Cerebral blood flow in small vessel disease: A systematic review and meta-analysis

• Published in: Journal of cerebral blood flow and metabolism Vol. 36; no. 10; pp. 1653 - 1667
• Main Authors: Shi, Yulu, Thrippleton, Michael J, Makin, Stephen D, Marshall, Ian, Geerlings, Mirjam I, de Craen, Anton JM, van Buchem, Mark A, Wardlaw, Joanna M
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.10.2016
• Subjects: Aging - pathology; Blood Flow Velocity - physiology; Cerebral Small Vessel Diseases - diagnostic imaging; Cerebral Small Vessel Diseases - pathology; Cerebral Small Vessel Diseases - physiopathology; Cerebrovascular Circulation - physiology; Dementia - diagnostic imaging; Dementia - pathology; Dementia - physiopathology; Gray Matter - blood supply; Gray Matter - diagnostic imaging; Gray Matter - pathology; Humans; Magnetic Resonance Angiography; Review; Ultrasonography, Doppler; White Matter - blood supply; White Matter - diagnostic imaging; White Matter - pathology; meta-analysis; cerebral small vessel disease; systematic review; Cerebral blood flow; white matter hyperintensities
• ISSN: 0271-678X; 1559-7016; 1559-7016
• DOI: 10.1177/0271678X16662891

White matter hyperintensities are frequent on neuroimaging of older people and are a key feature of cerebral small vessel disease. They are commonly attributed to chronic hypoperfusion, although whether low cerebral blood flow is cause or effect is unclear. We systematically reviewed studies that assessed cerebral blood flow in small vessel disease patients, performed meta-analysis and sensitivity analysis of potential confounders. Thirty-eight studies (n = 4006) met the inclusion criteria, including four longitudinal and 34 cross-sectional studies. Most cerebral blood flow data were from grey matter. Twenty-four cross-sectional studies (n = 1161) were meta-analysed, showing that cerebral blood flow was lower in subjects with more white matter hyperintensity, globally and in most grey and white matter regions (e.g. mean global cerebral blood flow: standardised mean difference−0.71, 95% CI −1.12, −0.30). These cerebral blood flow differences were attenuated by excluding studies in dementia or that lacked age-matching. Four longitudinal studies (n = 1079) gave differing results, e.g., more baseline white matter hyperintensity predated falling cerebral blood flow (3.9 years, n = 575); cerebral blood flow was low in regions that developed white matter hyperintensity (1.5 years, n = 40). Cerebral blood flow is lower in subjects with more white matter hyperintensity cross-sectionally, but evidence for falling cerebral blood flow predating increasing white matter hyperintensity is conflicting. Future studies should be longitudinal, obtain more white matter data, use better age-correction and stratify by clinical diagnosis.