Service of Neurology, S. Orsola Hospital, Brescia, Italy.
Acta Neurol Scand. 2011 Dec;124(6):403-9. doi: 10.1111/j.1600-0404.2011.01495.x. Epub 2011 Feb 25.
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).
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.
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).
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.
早期微血管和自主功能紊乱对轻度认知障碍（MCI）发病机制的影响尚不清楚。本研究旨在通过经颅多普勒（TCD）评估 MCI 患者的脑血管反应性（CVR）和心脏自主功能。
15 例 MCI 患者和 28 例对照者接受颈动脉超声和 TCD 评估，包括在基线、CO2 吸入后和过度通气后评估大脑中动脉平均血流速度（MFV）。整个过程中监测呼气末 CO2、平均动脉压（MAP）、心率（HR）和呼吸频率，并计算 CVR。
CO2 吸入和过度通气期间的 MAP、呼气末 CO2 和 MFV 变化在两组之间无差异。对照组和 MCI 组的 CVR 相似（分别为 2.30 和 2.39，P = 0.767）。对照组在 CO2 吸入时 HR 显著增加（+9.4%，P < 0.0001），在过度通气时 HR 显著增加（+18.7%，P < 0.0001），而 MCI 组在过度通气时 HR 显著增加（+10.4%，P = 0.002），但在 CO2 吸入时 HR 无显著增加（+1.1%，P = 0.635）。
本研究表明，MCI 患者的 CVR 正常，但在 CO2 挑战后表现出自主功能障碍的迹象。如果在更大的研究中证实这一发现，CO2 挑战时的 HR 反应可能成为 MCI 的标志物。
