The leak in a gas water heater was suspected. In the ER, the patient was unconscious and the COHb level was elevated.

Imaging studies, especially brain MRI, have demonstrated high sensitivity for detecting brain abnormalities after carbon monoxide poisoning. The most frequently affected areas are the brain regions with higher levels of iron (which are targeted by carboxyhemoglobin): the basal ganglia (especially the globus pallidus), and the substantia nigra.

Bilateral and symmetric lesions involving the globus pallidus suggest systemic or metabolic causes.

Differential diagnosis includes:

• toxic poisoning
  • methanol: necrosis of the putamen may be observed, white matter edema may occur
  • cyanide: also affects the cortex, putamen involvement
• metabolic abnormalities
  • hepatic cirrhosis: bilateral hyperintense areas also in the substantia nigra
  • Wilson disease: putaminal involvement, ventrolateral thalamus;
• hypoxic-ischemic encephalopathy: severe affects the cerebral cortex and hippocampi