Metronidazole-Induced Craniocervical Myoclonus with Reversible Bilateral Dentate Nucleus Lesions

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. JMD Dear Editor, Metronidazole is a widely prescribed drug that is used to treat bacterial and protozoal infections. Neurologic complications from metronidazole are rare but have been reported to exhibit the following syndromes: cerebellar syndrome, enceph-alopathy, seizures, autonomic neuropathy, optic neuropathy, and peripheral neuropathy. 1 Metronidazole-induced cerebellar syndrome is a rare adverse drug reaction, particularly when it involves lesions of the dentate nucleus; accompanying myoclo-nus is even more unusual. 2 Here, we report a patient who presented with craniocervical myoclonus involving bilateral dentate nucleus lesions following metronidazole use whose symptoms were reversible (including recovery of the dentate nucleus le-sions) after the discontinuation of metronidazole. The development of neurologic symptoms in metronidazole users is believed to be the result of metronidazole neurotoxicity because immediate discontinuation of the drug can improve symptoms and prevent further injury. 3 An 82-year-old man with hypertension and Alzheimer's disease presented to the emergency department complaining of jerky movements for 3 days. He had been taking metronidazole for acute cholecystitis at a nursing home for 12 days prior to presentation (500 mg three times a day, estimated cumulative dose of approximately 30 g). Rhythmic synchronous myoclonic movements involving the eyebrow, neck and bilateral upper arms were continuously observed at a frequency of 1–2 Hz. His mental status was clear and other neurological examinations were unremarkable. Repeated electroencephalography did not show any epileptiform discharges. His body temperature was normal. His glomerular filtration rate was 35 mL/min and liver function tests were normal. Cerebrospinal fluid examination was normal. Brain magnetic resonance imaging (MRI) showed high signal intensity in the bilateral dentate nuclei of the cerebellum on the T2 and T2 fluid-attenuated inversion recovery (FLAIR) scans (Figure 1A). Metronidazole was discontinued and clonazepam was prescribed (0.5 mg three times a day for 3 days), after which his myoclonus completely resolved. Clonazepam was then tapered off over the course of 3 days and the patient's my-oclonus did not recur. Sixteen days after his initial MRI scan, a repeat MRI was performed, which showed a complete recovery of the signal changes that were previously observed in the bilateral dentate nuclei (Figure 1B). Metronidazole neurotoxicity is rare but can manifest as several neurologic syndromes. A …