Directional Sensitivity of Dynamic Cerebral Autoregulation in Alzheimer’s Disease and Mild Cognitive Impairment
Nikita Kalidas, Ronney B Panerai, Lucy BeishonIntroduction:
Directional sensitivity of dynamic cerebral autoregulation refers to greater efficiency in counteracting increases in mean arterial pressure than decreases in it, thereby protecting the brain against hypertensive surges. Directional sensitivity may be affected in Alzheimer’s disease and mild cognitive impairment.
Methods:
This retrospective study analysed data from healthy controls (n=30) and individuals with Alzheimer’s disease (n=35) and mild cognitive impairment (n=22). Continuous cerebral blood velocity (CBv) and beat-to-beat mean arterial pressure were recorded during 5 minutes of rest. CBv responses to spontaneous mean arterial increases (MAP+D) and decreases (MAP-D) were assessed over 15 s (T1: 0-5s, T2: 5-10s, T3: 10-15s). The primary outcome explored directional sensitivity strength, quantified as the difference in CBv responses (ΔT1, ΔT2, ΔT3) and autoregulatory index (ΔARI) between MAP+D and MAP-D. The secondary outcome examined the separate autoregulatory response during positive and negative MAP derivatives.
Results:
Diagnosis was not significantly associated with any of the primary DSCA strength measures. However, diagnosis was significantly associated with ARI during MAP+D (p=0.030). Healthy controls showed significantly higher autoregulatory efficiency in response to MAP+D compared to individuals with mild cognitive impairment (p=0.003).
Discussion:
Although DSCA strength did not differ between diagnostic groups, individuals with early cognitive impairment showed alterations in autoregulatory efficiency during spontaneous BP rises that might reflect selective impairment of myogenic (vasoconstrictive) dCA pathways.
Conclusion:
These findings suggest altered dynamic cerebral autoregulatory efficiency in response to increases in mean arterial pressure in mild cognitive impairment, despite preserved directional sensitivity strength.