Quantitative middle cerebral artery flow in normal and vasospastic arteries

Area of Science:

• Neurology
• Medical Imaging
• Biomedical Engineering

Background:

• Middle cerebral artery (MCA) vasospasm is a critical complication after subarachnoid hemorrhage.
• Understanding the degree of vasospasm that compromises cerebral blood flow is vital for timely intervention.

Purpose of the Study:

• To quantify the degree of MCA vasospasm that reduces blood flow to less than one-third of normal.
• To establish the ischemic threshold for cerebral blood flow reduction in the MCA distribution.

Main Methods:

• Development of a computational fluid dynamics model simulating blood flow in the MCA distribution.
• Analysis of normal flow rates for a 3 mm trunk diameter (179 ml/min).
• Simulation of vasospasm by varying trunk diameter, branch diameter, and peripheral resistance.

Main Results:

• A 75% reduction in MCA trunk diameter decreased blood flow to less than one-third of normal.
• A 50% reduction in branch diameter also led to a similar reduction in blood flow.
• A threefold increase in peripheral resistance was required to achieve the same level of flow reduction.

Conclusions:

• Significant vasospasm, defined by substantial diameter reduction or increased resistance, is necessary to impair MCA blood flow below the ischemic threshold.
• These findings provide critical parameters for assessing the severity of vasospasm and its potential impact on cerebral perfusion.