Distinctive feeding vessel architecture and sparse collateralization may underlie the characteristic early temporal pole and external capsule white matter compromise in CADASIL

Abstract

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common monogenic cause of stroke. Mutations in the NOTCH3 gene cause vasculopathic changes predominantly involving medium and small brain arteries leading to progressively impaired cerebrovascular autoregulation, hypoperfusion, and ischemia. Magnetic resonance neuroimaging of CADASIL patients shows progressive white matter hyperintensity and accumulation of deep infarcts. Though these findings resemble in many respects changes seen in hypertensive cerebral small vessel disease, CADASIL is distinguished by early and extensive involvement of two regions: the white matter of the anterior temporal poles and the external capsules. Despite the longstanding reliance on presence of these findings to render a diagnosis of CADASIL, to our knowledge no pathophysiologic explanation has hitherto been advanced for the early and extensive temporal pole and external capsule. This paper advances the hypothesis that two distinctive features of the vascularization of temporal polar and external capsule white matter underly their early injury in CADASIL. First, the intermediate lumen diameters (0.75–1.00 mm) and the obtuse takeoff angles of the temporopolar artery (supplying temporal pole white matter) and the lateral lenticulostriate arteries (supplying the external capsule) cause intensified radial and sheer wall stress and vessel injury. Second, the sparse collateral supply to these regions potentiates the ischemic insult from compromise of directly supplying vessels.