[MRI and SPECT findings in a case of metronidazole-induced reversible acute cerebellar ataxia].

A 69-year-old man was referred to our department because of acute onset nausea, vomiting, dysphagia, dysarthria and gait disturbance. He had a 50-day-history of amebic dysentery and had been treated with 1,500 mg metronidazole per day. Neurological examination revealed dysphagia, ataxic speech, ataxia of the left extremities and the trunk, and hyperactive deep tendon reflexes in all extremities. Sensory impairment of all modalities was apparent in a glove and stocking pattern, with mild paresthesia. Brain MRI showed T2 high signal lesions in the bilateral cerebellar dentate nuclei, more markedly on the left. On brain SPECT, obvious low blood perfusion was observed in the left cerebellar hemisphere. These findings well explained the ataxia of the left limbs. One month after discontinuing metronidazole, the cerebellar ataxia, dysphagia and MRI abnormalities completely cleared. Therefore, central nervous system damage induced by metronidazole is considered reversible. In spite of the presence of the MRI lesion in the right dentate nucleus, the patient had no ataxia of the right extremities and there was no hypoperfusion in the right cerebellar hemisphere. Thus, metronidazole does not appear to have a direct neurotoxic effect on the central nervous system. On the other hand, nerve conduction studies showed axonal polyneuropathy, which was not improved one month after cessation of the drug; thus metronidazole seems to exert more damage on peripheral nerves.