Magnetic Resonance Techniques for the Identification of Patients With Symptomatic Carotid Artery Occlusion at High Risk of Cerebral Ischemic Events

Abstract

Background and Purpose —We sought to assess whether MRI, MR angiography, or 1 H MR spectroscopy can be used to identify patients with symptomatic carotid artery occlusion (CAO) who are at high risk of recurrent ipsilateral cerebral ischemic events. Methods —In 115 consecutive patients with transient or moderately disabling symptoms of cerebral or retinal ischemia and ipsilateral CAO, we studied the prognostic value of (1) presence of a border-zone infarct; (2) quantitative flow in the middle cerebral artery (MCA) ipsilateral to the CAO; and (3) metabolic ratios in the centrum semiovale ipsilateral to the CAO. Results —Presence of a border-zone infarct and the rate of flow in the MCA did not have a significant relationship with recurrence of cerebral ischemic events. Patients with a low N -acetyl aspartate (NAA)/choline ratio had an annual risk of recurrent, ipsilateral, cerebral ischemic events of 16.0% (95% CI, 9.5 to 27.0), whereas this risk was 4.2% (95% CI, 2.2 to 8.0) in those with a normal NAA/choline ratio (hazard ratio, 0.43; 95% CI, 0.19 to 1.00). Patients who on entry had had only retinal symptoms had on average a higher NAA/choline ratio (mean difference, 0.25; 95% CI, 0.13 to 0.37) and a lower risk of recurrent cerebral ischemic events (odds ratio, 0.0; 95% CI, 0.0 to 0.6) than those with cerebral ischemic symptoms. Conclusions —NAA/choline ratio measured by 1 H MRS, but not the presence of a border-zone infarct or the amount of flow in the MCA, can identify patients with symptomatic CAO who are at risk of future ipsilateral cerebral ischemic events.