No abstract

Blood oxygenation level-dependent (BOLD) or arterial spin labeling (ASL) MRI with hypercapnic stimuli allow for measuring cerebrovascular reactivity (CVR). Hypercapnic stimuli are also employed in calibrated BOLD functional MRI for quantifying neuronally-evoked changes in cerebral oxygen metabolism (CMRO2). It is often assumed that hypercapnic stimuli (with or without hyperoxia) are iso-metabolic; increasing arterial CO2 or O2 does not affect CMRO2. We evaluated the null hypothesis that two common hypercapnic stimuli, ‘CO2 in air’ and carbogen, are iso-metabolic. TRUST and ASL MRI were used to measure the cerebral venous oxygenation and cerebral blood flow (CBF), from which the oxygen extraction fraction (OEF) and CMRO2 were calculated for room-air, ‘CO2 in air’ and carbogen. As expected, CBF significantly increased (9.9% ± 9.3% and 12.1% ± 8.8% for ‘CO2 in air’ and carbogen, respectively). CMRO2 decreased for ‘CO2 in air’ (−13.4% ± 13.0%, p < 0.01) compared to room-air, while the CMRO2 during carbogen did not significantly change. Our findings indicate that ‘CO2 in air’ is not iso-metabolic, while carbogen appears to elicit a mixed effect; the CMRO2 reduction during hypercapnia is mitigated when including hyperoxia. These findings can be important for interpreting measurements using hypercapnic or hypercapnic-hyperoxic (carbogen) stimuli.

OBJECTIVE Patients with moyamoya vasculopathy often experience cognitive impairments. In this prospective single-center study, the authors investigated the profile of neurocognitive impairment and its relation with the severity of ischemic brain lesions and hemodynamic compromise. METHODS Patients treated in a Dutch tertiary referral center were prospectively included. All patients underwent standardized neuropsychological evaluation, MRI, digital subtraction angiography, and [15O]H2O-PET (to measure cerebrovascular reactivity [CVR]). The authors determined z-scores for 7 cognitive domains and the proportion of patients with cognitive impairment (z-score < −1.5 SD in at least one domain). The authors explored associations between patient characteristics, imaging and CVR findings, and cognitive scores per domain by using multivariable linear regression and Bayesian regression analysis. RESULTS A total of 40 patients (22 children; 75% females) were included. The median age for children was 9 years (range 1–16 years); for adults it was 39 years (range 19–53 years). Thirty patients (75%) had an infarction, and 31 patients (78%) had impaired CVR (steal phenomenon). Six of 7 cognitive domains scored below the population norm. Twenty-nine patients (73%) had cognitive impairment. Adults performed better than children in the cognitive domain visuospatial functioning (p = 0.033, Bayes factor = 4.0), and children performed better in processing speed (p = 0.041, Bayes factor = 3.5). The authors did not find an association between infarction, white matter disease, or CVR and cognitive domains. CONCLUSIONS In this Western cohort, cognitive functioning in patients with moyamoya vasculopathy was below the population norm, and 73% had cognitive impairment in at least one domain. The cognitive profile differed between adults and children. The authors could not find an association with imaging findings.

Background: It remains unclear whether revascularization of moyamoya vasculopathy (MMV) has a positive effect on cognitive function. In this prospective, single-center study, we investigated the effect of revascularization on cognitive function in patients with MMV. We report clinical and radiological outcome parameters and the associations between clinical determinants and change in neurocognitive functioning. Methods: We consecutively included all MMV patients at a Dutch tertiary referral hospital who underwent pre- and postoperative standardized neuropsychological evaluation, [15O]H2O-PET (including cerebrovascular reactivity (CVR)), MRI, cerebral angiography, and completed standardized questionnaires on clinical outcome and quality of life (QOL). To explore the association between patient characteristics, imaging findings, and change in the z-scores of the cognitive domains, we used multivariable linear- and Bayesian regression analysis. Results: We included 40 patients of whom 35 (27 females, 21 children) were treated surgically. One patient died after surgery, and two withdrew from the study. TIA- and headache frequency and modified Rankin scale (mRS) improved (resp. p = 0.001, 0.019, 0.039). Eleven patients (seven children) developed a new infarct during follow-up (31%), five of which were symptomatic. CVR-scores improved significantly (p < 0.0005). The language domain improved (p = 0.029); other domains remained stable. In adults, there was an improvement in QOL. We could not find an association between change in imaging and cognitive scores. Conclusion: In this cohort of Western MMV patients, TIA frequency, headache, CVR, and mRS improved significantly after revascularization. The language domain significantly improved, while others remained stable. We could not find an association between changes in CVR and cognitive scores.