Hippocampi and midbrain lesions in carbon monoxide intoxication: a rare case report

Carbon monoxide (CO) intoxication can lead to various brain lesions, with the globus pallidus being the most common site of injury. Herein, we report a rare case of CO poisoning with acute bilateral hippocampal lesions and delayed midbrain involvement of the substantia nigra.

A woman in her twenties who attempted suicide by burning charcoal briquettes presented with a Glasgow Coma Scale score of 3/15. Initial head computed tomography revealed low-density areas in the bilateral globus pallidus and hippocampi. Magnetic resonance imaging (MRI) on day 3 showed high signal intensity in the same regions on diffusion-weighted imaging (DWI), with a corresponding low signal on the apparent diffusion coefficient map and high signal intensity on fluid-attenuated inversion recovery imaging. The patient underwent hyperbaric oxygen therapy (HBOT) and gradually regained consciousness. However, the patient experienced persistent short-term memory loss. Follow-up MRI on day 23 showed improvement in the hippocampal and globus pallidus lesions but revealed new bilateral high-signal lesions in the substantia nigra on DWI. Despite these findings, the patient did not exhibit any extrapyramidal signs. Subsequent HBOT sessions led to further improvements in her cognitive function, as evidenced by an increase in her Mini-Mental State Examination score from 13/30 to 27/30.

This case highlights the importance of serial neuroimaging in CO poisoning, as delayed midbrain lesions may occur more frequently than previously thought, even in the absence of overt neurological symptoms. The patient's cognitive recovery and lack of parkinsonism suggests that early intervention with HBOT may help mitigate the long-term consequences of CO-induced brain injury.