Abstract
The authors experienced a curious phenomenon in an adult moyamoya patient. Mouth opening caused reversible occlusion of the donor superficial temporal artery (STA), and the patient exhibited transient cerebral ischemic symptoms. The aim of this study was to assess the incidence of such occlusion and the mechanisms behind this phenomenon.
Twelve adult moyamoya patients (15 affected sides) who underwent STA-middle cerebral artery anastomosis were included in the “direct group”. Ten patients with 15 affected sides who underwent indirect bypass surgery with STA as the donor vessel, were included in the “indirect group”. Ultrasound examination was performed postoperatively to determine whether mouth opening affects blood flow of the donor STA and leads to any ischemic symptoms. When changes in the blood flow of the donor STA were recognized, computed tomography angiography (CTA) or digital subtraction angiography (DSA) was performed under both mouth opening and closing conditions.
Under wide mouth opening condition, steno-occlusion of the donor STA occurred in 5 out of 15 sides (33.3%) in the direct group. On one side (6.7%), complete occlusion induced ischemic symptoms. In the indirect group, 1 out of 15 sides (6.7%) showed stenosis without any symptoms. Steno-occlusion occurred by at least two mechanisms; either the stretched temporalis muscle pushed the donor STA against the edge of the bone window, or the redundant donor STA kinked when the muscle was stretched.
Ischemic symptoms seem to occur rarely even with temporary occlusion of the donor STA. However, to avoid the “big bite ischemic phenomenon”, we recommend securing a sufficient distance between the donor STA and the edge of the bone window, and avoiding a redundant course of the donor STA within the muscle layer.
