Ann Otol Rhinol Laryngol99: 1990
POSTERIOR SEMICIRCULAR CANAL OCCLUSION FOR INTRACTABLE BENIGN PAROXYSMAL POSITIONAL VERTIGO LORNE S. PARNES, MD
JOSEPH
A.
MCCLURE, MD
LONDON, CANADA
Benign paroxysmal positional vertigo (BPPV) is most often a self-limited disorder arising from the posterior semicircular canal of the undermost ear in the Hallpike position. Some individuals with this disorder have severe and protracted symptoms requiring more than expectant therapy. We describe two patients with intractable BPPV and profound sensorineural hearing loss in the affected ear treated by transmastoid posterior semicircular canal occlusion. Postoperatively, both were relieved of their BPPV and demonstrated preserved lateral semicircular canal function as measured by electronystagmography. We feel this new procedure provides a simpler and possibly safer alternative to singular neurectomy and should be given future consideration in the treatment of intractable BPPV in a normal-hearing ear. KEY WORDS -
benign paroxysmal positional vertigo, cupulolithiasis, posterior semicircular canal occlusion.
INTRODUCTION
ated with position change, patients may complain of protracted nonspecific imbalance and dizziness accompanied by mild lassitude.
Benign paroxysmal positional vertigo (BPPV) is a common vestibular end organ disorder. In one busy vestibular clinic it was diagnosed in 17 % of patients. I It is most often an idiopathic or degenerative disorder, occurring frequently in the middle to late decades.' Head trauma, the second most common cause, underlies most cases of bilateral BPPV. 3 Other, less frequent causes include viral labyrinthitis, vestibular neuronitis, stapedectomy, perilymph fistula, and Meniere's disease."
As most cases of BPPV are self-limited, we treat our patients expectantly. If severe symptoms persist unchanged for greater than 1 year, then it is probable that the BPPV is permanent, and a diagnosis of cupulolithiasis is made. If the symptoms have a significant effect upon the patient's life-style or occupation, we feel that operative intervention is indicated. The mainstay of operative treatment has been the singular nerve section described initially by Cacek.:" Singular neurectomy selectively eliminates posterior semicircular canal function. However, as Silverstein II pointed out, singular neurectomy is a very difficult operation to learn and has a significant risk of failure and sensorineural hearing loss in inexperienced hands. In a recent human temporal bone study, Ohmichi et a1'2 demonstrated that the singular nerve was inaccessible through a tympanotomy approach in 14 % of the bones examined. These nerves were shielded by the labyrinth, and successful singular nerve section in such cases likely would ravage the inner ear.
The pathologic site of BPPV has been localized to the posterior semicircular canal. 5 Schuknecht and Ruby" found large basophilic deposits (presumably displaced otoconia) attached to the posterior semicircular canal cupula on examination of postmortem temporal bones from patients with clinical BPPV. They coined the term cupulolithiasis to describe this finding. The Hallpike maneuver rotates the posterior semicircular canal of the undermost ear in the earth vertical plane. The classic findings with left-sided involvement are a clockwise rotatory nystagmus in the left head-hanging position, and with right-sided involvement, a counterclockwise rotatory nystagmus in the right head-hanging position. Although various combinations of rotatory, vertical, and oblique eye movements have been described depending upon the position of the globe within the orbit, the nystagmus profile correlates with the known neuromuscular pathways arising from the posterior canal of the undermost ear. 5.7-9
Money and Scott" developed a technique in cats that involved plugging individual semicircular canals. They established that plugging a semicircular canal completely blocked its receptivity without influencing the functions of the other vestibular receptors. On the basis of the findings of Money and Scott, we postulated that the symptoms associated with cupulolithiasis could be relieved by posterior semicircular canal occlusion on the affected side. Posterior semicircular canal occlusion through a transmastoid approach would be a simpler and possibly safer alternative to a singular neurectomy. Of concern was the possibility of cochlear damage with this procedure, and Money and Scott had not addressed this possibility in their study. To examine
Most cases of BPPV, particularly the posttraumatic variety, are self-limited. However, the course often can be protracted, with up to one third of patients in a large series reporting symptoms dating back for more than 1 year. 4 Not uncommonly, the chronic cases may demonstrate periods of exacerbation and remission. When the disease is very active, in addition to the brief episodes of vertigo associ-
From the Department of Otolaryngology, University of Western Ontario, London, Canada. REPRINTS - Lome S. Parnes, MD, Dept of Otolaryngology, University Hospital, 339 Windermere Rd, London, Ontario, N6A 5A5 Canada.
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Fig 1. Preoperative computed tomograms of temporal bones, showing areas of posterior semicircular canal to be occluded (arrows). A) (Case 1) Left temporal bone. B) (Case 2) Right temporal bone.
these effects, a study was carried out on guinea pigs in which brain stem auditory evoked responses were measured before and after posterior canal occlusion.!" The canal occlusion was obtained by making a small "puncture" through the posterior semicircular canal with a diamond bur. This action resulted in simultaneous plugging of the adjacent canal ends with impacted bone chips. With this procedure, there was minimal effect on the brain stem evoked auditory responses, suggesting no cochlear damage. With this background, the transmastoid posterior canal occlusion technique was carried out on two patients with intractable BPPV. CASE REPORTS
Case 1. This 70-year-old woman presented with a 2-year history of positional vertigo. At the age of 68, she suddenly lost hearing in the left ear. The following day she experienced sudden onset of vertigo, along with nausea and vomiting. The intense vertigo persisted for the next 3 days and was made worse by any head movement. Following resolution of the intense steady vertigo, she continued to experience short-lived (30 seconds) episodes of vertigo associated with changes in head position such as getting out of bed, lying on her left side, or rolling over in bed. She found it difficult to perform normal household duties because of the exquisite sensitivity of the disorder, which often was triggered by the slightest head movement either up or down and to the left. She had a persistent nonpulsatile roaring tinnitus in her left ear and no recovery of hearing. Physical examination revealed a severe sensorineural hearing loss in the left ear. On the Hallpike test in the left head-hanging position after a 3-second latency she developed a violent clockwise rotatory nystagmus lasting 20 to 30 seconds. On her re-
turning to the sitting position, a milder counterclockwise nystagmus with latency was seen. Her symptoms of vertigo and nausea were replicated perfectly with this maneuver. The vertigo and nystagmus were absent with a second Hallpike maneuver during individual examinations, but were reproduced easily during four different visits. Her audiogram revealed a profound left-sided sensorineural hearing loss and normal hearing on the right. On electronystagmography (ENG) with horizontal leads, there was no spontaneous or positional nystagmus. Hot (44°C) and cold (30°C) caloric stimulation produced peak slow phase velocities of 53 ° /sand 27 ° /s, respectively, in the right ear, and 68° /s and 31 ° Is, respectively, in the left ear. Axial computed tomograms of the left temporal bone were normal and demonstrated a well-pneumatized mastoid (Fig lA). A diagnosis of cupulolithiasis was made. Various treatment options were discussed with the patient, and she wished to pursue operative intervention. With a complete hearing loss in the affected ear, she was an ideal first candidate for posterior semicircular canal occlusion. We used the original canal "puncture" technique as outlined in our guinea pig study. 14 Following the "puncture," perilymph continued to ooze through the impacted bone chips. This did not occur in the guinea pig model, probably because of the smaller size of the canal. The puncture was sealed with human fibrinogin glue (Tisseel; Immuno AG, Vienna) and a layer of fascia, which checked the perilymph leak. Postoperatively, the patient experienced severe vertigo for 1 week, which was aggravated by all head movements. There was a slight pendular type horizontal/rotatory nystagmus that resolved over 1 week. Four days postoperatively, the ENG showed
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moderate impairment of both saccadic and smooth pursuit movements but no spontaneous nystagmus with eyes closed. Surprisingly, there was no response to cold caloric stimulation on either side. The ENG at 7 days again showed absence of spontaneous nystagmus with eyes closed, and no positional nystagmus. Cold caloric stimulation showed improved responses of 20° Is on the left and 23° Is on the right. The patient was discharged on the 11th postoperative day, and by day 17 she was starting to return to her normal daily activities. At this time the results of her first postoperative Hallpike test proved to be completely negative for nystagmus and vertigo. An ENG showed normal saccadic and smooth pursuit movements with absence of gaze nystagmus. Cold calories had improved to 26° Is on the left and 35° Is on the right. After 1 year she continues to be symptom-free and describes an overall improvement in well-being compared to her preoperative state. She describes an increased energy level with freedom from the chronic vague imbalance sensation she had experienced preoperatively between her major vertigo spells. Case 2. This 57-year-old woman presented with a
21/ z-year history of positional vertigo. At the age of 54 she presented to another otolaryngologist with a gradual progressive right-sided hearing loss. A presumptive diagnosis of otosclerosis was made, and she underwent a stapedectomy with prosthesis. Postoperatively her hearing was much worse, and 6 months later a revision was attempted. Immediately following this revision, she experienced her first spell of positional vertigo that persisted despite a second attempted revision 6 months later. As well, she noted a complete loss of hearing in the operative ear after the first revision, with no improvement following the second revision. Her attacks of vertigo occurred daily. They were provoked by certain head movements and lasted a maximum of 20 seconds. The vertigo was most distressing at her workplace, a canning factory in which she was a supervisor. Her work entailed frequent bending and lifting that often triggered the vertigo. With time she found the constant attention required to avoid these spells was significantly restricting her job performance, and she was therefore referred to our institution for operative intervention. Physical examination demonstrated a severe right-sided sensorineural hearing loss. On the Hallpike test in the right head-hanging position, following a latency period of 3 seconds, she developed a violent counterclockwise rotatory nystagmus lasting approximately 20 seconds. There was a reversal of the nystagmus, but of less intensity, with an initial latency period of 2 to 3 seconds upon her returning to the sitting position. The response, which fatigued on repeat testing, also was demonstrated on two
other clinic visits. An audiogram showed a profound sensorineural hearing loss in the right ear and normal hearing in the left. The ENG with horizontal leads showed an absence of spontaneous or positional nystagmus. Caloric responses on the left were 74° Is and 56° Is following hot and cold stimulation. Right-sided calories were 41 ° Is after both hot and cold stimulation. The CT showed normal findings, including a moderately well-pneumatized mastoid (Fig IB). A diagnosis of cupulolithiasis was made, and after a long, careful discussion about various treatment options, the patient wished to pursue transmastoid posterior semicircular canal occlusion. The occlusion technique was modified from the original "puncture." A 2- to 3-mm posterior canal segment was blue-lined through 180° around the outer turn. The endosteum was opened with a small 90° hook, with care taken not to aspirate the inner ear fluids. Bone paste from the mastoidectomy was delivered into the opening in a gentle but firm fashion with the intention of compressing the membranous labyrinth while maintaining its integrity. A layer of bone wax plus a second layer of fascia stopped the perilymph leak. This patient's postoperative course was considerably more tolerable. There was no spontaneous vertigo or nystagmus throughout the postoperative period. Certain head movements such as sitting up or lying down continued to make her vertiginous for the first 5 or 6 days. A Hallpike test on the third postoperative day showed the same preoperative nystagmus but with much less intensity. She was now ambulating and was discharged on her fifth postoperative day. She continued to improve symptomatically, and by day 8 the Hallpike test showed a further reduction of the induced nystagmus intensity. The ENG showed absence of a spontaneous or gaze nystagmus. Caloric responses to hot and cold stimuli were now 98° Is and 48° Is on the left and 21° Is and 26° Is on the right. On follow-up 2 weeks later, she reported complete absence of vertigo despite provocative efforts. Her mild imbalance continued to improve on a daily basis. The results of the Hallpike maneuver were now completely negative, and the results on ENG were essentially unchanged from those of the previous study. She remains symptom-free after 9 months of follow-up. DISCUSSION
The preliminary results from these two patients suggest that posterior semicircular canal occlusion can relieve the symptoms associated with intractable BPPV, or what many refer to as cupulolithiasis. Hall et al " divided BPPV into fatigable and non fatigable types and suggested that free-floating particles caused the former and that particles fixed
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Parnes & McClure, Posterior Semicircular Canal Occlusion
----- SITE OF OCCWSION
Fig 2. Schematic representation of occluded posterior semicircular canal. Shaded area - closed fluid (endoIymph)- filled space between impermeable cupula and site of occlusion.
to the cupula caused the latter. It was suggested that a fatigable and nonfatigable classification could provide the diagnostic criteria separating BPPV that subsides spontaneously from cupulolithiasis. As both patients in this study had fatigable BPPV, one for 2 years and the other for 2 1/ 2 years, it seems more appropriate to classify BPPV on the basis of duration of symptoms. If symptoms persist unchanged for greater than 1 year, the BPPV is unlikely to resolve, and the diagnosis of cupulolithiasis is made. The patient becomes a potential candidate for posterior semicircular canal occlusion. Conventional theory explains the signs and symptoms of BPPV on the basis of endolymph flow, and in turn cupular deflection, when loose particles in the endolymph of the posterior semicircular canal move under the influence of gravity. Similarly with cupulolithiasis, a mass on the cupula can move under the influence of gravity and induce cupular deflection. In either case, cupular deflection implies endolymph displacement. However, with the semicircular canal occluded, a closed fluid-filled space is created between the site of occlusion and the cupula, as illustrated in Fig 2. Since fluid cannot be compressed or expanded, the closed fluid-filled space acts as a solid member, and the cupula becomes fixed. Singular neurectomy eliminates the resting discharge from the posterior canal, creating a static asymmetry" between the two posterior canals. In this situation, one would anticipate persistent vertigo along with rotatory/vertical spontaneous nystagmus with the patient at rest. Posterior canal occlu-
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sion does not disturb the resting discharge from the occluded canal, so one would not expect symptoms with the patient at rest, as demonstrated in the second patient. However, the first patient did develop a spontaneous nystagmus. We suspect that trauma from the canal "puncture" caused a labyrinthitis resulting in temporary canal paresis, and this would be supported by the reduced caloric response. The simultaneous reduction in caloric response on the opposite side is difficult to explain, but may represent some form of cerebellar clamp. '7 With both singular neurectomy and posterior canal occlusion, head movement produces a dynamic asymmetry. 16 One would expect symptoms from posterior canal stimulation, and this proved to be the case with both patients. The dynamic asymmetry appeared to adapt completely within a few weeks. We opted to change the occlusion technique in the second patient for three reasons. The first was to minimize the amount of canal trauma and reduce the degree of labyrinthitis. The second reason related to the anatomy of the mastoid. The mastoid in the second case was less pneumatized than in the first (Fig 1), and the posterior semicircular canal was sitting flush against the cerebellar plate. A technique was required that would avoid inadvertent breach of the posterior fossa dura during the canal puncture. The third reason was more theoretic, and related to future canal occlusions in normalhearing patients. We felt that drilling through endolymph and perilymph was likely to be more traumatic to the organ of Corti than drilling on otic capsule bone alone. The "compression" technique used for the second case proved to be just as effective as the original "puncture." The transmastoid approach provides easy access to the posterior semicircular canal for occlusion. In creating the occlusion, we stress the importance of using bone chips to promote new bone formation" leading to complete permanent occlusion of the canal. We have shown in two patients that posterior semicircular canal occlusion can relieve intractable BPPV (cupulolithiasis) and at the same time preserve lateral semicircular canal function. The effect of canal occlusion on hearing in the otherwise normal human ear is unknown. However, since animal studies':' indicate no deleterious effect on hearing, we feel that this procedure now should be given consideration in the treatment of the normal-hearing ear with BPPV.
REFERENCES 1. Nedzelski JM, Barber HO, McIlmoyl L. Diagnoses in a dizziness unit. J Otolaryngol 1986;15:101-4. 2. Barber HO, Leigh RJ. Benign (and not so benign) postural vertigo: diagnosis and treatment. In: Barber HO, Sharpe A, eds. Vestibular disorders. Boca Raton, Fla: CRC Press, 1988:215-32. 3. Longridge NS, Barber HO. Bilateral paroxysmal positioning nystagmus. J Otolaryngol 1978;7:395-400.
4. Baloh RW, Honrubia V, Jacobson K. Benign positional vertigo: clinical and oculographic features in 240 cases. Neurology 1987;37:371-8. 5. Baloh RW. Sakala S, Honrubia V. The mechanism of benign paroxysmal positional nystagmus. Adv Otorhinolaryngol 1979;25: 161-6. 6. Schuknecht HF, Ruby RRF. Cupulolithiasis. Adv Oto-
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rhinolaryngol 1973;20:434-43. 7. Katsarkas A, Outerbridge JS. Nystagmus of paroxysmal positional vertigo. Ann Otol Rhinol LaryngoI1983;92:146-50. 8. Harbert F. Benign paroxysmal positional vertigo. Arch Ophthalmol 1970;84:298-302. 9. Cohen B, Suzuki J, Bender MB. Nystagmus induced by electrical stimulation of ampullary nerves. Acta Otolaryngol (Stockh) 1965;60:422-36.
13. Money KE, Scott JW. Functions of separate sensory receptors of nonauditory labyrinth of the cat. Am J Physiol 1962; 202:1211-20. 14. Parnes LS, McClure JA. Effect on brainstem auditory evoked responses of posterior semicircular canal occlusion in guinea pigs. J OtolaryngoI1985;14:145-50. 15. Hall SF, Ruby RRF, McClure JA. The mechanics of benign paroxysmal vertigo. J Otolaryngol 1979;8:151-8.
10. Gacek RR. Transection of the posterior ampullary nerve for the relief of benign paroxysmal positional vertigo. Ann Otol Rhinol Laryngol 1974;83:596-605.
16. McClure JA, Lycett P. Vestibular asymmetry. Arch Otolaryngol 1983;109:682-7.
11. Silverstein H. Singular neurectomy: a treatment for benign positional vertigo. In: Brackmann DE, ed. Neurological surgery of the ear and skull base. New York: Raven Press, 1982:331-5.
17. McCabe BF. Vestibular physiology: its clinical application in understanding the dizzy patient. In: Paparella MM, Shumrick DA, eds. Otolaryngology. Philadelphia: WB Saunders, 1980: 241-52.
12. Ohmichi T, Rutka J, Hawke M. Histopathologic consequences of surgical approaches to the singular nerve. Laryngoscope 1989;99:963-70.
18. Altmann F. Healing of fistulas of the human labyrinth. Arch Otolaryngol 1946;43:409-21.
THE DEAFNESS RESEARCH FOUNDATION 1991 RESEARCH GRANTS AVAILABLE The Deafness Research Foundation invites applications for 1991 grant support of new research that promises to advance our understanding of the causes, treatment, and prevention of deafness and related ear disorders. The grants will be awarded to tax-exempt institutions for projects that will begin January 1, 1991, with the principal investigator of each project a member of the staff or faculty of such institution. The grants do not exceed $15,000, and can be competitively renewed with the same limit for an additional 1 or 2 years. Applications are reviewed for scientific merit of the proposed investigations and for their direct or potential clinical importance. The deadline for first year applications is July 15, 1990, and for renewal applications is August 15, 1990. For full information on the grant program, and for the required application form, please write to Walter A. Petryshyn, MD, Medical Director, The Deafness Research Foundation, 9 East 38th Street, New York, NY 10016; (212) 684-6556.
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POSTERIOR SEMICIRCULAR CANAL OCCLUSION FOR INTRACTABLE BENIGN PAROXYSMAL POSITIONAL VERTIGO LORNE S. PARNES, MD
JOSEPH
A.
MCCLURE, MD
LONDON, CANADA
Benign paroxysmal positional vertigo (BPPV) is most often a self-limited disorder arising from the posterior semicircular canal of the undermost ear in the Hallpike position. Some individuals with this disorder have severe and protracted symptoms requiring more than expectant therapy. We describe two patients with intractable BPPV and profound sensorineural hearing loss in the affected ear treated by transmastoid posterior semicircular canal occlusion. Postoperatively, both were relieved of their BPPV and demonstrated preserved lateral semicircular canal function as measured by electronystagmography. We feel this new procedure provides a simpler and possibly safer alternative to singular neurectomy and should be given future consideration in the treatment of intractable BPPV in a normal-hearing ear. KEY WORDS -
benign paroxysmal positional vertigo, cupulolithiasis, posterior semicircular canal occlusion.
INTRODUCTION
ated with position change, patients may complain of protracted nonspecific imbalance and dizziness accompanied by mild lassitude.
Benign paroxysmal positional vertigo (BPPV) is a common vestibular end organ disorder. In one busy vestibular clinic it was diagnosed in 17 % of patients. I It is most often an idiopathic or degenerative disorder, occurring frequently in the middle to late decades.' Head trauma, the second most common cause, underlies most cases of bilateral BPPV. 3 Other, less frequent causes include viral labyrinthitis, vestibular neuronitis, stapedectomy, perilymph fistula, and Meniere's disease."
As most cases of BPPV are self-limited, we treat our patients expectantly. If severe symptoms persist unchanged for greater than 1 year, then it is probable that the BPPV is permanent, and a diagnosis of cupulolithiasis is made. If the symptoms have a significant effect upon the patient's life-style or occupation, we feel that operative intervention is indicated. The mainstay of operative treatment has been the singular nerve section described initially by Cacek.:" Singular neurectomy selectively eliminates posterior semicircular canal function. However, as Silverstein II pointed out, singular neurectomy is a very difficult operation to learn and has a significant risk of failure and sensorineural hearing loss in inexperienced hands. In a recent human temporal bone study, Ohmichi et a1'2 demonstrated that the singular nerve was inaccessible through a tympanotomy approach in 14 % of the bones examined. These nerves were shielded by the labyrinth, and successful singular nerve section in such cases likely would ravage the inner ear.
The pathologic site of BPPV has been localized to the posterior semicircular canal. 5 Schuknecht and Ruby" found large basophilic deposits (presumably displaced otoconia) attached to the posterior semicircular canal cupula on examination of postmortem temporal bones from patients with clinical BPPV. They coined the term cupulolithiasis to describe this finding. The Hallpike maneuver rotates the posterior semicircular canal of the undermost ear in the earth vertical plane. The classic findings with left-sided involvement are a clockwise rotatory nystagmus in the left head-hanging position, and with right-sided involvement, a counterclockwise rotatory nystagmus in the right head-hanging position. Although various combinations of rotatory, vertical, and oblique eye movements have been described depending upon the position of the globe within the orbit, the nystagmus profile correlates with the known neuromuscular pathways arising from the posterior canal of the undermost ear. 5.7-9
Money and Scott" developed a technique in cats that involved plugging individual semicircular canals. They established that plugging a semicircular canal completely blocked its receptivity without influencing the functions of the other vestibular receptors. On the basis of the findings of Money and Scott, we postulated that the symptoms associated with cupulolithiasis could be relieved by posterior semicircular canal occlusion on the affected side. Posterior semicircular canal occlusion through a transmastoid approach would be a simpler and possibly safer alternative to a singular neurectomy. Of concern was the possibility of cochlear damage with this procedure, and Money and Scott had not addressed this possibility in their study. To examine
Most cases of BPPV, particularly the posttraumatic variety, are self-limited. However, the course often can be protracted, with up to one third of patients in a large series reporting symptoms dating back for more than 1 year. 4 Not uncommonly, the chronic cases may demonstrate periods of exacerbation and remission. When the disease is very active, in addition to the brief episodes of vertigo associ-
From the Department of Otolaryngology, University of Western Ontario, London, Canada. REPRINTS - Lome S. Parnes, MD, Dept of Otolaryngology, University Hospital, 339 Windermere Rd, London, Ontario, N6A 5A5 Canada.
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Fig 1. Preoperative computed tomograms of temporal bones, showing areas of posterior semicircular canal to be occluded (arrows). A) (Case 1) Left temporal bone. B) (Case 2) Right temporal bone.
these effects, a study was carried out on guinea pigs in which brain stem auditory evoked responses were measured before and after posterior canal occlusion.!" The canal occlusion was obtained by making a small "puncture" through the posterior semicircular canal with a diamond bur. This action resulted in simultaneous plugging of the adjacent canal ends with impacted bone chips. With this procedure, there was minimal effect on the brain stem evoked auditory responses, suggesting no cochlear damage. With this background, the transmastoid posterior canal occlusion technique was carried out on two patients with intractable BPPV. CASE REPORTS
Case 1. This 70-year-old woman presented with a 2-year history of positional vertigo. At the age of 68, she suddenly lost hearing in the left ear. The following day she experienced sudden onset of vertigo, along with nausea and vomiting. The intense vertigo persisted for the next 3 days and was made worse by any head movement. Following resolution of the intense steady vertigo, she continued to experience short-lived (30 seconds) episodes of vertigo associated with changes in head position such as getting out of bed, lying on her left side, or rolling over in bed. She found it difficult to perform normal household duties because of the exquisite sensitivity of the disorder, which often was triggered by the slightest head movement either up or down and to the left. She had a persistent nonpulsatile roaring tinnitus in her left ear and no recovery of hearing. Physical examination revealed a severe sensorineural hearing loss in the left ear. On the Hallpike test in the left head-hanging position after a 3-second latency she developed a violent clockwise rotatory nystagmus lasting 20 to 30 seconds. On her re-
turning to the sitting position, a milder counterclockwise nystagmus with latency was seen. Her symptoms of vertigo and nausea were replicated perfectly with this maneuver. The vertigo and nystagmus were absent with a second Hallpike maneuver during individual examinations, but were reproduced easily during four different visits. Her audiogram revealed a profound left-sided sensorineural hearing loss and normal hearing on the right. On electronystagmography (ENG) with horizontal leads, there was no spontaneous or positional nystagmus. Hot (44°C) and cold (30°C) caloric stimulation produced peak slow phase velocities of 53 ° /sand 27 ° /s, respectively, in the right ear, and 68° /s and 31 ° Is, respectively, in the left ear. Axial computed tomograms of the left temporal bone were normal and demonstrated a well-pneumatized mastoid (Fig lA). A diagnosis of cupulolithiasis was made. Various treatment options were discussed with the patient, and she wished to pursue operative intervention. With a complete hearing loss in the affected ear, she was an ideal first candidate for posterior semicircular canal occlusion. We used the original canal "puncture" technique as outlined in our guinea pig study. 14 Following the "puncture," perilymph continued to ooze through the impacted bone chips. This did not occur in the guinea pig model, probably because of the smaller size of the canal. The puncture was sealed with human fibrinogin glue (Tisseel; Immuno AG, Vienna) and a layer of fascia, which checked the perilymph leak. Postoperatively, the patient experienced severe vertigo for 1 week, which was aggravated by all head movements. There was a slight pendular type horizontal/rotatory nystagmus that resolved over 1 week. Four days postoperatively, the ENG showed
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moderate impairment of both saccadic and smooth pursuit movements but no spontaneous nystagmus with eyes closed. Surprisingly, there was no response to cold caloric stimulation on either side. The ENG at 7 days again showed absence of spontaneous nystagmus with eyes closed, and no positional nystagmus. Cold caloric stimulation showed improved responses of 20° Is on the left and 23° Is on the right. The patient was discharged on the 11th postoperative day, and by day 17 she was starting to return to her normal daily activities. At this time the results of her first postoperative Hallpike test proved to be completely negative for nystagmus and vertigo. An ENG showed normal saccadic and smooth pursuit movements with absence of gaze nystagmus. Cold calories had improved to 26° Is on the left and 35° Is on the right. After 1 year she continues to be symptom-free and describes an overall improvement in well-being compared to her preoperative state. She describes an increased energy level with freedom from the chronic vague imbalance sensation she had experienced preoperatively between her major vertigo spells. Case 2. This 57-year-old woman presented with a
21/ z-year history of positional vertigo. At the age of 54 she presented to another otolaryngologist with a gradual progressive right-sided hearing loss. A presumptive diagnosis of otosclerosis was made, and she underwent a stapedectomy with prosthesis. Postoperatively her hearing was much worse, and 6 months later a revision was attempted. Immediately following this revision, she experienced her first spell of positional vertigo that persisted despite a second attempted revision 6 months later. As well, she noted a complete loss of hearing in the operative ear after the first revision, with no improvement following the second revision. Her attacks of vertigo occurred daily. They were provoked by certain head movements and lasted a maximum of 20 seconds. The vertigo was most distressing at her workplace, a canning factory in which she was a supervisor. Her work entailed frequent bending and lifting that often triggered the vertigo. With time she found the constant attention required to avoid these spells was significantly restricting her job performance, and she was therefore referred to our institution for operative intervention. Physical examination demonstrated a severe right-sided sensorineural hearing loss. On the Hallpike test in the right head-hanging position, following a latency period of 3 seconds, she developed a violent counterclockwise rotatory nystagmus lasting approximately 20 seconds. There was a reversal of the nystagmus, but of less intensity, with an initial latency period of 2 to 3 seconds upon her returning to the sitting position. The response, which fatigued on repeat testing, also was demonstrated on two
other clinic visits. An audiogram showed a profound sensorineural hearing loss in the right ear and normal hearing in the left. The ENG with horizontal leads showed an absence of spontaneous or positional nystagmus. Caloric responses on the left were 74° Is and 56° Is following hot and cold stimulation. Right-sided calories were 41 ° Is after both hot and cold stimulation. The CT showed normal findings, including a moderately well-pneumatized mastoid (Fig IB). A diagnosis of cupulolithiasis was made, and after a long, careful discussion about various treatment options, the patient wished to pursue transmastoid posterior semicircular canal occlusion. The occlusion technique was modified from the original "puncture." A 2- to 3-mm posterior canal segment was blue-lined through 180° around the outer turn. The endosteum was opened with a small 90° hook, with care taken not to aspirate the inner ear fluids. Bone paste from the mastoidectomy was delivered into the opening in a gentle but firm fashion with the intention of compressing the membranous labyrinth while maintaining its integrity. A layer of bone wax plus a second layer of fascia stopped the perilymph leak. This patient's postoperative course was considerably more tolerable. There was no spontaneous vertigo or nystagmus throughout the postoperative period. Certain head movements such as sitting up or lying down continued to make her vertiginous for the first 5 or 6 days. A Hallpike test on the third postoperative day showed the same preoperative nystagmus but with much less intensity. She was now ambulating and was discharged on her fifth postoperative day. She continued to improve symptomatically, and by day 8 the Hallpike test showed a further reduction of the induced nystagmus intensity. The ENG showed absence of a spontaneous or gaze nystagmus. Caloric responses to hot and cold stimuli were now 98° Is and 48° Is on the left and 21° Is and 26° Is on the right. On follow-up 2 weeks later, she reported complete absence of vertigo despite provocative efforts. Her mild imbalance continued to improve on a daily basis. The results of the Hallpike maneuver were now completely negative, and the results on ENG were essentially unchanged from those of the previous study. She remains symptom-free after 9 months of follow-up. DISCUSSION
The preliminary results from these two patients suggest that posterior semicircular canal occlusion can relieve the symptoms associated with intractable BPPV, or what many refer to as cupulolithiasis. Hall et al " divided BPPV into fatigable and non fatigable types and suggested that free-floating particles caused the former and that particles fixed
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Parnes & McClure, Posterior Semicircular Canal Occlusion
----- SITE OF OCCWSION
Fig 2. Schematic representation of occluded posterior semicircular canal. Shaded area - closed fluid (endoIymph)- filled space between impermeable cupula and site of occlusion.
to the cupula caused the latter. It was suggested that a fatigable and nonfatigable classification could provide the diagnostic criteria separating BPPV that subsides spontaneously from cupulolithiasis. As both patients in this study had fatigable BPPV, one for 2 years and the other for 2 1/ 2 years, it seems more appropriate to classify BPPV on the basis of duration of symptoms. If symptoms persist unchanged for greater than 1 year, the BPPV is unlikely to resolve, and the diagnosis of cupulolithiasis is made. The patient becomes a potential candidate for posterior semicircular canal occlusion. Conventional theory explains the signs and symptoms of BPPV on the basis of endolymph flow, and in turn cupular deflection, when loose particles in the endolymph of the posterior semicircular canal move under the influence of gravity. Similarly with cupulolithiasis, a mass on the cupula can move under the influence of gravity and induce cupular deflection. In either case, cupular deflection implies endolymph displacement. However, with the semicircular canal occluded, a closed fluid-filled space is created between the site of occlusion and the cupula, as illustrated in Fig 2. Since fluid cannot be compressed or expanded, the closed fluid-filled space acts as a solid member, and the cupula becomes fixed. Singular neurectomy eliminates the resting discharge from the posterior canal, creating a static asymmetry" between the two posterior canals. In this situation, one would anticipate persistent vertigo along with rotatory/vertical spontaneous nystagmus with the patient at rest. Posterior canal occlu-
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sion does not disturb the resting discharge from the occluded canal, so one would not expect symptoms with the patient at rest, as demonstrated in the second patient. However, the first patient did develop a spontaneous nystagmus. We suspect that trauma from the canal "puncture" caused a labyrinthitis resulting in temporary canal paresis, and this would be supported by the reduced caloric response. The simultaneous reduction in caloric response on the opposite side is difficult to explain, but may represent some form of cerebellar clamp. '7 With both singular neurectomy and posterior canal occlusion, head movement produces a dynamic asymmetry. 16 One would expect symptoms from posterior canal stimulation, and this proved to be the case with both patients. The dynamic asymmetry appeared to adapt completely within a few weeks. We opted to change the occlusion technique in the second patient for three reasons. The first was to minimize the amount of canal trauma and reduce the degree of labyrinthitis. The second reason related to the anatomy of the mastoid. The mastoid in the second case was less pneumatized than in the first (Fig 1), and the posterior semicircular canal was sitting flush against the cerebellar plate. A technique was required that would avoid inadvertent breach of the posterior fossa dura during the canal puncture. The third reason was more theoretic, and related to future canal occlusions in normalhearing patients. We felt that drilling through endolymph and perilymph was likely to be more traumatic to the organ of Corti than drilling on otic capsule bone alone. The "compression" technique used for the second case proved to be just as effective as the original "puncture." The transmastoid approach provides easy access to the posterior semicircular canal for occlusion. In creating the occlusion, we stress the importance of using bone chips to promote new bone formation" leading to complete permanent occlusion of the canal. We have shown in two patients that posterior semicircular canal occlusion can relieve intractable BPPV (cupulolithiasis) and at the same time preserve lateral semicircular canal function. The effect of canal occlusion on hearing in the otherwise normal human ear is unknown. However, since animal studies':' indicate no deleterious effect on hearing, we feel that this procedure now should be given consideration in the treatment of the normal-hearing ear with BPPV.
REFERENCES 1. Nedzelski JM, Barber HO, McIlmoyl L. Diagnoses in a dizziness unit. J Otolaryngol 1986;15:101-4. 2. Barber HO, Leigh RJ. Benign (and not so benign) postural vertigo: diagnosis and treatment. In: Barber HO, Sharpe A, eds. Vestibular disorders. Boca Raton, Fla: CRC Press, 1988:215-32. 3. Longridge NS, Barber HO. Bilateral paroxysmal positioning nystagmus. J Otolaryngol 1978;7:395-400.
4. Baloh RW, Honrubia V, Jacobson K. Benign positional vertigo: clinical and oculographic features in 240 cases. Neurology 1987;37:371-8. 5. Baloh RW. Sakala S, Honrubia V. The mechanism of benign paroxysmal positional nystagmus. Adv Otorhinolaryngol 1979;25: 161-6. 6. Schuknecht HF, Ruby RRF. Cupulolithiasis. Adv Oto-
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rhinolaryngol 1973;20:434-43. 7. Katsarkas A, Outerbridge JS. Nystagmus of paroxysmal positional vertigo. Ann Otol Rhinol LaryngoI1983;92:146-50. 8. Harbert F. Benign paroxysmal positional vertigo. Arch Ophthalmol 1970;84:298-302. 9. Cohen B, Suzuki J, Bender MB. Nystagmus induced by electrical stimulation of ampullary nerves. Acta Otolaryngol (Stockh) 1965;60:422-36.
13. Money KE, Scott JW. Functions of separate sensory receptors of nonauditory labyrinth of the cat. Am J Physiol 1962; 202:1211-20. 14. Parnes LS, McClure JA. Effect on brainstem auditory evoked responses of posterior semicircular canal occlusion in guinea pigs. J OtolaryngoI1985;14:145-50. 15. Hall SF, Ruby RRF, McClure JA. The mechanics of benign paroxysmal vertigo. J Otolaryngol 1979;8:151-8.
10. Gacek RR. Transection of the posterior ampullary nerve for the relief of benign paroxysmal positional vertigo. Ann Otol Rhinol Laryngol 1974;83:596-605.
16. McClure JA, Lycett P. Vestibular asymmetry. Arch Otolaryngol 1983;109:682-7.
11. Silverstein H. Singular neurectomy: a treatment for benign positional vertigo. In: Brackmann DE, ed. Neurological surgery of the ear and skull base. New York: Raven Press, 1982:331-5.
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12. Ohmichi T, Rutka J, Hawke M. Histopathologic consequences of surgical approaches to the singular nerve. Laryngoscope 1989;99:963-70.
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THE DEAFNESS RESEARCH FOUNDATION 1991 RESEARCH GRANTS AVAILABLE The Deafness Research Foundation invites applications for 1991 grant support of new research that promises to advance our understanding of the causes, treatment, and prevention of deafness and related ear disorders. The grants will be awarded to tax-exempt institutions for projects that will begin January 1, 1991, with the principal investigator of each project a member of the staff or faculty of such institution. The grants do not exceed $15,000, and can be competitively renewed with the same limit for an additional 1 or 2 years. Applications are reviewed for scientific merit of the proposed investigations and for their direct or potential clinical importance. The deadline for first year applications is July 15, 1990, and for renewal applications is August 15, 1990. For full information on the grant program, and for the required application form, please write to Walter A. Petryshyn, MD, Medical Director, The Deafness Research Foundation, 9 East 38th Street, New York, NY 10016; (212) 684-6556.
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