Metronidazole-induced encephalopathy: a systematic review

Metronidazole, a commonly used antibiotic drug, can cause adverse effects in the central nervous system termed metronidazole-induced encephalopathy, leading to diagnostic challenges. The condition is rare and a detailed description of its phenotype is lacking. In this systematic review we investigated the clinical features of metronidazole-induced encephalopathy to promote recognition and elaborate the description.

We performed a systematic literature search using PubMed.gov and hand searched the reference lists of included articles and other publications of interest. We included case series and single reports describing individual patients developing symptoms from the central nervous system in relation to metronidazole treatment. Data were extracted and analyzed descriptively.

We identified 779 publications of which 112 papers comprising 136 patients were included. Typical findings were dysarthria, gait instability, limb dyscoordination and altered mental status. Frequently, patients concomitantly presented with metronidazole-induced polyneuropathy. Liver disease was the most common pre-existing condition. MRI showed a characteristic pattern of reversible symmetrical hyperintense lesions on T2/FLAIR of the dentate nuclei in 90% of patients. Most patients improved significantly after discontinuation of metronidazole. Poor outcome was associated with severe comorbidity.

Metronidazole-induced encephalopathy should be considered in patients presenting with neurological symptoms in relation to newly initiated or prolonged metronidazole treatment. MRI changes are highly characteristic and specific. Patients with liver disease are at increased risk. Prognosis is good if recognized early.