occurrence of long tract signs in hypothyroidism [ 121, but no references were provided in that article and in several reviews this manifestation has not been commented on [ 1, 3, 151. However, Addison’s disease in association with spastic paraplegia is a well-recognized entity [6, 13, 181. Although a patient with a hypothalamic tumor and spastic paraplegia has been reported (Case 3 in [7]), pressure on the long tract was not excluded as a cause of the neurological deficit. Hypothalamic tumor seems unlikely in our patient in view of the normal contrast study of the area and her complete recovery, which has been maintained for five years. Although demyelinating disease with spontaneous recovery is a possibility, our patient’s age at onset of the condition as well as the long follow-up make this diagnosis remote. We conclude that hypothalamic disease causing hypothyroidism can result in spastic paraplegia that may be reversible with appropriate hormone therapy. The diagnosis of hypothyroidism should be considered in such neurological disorders of apparently unknown cause. Supported in part by US Public Health Service Grants AM-05166 (Training) and FR-0054.
References 1. Aita JA: Neurologic manifestations of endocrine diseases, in
2.
3. 4.
5.
6. 7.
8.
9. 10.
11.
Neurologic Manifestations of General Diseases. Springfield, IL, Charles C Thomas, 1964, pp 88-175 Costom B H , Grumbach MM, Kaplin SL: Effect of thyrotropin releasing factor o n serum thyroid stimulating hormone. An approach to distinguishing hypothalamic from pituitary forms of idiopathic hypopituitary dwarfism. J Clin invest 5 0 2 2 192225, 1971 Dale AD: Neurological problems in endocrine diseases. Med Clin North Am 56:1029-1039. 1072 Faglia G, Beck-Peccoz P, Ferrari C, et al: Plasma thyrotropin response to thyrotropin-releasing hormone in patients with pituitary and hypothalamic disorders. J Clin Endocrinol Metab 37:595-601, 1973 Hall R, Ormston BJ, Besser G M , et al: The thyrotropinreleasing hormone test in diseases of the pituitary and hypothalamus. Lancet 1:759-762, 1972 Harris-Jones J N , Nixon PGF: Familial Addison’s disease with spastic paraplegia J Clin Endocrinol Metab 15:739-744, 1955 Kahana L, Lebovitz H, Lusk W. e t al: Endocrine manifestations of intracranial extrasellar lesions. J Clin Endocrinol Metab 22:304-324. 1962 Lppe B, Wong RSL, Kaplan SA: Simultaneous assessment of growth hormone and ACTH reserve in children pretreated with diethylstilbestrol. J Clin Endocrinol Metab 33949-956, 1971 Mattingly D: A simple fluorimetric method for the estimation of free 1 1-hydroxycorticoids in human plasma. J Clin Pathol 15:374-379, 1062 Murphy BP. Jacham C: The determination of thyroxine by competitive protein-binding analysis employing an anionexchange resin and radiothyroxine. J Lab Clin Med 6 6 1 5 1 167, 1965 Nejad IF, Bollinger JA, Mitnick M, et al: Importance of T3
2. 3.
4. 15. 16.
17. 18.
secretion in altered states of thyroid function in the rat: cold exposure, subtotal thyroidectomy and hypophysectorny. Trans Assn Am Phys 85:295-308, 1072 Nickel SN, Frame B: Neurologic manifestations of myxedema. Neurology (Minncap) 8:511-517, 1958 Penman RWB: Addison’s disease in association with spastic paraplegia Br Med J 1:402, 1060 Peterson RE, Nokes G , Chen PS, e t al: Estrogens and adrenocortical function in man. J Clin Endocrinol Metab 20:495-514, 1960 Sanders V: Neurologic manifestations of myxedema. N Engl J Med 226:547-552, 599-603, 1962 Sterling K, Brenner MA: Free thyroxine in human serum: simplified measurement with the aid of magnesium precipitation. J Clin Invest 45:153-163, 1966 Turkington RW, Macindow JH: Hyperprolactinemia in sarcoidosis. Ann lntcrn Med 76:545-549, 1972 Warter J. Voegtlin R, Grappe JM: Myelomalacie Addisonienne. Sem H o p Paris 34:2930-2933, 1958
Late Components of Motor Unit Potentials in a Patient with Myoglobinuria Jackson B. Pickett,
MD
A 45-year-old woman had severe weakness, myoglo-
binuria, and elevated muscle enzyme levels in the serum after a flulike illness. Electromyography some four weeks later showed motor unit potentials with late components; these remained present on subsequent electromyographic examinations performed at approximately monthly intervals for the following year. The persistence of motor unit potentials with late components is taken to imply that the late components were caused either b y sprouts that failed to undergo myelination or, more likely, by ectopically innervated muscle fibers. Pickett JB: Late c o m p o n e n t s of m o t o r u n i t potentials i n a p a t i e n t with m y o d o b i n u r i a . A n n Neurol 3:461-464, 1978
Excitation of a single motor neuron leads to the generation of action potentials in all of the muscle fibers that it innervates. A motor unit potential is a compound potential representing the sum of these individual potentials. Its duration is governed by the scatter of the neuromuscular junctions innervated by its terminal branches. Accordingly, the duration relates to the width of the innervation zone and to differences in Accepted for publication Dec 8 , 1977. Address reprint requests to D r Pickett, Department o f Neurology. University of California, San Francisco, School of Medicine, San Francisco. C A 94143.
0364-5 134/78/0003-0520$01.00 @ 1978 by Jackson B. P i c k e t t
461
conduction time along the terminal axonal processes and the individual muscle fibers that they innervate. Late components of motor unit potentials [ 3 ] are small potentials separated from the main motor unit potential by 20 msec or more (Fig 1).They have been seen in progressive neurogenic disorders and progressive muscle diseases such as polymyositis and muscular dystrophy. A late component could occur 20 msec after the main potential if its pathway to the recording electrode included a 20 mm unmyelinated sprout conducting at about 1 d s e c . Collateral sprouts typically become myelinated and attain a near-normal diameter over two to three months [ 4 ] ,and the late component would then be expected to become incorporated into the main motor unit potential. A late component could also occur due to the presence of an ectopic end-plate separated from the innervation zone by 60 mm with a muscle fiber conduction velocity of 3 d s e c ; in such circumstances one would not expect the latency of the late component to change with sprout myelination. The present report describes apatient with an acute monophasic muscle disease in whom electromyography revealed motor unit potentials with late components. These late components persisted for at least
462 Annals of Neurology
Vol 3 N o 5 May 1978
twelve months, which suggests that they were due to ectopic innervation. A 45-year-old woman had severe weakness, myoglobinuria, and elevated muscle enzyme levels in the serum after a flulike illness. There was no clinical evidence of peripheral nerve involvement. She recovered completely in six months. Motor and sensory conduction studies and repcutive nerve stimulation before and after exercise were normal. Needle examination of the left tibialis anterior muscle revealed fibrillation (3 +) and an excess of small short motor unit potentials. The examination was repeated 13 days later (approximately 27 days after the onset of the illness), and on this occasion rwo motor units were seen to contain late compoF i g I. Two type.!of late component blocking. Motor unit potenti& from the tibialiJ anterior trigger a n oscilloscope sweep after a 5 msec delay and are photographed onfilm moving perpendicular to the sweep. In each halfofthefigure, the main body of the motor unit potential is 1dt and the late component is right. (Ltfr) D u a l blocking run be observed where both late components are absent on the thirdandsixth sweep from the bottom. (Right) On-off lute component blocking w i t h transition is shown. Late component amplitude varieJ greatly w i t h electrode position. (Culibrution:vertical bar, 50 pv Idt and 500 pv right; horizontal bar, 5 msec.)
d2
.
n
2 5
50-
.
I-
I-
2
40-
I
2
11
16
18
24
28 32
37
45
54
WEEKS AFTER ONSET OF MYOGLOBINURIA
Fig 2. L.ute components ufter myoglobinuria. Motor unit potentiuls were recorded in the left tibialis anterior w i t h a Disu 1.3L50 concentric needle electrode. Each .sample consisted of 20 potentirrls. Lute components were first seen 27 days after myoglobinuria, a time when pain prevented sampling 20 units. Mean intramuscular temperature was 34.8"C In the patient and35.0"C in the normulsubject.
nents. One of these potentials had a single late component that was absent in a random fashion 40V; of the time. Similar electromyographicfindings were obtained on subsequent examinations performed at approximately monthly intervals for up to o n e year (Fig 2). In view of the possibility that these late components had arisen from injury to the muscle by rcpcatcd needle examinations, a previously unsampled muscle (the right tibialis anterior) was examined eleven months after the onset of the disorder, but similar potentials with late components were found. Also, potentials with late components did not develop aftcr the same number of needle examinations in a normal subject who was studied with this possibility in mind. During the examinations performed at two and a half and seven months after the onset of the illness, blocking of two late components was seen to occur at the same time, dual blocking (Fig 1, left). A different type of blocking (Fig 1, right) was sccn eight and nine months after the onsct of the illness. At those times, a single late component was present in an on-off fashion for 30 or more consecutive impulses.
Discussion The patient had a monophasic muscle disease (myoglobinuria being indicative of extensive muscle fiber
destruction), due probably to a viral myositis. Profuse fibrillation was found during the first electromyographic examination some two weeks after the onset of the illness and could still be found as late as six months after onset, presumably resulting from muscle fiber segmentation [31. T h e persistence of late components in this patient with myglobinuria suggests that the late components were due to ectopic innervation, because the maturation of collateral nerve sprouts should have occurred well within the one-year follow-up [7]. Ectopic innervation could certainly have been induced by the muscle fiber fragmentation and regeneration that occur in myoglobinuria. Thus, after rat muscle fibers are destroyed by bupivacaine, regenerating muscle fibers can be reinnervated by a transplanted foreign nerve, by their native nerve, or by both nerves [5]. Statistical analysis does not reveal any decrease in late component latency during the one-year period of observation. There was n o significant difference in late component latency in the 9 samples as determined by one-way analysis of variance (F = 0.810; df = 8). Moreover, the correlation coefficient of the duration of motor unit potentials with late components to time from onset of illness was insignificant (r = -0.03 17) and was similar to the correlation coefficient of motor unit potential duration to the time from onsct in the normal sample (r = -0.0954). When late components were first seen 2 7 days after the onset of the disorder, one motor unit potential had a single late component that was absent in a random fashion on 40% of occasions. This type of blocking was not seen in later examinations. Single blocking of this sort has frequently been observed [3] and probably reflects the activity of immature synapses in which end-plate potentials are often below the threshold for exciting muscle fiber action potentials due to a reduction in a number of acetylcholine quanta that are released [2]. Blocking of two late components at the same t i m e - d u a l blocking-was seen during later electromyographic examinations [6]. In the illustrated example, blocking of both late components occurred 2 in 165 times with no single blocks. If dual blocking were the result of 2 single blocks occurring at the same time, the probability of a dual block would equal the product of the two single-block probabilities: = (Psnl) (PsB2).T h e expected number of single blocks would equal their probabilitics times the number of observations. If PUB is constant, then the minimal number of single blocks will occur when PsHl= PsR2= Since 1 8 single blocks would be expected and none were observed, dual blocking presumably either must have occurred along the nerve before it branched to supply the muscle fibers giving rise to the two late componcnts, or was caused by repetitive firing of a single muscle fiber.
6.
Case Report: Pickett: Late Components after Myoglobinuria 463
A different type of blocking (Fig 1, right) was seen eight and nine months after onset. Here, a single late component was present in an on-off fashion for 30 or more consecutive impulses. An analogous finding has been reported at regions of low conduction safety in single primary afferent fibers of the cat, with impulses undergoing alternating periods of block and conduction [I]. This raises the possibility that following the attack of myoglobinuria, a recently myelinated sprout acted as a region of low conduction safety, thereby giving rise to on-off blocking. Further studies may help resolve this point. I am grateful to Drs M. J. Aminoff, H. L. Fields, and D. A. Riley, of the University of California, San Francisco, for review of the manuscript and valuable suggestions.
References 1. Chung S-H, Raymond SA, Letwin JY: Mulaple meanings in
single visual units. Brain Behav Evol 3:72-101, 1970 2. Dennis MJ: Physiological properties of junctions berween nerve and muscle developing during salamander limb regeneration. J Physiol (Lond) 244:683-702, 1975 3. Desmedt JE, Borenstein S: Regeneration in Duchenne muscular dystrophy.
Electromyographic
evidence.
Arch
Neurol
33:642-650, 1976 4. Edds M V : Collateral nerve regeneration. Q Rev Biol 28:260276, 1953 5. Hall-Crams ECB: Hyperinnervation of muscle following treatment with bupivacaine. Anat Rec 184:420-421, 1976 6. Staberg E, 'Ihiele B: Transmission block in terminal nerve twigs: a single fibre electromyographic finding in man. J Neurol Neurosurg Psychiatry 35:52-59, 1972 7 . Trojaborg W: Prolonged conduction block with axonal degeneration. An electrophysiological study. J Neurol Neurosurg Psychiatry 40:50-57, 1977
Blue Rubber Bleb Nevus Syndrome with CNS Involvement and Thrombosis of a Vein of Galen Malformation E. A. Waybright, MD, J. B. Selhorst, MD, W. 1. Rosenblum, MD, and C. G. Suter, M D
A patient is described with the dermatological features of blue rubber bleb nevus syndrome (BRBNS), focal seizures, and lateralized neurological signs. CAT scan demonstrated a nonenhanced density in the region of the vein of Galen. Neuropathological examination showed that this density was a clot within a vein of Galen malformation. Hemangiomas that grossly resembled the skin lesions of BRBNS were seen on the cerebral surface. Many of these hemangiomas were thrombosed and overlay patchy zones of infarction. Numerous vascular malformations of varying histological types were also found within the brain and systemic organs. Bluish, compressible, often raised hemangiomas of the skin should alert physicians to the BRBNS and the potential for vascular malformations to occur within the brain as well as systemic organs. Diagnosis of BRBNS involving the brain may assist in interpretation of radiographic findings. T h e tendency of these malformations to thrombose may account for focal neurological deficits. Waybright EA, Selhorst JB, Rosenblum WI, et al: Blue rubber bleb nevus syndrome with CNS involvement and thrombosis of a vein of Galen malformation. Ann Neurol 3:464-467, 1978 In 1958 Bean [ 13 described a disorder with distinctive hemangiomas of the skin and gastrointestinal tract. He termed the condition the blue rubber bleb nevus syndrome (BRBNS). We wish to draw attention to brain involvement in BRBNS by describing a patient who presented with focal seizures, lateralized neurological signs, and bluish hemangiomas of the skin. In this patient computerized tomography (CAT scan) revealed a high density in the region of the vein of Galen. T h e nature of this high density and the cause of the neurological signs were not fully evident until pathological examination. From the Departments of Neurology and Pathology, Medical College of Virginia, Richmond, VA. Accepted for publication Dec 13, 1977. Address reprint requests to D r Selhorst, Box 698, Medical College of Virginia. L c h m o n d , VA 23298.
464 0364-5134/78/0003-0521$01.00 @ 1978 by E. A. Waybright
References 1. Aita JA: Neurologic manifestations of endocrine diseases, in
2.
3. 4.
5.
6. 7.
8.
9. 10.
11.
Neurologic Manifestations of General Diseases. Springfield, IL, Charles C Thomas, 1964, pp 88-175 Costom B H , Grumbach MM, Kaplin SL: Effect of thyrotropin releasing factor o n serum thyroid stimulating hormone. An approach to distinguishing hypothalamic from pituitary forms of idiopathic hypopituitary dwarfism. J Clin invest 5 0 2 2 192225, 1971 Dale AD: Neurological problems in endocrine diseases. Med Clin North Am 56:1029-1039. 1072 Faglia G, Beck-Peccoz P, Ferrari C, et al: Plasma thyrotropin response to thyrotropin-releasing hormone in patients with pituitary and hypothalamic disorders. J Clin Endocrinol Metab 37:595-601, 1973 Hall R, Ormston BJ, Besser G M , et al: The thyrotropinreleasing hormone test in diseases of the pituitary and hypothalamus. Lancet 1:759-762, 1972 Harris-Jones J N , Nixon PGF: Familial Addison’s disease with spastic paraplegia J Clin Endocrinol Metab 15:739-744, 1955 Kahana L, Lebovitz H, Lusk W. e t al: Endocrine manifestations of intracranial extrasellar lesions. J Clin Endocrinol Metab 22:304-324. 1962 Lppe B, Wong RSL, Kaplan SA: Simultaneous assessment of growth hormone and ACTH reserve in children pretreated with diethylstilbestrol. J Clin Endocrinol Metab 33949-956, 1971 Mattingly D: A simple fluorimetric method for the estimation of free 1 1-hydroxycorticoids in human plasma. J Clin Pathol 15:374-379, 1062 Murphy BP. Jacham C: The determination of thyroxine by competitive protein-binding analysis employing an anionexchange resin and radiothyroxine. J Lab Clin Med 6 6 1 5 1 167, 1965 Nejad IF, Bollinger JA, Mitnick M, et al: Importance of T3
2. 3.
4. 15. 16.
17. 18.
secretion in altered states of thyroid function in the rat: cold exposure, subtotal thyroidectomy and hypophysectorny. Trans Assn Am Phys 85:295-308, 1072 Nickel SN, Frame B: Neurologic manifestations of myxedema. Neurology (Minncap) 8:511-517, 1958 Penman RWB: Addison’s disease in association with spastic paraplegia Br Med J 1:402, 1060 Peterson RE, Nokes G , Chen PS, e t al: Estrogens and adrenocortical function in man. J Clin Endocrinol Metab 20:495-514, 1960 Sanders V: Neurologic manifestations of myxedema. N Engl J Med 226:547-552, 599-603, 1962 Sterling K, Brenner MA: Free thyroxine in human serum: simplified measurement with the aid of magnesium precipitation. J Clin Invest 45:153-163, 1966 Turkington RW, Macindow JH: Hyperprolactinemia in sarcoidosis. Ann lntcrn Med 76:545-549, 1972 Warter J. Voegtlin R, Grappe JM: Myelomalacie Addisonienne. Sem H o p Paris 34:2930-2933, 1958
Late Components of Motor Unit Potentials in a Patient with Myoglobinuria Jackson B. Pickett,
MD
A 45-year-old woman had severe weakness, myoglo-
binuria, and elevated muscle enzyme levels in the serum after a flulike illness. Electromyography some four weeks later showed motor unit potentials with late components; these remained present on subsequent electromyographic examinations performed at approximately monthly intervals for the following year. The persistence of motor unit potentials with late components is taken to imply that the late components were caused either b y sprouts that failed to undergo myelination or, more likely, by ectopically innervated muscle fibers. Pickett JB: Late c o m p o n e n t s of m o t o r u n i t potentials i n a p a t i e n t with m y o d o b i n u r i a . A n n Neurol 3:461-464, 1978
Excitation of a single motor neuron leads to the generation of action potentials in all of the muscle fibers that it innervates. A motor unit potential is a compound potential representing the sum of these individual potentials. Its duration is governed by the scatter of the neuromuscular junctions innervated by its terminal branches. Accordingly, the duration relates to the width of the innervation zone and to differences in Accepted for publication Dec 8 , 1977. Address reprint requests to D r Pickett, Department o f Neurology. University of California, San Francisco, School of Medicine, San Francisco. C A 94143.
0364-5 134/78/0003-0520$01.00 @ 1978 by Jackson B. P i c k e t t
461
conduction time along the terminal axonal processes and the individual muscle fibers that they innervate. Late components of motor unit potentials [ 3 ] are small potentials separated from the main motor unit potential by 20 msec or more (Fig 1).They have been seen in progressive neurogenic disorders and progressive muscle diseases such as polymyositis and muscular dystrophy. A late component could occur 20 msec after the main potential if its pathway to the recording electrode included a 20 mm unmyelinated sprout conducting at about 1 d s e c . Collateral sprouts typically become myelinated and attain a near-normal diameter over two to three months [ 4 ] ,and the late component would then be expected to become incorporated into the main motor unit potential. A late component could also occur due to the presence of an ectopic end-plate separated from the innervation zone by 60 mm with a muscle fiber conduction velocity of 3 d s e c ; in such circumstances one would not expect the latency of the late component to change with sprout myelination. The present report describes apatient with an acute monophasic muscle disease in whom electromyography revealed motor unit potentials with late components. These late components persisted for at least
462 Annals of Neurology
Vol 3 N o 5 May 1978
twelve months, which suggests that they were due to ectopic innervation. A 45-year-old woman had severe weakness, myoglobinuria, and elevated muscle enzyme levels in the serum after a flulike illness. There was no clinical evidence of peripheral nerve involvement. She recovered completely in six months. Motor and sensory conduction studies and repcutive nerve stimulation before and after exercise were normal. Needle examination of the left tibialis anterior muscle revealed fibrillation (3 +) and an excess of small short motor unit potentials. The examination was repeated 13 days later (approximately 27 days after the onset of the illness), and on this occasion rwo motor units were seen to contain late compoF i g I. Two type.!of late component blocking. Motor unit potenti& from the tibialiJ anterior trigger a n oscilloscope sweep after a 5 msec delay and are photographed onfilm moving perpendicular to the sweep. In each halfofthefigure, the main body of the motor unit potential is 1dt and the late component is right. (Ltfr) D u a l blocking run be observed where both late components are absent on the thirdandsixth sweep from the bottom. (Right) On-off lute component blocking w i t h transition is shown. Late component amplitude varieJ greatly w i t h electrode position. (Culibrution:vertical bar, 50 pv Idt and 500 pv right; horizontal bar, 5 msec.)
d2
.
n
2 5
50-
.
I-
I-
2
40-
I
2
11
16
18
24
28 32
37
45
54
WEEKS AFTER ONSET OF MYOGLOBINURIA
Fig 2. L.ute components ufter myoglobinuria. Motor unit potentiuls were recorded in the left tibialis anterior w i t h a Disu 1.3L50 concentric needle electrode. Each .sample consisted of 20 potentirrls. Lute components were first seen 27 days after myoglobinuria, a time when pain prevented sampling 20 units. Mean intramuscular temperature was 34.8"C In the patient and35.0"C in the normulsubject.
nents. One of these potentials had a single late component that was absent in a random fashion 40V; of the time. Similar electromyographicfindings were obtained on subsequent examinations performed at approximately monthly intervals for up to o n e year (Fig 2). In view of the possibility that these late components had arisen from injury to the muscle by rcpcatcd needle examinations, a previously unsampled muscle (the right tibialis anterior) was examined eleven months after the onset of the disorder, but similar potentials with late components were found. Also, potentials with late components did not develop aftcr the same number of needle examinations in a normal subject who was studied with this possibility in mind. During the examinations performed at two and a half and seven months after the onset of the illness, blocking of two late components was seen to occur at the same time, dual blocking (Fig 1, left). A different type of blocking (Fig 1, right) was sccn eight and nine months after the onsct of the illness. At those times, a single late component was present in an on-off fashion for 30 or more consecutive impulses.
Discussion The patient had a monophasic muscle disease (myoglobinuria being indicative of extensive muscle fiber
destruction), due probably to a viral myositis. Profuse fibrillation was found during the first electromyographic examination some two weeks after the onset of the illness and could still be found as late as six months after onset, presumably resulting from muscle fiber segmentation [31. T h e persistence of late components in this patient with myglobinuria suggests that the late components were due to ectopic innervation, because the maturation of collateral nerve sprouts should have occurred well within the one-year follow-up [7]. Ectopic innervation could certainly have been induced by the muscle fiber fragmentation and regeneration that occur in myoglobinuria. Thus, after rat muscle fibers are destroyed by bupivacaine, regenerating muscle fibers can be reinnervated by a transplanted foreign nerve, by their native nerve, or by both nerves [5]. Statistical analysis does not reveal any decrease in late component latency during the one-year period of observation. There was n o significant difference in late component latency in the 9 samples as determined by one-way analysis of variance (F = 0.810; df = 8). Moreover, the correlation coefficient of the duration of motor unit potentials with late components to time from onset of illness was insignificant (r = -0.03 17) and was similar to the correlation coefficient of motor unit potential duration to the time from onsct in the normal sample (r = -0.0954). When late components were first seen 2 7 days after the onset of the disorder, one motor unit potential had a single late component that was absent in a random fashion on 40% of occasions. This type of blocking was not seen in later examinations. Single blocking of this sort has frequently been observed [3] and probably reflects the activity of immature synapses in which end-plate potentials are often below the threshold for exciting muscle fiber action potentials due to a reduction in a number of acetylcholine quanta that are released [2]. Blocking of two late components at the same t i m e - d u a l blocking-was seen during later electromyographic examinations [6]. In the illustrated example, blocking of both late components occurred 2 in 165 times with no single blocks. If dual blocking were the result of 2 single blocks occurring at the same time, the probability of a dual block would equal the product of the two single-block probabilities: = (Psnl) (PsB2).T h e expected number of single blocks would equal their probabilitics times the number of observations. If PUB is constant, then the minimal number of single blocks will occur when PsHl= PsR2= Since 1 8 single blocks would be expected and none were observed, dual blocking presumably either must have occurred along the nerve before it branched to supply the muscle fibers giving rise to the two late componcnts, or was caused by repetitive firing of a single muscle fiber.
6.
Case Report: Pickett: Late Components after Myoglobinuria 463
A different type of blocking (Fig 1, right) was seen eight and nine months after onset. Here, a single late component was present in an on-off fashion for 30 or more consecutive impulses. An analogous finding has been reported at regions of low conduction safety in single primary afferent fibers of the cat, with impulses undergoing alternating periods of block and conduction [I]. This raises the possibility that following the attack of myoglobinuria, a recently myelinated sprout acted as a region of low conduction safety, thereby giving rise to on-off blocking. Further studies may help resolve this point. I am grateful to Drs M. J. Aminoff, H. L. Fields, and D. A. Riley, of the University of California, San Francisco, for review of the manuscript and valuable suggestions.
References 1. Chung S-H, Raymond SA, Letwin JY: Mulaple meanings in
single visual units. Brain Behav Evol 3:72-101, 1970 2. Dennis MJ: Physiological properties of junctions berween nerve and muscle developing during salamander limb regeneration. J Physiol (Lond) 244:683-702, 1975 3. Desmedt JE, Borenstein S: Regeneration in Duchenne muscular dystrophy.
Electromyographic
evidence.
Arch
Neurol
33:642-650, 1976 4. Edds M V : Collateral nerve regeneration. Q Rev Biol 28:260276, 1953 5. Hall-Crams ECB: Hyperinnervation of muscle following treatment with bupivacaine. Anat Rec 184:420-421, 1976 6. Staberg E, 'Ihiele B: Transmission block in terminal nerve twigs: a single fibre electromyographic finding in man. J Neurol Neurosurg Psychiatry 35:52-59, 1972 7 . Trojaborg W: Prolonged conduction block with axonal degeneration. An electrophysiological study. J Neurol Neurosurg Psychiatry 40:50-57, 1977
Blue Rubber Bleb Nevus Syndrome with CNS Involvement and Thrombosis of a Vein of Galen Malformation E. A. Waybright, MD, J. B. Selhorst, MD, W. 1. Rosenblum, MD, and C. G. Suter, M D
A patient is described with the dermatological features of blue rubber bleb nevus syndrome (BRBNS), focal seizures, and lateralized neurological signs. CAT scan demonstrated a nonenhanced density in the region of the vein of Galen. Neuropathological examination showed that this density was a clot within a vein of Galen malformation. Hemangiomas that grossly resembled the skin lesions of BRBNS were seen on the cerebral surface. Many of these hemangiomas were thrombosed and overlay patchy zones of infarction. Numerous vascular malformations of varying histological types were also found within the brain and systemic organs. Bluish, compressible, often raised hemangiomas of the skin should alert physicians to the BRBNS and the potential for vascular malformations to occur within the brain as well as systemic organs. Diagnosis of BRBNS involving the brain may assist in interpretation of radiographic findings. T h e tendency of these malformations to thrombose may account for focal neurological deficits. Waybright EA, Selhorst JB, Rosenblum WI, et al: Blue rubber bleb nevus syndrome with CNS involvement and thrombosis of a vein of Galen malformation. Ann Neurol 3:464-467, 1978 In 1958 Bean [ 13 described a disorder with distinctive hemangiomas of the skin and gastrointestinal tract. He termed the condition the blue rubber bleb nevus syndrome (BRBNS). We wish to draw attention to brain involvement in BRBNS by describing a patient who presented with focal seizures, lateralized neurological signs, and bluish hemangiomas of the skin. In this patient computerized tomography (CAT scan) revealed a high density in the region of the vein of Galen. T h e nature of this high density and the cause of the neurological signs were not fully evident until pathological examination. From the Departments of Neurology and Pathology, Medical College of Virginia, Richmond, VA. Accepted for publication Dec 13, 1977. Address reprint requests to D r Selhorst, Box 698, Medical College of Virginia. L c h m o n d , VA 23298.
464 0364-5134/78/0003-0521$01.00 @ 1978 by E. A. Waybright
