Abstract
For the prognosis of stroke, patients with moyamoya disease (MMD) require the estimation of remaining cerebrovascular reactivity. For this purpose, CO2-triggered BOLD fMRI by use of short breath-hold periods seems to be a highly available alternative to nuclear medicine methods. Too long breath-hold periods are difficult to perform, too short breath-hold periods do not lead to sufficient BOLD signal changes. We aimed to investigate the required minimum breath-hold duration to detect distinct BOLD signals in the tissue of healthy subjects to find out how long the minimum breath-hold duration in clinical diagnostics of MMD should be. A prospective study was performed. Fourteen healthy subjects underwent fMRI during end-expiration breath-hold periods of different duration (3, 6, 9, and 12 s). Additionally, we compared the influence of paced and self-paced breathing altering the breath-hold periods. Data of a patient with MMD was evaluated to investigate whether the tested procedure is suitable for clinical use. Significant global BOLD signal increases were detected after breath-hold periods of 6, 9, and 12 s. The signals were significantly higher after breath-hold periods of 9 s than after 6 s, while not when the duration was extended from 9 to 12 s. Furthermore, we found additional BOLD signal changes before the expected signal increases, which could be avoided by paced respiratory instructions. This investigation indicates that end-expiration breath-hold period of at least 9 s might be used to measure the cerebrovascular reactivity. This time period resulted in distinct BOLD signal changes and could be performed easily.
Highlights
Moyamoya disease (MMD) is a cerebrovascular disease that leads to progressive stenosis of terminal parts of the internal carotid arteries (ICA) and the circulus of Willis
One of the major findings of this study is that significant global BOLD responses can be detected after BH periods of 6, 9, and 12 s, whereas BH periods of 3 s do not induce significant global signal increases
Another important finding is that the BOLD signals after BH periods of 9 s were significantly higher than after BH periods of 6 s, while the extension from 9 to 12 s revealed no significant additional signal increase
Summary
Moyamoya disease (MMD) is a cerebrovascular disease that leads to progressive stenosis of terminal parts of the internal carotid arteries (ICA) and the circulus of Willis. The reactively formed collateral vessels serving to maintain the cerebral blood flow (CBF) remind on angiograms of MMD patients. In vascular territories with insufficient CVR, reduced increase in perfusion during hypercapnic stimulation is expected, as the vessels are chronically in a state of maximum dilatation to maintain cerebral blood flow. In patients with MMD, the BOLD signal increase is not supposed to be observed in the pathological vascular territories. Breath-hold technique can be a wellpracticable method to achieve hypercapnia. It is noninvasive and does not require any additional equipment [14, 15], but leads to similar BOLD signal changes as the inhalation of CO2-enriched gas mixtures [15]
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