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We described a-44-year old male patient with Isaacs' syndrome occurring 8 months before the recurrence of malignant thymoma. Electrophysiological examination suggested that spontaneous muscle activities were generated at the distal terminals of the motor nerves. Double filtration plasmapheresis alleviated the symptoms of neuromyotonia for a short term. Administration of valproic acid had more prolonged effects lasting for 2 months until his death from relapsed thymoma. Our results support that autoimmune mechanisms, especially humoral factors, are playing an important role in the pathogenesis of Isaacs' syndrome and that anti-convulsants therapy is important.

A 24-year-old woman with SLE since the age of 12 developed sensory-motor peripheral neuropathy in 1990. Her sensory neuropathy was symmetrical in all limbs and distally dominant. Electrophysiological study showed marked reduction of motor and sensory conduction velocities. Sural nerve biopsy revealed vasculitis and axonopathy. Symptoms of neuropathy and nerve conduction velocities were improved by high dose steroid treatment. After one year she had a fever of unknown origin, and then presented limb myokymia with involuntary finger movement which was fine, irregular, and continuous. Needle EMG revealed myokymic discharge at dorsal interosseous and flexor pollicis brevis muscles. Because myokymia was increased by hyperventilation and suppressed by local anesthesia at the wrist, her myokymia was thought to originate in the peripheral nerve. This is the first case report of limb myokymia with finger involuntary movement caused by peripheral neuropathy due to SLE.

Myokymia is one of the involuntary movements, which is characterized by undulatory muscle spasm, similar to the worm's crawl. Sometimes muscle pain, itchy sensation, dysautonomia and other symptoms are associated with it. Cases showing normal neurological findings are rare. Myokymia is caused by various diseases, such as, multiple sclerosis, hypothyroidism, Guillan-Barre syndrome and so on. Generally myokymia is classified into two types, i.e. limb myokymia and facial myokymia according to the site. On the other hand, myokymia with hyperhidrosis is known as Issacs syndrome. There are many opinions about the pathogenesis and mechanism in the myoneural junction, peripheral nerve or spinal cord, however these are not established. Further investigation of myokymia is expected.

A 30-year-old male visited us with complaints of dizziness and diplopia of abrupt onset in September, 1988. Neurological studies demonstrated paroxysmal rotatory to-and-fro oscillations of the left eye. There has been the same clinical episode at 25 years of age, lasting approximately 6 months. The characteristics of his ocular involuntary movement with the mild IVth cranial nerve paresis were as follows: quick, nonrhythmic, initially counterclockwise-rolling, more prominent in moving the left eye to the lower medial side, persisting for 1-10 seconds and rapidly repeated oscillations. When oscillations were prominent, he complained of faintness in addition to double vision. Except for the ocular signs, other neurological and laboratory examinations including cerebrospinal fluid, brain MRI and brain stem auditory evoked response, failed to disclose the precise location and nature of the lesion. Abnormal ocular movement was fluctuating for 4 months and gradually disappeared without any medication. In conclusion, the faintness could be considered to result from a lesion of reticular activating system adjacent to the IVth cranial nerve nucleus and its rostral (excitatory or inhibitory) supranuclei, and it suggests that a responsible lesion of the abnormal ocular movement is located at a region of the dorsomedial midbrain.

The present report deals with an unique case of myokymia-hyperhidrosis syndrome. A 46-year-old man developed generalized relatively slow, undulating movement of the muscles, excessive sweating, muscle cramps and easy fatigability since three years ago. On admission, he had generalized myokymia, abnormal movements consisting of slow, undulating and worm-like muscular contractions. There was no muscle atrophy or weakness, or sensory deficits. Deep tendon reflexes were diminished and no Babinski sign or other pathological reflexes were present. Muscle tone was in normal range. Neither fasciculation nor myotonia was found. Laboratory examinations revealed elevation of BMR with normal thyroid function. The value of anti-Ach receptor antibody was below 0.6nmol/l. EMG recordings showed (1) continuous spontaneous repetitive discharges of NMU at a frequency of 30-50Hz, with duration of 1-2 seconds and amplitude of about 1 mV, were demonstrated at rest and the findings were consistent with myokymia, (2) waxing phenomenon was observed on repetitive peripheral nerve stimuli, which didn't improve by the tension test, and (3) high amplitude, long duration and polyphasic NMU, a sign of denervation, were observed on voluntary contraction. Muscle biopsy specimens from the left quadriceps showed a number of internal nuclei. On electron microscopy, clustered mitochondria and filamentous bodies were very often found in subsarcolemma. From these observations, damage to peripheral nerves, neuromuscular junctions and muscles may be responsible for the generalized myokymia in our patient.