Metronidazole-induced encephalopathy delayed diagnosis due to cerebellar infarction: A case report.

Rationale: Metronidazole is a 5-nitroimidazole antibiotic effective against anaerobic bacterial and parasitic infections. Long-term use may cause side effects in the central nervous system, although the occurrence of encephalopathy is rare.

Patient Concerns: A 73-year-old man was diagnosed with acute pyelonephritis and received antibiotic treatment. During the treatment, the patient complained of back pain. Lumbar spinal magnetic resonance imaging (MRI) revealed infective spondylitis, and metronidazole (1.5 g) was administered daily for approximately 160 days. The patient developed cognitive dysfunction and gait disorder after antibiotic treatment, and brain MRI showed acute infarction in both cerebellar lobes. Secondary prevention with antiplatelet and physiotherapy was prescribed; however, functional recovery was not achieved.

Diagnosis: After 1 month, a follow-up brain MRI showed high signal intensity and diffusion restriction in the corpus callosum on diffusion-weighted images and high signal intensity in the dentate nucleus on T2-weighted images. Therefore, metronidazole-induced encephalopathy was suspected.

Interventions: Metronidazole was discontinued, and ceftriaxone (2 g/day) was administered to manage the infective spondylitis.

Outcomes: One week after the discontinuation of the drug, the patient's cognition improved to the extent that communication was possible. Thus, even if other neurological deficits, such as cerebellar infarction, are found in patients with long-term disability, the possibility of metronidazole-induced encephalopathy should be considered when metronidazole is used for a long time.