Assessment of Dynamic Cerebral Autoregulation in Patients with Basilar Artery Stenosis

Abstract

Background and AimsPrevious studies have shown impaired cerebral autoregulation (CA) in carotid and middle cerebral artery (MCA) stenosis/occlusion. Little is known about CA in patients with basilar artery (BA) stenosis. We therefore investigated dynamic CA patterns in BA stenosis using transfer function analysis (TFA).MethodsWe measured spontaneous oscillations of blood flow velocity (CBFV) in the right posterior cerebral artery (PCA), and left MCA and mean arterial pressure (ABP) continuously in 25 patients with BA stenosis (moderate n=16 with 50-69% occlusion and severe n=9 with ≥70% occlusion) and 22 healthy volunteers in supine position during 6 circles per minute deep breath. Analysis was based on the ‘black-box’ model of transfer function deriving phase and gain in both PCA and MCA.ResultsThough changes of phase shift and gain between the patients and healthy controls were observed in MCA, the differences are however not significant. Phase shift in PCA was significantly decreased in severe stenosis when comparing with healthy controls and moderate stenosis (4.2±34.2° VS 41.1±40.4°, 4.2±34.2° VS 34.2±27.2°, both p<0.05), whilst the gain in PCA is increased for moderate BA stenosis and decreased for severe BA stenosis. Furthermore, we found that phase shift were almost abolished in patients with ischemic stroke who developed unfavorable clinical outcome (mRs>2) on the 90 days after stroke onset.ConclusionDynamic CA in PCA reduces in patients with severe BA stenosis and those with ischemic stroke who present poor outcome in 90 days after stroke onset. Phase shift might be a sensitive index prompting impaired CA in posterior circulation.

Assessment of cerebral autoregulation in stroke: A systematic review and meta-analysis of studies at rest

“…The majority of existing studies on dCA disturbances during the acute stage of stroke report that worse dCA within a week after onset may be predictive of poor clinical outcomes. 27,29,32,36,37,43,46 Although there are currently standardized recommendations for measuring TFA in the context of dCA research, 14 this tends to apply only to healthy studies. TFA is a non-invasive technique that can be applied safely and easily to a wide range of clinical conditions, but there is currently no systematic review with associated meta-analysis of TFA for assessment of dCA in neurological applications.…”

“…13, 24, 27, 29, 32, 35-38, 43, 46 Moreover, the majority of participants were recruited within 6 to 72 hours from stroke onset, 2, 12, 13, 24-27, 29, 34-40, 42, 43, 45-47, 49, 51 including within 48 hours (n = 8), 2, 25, 34-36, 39, 47, 49 five studies assessed dCA at 72 hours, 24,29,40,45,51 twenty-four hours were studied in four studies, 37,42,43,46 three studies examined dCA between 30 to 37 hours, 12,13,38 dCA was assessed at 6 hours (n = 2), 26,27 one study assessed between onset to 16 days, 52 other three studies recruited participants after first week of stroke onset 32,33,48 and one study examined recovery at 6 months. 49 The location of the lesion was identified in the MCA (n = 13), 23, 26-28, 33-37, 40, 41, 49, 51 posterior cerebral artery (n = 3), 31,32,49 and anterior cerebral artery territories (n = 3), 2, 25, 52 though eight studies did not specify the precise localization of the lesion. 12,13,24,29,38,39,48,50 Five studies of ICH recruited participants for dCA testing within 48 hours of onset, 42,43,[45][46][47] with the exception of one study which assessed at 4-6 days after onset.…”

“…reporting unit of gain as cm/s/mmHg, 23,32,35,38,41,47,49,50,52 six studies as %/%, 29,31,33,39,43,46 four studies as %/mmHg, 27,45,48,50 with dB and amplitude used for one study each. 28,40 Two units were used for phase with twenty four studies presenting degrees 23, 24, 26-36, 39, 41-44, 46, 47, 49, 51, 52 and four studies using radians.…”

Cerebral Autoregulation

“…Although there was no significant change in phase shift and gain between Basilar Artery (BA) stenosis subjects and controls in the MCA, phase angle decreased significantly in severe stenosis ( 70 % occlusion) subjects in the PCA and the gain in the PCA increased for moderate BA stenosis (50-69 % occlusion) subjects and decreased for severe BA stenosis, Gong et al (2013).…”

Partial pharmacologic blockade shows sympathetic connection between blood pressure and cerebral blood flow velocity fluctuations

“…Cerebral autoregulation (CA) assures constant cerebral blood flow in the face of changing blood pressure (BP) [1,2], and is altered in neurovascular disorders [3][4][5][6][7]. Under physiologic conditions, various components, such as myogenic, endothelial and neurogenic, primarily sympathetic mechanisms, contribute to dampening the transfer of BP fluctuations onto CBFV [8][9][10].…”