An 18-year-old man with seizures from birth was followed in the Department of Clinical Neurological Sciences, University of Western Ontario, London, and was found to have developed a sensory neuropathy by 2 years of age following treatment with pyridoxine in doses up to 2000 mg/day. The initial seizure at birth responded to pyridoxine 150 mg IV, after treatment with diazepam had failed. A sister had died in status epilepticus at age 9 days and had not received pyridoxine. Complex febrile seizures from 1 to 4 years, followed by recurrent afebrile convulsions, and at 13 years, complex partial seizures continued despite pyridoxine 2000 mg/day, phenytoin, and phenobarbital. At 18 years, following the addition of carbamazepine, seizures were controlled, and pyridoxine was decreased to 100 mg daily. MRI showed left mesial temporal sclerosis. Nerve conduction studies at 2 years revealed absent sensory action potentials and normal motor conduction. Sural nerve biopsy showed severe, axonal, sensory neuropathy. At 18 years, vibration sense in the feet was absent, position sense was decreased in the toes, pain sensation was impaired to the midcalf and in the fingers, tendon reflexes were absent, and plantar responses were flexor. His gait was ataxic. Sural, peroneal and median sensory nerve action potentials were absent. The sensory neuronopathy diagnosed at 2 years had not progressed or remitted at 18 years. [1]

COMMENT. The authors explain the failure of pyridoxine to completely control the seizures in this patient by a combination of pyridoxine-dependent epilepsy with complex partial seizures due to mesial sclerosis. Unusually high doses of pyridoxine were prescribed in this patient. Doses as low as 50 mg/day have caused neuropathy when continued for months or years. Individual susceptibility is also a factor in the occurrence of this side effect.