Angiographic Characteristics of Cerebral Perfusion and Hemodynamics of the Bridging Artery After Surgical Treatment of Unilateral Moyamoya Disease

Abstract

Purpose: To investigate the characteristics of cerebral perfusion and hemodynamics of bypass grafting in the treatment of moyamoya disease (MMD) using the iFlow color-coded flow map in comparison with magnetic resonance imaging-perfusion-weighted imaging (MRI-PWI) and computational fluid dynamic (CFD) analysis.

Materials and methods: Patients with MMD treated with bypass grafting who had undergone MRI PWI and digital subtraction angiography for iFlow color-coded map was retrospectively enrolled and CFD was performed for calculating the hemodynamic stresses around the bypass grafting.

Results: Forty-five patients with unilateral MMD treated with bypass surgery were enrolled. The bypass surgery was successful in all patients, with no severe neurological complications during the periprocedural period. Followed up for 4-12 months (median 5.5), the neurological function was good in all patients. The cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to peak (TTP) were significantly (p < 0.05) improved in the middle cerebral artery distribution area on the surgical side before and after vascular bypass, and the difference of TTP (s) measured from the proximal bifurcation of common carotid artery to the confluence of sinus was also significant (p < 0.05). A significant (p < 0.05) positive correlation existed in the perfusion parameters between the iFlow blood perfusion and the MRI-PWI perfusion, with r-value for TTP of 0.765 (p < 0.01). The iFlow color-coded blood flow map showed warm color changes on the diseased side, similar to those on the contralateral side. In CFD analysis, the hemodynamic stresses were all improved, in and around the bypass grafting and distal vessels, which were beneficial to blood flow entering distal arterial branches.

Conclusion: The iFlow color-coded flow map can be used to analyze cerebral perfusion after bypass grafting for MMD, similar to MRI-PWI, and CFD can be used to analyze the hemodynamics after bypass grafting, revealing improved hemodynamics to promote blood flow entering distal arteries.

Keywords: bypass grafting; computational fluid dynamics; digital subtraction angiography; hemodynamic stresses; moyamoya disease.

FIGURE 1

After right superficial temporal artery-middle cerebral artery (STA-MCA) bypass grafting in one patient, no recurrence of stroke and transient ischemic attack was found at 4-month follow-up, and cerebral angiography showed that the bypass supplied blood to the brain. (A,B) Cerebral angiography before the bypass surgery was shown. (C,D) Mean transit time (C) and TTP (D) were shown before surgery in MRI-PWI. (E,F) Cerebral angiography after surgery. (G,H) Four months after surgery, the MTT (G) and TTP (H) were significantly improved.

FIGURE 2

Pearson correlation in TTP between MRIPWI and iFlow outcome in patients with moyamoya.

FIGURE 3

The iFlow color-coded blood flow map was constructed on DSA postoperative cerebral angiographic images. (A–D) Angiography through the external carotid artery showed warm color changes on the diseased side (A,B), similar to those on the contralateral side (C,D). (E,F) The time–density curve at the anastomosis and region of interest around the upper and lower trunk of the MCA showed that the contrast agent apparently disappeared at the anastomosis while the contrast agent peak value was significantly increased at the upper and lower trunk of the MCA. The interval from the upper or lower MCA trunk to the upper middle sagittal sinus was roughly the same.

FIGURE 4

Distribution of hemodynamic stresses in and around the surgical bypass vessel after bypass surgery. (A–C) Distribution of wall shear stress (WSS) in and around the bypass vessel was shown. No abnormal increase was demonstrated in WSS in the bypass or the anastomosis, and the middle cerebral artery supply blood reversely without producing abnormal WSS. (D) The distribution of dynamic pressure was shown, with increased dynamic pressure around the anastomosis to promote blood flow distally, but the dynamic pressure was stable in the whole vessels. (E) The distribution of total pressure was shown in and around the bypass vessel. Proximal to the anastomosis, the total pressure was high to promote blood flow distally. A low total pressure was shown in the distal branches of the middle cerebral artery, beneficial to blood entering distal branches. The color scale represents the size of the value.