We report a unique patient who had temporary
isoniazid-induced
myoclonic seizures. A 74-year-old man noticed
involuntary movements in the upper extremities when he received
isoniazid in pulmonary atypical mycobacteriosis late June 1996. Neurological examination revealed
myoclonic jerking in the upper limbs. Although
isoniazid treatment had been given to November 1996, the
myoclonic seizures were spontaneously ameliorated at 2 weeks following the onset. The second administration of
isoniazid was started for the exacerbation of pulmonary atypical mycobacteriosis in February 13, 1999. Immediately he developed
myoclonic seizures in the upper extremities. Neurological examination showed
myoclonic jerking in the upper extremities and
cerebellar ataxia in the lower extremities. These neurological deficits were naturally improved within a week. Brain MRI suggested multiple
lacunar infarction. EEG showed slow theta and sharp waves. Somatosensory evoked potential (SEP) revealed giant potentials. There was no renal or
liver dysfunction. Serum
vitamin B6 levels were decreased slightly. The metabolic studies of serum and cerebrospinal fluid
isoniazid concentrations demonstrated slow inactivation of this agent. After the end of
isoniazid treatment, EEG and SEP were normal. The results of these studies indicated that slow inactivator of
isoniazid and its epileptogenic effects might contribute to the pathogenesis of
myoclonic seizures in our patient.