Continuous Muscle Fiber Activity

Isaacs, Journal of Neurology, Neurosurgery and Psychiatry (1961),176 describes the syndrome of continuous muscle fiber activity in two patients, marked by progressive muscle stiffness increased by voluntary muscle contractions and accompanied by fasciculation and weakness. Electromyography recorded a state of constant rapid dysrhythmic discharge of independent muscle fibers. The author defined the state as myotonic afterdischarge and likened it to post-tetanic afterdischarge. Neither patient showed response to numerous medications including quinidine, procainamide, cortisone, and atropine. Treatment with PHT (100 mg q.i.d.) resulted in dramatic improvement in symptoms and electromyographic changes both at rest and on voluntary effort. In a five-year follow-up,1183 the author reported that both patients were still well and had lost their abnormal stiffness. He noted that on the occasions when PHT had been stopped, the symptoms returned.

176. Isaacs, H., A syndrome of continuous muscle-fibre activity. J. Neurol. Neuro-surg. Psychiat., 24: 319-325, 1961.
1183. Isaacs, H., Continuous muscle fibre activity in an Indian male with additional evidence of terminal motor fiber abnormality, J. Neurol. Neurosurg. Psychiat., 30: 126-133, 1967.

Isaacs, Journal of Neurology, Neurosurgery and Psychiatry (1967),1183 reports on another patient with continuous muscle fiber activity, a twenty-year-old Indian male. The rapid effectiveness of PHT was apparent. (See also Ref. 2612.)

1183. Isaacs, H., Continuous muscle fibre activity in an Indian male with additional evidence of terminal motor fiber abnormality, J. Neurol. Neurosurg. Psychiat., 30: 126-133, 1967.
2612. Isaacs, H., Heffron, J. J., The syndrome of continuous muscle-fibre activity cured: further studies, J. Neurol. Neurosurg. Psychiatry, 37: MI-5, 1974.

Mertens and Zschocke, Klinische Wochenchrift (1965),251 report on three cases of neuromyotonia. Each patient had in common a continuous spastic contraction of the entire skeletal musculature, which did not even diminish while asleep or under anesthesia. Extensive electromyographic, histologic and other laboratory studies confirmed the electrophysiological abnormality. Quinine, quinidine, novocamid, steroids and diuretics had little or no effect. PHT and mephenytoin were tried. PHT was far more effective. With two injections of PHT, 250 mg, at sixty-minute intervals, it was possible to obtain significant elimination of spastic contractions and inhibition of movement in all muscle groups within two to four hours. The authors state that with oral PHT they were able to maintain this astonishing effect. A trial of discontinuing the PHT resulted in recurrence or rapid increase of the abnormal contraction.

251. Mertens, H. G. and Zschocke, S., Neuromyotonia, Klin. Wschr., 17: 917-925, 1965.

Levy, Wittig and Ferraz, Arquivo de Neuro Psiquiat (1965),1280describe a case of continuous muscle fiber activity at rest, diagnosed by electromyography. The condition showed some clinical improvement with corticosteroids, although this improvement was not reflected on the electromyogram. The authors report that PHT, 300 mg/day, markedly improved both the clinical picture and the abnormal electrical tracing in a few days.

1280. Levy, J. A., Wittig, E. O., Ferraz, E. C. F., Scleroderma associated with continuous electro-muscular activity, Arq. NeuroPsiquiat., 23: 283-287, 1965.

Hughes and Matthews, Journal of Neurology, Neurosurgery and Psychiatry (1969),1171 described a patient who for thirty-two years had suffered from a form of muscular rigidity clinically resembling myotonia but, in fact, identical with continuous muscle fiber activity. The patient was treated with 100 mg of PHT q.i.d., which produced immediate and continuing benefits. If he stopped taking PHT, for as short a period as twenty-four hours, the symptoms returned.

1171. Hughes, R. C. and Matthews, W. B., Pseudo-myotonia and myokymia, J. Neurol. Neurosurg. Psychiat., 32: 11-14, 1969.

Buscaino, Caruso, De Giacomo, Labianca and Ferrannini, Acta Neurologica (1970),881 describe a case of continuous muscle fiber activity syndrome (neuromyotonia). The man, age forty-five, had suffered for twenty years from stiffness of all muscles, widespread fasciculations, myokymia and excessive sweating. The muscular stiffness was present even during sleep. The nature of the electrical abnormality was documented on the electromyogram. This condition, present for twenty years, had been treated with a variety of substances without success. The authors state that the condition was dramatically resolved by the use of PHT or carbamazepine.

881. Buscaino, G. A., Labianca, O., Caruso, G., De Giacomo, P., and Ferrannini, E., Electromyographic and muscular histoenzymatic findings in a patient with continuous muscular activity syndrome (“Neuromyotonia”), Acta Neurol (Naples), 25: 206-224, 1970.

Wallis, Van Poznak and Plum, Archives of Neurology (1970),1658 report on two cases involving generalized muscular stiffness, fasciculations and myokymia of peripheral nerve origin. Electomyographic and other laboratory findings were consistent with the clinical diagnosis. In one case the authors state PHT, 100 mg t.i.d., provided dramatic relief. In the other case it was not found effective. In the successful case, when PHT was discontinued, within three days, all pretreatment symptoms returned. Prompt relief recurred with the reinstitution of PHT.

1658. Wallis, W. E., Van Poznak, A., and Plum, F., Generalized muscular stiffness, fasciculations, and myokymia of peripheral nerve origin, Arch. Neurol., 22: 430-439, 1970.

Welch, Appenzeller and Bicknell, Neurology (1972),1676 report a case of peripheral neuropathy with myokymia, sustained muscular contraction and continuous motor unit activity in twenty-two-year-old female. The patient was tried with quinine for one month without success. The patient was then given PHT, 300 mg/day, with almost immediate remission of symptoms. This remission continued with daily PHT.

1676. Welch, L. K., Appenzeller, O., and Bicknell, J. M., Peripheral neuropathy with myokymia, sustained muscular contraction, and continuous motor unit activity, Neurology, 22: 161169, 1972.

Kostov, Tachev and Nastev, Zhurnal Nevropatologii i Psikhiatrii imeni S.S. Korsakova (1973),1231 report on a patient with pseudomyotonia, (Isaacs’ syndrome) characterized by hypertonia of the distal extremities. Spontaneous electromyographic activity was present at rest, and did not disappear even after novocaine blockade of the peripheral nerve. PHT and carbamazepine each had favorable therapeutic effect. Withdrawal of the medications resulted in return of the disorder.

1231. Kostov, K. G., Tachev, A. M. and Nastev, G. T., The problem of pseudomyotonia (Isaac’s syndrome), Zh. Neuropatol. Psikhiatr. Korsakov, 73: 825-829, 1973.

Levinson, Canalis and Kaplan, Archives of Otolaryngology (1976),1954 reported an unusual case of continuous muscle activity complicated by airway obstruction secondary to laryngeal spasm. Treatment with PHT, 300 mg/day, resulted in rapid improvement of the peripheral symptoms and the laryngeal spasms.

1954. Levinson, S., Canalis, R. F. and Kaplan, H. J., Laryngeal spasm complicating pseudomyotonia, Arch. Otolaryngol., 102: 185-7, 1976.

Irani, Purohit and Wadia, Acta Neurologica Scandinavica (1977),1907 reported prompt and remarkable improvement upon administration of PHT in three of four patients with continuous muscle fiber activity.

1907. Irani, P. F., Purohit, A. V., and Wadia, N. H., The syndrome of continuous muscle fiber activity, Acta Neurol. Scand., 55:273-88,1977.

Lutschg, Jerusalem, Ludin, Vassella and Mumenthaler, Archives of Neurology (1978),1970 reported the successful treatment with PHT of a seven-year-old boy who had suffered for two years with the syndrome of continuous muscle fiber activity.

1970. Lutschg, J., Jerusalem, F., Ludin, H. P., Vasselia, F. and Mumenthaler, M., The syndrome of ‘continuous muscle fiber activity,’ Arch. Neurol, 35: 198-205, 1978.

Jackson, Satya-Murti, Davis and Drachman, Neurology (1979),1910 report on a case of Isaacs’ syndrome with laryngeal involvement, confirmed by clinical, pharmacologic and electrophysiologic findings. The patient responded well to treatment with a combination of PHT and carbamazepine.

1910. Jackson, D. L., Satya-Murti, S., Davis, L. and Drachman, D. B., Isaacs syndrome with laryngeal involvement: an unusual presentation of myokymia, Neurology, 29: 1612-5, 1979.

Lubliln, Tsairis, Streletz, Chambers, Riker, VanPoznak and Duckett, Journal of Neurology, Neurosurgery and Psychiatry (1979),1967 report two cases of continuous motor activity with impaired muscular relaxation. EMG showed continuous motor activity at rest. Treatment with PHT, 500-700 mg/day, resulted in marked diminution in myokymia and continuous motor activity. Clinical improvement persisted in two-year follow-up.

1967. Lublin, F. D., Tsairis, P., Streletz, L. J., Chambers, R. A., Riker, W. F., Van Poznak, A. and Duckett, S. W., Myokyrnia and impaired muscular relaxation with continuous motor unit activity, J. Neurol. Neurosurg. Psychiatry, 42: 557-62, 1979.

Reeback, Benton, Swash, Schwartz, British Medical Journal (1979),2040 report a patient treated for rheumatoid arthritis with penicillamine who developed muscle contractions and weakness suggesting neuromyotonia. EMG showed continuous motor firing at rest. The patient was treated with PHT with marked improvement in three days, which was confirmed by EMG studies six weeks later.

2040. Reeback, J., Benton, S., Swash, M. and Schwartz, M. S., Penicillamine-induced neuromyotonia, Br. Med. J., 1464-5, 1979.

Grassa, Figa-Talamanca, LoRusso, Giacanelli and Pontesilli, Italian Journal of Neurological Science (1981),2553 report a thirty-four-year-old woman with diffuse muscle contractions and other symptoms of continuous muscle fiber activity syndrome, confirmed by EMG. With oral PHT, 400 mg/day, improvement, which included cessation of the painful muscle spasms and excessive sweating, occurred. EMG, nine months later, showed almost complete disappearance of the abnormal activity.

2553. Grassa, C., Figa-Talamanca, L., LoRusso, F., Giacanelli, M., Pontesilli, B., Syndrome of continuous muscle fiber activity, Ital. J. Neurol. Sci., 4: 415-8, 1981.

Vasilescu and Florescu, Journal of Neurology (1982),3047 report a case of a male alcoholic who developed continuous muscle fiber activity. Electrophysiologic studies and muscle biopsy confirmed mixed sensorimotor polyneuropathy. PHT, 400 mg/day, was started and the clinical symptoms and EMG activity at rest disappeared within two days. This result persisted at follow-up six months later.

3047. Vasilescu, C., Florescu, A., Peripheral neuropathy with a syndrome of continuous motor unit activity, J. Neurol., 226: 275-82, 1982.

Maria and Pisanelli, Rivista di Neurologia (1983),2763 report a fifty-three-year-old male patient with neuromyotonia (Isaacs’ syndrome), who had been treated unsuccessfully with dopamine and benzodiazepines. Carbamazepine was tried with partial success. Treatment with PHT, 600 mg/day, resulted in remarkable improvement. When PHT was discontinued, the symptoms reappeared.

2763. Maria, G., Pisanelli, S., A case of neuromyotonia considerations of pathogenesis, Riv. Neurot., 53:400-09, 1983.

Zisfein, Sivak, Aron and Bender, Archives of Neurology (1983),3100 report a sixteen-year-old boy with severe episodic muscle cramps and generalized myokymia (Isaacs’ syndrome), associated gastrocnemius hypertrophy and ankle areflexia. The patient was treated with PHT, 300 mg/day, with total relief of cramps, marked decrease in myokymia and return of ankle reflexes. There was marked reduction in the muscle hypertrophy after three months.

3100. Zisfein, J., Sivak, M., Aron, A. M., Bender, A. N., Isaac’s syndrome with muscle hypertrophy reversed by phenytoin therapy, Arch. Neurol., 40: 241-2, 1983.

Brown, Archives of Physical Medicine and Rehabilitation (1984),2363 reports a twenty-year-old male patient with myokymia in all four extremities, hyporeflexia and hypertrophy of thenar musculature, who resented with cramping pain in both thighs and difficulty releasing grip. EMG revealed continuous motor unit activity at rest. The patient was treated with PHT and showed almost complete resolution of symptoms within twenty-four hours. The author states that rapid response to PHT, in conjunction with clinical and EMG findings, are diagnostic of Isaacs’ syndrome.

2363. Brown, T. J., Isaacs syndrome, Arch. Phys. Med. Rehabil., 65(l): 27-9, 1984.

See also Refs. 836, 1549, 1758, 2016, 2124, 2146, 2147, 2298, 2302, 2312, 2397, 2407, 2409, 2448, 2456, 2572, 2612, 2683, 2692, 2780, 2850, 2920, 3003, 3043, 3057.

836. Black, J. T., Garcia-Mullin, R., Good, E., and Brown, S., Muscle rigidity in a newborn due to continuous peripheral nerve hyperactivity, Arch. Neurol., 27: 413-425, 1972.
1549. Sigwaid, J., Raverdy, P., Fardeau, M., Gremy, F., Mace de Lepinay, A., Bouttier, D., and Danic, Mme., Pseudomyotonia, Rev. Neurol., II 5: 1003-1014, 1966.
1758. Broser, F., Ditzen, G. and Friedrich, K., Complementary electro-physiological findings in a case of neuromytonia, Nervenarzt, 46: 100-4, 1975.
2016. Pendefunda, G., Oprisan, C., Ciobanu, M. and Cozma, V., Clinico-electromyographic considerations on a case of neuro myotonia, Rev. Rouin. Med. (Neurot. Psychiatr.), 13(4): 237-45, 1975.
2124. Wolter, M. and Brauer, D., Neuromyotonia syndrome, Foruchr. Neural. Psychial., 45: 98-105, 1977.
2146. Ashizawa, T., Butler, I.J., Harati, Y. and Marshall, R.N. Autosomat dominant form of continuous motor neuron discharge, Neurology, 31(2): 59, 1981.
2147. Askanas, V., Engel, W.K., Berginer, V.M., Odenwald, W.F. and Galdi, A., Lysosomal abnormalities in cultured Schwann cells from a patient with peripheral neuropathy and continuous muscle fiber activity, Ann. Neurol., 10: 238-42, 1981.
2298. Ashizawa, T., Butler, 1. J., Harati, Y., Ftoongta, S. M., A dominantly inherited syndrome with continuous motor neuron discharges, Ann. Neural., 13: 285-90, 1983.
2302. Bady, B., Girard, P. F., Jallade, S., Gaillard, L., A case of pseudomyotonia cured by carbamazepine, Rev. Neural., 120: 277-86, 1969.
2312. Barron, S. A., Heffner, B. R., Continuous muscle fiber activity a case with unusual clinical features, Arch. Neurol., 36: 520-1, 1979.
2397. Coers, C., Telerman-Toppet, N., Durdu, J., Neurogenic benign fasciculations, pseudomyotonia and pseudotetany: A disease in search of a name, Arch. Neurol. 38: 282-7, 1981.
2407. Cordonnier, M., Delwaide, P. J., Malignant and benign fasciculations. Apropos of a case of neuromyotonia, Rev. Med. Liege., 34: 839-45, 1979.

2409. Cotrufo, R., Di forio, G., Arnmendola, A., Bravaccio, F., Continuous muscle fiber activity associated with denervation atrophy, Eur, Neural., 21: 375-9, 1982.
2448. Den Hartog Jager, W. A., Hootsmans, W. J., Isaacs’ Disease (continuous muscle fiber activity), Ned. Tijdschr. Geneeskd., 122: 1917-20, 1978.
2456. Ding-Cuo, S., Investigation in electrophysiology of neuromyotonia, Electroencephalogr. Clin. Neurophysiol., 56(3): S70, 1983.
2572. Harik, S. I., Baraka, A. S., Tomeh, C. J., Mire Salmari, Kronfulk, Z., Afifi, A. K., Autonomous peripheral nerve activity causing generalized muscle stiffness and fasciculations: report of a case with physiological, pharmacological, and morphological observations, Johns Hopkins Med. J., 139: 60, 1976.
2612. Isaacs, H., Heffron, J. J., The syndrome of continuous muscle-fibre activity cured: further studies, J. Neurol. Neurosurg. Psychiatry, 37: MI-5, 1974.
2683. Kwiecinski, H., The antimyotonic effect of diphenylhydantoin, Eur. J. Clin. Invest., 14: 37, 1984.
2692. Laterza, A., Paolella, P., Valassi, F., Myotonia-like deforming stiffness (a new myo-oculo-skeletal disease sensitive to diphenylhydantoin, Rev. Otoneuroophtalmol., 42 (1); 5170, 1967.
2780. McGuire, S. A., Tomasovic, J. J., Ackerman, N., Hereditary continuous muscle fiber activity, Arch. Neurol., 41: 395-6, 1984.
2850. Partanen, V. S., Soininen, H., Saksa, M., Riekkinen, P., Electromyographic and nerve conduction findings in a patient with neurornyotonia, normocalcemic tetany and small cell lung cancer, Acta Neurol. Scand., 61: 216-26, 1980.
2920. Sakai, T., Hosokawa, S., Shibasaki, H., Goto, I., Kuroiwa, Y., Sonoda, H., Murai, Y., Syndrome of continuous muscle-fiber activity: increased CSF GABA and effect of dantrolene, Neurology, 33: 495-8, 1983.
3003. Tang, X., Isaacs syndrome: report of a Chinese case with clinical and electrophysiologic study, China Med., Abstr., 2(3): 183, 1985.
3043. Valli, G., Barbieri, S., Cappa, S., Pellegrini, G., Searlato, G., Syndromes of abnormal muscular activity: overlap between continuous muscle fiber activity and the stiff man syndrome, J. Neural. Neurosurg. Psychiatry, 46: 241-7, 1983.
3057. Walsh, J. C., Neuromyotonia: an unusual presentation of intrathoracic malignancy, J. Neural. Neurosurg. Psychiatr., 39: 1086-91, 1976.

Baruah,, Neurology (1988), 3195 describes the regional infusion of phenytoin (diphenylhydantoin) (RID) in motor-unit hyperexcitable states (MUHS) in three patients with neurotonia, three with continuous muscle fiber activity syndromes, two with normocalcemic tetany and three with myokymia. RID was performed in the EMG laboratory with continuous EMG monitoring of the MUHS. PHT (300 mg mixed in 15 cc of normal saline) was infused in the distal forearm vein at a rate of 50 mg/min. Eight patients showed complete or marked disappearance of abnormal activity within 5-10 minutes of the start of the PHT infusion. Subsequent oral PHT therapy was successful in controlling symptoms and signs of their abnormal muscle activity in all of these patients. Three patients, one each with neurotonia, continuous muscle fiber activity, and myokymia, responded to neither RID nor oral PHT.

3195. Baruah, J.K., Regional infusion of diphenylhydantoin (RID) in motor unit hyperexcitable states (MUHS), Neurology, 38(Sup 1): 308, 1988.

Kurtzke, Lange, Trojaborg, Papadimitrou, Mills, Newsom-Davis and Rowland, Annals of Neurology (1989), 3196 studied a patient with no visible muscle twitching, but with other manifestations of Isaacs' syndrome. Plasmapheresis and combined prednisone-azathioprine therapy were ineffective. Intravenous phenytoin therapy abolished the impaired relaxation after muscle contraction (pseudomyotonia); Trousseau's sign; and the spontaneous electromyographic (EMG) high-frequency discharges seen in this patient. Ischemia-induced EMG activity was also delayed and shorter in duration with phenytoin.

3196. Kurtzke, R., Lange, D.J., Trojaborg, W., Papadimitrou, A., Mills, K., Nresome-Davis, J., Rowland, L.P., Isaacs syndrome without clinical fasciculation, Ann. Neurol., 26(1): 186, 1989.

Oda, Fukushima, Shibasaki and Ohnishi, Annals of Neurology (1989), 3197 report a case of Isaacs' syndrome with Trousseau's phenomenon. The patient, a thirty-three year-old male, presented with a two-year history of prominent, somewhat stiff muscles, intermittent myokymia in the thenar and calf muscles during waking, as well as sleep, absent deep tendon reflexes, and glove-and-stocking paresthesias in his extremities. He evidenced remarkable difficulty in relaxing after a forceful grasp and in opening his eyes after strenuous closure. The respiratory and bulbar muscles were affected, and he found it difficult to take a deep breath. Myokymia, pseudomyotonia (difficulty relaxing after forceful contraction), and ischemia-induced carpal spasm (Trousseau's phenomenon) were not abolished by nerve block distal to the cuff or by intravenous infusion of calcium. Inhalation of oxygen suppressed the pseudomyotonia and Trousseau's phenomenon, but his myokymia persisted. Administration of phenytoin (300 mg/day) completely abolished all types of abnormal discharges and his glove-and-stocking-type paresthesias in three days. There was no change in his deep tendon reflexes.

3197. Oda, K., Fukushima, N., Shibasaki, H., Ohnishi, A., Hypoxia-sensitive hyperexcitability of the intramuscular nerve axons in Isaacs' syndrome, Ann Neurol, 25: 140-145, 1989.

Hahn, Parkes, Bolton and Steward, Journal of Neurosurgical Psychiatry (1991), 3198 observed a case of two siblings with neuromyotonia or delayed muscle relaxation after voluntary contraction who experienced cramping and difficulty with muscle relaxation. Upon administration of PHT (300 mg/day), their neuromyotonia improved in a dose-dependent fashion. Abnormal spontaneous discharge from resting muscle was also significantly reduced.

3198. Hahn, A.F., Parkes, A.W., Bolton, C.F., Stewart, S.A., Neuromyotonia in hereditary motor neuropathy, J. Neurol. Neurosurg. Psychiatry, 54: 230-235, 1991.

Chang, Wu, Chen and Lu, Journal of Formosan Medical Association (1993), 3199 present a case report of an 18-year-old man who, one month before admission, experienced the acute onset of involuntary generalized contractions of the muscles. The involuntary cramps caused a dystonic posture of his neck and limbs. The patient walked slowly due to pain and stiffness in his legs, and he had fallen twice. Opisthotonos was noted when the cramps were exacerbated. The cramps were painful and sensitive to movements, causing the patient to limit body movement. On examination, external stimulation, such as a pinprick or a loud noise, induced or aggravated the cramps. The contractions of the muscles were observed to persist during sleep. No other neurological abnormalities were noted. Electromyography (EMG) showed spontaneous continuous muscle fiber activity that diminished dramatically after intravenous phenytoin (100 mg), but not diazepam (10 mg). Therapeutic trials with baclofen (40 mg/day) and diazepam (40 mg/day) for one week failed to eliminate the painful cramps. Within three days of treatment with oral phenytoin (300 mg/day), the cramps disappeared dramatically. This dosage was maintained for six months and then reduced to 200 mg/day without recurrence of the cramps.

3199. Chang, Y.J., Wu, C.L., Chen, R.S., Lu, C.S., Case of Isaacs syndrome successfully treated with phenytoin, Taiwan I. Hsueh. Hui. Tsa. Chih., 92(11): 1010-2, 1993.

De Oliveira and Levy-Reis, Arquivos de Neuro-Psiquiatria (1994), 3200 report a 16-year-old male patient, who, when originally examined, had a four-month history of muscle stiffness associated with difficulty speaking. Electromyography (EMG) revealed continuous motor activity that was unaffected by peripheral nerve block or general anesthesia, but was abolished by curare. The patient was treated with phenytoin (100 mg t.i.d.) with marked clinical improvement. When seen eleven years later, he had discontinued his phenytoin treatment, and his physical exam and EMG were the same as before treatment. Upon resuming phenytoin, his condition improved, and his EMG showed marked depression of the abnormal motor activity at rest.

3200. De Oliveira, J.T., Levy-Reis, I., Syndrome of continuous muscle fiber activity, Arq. Neuropsiquiatr, S2(1): 96-99, 1994.

Jamieson and Katirji, Muscle and Nerve (1994), 3201 present an analysis of seventy-five cases of idiopathic generalized myokymia (IGM) and review the published literature. Their analysis includes clinical characteristics, presenting symptoms, electrophysiology, results of muscle biopsies, pathogenesis, diagnosis and treatment. According to this analysis, "…approximately 70% of patients obtained complete relief of symptoms with either carbamazepine or phenytoin. Neither treatment worked in 12% of patients and neither treatment was tried in 16%. Carbamazepine was effective in eight cases where phenytoin was not, while phenytoin was effective in one case where carbamazepine was not." They make the point that, on occasion, treatment with both drugs may produce a response where neither alone is effective.

3201. Jamieson, P.W., Katirji, M.B., Idiopathic generalized myokymia, Muscle Nerve, 17(1): 42-51, 1994.

Perini, Ghezzi, Basso and Montanini, Italian Journal of Neurosurgical Sciences (1994), 3202 report a 51-year-old man who, over a four-year period, developed generalized weakness, dysarthria and difficulty in mastication associated with perioral paresthesias. Prior to the authors' report, a diagnosis of myasthenia gravis was made. After the removal of a large lymphoepithelial thymoma, the patient's symptoms worsened. When this patient was examined by the authors, in addition to an electromyographic pattern of continuous muscle fiber activity at rest, there was neurophysiological evidence of peripheral nervous system involvement. Myasthenic symptoms were absent. Following the administration of phenytoin (150 mg daily), the patient improved slightly. Three months after the dose was increased to 200 mg daily, the authors observed clear improvement in facial grimacing, and his myokymic discharges were less evident on EMG, their frequency being reduced by up to 70% and their duration, from 100-150 msec to 30-50 msec.

3202. Perini, M., Ghezzi, A., Basso, P.F., Montanini, R., Association of neuromyotonia with peripheral neuropathy, myasthenia gravis and thymoma: a case report, Ital. J. Neurol. Sci., 15(6): 307-10, 1994.

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