THE NYSTAGMUS BLOCKAGE SYNDROME* BY Gunter K. von Noorden, MD CONGENITAL NYSTAGMUS WITH A NEUTRAL ZONE IN DEXTRO- OR LEVOVERSION IS A
well recognized entity; binocular functions are, as a rule, preserved and surgical treatment has been successful. 1'2 A less well-known, but at least as frequently encountered form of congenital nystagmus may be accompanied by esotropia. In these patients the nystagmus is reduced or absent when the fixating eye is adducted and becomes manifest and increasingly pronounced as the fixating eye moves toward the primary position and into abduction. In the older literature, nystagmus with a neutral zone in adduction and accompanied by esotropia is mentioned occasionally. 3'4 More recently, Franceschetti and co-workers5 concluded from an electronystagmographic study that patients who habitually hold their dominant eye in the position of least nystagmus (usually adduction) may develop suppression and esotropia in the fellow eye. Adelstein and Cuppers6 analyzed this condition further and coined the term "nystagmus blockage syndrome" (NBS) for an entity consisting of the following clinical features: esotropia with a sudden onset in early infancy and often preceded by nystagmus, pseudoabducens paralysis, and the appearance of a manifest nystagmus as the fixating eye moves from adduction towards abduction. In the majority of patients both eyes are in a convergent position, in others there is alternating fixation. Adelstein and Cuppers6 separated this syndrome from bilateral abducens paralysis and explained the esotropia on the basis of hypertonicity of the medial rectus muscles, resulting from the patient's sustained effort to block the nystagmus by adducting his eyes. Since this first report by Adelstein and Cuppers in 1966, the NBS has become widely recognized by European ophthalmologists, but has been mentioned only once in the American literature.7 I have diagnosed this syndrome in 12 of 247 consecutive patients with congenital esotropia. It is the purpose of this paper to describe the clinical findings in this group of *From the Department of Ophthalmology, Baylor College of Medicine, Houston, Texas. Supported in part by Research Grant EY 01120-03 from the National Eye Institute, National Institutes of Health, Department of Health, Education, and Welfare.
TR. AM. OPHTH. Soc., vol. LXXIV, 1976
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Noorden patients, to discuss the diagnostic and theoretical aspects of this intriguing entity, and to differentiate it from other causes of apparent abducens paralysis in esotropic children.
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CLINICAL DESCRIPTION
The clinical data are summarized in the Table. Six patients were males and six were females. The ages of the patients when first examined by this author ranged from 6 months to 11 years, the average age was 4 years. The family history for nystagmus was negative in all patients and esotropia occurred in the families of two patients of this group. All patients had a history of sudden onset of esotropia shortly after birth. The parents were unaware of nystagmus or head nodding prior to the onset of esotropia. A head turn developed within the first few months of life in all but four patients. The direction ofthe head turn was constant in some patients and varied in others. When the head was passively straightened in patients with a habitual head turn, both eyes were in an adducted position (Fig. 1). However, a head turn occurred in all patients upon covering one eye; the head turned towards the side of the fixating eye. Latent nystagmus with the smallest amplitude in adduction was present in cases 4, 6, 8, and 11 and a manifest nystagmus developed in all patients as soon as the fixating adducted eye began to move towards the primary position. Amblyopia was present in 6 patients (Cases 1, 2, 4, 5, 6, and 9). On superficial examination a marked limitation of abduction was present in all patients, and both eyes remained adducted when a visual target was moved horizontally back and forth before the patient's face. However, when the ductions were examined while the fellow eye was occluded, full abduction was noted in all but four patients (Cases 1, 5, 9, and 10). In these, each eye abducted well beyond the primary position but there was limitation ofabduction in extreme lateral gaze. With the exception ofcases 4 and 11, surgery had been performed. A significant overcorrection was present in 2 of 10 patients following surgery (Cases 9 and 10). It is perhaps significant that there was evidence of brain damage in both of these children. Case 9 had been esotropic from birth and developed a streptococcal meningitis at age two, followed by aqueductal stenosis which had to be relieved with a peritoneal shunt. The child is hyperactive, destructive, and has a short attention span. Case 10 had a shunt operation for hydrocephalus and repair of a spina bifida during infancy. This patient shows signs of moderately severe physical and mental retardation. A dissociated vertical deviation (alternating sursumduction) was present in four patients (Cases 1, 6, 11, and 12). In order to demonstrate the characteristic features of a NBS, one patient (Case 5) will be described in detail:
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FIGURE 1
A patient with the NBS may present with both eyes maximally adducted (Case 4), simulating bilateral abducens paralysis.
CASE REPORT
This one-year-old caucasian male infant presented on March 11, 1975, with a history of the left eye turning in since shortly after birth. At age four months, the mother had noted a head turn to the right which had become increasingly more severe in recent months. The child had been seen by several ophthalmologists but no previous treatment had been carried out. The medical history was unremarkable, the child was a product of an uncomplicated pregnancy, and his birth weight was 6 pounds 9 ounces. The mother has an anisometropic amblyopia and one maternal cousin had esotropia. On examination the child had a marked head turn to the right (Figure 2A) and fixated with the right eye. On straightening the head passively, both eyes were in a position of adduction and an esotropia of approximately 70 prism diopters was present at near and distance fixation (Figure 2B). Upon covering the left eye, the child maintained steady fixation with the right eye and the head turn increased slightly (Figure 2C). Upon covering the right eye, the child turned his head to the left but objected to prolonged occlusion (Figure 2D). No nystagmus was present with either eye in adduction but a jerky nystagmus with a fast phase to the left occurred in both eyes as soon as the left eye followed a fixation target into the left field of gaze (Figure 3A) and, with a fast phase to the right, when the right eye followed
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FIGURE 2
Case 5 presented with a head turn to the right and preferred OD for fixation (A). On passive straightening of the head both eyes were in adduction (B). Occlusion OS slightly increased habitual head turn to the right (C). Upon occluding OD the head is turned to the left (D).
the light into the right field of gaze (Figure 3B). The amplitude of nystagmus increased the further each eye abducted and, unlike an end point nystagmus in extreme lateral gaze, the nystagmus became apparent as soon as each eye left the position of adduction and moved towards primary position. Except for a slight limitation of abduction of each eye, ductions and versions were unremarkable. An atropine refraction showed the following refractive error: 0. D.: +2.25 sph. + 1.00 cyl. axis 90 and O.S.: +2.75 sph. The right eye fixated centrally and steadily and there was wandering fixation of the left eye. The fundi and the results of the remainder of the ocular examination were normal. After one week of occlusion of the right eye, the head turn to the left persisted but the child now held fixation steadily with the left adducted eye and no longer
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Manifest jerky nystagmus as fixating OS moves into abduction (A) or fixating OD moves into abduction (B). Note slight limitation of abduction OU that was present in Cases 1, 5, 9, and 10.
objected to having the right eye covered. However, there was still marked preference for fixation of the right eye and the head, turn to the right recurred as soon as the patch was removed from the left eye. The diagnosis of congenital esotropia with nystagmus blockage was made. On April 7, 1975, the left medial rectus muscle was recessed 5 mm and the left lateral rectus muscle was resected 8 mm. The forced duction test, performed under general anesthesia prior to the operation, was negative. Two weeks later, the esotropia measured 35 prism diopters. There was still preference of fixation with the right eye. However, the spontaneous head turn to the right had disappeared and the head remained also straight when each eye was covered. There was no nystagmus with either eye in adduction or primary position but the nystagmus was still present as soon as each eye moved from primary position towards abduction. Obviously, the neutral zone had been shifted from adduction into primary position by surgical intervention. On May 21, 1975, the patient had a 5 mm recession of the right medial and a 7 mm resection of the right lateral rectus muscle for his residual esotropia. Seven months later, the child was orthophoric at near and distance fixation. The head had remained straight and fixation was maintained steadily with each eye in primary position while the other eye was covered. Abduction of either eye was normal and a low-amplitude high-frequency jerky nystagmus was noted only on extreme
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lateral gaze to either side. This type of nystagmus had now become indistinguishable from an end point nystagmus. DISCUSSION
The diagnosis ofthe NBS was made in 12 (4.8%) of 247 consecutive patients with congenital esotropia. This incidence is lower than that reported by Ciippers8 who recognized the NBS in 139 (10.3%) of 1,352 esotropic patients. It has been pointed out that the nystagmus may be of such small amplitude that it can be detected only with slit lamp or visuscope examination. 8.9 It is possible that NBS would have been recognized more frequently in our patients if slit lamp and visuscope examination had been a routine part of the examination of esotropic infants. On the other hand, one must consider the possibility that many patients classified elsewhere as having the NBS may have had, in fact, crossed fixation, a clinically similar but pathophysiologically different form of pseudoabducens paralysis. Curiously, crossed fixation is not mentioned in any of the publications concerned with descriptions of the NBS68-10 and the differental diagnosis between these two conditions needs clarification. Crossed fixation is frequently encountered in congenital esotropes with alternating fixation behavior. Characteristically, and as in the NBS, there is apparent paralysis of abduction on lateral gaze which disappears, however, as soon as one eye is occluded or during the doll's head maneuver. This apparent weakness of abduction is caused by a switch of fixation from one eye to the other as the patient fixates a visual target moving horizontally before his eyes. In the right field of gaze, he uses his left eye and in the left field of gaze, his right eye. The nonfixating eye remains adducted (Figure 4). There are three features that distinguish crossed fixation from the NBS. First, and most importantly, there is no nystagmus as fixation is maintained in the primary position or in abduction. Second, an esotropia caused by adduction of both eyes, which is frequently seen with the NBS, does not occur in alternating esotropia with crossed fixation where the fixating eye, as a rule, is in the primary position and only the nonfixating eye is adducted. Third, patients with crossed fixation are alternators; amblyopia does not occur with alternating strabismus but is seen with the NBS. The second condition to be differentiated from the.NBS is a bilateral congenital abducens paralysis. In both instances abduction is limited and a head turn occurs either spontaneously or upon covering one eye. According to Adelstein and Cuppers6 this differentiation is based on an examination under general anesthesia: spontaneous abduction during the in-
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A
B
FIGURE 4
Crossed fixation with pseudoabducens paralysis. In the right field of gaze the patient fixates with OS (A); in the left field of gaze with OD (B).
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duction or recovery stage and a divergent position of the globes during surgical levels of anesthesia are indicative of nystagmus blockage. Immediately prior to awakening from anesthesia a nystagmus has been reported6 to appear which, within a matter of seconds, is blocked by adduction of the globes. However, Adelstein and Cuppers point out that in patients with NBS of long standing, contracture of the medial rectus muscles and loss of elasticity of conjunctiva and Tenon's capsule will limit abduction even under general anesthesia; the forced duction test will then become positive and the NBS can no longer be differentiated from a primary abducens paralysis. I have not encountered this differential diagnostic problem in this series; even though abduction was limited in 4 of the 12 patients, their eyes moved well beyond the primary position toward abduction, and the forced duction tests were negative in all patients who underwent surgery. The mechanism of nystagmus blockage and the etiology of the accompanying esotropia deserve further discussion. It is well known that visual acuity in congenital nystagmus is often better at near fixation than at distant fixation because of the dampening effect of convergence on the amplitude of the nystagmus. The findings in Case 6 demonstrate that the position of the eyes can be related to variations of visual acuity in different directions of gaze. In this patient, visual acuity of each eye improved in that position of gaze where nystagmus was least pronounced or absent. The patient had a head turn to the right and showed preference in fixation with the right eye. Visual acuity of the adducted right eye was 20/30 and decreased to 20/60 in abduction. Visual acuity of the adducted left eye was 20/60 and decreased to 20/200 in abduction. Whereas there was no nystagmus when the patient fixated with the adducted right eye, a latent nystagmus of low amplitude occurred when the left adducted eye took up fixation. The amplitude of the nystagmus increased as the left eye abducted. Similar observations have been reported by Haase.9
The question arises whether a patient uses convergence or adduction innervation to gain better visual acuity. Adelstein and Cuppers6 state that it is probably adduction rather than convergence that causes blockage of the nystagmus since "accommodation is uninvolved in adduction". On the other hand, the following observation of the pupil size during episodes of intermittent esotropia in a patient with congenital nystagmus implicates the convergence-accommodation mechanism. Because of the atypical features, this patient was not included in our series.
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A 5-year-old caucasian boy was noted to have manifest nystagmus and a head turn to the right since early infancy. Visual acuity determined with both eyes open and in levoversion was 20/60 and decreased to 20/200 in dextroversion. The nystagmus decreased in levoversion and increased in dextroversion. There was no manifest ocular deviation in any gaze position. However, when the examiner's hand forced the patient's head into primary position and the child was asked to read an acuity chart at 20 feet or at 1 foot distance, an esotropia varying between 10 and 30 prism diopters occurred. As the esotropia appeared the nystagmus vanished completely and both pupils constricted from 5 to 2 mm. The esotropia disappeared, the pupils dilated to their normal size, and the nystagmus recurred as soon as the patient released his attention. The diagnosis of asymmetric concordant nystagmus with a null point in levoversion and blockage by convergence in the primary position was made. A modified Kestenbaum-Anderson operation" consisting of a 7 mm recession of the left lateral rectus, a 6 mm resection of the left medial rectus, an 8 mm resection of the right lateral rectus, and a 5 mm recession of the right medial rectus muscle eliminated the head turn. Even though the operation succeeded in shifting the position of least nystagmus from levoversion into primary position, there was still intermittent esotropia with pupillary constriction as soon as the patient made a sustained effort to fixate visual objects in the distance or at near. In further support of the concept that nystagmus is blocked by convergence is an observation by Haase,9 who demonstrated electromyographically in patients with the NBS that there is incomplete inhibition of the medial rectus muscle of the nonfixating eye as the fixating eye moves from abduction into adduction. During a conjugate eye movement, one would expect complete inhibition of the medial rectus muscle in the nonfixating eye under such circumstances. On the other hand, convergence innervation, causing increased tonus of both medial rectus muscles, would explain these findings. Further clinical research is needed to determine the roles of accommodative, voluntary, or tonic convergence during blockage of the nystagmus. However, it is reasonable to conclude that the esotropia develops as a consequence of sustained convergence effort. Another interesting clinical feature of the NBS is that it may explain the recurrence of esotropia after multiple operations. This is demonstrated by the findings in Case 12 of this series. A 4-year-old caucasian girl had a large angle esotropia since birth. Four operations had been performed in the following order: 5 mm recession of the right medial and 8 mm resection ofthe right lateral rectus muscle; 5 mm
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recession ofthe left medial and 8 mm resection ofthe left lateral rectus muscle; marginal myotomies of both medial rectus muscles; advancement and additional resection of both lateral rectus muscles. After each operation the angle of strabismus was significantly reduced or the eyes were aligned for short periods of time. This was followed by a rather rapid recurrence of the esotropia. Ductions, versions, and saccadic velocities were remarkably normal and scarring of the conjunctiva was minimal, considering the number of operations performed. There was no obvious mechanical obstacle to nQrmal ocular motility. A jerky manifest nystagmus of both eyes appeared as each eye fixated in a position of abduction; nystagmus was absent in adduction. Upon occluding the left eye, the patient turned her head to the right, thus placing the right, dominant eye into a position of adduction. Surgical failures of this nature can often be explained on the basis of mechanical factors such as scarring, adhesions, disinserted muscles, etc. However, in the absence of such problems, innervational causes must be considered. Continued blockage of the nystagmus by sustained convergence is certainly a more plausible explanation for the persistence of esotropia after surgery than the widely held view that anomalous retinal correspondence causes the eyes to return to their preoperative position. Anomalies of the head posture are frequently encountered with the NBS. If the patient chooses adduction as the position of optimal visual acuity for his dominant eye, the head turn occurs toward the side of the dominant eye; the contralateral eye may become amblyopic (Cases 4, 5, and 6). If there is no strong ocular dominance, or if the amblyopia has been cured by occlusion therapy, the patient will alternate and the head turn may vary according to which eye is used for fixation at any given moment. This pattern was present in cases 3, 7, and 8. If there is rapid alternation of fixation there will be an equally rapid change of the head turn from one to the other side and the esotropic patients with congenital nystagmus described by Robb12 as having "periodic alternation of the null point" may well fall into this category. For the treatment of the NBS in infants, Cuppers8 recommends alternating occlusion combined with "exercises of ocular motility". He claims that this therapy eliminates the blockage mechanism in the large majority of patients. Surgical treatment, consisting of a recession-resection operation is advocated by Cuppers only when the forced duction test performed under general anesthesia becomes positive and progressive contracture of the medial rectus muscle and loss of elasticity of conjunctiva in Tenon's capsule are about to develop. More recently, a posterior fixation
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suture (Fadenoperation) has been successfully employed at the Giessen University Eye Clinic for the treatment of the NBS.10 Conservative therapy consisting of alternating occlusion for a period of up to six weeks was attempted in several of our patients. However, a marked head turn persisted or developed where it had not been present prior to therapy, and we proceeded with surgery in these and in the remainder of our patients who had no other preceding therapy. Except for the surgical overcorrection encountered in cases 9 and 10 and the persistent esotropia in case 12, the results of surgery with a conventional recession-resection procedure on one or both eyes have been gratifying. SUMMARY
A previously unrecognized form of nystagmus associated with esotropia was described in the German literature by Adelstein and Cuppers in 1966 as the nystagmus blockage syndrome. Even though widely publicized in the European ophthalmic literature, this entity has remained virtually unrecognized in this country. We have identified the nystagmus blockage syndrome in 12 of 247 consecutive patients with congenital esotropia. The following characteristic features were encountered: onset of esotropia in early infancy, pseudoabducens paralysis, head turn toward the side of the fixating eye, absence of nystagmus with the fixating eye in adduction, and appearance of a manifest jerky nystagmus as the fixating eye moves into primary position and abduction. It has been suggested that the nystagmus is actively blocked by convergence innervation, the esotropia thus being caused by sustained convergence and secondary changes in the medial rectus muscles. The differential diagnosis includes crossed fixation and bilateral sixth nerve paralysis. ACKNOWLEDGEMENT
I thank Dr Samuel Shoss for his permission to include Case 12 in this paper. REFERENCES
1. Kestenbaum A: Nouvelle operation du nystagmus. Bull Soc Ophtalmol Fr 6:599, 1953. 2. Anderson JR: Causes and treatment of congenital eccentric nystagmus. Br J Ophthalmol 137:267, 1953. 3. Lafon C: La vision des nystagmiques. Ann Ocul (Paris) 151:4, 1914. 4. Ohm J: Das Ohrlabyrinth als Erzeuger des Schielens. Zeitschr Augenheilkd 36:253, 1916.
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5. Franceschetti A, Monnier M, Dieterle P: Analyse du nystagmus congenital par la methode 'electro-nystagmographique (ENG). Bull Schweiz Akad Med Wiss 8:403, 1952. 6. Adelstein F, Cuppers C: Zum Problem der echten und scheinbaren Abducenslamung (das sogenannte "Blockierungs-syndrom"). In AugenmuskeUahmungen, Buch. d. Augenarzt. Stuttgart, F. Enke, 46:271, 1966. 7. Burian HM, von Noorden GK: Binocular Vision and Ocular Motility. Theory and management of strabismus. St. Louis, C.V. Mosby, 1974, p 404. 8. Cuppers C: Probleme der operativen Therapie des okularen Nystagmus. Klin Monatsbl Augenheilkd 159:145, 1971. 9. Haase W: Zur Diagnose und Therapie des Nystagmusblockierungssyndroms (elektromyographische Untersuchungen). Klin Monatsbl Augenheilkd 157:500, 1970. 10. Muhlendyck H, Linnen HJ: Die operative Behandlung nystagmusbedingter schwankender Schielwinkel mit der Fadenoperation nach Cuppers. Klin Monatsbl Augenheilkd 167:273, 1975. 11. Parks MM: Congenital nystagmus surgery. Am Orthop J 23:35, 1973. 12. Robb RM: Periodic alternation of null point in congenital nystagmus. Association with alternating gaze deviation and esotropia. Arch Ophthalmol 87:169, 1972.
DISCUSSION
DR ARTHUR JAMPOLSKY. Officers, members, and guests. I want to thank the author for sending his manuscript to me in advance of this meeting. He is to be congratulated for examining the complex group of infantile esotropes and isolating a category requiring separate diagnostic techniques and perhaps separate treatment techniques. It is only by this method of separating uniquely characteristic cases, from a general mix of congenital or infantile esotropias, that we will begin to make sense regarding treatment. What is the uniquely descriptive distinguishing feature in these cases? I feel that it is as follows: "An esotropia (usually binocular, but may be monocular) in which there is marked preference for fixation in adduction, with nystagmus increasing toward abduction, with or without a real limitation of abduction. " The most interesting cases are those without any demonstrable limitation of abduction but without any real ability to maintain steady fixation in abduction, nor in fact in the primary position. Characteristically, there is a head turn, to fix with each eye in extreme adduction, where the nystagmus is minimal or absent. This was well described by Kestenbaum as unimacular nystagmus. He stated, "As is always the case, the right nystagmus became more severe engaged to the right, and less severe engaged to the left, i. e., in adduction of the right eye. The patient achieved this adduction by rotating his head to the right, and fixating with his now adducted right eye. The opposite happened when the left eye tried to fixate: head rotation to the left, fixation with the left, now adducted eye." The Dutch school (Keiner, Zeeman, and Crone) have repeatedly emphasized the abnormalities of the monocular reflexes, rather than the binocular reflexes so traditionally popular. This is entirely consistent with the term "unimacular" and consistent with my own views that there is an abnormality of the motor systems, as reflected in the monocular fixation and saccadic and pursuit mechanisms, as the common etiological basis for many of the phenomena seen in the group of infantile esotropes under discussion.
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A. Ciancia further analyzed such patients and well described the adduction fixation preference, with increased nystagmus toward abduction, and later added some electrooculographic recordings of the nystagmus in such patients. Different authors have put forth different causation theories of this entity. The author points out that Cuppers and Adelstein in 1966 proposed a mechanism of "blocked nystagmus", and the author has proposed his own notion of the mechanism of the blocked nystagmus by sustained convergence. My own interest in such cases was sparked by Ciancia's description of the entity and his electrooculographic studies. In 1974 at the September meeting of the Pacific Section of the Association for Research in Vision and Ophthalmology, held in San Francisco, I showed some electrooculograms that analyzed the abduction nystagmus with a view toward providing evidence that the defect was in the "hold" mechanism, i. e., the second part of the saccadic system. Others showed some brief fixation hold in extreme abduction, but apparently were driven off by an unharnessed pursuit system. Since that time we have recorded electrooculograms showing that there is a true neutral point of nystagmus in extreme adduction, in some patients, with the fast component toward adduction, when one records the eye movements in the very extreme few degrees offurther adduction. It is obvious that there are many mixed patterns of motor system defects in this group of patients depicting adduction fixation preference. My own theory is that this is a defect of one of the motor systems, a neural deficit. We are all familiar with the immature development of the input system, i. e., the underdeveloped macula at birth. Sufficient attention has not been directed toward the possible immaturity and maldeveloped motor systems in developmental esotropia. Cogan has described similar fixation-hold defects in the extreme fields of gaze, as occurring in rehabilitated saccades. It is also found in several cerebellectomized monkeys. I believe there to be a distinct relationship among the following cases, all exhibiting adduction fixation preference with increasing nystagmus toward abduction: 1) Alternating infantile esotropia, with each eye preferring adduction fixation, and compensatory head turn; 2) unilateral strabismus (relative amblyopia of the non-fixing eye), with either esotropia or exotropia; and 3) neutral point of nystagmus, wherein the nonfixing eye is "orthotropic" without evident alignment. It matters now whether the nondominant eye is parallel (as in neutral or null point nystagmus) or an amblyopic esotropic eye or an equal visioned alternating eye (wherein the mechanism exists in each eye). The fixing eye's dominant role in preferring extreme adduction fixation is of paramount importance. Many authors have advocated a large recession ofthe medial rectus in order to stabilize fixation in the primary position. This has ranged from 7 to 9 mm, and my recent experience during the past year has indicated the desirability of this procedure in selected instances. Certainly the medial rectus must be recessed a considerable degree if there is to be a tonus balance reestablished. I would like to ask the author two questions: 1) Why the difference of 44% incidence of Ciancia's cases of esotropes with this characteristic, without restriction
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in abduction and 2) his comments relative to my own proposed causation theory of a neurologic deficit of one of the motor control systems. I want to congratulate the author for again calling attention to the differential diagnosis of the mixed group of infantile esotropes, which highlights the point that there is no single etiologic cause and certainly no single surgical treatment in the management of infantile esotropia. DR PHILIP KNAPP. I would like to congratulate Doctor von Noorden for bringing this syndrome to our attention. As he stated, for the last ten years in Europe this has been an important subject. When Doctor DeDecker was here last summer for the International Orthoptic Congress, he had already done 2,000 of these Faden operations. Muhlendyck, in the paper that Doctor von Noorden referred to, stressed two facts that I think are important. I don't think Doctor von Noorden gave these quite enough emphasis. One is if you take these children and just have them follow a light, quite frequently they will end up with both eyes maximally adducted looking almost like strabismus fixus. If you then cover one eye and make the child look with the other eye, the nystagmus increases as the eye abducts, finally fully, and the angle of esotropia decreases. This is against the diagnosis of a VI nerve paresis. As you know, with a VI nerve paresis the esotropia gets worse when you get into the field of action of the lateral rectus so this makes your differential diagnosis for you. The surgeon is faced with a child who varies between 150 and 30 diopters of esotropia. Both eyes go in dramatically. Then at times the eyes are practically parallel which is why this Faden or posterior suture technique was devised. I have done 46 Faden operations upon 31 patients in the last five months. I've done three of them for this so-called nystagmus blockage syndrome and the results have been rewarding. The principle used is that you do a mild recession for the static angle of esotropia then you use this suture which should be 13 mm posterior to the insertion of the medial rectus-not 10 mm. Cuppers originally said 10 mm but he changed it in 1974. So far, two of the three patients have been practically cured and the other is greatly improved. Obviously the follow-up is very inadequate, being only a few months. DR KENNETH SWAN. We are indebted to Doctor von Noorden for calling the attention of American ophthalmologists to this group of patients. Since reading about it in the European literature, Andrea Tongue and I have been reviewing patients in the Oregon Children's Eye Clinic and have identified a number with this clinical entity. One is worth discussing, because I have followed her course and taken photos for 27 years. [Slide] This girl was referred to me when she was just a few months old with a differential diagnosis of bilateral VIth paralysis or strabismus fixus, but those conditions were excluded. A few months later the parents noted that whenever the infant looked at anything intently she would turn her face to the right [Slide]. They interpreted this as a crossing of the right eye, but indeed the child was fixating with the right eye at the null point of nystagmus. When forced to abduct either eye to the midline, gross nystagmus would develop. We were con-
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servative in her surgical management for several reasons. One was that when this child was drowsy or partially awake, her eyes would straighten. The next slide, taken in 1951 when the child was two years old, again shows her face turned to keep the fixating right eye in adduction. We had the dual problem of shifting the null point of the nystagmus in each eye to a more central position and at the same time reducing the esotropia. Bilateral medial rectus recessions were pefformed in 1952. The operative note described that her eyes straightened under anesthesia and forced ductions revealed no limitation, features described for this entity in the European literature. The next slide shows that in 1956, at age 7, her eyes were in good alignment. She had no face turn and nystagmus only with abduction. At age 14 she began to show a left hypertropia. I recessed her left inferior oblique at age 17. One year later photo shows that the hyper was corrected. The final slide, taken the first week in May of 1976, reveals no deviation. She was asymptomatic; however, her visual acuity was 20/25 maximal. The visuscope revealed a fine searching nystagmus in the central field. With abduction of 25 degrees or more ofeither eye, she still developed a gross nystagmus. Unfortunately, the bridge of her nose was so high that I was unable to determine whether fixating with her left eye in right gaze would eliminate this nystagmus. This patient's course illustrated that early surgery to shift the null point of the nystagmus and to reduce the nystagmus and to reduce the esotropia was effective for this condition. Her condition was markedly improved and has been stable for more than 25 years. Thank you. DR GUNTER VON NOORDEN. I would like to thank the discussors for their very pertinent comments. I do not know the reason for the difference in the incidence of the nystagmus blockage syndrome in Ciancia's and my series. I am doubtful, however, whether the nystagmus in esotropes described by Ciancia qualifies for inclusion under this diagnosis according to the criteria set forth by Adelstein and Cuppers and in this paper. I agree with Dr Jampolsky that the nystagmus in these patients is of the motor defect type, as defined by Cogan. The esotropia develops secondarily and as the result of an effort to neutralize the nystagmus. I also share Dr Jampolsky's concern with respect to the need for further study ofthis intriguing entity by electrooculography and electromyography. I am sure that much can be learned from this ap-
proach. I was very interested to hear Dr Knapp has already had much experience in the treatment of this condition with the new strabismus operation, introduced by Cuppers as the "Fadenoperation." I too have been experimenting with this procedure and believe that it may evolve as a major advance in the surgical treatment of certain forms of strabismus. The essence of this procedure is to alter the effectiveness of an extraocular muscle in one position of gaze without affecting it in others and without changing the tonus of its antagonist. Thus, it is especially applicable as an operation to weaken adduction in patients with a large dynamic angle of esotropia, the size of which depends on the state of attention as in the nystagmus blockage syndrome. However, the German term "Fadenoperation" is rather
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meaningless and has been used by earlier authors to describe what we call traction sutures. It would be more appropriate to replace it in English with "posterior fixation" or "retropexy" of an extraocular muscle. Dr Swan points out that in patients with the nystagmus blockage syndrome, the eyes may straighten under general anesthesia. Adelstein and Cuppers make a strong point of this. I doubt that this phenomenon is really pathognomonic for the nystagmus blockage syndrome since straightening ofthe eyes or even exotropia under general anesthesia is not an uncommon occurrence in esotropes and not restricted to patients with the nystagmus blockage syndrome. I was most interested to hear the detailed description of Dr Swan's case which adds yet another one to the increasing number of patients with the nystagmus blockage syndrome that we have now learned to recognize. Again, I wish to thank all the discussors for their helpful and constructive comments.
well recognized entity; binocular functions are, as a rule, preserved and surgical treatment has been successful. 1'2 A less well-known, but at least as frequently encountered form of congenital nystagmus may be accompanied by esotropia. In these patients the nystagmus is reduced or absent when the fixating eye is adducted and becomes manifest and increasingly pronounced as the fixating eye moves toward the primary position and into abduction. In the older literature, nystagmus with a neutral zone in adduction and accompanied by esotropia is mentioned occasionally. 3'4 More recently, Franceschetti and co-workers5 concluded from an electronystagmographic study that patients who habitually hold their dominant eye in the position of least nystagmus (usually adduction) may develop suppression and esotropia in the fellow eye. Adelstein and Cuppers6 analyzed this condition further and coined the term "nystagmus blockage syndrome" (NBS) for an entity consisting of the following clinical features: esotropia with a sudden onset in early infancy and often preceded by nystagmus, pseudoabducens paralysis, and the appearance of a manifest nystagmus as the fixating eye moves from adduction towards abduction. In the majority of patients both eyes are in a convergent position, in others there is alternating fixation. Adelstein and Cuppers6 separated this syndrome from bilateral abducens paralysis and explained the esotropia on the basis of hypertonicity of the medial rectus muscles, resulting from the patient's sustained effort to block the nystagmus by adducting his eyes. Since this first report by Adelstein and Cuppers in 1966, the NBS has become widely recognized by European ophthalmologists, but has been mentioned only once in the American literature.7 I have diagnosed this syndrome in 12 of 247 consecutive patients with congenital esotropia. It is the purpose of this paper to describe the clinical findings in this group of *From the Department of Ophthalmology, Baylor College of Medicine, Houston, Texas. Supported in part by Research Grant EY 01120-03 from the National Eye Institute, National Institutes of Health, Department of Health, Education, and Welfare.
TR. AM. OPHTH. Soc., vol. LXXIV, 1976
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Noorden patients, to discuss the diagnostic and theoretical aspects of this intriguing entity, and to differentiate it from other causes of apparent abducens paralysis in esotropic children.
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CLINICAL DESCRIPTION
The clinical data are summarized in the Table. Six patients were males and six were females. The ages of the patients when first examined by this author ranged from 6 months to 11 years, the average age was 4 years. The family history for nystagmus was negative in all patients and esotropia occurred in the families of two patients of this group. All patients had a history of sudden onset of esotropia shortly after birth. The parents were unaware of nystagmus or head nodding prior to the onset of esotropia. A head turn developed within the first few months of life in all but four patients. The direction ofthe head turn was constant in some patients and varied in others. When the head was passively straightened in patients with a habitual head turn, both eyes were in an adducted position (Fig. 1). However, a head turn occurred in all patients upon covering one eye; the head turned towards the side of the fixating eye. Latent nystagmus with the smallest amplitude in adduction was present in cases 4, 6, 8, and 11 and a manifest nystagmus developed in all patients as soon as the fixating adducted eye began to move towards the primary position. Amblyopia was present in 6 patients (Cases 1, 2, 4, 5, 6, and 9). On superficial examination a marked limitation of abduction was present in all patients, and both eyes remained adducted when a visual target was moved horizontally back and forth before the patient's face. However, when the ductions were examined while the fellow eye was occluded, full abduction was noted in all but four patients (Cases 1, 5, 9, and 10). In these, each eye abducted well beyond the primary position but there was limitation ofabduction in extreme lateral gaze. With the exception ofcases 4 and 11, surgery had been performed. A significant overcorrection was present in 2 of 10 patients following surgery (Cases 9 and 10). It is perhaps significant that there was evidence of brain damage in both of these children. Case 9 had been esotropic from birth and developed a streptococcal meningitis at age two, followed by aqueductal stenosis which had to be relieved with a peritoneal shunt. The child is hyperactive, destructive, and has a short attention span. Case 10 had a shunt operation for hydrocephalus and repair of a spina bifida during infancy. This patient shows signs of moderately severe physical and mental retardation. A dissociated vertical deviation (alternating sursumduction) was present in four patients (Cases 1, 6, 11, and 12). In order to demonstrate the characteristic features of a NBS, one patient (Case 5) will be described in detail:
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FIGURE 1
A patient with the NBS may present with both eyes maximally adducted (Case 4), simulating bilateral abducens paralysis.
CASE REPORT
This one-year-old caucasian male infant presented on March 11, 1975, with a history of the left eye turning in since shortly after birth. At age four months, the mother had noted a head turn to the right which had become increasingly more severe in recent months. The child had been seen by several ophthalmologists but no previous treatment had been carried out. The medical history was unremarkable, the child was a product of an uncomplicated pregnancy, and his birth weight was 6 pounds 9 ounces. The mother has an anisometropic amblyopia and one maternal cousin had esotropia. On examination the child had a marked head turn to the right (Figure 2A) and fixated with the right eye. On straightening the head passively, both eyes were in a position of adduction and an esotropia of approximately 70 prism diopters was present at near and distance fixation (Figure 2B). Upon covering the left eye, the child maintained steady fixation with the right eye and the head turn increased slightly (Figure 2C). Upon covering the right eye, the child turned his head to the left but objected to prolonged occlusion (Figure 2D). No nystagmus was present with either eye in adduction but a jerky nystagmus with a fast phase to the left occurred in both eyes as soon as the left eye followed a fixation target into the left field of gaze (Figure 3A) and, with a fast phase to the right, when the right eye followed
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FIGURE 2
Case 5 presented with a head turn to the right and preferred OD for fixation (A). On passive straightening of the head both eyes were in adduction (B). Occlusion OS slightly increased habitual head turn to the right (C). Upon occluding OD the head is turned to the left (D).
the light into the right field of gaze (Figure 3B). The amplitude of nystagmus increased the further each eye abducted and, unlike an end point nystagmus in extreme lateral gaze, the nystagmus became apparent as soon as each eye left the position of adduction and moved towards primary position. Except for a slight limitation of abduction of each eye, ductions and versions were unremarkable. An atropine refraction showed the following refractive error: 0. D.: +2.25 sph. + 1.00 cyl. axis 90 and O.S.: +2.75 sph. The right eye fixated centrally and steadily and there was wandering fixation of the left eye. The fundi and the results of the remainder of the ocular examination were normal. After one week of occlusion of the right eye, the head turn to the left persisted but the child now held fixation steadily with the left adducted eye and no longer
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Manifest jerky nystagmus as fixating OS moves into abduction (A) or fixating OD moves into abduction (B). Note slight limitation of abduction OU that was present in Cases 1, 5, 9, and 10.
objected to having the right eye covered. However, there was still marked preference for fixation of the right eye and the head, turn to the right recurred as soon as the patch was removed from the left eye. The diagnosis of congenital esotropia with nystagmus blockage was made. On April 7, 1975, the left medial rectus muscle was recessed 5 mm and the left lateral rectus muscle was resected 8 mm. The forced duction test, performed under general anesthesia prior to the operation, was negative. Two weeks later, the esotropia measured 35 prism diopters. There was still preference of fixation with the right eye. However, the spontaneous head turn to the right had disappeared and the head remained also straight when each eye was covered. There was no nystagmus with either eye in adduction or primary position but the nystagmus was still present as soon as each eye moved from primary position towards abduction. Obviously, the neutral zone had been shifted from adduction into primary position by surgical intervention. On May 21, 1975, the patient had a 5 mm recession of the right medial and a 7 mm resection of the right lateral rectus muscle for his residual esotropia. Seven months later, the child was orthophoric at near and distance fixation. The head had remained straight and fixation was maintained steadily with each eye in primary position while the other eye was covered. Abduction of either eye was normal and a low-amplitude high-frequency jerky nystagmus was noted only on extreme
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lateral gaze to either side. This type of nystagmus had now become indistinguishable from an end point nystagmus. DISCUSSION
The diagnosis ofthe NBS was made in 12 (4.8%) of 247 consecutive patients with congenital esotropia. This incidence is lower than that reported by Ciippers8 who recognized the NBS in 139 (10.3%) of 1,352 esotropic patients. It has been pointed out that the nystagmus may be of such small amplitude that it can be detected only with slit lamp or visuscope examination. 8.9 It is possible that NBS would have been recognized more frequently in our patients if slit lamp and visuscope examination had been a routine part of the examination of esotropic infants. On the other hand, one must consider the possibility that many patients classified elsewhere as having the NBS may have had, in fact, crossed fixation, a clinically similar but pathophysiologically different form of pseudoabducens paralysis. Curiously, crossed fixation is not mentioned in any of the publications concerned with descriptions of the NBS68-10 and the differental diagnosis between these two conditions needs clarification. Crossed fixation is frequently encountered in congenital esotropes with alternating fixation behavior. Characteristically, and as in the NBS, there is apparent paralysis of abduction on lateral gaze which disappears, however, as soon as one eye is occluded or during the doll's head maneuver. This apparent weakness of abduction is caused by a switch of fixation from one eye to the other as the patient fixates a visual target moving horizontally before his eyes. In the right field of gaze, he uses his left eye and in the left field of gaze, his right eye. The nonfixating eye remains adducted (Figure 4). There are three features that distinguish crossed fixation from the NBS. First, and most importantly, there is no nystagmus as fixation is maintained in the primary position or in abduction. Second, an esotropia caused by adduction of both eyes, which is frequently seen with the NBS, does not occur in alternating esotropia with crossed fixation where the fixating eye, as a rule, is in the primary position and only the nonfixating eye is adducted. Third, patients with crossed fixation are alternators; amblyopia does not occur with alternating strabismus but is seen with the NBS. The second condition to be differentiated from the.NBS is a bilateral congenital abducens paralysis. In both instances abduction is limited and a head turn occurs either spontaneously or upon covering one eye. According to Adelstein and Cuppers6 this differentiation is based on an examination under general anesthesia: spontaneous abduction during the in-
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A
B
FIGURE 4
Crossed fixation with pseudoabducens paralysis. In the right field of gaze the patient fixates with OS (A); in the left field of gaze with OD (B).
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duction or recovery stage and a divergent position of the globes during surgical levels of anesthesia are indicative of nystagmus blockage. Immediately prior to awakening from anesthesia a nystagmus has been reported6 to appear which, within a matter of seconds, is blocked by adduction of the globes. However, Adelstein and Cuppers point out that in patients with NBS of long standing, contracture of the medial rectus muscles and loss of elasticity of conjunctiva and Tenon's capsule will limit abduction even under general anesthesia; the forced duction test will then become positive and the NBS can no longer be differentiated from a primary abducens paralysis. I have not encountered this differential diagnostic problem in this series; even though abduction was limited in 4 of the 12 patients, their eyes moved well beyond the primary position toward abduction, and the forced duction tests were negative in all patients who underwent surgery. The mechanism of nystagmus blockage and the etiology of the accompanying esotropia deserve further discussion. It is well known that visual acuity in congenital nystagmus is often better at near fixation than at distant fixation because of the dampening effect of convergence on the amplitude of the nystagmus. The findings in Case 6 demonstrate that the position of the eyes can be related to variations of visual acuity in different directions of gaze. In this patient, visual acuity of each eye improved in that position of gaze where nystagmus was least pronounced or absent. The patient had a head turn to the right and showed preference in fixation with the right eye. Visual acuity of the adducted right eye was 20/30 and decreased to 20/60 in abduction. Visual acuity of the adducted left eye was 20/60 and decreased to 20/200 in abduction. Whereas there was no nystagmus when the patient fixated with the adducted right eye, a latent nystagmus of low amplitude occurred when the left adducted eye took up fixation. The amplitude of the nystagmus increased as the left eye abducted. Similar observations have been reported by Haase.9
The question arises whether a patient uses convergence or adduction innervation to gain better visual acuity. Adelstein and Cuppers6 state that it is probably adduction rather than convergence that causes blockage of the nystagmus since "accommodation is uninvolved in adduction". On the other hand, the following observation of the pupil size during episodes of intermittent esotropia in a patient with congenital nystagmus implicates the convergence-accommodation mechanism. Because of the atypical features, this patient was not included in our series.
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A 5-year-old caucasian boy was noted to have manifest nystagmus and a head turn to the right since early infancy. Visual acuity determined with both eyes open and in levoversion was 20/60 and decreased to 20/200 in dextroversion. The nystagmus decreased in levoversion and increased in dextroversion. There was no manifest ocular deviation in any gaze position. However, when the examiner's hand forced the patient's head into primary position and the child was asked to read an acuity chart at 20 feet or at 1 foot distance, an esotropia varying between 10 and 30 prism diopters occurred. As the esotropia appeared the nystagmus vanished completely and both pupils constricted from 5 to 2 mm. The esotropia disappeared, the pupils dilated to their normal size, and the nystagmus recurred as soon as the patient released his attention. The diagnosis of asymmetric concordant nystagmus with a null point in levoversion and blockage by convergence in the primary position was made. A modified Kestenbaum-Anderson operation" consisting of a 7 mm recession of the left lateral rectus, a 6 mm resection of the left medial rectus, an 8 mm resection of the right lateral rectus, and a 5 mm recession of the right medial rectus muscle eliminated the head turn. Even though the operation succeeded in shifting the position of least nystagmus from levoversion into primary position, there was still intermittent esotropia with pupillary constriction as soon as the patient made a sustained effort to fixate visual objects in the distance or at near. In further support of the concept that nystagmus is blocked by convergence is an observation by Haase,9 who demonstrated electromyographically in patients with the NBS that there is incomplete inhibition of the medial rectus muscle of the nonfixating eye as the fixating eye moves from abduction into adduction. During a conjugate eye movement, one would expect complete inhibition of the medial rectus muscle in the nonfixating eye under such circumstances. On the other hand, convergence innervation, causing increased tonus of both medial rectus muscles, would explain these findings. Further clinical research is needed to determine the roles of accommodative, voluntary, or tonic convergence during blockage of the nystagmus. However, it is reasonable to conclude that the esotropia develops as a consequence of sustained convergence effort. Another interesting clinical feature of the NBS is that it may explain the recurrence of esotropia after multiple operations. This is demonstrated by the findings in Case 12 of this series. A 4-year-old caucasian girl had a large angle esotropia since birth. Four operations had been performed in the following order: 5 mm recession of the right medial and 8 mm resection ofthe right lateral rectus muscle; 5 mm
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recession ofthe left medial and 8 mm resection ofthe left lateral rectus muscle; marginal myotomies of both medial rectus muscles; advancement and additional resection of both lateral rectus muscles. After each operation the angle of strabismus was significantly reduced or the eyes were aligned for short periods of time. This was followed by a rather rapid recurrence of the esotropia. Ductions, versions, and saccadic velocities were remarkably normal and scarring of the conjunctiva was minimal, considering the number of operations performed. There was no obvious mechanical obstacle to nQrmal ocular motility. A jerky manifest nystagmus of both eyes appeared as each eye fixated in a position of abduction; nystagmus was absent in adduction. Upon occluding the left eye, the patient turned her head to the right, thus placing the right, dominant eye into a position of adduction. Surgical failures of this nature can often be explained on the basis of mechanical factors such as scarring, adhesions, disinserted muscles, etc. However, in the absence of such problems, innervational causes must be considered. Continued blockage of the nystagmus by sustained convergence is certainly a more plausible explanation for the persistence of esotropia after surgery than the widely held view that anomalous retinal correspondence causes the eyes to return to their preoperative position. Anomalies of the head posture are frequently encountered with the NBS. If the patient chooses adduction as the position of optimal visual acuity for his dominant eye, the head turn occurs toward the side of the dominant eye; the contralateral eye may become amblyopic (Cases 4, 5, and 6). If there is no strong ocular dominance, or if the amblyopia has been cured by occlusion therapy, the patient will alternate and the head turn may vary according to which eye is used for fixation at any given moment. This pattern was present in cases 3, 7, and 8. If there is rapid alternation of fixation there will be an equally rapid change of the head turn from one to the other side and the esotropic patients with congenital nystagmus described by Robb12 as having "periodic alternation of the null point" may well fall into this category. For the treatment of the NBS in infants, Cuppers8 recommends alternating occlusion combined with "exercises of ocular motility". He claims that this therapy eliminates the blockage mechanism in the large majority of patients. Surgical treatment, consisting of a recession-resection operation is advocated by Cuppers only when the forced duction test performed under general anesthesia becomes positive and progressive contracture of the medial rectus muscle and loss of elasticity of conjunctiva in Tenon's capsule are about to develop. More recently, a posterior fixation
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suture (Fadenoperation) has been successfully employed at the Giessen University Eye Clinic for the treatment of the NBS.10 Conservative therapy consisting of alternating occlusion for a period of up to six weeks was attempted in several of our patients. However, a marked head turn persisted or developed where it had not been present prior to therapy, and we proceeded with surgery in these and in the remainder of our patients who had no other preceding therapy. Except for the surgical overcorrection encountered in cases 9 and 10 and the persistent esotropia in case 12, the results of surgery with a conventional recession-resection procedure on one or both eyes have been gratifying. SUMMARY
A previously unrecognized form of nystagmus associated with esotropia was described in the German literature by Adelstein and Cuppers in 1966 as the nystagmus blockage syndrome. Even though widely publicized in the European ophthalmic literature, this entity has remained virtually unrecognized in this country. We have identified the nystagmus blockage syndrome in 12 of 247 consecutive patients with congenital esotropia. The following characteristic features were encountered: onset of esotropia in early infancy, pseudoabducens paralysis, head turn toward the side of the fixating eye, absence of nystagmus with the fixating eye in adduction, and appearance of a manifest jerky nystagmus as the fixating eye moves into primary position and abduction. It has been suggested that the nystagmus is actively blocked by convergence innervation, the esotropia thus being caused by sustained convergence and secondary changes in the medial rectus muscles. The differential diagnosis includes crossed fixation and bilateral sixth nerve paralysis. ACKNOWLEDGEMENT
I thank Dr Samuel Shoss for his permission to include Case 12 in this paper. REFERENCES
1. Kestenbaum A: Nouvelle operation du nystagmus. Bull Soc Ophtalmol Fr 6:599, 1953. 2. Anderson JR: Causes and treatment of congenital eccentric nystagmus. Br J Ophthalmol 137:267, 1953. 3. Lafon C: La vision des nystagmiques. Ann Ocul (Paris) 151:4, 1914. 4. Ohm J: Das Ohrlabyrinth als Erzeuger des Schielens. Zeitschr Augenheilkd 36:253, 1916.
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5. Franceschetti A, Monnier M, Dieterle P: Analyse du nystagmus congenital par la methode 'electro-nystagmographique (ENG). Bull Schweiz Akad Med Wiss 8:403, 1952. 6. Adelstein F, Cuppers C: Zum Problem der echten und scheinbaren Abducenslamung (das sogenannte "Blockierungs-syndrom"). In AugenmuskeUahmungen, Buch. d. Augenarzt. Stuttgart, F. Enke, 46:271, 1966. 7. Burian HM, von Noorden GK: Binocular Vision and Ocular Motility. Theory and management of strabismus. St. Louis, C.V. Mosby, 1974, p 404. 8. Cuppers C: Probleme der operativen Therapie des okularen Nystagmus. Klin Monatsbl Augenheilkd 159:145, 1971. 9. Haase W: Zur Diagnose und Therapie des Nystagmusblockierungssyndroms (elektromyographische Untersuchungen). Klin Monatsbl Augenheilkd 157:500, 1970. 10. Muhlendyck H, Linnen HJ: Die operative Behandlung nystagmusbedingter schwankender Schielwinkel mit der Fadenoperation nach Cuppers. Klin Monatsbl Augenheilkd 167:273, 1975. 11. Parks MM: Congenital nystagmus surgery. Am Orthop J 23:35, 1973. 12. Robb RM: Periodic alternation of null point in congenital nystagmus. Association with alternating gaze deviation and esotropia. Arch Ophthalmol 87:169, 1972.
DISCUSSION
DR ARTHUR JAMPOLSKY. Officers, members, and guests. I want to thank the author for sending his manuscript to me in advance of this meeting. He is to be congratulated for examining the complex group of infantile esotropes and isolating a category requiring separate diagnostic techniques and perhaps separate treatment techniques. It is only by this method of separating uniquely characteristic cases, from a general mix of congenital or infantile esotropias, that we will begin to make sense regarding treatment. What is the uniquely descriptive distinguishing feature in these cases? I feel that it is as follows: "An esotropia (usually binocular, but may be monocular) in which there is marked preference for fixation in adduction, with nystagmus increasing toward abduction, with or without a real limitation of abduction. " The most interesting cases are those without any demonstrable limitation of abduction but without any real ability to maintain steady fixation in abduction, nor in fact in the primary position. Characteristically, there is a head turn, to fix with each eye in extreme adduction, where the nystagmus is minimal or absent. This was well described by Kestenbaum as unimacular nystagmus. He stated, "As is always the case, the right nystagmus became more severe engaged to the right, and less severe engaged to the left, i. e., in adduction of the right eye. The patient achieved this adduction by rotating his head to the right, and fixating with his now adducted right eye. The opposite happened when the left eye tried to fixate: head rotation to the left, fixation with the left, now adducted eye." The Dutch school (Keiner, Zeeman, and Crone) have repeatedly emphasized the abnormalities of the monocular reflexes, rather than the binocular reflexes so traditionally popular. This is entirely consistent with the term "unimacular" and consistent with my own views that there is an abnormality of the motor systems, as reflected in the monocular fixation and saccadic and pursuit mechanisms, as the common etiological basis for many of the phenomena seen in the group of infantile esotropes under discussion.
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A. Ciancia further analyzed such patients and well described the adduction fixation preference, with increased nystagmus toward abduction, and later added some electrooculographic recordings of the nystagmus in such patients. Different authors have put forth different causation theories of this entity. The author points out that Cuppers and Adelstein in 1966 proposed a mechanism of "blocked nystagmus", and the author has proposed his own notion of the mechanism of the blocked nystagmus by sustained convergence. My own interest in such cases was sparked by Ciancia's description of the entity and his electrooculographic studies. In 1974 at the September meeting of the Pacific Section of the Association for Research in Vision and Ophthalmology, held in San Francisco, I showed some electrooculograms that analyzed the abduction nystagmus with a view toward providing evidence that the defect was in the "hold" mechanism, i. e., the second part of the saccadic system. Others showed some brief fixation hold in extreme abduction, but apparently were driven off by an unharnessed pursuit system. Since that time we have recorded electrooculograms showing that there is a true neutral point of nystagmus in extreme adduction, in some patients, with the fast component toward adduction, when one records the eye movements in the very extreme few degrees offurther adduction. It is obvious that there are many mixed patterns of motor system defects in this group of patients depicting adduction fixation preference. My own theory is that this is a defect of one of the motor systems, a neural deficit. We are all familiar with the immature development of the input system, i. e., the underdeveloped macula at birth. Sufficient attention has not been directed toward the possible immaturity and maldeveloped motor systems in developmental esotropia. Cogan has described similar fixation-hold defects in the extreme fields of gaze, as occurring in rehabilitated saccades. It is also found in several cerebellectomized monkeys. I believe there to be a distinct relationship among the following cases, all exhibiting adduction fixation preference with increasing nystagmus toward abduction: 1) Alternating infantile esotropia, with each eye preferring adduction fixation, and compensatory head turn; 2) unilateral strabismus (relative amblyopia of the non-fixing eye), with either esotropia or exotropia; and 3) neutral point of nystagmus, wherein the nonfixing eye is "orthotropic" without evident alignment. It matters now whether the nondominant eye is parallel (as in neutral or null point nystagmus) or an amblyopic esotropic eye or an equal visioned alternating eye (wherein the mechanism exists in each eye). The fixing eye's dominant role in preferring extreme adduction fixation is of paramount importance. Many authors have advocated a large recession ofthe medial rectus in order to stabilize fixation in the primary position. This has ranged from 7 to 9 mm, and my recent experience during the past year has indicated the desirability of this procedure in selected instances. Certainly the medial rectus must be recessed a considerable degree if there is to be a tonus balance reestablished. I would like to ask the author two questions: 1) Why the difference of 44% incidence of Ciancia's cases of esotropes with this characteristic, without restriction
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in abduction and 2) his comments relative to my own proposed causation theory of a neurologic deficit of one of the motor control systems. I want to congratulate the author for again calling attention to the differential diagnosis of the mixed group of infantile esotropes, which highlights the point that there is no single etiologic cause and certainly no single surgical treatment in the management of infantile esotropia. DR PHILIP KNAPP. I would like to congratulate Doctor von Noorden for bringing this syndrome to our attention. As he stated, for the last ten years in Europe this has been an important subject. When Doctor DeDecker was here last summer for the International Orthoptic Congress, he had already done 2,000 of these Faden operations. Muhlendyck, in the paper that Doctor von Noorden referred to, stressed two facts that I think are important. I don't think Doctor von Noorden gave these quite enough emphasis. One is if you take these children and just have them follow a light, quite frequently they will end up with both eyes maximally adducted looking almost like strabismus fixus. If you then cover one eye and make the child look with the other eye, the nystagmus increases as the eye abducts, finally fully, and the angle of esotropia decreases. This is against the diagnosis of a VI nerve paresis. As you know, with a VI nerve paresis the esotropia gets worse when you get into the field of action of the lateral rectus so this makes your differential diagnosis for you. The surgeon is faced with a child who varies between 150 and 30 diopters of esotropia. Both eyes go in dramatically. Then at times the eyes are practically parallel which is why this Faden or posterior suture technique was devised. I have done 46 Faden operations upon 31 patients in the last five months. I've done three of them for this so-called nystagmus blockage syndrome and the results have been rewarding. The principle used is that you do a mild recession for the static angle of esotropia then you use this suture which should be 13 mm posterior to the insertion of the medial rectus-not 10 mm. Cuppers originally said 10 mm but he changed it in 1974. So far, two of the three patients have been practically cured and the other is greatly improved. Obviously the follow-up is very inadequate, being only a few months. DR KENNETH SWAN. We are indebted to Doctor von Noorden for calling the attention of American ophthalmologists to this group of patients. Since reading about it in the European literature, Andrea Tongue and I have been reviewing patients in the Oregon Children's Eye Clinic and have identified a number with this clinical entity. One is worth discussing, because I have followed her course and taken photos for 27 years. [Slide] This girl was referred to me when she was just a few months old with a differential diagnosis of bilateral VIth paralysis or strabismus fixus, but those conditions were excluded. A few months later the parents noted that whenever the infant looked at anything intently she would turn her face to the right [Slide]. They interpreted this as a crossing of the right eye, but indeed the child was fixating with the right eye at the null point of nystagmus. When forced to abduct either eye to the midline, gross nystagmus would develop. We were con-
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servative in her surgical management for several reasons. One was that when this child was drowsy or partially awake, her eyes would straighten. The next slide, taken in 1951 when the child was two years old, again shows her face turned to keep the fixating right eye in adduction. We had the dual problem of shifting the null point of the nystagmus in each eye to a more central position and at the same time reducing the esotropia. Bilateral medial rectus recessions were pefformed in 1952. The operative note described that her eyes straightened under anesthesia and forced ductions revealed no limitation, features described for this entity in the European literature. The next slide shows that in 1956, at age 7, her eyes were in good alignment. She had no face turn and nystagmus only with abduction. At age 14 she began to show a left hypertropia. I recessed her left inferior oblique at age 17. One year later photo shows that the hyper was corrected. The final slide, taken the first week in May of 1976, reveals no deviation. She was asymptomatic; however, her visual acuity was 20/25 maximal. The visuscope revealed a fine searching nystagmus in the central field. With abduction of 25 degrees or more ofeither eye, she still developed a gross nystagmus. Unfortunately, the bridge of her nose was so high that I was unable to determine whether fixating with her left eye in right gaze would eliminate this nystagmus. This patient's course illustrated that early surgery to shift the null point of the nystagmus and to reduce the nystagmus and to reduce the esotropia was effective for this condition. Her condition was markedly improved and has been stable for more than 25 years. Thank you. DR GUNTER VON NOORDEN. I would like to thank the discussors for their very pertinent comments. I do not know the reason for the difference in the incidence of the nystagmus blockage syndrome in Ciancia's and my series. I am doubtful, however, whether the nystagmus in esotropes described by Ciancia qualifies for inclusion under this diagnosis according to the criteria set forth by Adelstein and Cuppers and in this paper. I agree with Dr Jampolsky that the nystagmus in these patients is of the motor defect type, as defined by Cogan. The esotropia develops secondarily and as the result of an effort to neutralize the nystagmus. I also share Dr Jampolsky's concern with respect to the need for further study ofthis intriguing entity by electrooculography and electromyography. I am sure that much can be learned from this ap-
proach. I was very interested to hear Dr Knapp has already had much experience in the treatment of this condition with the new strabismus operation, introduced by Cuppers as the "Fadenoperation." I too have been experimenting with this procedure and believe that it may evolve as a major advance in the surgical treatment of certain forms of strabismus. The essence of this procedure is to alter the effectiveness of an extraocular muscle in one position of gaze without affecting it in others and without changing the tonus of its antagonist. Thus, it is especially applicable as an operation to weaken adduction in patients with a large dynamic angle of esotropia, the size of which depends on the state of attention as in the nystagmus blockage syndrome. However, the German term "Fadenoperation" is rather
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meaningless and has been used by earlier authors to describe what we call traction sutures. It would be more appropriate to replace it in English with "posterior fixation" or "retropexy" of an extraocular muscle. Dr Swan points out that in patients with the nystagmus blockage syndrome, the eyes may straighten under general anesthesia. Adelstein and Cuppers make a strong point of this. I doubt that this phenomenon is really pathognomonic for the nystagmus blockage syndrome since straightening ofthe eyes or even exotropia under general anesthesia is not an uncommon occurrence in esotropes and not restricted to patients with the nystagmus blockage syndrome. I was most interested to hear the detailed description of Dr Swan's case which adds yet another one to the increasing number of patients with the nystagmus blockage syndrome that we have now learned to recognize. Again, I wish to thank all the discussors for their helpful and constructive comments.
![[A new method of surgery of nystagmus blockage syndrome].](/assets/img/hold.png)
