Recovery of cerebrovascular reactivity after treatment of asymptomatic carotid artery stenosis is assessable by non-invasive breath-hold fMRI within global watershed areas

Background: Treatment of asymptomatic internal carotid artery stenosis (ICAS) patients remains still controversial [1]. Hemodynamic biomarkers such as the cerebrovascular reactivity (CVR) are promising to identify patients who benefit from revascularization precedures [2–4]. However, commonly employed methods are invasive acetazolamide or complicated gas applications [2–6]. The aim of our study was therefore to measure CVR recovery in ICAS-patients after treatment by easily-applicable breath-hold fMRI (BH-fMRI) with increased sensitivity by evaluation within global watershed areas (gWSAs) [7].
Methods: Thirty-three participants (16 asymptomatic, unilateral ICAS-patients, age = 71.4 ± 5.8y, and 17 healthy controls [HC], age = 70.8 ± 5.3y, see Fig. 1) underwent MRI on a 3T Philips Ingenia.
All participants were scanned twice, patients before and at least three months after treatment, HC at similar follow-up delays. BH-fMRI comprised five breath-holds à 15s each; CVR-maps were calculated by data-driven analysis [8] (Fig. 2a, b). Lateralization of CVR was calculated in GM of gWSAs between hemispheres for each participant (Fig. 2c).
Result: Exemplary ICAS-patient’s data shows impaired CVR before treatment, which recovered after treatment (Fig. 1A,B). On group level, CVR was significantly impaired ipsilateral to the stenosis before treatment (Fig. 3a, t-test, p = 0.0038). After treatment, CVR significantly recovered (2-sample t-test, p = 0.0495) resulting in symmetrical CVR between hemispheres (t-test, p = 0.25). HC data was symmetrical between hemispheres (Fig. 3b, p > 0.60).
Discussion: BH-fMRI based evaluation within gWSAs was sensitive to CVR impairments in asymptomatic ICAS, indicating chronic vasodilation [5]. Specificity was affirmed by symmetrical HC results. Consistent with current literature, CVR recovered after ICAS-treatment [4–7], demonstrating improved hemodynamic status.
Conclusion: We successfully analyzed CVR recovery after ICAS treatment by easily applicable, tolerable and non-invasive BH-fMRI within clinically feasible scan times. This technique could potentially improve future treatment decisions.