Isolated involvement of corpus callosum in metronidazole-induced encephalopathy with concomitant peripheral neuropathy

Rationale: Metronidazole is widely used for treating infection of anaerobic bacteria and protozoa. Metronidazole is generally well tolerated, although metronidazole-associated peripheral neuropathy (PN) and metronidazole-induced encephalopathy (MIE) have been reported as rare side effects. The most common sites of MIE involve the bilateral dentate nucleus of the cerebellum. Herein, we present a rare case of MIE with isolated corpus callosum involvement, with concomitant metronidazole-associated PN. Patient concerns: A middle-aged man with ulcerative colitis was diagnosed with amoebic dysentery because of unhygienic eating. After receiving metronidazole (1.8 g/d, cumulative dose 61.2 g) for >1 month, he started to complain of continuous paresthesia of the limbs, and intermittent speech problems. Magnetic resonance imaging demonstrated an isolated lesion in the splenium of the corpus callosum. Diagnosis: A diagnosis of reversible splenial lesion syndrome and PN was made. Given the patient's medical history, MIE and metronidazole-associated PN were considered. Interventions: Metronidazole was stopped. Mecobalamine and vitamin B1 were used for adjuvant treatment. Outcomes: At 1.5 months after stopping metronidazole, his symptoms of numbness and hyperesthesia had not improved, although he felt less ill. The isolated lesion disappeared on follow-up magnetic resonance imaging. At 6 months later, the hyperesthesia symptoms remained, and he was unable to resume his previous work. Conclusions: Physicians should consider MIE in their differentials for reversible splenial lesion syndrome when encountering a patient with a history of metronidazole medication and symptoms of encephalopathy, especially with concomitant PN. Early identification of this metronidazole-related complication and early cessation of the drug are essential for treatment.