Age-related differences in cerebrovascular responses to cognitive stimulation using a novel method.

Aging is associated with a number of alterations to cerebrovascular function. We aimed to investigate the effect of age on cerebrovascular responses to cognitive stimulation using an objective two-parameter method.Previously derived from a large data-set (135 healthy participants) were applied to a task-activated dataset of 69 healthy participants in five different task conditions. Cumulative response rate (CRR) was calculated as the sum of responses across tasks and hemispheres.There was a significant effect of age (adjusted odds ratio: 1.02 (95% confidence interval: 1.01, 1.04), p = 0.016). There was also a significant effect of task (p = 0.002), but there was no significant interaction between age and task (p = 0.37). Increasing age was associated with increased CRR (adjusted odds ratio: 1.04 (95% confidence interval: 1.01, 1.07), p = 0.009).Using an objective two-parameter method, healthy older adults had increased cerebrovascular responses to cognitive testing.

Extremes of cerebral blood flow during hypercapnic squat-stand maneuvers.

Squat-stand maneuvers (SSMs) are a popular method of inducing blood pressure (BP) oscillations to reliably assess dynamic cerebral autoregulation (dCA), but their effects on the cerebral circulation remain controversial. We designed a protocol whereby participants would perform SSMs under hypercapnic conditions. Alarmingly high values of cerebral blood flow velocity (CBFV) were recorded, leading to early study termination after the recruitment of a single participant. One healthy subject underwent recordings at rest (5 min sitting, 5 min standing) and during two SSMs (fixed and random frequency). Two sets of recordings were collected; one while breathing room air, one while breathing 5% CO2 . Continuous recordings of bilateral CBFV (transcranial Doppler), heart rate (ECG), BP (Finometer), and end-tidal CO2 (capnography) were collected. Peak values of systolic CBFV were significantly higher during hypercapnia (p < 0.01), and maximal values exceeded 200 cm.s-1 . Estimates of dCA (ARI) during hypercapnia were impaired relative to poikilocapnia (p = 0.03). The phase was significantly reduced under hypercapnic conditions (p = 0.03). Here we report extremely high values of CBFV in response to repeated SSMs during induced hypercapnia, in an otherwise healthy subject. Our findings suggest that protocols performing hypercapnic SSMs are potentially dangerous. We, therefore, urge caution if other research groups plan to undertake similar protocols.

An objective method to identify non-responders in neurovascular coupling testing.

BACKGROUND: Neurovascular coupling (NVC) can be assessed using transcranial Doppler (TCD) measured task-activation of cerebral blood flow velocity (CBFv). However, not all individuals show consistent responses. The aim of this study was to develop a robust, objective, method to identify non-responders to task-activation. NEW METHOD: Using five-minute seated resting (non-stimulated), bilateral CBFv data from 135 healthy participants, the cross-correlation function peak (CCF) between the population coherent average and each individual was obtained for a randomly selected segment of data (40 s) for both hemispheres (n = 270). The variance ratio (VR) was calculated by comparing the variance in CBFv data pre- and post-random mark. The 90th percentile for non-stimulated data was used to determine the upper confidence limit of normal variation in the CCF peak value (0.53), and VR (2.59). These criteria were then applied to task-activated CBFv from 69 healthy participants for five cognitive tasks (attention, verbal fluency, language, visuospatial, memory). RESULTS: Data were accepted as responders if either CCF ≥ 0.53 or VR ≥ 2.59. The number of cases accepted as responders for each task were as follows: attention, 54-59 (78-86 %); verbal fluency, 42-48 (60-70 %); language, 51-53 (74-77 %); visuospatial, 54 (78 %); memory, 40-47 (58-68 %). COMPARISON WITH EXISTING METHOD: Currently, there are no objective criteria for the identification of non-responders in studies of NVC. This is a new method to objectively classify non-responders to task-activation. CONCLUSIONS: Using a large sample of resting CBFv data, we have set objective criteria to differentiate between responders and non-responders in task activation protocols.

Agreement between patient-based and clinician-based assessment of the shoulder.

BACKGROUND: Patient home-based self-assessments after shoulder surgery have the potential to aid clinicians in reducing clinic time and decreasing follow-up requirements. The purpose of this systematic review was to determine the correlation between patient-based and physician-assessed outcome measures for range of motion (ROM), strength, and shoulder function. METHODS: This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. MEDLINE, Embase, CINAHL, and Cochrane Central Register of Controlled Trials databases were searched. All studies comparing patient-reported and clinician-based assessments of shoulder ROM, strength, and function were eligible for inclusion. Studies that included patient or clinician assessment only, description of shoulder diseases or treatments only, and animal- or cadaveric-based studies were excluded. More than 250 abstracts were searched, and 4 studies were found eligible. RESULTS: Patients assessed their shoulder ROM, strength, and function with moderate-to-high accuracy compared with clinical assessment. There was less agreement between patients and clinicians regarding the symptomatic shoulder compared with the contralateral shoulder. There was less agreement between patients and clinicians on rotation than forward elevation. Patients who were less satisfied with their shoulder had less agreement with clinicians. CONCLUSION: There is moderate-to-high agreement between patients and clinicians in the assessment of the shoulder after surgery. Methods of assessment of rotation could be reviewed to create a more exact self-assessment tool.