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Cerebral metronidazole toxicity

Case contributed by Dr Stan Buckens


Patient suffering from cerebellar syndrome and sensory neuropathy several months after surgical and medical treatment for frontal cerebral abscesses originating from the sinuses.

Patient Data

Age: 45
Gender: Female

Pre-operative MRI Brain

Pre-operative MRI scan showing bi-frontal abscesses in communication with fluid-filled sinuses. There is are no signal abnormalities elsewhere in the brain.


Several months later - MRI Brain

New high signal in the splenium of the corpus callosum, in the ventral mesencephalon  and tectum, bilaterally in the nucleus dentatus and in the medulla oblongata. Note the high signal on DWI with high signal on the corresponding ADC map. This pattern is consistent with metronidazole-induced toxicity. 

Frontally there is residual enhancement and gliosis from the massive abscess, where a bone-flap has been removed for surgical access. 

Case Discussion

This patient presented initially with headaches and sinusitis. CT scanning at presentation (not reproduced here) showed a frontal mass communicating with fluid filled sinuses, for which antibiotics (ceftriaxone and metronidazole) were started. MRI scanning confirmed intracerebral abscesses originating in sinusitis and the bi-frontal abscesses were surgically opened and drained.

Hereafter the patient recovered well until she developed nausea, trouble walking and a sensory neuropathy. A follow-up MRI scan showed a pattern of T2 hyperintense signal consistent with metronidazole-induced toxicity. Metronidazole had been prescribed for more than three months at this point. After ceasing metronidazole the ataxic symptoms subsided in a matter of days.

Central nervous system toxicity is a rare side-effect of metronidazole treatment, causing cerebellar ataxia, altered mental state and neuropathy. A characteristic pattern of T2 and FLAIR hyperintense signal bilaterally in the cerebellar dentate nuclei is most commonly seen, with the corpus callosum, the midbrain, the pons, or/and the medulla also being involved in some cases. 

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Case information

rID: 39223
Published: 26th Aug 2015
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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