Impaired cerebrovascular reserve in chronic steno-occlusive disease has been shown to be associated with poor leptomeningeal collaterals (LMCs) on digital subtraction angiography and increased stroke risk. We examined the relationship between the degree of LMCs and the flow change with Diamox challenge measured using quantitative magnetic resonance angiography (QMRA).

Patients with steno-occlusion in the internal carotid artery or middle cerebral artery (MCA) at our institution between 2007 and 2013 were retrospectively studied. Intracranial flows were obtained using QMRA, and flow change with Diamox (QMRA_Δd) was calculated as follows: ([flow after Diamox−flow before Diamox]/[flow before Diamox])×100%. Poor LMC was defined as grade 1 or 2, and robust LMC was defined as grade 3 or 4 based on the ASITN/SIR (American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology) grading system on digital subtraction angiography.

Thirty-eight patients had angiographic and flow data. Ipsilateral MCA QMRA_Δd was significantly lower versus the contralateral side (flow, 85.5 versus 135.9 mL/min; P<0.001 and QMRA_Δd, 24.0% versus 45.6%; P=0.01). If LMCs were robust (n=12), MCA QMRA_Δd was significantly higher (21.4% versus −26.8%; P=0.04) compared with patients with poor LMC (n=4).

We show that patients with more robust LMC have better MCA QMRA_Δd. Therefore, QMRA_Δd may be used for the functional assessment of LMC as a surrogate for cerebrovascular reserve in chronic internal carotid artery or MCA steno-occlusive disease.