Clinical History
37-year-old male patient admitted for brain abscess, treated with Augmentin, Vancomycine and metronidazole for the last 4 weeks. Patient was responding well to his medication till he started to have progressive changes in mental status, slurred speech and weakness of lower limbs.
Imaging Findings
MRI brain showed bilateral symmetrical bright T2 and FLAIR signal intensity at both cerebellar hemispheres of midline location namely at the dentate nucleus surrounding the fourth ventricle. No hydrocephalus.
No diffusion restriction could be seen.
No enhancement could be seen after contrast administration.
Unremarkable brainstem and cerebellum.
Improvement of previously seen brain abscess with improved associated surrounding vasogenic oedema.
Right maxillary sinus mucocele.
Impression:
MRI features are highly suggestive of drug induced toxicity.
Patient was on metronidazole, Augmentin and vancomycine for the last 4 weeks which raised the possibility of metronidazole-induced encephalopathy. The case was discussed with the neurologist who agreed to stop metronidazole.
A few days later the patient started to improve significantly and was then discharged in stable condition.
Discussion
Metronidazole is an antimicrobial agent which is commonly used to treat protozoal and anaerobic infections.
Duration and cumulative dose of metronidazole should be monitored to avoid its side effects like cerebellar dysfunction, seizures and peripheral neuropathy. [1, 2]
The mechanism of metronidazole toxicity is not clear yet.
On MRI about 93-100% of cases showed cerebellar involvement; however, changes in brain stem and corpus callosum have been reported. [3, 4]
Most of the cases show symmetrical bilateral involvement of cerebellar dentate nuclei in particular, and superior olivary nucleus and tegmentum to a lesser extent. [4]
It shows typically symmetrical high signal intensity in T2WI with restricted diffusion. No contrast enhancement is seen. [4]
If possibility of metronidazole-induced encephalopathy was raised, the treatment of choice would be to discontinue it. This showed a complete resolution of disease in 65% of cases, improvement in 29% and permanent cognitive impairment in only 3% of the cases. [4]
Differential Diagnosis List
Metronidazole -nduced encephalopathy
Acute Wernicke encephalopathy
Posterior reversible encephalopathy syndrome
Final Diagnosis
Metronidazole -nduced encephalopathy
