Article

Impaired cerebrovascular reactivity with steal phenomenon is associated with increased diffusion in white matter of patients with Moyamoya disease.

Department of Medical Imaging, Toronto Western Hospital, Toronto, Ontario, Canada.
Stroke (Impact Factor: 6.16). 08/2010; 41(8):1610-6. DOI: 10.1161/STROKEAHA.110.579540
Source: PubMed

ABSTRACT Reduced cerebrovascular reactivity (CVR) with steal phenomenon is an independent predictor for stroke and may indicate tissue exposed to episodic low-grade ischemia. The apparent diffusion coefficient (ADC) calculated using diffusion-weighted MRI is effective in characterizing focal brain ischemia and subtle structural changes in normal-appearing white matter (WM). We hypothesized that regions of steal phenomenon are associated with increased ADC in normal-appearing WM of patients with Moyamoya disease.
Twenty-two patients with unilateral CVR impairment secondary to Moyamoya disease and 12 healthy control subjects underwent diffusion-weighted MRI and functional MRI mapping of the cerebrovascular response to hypercapnia. Parametric maps of ADC and CVR were calculated, coregistered, and segmented using automated image processing methods. ADC of normal-appearing WM was compared between hemispheres, and between WM with negative CVR (ie, steal phenomenon) and WM with positive CVR.
In patients, ADC of normal-appearing WM was elevated in the hemisphere ipsilateral to the CVR impairment compared with the contralateral hemisphere (P<0.005) and in WM with negative CVR compared with WM with positive CVR (P<0.001). WM in regions of steal phenomenon within the affected hemisphere had higher ADC than homologous contralateral WM (P<0.005). In control subjects, negative CVR in WM was not associated with elevated ADC.
Regions of steal phenomenon are spatially correlated with elevated ADC in normal-appearing WM of patients with Moyamoya disease. This structural abnormality may reflect low-grade ischemic injury after exhaustion of the cerebrovascular reserve capacity.

0 Bookmarks
 · 
181 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chronic, repetitive, and sublethal hypoperfusion by intra- or extracranial artery stenosis promotes collateral development and conditions the brain toward preventing subsequent lethal ischemia, although these latent properties have rarely been demonstrated in the clinical setting. This study assessed the previously unexplored role of subclavian steal syndrome (SSS) on inciting and protecting brain damage. We enrolled patients diagnosed with SSS associated with subclavian artery stenosis. Subclavian steal was determined by transcranial Doppler and/or digital subtraction angiography. We analyzed the prevalences and predictors of posterior ischemic symptoms and infarcts in SSS patients and also investigated individual cases to demonstrate a clinical evidence of brain conditioning, focusing on cytotoxic and vasogenic edema. Of 54 SSS patients, 36 (66.7%) had been asymptomatic and incidentally diagnosed with SSS, whereas 18 (33.3%) patients had presented with posterior ischemic symptoms. Symptoms and infarcts including old silent lesions occurred more frequently as unstable hemodynamics of the anterior circulation were combined. Of 18 symptomatic patients, 13 patients (72.2%) had transient ischemic attack and 5 (27.8%) patients had an infarct in the posterior circulation territory. Four patients with cytotoxic edema had mild neurologic deficits and rapid and complete recovery, whereas 1 patient had prolonged, severe vasogenic edema after acute hypertension. Although we noted low rates of disabling or fatal strokes in patients with SSS, a variety of vascular and neural factors beyond severity of subclavian steal could influence the likelihood of brain damage.
    Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 10/2013;
  • [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: Background and PurposeCerebrovascular reactivity (CVR), measures the ability of the cerebrovasculature to respond to vasoactive stimuli such as CO2. CVR is often expressed as the ratio of cerebral blood flow change to CO2 change. We examine several factors affecting this measurement: blood pressure, stimulus pattern, response analysis and subject position.Methods Step and ramp increases in CO2 were implemented in nine subjects, seated and supine. Middle cerebral artery blood flow velocity (MCAv), and mean arterial pressure (MAP) were determined breath-by-breath. Cerebrovascular conductance (MCAc) was estimated as MCAv/MAP. CVR was calculated from both the relative and absolute measures of MCAc and MCAv responses.ResultsMAP increased with CO2 in some subjects so that relative CVR calculated from conductance responses were less than those calculated from CVR calculated from velocity responses. CVR measured from step responses were affected by the response dynamics, and were less than those calculated from CVR measured from ramp responses. Subject position did not affect CVR.Conclusions(1) MAP increases with CO2 and acts as a confounding factor for CVR measurement; (2) CVR depends on the stimulus pattern used; (3) CVR did not differ from the sitting versus supine in these experiments; (4) CVR calculated from absolute changes of MCAv was less than that calculated from relative changes.
    Brain and Behavior. 08/2014;