Autonomic dysfunction in mild cognitive impairment: a transcranial Doppler study.
OBJECTIVE
The contribution of early microvascular and autonomic derangements to the pathogenesis of mild cognitive impairment (MCI) is unclear. Aim of this study is to evaluate cerebrovascular reactivity (CVR) and cardiac autonomic function in patients with MCI by means of transcranial Doppler (TCD).


METHODS
Fifteen patients with MCI and 28 controls underwent carotid ultrasound and TCD evaluation, including assessment of mean flow velocity (MFV) in the middle cerebral artery at baseline, after CO(2) inhalation and after hyperpnoea. End-tidal CO(2) , mean arterial blood pressure (MAP), heart rate (HR), and respiratory rate were monitored throughout the procedure, and CVR was calculated.


RESULTS
MAP, end-tidal CO(2) , and MFV variations during hypercapnia and hyperventilation showed no between-group differences. CVR was similar in controls and MCI (2.30 vs 2,39, respectively, P = 0.767). HR significantly increased in hypercapnia (+9.4%, P < 0.0001) and hyperventilation (+18.7%, P < 0.0001) in controls, while in MCI it significantly increased in hyperventilation (+10.4%, P = 0.002), but not in hypercapnia (+1.1%, P = 0.635).


CONCLUSIONS
This study demonstrates that patients with MCI have a normal CVR, but they exhibit signs of autonomic dysfunction after CO(2) challenge. Should this finding be confirmed in larger studies, HR response to CO(2) challenge could become a marker of MCI.
Service of Neurology, S. Orsola Hospital, Brescia, Italy. gianpaolo.anzola@poliambulanza.it
G P
GP
Anzola
S
S
Galluzzi
S
S
Mazzucco
G B
GB
Frisoni
D000368:Aged; D001342:Autonomic Nervous System Diseases / Q000150:complications* / Q000000981:diagnostic imaging*; D001783:Blood Flow Velocity / Q000502:physiology; D060825:Cognitive Dysfunction / Q000150:complications*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D006985:Hyperventilation / Q000503:physiopathology; D008297:Male; D017585:Ultrasonography, Doppler, Transcranial; D014655:Vascular Resistance / Q000502:physiology