Neuromyotonia with neuropathy and muscle hypertrophy: association or cause?

Continuous muscle fibre activity in a patient with demyelinating neuropathy is rare. We report an 18 year old boy who presented with walking difficulty and continuous rippling in muscles of upper and lower limbs. He had dysarthric speech, hypertrophied arm and calf muscles with normal power, tone, reflexes and sensations. Myokymic discharges were seen in deltoid, biceps, quadriceps and calf muscles. His blood counts, chemistry, thyroid profile, DNA, Rh factor were normal and CPK was raised. CSF showed protein 50 mg/dl and 4 lymphocyte/mm3. Nerve conduction study revealed conduction block and absence of peroneal F wave. EMG showed neuromyotonic discharges which disappeared on regional neuromuscular blocker but not on nerve block or general anaesthesia. He responded partially to prednisolone. Acquired demyelinating neuropathy may result in neuromyotonia and muscle hypertrophy which may partially respond to prednisolone.