Abstract 164: The Impact Of Hemodynamic Factors On Stroke Risk In Moyamoya Phenomenon: A Prospective Natural History Study
Authors: Derdeyn Colin , Sagar James , Lee John , Aiyagari Venkatesh , Davis Patricia , Ivan Cristina , Prabhakaran Shyam , Shinawi Lina , Hantler Nancy , Zazulia Allyson , Grubb Robert , Zipfel Greg 
Published: July 2021

Background:
The natural history of moyamoya phenomenon is not well defined. Hemodynamic factors are likely involved in the risk of future stroke in these patients. The purpose of this study was to determine if severe hemodynamic impairment predicted stroke risk in patients with idiopathic moyamoya phenomenon.

Methods:
The study was a prospective, blindly-adjudicated, multicenter natural history study performed at five Midwestern sites. Inclusion criteria required unilateral or bilateral moyamoya phenomenon by catheter angiography and presumed idiopathic basal arterial occlusive disease. Baseline demographic and epidemiologic stroke risk factors, presenting symptoms (if any), and imaging findings were recorded on study entry. Baseline measurements of oxygen extraction fraction (OEF)were made using positron emission tomography. Hemodynamic impairment was determined by comparing the ratio of the left or right middle cerebral to cerebellar count-based OEF to normal control subjects. Those with values beyond the 95% confidence limit were considered increased. Subjects were followed for the occurrence of the primary endpoints, ischemic or hemorrhagic stroke. Follow up was done by phone interview at 6 month intervals and in person at one year. Outcome was analyzed on a per-hemisphere basis for patients with bilateral disease. The treated hemisphere was censored at the time of revascularization surgery for patients that underwent surgery. Surgery was allowed based on the discretion of treating physicians. The occurrence of stroke was adjudicated by an investigator blinded to hemodynamic status, based on records and imaging studies available at the time of the event.

Results:
Fifty subjects were recruited over a 5-year period and followed for a mean of 2.5 years. Mean age was 46 years. Sixteen were male. Forty had bilateral disease. Presenting symptoms were ischemic (39), hemorrhagic (5), seizure (2), headache (3) and none (2). A total of 15 patients (20 hemispheres) were censored, 4 of whom had increased OEF: 5 underwent bilateral and 10 unilateral revascularization procedures. Increased OEF was seen bilaterally in 7 (14%) and unilaterally in 8 patients (16%). Only 1 of the 15 patients with increased OEF suffered an ischemic stroke during follow-up. Two other endpoint events occurred, neither in hemispheres with increased OEF. One patient with bilateral disease and unilateral increased OEF suffered a hemorrhage one year after revascularization of the contralateral hemisphere. One patient with unilateral disease and normal OEF suffered a minor stroke 2 years after study entry. The annual risk for stroke in this cohort was 4.2%.

Conclusions:
The risk of stroke in this cohort of patients with moyamoya disease was very low relative to prior retrospective case series. Severe hemodynamic impairment was not associated with an increased risk of stroke.