The constellation of abnormal FLAIR signal intensity in bilateral dentate nuclei, dorsal pons, as well as splenium of the corpus callosum raises concerns for a toxic/metabolic abnormality. Specifically, this pattern may be seen in metronidazole (Flagyl) neurotoxicity. Upon further review of the patient's medical history, she had been on multiple antibiotics and was started on metronidazole for endograft infection approximately five weeks prior to onset of vertigo. Upon review of findings, the patient was switched from metronidazole to other antibiotic therapy, and symptoms improved within days.
Metronidazole can affect both the peripheral nervous system as well as the central nervous system. Specifically, it can produce cerebellar dysfunction, as seen in this case. MRI can demonstrate T2 signal abnormality in the bilateral dentate nuclei, midbrain, dorsal pons and medulla and splenium of the corpus callosum. Mildly reduced diffusion can be seen in the corpus callosum, possibly related to the density of axonal fibers in this structure. For most cases, both MRI findings and clinical symptoms reverse upon cessation of metronidazole therapy.
While bilateral dentate involvement is characteristic of metronidazole neurotoxicity, it is not the only process which can involve these structures. Differential considerations for this finding include other metabolic disorders such as maple syrup urine disease, as well as toxic and infectious causes such as enterovirus encephalopathy and methyl bromide intoxication. Wernicke's encephalopathy can clinically present very similarly as metronidazole induced encephalopathy and remains an important differential consideration, with symmetric areas of FLAIR signal abnormality which more commonly involves the mammillary bodies, medial thalami, periaqueductal gray matter, and midbrain tectum.