Introduction: “Deep tiny flow voids” (DTFV), defined as three or more flow voids along occlusive middle cerebral artery(MCA) on at least two consecutive T2-weigthed image slices of high-resolution magnetic resonance imaging(HR-MRI), were recently proposed as a sign of pathological collaterals formation.
Objective: In this study, we sought to examine the prevalence and clinical relevance of DTFV in patients with steno-occlusive MCA disease.
Methods: We retrospectively reviewed the HR-MRI and clinical data of 477 patients with MCA steno-occlusive disease. The presence and distribution of DTFV were observed. The relationships among DTFV, the degree of stenosis, and infarctions were analyzed. To clarify the difference between DTFV and moyamoya collaterals, we also compared the HR-MRI findings of 102 patients with moyamoya disease and the patients with DTFV.
Results: DTFV were revealed in 112 (23.5%) patients. The prevalence of DTFV was 1.4% in mild stenosis (<50%),12.8% in moderate stenosis (50-70%), 40.6% in severe stenosis (70-99%) and 50.7% in occlusions of MCA. DTFV were more common in asymptomatic than in symptomatic patients with severe stenosis (49.3% vs 30.9%, p=0.025) and occlusions (68.0% vs 41.7%, p=0.033). As high as 71.4% DTFV distributed in more than 3 of 4 quadrants around MCA stem. Obvious flow voids in basal ganglia region were observed in 58 (56.9%) patients with Moyamoya disease, but in none of patients with DTFV (p<0.001).
Conclusions: DTFV are common in patients with severe steno-occlusive MCA, especially in asymptomatic patients. We hypothesize DTFV are suggestive of non-Moyamoya vessel network formation due to chronic hypoxia and ischemia.