An interesting image (D Farmakiotis, B Zeluff. NEJM 2016; 374: 1465) shows an unusual side effect from metronidazole. This individual who had cirrhosis presented with confusion after a fall.

The MRIs below show “a symmetric, enhanced fluid-attenuated inversion recovery (FLAIR) signal in the dentate nuclei of the cerebellum (Panel A, arrow), a finding consistent with encephalopathy associated with metronidazole use.” Panel B shows resolution one month later following metronidazole discontinuation.

Risk factors for metronidazole encephalopathy:

• Liver dysfunction
• Prolonged treatment with metronidazole (typical cumulative dose >20 g)