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.
Highlights
Transcranial Doppler (TCD) is a safe and non-invasive technique for assessing hemodynamics of cerebral blood flow especially in evaluation of cerebral autoregulation [1,2]
CBFV in posterior cerebral artery (PCA) is significantly reduced in patients with severe basilar artery (BA) stenosis, which is similar to the situation in pulsatility index (PI) in PCA, implying normal perfusion in the PCA can possibly be maintained until the occlusion is severe
Though the stenosis is occurred in BA, cerebral autoregulation might be affected remotely in middle cerebral artery (MCA) as both gain and phase shift for MCA are changed
Summary
Transcranial Doppler (TCD) is a safe and non-invasive technique for assessing hemodynamics of cerebral blood flow especially in evaluation of cerebral autoregulation [1,2]. Characteristics of dynamic CA on carotid and middle cerebral artery have been described widely, while the knowledge of dynamic cerebral autoregulation (dCA) on posterior circulation remains scarce. This is of great concern, as high incidence of intracranial artery stenosis in Asian populations and high risk of stroke in posterior circulation [11]. Methods: We 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. Phase shift might be a sensitive index prompting impaired CA in posterior circulation
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