Leptomeningeal collateral response and computed tomographic perfusion mismatch in acute middle cerebral artery occlusion.

To identify the relationship between the magnitude of leptomeningeal collaterals (LMC) on digital subtraction angiography (DSA) and regional cerebral blood volume (rCBV)/regional cerebral blood flow (rCBF) mismatch on computed tomography perfusion (CTP) in patients with acute middle cerebral artery (MCA) occlusion.We reviewed the clinical records, and neuroimaging studies in consecutive patients with proximal MCA (M1-segment) and proximal branch (M2-segment) occlusion undergoing endovascular treatment following the demonstration of mismatch on CTP. DSA images acquired prior to the treatment were used to grade collateral flow from the anterior cerebral artery to the MCA on a scale ranging from 1 to 5, based on retrograde reconstitution of MCA segments in the late arterial phase. CTP images were reviewed and rCBV/rCBF mismatch was categorized as minor (≤ 1/3 of MCA territory), moderate (1/3-2/3 of MCA territory), or severe (> 2/3 to complete territory). Statistical association was assessed using Pearson exact test.A total of sixteen patients were studied (10 were men; mean age of 69 years). Mean time from symptom onset to CTP was 146 minutes. Patients with M1-segment occlusion (n=10) had more severe rCBV/rCBF mismatch compared to patients with M2-segment occlusion (p=0.016). There was no association between the magnitude of LMC and severity of rCBV/rCBF mismatch on CTP.The magnitude of LMC on DSA does not correlate with the severity of rCBV/rCBF mismatch in patients with MCA occlusion. This result suggests that additional factors, such as micro vascular failure, may contribute to altered cerebral perfusion.