[Intracerebral steal after acetazolamide administration]

Area of Science:

• Neurology
• Vascular Neurology
• Cerebrovascular Disease

Background:

• Internal carotid artery stenosis can be asymptomatic due to compensatory collateral flow via the Circle of Willis and microvascular reserve capacity.
• Vasomotor reactivity, a measure of cerebral arteriolar distensibility, is crucial for maintaining cerebral blood flow under stress.
• Assessing cerebrovascular reserve is vital in patients with significant carotid artery disease.

Observation:

• Three patients with severe unilateral internal carotid artery stenosis and contralateral severe stenosis or occlusion were studied.
• Transcranial Doppler ultrasound continuously measured middle cerebral artery blood flow velocity at rest and after acetazolamide administration.
• Arterial blood pressure and end-tidal CO2 were monitored to control for confounding physiological variables.

Findings:

• Resting collateral flow was observed from the anterior communicating artery, posterior communicating artery, and ophthalmic artery towards the side with more severe carotid disease.
• Following acetazolamide administration, middle cerebral artery blood flow velocity decreased on the side of severe occlusive carotid disease.
• Conversely, blood flow velocity increased on the contralateral side, indicating differential responses in cerebrovascular reserve.

Implications:

• The findings suggest an 'intracerebral steal' phenomenon where the acetazolamide-induced vasodilation in the contralateral hemisphere may draw blood flow away from the compromised ipsilateral hemisphere.
• The exhausted arteriolar system on the severely affected side may be unable to dilate, exacerbating the flow reduction.
• This study highlights the importance of assessing cerebrovascular reserve and collateral status in patients with bilateral internal carotid artery disease to predict stroke risk.