To report a case of severe methanol toxicity with evidence of unique optic nerve diffusion restriction on brain MRI.

Optic nerve diffusion restriction on MRI diffusion weighted imaging can be seen with acute demyelination, inflammation, idiopathic intracranial hypertension, infection, trauma, and ischemic optic neuropathy. There are very few cases reported of severe methanol toxicity causing optic nerve diffusion restriction on MRI.

We report a case of a 35-year old male who presented with sudden onset confusion, vision impairment, and seizures following drinking unknown liquid. He was agitated, not following commands, tachycardic, tachypneic, and in acute respiratory failure requiring intubation. He was non-focal on neurologic examination.  He had elevated serum osmolality at 406 mOsm/kg. ABG showed high anion gap metabolic acidosis with pH of 6.70. Methanol level was 238 mg/dL.

Brain MRI demonstrated: classic T2/FLAIR putamen hyperintensity bilaterally, susceptibility weighted imaging with evidence of bilateral putaminal hemorrhage, and unique optic nerve diffusion restriction bilaterally with corresponding ADC hypointensity. Despite hemodialysis and supportive treatment the patient continued to deteriorate clinically and passed away 6 days following admission.

Methanol toxicity is associated with high mortality. It is associated with neurologic sequelae such as vision loss that is potentially irreversible. Toxic formic acid accumulation, a methanol metabolite, leads to mitochondrial enzyme inhibition causing ATP depletion and cytotoxic hypoxia due to impairment of mitochondrial oxygen utilization. The associated acidosis results in dilatation of cerebral vessels, which facilitates calcium ion entry into the cells and more ATP derangement. The retinal ganglion cells and axons are selectively vulnerable causing blindness.