56‐Year‐Old Male With Acute‐Onset Ataxia After Metronidazole Use and a Typical MRI Appearance

Metronidazole is commonly used for treatment of anaerobic bacteria and protozoal infections. Neurological side effects of metronidazole include peripheral neuropathy, headache, dizziness, syncope, vertigo, and confusion.1 Isolated cerebellar toxicity is a reported, but uncommon, manifestation of metronidazole therapy. Here, we report on a case of ataxia and cerebellar lesions after short-term use of metronidazole, which resolved rapidly after discontinuation of drug therapy, and review the literature on this rare condition. A 56-year-old male presented with complaints of progressive imbalance while walking for the last 4 days. He gave history of swaying side to side, but there was no history of limb incoordination. There was no history of fever, headaches, or other neurological deficit. Three months previously, he was diagnosed with megaloblastic anemia resulting from vitamin B12 defficiency. He was having long-standing history of vitiligo. He was taking vitamin B12 injections regularly. On examination, he had gait and truncal ataxia (see Video 1, Segment A). There was no evidence of peripheral neuropathy. MRI disclosed bilaterally symmetrical T2 and fluid-attenuated inversion recovery (FLAIR) hyperintensity in dentate nucleus and dorsal pons (Fig. 1). Hemogram, renal function tests, liver function tests, serum electrolytes, and vitamin B12 levels were within normal range. Further detailed history revealed metronidazole intake for the last few days. He was taking metronidazole per orally for loose motions prescribed by physician for the last 2 weeks. He was taking metronidazole 400 mg three times a day. A diagnosis of metronidazole-induced acute cerebellar ataxia was made in the presence of the clinical features on neuroimaging findings and temporal relationship with metronidazole use. After admission to the hospital, metronidazole was stopped. His ataxia recovered gradually over the next 7 days (see Video 1, Segment B). The patient was asymptomatic on follow-up after 1 month, but he declined repeat MRI. Cerebellar toxicity is a rare side effect reported in patients treated with metronidazole.2 Cerebellar toxicity tends to occur at cumulative doses ranging between 25 and 1,080 g.3 Our patient took a cumulative dose of 16.8 g only. The majority of patients present with symptoms of ataxia and dysarthria; our patient presented with isolated gait ataxia and no speech impairment. Brain MRI commonly demonstrates bilateral symmetric T2 hyperintense lesions in the cerebellar dentate nucleus and dorsal pons, medulla, midbrain, corpus callosum, and cerebral white matter.4 This patient had MRI changes restricted predominantly to cerebellar dentate nucleus and dorsal pons. After discontinuation of metronidazole therapy, clinical improvement is noted in all patients within 3 to 7 days. Our patient had near complete recovery of ataxia in 7 days. Metronidazole is a commonly used antibiotic; physicians need to be aware of this cerebellar toxicity, given that prompt withdrawal of the drug often leads to reversal of the clinical and radiological resolution of the abnormalities, but resolution may take a number of weeks.5 (1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript Preparation: A. Writing of the First Draft, B. Review and Critique. R.B.: 1A, 1C D.D.: 3A, 3C Funding Sources and Conflicts of Interest: The authors report no sources of funding and no conflicts of interest. Financial Disclosures for previous 12 months: The authors declare that there are no disclosures to report. A video accompanying this article is available in the supporting information here. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.