Imaging cognitive fatigability in multiple sclerosis: objective quantification of cerebral blood flow during a task of sustained attention using ASL perfusion fMRI.

Cognitive fatigability (CF) can be defined as an inability to maintain performance throughout a sustained cognitive task. Individuals with multiple sclerosis (MS) are more susceptible to CF than healthy controls (HCs); however, the neural correlates underlying CF are still under investigation. Arterial spin labeling (ASL) perfusion imaging provides a non-invasive method of objectively quantifying cerebral blood flow (CBF) during sustained attention tasks. To date, no study has yet evaluated CF in MS using this methodology. 10 MS and 10 HCs completed a 20-min psychomotor vigilance task (PVT). CF was evaluated by dividing the PVT into quintiles and examining performance from the 1st to the last. Mean reaction times (RTs) and number of lapses were recorded. Global and regional CBF changes were evaluated throughout the PVT as well as during pre- and post-task rest. Increased susceptibility to CF was noted in the MS group. Distinct patterns of CBF activation were observed in areas comprising fronto-parietal, cortico-striatal, cerebellar, and basal ganglia regions; however, when and how these regions were engaged differed between the MS and HC groups. In particular, dysfunction in CBF to the middle frontal gyrus may underlie the CF effects observed. In addition, individuals with MS appear to struggle with "switching off" regions of the attentional network at rest following sustained cognitive effort. Findings support the use of ASL as an appropriate methodology for evaluating CF in MS with an overall pattern of attentional network dysfunction being observed. Objectively quantifying CF in this manner can help validate patients' subjective complaints.

Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS): Canadian contribution to the international validation project.

BACKGROUND: Given the high prevalence of cognitive dysfunction in people with multiple sclerosis (PWMS) and the lack of availability of specialized neuropsychological services in most MS Clinics, there is a need for a brief cognitive monitoring tool that can be easily administered by MS clinic staff. OBJECTIVE: We aimed to establish the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) as a feasible cognitive monitoring tool and provide Canadian data toward the international validation effort. Secondary considerations were to determine if BICAMS correlates with self-reported cognition and predicted vocational status. METHODS: 57 PWMS were matched to 51 healthy controls (age, sex, education). Participants completed the BICAMS battery which includes the Symbol Digit Modalities Test, and the learning trials from the California Verbal Learning Test-II and the Brief Visuospatial Memory Test-Revised. Depression, self-reported cognition, and fatigue were assessed. Participants were re-tested 15.6 (SD 2.0) days later. RESULTS: With impairment defined as "one or more abnormal tests," 57.9% of MS sample was cognitively impaired. Participants were more likely to be impaired on the BVMT-R (43.9%). On the SDMT and CVLT-II, 28.1% and 26.3% of MS participants were impaired. Sensitivity and specificity were highest for the SDMT. The BICAMS was reliable over time (r value range from 0.69 for BVMT-R to 0.87 for SDMT) with the SDMT being most robust. There was no relationship between BICAMS and subjective cognition. The BVMT-R reliably predicted employment. CONCLUSIONS: The BICAMS detected cognitive impairment to a comparable degree to more comprehensive neuropsychological batteries and is a valid measure of cognition in MS. Reliability of components varies, suggesting care be taken when interpreting serial testing results. The BICAMS is a feasible cognitive assessment tool in Canadians and yields comparable results to other cultures.