Article

Carotid endarterectomy improves cerebrovascular reserve capacity preferentially in patients with preoperative impairment as indicated by asymmetric BOLD response to hypercapnia.

Department of Academic Radiology, University of Nottingham, Queens Medical Centre, Nottingham, UK.
European journal of vascular and endovascular surgery: the official journal of the European Society for Vascular Surgery (Impact Factor: 2.92). 10/2009; 38(5):546-51. DOI: 10.1016/j.ejvs.2009.06.010
Source: PubMed

ABSTRACT In patients with symptomatic carotid artery disease the predominant mechanism causing ischaemic injury is considered to be thromboembolic, however compromise of cerebral haemodynamics is considered to be a significant factor. Removal of the embolic source is accepted as the major benefit from carotid endarterectomy (CEA), however improvement in cerebral haemodynamics may be another beneficial outcome as suggested by transcranial doppler (TCD). Blood oxygen level-dependent (BOLD) hypercapnia functional magnetic resonance imaging (fMRI) can be used to map the cerebrovascular reserve (CVR). The aim of this study was to assess the effects of carotid surgery on cerebral haemodynamics in patients with carotid artery disease using a hypercapnia BOLD fMRI and assessment of hemispheric asymmetry.
Seventeen patients with symptomatic internal carotid artery stenosis were scanned using a clinical 1.5T MR scanner. Scanning was done immediately prior to and between 4 and 8 weeks after CEA. 10% carbon dioxide was administered to achieve transient episodes of hypercapnia. The data was analyzed using FMRIB Software Library (FSL) software to derive percentage signal change (PSC) for the grey matter of the middle cerebral artery (MCA-GM) territory for both hemispheres. MCA-GM PSC was furthermore normalized to the contralateral hemisphere to derive an Hemispheric Asymmetry Index (hAI) for all patients pre- and postoperatively.
Ipsilateral GM CVR improved significantly following CEA (2.47% preoperatively vs. 2.73% postoperatively, p=0.038). There was no change in CVR in the contralateral grey and white matter MCA territories (p=0.27, p=0.1). Also, the hAI was significantly more shifted to the ipsilateral hemisphere after CEA (preoperative hAI -0.56, vs. -3.90 postoperatively, p=0.02). Patients with an impaired hAI preoperatively were found to show the greatest improvement in PSC and hAI following CEA (p=0.007).
CEA resulted in improved CVR in patients with carotid artery disease as shown by the absolute and hemispheric asymmetry of BOLD response to hypercapnia.. These findings show that benefits from recanalisation may go beyond removal of the embolic source, by improving the cerebrovascular reserve. Moreover, hypercapnia BOLD fMRI may be a useful clinical tool in predicting this therapeutic potential in patients with severe carotid artery disease.

0 Bookmarks
 · 
66 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The functional imaging of perfusion enables the study of its properties such as the vasoreactivity to circulating gases, the autoregulation and the neurovascular coupling. Downstream from arterial stenosis, this imaging can estimate the vascular reserve and the risk of ischemia in order to adapt the therapeutic strategy. This method reveals the hemodynamic disorders in patients suffering from Alzheimer's disease or with arteriovenous malformations revealed by epilepsy. Functional MRI of the vasoreactivity also helps to better interpret the functional MRI activation in practice and in clinical research.
    Diagnostic and interventional imaging. 09/2013;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Association between preoperative perfusion pattern and reperfusion after carotid endarterectomy (CEA) is an important yet unexplored topic. Therefore, the aim of our study was to determine whether 99mTc-ECD single-photon emission computed tomography (SPECT) performed before carotid endarterectomy in patients with internal carotid artery (ICA) stenosis may be helpful in predicting early perfusion changes after revascularization. The examined group consisted of 30 patients (mean age 67.4±9.6 years) with ICA stenosis who underwent CEA. Infarction was demonstrated on computed tomography (CT) in 12 cases. Brain perfusion SPECT was performed 1-3 days before CEA and 3-5 days after the surgery. Voxel-based analysis was carried out with Brain SPECT Quantification software. For evaluation of preoperative interhemispheric asymmetry of perfusion, the percentage asymmetry index (AI) was calculated. For comparison of perfusion before and after CEA, the percentage relative difference (RD) was computed. Before CEA, cerebral hypoperfusion was seen in 26 cases, including 15 participants with normal CT. After CEA, the following changes of perfusion were observed: perfusion increase n=18 (ipsilateral and bilateral), deterioration n=1, mixed patterns n=2, no change n=9. In patients with preoperative ipsilateral hypoperfusion and perfusion increase after CEA, AI correlated significantly with RD (r=0.48, p=0.04). Our results suggest that perfusion increase 3-5 days after CEA is higher in patients with greater ipsilateral asymmetry index. Evaluation of preoperative AI may help to identify patients in whom rapid reperfusion is more likely.
    Medical science monitor: international medical journal of experimental and clinical research 05/2011; 17(5):CR297-303. · 1.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The study aims to investigate the effect of cerebral ischemia or hypoperfusion in the evaluation of neural activity with blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI), and to examine whether the severity of the compromised hemodynamic status in patients with major cerebral artery diseases could, conversely, be assessed with the use of neural activity as endogenous vasodilator. 28 neurological impairment-free patients with anterior-circulation-territory ischemia performed a bimanual hand-grasping task. Magnitude and temporal shift of evoked BOLD response, baseline cerebral blood flow (CBF) and its increment, and the severity of hemodynamic impairment stratified by blood flow pattern were evaluated. For fMRI data, both conventional analysis with a canonical HRF and an HRF-model-free analysis were performed. The severity of hemodynamic impairment was significantly correlated (p<0.0001) with baseline CBF, CBF increment, and magnitude and delay of BOLD response. BOLD response delay was also significantly correlated (p<0.0001) with baseline CBF, CBF increment, and response magnitude. In 10 out of 45 ischemic motor cortices, conventional analysis completely failed to detect areas of activation that were demonstrated by HRF-model-free analysis. These data suggest that delay and reduced magnitude of BOLD response can be an indicator of the severity of compromised hemodynamic status, and that reduced regional baseline CBF and its increment underlie impaired BOLD response, which necessitates an alternative approach to conventional analysis with any single HRF.
    NeuroImage 04/2012; 61(3):579-90. · 6.25 Impact Factor

Full-text

View
31 Downloads
Available from
May 22, 2014