MR Imaging of Metronidazole-Induced Encephalopathy: Lesion Distribution and Diffusion-Weighted Imaging Findings

TLDR

MR imaging features of metronidazole‑induced encephalopathy remain incompletely defined. This study aimed to map the topographic distribution of lesions and characterize diffusion‑weighted imaging findings in MIE. The authors retrospectively reviewed initial MR scans (n = 7, including DWI in 5) and follow‑up scans (n = 4) after drug cessation, assessing lesion locations, DWI signal intensities, and ADC values. Bilateral symmetric T2 hyperintense lesions were found in the cerebellar dentate nucleus, midbrain, dorsal pons, medulla, corpus callosum, and cerebral white matter; DWI showed isointensity or hyperintensity with reduced ADC only in corpus callosum lesions, and all lesions resolved on follow‑up except one corpus callosum lesion, indicating vasogenic edema predominates while cytotoxic edema is limited to the corpus callosum.

Abstract

<b>BACKGROUND AND PURPOSE:</b> MR imaging features of metronidazole-induced encephalopathy (MIE) have not been fully established. This study was undertaken to determine the topographic distributions and diffusion-weighted imaging (DWI) findings of MIE. <b>MATERIALS AND METHODS:</b> We retrospectively evaluated the initial MR images (<i>n</i> = 7), including DWI (<i>n</i> = 5), and follow-up MR images (<i>n</i> = 4) after drug discontinuation in 7 patents with clinically diagnosed MIE. The topographic distributions of lesions were evaluated on MR images, and DWI signal intensities and apparent diffusion coefficient (ADC) values of the lesions were assessed. <b>RESULTS:</b> MR images demonstrated bilateral symmetric T2 hyperintense lesions in the cerebellar dentate nucleus (<i>n</i> = 7), midbrain (<i>n</i> = 7), dorsal pons (<i>n</i> = 6), medulla (<i>n</i> = 4), corpus callosum (<i>n</i> = 4), and cerebral white matter (<i>n</i> = 1). Brain stem lesions involved the following: tectum (<i>n</i> = 5), tegmentum (<i>n</i> = 4), red nucleus (<i>n</i> = 3) of the midbrain, vestibular nucleus (<i>n</i> = 6), and a focal tegmental lesion involving the superior olivary nucleus (<i>n</i> = 6) and abducens nucleus (<i>n</i> = 4) of the pons and vestibular nucleus (<i>n</i> = 4) and inferior olivary nucleus (<i>n</i> = 1) of the medulla. DWI (<i>n</i> = 5) showed isointensity or hyperintensity of lesions, and the decreased ADC value was found only in the corpus callosum lesions (<i>n</i> = 2). All detected lesions were completely reversible at follow-up except for the single corpus callosum lesion with an initial low ADC value. <b>CONCLUSION:</b> Brain lesions were typically located at the cerebellar dentate nucleus, midbrain, dorsal pons, medulla, and splenium of the corpus callosum. According to DWI, most of the lesions in MIE probably corresponded to areas of vasogenic edema, whereas only some of them, located in the corpus callosum, corresponded to cytotoxic edema.