Laser speckle imaging allows real-time intraoperative blood flow assessment during neurosurgical procedures

Currently, there is no adequate technique for intraoperative monitoring of cerebral blood flow (CBF). To evaluate laser speckle imaging (LSI) for assessment of relative CBF, LSI was performed in 30 patients who underwent direct surgical revascularization for treatment of arteriosclerotic cerebrovascular disease (ACVD), Moyamoya disease (MMD), or giant aneurysms, and in 8 control patients who underwent intracranial surgery for reasons other than hemodynamic compromise. The applicability and sensitivity of LSI was investigated through baseline perfusion and CO₂ reactivity testing. The dynamics of LSI were assessed during bypass test occlusion and flow initiation procedures. Laser speckle imaging permitted robust (pseudo-) quantitative assessment of relative microcirculatory flow and standard bypass grafting resulted in significantly higher postoperative baseline perfusion values in ACVD and MMD. The applicability and sensitivity of LSI was shown by a significantly reduced CO₂ reactivity in ACVD (9.6±9%) and MMD (8.5±8%) compared with control (31.2±5% P<0.0001). In high- and intermediate-flow bypass patients, LSI was characterized by a dynamic real-time response to acute perfusion changes and ultimately confirmed a sufficient flow substitution through the bypass graft. Thus, LSI can be used for sensitive and continuous, non-invasive real-time visualization and measurement of relative cortical CBF in excellent spatial–temporal resolution.     

Skin blood flow responses during sleep by laser Doppler flowmetry

Skin surface blood flow at the fingertips was measured in a 21-year-old woman during sleep using laser Doppler flowmetry. Skin blood flow responses (SBFR) are transient reductions in skin blood flow of about 25s in duration. In our subject, SBFR showed a delay time of 8-9s from the onset of skin potential responses (SPR) and appeared more consistently than SPR. The frequency of SBFR decreased during non-rapid eye movement sleep, especially when the sleep stage became deep. These findings indicate the validity of SBFR as a discrete index of autonomic function during sleep.     

Effect of nimodipine on the autoregulation of cerebral blood flow studied by laser-Doppler flowmetry

The present work examines whether nimodipine impairs autoregulation of CBF during hypotension. The CBF of 16 anesthetized rabbits was measured with a laser-Doppler flowmetry probe placed on the external surface of a plexiglas window, chronically inserted in the skull. Autoregulation was triggered by aortic bleeding. First, the effects of three doses of nimodipine (1, 3 and 10 μg/kg) and the solvent were studied in 10 rabbits in which MABP was maintained at 50 mmHg for one minute. Second, 10 μg/kg i.v. nimodipine was administered to 6 rabbits in which MABP was kept at 30 mmHg for one minute. Before bleeding, the 10 μg/kg dose significantly decreased MABP (from 96 ± 11mmHg to 81 ± 11mmHg, P < 0.01) and increased CBF (from 104 ± 20%to147 ± 25%, P < 0.01) as compared to the solvent. In the first set of experiments, only the 10 μg/kg dose suppressed the autoregulatory vasodilation, but CBF was not different from control (84 ± 17%versus87 ± 12%), probably because of the previous induced vasodilation. In the second set of experiments, active vasodilation occurred and the CBF during hypotension was not different from control (72 ± 26%versus65 ± 11%). We conclude that under nimodipine the triggering of the active autoregulatory vasodilation is dependent on both the severity of hypotension and the previous nimodipine-induced vasodilation.     

Regional cerebral blood flow in delirium patients

The purpose of the present paper was to determine the possible mechanism of delirium by using xenon-enhanced computed tomography to measure the regional cerebral blood flow (rCBF) of the patients both during delirium and after improvement from delirium. The rCBF measurements of the frontal, temporal and occipital cortex during delirium ranged from 31.4 to 39.6 mL/100 g per min; the rCBF of the thalamus and basal ganglia ranged from 47.5 to 52.4 mL/100 g per min. After recovery from delirium the rCBF of both areas returned to normal. The findings that reduced rCBF during delirium becomes normal once delirium improves suggest that a possible cause of delirium may be the cerebral hypoperfusion.     

血液光量子疗法对局灶性脑缺血大鼠大脑皮层局部血流量和脑水肿的影响

本文动态观测了光量子疗法治疗血栓栓塞性脑缺血大鼠,大脑皮层局部血流量(rCBF)及脑水肿的变化。结果:缺血6小时经光量子血液治疗2小时后,rCBF于注后30min明显增加,达19.78％(P<0.01),以后各点维持在一定水平,2小时增加到19.30(P<0.05)。脑组织比重:缺血中心区未见明显改善(P>0.1)而半暗区组织比重非常明显增加(P<0.001),可见水肿明显减轻。说明光量子疗法增加rCBF,减轻半暗区水肿。     

Intraoperative blood flow analysis of direct revascularization procedures in patients with moyamoya disease

Moyamoya disease is characterized by the progressive stenosis and often occlusion of the terminal internal carotid arteries, which leads to ischemic and hemorrhagic injuries. The etiology is unknown and surgical revascularization remains the mainstay treatment. We analyzed various hemodynamic factors in 292 patients with moyamoya disease, representing 496 revascularization procedures, including vessel dimension and intraoperative blood flow, using a perivascular ultrasonic flowprobe. Mean middle cerebral artery (MCA) flow rate was 4.4±0.26 mL/min. After superficial temporal artery (STA)–MCA bypass surgery, flows at the microanastomosis were increased fivefold to a mean of 22.2±0.8 mL/min. The MCA flows were significantly lower in the pediatric (16.2±1.3 mL/min) compared with the adult (23.9±1.0 mL/min; P<0.0001) population. Increased local flow rates were associated with clinical improvement. Permanent postoperative complications were low (<5%), but very high postanastomosis MCA flow was associated with postoperative stroke (31.2±6.8 mL/min; P=0.045), hemorrhage (32.1±10.2 mL/min; P=0.045), and transient neurologic deficits (28.6±5.6 mL/min; P=0.047) compared with controls. Other flow and vessel dimension data are presented to elucidate the hemodynamic changes related to the vasculopathy and subsequent to surgical intervention.     

Cerebral blood flow and cerebral hematocrit in patients with cerebral ischemia measured by single-photon emission computed tomography

Abstract– Single-photon emission computed tomography (SPECT) was used for the measurement of regional cerebral blood flow (CBF), cerebral blood volume (CBV) and cerebral hematocrit (Hct). CBF was measured using N-isopropyl-p-I-123-Iodoamphetamine. CBV was measured by both RBC tracer (Tc-99m RBC) and plasma tracer (Tc-99m human serum albumin) and cerebral hematocrit (Hct) was calculated. In normals, the cerebral-to-large vessel Hct ratio was 75.9%. Isovolemic hemodilution in patients with high Hct tended to increase the cerebral-to-large vessel Hct ratio. Low CBF, high CBV and slow cerebral blood mean transit time (MTT by dynamic CT scanning) was seen during the acute stage of completed infarction and during the symptom-free interval of TIA. Cerebral Hct was increased in the ischemic region of poor prognosis.     

The effect of ACTH on cerebral blood flow in children with intractable epilepsy

Cerebral blood flow was assessed by ultrasound in 12 children with intractable epilepsy who were treated with ACTH. The average maximal blood velocity (A/L) and end-diastolic blood velocity (d) of the internal carotid artery were measured, before, during and after ACTH therapy in each subject. The right and left mean A/L and d values were significantly decreased during ACTH therapy, and these values returned to the previous levels after the treatment. Cerebral function in children treated with ACTH may be affected by a decrease in cerebral blood flow.     

Normal pressure hydrocephalus and cerebral blood flow: a review

Normal pressure hydrocephalus is a neurological disease which poses both diagnostic and therapeutic problems for the clinician. The measurement and characterisation of cerebral blood flow has been proposed as a tool for resolving such problems as well as elucidating its pathophysiology. We review the results of studies in which this tool has been applied to normal pressure hydrocephalus patients and consider the merits of the techniques that have been utilised. Finally, consideration is given to feasible future studies and the methods that could be employed in the study of cerebral blood flow and metabolism in patients with normal pressure hydrocephalus.     

Acute changes in cerebral blood flow associated with marijuana smoking

Cerebral blood flow (CBF) was measured in experienced (ES) and inexperienced (IS) marijuana smokers with the 133xenon inhalation technique before and after smoking both a high-potency marijuana cigarette and a placebo marijuana cigarette. CBF was measured twice under resting conditions in a control group. Mood states before and after marijuana smoking were quantified with the Profile of Mood States (POMS). Analyses of POMS factors after smoking marijuana revealed IS had an increase in anxiety while ES had a decrease. IS also had a significant increase in depression and decrease in vigor, but neither variable changed in the ES. After marijuana, CBF decreased in IS, but in ES, it increased in comparison with the 2 control runs. In both IS and ES, CBF changes following placebo administration were similar to those associated with marijuana smoking. However, in IS, the marijuana-induced CBF decrease was significantly higher than that associated with placebo. There were no statistically significant differences between the CBF increase seen after placebo and marijuana in ES. Anxiety, anger, fatigue, confusion and depression had significant negative correlations with CBF while vigor correlated positively, but the anxiety factor was the only one to account for a significant percentage of the change (parital correlation) in hemispheric CBF.     

Integrative cerebral blood flow regulation in ischemic stroke

Optimizing cerebral perfusion is key to rescuing salvageable ischemic brain tissue. Despite being an important determinant of cerebral perfusion, there are no effective guidelines for blood pressure (BP) management in acute stroke. The control of cerebral blood flow (CBF) involves a myriad of complex pathways which are largely unaccounted for in stroke management. Due to its unique anatomy and physiology, the cerebrovascular circulation is often treated as a stand-alone system rather than an integral component of the cardiovascular system. In order to optimize the strategies for BP management in acute ischemic stroke, a critical reappraisal of the mechanisms involved in CBF control is needed. In this review, we highlight the important role of collateral circulation and re-examine the pathophysiology of CBF control, namely the determinants of cerebral perfusion pressure gradient and resistance, in the context of stroke. Finally, we summarize the state of our knowledge regarding cardiovascular and cerebrovascular interaction and explore some potential avenues for future research in ischemic stroke.     

强迫症的局部脑血流动态显像研究

目的　探讨强迫症患者各脑叶的代谢状态及脑功能异常与其发病的关系。　　方法　采用单光子发射计算机扫描 (SPECT)技术 ,对未服药的 2 2例强迫症患者于静息及症状诱发状态下行局部脑血流 (rCBF)动态显像研究。　　结果　 1 8例有rCBF异常 ,表现为皮层内局限性放射性分布稀疏、缺损区 ,异常脑叶主要为顶叶、额叶、颞叶 ,并发现脑功能异常与强迫症状的严重程度及药物治疗反应有关。　　结论　大脑顶叶、额叶等脑叶的功能异常是部分强迫症发病的神经病理学基础     

Herpes zoster ophthalmicus with cerebral angiitis and reduced cerebral blood flow

Two patients with herpes zoster ophthalmicus (HZO) who experienced a delayed contralateral hemiparesis, the so-called crossed zoster syndrome, are described. Particular emphasis is paid to the cerebral blood flow (CBF) findings studied with the Xenon-133 inhalation technique using single photon emission computed tomography (SPECT). In a 40-year-old female with right-sided hemiparesis, angiography showed multiple segmental narrowings of the intracerebral arteries. Cerebral computer tomography (CT) scans were normal. The CBF studied 11 months after the HZO showed a generalized reduction of flow which, however, was more pronounced in the left hemisphere. On re-examination 8 months later both the mean hemispheric flow and regional CBF (rCBF) had increased to normal values. In a 66-year-old male with dysphasia and right-sided hemiparesis, cerebral CT scans demonstrated two small deep left-sided infarcts. CBF examination showed a generalized reduction of flow in the left hemisphere. The flow was slightly increased on re-examination 12 months later. These findings suggest that the Xenon-133 inhalation method represents a useful way to demonstrate the CBF pattern in this group of patients.     

Regional cerebral blood flow in the rat during prolonged seizure activity

In order to evaluate the possible contribution of regional insufficiency in blood flow to the development of epileptic brain damage, we have measured changes in total and regional cerebral blood flow (tCBF and rCBF) during the course of prolonged sustained seizures. We have used both a particle distribution method (radioactively labelled microspheres) and a diffusible tracer method (iodo [14C]antipyrine). Seizures were induced with bicuculline (1.2 mg/kg, i.v.) in rats with neuromuscular paralysis, mechanically ventilated with 70% N2O/30% O2, rCBF was determined in 13 brain regions after 10, 30, 60 and 120 min of seizure activity. Microsphere and iodo[14C]antipyrine methods gave identical control values for tCBF (0.88 +/- 0.02 vs 0.86 +/- 0.07 ml/g brain/min) and closely similar rCBF values. The increases in tCBF after 10 and 30 min seizure activity were less as measured with microspheres than with iodo [14C]antipyrine (2.42 +/- 0.29 vs. 4.99 +/- 0.94 and 1.79 +/- 0.18 vs 3.05 +/- 0.30 mg/g brain/min, respectively). With microspheres, rCBF values showed considerable interhemisphere variability, but did not do so with iodo [14C]antipyrine. The regional pattern of flow changed during seizures. Changes in neocortical rCBF tended to match changes in tCBF. Consistent decreases in rCBF relative to tCBF were seen in the pons-medulla and cerebellum at all seizures times. Relative increases in rCBF were seen at all seizure times in the thalamus, and at 10 and 30 min in colliculi and midbrain. In the hippocampus, rCBF was unchanged (relative to tCBF) at 10 and 30 min, but was increased at 60 and 120 min of seizure activity. Thus, regions developing epileptic brain damage in this model of status epilepticus (hippocampus, thalamus, neocortex) show increases in rCBF greater than those in regions not showing brain damage (cerebellum, brain stem).     

Effect of age and vascular anatomy on blood flow in major cerebral vessels

Measurement of volume flow rates in major cerebral vessels can be used to evaluate the hemodynamic effects of cerebrovascular disease. However, both age and vascular anatomy can affect flow rates independent of disease. We prospectively evaluated 325 healthy adult volunteers using phase contrast quantitative magnetic resonance angiography to characterize these effects on cerebral vessel flow rates and establish clinically useful normative reference values. Flows were measured in the major intracranial and extracranial vessels. The cohort ranged from 18 to 84 years old, with 157 (48%) females. All individual vessel flows and total cerebral blood flow (TCBF) declined with age, at 2.6 mL/minute per year for TCBF. Basilar artery (BA) flow was significantly decreased in individuals with one or both fetal posterior cerebral arteries (PCAs). Internal carotid artery flows were significantly higher with a fetal PCA and decreased with a hypoplastic anterior cerebral artery. Indexing vessel flows to TCBF neutralized the age effect, but anatomic variations continued to impact indexed flow in the BA and internal carotid artery. Variability in normative flow ranges were reduced in distal vessels and by examining regional flows. Cerebral vessel flows are affected by age and cerebrovascular anatomy, which has important implications for interpretation of flows in the disease state.     

Changes in cerebral blood flow pattern after carotid endarterectomy

A comparison was made between pre- and postoperative cerebral blood flow measurements in 20 patients who underwent endarterectomy. Most patients showed no difference between both studies. However in 4 of the series an increase in blood flow was observed while in another 4 patients a decrease occurred. Especially patients with a low preoperative flow seemed to have profited from the endarterectomy.     

Laser Doppler monitoring of cerebral blood flow

Abstract

The clinical management of cerebral hemodynamic status has become more important, as well as more complex, in recent years. In response", monitoring systems for neurological patients have grown increasingly sophisticated. Unfortunately the capability of monitoring cerebral blood flow is absent in commercially available monitoring systems at this time. Various investigators have demonstrated that laser Doppler systems are capable of meeting this need. We present here a summary of laser Doppler technology and also a review of the progress in application of this technology to provide meaningful input for clinical decision making. Recent clinical experience and advances in instrumentation design suggest that laser Doppler monitoring of cerebral blood flow may soon become routine in neurological intensive care settings. [Neurol Res 1996; 18: 251–255]     

Regional cerebral blood flow during cortical spreading depression in rat brain: increased reactive hyperperfusion in low-flow states

The purpose of the present study was to characterize the initial vascular events accompanying cortical spreading depression (CSD) of the rat brain. Regional cerebral blood flow (rCBF) was measured during the first 1–2 min of CSD using ¹⁴C-iodoantipyrine autoradiography. The material included a reference group, and 4 groups where rCBF was altered by indomethacin treatment, hypo- or hypercapnia, or one previous episode of CSD. rCBF did not change prior to, or during the onset of CSD. Thirty seconds later, rCBF increased depending on the pre-existing level of blood flow, i.e. the rise of rCBF was pronounced at depressed flow levels, but small or absent at normal or high flow levels. The prevalent view that CSD is intimately associated with vasodilatation was accordingly not supported. The activated rCBF in normocapnic rats ranged between 93 and 175 ml/100g/min, supra normal values were the exception rather than the rule. The rCBF rise, when present, probably succeeds a period of brain hypoxia, and should be classified as a reactive hyperfusion. The results together with earlier clinical and experimental findings, support that CSD may serve as experimental migraine model.