Occurence and variability in acute formation of leptomeningeal collaterals in proximal middle cerebral artery occlusion.

BACKGROUND We performed this study to semi-quantitatively characterize the formation of leptomeningeal collaterals in acute middle cerebral artery (MCA) occlusion caused by intravascular balloon inflation. METHODS The anatomic extent of leptomeningeal collateral blood flow from the anterior cerebral artery territory to the MCA territory during occlusion of the M1 segment was graded based on angiographically visible retrograde reconstitution of the MCA segments on the delayed venous phase prior to and during inflation of the balloon. RESULTS During MCA occlusion, the leptomeningeal collaterals markedly improved in 5 of 7 patients and were graded as 1 (retrograde filling of distal M1 segment) in 3 patients, 2 (retrograde filling of proximal M2 segment) in 1 patient, 4 (retrograde filling of M3 segment) in 1 patient and 5 (none or minimal) in 2 patients. CONCLUSION Leptomeningeal collaterals from the anterior cerebral artery can form rapidly during MCA occlusion with considerable individual variability.