Intracranial atherosclerotic disease associated with moyamoya collateral formation: histopathological findings

Atherosclerotic disease has been suspected as a cause of moyamoya disease in some patients but has not, to the authors' knowledge, been confirmed by pathological studies. The authors present the histopathological findings in a patient with moyamoya collateral formation associated with atherosclerotic occlusive disease of the distal internal carotid artery (ICA). Typical atheromatous changes were evident in the distal ICA and proximal middle cerebral artery. In addition, intimal thickening, fibrosis, and abnormal internal elastic lamina were present in these vessels. These findings are common in moyamoya but not in atherosclerotic disease. Proliferation and enlargement of the lenticulostriate arteries in the basal ganglia was also identified. Moyamoya phenomenon secondary to atherosclerotic disease has similar histopathological features to idiopathic moyamoya phenomenon, both in the affected large basal arteries and lenticulostriate collaterals. These findings support the hypothesis advanced by Peerless that moyamoya is a 2-step process involving an obliterative vasculopathy of the terminal ICA and a secondary proliferative response.

Abstract TMP38: Diminished Cortical Thickness and Increased Oxygen Extraction Fraction in Moyamoya Disease

PURPOSE: Chronic hemodynamic impairment may lead to reduced cortical thickness, perhaps related to metabolic down-regulation in cortical neurons. The purpose of this study was to determine whether hemodynamic impairment correlated with diminished cortical thickness in patients with idiopathic moyamoya phenomenon. METHODS: The study was a retrospective analysis of a prospective, blindly-adjudicated, multicenter patient cohort. Inclusion criteria required moyamoya phenomenon diagnosed by catheter angiography and presumed idiopathic basal arterial occlusive disease. Oxygen extraction fraction (OEF) was measured using positron emission tomography (PET). Hemodynamic impairment was determined by comparing the OEF of middle cerebral artery territories to cerebellar regions and to normal control subjects. MR imaging was obtained concurrently with PET, within several hours, and cortical thickness estimates were made with Freesurfer (http://surfer.nmr.mgh.harvard.edu). OEF measurements were then compared to cortical thickness measurements. RESULTS: Adequate MR studies were available for 40 subjects. Mean age was 44 years. Eleven were male. Thirty-one had bilateral disease. Three had increased OEF in both hemispheres and four had unilateral increased OEF. Three patients underwent revascularization surgery during follow-up. Robust linear regression of relative cortical thickness to relative OEF is shown below: the slope was -0.02693 (-0.03002, -0.02384), the intercept was 1.022 (1.019, 1.025) at 95% confidence. Pearson’s R-square was 0.9648. CONCLUSIONS: Chronic hemodynamic impairment may be associated with reduced cortical thickness. This may reflect reversible down-regulation or irreversible subclinical ischemic injury. Supported by NINDS RO1 NS051631, 1 UL1 RR024992-01, 1 TL1 RR024995-01 and 1 KL2 RR 024994-01 from the National Center for Research Resources (NCRR).