B-waves in healthy persons

The objective of this study was to determine, whether 0.5-2/min oscillations in intracranial pressure ('B-waves') are a physiological phenomenon. In a group of 5 patients 0.5-2/min oscillations of ventricular pressure simultaneous with oscillations in the middle cerebral artery (MCA) flow velocity, as assessed by transcranial Doppler sonography, were observed. Similar oscillations in MCA blood flow velocity were demonstrated in 8 out of 10 healthy subjects with an amplitude of about 10% of the mean flow velocity. We speculate that oscillations both in ventricular pressure and middle cerebral artery blood flow velocity are caused by rhythmic diameter changes of cerebral vessels with concomitant cerebral blood volume oscillations. Our data support the suggestion that B-waves may be physiological.     

脑静脉窦血栓经颅多普勒超声监测的临床意义

目的探讨经颅多普勒超声(TCD)监测上矢状窦血栓患者颅内压(ICP)的可行性,研究TCD动脉、静脉参数及频谱形态与ICP的关系,以指导临床治疗、评价疗效及判定预后。方法选择18例上矢状窦血栓形成住院患者,取入院第1、7及14天为观察点,动态监测患者的ICP、脑灌注压(CPP)、波动指数(PI)、阻力指数(RI)、大脑中动脉(MCA)和大脑中深静脉(dMCV)平均血流速度(Vm)以及TCD频谱形态,并与对照组相比较,同时进行相关性分析。结果上矢状窦血栓患者各观察点参数与对照组相比均有显著性差异(t=6.32,P<0.05),随着ICP的升高,患者的dMCV平均血流速度、PI及RI呈上升趋势,MCA平均血流速度和CPP呈下降趋势,在第7天达到高峰,持续到两周时略有恢复,但仍维持在较高水平。ICP与P1呈明显正相关(P<0.01,r=0.859);ICP与MCA-Vm呈明显负相关(P<0.01.r=-0.638);ICP与dMCV-Vm无相关性(r=0.07,P>0.05)。随着ICP的升高,动脉频谱表现为舒张期和收缩期血流的不同步下降,静脉频谱呈现血流升高的特征,表现为血流量与血管径的同步增加。结论TCD对临床可疑脑静脉窦血栓形成的患者是一种有效的筛选检测手段,TCD动态监测脑静脉窦血栓患者动脉和静脉血流的同步变化可以评估ICP增高的程度和脑部灌注情况,为临床治疗提供科学依据。     

急性脑梗死各临床亚型患者的脑血管反应性的变化

目的 探讨急性脑梗死各临床亚型患者脑血管反应性(CVR)的变化.方法 将70例急性脑梗死患者分为3个亚组:动脉硬化性血栓形成性脑梗死(AI)组(22例)、腔隙性脑梗死(LI)组(33例)和心源性脑梗死(CI)组(15例).应用经颅多普勒超声(TCD)检测各组患者双侧大脑中动脉(MCA)的平均流速(Vm)、脉动指数(PI)、阻力指数(RI)指标,通过屏气试验测定屏气指数(BHI);并与20名正常对照组进行比较. 结果与正常对照组相比,AI组Vm、PI、RI均显著升高(P<0.05～0.01),BHI明显降低(P<0.01);LI组Vm、BHI均显著降低(均P<0.05);而CI组各参数与正常对照组相比差异无统计学意义. 结论急性脑梗死各亚组的CVR改变并不相同,AI、LI组CVR损害更为明显,CVR检测对急性脑梗死各亚型的血液动力学研究有重要意义.     

Transcranial Doppler sonography evaluation of anterior cerebral artery hypoplasia or aplasia

BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) sonography is useful to evaluate intracranial arteries, however, interpretation of the TCD results in anterior cerebral artery (ACA) is difficult because of hypoplasia or aplasia. We try to define useful TCD indices and cut-off values to determine the variations of ACA. METHODS: Consecutive patients who underwent TCD and magnetic resonance angiography (MRA) were included. Patients with cerebrovascular abnormality or inadequate temporal windows were excluded. ACA status was classified as normal (NL), hypoplasia (HP), and aplasia (AP) according to MRA. TCD indices of mean flow velocity (MFV), pulsatility index (PI), ACA/middle cerebral artery (MCA) flow velocity ratio (ACA/MCA FVR), and asymmetry index (AI) of ACA were blindly compared with MRA between three groups. RESULTS: Two hundred and forty-one patients were included, and 193 patients (80%) were classified as NL, 34 (14%) as HP and 14 (6%) as AP. MFV was significantly lower in HP and AP (p<0.001), however, PI and ACA/MCA FVR were not different. AI was significantly different between NL and HP (21.5% vs. 50.4%), NL and AP (21.5% vs. 105.2%) (p<0.001). CONCLUSIONS: MFV of ACA should be interpreted with caution for its frequent anatomical variations. AI is useful to differentiate hypoplasia and aplasia from normal ACA with optimal criteria.     

大面积脑梗死脑血流动力学动态变化研究

目的探讨大面积脑梗死后颅内血流动力学动态的变化特点。方法对58例大面积脑梗死患者采用影像学供血模型分为完全MCA型和MCA皮质型,利用床旁经颅彩色多普勒（TCD）于入院当天和1周内隔日1次及第14天动态检测颅内血流情况,通过测定脑底动脉血流速度、搏动指数及血流速度比值（RVACA）,观察颅内血管血流动力学变化。结果大面积脑梗死病灶侧大脑中动脉（MCA）平均血流速度（Vm）、颈内动脉（ICA）平均血流速度均明显低于对照组（P〈0.05）,完全MCA型组较MCA皮质型组MCA血流速度明显减慢;完全MCA型与MCA皮质型梗死后动态观察MCA血流变化不明显,NIHSS评分及Pi在第3、5、7天较第1天明显增高（P〈0.05）,NIHSS评分变化最明显。结论大面积脑梗死患者可通过床旁TCD动态检测,及时发现侧支循环代偿及血管再通情况,评价颅内压动态变化,结合神经功能缺损评分,观察脱水降颅压治疗反应,为患者选择合适的治疗方案提供依据。     

Arterial pulsatility as an index of cerebral microangiopathy in diabetes

BACKGROUND AND PURPOSE: This study was designed to evaluate cerebral hemodynamic changes related to diabetes mellitus (DM) with transcranial Doppler ultrasonography (TCD). METHODS: We measured the flow velocities and the Gosling pulsatility index (PI) of the middle cerebral artery (MCA), extracranial internal carotid artery (ICA), and basilar artery (BA) in 56 stroke-free, normotensive patients with type 2 DM and 70 age- and gender-matched healthy volunteers. Patients were divided into 2 groups according to the presence of microvascular complications such as retinopathy, nephropathy, and neuropathy. RESULTS: Patients showed slightly lower hematocrit and higher serum fibrinogen levels than control subjects, but other clinical profiles, including stroke risk factors except for diabetes, were comparable between patients and controls. The flow velocity of the ICA but not the MCA and BA in patients regardless of the complication was significantly higher than that in controls. The PIs of the MCA and ICA were significantly higher in patients with complication than those without complication, as well as in controls. The PI of the BA was also significantly higher, even in patients without complication, than in controls. The PIs of the MCA and ICA but not the BA were closely correlated with the duration of DM (r(2)=0.46 and 0.34, respectively). CONCLUSIONS: This study defines TCD findings of diabetes-related cerebral hemodynamic changes and suggests that the PI reflects microangiopathic changes of cerebral vessels.     

重症脑梗死脑血流动力学的动态观察

目的:动态观察重症脑梗死脑血流动力学变化的特征和规律。方法:对42例急性重症脑梗死患者进行连续7天的TCD检测,20例正常人TCD检测数据作为正常组。结果:急性重症脑梗死患者脑血流速度减慢。血管阻力参数值(Pl、Rl)增大,病程的3～5天各指标变化达高峰。结论:根据脑血流动力学的特征性改变,表明重症脑梗死在病程早期就有不同程度的缺血性脑水肿发生,进展迅速,多在病程的3—5天达高峰:TCD用于床旁连续监测,可通过动态观察TCD参数变化,评价颅内压变化、判断预后。     

高血压脑出血术后动态经颅多普勒超声与颅内压监护仪监测的临床意义

目的 探讨高血压脑出血手术方式以及术后如何控制血压.方法 对与96例高血压脑出血患者分别行开颅血肿清除术和血肿腔钻孔引流术,同时对每例患者行颅内压和平均动脉压连续监测7 d,同时监测术后1、3、7、14 d行双侧大脑中动脉平均血流速度和搏动指数值.结果 开颅术对于血肿量>50 ml的患者远期生存质量(6月后ADL分级)与血肿腔钻孔引流术比较有显著差异;另外术后1 d、3 d、7 d、14 d的TCD参数结果分析,开颅术对于缓解颅内压力、改善脑血流优于钻孔引流组.对所有患者术后ICP、MAP监测能有效控制血压防止再出血.结论 对于血肿量>50 ml患者应选择开颅手术.对所有高血压脑出血患者术后应常规进行ICP、MAP监测.     

经颅多普勒超声检测MCA与OA在原发性高血压病中的脑血流储备研究

目的运用经颅多普勒超声对高血压病患者大脑中动脉(MCA)和眼动脉(OA)血流储备及血管反应性研究,探讨其检查结果及临床意义。方法门诊随机抽取20例原发性高血压病患者40只眼及同时期体检健康20例正常对照组40只眼,运用经颅多普勒超声检查2组患者MCA及OA的平均血流速度(Vm)、屏气后的平均血流速度(Vm’)、搏动指数(PI)、屏气后的搏动指数(PI’)和屏气指数(BHI)的参数进行对比分析。结果高血压组与对照组比较:OA的平均血流速度(Vm)、屏气后的平均血流速度(Vm’)、搏动指数(PI)、屏气指数(BHI)与对照组比较均有统计学意义(P<0.05);MCA的搏动指数(PI)、屏气后的搏动指数(PI’)与对照组比较均有统计学意义(P<0.05)。结论通过对高血压患者MCA、OA的脑血管反应性检测,可以为高血压病患者早期及时提供防治依据。     

Effect of perfluorochemicals on experimental cerebral ischemia

It has been noted that perfluorochemicals (PFC) which were developed as artificial blood substitutes, protect against ischemic brain injury by their ability to serve as oxygen carriers. It is also known that normovolemic hemodilution (HD) improves cerebral blood flow (CBF) and neurological symptoms in cerebral infarction. However, there are few reports concerning the effect of PFC on the collateral circulation via pial anastomoses in cases of middle cerebral artery (MCA) occlusion. The ability to record the pial arterial blood pressure (PAP) without interfering blood flow now makes it possible to measure the segmental resistance of cerebral vessels. By using this method, one can measure collateral vessel resistance through pial anastomoses following MCA occlusion. In this paper, we studied the protective effects of PFC combined with HD on ischemic brain injury with the focus on the collateral circulation via pial anastomoses following occlusion of the MCA. Twenty adult cats were studied: control, 8; HD, 5; Fluosol (Fluosol-DA), 7. The systemic arterial pressure (SAP) and PeCO2 were continuously monitored. Subsequently the MCA was occluded via the transorbital approach. CBF in the ectosylvian gyrus (central area of the ischemic lesion) was measured by the hydrogen clearance method. A small pial artery about 100 microns in diameter on the exposed ectosylvian gyrus was punctured nonocclusively with a micropipette filled with 2 M sodium chloride which was connected to a servo-null micropressure system (Model 900, W-P Instruments, Inc. U.S.A.). The electroencephalogram (EEG) was recorded from the ectosylvian gyrus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transcranial Doppler findings during balloon test occlusion of the internal carotid artery.

The authors performed transcranial Doppler ultrasonography (TCD) during internal carotid artery (ICA) balloon test occlusion (BTO) and observed changes in mean flow velocity (Vm) in the middle cerebral artery (MCA), and pulsatility index (PI) while monitoring the stump pressure (Sp) of the internal carotid artery (ICA), and neurologic findings. A group of 17 patients requiring possible temporary or permanent occlusion of the ICA in the course of planned procedures first underwent BTO. A patient who either developed neurologic changes or maintained less than 60% of preocclusion Sp or Vm in the ipsilateral MCA during BTO was considered to have a positive test. Eleven patients had negative results, while in six patients, tests were positive. Mean flow velocity showed a decrease after occlusion in all cases but not to a remarkable extent in some patients. Stump pressure decreased in all negative cases after balloon inflation and than tended to increase progressively during 15 minutes of BTO. Pulsatility index tended to decrease gradually during BTO in all negative patients. However, in positive cases, PI and Sp fell steeply. Only one positive case had a neurologic symptom of severe headache. The decreased PI in the MCA reflected autoregulatory dilation of cerebral vessels to compensate for decreased absolute cerebral blood volume following ICA occlusion. Changes in PI are a good indicator for evaluating blood flow during BTO.     

Regional cerebral blood flow in schizophrenia using stable xenon-enhanced computed tomography

To investigate the regional cerebral blood flow (rCBF) and the factors affecting the rCBF in schizophrenia, we measured the rCBF using stable xenon-enhanced computed tomography in 118 schizophrenic patients and 21 healthy subjects. A multiple regression analysis was applied to assess the potential affecting factors, i.e. age, gender, duration of illness, dose of antipsychotics and usage of antiparkinsonism and antianxiety drugs. The rCBF of the schizophrenic patients was significantly lower than that of the healthy subjects in all regions except for the occipital region. The rCBF was decreased with increasing age in both groups to the same extent. The dosage of antipsychotic drugs taken had a significant regression relationship with the rCBF in the bilateral thalamus.     

The cerebral hemodynamics of repetitive transcranial magnetic stimulation

Repetitive transcranial magnetic stimulation (rTMS) has been shown to be effective in the treatment of affective disorders. However, only little is known about hemodynamic physiological and safety aspects of this method. We studied the cerebral hemodynamics as measured by transcranial Doppler sonography in 20 healthy subjects during different rTMS procedures. Mean cerebral blood flow velocity (CBFBV), pulsatility index (PI), and oxygen consumption were recorded continuously and averaged directly after the rTMS procedure. RTMS did not influence blood pressure, pulse rate, or blood oxygenation. There was a maximal increase of CBFV in the middle cerebal artery (MCA) of 3.6% and 5.6% during 10 Hz and 20 Hz stimulation, respectively. This increase was only seen on the stimulated left hemisphere. The PI remained unchanged during the whole procedure. It is likely that the increase of CBFV is due to dilatation of the small resistance vessels rather than due to vasoconstriction of the MCA. In terms of cerebral hemodynamics, rTMS is a safe and well-tolerated technique with a lower increase of CBFV than that seen in electroconvulsive therapy. Received: 22 March 2000 / Accepted: 4 July 2000     

Transcranial Doppler for evaluation of idiopathic intracranial hypertension

OBJECTIVES: The value of transcranial Doppler (TCD) ultrasonography in assessing patients with Idiopathic Intracranial Hypertension (IIH) is uncertain. We sought to determine the contribution of TCD to their evaluation. MATERIALS AND METHODS: Twenty-three patients with suspected IIH underwent TCD. Mean blood flow (BFV), peak systolic (PSV) and end-diastolic (EDV) velocities, and pulsatility (PI) and resistance (RI) indexes were obtained in the middle cerebral (MCA) and vertebral (VA) arteries and compared (Student's t-test) between patients with confirmed IIH and controls. IIH patients and controls were comparable in terms of age, gender and weight. RESULTS: The mean +/- SD BFV(MCA), PSV(MCA), EDV(MCA) and PI(VA) in the 13 IIH patients were higher than in the ten controls (59 +/- 6.8, 94 +/- 28.5, 43 +/- 12.4, 0.86 +/- 0.16 and 50 +/- 8.6, 72 +/- 25.8, 32 +/- 11.5, 0.58 +/- 0.45 respectively, P < 0.05) but still within normal values. The mean +/- SD PI(MCA), RI(MCA) and RI(VA) values in the IIH patients and controls were similar. CONCLUSIONS: TCD parameters had no useful unique features for monitoring IIH patients.     

Predictability of intracranial pressure oscillations in patients with suspected normal pressure hydrocephalus by transcranial Doppler ultrasound

Abstract

Intracranial pressure (ICP) was monitored continuously for one night in 36 patients with suspected symptomatic normal pressure hydrocephalus (NPH) to identify patients who might benefit from subsequent shunting. In 33 of these patients middle cerebral artery (MCA) blood flow velocity by means of transcranial Doppler sonography (TCD) and ICP were recorded simultaneously. ICP B-waves always paralleled changes in the TCD signal (TCD B-wave equivalents). The relative frequency of ICP B-waves was predictable by TCD, albeit slightly underestimated due to a generally lower relative amplitude of the TCD B-wave equivalents. However; the same TCD B-wave equivalent amplitude could be accompanied by quite different ICP changes in different patients. Considering the baseline values in the absence of pressure wavesthere was no significant relationship between ICP and TCD resistance index (Pourcelot) in different patients. Raising ICP by injection of 10 ml saline into the ventricle, however was accompanied by an increased TCD resistance index in the individual patient. As the relative frequency of B-wave activity is assumed to be an indicator for shunt responsiveness, continuous TCD monitoring can be used as a screening procedure to detect the presence and the relative frequency of B-wave activity in patients with suspected NPH. However, since neither the absolute ICP nor the amplitude of spontaneous oscillations can be predicted, TCD monitoring is not suitable to replace ICP monitoring. [Neurol Res 1994; 16: 398-402]     

高血压合并无症状性大脑中动脉狭窄患者的药物干预研究

目的探讨在降血压治疗的同时联合应用辛伐他汀和阿司匹林对高血压合并无症状性大脑中动脉狭窄患者的干预作用和脑血管事件的预防效果。方法177例高血压合并大脑中动脉狭窄患者,其中90例应用辛伐他汀(每晚20mg)和阿司匹林肠溶片(75mg/d)进行治疗(干预组),通过经颅多普勒超声检查分别观察治疗前及治疗后1～3年大脑中动脉收缩期血流速度峰值、搏动指数、阻力指数、频谱形态,同时检测治疗前后血压、血脂等项生化指标的变化,并与87例对照者进行比较。结果治疗第1年,干预组患者大脑中动脉收缩期血流速度峰值、搏动指数、阻力指数及频谱形态等与治疗前差异无统计学意义(P>0.05);随访至第2,3年,上述各项指标均改善(P<0.01),频谱形态明显好转。随访结束时,两组患者大脑中动脉上述指标间差异有高度统计学意义(均P<0.01),干预组患者脑血管事件发生率为11.11%(10/90),低于对照组的24.14%(21/87)(P<0.01)。结论在有效降低血压的同时,联合应用辛伐他汀和阿司匹林可稳定并延缓高血压患者大脑中动脉狭窄的进程,对降低脑血管事件的发生率具有良好的作用。     

Role of sympathetic nervous system in activity-induced cerebral perfusion

Several studies have suggested that autonomic neural control plays a role in regulation of cerebral blood flow (CBF), although the exact role of the sympathetic nervous system on CBF remains debated. The effects of sympathetic innervation on activity-induced cerebral perfusion changes in humans have not been studied. The aims of this study were therefore (a) to investigate patients with an “intrinsic” sympathetic deficit after stroke and healthy controls with regard to activity-induced cerebral perfusion changes, and (b) to investigate possible differences in functional CBF regulation between the anterior and posterior circulation. Cerebral blood flow velocity in the medial cerebral artery (MCA) and posterior cerebral artery (PCA) was investigated in 21 healthy controls and 17 patients with Wallenberg’s syndrome using transcranial Doppler sonography during cortical activation of MCA and PCA territories, respectively. Patients with a central sympathetic deficit had a prolonged decrease of resistance in the MCA and showed a slower and less pronounced decrease of resistance in the PCA upon cortical activation. No difference was observed between the side with and without sympathetic deficit. Results suggest that (a) sympathetic efferents are involved in economisation of activity-induced changes of cerebral perfusion in the anterior circulation, (b) activity-induced sympathetic regulation of blood flow differs between the anterior and posterior vascular territories in humans and (c) a possible resting sympathetic tonus on extraparenchymal vessel might exist in the posterior circulation.     

Absent middle cerebral artery flow predicts the presence and evolution of the ischemic penumbra

OBJECTIVES: In acute ischemic stroke the pattern of a perfusion-imaging (PI) lesion larger than the diffusion-weighted imaging (DWI) lesion may be a marker of the ischemic penumbra. We hypothesized that acute middle cerebral artery (MCA) occlusion would predict the presence of presumed "penumbral" patterns (PI > DWI), ischemic core evolution, and stroke outcome. METHODS: Echoplanar PI, DWI, and magnetic resonance angiography (MRA) were performed in 26 patients with MCA territory stroke. Imaging and clinical studies (Canadian Neurological Scale, Barthel Index, and Rankin Scale) were performed within 24 hours of onset and repeated at days 4 and 90. RESULTS: MCA flow was absent in 9 of 26 patients. This was associated with larger acute PI and DWI lesions, greater PI/DWI mismatch, early DWI lesion expansion, larger final infarct size, worse clinical outcome (p < 0.01) and provided independent prognostic information (multiple linear regression analysis, p < 0.05). Acute penumbral patterns were present in 14 of 26 patients. Most of these patients (9 of 14) had no MCA flow, whereas all nonpenumbral patients (PI < or = DWI lesion) had MCA flow (p < 0.001). Penumbral-pattern patients with absent MCA flow had greater DWI lesion expansion (p < 0.05) and worse clinical outcome (Rankin Scale score, p < 0.05). CONCLUSIONS: Absent MCA flow on MRA predicts the presence of a presumed penumbral pattern on acute PI and DWI and worse stroke outcome. Combined MRA, PI, and DWI can identify individual patients at risk of ischemic core progression and the potential to respond to thrombolytic therapy beyond 3 hours.     

Effects of advancing age on regional cerebral blood flow. Studies in normal subjects and subjects with risk factors for atherothrombotic stroke.

Regional cerebral blood flow (rCBF) was measured by 133Xe inhalation in 46 normal volunteers, aged 21 to 63 years, and 14 neurologically asymptomatic subjects above age 40 with risk factors for atherothrombotic stroke, including hypertension, diabetes mellitus, and hyperlipidemia. In normal volunteers, there was diffuse and progresive reduction of gray matter flow and weight as well as increases of cerebrovascular resistance (CVR) with advancing age. Reduction of gray matter flow with advancing age appears to be attributed in part to neuronal atrophy and in part to cerebral arteriosclerosis. Regional increases of CVR and reduction of gray matter flow with advancing age were most evident in the middle cerebral arterial (MCA) distribution and were enhanced by the association of risk factors. Development of cerebral arteriosclerosis with age and/or risk factors appears to be most evident in MCA distribution.     

Spontaneous oscillations of arterial blood pressure, cerebral and peripheral blood flow in healthy and comatose subjects.

Slow and rhythmic spontaneous oscillations of cerebral and peripheral blood flow occur within frequencies of 0.5-3 min-1 (0.008-0.05 Hz, B-waves) and 3-9 min-1 (0.05-0.15 Hz, M-waves). The generators and pathways of such oscillations are not fully understood. We compared the coefficient of variance (CoV), which serves as an indicator for the amplitude of oscillations and is calculated as the percent standard deviation of oscillations within a particular frequency band from the mean, to study the impairment of generators or pathways of such oscillations in normal subjects and comatose patients in a controlled fashion. With local ethic committee approval, data were collected from 19 healthy volunteers and nine comatose patients suffering from severe traumatic brain injury (n = 3), severe subarachnoid hemorrhage (n = 3), and intracerebral hemorrhage (n = 3). Cerebral blood flow velocities were measured by transcranial Doppler ultrasound (TCD), peripheral vasomotion by finger tip laser Doppler flowmetry (LDF), and ABP by either non-invasive continuous blood pressure recordings (Finapres method) in control subjects, or by direct radial artery recordings in comatose patients. Each recording session lasted approximately 20-30 min. Data were stored in the TCD device for offline analysis of CoV. For CoV in the cerebral B-wave frequency range there was no difference between coma patients and controls, however there was a highly significant reduction in the amplitude of peripheral B-wave LDF and ABP vasomotion (3.8 +/- 2.1 vs. 28.2 +/- 16.1 for LDF, p < 0.001; and 1.2 +/- 0.7 vs. 4.6 +/- 2.8 for ABP, p < 0.001). This observation was confirmed for spontaneous cerebral and peripheral oscillations in the M-wave frequency range. The CoV reduction in peripheral LDF and ABP oscillations suggest a severe impairment of the proposed sympathetic pathway in comatose patients. The preservation of central TCD oscillations argues in favor of different pathways and/or generators of cerebral and peripheral B- and M-waves.