Preoperative impairment of cerebral hemodynamics predicts the development of new cerebral ischemic events after carotid endarterectomy (CEA), including neurological deficits and cerebral ischemic lesions on diffusion weighted MR imaging. Furthermore, the signal intensity of the middle cerebral artery (MCA) on single-slab 3D time-of-flight MR angiography (MRA) can assess hemodynamic impairment in the cerebral hemisphere. The purpose of the present study was to determine whether, on preoperative MR angiography, the signal intensity of the MCA can be used to identify patients at risk for development of cerebral ischemic events after CEA.
The signal intensity of the MCA ipsilateral to CEA on preoperative MR angiography was graded according to the ability to visualize the MCA in 106 patients with unilateral internal carotid artery stenosis (≥ 70%). Diffusion weighted MR imaging was performed within 3 days of and 24 hours after surgery. The presence or absence of new postoperative neurological deficits was also evaluated.
Cerebral ischemic events after CEA were observed in 16 patients. Reduced signal intensity of the MCA on preoperative MR angiography was the only significant independent predictor of postoperative cerebral ischemic events. When the reduced MCA signal intensity on preoperative MR angiography was defined as an impairment in cerebral hemodynamics, MR angiography grading resulted in an 88% sensitivity and 63% specificity, with a 30% positive- and a 97% negative-predictive value for the development of postoperative cerebral ischemic events.
Signal intensity of the MCA on preoperative single-slab 3D time-of-flight MR angiography is useful for identifying patients at risk for cerebral ischemic events after CEA.