Increased cerebral blood volume in benign intracranial hypertension.

In two patients with benign intracranial hypertension, the regional cerebral blood volume was markedly elevated (mean of 85 percent) while regional cerebral blood flow was slightly reduced (mean of 10 percent). Reduction of cerebrospinal fluid pressure by removal of cerebrospinal fluid reduced the mean values of regional cerebral blood volume by 13 percent without significant change in regional cerebral blood flow. The abnormal regional volume and regional flow returned to normal concurrent with the clinical improvement. Vinous engorgement and increased intracranial blood volume appear to play an important part in the pathophysiology of increased intracranial pressure in benign intracranial hypertension. A unified concept of the pathogenesis of benign intracranial hypertension is proposed.     

Cerebral blood flow and metabolism in normotensive and hypertensive patients with transient neurologic deficits

We used positron emission tomography to examine retrospectively the effects of blood pressure on regional cerebral blood flow and oxygen metabolism in seven normotensive and eight hypertensive patients with a history of transient neurologic deficits. In the hypertensive patients, a decrease in regional cerebral blood flow was closely related to blood pressure; these changes were most pronounced in the supratentorial structures, especially the striatum and thalamus. In contrast, the regional cerebral metabolic rate for oxygen was less related to blood pressure. Consequently, the regional oxygen extraction fraction was increased in the hypertensive patients, while regional cerebral blood volume and the regional cerebral blood flow volume ratio were unchanged. Multivariate regression analysis confirmed that hypertension was an independent factor affecting regional cerebral blood flow. The analysis also disclosed that age, sex, hematocrit, smoking, and PaCO2 affected regional cerebral blood flow. These findings suggest that the hemodynamic reserve in hypertensive individuals is reduced, which may predispose them to cerebral ischemia and perhaps stroke, even during small decreases in cerebral perfusion pressure.     

Intracranial pressure, conductance to cerebrospinal fluid outflow, and cerebral blood flow in patients with benign intracranial hypertension (pseudotumor cerebri)

Intracranial pressure, conductance to cerebrospinal fluid outflow, and cerebral blood flow were investigated in 14 patients with benign intracranial hypertension (pseudotumor cerebri). Intracranial pressure was increased in 9 patients (20 to 30 mm Hg), borderline in 4 patients (15 to 18 mm Hg), and normal in 1 patient (8 mm Hg). Six patients had plateau waves, and all had B waves in more than 50% of the monitored time. Conductance to cerebrospinal fluid outflow, measured by a lumbo-lumbar perfusion method, was significantly reduced: 0.042 ml X mm Hg-1 X min-1 (+/- 0.004 [SEM]; normal, more than 0.080 ml X mm Hg-1 X min-1). Cerebral blood flow was measured by xenon 133 inhalation and single photon emission computer tomography. Mean hemispheric flow was normal in all cases, averaging 59 +/- 9 ml X 100 gm-1 X min-1. Only 2 patients showed focal low-flow areas. Thus, a disturbance of cerebrospinal fluid circulation seems to be of pathogenetic significance in benign intracranial hypertension.     

Blood flow and oxygen utilisation in the contralateral cerebral cortex of patients with untreated intracranial tumours as studied by positron emission tomography, with observations on the effect of decompressive surgery.

Using positron emission tomography, regional cerebral blood flow and oxygen utilisation were measured in the contralateral cortex of 14 patients with a variety of intracranial tumours. A comparison was made with cortical values derived from 14 normal controls. Compared with normal subjects, patients with brain tumours had a significant reduction in oxygen utilisation and blood flow in their contralateral cortex. Decompression resulting from craniotomy and biopsy, led to a partial reversal of this cerebral hypofunction.     

老年人经颅多普勒超声检出颅内动脉血流异常对卒中或缺血发作的预测价值

目的　评价经颅多普勒超声 (TCD)检出颅内动脉血流异常对老年人卒中或缺血发作的预测价值。方法　对 141例 TCD检查颅内动脉血流异常及 187例颅内动脉血流正常的老年人进行 5年的前瞻性随访研究。结果　卒中或缺血发作发生率在颅内动脉血流异常者为 2 5 .5 3 % ,血流正常者为 6.7% ,差异有显著性 ,(P<0 .0 1) ;在合并糖尿病、高血压的患者中 ,有颅内动脉血流加快者卒中或缺血发作发生率亦明显高于血流正常者 (P<0 .0 5 )。结论　 TCD检查颅内动脉血流加快对卒中或缺血发作有较准确且安全的预测价值     

Effects of increased arterial pressure on blood flow in the damaged brain.

The effect of induced arterial hypertension on cerebral blood flow and intracranial pressure was measured before and after the production of a standard cryogenic brain lesion in 10 anaesthetized, ventilated baboons. Before injury the animals were divided into a group with intact autoregulation, having more than 20% increase in cerebrovascular resistance during arterial hypertension, and a group with impaired autoregulation, in which the change in cerebrovascular resistance was much less. The cryogenic injury produced a rapid rise in intracranial pressure and a reduction of cerebral blood flow in the affected hemisphere. Despite this, there was an increase in cerebrovascular resistance during arterial hypertension in all animals after brain injury, accompanied by a further significant rise in intracranial pressure. It is suggested that this response is unlikely to represent normal physiological autoregulation and caution should be exercised in interpreting it as such in the course of studies of cerebral blood flow in patients with acute brain damage.     

Concurrent changes in intracranial pressure,cerebral blood flow velocity,and brain energy metabolism in rabbits with acute intracranial hypertension

The relationship between intracranial pressure or cerebral perfusion pressure (CPP), cerebral blood flow, and brain energy failure is unpredictable throughout the development of acute intracranial hypertension. The purpose of the present study was to correlate intracranial pressure with cerebral blood flow velocities and brain energy metabolism in adult rabbits. The acute intracranial hypertension was achieved by pressure transmission. Transcranial Doppler waveforms were obtained from the basilar artery for monitoring cerebral blood flow velocities. ³¹P-Magnetic resonance spectroscopy was used to assess brain energy metabolism. The diastolic blood flow velocity began to decrease significantly (34.5%) when the intracranial pressure was equal to half the diastolic arterial pressure for a CPP of 36±18 mmHg. Circulatory cerebral resistances increased significantly (55%) for the same value of CPP. Diastolic frequency was near zero when intracranial pressure approached diastolic arterial pressure (51±12 mmHg), corresponding to a CPP of 30±15 mmHg. At the same time, only a tendency for brain energy metabolism to decrease was observed. Consequently, transcranial Doppler sonography could be proposed for the followup of intracranial hypertension. Magnetic resonance spectroscopy could help to monitor these patients and could be especially proposed in case of high intracranial pressure (near diastolic arterial pressure). The joint ue of these two methods would help in making appropriate therapeutic decision in humans.     

Computed tomographic evidence of cerebral swelling in benign intracranial hypertension.

Computed tomography of 30 patients presenting acutely with benign intracranial hypertension was compared with that of 30 normal controls matched for age and sex. Qualitative and quantitative assessments showed smaller cranial CSF spaces in the cases of benign intracranial hypertension, suggesting that cerebral swelling is involved in the pathogenesis of benign intracranial hypertension.     

Regional cerebral blood flow in essential hypertension: data evaluation by a mapping system

Regional cerebral blood flow was studied by means of the 133Xe inhalation method in 26 untreated and 10 treated patients with essential hypertension. The untreated subjects were divided into newly and previously diagnosed groups to assess the relation between regional cerebral blood flow and the duration of hypertension. The overall flow reduction was more marked in the frontal and temporal regions in the previously diagnosed group, and this was attributed to pathological changes in the district served by the middle cerebral artery. Regional temporal lobe impairment was also noted in the newly diagnosed and treated subjects. A significant correlation was found between regional cerebral blood flow and mean arterial blood pressure.     

Intracranial volume–pressure relationships during experimental brain compression in primates: 2. Effect of induced changes in systemic arterial pressure and cerebral blood flow

In eight anaesthetized, ventilated adult baboons, the intracranial volume–pressure response was examined at differing levels of raised intracranial pressure during induced changes in systemic arterial pressure and cerebral blood flow. The volume–pressure response is defined as the change in ventricular fluid pressure caused by a volume addition of 0·05 ml to the lateral ventricle. At normal intracranial pressure, the volume–pressure response was unchanged by alterations in systemic arterial pressure and cerebral blood flow. At raised intracranial pressure, however, systemic arterial hypertension rendered the intracranial contents more sensitive to the effects of an addition to the ventricular volume as shown by an increased volume–pressure response. When intracranial pressure was increased, there was a significant linear correlation between the volume–pressure response and both arterial pressure and cerebral blood flow. The clinical implication of this phenomenon is that arterial hypertension in patients with increased intracranial pressure is likely to have a deleterious effect by increasing brain tightness.     

经颅多普勒超声STI、rCBFLI与99 mTc-ECD SPECT脑灌注成像半定量分析比较与应用研究

目的为阐述经颅多普勒超声(TCD)的狭窄指数(STI)与局部脑血流量丧失指数(rCBFLI) 公式数理逻辑推导的合理性、实用性。方法将TCD检测的脑梗死病例中18例27条颅内动脉狭窄区的STI、rCBFLI指数与相对应区的SPECT脑血流量下降的半定量分析资料进行回顾性对比研究。结果 18例27条颅内动脉狭窄后局部脑血流量下降TCD的rCBFLI值与SPECT相对脑血流量下降值的比较呈线性模型曲线拟合,r=0．62,P<0．001,n=27;局部脑血流量下降的SPECT测量值与TCD的STI值相关曲线拟合呈复合模型曲线拟合,r=0．65,P<0．001,n=27。结论 TCD的STI 和rCBFLI计算公式可以作为评估颅内动脉狭窄程度的新指标。     

急性颅内高压时呼气末正压通气对脑氧代谢的影响

目的 观察呼气末正压通气（PEEP）对急性高颅压犬脑氧代谢的影响。方法 8只犬,全麻、机械通气,自体血凝块注入右额叶脑内制成颅内高压模型,静脉滴注脂多糖诱发急性肺损伤,PEEP从0cmH2O开始每次增加3cmH2O水柱,直到18cmH2O,每个水平持续20min,在左侧额顶部用光纤颅内压探头监测颅内压（ICP）的变化,记录平均动脉压（MAP）并计算脑灌注压（CPP）。股动脉、左颈内静脉球部逆行置管采血,行血气分析并计算脑氧摄取（CEO2）和脑动静脉氧含量差（Da-jO2）,分析其与MAP、ICP和CPP的相互关系。结果 随着PEEP的递增,MAP下降,ICP,CPP均有不同程度下降,Da-jO2、CEO2呈上升趋势。血流动力变化与脑氧代谢之间无明显相关性。结论 PEEP通气可改善氧合,但使脑灌注下降,血流动力指标与脑氧代谢指标之间无明显一致性,单用ICP、CPP不能完全判断组织灌注是否充分,有必要监测脑氧代谢,以指导设置PEEP水平。     

Effects of extract of ginkgo biloba on intracranial pressure, cerebral perfusion pressure, and cerebral blood flow in a rat model of subarachnoid haemorrhage

The purpose of this study was to investigate in effect of extract of Ginkgo biloba (EGb) on cerebral blood perfusion in a subarachnoid haemorrhage (SAH) rat model. SAH lead to an increase in intracranial pressure and decrease in cranial perfusion pressure and regional cerebral blood flow in all groups. However, the intracranial pressure increases in EGb groups were less than that of the vehicle group (p < .01), whereas the reduction in cranial perfusion pressure and regional cerebral blood flow in the EGb group was less than that of the vehicle and SAH groups (p < .01). It was concluded that EGb attenuates the increase in intracranial pressure and reduction in cerebral blood perfusion after SAH.     

重型颅脑损伤后局部脑氧饱和度的监测及意义

目的探讨重型颅脑损伤后局部脑氧饱和度(rScO2)的变化规律及意义。方法选择29例重型颅脑损伤病人为研究对象,采用近红外线光谱仪(NIRS)持续监测rScO2,与脉搏血氧饱和度(SpO2)、动脉血氧饱和度(SaO2)、平均动脉压(MAP)、颅内压(ICP)和脑灌注压(CPP)等,并将监测结果进行分析比较。结果重型颅脑损伤后rScO2均明显降低。23例存活病人术后早期rScO2呈不同程度上升,此后随ICP变化呈普遍下降然后又逐步上升的趋势。另6例rScO2呈持续性降低者均死亡。SpO2、SaO2、MAP除在死亡病例临死前进行性降低外,整个监测过程中均正常。结论NIRS持续监测rScO2能准确反映重型颅脑损伤后脑氧代谢的变化规律,对临床治疗及预后评估也有重要价值。     

颅内动脉瘤载瘤动脉闭塞术后局部脑血流的变化研究

目的探讨颅内动脉瘤载瘤动脉闭塞术后的局部脑血流改变。方法对10例正常对照者和23例颅内动脉瘤载瘤动脉闭塞术后的患者行99Tcm-ECDSPECT脑显像。结果10例正常对照者脑实质内放射性核素分布浓度均匀,左右两侧对称,脑皮质部完整,未见局限性浓度稀疏或增浓区。23例术后患者中16例显示脑实质内放射性核素分布浓度均匀,呈正常影像;4例显示患侧核素分布浓度较对侧稍稀疏;1例左基底节区呈放射性核素浓度稀疏;另2例于颞叶内侧部显示为放射性核素缺损。99Tcm-ECDSPECT对脑缺血显示的灵敏度、特异性和准确性均为100%。结论99Tcm-ECDSPECT脑显像对判断颅内动脉瘤载瘤动脉闭塞术后局部脑血流的变化具有重要的应用价值。     

Measurement of regional cerebral blood flow, blood volume and oxygen metabolism in patients with sickle cell disease using positron emission tomography

Regional cerebral blood flow, blood volume, fractional oxygen extraction and oxygen consumption were measured by positron emission tomography in six patients with sickle cell disease to see how oxygen delivery to the brain is maintained in the presence of both anemia and a low oxygen affinity hemoglobin. Both regional cerebral blood flow and blood volume were found to be markedly increased compared to values obtained from 14 normal subjects in the same age range. The mean fractional oxygen extraction was not significantly different in the two groups. Mean oxygen consumption in the two groups was also not significantly different but low values in individual patients with sickle cell disease and the presence of atrophy on the CT-scans of three of them were suggestive of some neuronal loss in patients without any history of nervous system involvement. In view of the known high values of cerebral blood flow and metabolism in childhood, it is suggested that when compounded by anemia and abnormal red cells, a hypercirculatory state may make patients in this age-group particularly prone to ischemic infarction.     

Timing and topography of cerebral blood flow, aura, and headache during migraine attacks

Ten years of study has resulted in considerable but fragmented knowledge about regional cerebral blood flow in migraine with aura (classic migraine). In the present study, the number of repeatedly studied patients (n = 63) was large enough to determine statistically significant sequences of events and statistically significant spatial relations. The first observable event was a decrease of regional cerebral blood flow posteriorly in one cerebral hemisphere. Further development of this pathological process was accompanied by the aura symptoms. Thereafter headache occurred while regional cerebral blood flow remained decreased. During the headache phase, regional cerebral blood flow gradually changed from abnormally low to abnormally high without apparent change in headache. In some patients headache disappeared while regional cerebral blood flow remained increased. Although regional cerebral blood flow reduction and aura symptoms in the great majority of patients were unilateral, one-third had bilateral headache. Unilateral headache usually localized to the side on which regional cerebral blood flow was reduced and from which the aura symptoms originated (i.e., aura symptoms were perceived to occur contralaterally but presumably originated in the hypoperfused hemisphere). Our results suggest a simple model for migraine attacks: A pathological disturbance in one cerebral hemisphere causes the aura symptoms and after a time delay, it also causes the headache by stimulating local vascular nociceptors. Bilateral headache caused by a unilateral cerebral disturbance may be explained by recent neuroanatomical and neurophysiological findings.     

高血压病程与高血压患者无症状性脑动脉病变的相关性研究

目的探讨高血压病患者病程与无症状性脑动脉病变的相关性 方法收集245例住院高血压病患者,排除中风或中风史、合并糖尿病或其他颅内疾病的患者。按病程分为<5年、5-10年和>10年三组,应用经颅多普勒超声(TCD)评介病人脑动脉病变,SPSS10.0统计包分析TCD结果和病程之间的相关性。结果各病程组各动脉血速间无差异。 高血压病5年内组和5-10年组之间脑动脉总异常率无差异,但高血压病程>10年后总血管异常率显著增加 除大脑前、后动脉之外,其他各主要动脉异常率和高血压病程呈现直线相关,尤以颈内动脉末端、大脑中动脉血管血速增快(狭窄)率最显著。结论病程是高血压患者无症状性脑血管病变的危险因素     

Effect of intracerebral vasculitis on regional cerebral blood flow

Regional cerebral blood flow was measured by the xenon 133-inhalation method in a 40-year-old man during an acute exacerbation of intracranial vasculitis. Neurologic function was quantitated by the Halstead-Reitan Neuropsychological test battery. The patient was also studied during remission that was induced by steroid therapy. Vasculitis produced a diffuse encephalopathy with generalized reduction in cerebral blood flow. During remission, only local symptoms secondary to a small cerebral infarction remained and regional cerebral blood flow returned to the normal range. There seems to be a close correlation between the severity of symptoms in cerebral vasculitis and reduction of flow through diseased vessels.     

Raised intracranial pressure and cerebral blood flow: I. Cisterna magna infusion in primates

Changes in cerebral blood flow during incremental increases of intracranial pressure produced by infusion of fluid into the cisterna magna were studied in anaesthetized baboons. Cerebral blood flow remained constant at intracranial pressure levels up to approximately 50 mm Hg. At intracranial pressure levels between 50-96 mm Hg a marked increase in cerebral blood flow occurred, associated with the development of systemic hypertension and changes in cerebrovascular resistance. Further increases of intracranial pressure led to a progressive fall in cerebral blood flow. Prior section of the cervical cord prevented both the increase in cerebral blood flow and the systemic hypertension. Alteration of cerebral perfusion pressure by bleeding during the hyperaemia in a further group of animals suggested that autoregulation was at least partially preserved during this phase. After maximum hyperaemia had occurred, however, autoregulation appeared to be lost. The clinical implications of these findings are discussed.