Cholinergic dysfunction in cognitive impairments after aneurysmal subarachnoid hemorrhage

Area of Science:

• Neuroscience
• Neurology
• Ophthalmology

Background:

• Cognitive impairments are common sequelae of subarachnoid hemorrhage (SAH).
• The neurobiological underpinnings of post-SAH cognitive deficits remain largely unexplored.
• Cholinergic system dysfunction is implicated in cognitive decline.

Purpose of the Study:

• To investigate cholinergic function in patients following aneurysmal SAH.
• To assess the utility of the tropicamide drop test, a measure of cholinergic function, in post-SAH patients.
• To correlate pupillary response to tropicamide with cognitive status.

Main Methods:

• Seventeen surgically treated aneurysmal SAH patients were categorized into two groups based on Mini-Mental State Examination (MMSE) scores.
• The tropicamide drop test was administered, measuring pupil diameter before and after instillation of tropicamide or saline.
• Pupil dilation ratios were calculated to assess cholinergic response.

Main Results:

• Patients with lower MMSE scores (Group B) exhibited a trend towards higher mean pupil dilation ratios compared to those with higher scores (Group A), though not statistically significant (P=0.18).
• The relative dilation ratio (comparing tropicamide-affected eye to saline-affected eye) was significantly higher in Group B (1.41 ± 0.36) than in Group A (1.06 ± 0.20) (P < 0.05).

Conclusions:

• The study identified cholinergic dysfunction in patients experiencing cognitive impairment after SAH.
• Pupillary response to tropicamide serves as a biomarker for cognitive deficits post-SAH.
• These findings offer insights into the pathophysiology of cognitive impairment following SAH and may inform future therapeutic strategies.