Temporal Base Transdural Anastomosis in Moyamoya Disease: A Potential Association with Posterior Cerebral Artery Involvement and Clinical Importance.

Moyamoya disease is associated with the formation of collateral pathways, including transdural anastomosis, such as vault and ethmoidal moyamoya. However, temporal base transdural anastomosis remains unrecognized. This study investigates the imaging characteristics and features of temporal base transdural anastomosis in moyamoya disease. This retrospective review was conducted on 164 hemispheres from 82 patients with moyamoya disease admitted to our institution between 2012 and 2024. Digital subtraction angiography helped identify temporal base transdural anastomosis, which is classified as "obvious" or "faint" types based on digital subtraction angiography findings. Affected hemispheres and patients were grouped based on the presence or absence of temporal base transdural anastomosis, and their clinical characteristics were analyzed. Both types of temporal base transdural anastomosis were found in 10 of 164 hemispheres (6.1%) and 10 of 82 patients (12.2%). The obvious-type temporal base transdural anastomosis was detected in three hemispheres (1.8%) among three patients (3.7%). Temporal base transdural anastomosis was predominantly associated with advanced-stage moyamoya disease (Suzuki stage ≥4) and posterior cerebral artery involvement (p < 0.01). Although no significant association was found between the presence of temporal base transdural anastomosis and previous bypass surgery (p = 0.26), obvious temporal base transdural anastomosis was frequently found in cases without bypass surgery (two of three cases; 66.7%), and all obvious temporal base transdural anastomosis cases received no direct bypass surgery. Temporal base transdural anastomosis is considered to compensate for blood flow to the temporal lobe and is associated with posterior cerebral artery involvement. In addition, temporal base transdural anastomosis may receive high hemodynamic stress due to blood flow from the middle meningeal artery main trunk that may be related to aneurysmal formation or an unknown origin intracranial hemorrhage.