Short-term changes in cerebral microhemodynamics after carotid stenting

Abstract

Background and purpose: The cerebral hemodynamic sequelae of interventions in patients with severe internal carotid artery (ICA) stenoses are not fully understood. In this study, we sought to determine the immediate changes in cerebral perfusion characteristics, determined by MR imaging in patients who have undergone unilateral transluminal angioplasty and stent placement.

Methods: Eleven patients with symptomatic high-grade ICA stenosis underwent MR imaging within 4 hours before and within 3 hours after carotid stent placement. First-pass gadolinium-enhanced imaging of perfusion was performed by using a gradient-recalled echo-planar technique. Localized relative cerebral blood volume (rCBV) and bolus first-moment transit time (TT(FM)) were calculated for different vascular territories (middle, anterior, and posterior cerebral arteries) in each hemisphere.

Results: Significantly longer TT(FM) (P <.005) was observed in the symptomatic territory of the middle cerebral artery before intervention. After intervention, TT(FM) remained significantly longer in this territory (P <.05). However, the magnitude of the interhemispheric asymmetry had declined significantly (50-60% reduction; P <.05). No significant differences or changes in rCBV were identified between hemispheres, between images, or in areas of unilateral leptomeningeal enhancement after intervention.

Conclusion: MR can demonstrate short-term partial resolution of timing asymmetry in interhemispheric perfusion after angioplasty and stent insertion for severe stenosis of the ICA.

Fig 1.

Signal intensity versus time. A, Mean signal intensity as a function of time from an ROI placed within the proximal intracranial branch of the MCA. The start-stop interval is used to define the mean baseline signal intensity, while the stop-last interval represents the first pass of the contrast bolus. Note that subsequent decreases in signal intensity occur as the contrast material is recirculated. B, Gamma-variate fit (solid line) to the baseline subtracted and inverted data (dashed line). The two variables used to quantify the curve are the first moment of the gamma-variate fit, termed the first-moment transit time (TT_FM), and the area under the fitted curve (relative cerebral blood volume [rCBV]).

Fig 2.

Placement of the ROIs. A, PCAT. B, MCAT1. C, MCAT2. D, ACAT.

Fig 3.

Perfusion data obtained at the level of the lateral ventricles in a patient with a symptomatic 95% stenosis in the left ICA and a 50% stenosis of the contralateral ICA. A, Preintervention rCBV map. B, Preintervention TT_FM map. C, Gamma-variate fits corresponding to the depicted regions show a longer TT_FM and a smaller rCBV in the symptomatic hemisphere. D, Postintervention rCBV map. E, Postintervention TT_FM map. F, Corresponding gamma-variate fits. Note the resolution of interhemispheric asymmetry in TT_FM.