Quantitative Magnetic Resonance Angiography in Internal Carotid Artery Occlusion with Primary Collateral Pathway

Abstract

Background and purpose: Quantitative magnetic resonance angiography (Q-MRA) enables direct measurement of volume flow rate (VFR) of intracranial arteries. We aimed to evaluate the collateral flows in internal carotid artery (ICA) occlusion with primary collateral pathway via circle of Willis using Q-MRA, and to compare them between patients who recently developed ipsilateral symptomatic ischemia and those who did not.

Methods: Between 2012 and 2014, 505 patients underwent Q-MRA in our institution. Among these, 33 patients who had unilateral ICA occlusion with primary collateral pathway were identified, and grouped into asymptomatic patients, stable patients with chronic infarction, and symptomatic patients with acute/subacute infarction. Mean VFR (mVFR) in intracranial arteries was measured and compared between the patients' groups. Kruskal-Wallis test was used for statistical analysis.

Results: Six patients were asymptomatic, fifteen with chronic infarction were stable, and twelve with acute/subacute infarction were symptomatic. The mVFR of ipsilateral middle cerebral artery in symptomatic patients was significantly lower than those in stable or asymptomatic patients (73.7±45.6 mL/min vs. 119.9±36.1 mL/min vs. 121.8±42.0 mL/min; P = 0.04). Total sum of the mVFR of ipsilateral anterior, middle, and posterior cerebral arteries was significantly lower in symptomatic patients than those in other groups (229.3 ± 51.3 mL/min vs. 282.0±68.6 mL/min vs. 314.0±44.4 mL/min; P = 0.02).

Conclusions: Q-MRA could be helpful to demonstrate the difference in the degree of primary collateral flow in ICA occlusion between the patients with recent symptomatic ischemia and those without.

Keywords: Carotid artery, internal; Collateral circulation; Magnetic resonance angiography.

Figure 1.

Q-MRA images of a 47-year-old male patient in group 1. (A) Left ICA is occluded, but patent ipsilateral MCA flow from posterior communicating arterial collateral is demonstrated on TOF-MRA. (B) The section plane (yellow) shows the location of the measurement of left MCA flow. (C) The overall mVFR of the intracranial and cervical arteries are shown in the report of NOVA software.

Figure 2.

(A) T2-weighted imaging and fluid-attenuated inversion recovery images of a 67-year-old male patient. About 3.1 cm sized chronic infarction is noted in right anterior corona radiata. (B) Diffusion-weighted imaging and Apparent diffusion coefficient map of an 80-year-old male. He had sudden onset right hand weakness at the time of imaging. There is about 3.3 cm sized acute infarction in left anterior corona radiata. (C) TOF MRA of the 67-year-old male with chronic infarction. Patent flow of MCA ipsilateral to the occluded ICA is visualized. The mVFR of the ipsilateral MCA was calculated as 94 mL/min. (D) The 80-year-old male with acute infarction in the territory in left MCA also shows intact flow of ipsilateral MCA to the occluded ICA on TOF MRA. However, the mVFR of this MCA was calculated as 65 mL/min.