Transmission electron microscopy ultrastructural characteristics of the distal middle cerebral artery in moyamoya disease.

The etiology of moyamoya disease (MMD) remains unknown. The main pathological finding is fibrocellular thickening of the intima, irregular undulation of the internal elastic lamina affecting the distal portions of the internal carotid artery and A1 and M1 segments. Our aim is to describe the histological and electron microscope ultrastructural characteristics of cortical MMD vessels (middle cerebral artery) in hemorrhagic and ischemic presentation along different Suzuki stages. From January 2022 to December 2022, we collected clinical and radiological data of 310 patients with MMD, among them we identified 52 patients that underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass. We collected arterial walls (excisional arteriotomy) of the recipient arteries specifically, M3 or M4 segments of the MCA. Observations and micrographs were captured utilizing an HT7700 transmission electron microscope. MMD patients exhibit severe internal elastic lamina (IEL) changes as compared to patients with intracranial atherosclerosis. Hemorrhagic MMD presentation showed a higher score of IEL ruptured when comparing to ischemic presentation. Endothelial cells in hemorrhagic MMD showed more significant contraction compared to those in ischemic moyamoya disease. Hemorrhagic and ischemic MMD patients showed no statistically significant differences when correlated to Suzuki stages and cerebral perfusion. MMD patients exhibit IEL changes and endothelial cells contraction extending into the distal segments of the middle cerebral artery. Hemorrhagic MMD presentation has higher IEL rupture score making these patients probably more susceptible for hemorrhage. This study provides an inside of the extension of MMD into the brain surface.