Reproducibility of task activation using the Addenbrooke's cognitive examination in healthy controls: A functional Transcranial Doppler ultrasonography study.

INTRODUCTION: Cerebral blood flow velocity (CBFv) changes occurring with cognitive stimulation can be measured by Transcranial Doppler ultrasonography (TCD). The aim of this study was to assess the reproducibility of CBFv changes to the Addenbrooke's cognitive examination (ACE-III). NEW METHOD: 13 volunteers underwent bilateral TCD (middle cerebral artery), continuous heart rate (HR, 3-lead ECG, Finometer), beat-to-beat mean arterial pressure (MAP, Finometer), and end-tidal CO2 (ETCO2, capnography). After 5min baseline, all ACE-III tasks were performed in 3 domains (A/B/C). Data presented are population CBFv peak normalised changes and area under the curve (AUC). Statistical analysis was by 2-way repeated measures (ANOVA), intra-class correlation coefficient (ICC), standard error of measurement (SEM) and coefficient of variation (CV). RESULTS: 12 bilateral data sets were obtained (10 right hand dominant, 6 female). Baseline parameters (MAP, HR, ETCO2) did not differ between visits. All tasks increased CBFv. Only domain A on AUC analysis differed significantly on ANOVA, and one task on post hoc testing (p <0.05). ICC values were poor (<0.4) for most tasks, but 3 tasks produced more consistent results on AUC and peak CBFv analysis (range ICC: 0.15-0.73, peak CV: 16.2-56.1(%), AUC CV: 23.2-60.2(%), peak SEM: 2.5-6.0 (%), AUC SEM: 21.8-135.8 (%*s). COMPARISON WITH EXISTING METHODS: This is the first study to examine reproducibility of CBFv changes to a complete cognitive assessment tool. CONCLUSIONS: Reproducibility of CBFv measurements to the ACE-III was variable. AUC may provide more reliable estimates than peak CBFv responses. These data need validating in patient populations.

Transcranial Doppler ultrasonography in the assessment of neurovascular coupling responses to cognitive examination in healthy controls: A feasibility study.

BACKGROUND: We tested the hypothesis that paradigms from the Addenbrooke's Cognitive Examination (ACE-III), including those that had not been studied using TCD previously (novel) versus those which had been (established), would elicit changes in CBF velocity (CBFv). NEW METHOD: Healthy subjects were studied with bilateral transcranial Doppler (TCD), beat-to-beat blood pressure (Finapres), continuous electrocardiogram (ECG), and end-tidal CO2 (nasal capnography). After a 5-min baseline recording, cognitive tests of the ACE-III were presented to subjects, covering attention (SUB7, subtracting 7 from 100 sequentially), language (REP, repeating words and phrases), fluency (N-P, naming words), visuospatial (DRAW, clock-drawing), and memory (MEM, recalling name and address). An event marker noted question timing. RESULTS: Forty bilateral data sets were obtained (13 males, 37 right-hand dominant) with a median age of 31 years (IQR 22-52). Population normalized mean peak CBFv% in the dominant and non-dominant hemispheres, respectively, were: SUB7 (11.3±9.6%, 11.2±10.5%), N-P (12.7±11.7%, 11.5±12.0%), REP (12.9±11.7%, 11.6±11.6%), DRAW (13.3±11.7%, 13.2±15.4%) and MEM (13.2±10.3%, 12.0±10.1%). There was a significant difference between the dominant and non-dominant CBFv responses (p<0.008), but no difference between the amplitude of responses. COMPARISON WITH EXISTING METHODS: For established paradigms, our results are in excellent agreement to what has been found previously in the middle cerebral artery. CONCLUSIONS: Cognitive paradigms derived from the ACE-III led to significant lateralised changes in CBFv that were not distinct for novel paradigms. Further work is needed to assess the potential of paradigms to improve the interpretation of cognitive assessments in patients at risk of mild cognitive impairment.