Rete anomaly of the middle cerebral artery: case series of 13 patients from the Northeastern United States

Background Rete middle cerebral artery (MCA) is a rare anomaly of the intracranial circulation that mimics congenital Moyamoya disease (MMD). Similar to MMD, it is reported almost exclusively in East-Asian ethnicities. Here, we report 13 patients with rete MCA anomaly from a predominantly non-Asian background in the USA. Methods Consecutive patients (≥18 years of age) with rete MCA seen in the neurovascular clinic at Columbia University Medical Center (2014–2024) were included. We retrieved demographics, clinical presentation, imaging findings, neurosurgical interventions, and clinical outcomes. Results 13 patients were identified (mean age 42±21 years, 83.3% female): 7 were White (53.8%), 3 were multiracial Hispanic (23.1%), 2 were South-Asian (15.4%), and 1 was Black (7.7%). Rete MCA was unilateral in all (n=13) and collaterals typical of MMD were absent. MRI vessel wall imaging (n=6) did not show enhancement characteristic of MMD. With serial imaging (n=12), there was no progression or contralateral MCA involvement. Strokes occurred in 5 (38.5%): subarachnoid hemorrhage (n=2), intracerebral hemorrhage (n=2), and ischemic stroke (n=1) from cardioembolism (n=1). 5 (38.5%) underwent neurosurgical bypass (encephaloduroarteriosynangiosis) due to presumed initial diagnosis of MMD (n=4), or for hypoperfusion on imaging related to rete MCA (n=1). Over a 4±3-year mean follow-up, there were no acute neurovascular events. Conclusions Rete MCA anomaly occurs in non-Asian populations, and is likely benign relative to MMD. The diagnosis should be considered with unilateral, non-progressive findings, and absent MMD-type collaterals. Neurosurgical bypass appears safe, but studies are required to assess the natural history and stroke risk in this condition.