Background: The validity of indirect bypass for adult patients with moyamoya disease is still debatable. Some patients are poor responders to indirect bypass, and additive intervention is occasionally required in these cases. Therefore, it is necessary to evaluate the development of collateral circulation as early as possible postoperatively.
Methods: Fifteen adult patients (>17 years old) with moyamoya disease (22 affected sides) who underwent encephalo-duro-arterio-synangiosis (EDAS) at Fukuoka University Hospital from April 2008 to August 2014 were included. All patients had ischemic symptoms of at least one hemisphere. Superficial temporal artery duplex ultrasonography (STDU) was performed before and 3, 6, and 12 months postoperatively. Digital subtraction angiography was performed 1 year after the operation to evaluate the development of collateral circulation. Hemispheres exhibiting collateral formation of more than one-third of the MCA distribution were defined as good responders, and those with less than one-third were defined as poor responders.
Results: EDAS induced the formation of well-developed collaterals in 17 of 22 affected sides (77.3%) of adult patients with ischemic moyamoya disease. Regardless of the degree of collateral formation, the ischemic event subsided eventually with time in all patients. In good responders, the pulsatility index obtained by STDU showed a drastic decrease 3 months after the operation, while it did not change significantly in poor responders. Absence of this decrease in the pulsatility index along with no change in the flow velocity reliably indicated poor responders.
Conclusions: Neovascularization after EDAS can be evaluated noninvasively in early phase using STDU.
Keywords: Duplex ultrasonography; Encephalo-duro-arterio-synangiosis; Indirect bypass; Moyamoya disease; Superficial temporal artery.