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Recovery of cerebrovascular reactivity after treatment of asymptomatic carotid artery stenosis is assessable by non-invasive breath-hold fMRI within global watershed areas
Kaczmar, S.; Goettler, J.; Sollmann, N.; Hock, A.; Sorg, C.; Zimmer, C.; Mouridsen, K.; Hyder, F.; Preibisch, C.; Petr, J.;
Objectives
Accounting for approximately 10% of all strokes,1 severe internal carotid-artery stenosis (ICAS) is a major public health issue. The average 2-year mortality after the invasive treatment is very high with 32%,2 which creates the need for non-invasive methods to support treatment decisions and evaluate treatment efficacy.3,4 A highly promising biomarker of vascular health is cerebrovascular reactivity (CVR),3,4 however, commonly employed methods are either invasive acetazolamide injections or complicated gas applications.3-8 We therefore used an easily-applicable breath-hold fMRI (BH-fMRI) scheme for CVR measurements. To maximize sensitivity and ensure specificity, we evaluated CVR within global watershed areas (gWSAs) in ICAS-patients before and after treatment and in healthy controls (HC).9

Methods
Thirty-three participants (16 asymptomatic, unilateral ICAS-patients, age = 71.4 ± 5.8 y and 17 HC, age = 70.8 ± 5.3 y) underwent MRI on a 3 T Philips Ingenia with written informed consent. All participants were scanned twice, patients before and at least three months after treatment (by stenting or endarterectomy), HC with a similar follow-up delay. The BOLD-based BH-fMRI scheme comprised five breath-holds of 15 s, each. CVR-maps were calculated by data-driven analysis10 (Fig.1B,C). Artefact-affected CVR-maps were excluded based on visual ratings (CP,SK,JG). To investigate the role of chronic vasolidation,5 dynamic susceptibility contrast (DSC) MRI was additionally acquired in both scans to calculate relative cerebral blood volume (rCBV) maps11. Lateralization between hemispheres was calculated in MNI-space by mean parameter-values within GM of gWSAs for each participant (Fig.1A). ICAS-patients were evaluated within hemispheres ipsilateral and contralateral to the stenosis.

Results
Exemplary data of an ICAS-patient shows impaired CVR before treatment, which improves after treatment (see arrows in Fig.1B,C). On group level, CVR is significantly decreased in the ipsilateral hemisphere before treatment (Fig.1D, p = 0.0038). After treatment, CVR lateralization was significantly reduced (p = 0.0495) towards more symmetrical values between hemispheres (p = 0.25). Similarly, rCBV was ipsilaterally increased in ICAS before treatment and more symmetrical after treatment (data not shown). HC data was symmetrical between hemispheres at all scans (Fig.1E, p > 0.60).

Discussion
As hypothesized, BH-fMRI based evaluation of CVR lateralization within gWSAs was sensitive to subtle impairments in asymptomatic ICAS without compromising its specificity, as affirmed by symmetrical HC results (Fig.1E). Decreased CVR along with increased rCBV before treatment is associated with chronic vasodilation.5 Consistent with current literature, CVR recovery was detected after ICAS-treatment,4-8 demonstrating improved haemodynamic status. Compared to more accurate CVR-measurements with CO2 application and end-tidal gas analysis,3,12 breath-holds remain a viable alternative being much more tolerable and easily applicable at low costs within clinically feasible scan times.
  • Contribution to proceedings
    The 29th International Symposium on Cerebral Blood Flow, Metabolism and Function, 04.07.2019, Yokohama, Japan
  • Poster
    The 29th International Symposium on Cerebral Blood Flow, Metabolism and Function, 04.07.2019, Yokohama, Japan

Publ.-Id: 29521 - Permalink