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

- Classical cognitive tests do not consider the neurovascular coupling (NVC) response.
- NVC has not been previously challenged with novel paradigms from cognitive tests.
- Transcranial Doppler (middle cerebral artery) validated novel paradigm responses.
- Novel paradigms elicited similar responses to more established paradigms.
- Clinical assessment of cognitive loss could be improved with matched NVC testing.

BackgroundWe 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 methodHealthy 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.ResultsForty 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 methodsFor established paradigms, our results are in excellent agreement to what has been found previously in the middle cerebral artery.ConclusionsCognitive 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.