Metronidazole-Induced Encephalopathy in a Patient With Hepatitis B Cirrhosis During Treatment for Intra-abdominal Abscess

Metronidazole-induced encephalopathy is an uncommon but potentially reversible neurotoxicity characterized by symmetric dentate-nucleus hyperintensities on magnetic resonance imaging. Reduced drug clearance in cirrhosis may lower the toxicity threshold. We report a 72-year-old man with hepatitis B virus-related cirrhosis and hepatocellular carcinoma who underwent right hemicolectomy for bowel perforation due to peritoneal dissemination and subsequently developed recurrent intra-abdominal/retroperitoneal abscesses, with <i>Bacteroides thetaiotaomicron</i> isolated from drainage. Metronidazole 1,500 mg/day was initiated (day 0), briefly substituted with an alternative agent because the patient experienced nausea, and then reintroduced, after which the patient developed dizziness followed by dysarthria and cerebellar ataxia. Brain magnetic resonance imaging on day 63 revealed symmetric T2-weighted and fluid-attenuated inversion recovery hyperintensities in both dentate nuclei consistent with metronidazole-induced encephalopathy. Discontinuation of metronidazole resulted in a gradual clinical improvement, and follow-up magnetic resonance imaging on day 92 showed complete resolution, with a cumulative dose of 76.5 g. This case highlights the occurrence of metronidazole-induced encephalopathy at a sub-100-g exposure in cirrhosis. Thus, new cerebellar signs during therapy should prompt immediate withdrawal, early magnetic resonance imaging, and avoidance of re-exposure.