Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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March 10, 2022
Methanol Toxicity
- Background:
- Methanol is oxidized into toxic formaldehyde and formic acid by alcohol dehydrogenase and formaldehyde dehydrogenase, respectively.
- The toxic metabolites are neurotoxic, particularly to the optic nerves and putamina.
- Note: After the neuroradiologist suggested methanol toxicity, the family confirmed methanol ingestion on the day the patient presented with myocardial infarction.
- Clinical Presentation:
- Dose-dependent and nonspecific manifestations range from blurry vision, nausea, vomiting, abdominal pain, drowsiness, confusion, seizures, coma, and even death if not treated.
- Key Diagnostic Features:
- Bilateral putaminal T2 prolongation and diffusion restriction, which can evolve to hemorrhagic necrosis
- Similar changes are seen in the optic nerves, subcortical white matter, and caudate nuclei.
- Uncommon areas of involvement are the corpus callosum, brainstem, and cerebellum.
- Differential Diagnoses:
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Carbon monoxide poisoning: Likely to involve the globus pallidus more than the putamen; injury of the cerebral cortex and subcortical white matter can also occur.
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Anoxic brain injury: Variable pattern of involvement depending on brain maturity and severity of the ischemic insult; it can involve the basal ganglia, thalami, hippocampi, and cerebellum, or it can present as watershed infarcts; mostly nonhemorrhagic
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Uremic encephalopathy: Symmetric swelling and edema of the lentiform nuclei with characteristic T2-hyperintense signal of the internal capsule, external capsule, and lamina terminalis (lentiform fork sign)
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Osmotic demyelination syndrome: T2 prolongation of the central pons and/or extrapontine sites
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Hypertensive hemorrhage: Basal ganglia hemorrhage is typically unilateral.
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Treatment:
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Antidote: Fomepizole or ethanol, which inhibit alcohol dehydrogenase, preventing the buildup of toxic metabolites
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Supportive: Intravenous fluids and correction of electrolyte disturbances and acidemia
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