MR imaging of metronidazole-induced encephalopathy: lesion distribution and diffusion-weighted imaging findings

Abstract

Background and purpose: 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.

Materials and methods: We retrospectively evaluated the initial MR images (n = 7), including DWI (n = 5), and follow-up MR images (n = 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.

Results: MR images demonstrated bilateral symmetric T2 hyperintense lesions in the cerebellar dentate nucleus (n = 7), midbrain (n = 7), dorsal pons (n = 6), medulla (n = 4), corpus callosum (n = 4), and cerebral white matter (n = 1). Brain stem lesions involved the following: tectum (n = 5), tegmentum (n = 4), red nucleus (n = 3) of the midbrain, vestibular nucleus (n = 6), and a focal tegmental lesion involving the superior olivary nucleus (n = 6) and abducens nucleus (n = 4) of the pons and vestibular nucleus (n = 4) and inferior olivary nucleus (n = 1) of the medulla. DWI (n = 5) showed isointensity or hyperintensity of lesions, and the decreased ADC value was found only in the corpus callosum lesions (n = 2). All detected lesions were completely reversible at follow-up except for the single corpus callosum lesion with an initial low ADC value.

Conclusion: 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.

Fig 1.

A 54-year-old man (patient 4) with spontaneous bacterial peritonitis. A, Axial FLAIR (TR/TE/TI = 6000/120/2000 ms) images demonstrate bilateral symmetric hyperintense lesions in the dorsal medulla (black thick arrows), vestibular (black thin arrows), abducens (white arrows), and a focal tegmental lesion of the superior olivary nuclei (arrowheads) of the dorsal pons, dentate nuclei of the cerebellum, red nuclei and tegmentum of the midbrain, and the splenium of the corpus callosum. B, DWIs (TR/TE = 3396/60) show bright signal intensity at the peripheral part of the cerebellar dentate nuclei and central part of the splenium. The lesions of the low pons and tegmentum of the midbrain are slightly hyperintense, and the lesions of dorsal medulla and central part of dentate nuclei are isointense on DWI. C, ADC maps show a focal area of low ADC in the splenium of the corpus callosum (black arrow) and a high ADC area in most areas of the dentate nuclei (white arrows).

Fig 2.

A 55-year-old man with ischemic colitis (patient 6). A, Axial T2-weighted (TR/ TE = 5000/110) images demonstrate bilateral symmetric hyperintense lesions in the dorsal medulla, vestibular, abducens, and focal tegmental lesions of the superior olivary nuclei of the dorsal pons, dentate nuclei of the cerebellum, the tectum of the midbrain, and the splenium of the corpus callosum. B, DWI (TR/TE = 4000/73) and ADC maps show mild hyperintensity and slightly high ADC of the dentate nuclei and obvious hyperintensity and very low ADC of the splenium of the corpus callosum. C, Follow-up MR images obtained 15 days after drug discontinuation. T2-weighted images show that the hyperintense lesions of the dentate nucleus and pons have disappeared, but a residual hyperintense lesion is seen in the splenium of corpus callosum. Note the near normalization of ADC and residual hyperintensity of the residual splenium lesion on DWI.

Fig 3.

A 64-year-old man with an intra-abdominal abscess (patient 3). A, Axial FLAIR (TR/TE/TI = 10,000/122/2000) images show bilateral symmetric hyperintense lesions in the inferior olivary nuclei (arrows) and dorsal medulla, dorsal pons, cerebellar dentate nuclei, splenium and genu of corpus callosum, and subcortical white matter of both cerebral hemispheres. B, Follow-up FLAIR images obtained 17 days after drug discontinuation show complete reversal of all lesions.