Somatosensory evoked potentials and cortical blood flow during craniotomy for vascular disease

It has been demonstrated that central conduction time (CCT) is slowed and that attenuation of cortical potentials occurs with reduced cerebral perfusion. During 11 craniotomies for aneurysm, arteriovenous malformation (AVM), or extracranial-intracranial (EC-IC) bypass, we continuously monitored somatosensory evoked potentials (SSEPs) and regional cortical blood flow (rCBF) as determined by a thermal flow probe. The CCT was calculated and correlated with the rCBF. In 8 of the 11 cases, the rCBF values varied within 1 SD of normal values derived from 25 measurements of nonischemic cerebral cortex. All initial CCT values were within 1 SD of normal, but 4 of 11 patients had a prolonged CCT intraoperatively. Three of these were associated with a low rCBF (14 to 31 ml/100 g/minute). One patient had postoperative confusion at the time of discharge. One patient who underwent AVM embolization had a permanent loss of SSEPs postoperatively, and his preexisting hemiparesis was more profound after operation. Finally, 1 patient's CCT improved after EC-IC bypass. This is a preliminary study that demonstrates the feasibility of monitoring CCT and rCBF during craniotomy. When rCBF values fall and the CCT slows, neurological deficit will probably occur.     

Preliminary results of PET activation study in cerebral arteriovenous malformation (AVM), using C15O2 and 18F-FDG

The authors applied PET activation study to two patients with arteriovenous malformation (AVM) to localize primary motor cortex before surgery or embolization. The change in regional cerebral blood flow (rCBF) was measured during foot movements in Case 1 who had a 2-cm AVM located in the post-central gyrus. Superimposed PET/MRI images revealed that the rCBF increase was located in the pre-central gyrus. Its validity was confirmed by intraoperative cortical mapping using electrical median nerve stimulation. The patient safely underwent total removal of AVM. The change in regional cerebral metabolic rate for glucose (rCMRglc) was measured during hand movements in Case 2 who had a huge AVM over the central sulcus. Superimposed PET/MRI images revealed that hand movements significantly increased rCMRglc in the frontal cortex, which was separated from the original primary motor area. The patient safely underwent partial embolization, although he suffered transient weakness of the face after embolization. The preliminary results strongly suggest that PET activation study is useful to localize precisely cortical functions of the patients with AVM, thus reducing morbidity after treatment. The results also suggest that cortical functions may undergo translocation when huge AVM involves the eloquent area.     

应用控制性降压降低脑动静脉畸形术后脑过度灌注

目的：应用手术切除脑动静脉畸形（ＡＶＭ）病灶后给予控制性低血压的方法,观察病灶周围脑组织的灌流情况,探讨术后脑肿胀发生的可能防治措施。方法：选择病灶最大径≥６ｃｍ的ＡＶＭ病人８例,在术中ＡＶＭ切除后,激光多普勒血流测定仪显示病灶周围脑组织高灌注时给予静脉推注２．５％硫喷妥钠－５￣１０ｍｇ／ｋｇ促使血压在原基因上下降２５％左右,观察病灶周围脑组织的灌注情况。结果：８例ＡＶＭ的基础平均血压为７７．６３     

Cerebral hemodynamics in angioma patients: an intraoperative study

Local hemodynamics were investigated during 33 operations for cerebral arteriovenous malformation (AVM). In all cases, microvascular Doppler sonography was used to measure flow velocities and vasomotor reactivity to CO2 changes. Intravascular pressure recordings were performed in six patients. The AVM feeders had low intravascular pressure, high flow velocity, low peripheral stream resistance, and very poor vasomotor reactivity. Remote brain arteries showed no abnormalities. Doppler findings in arterial branches of AVM feeders that supplied normal brain indicated arteriolar dilation in their peripheral distribution. On removal of the angiomas, the arteries that formerly supplied them showed a return to normal intravascular pressure, whereas flow velocities dropped far below normal in these vessels. Remote arteries and branches of the former AVM feeders supplying the brain did not show any signs of impaired vasomotor reactivity following angioma removal. The results are in contrast to the normal perfusion pressure breakthrough theory.     

Early effects of experimental arterial subarachnoid haemorrhage on the cerebral circulation part II: Regional cerebral blood flow and cerebral microcirculation after experimental subarachnoid haemorrhage

Summary Employing the experimental set-up and the methods described — in part I of the paper, the measurements of the regional cerebral blood flow (rCBF) and evaluation of brain microcirculation were performed. The control series provided normal values and constituted the reference for the results of the posthaemorrhagic measurements.Arterial subarachnoid haemorrhage increases transitorily the intracranial pressure to values close to the diastolic blood pressure. The rise of the blood pressure (Cushing response) is not adequate to prevent the reduction in the cerebral perfusion pressure.Cerebral blood flow diminishes after arterial subarachnoid haemorrhage during the elevation of intracranial pressure. It results in numerous, disseminated areas of reduced regional cerebral blood flow.During 4 hours following arterial subarachnoid haemorrhage global cerebral blood flow returns to normal values, while focal reductions in blood flow persist in the grey matter structures of both hemispheres. These foci are accompanied by confined areas of markedly increased regional cerebral blood flow.Disseminated foci with a reduced number of patent capillaries are found in the grey matter structures of both hemispheres 1 and 4 hours following arterial subarachnoid haemorrhage. Their number decreases during the 4 hours observation.     

Effects of xenon anesthesia on cerebral blood flow in humans: a positron emission tomography study

BACKGROUND: Animal studies have demonstrated a strong neuroprotective property of xenon. Its usefulness in patients with cerebral pathology could be compromised by deleterious effects on regional cerebral blood flow (rCBF). METHODS: 15O-labeled water was used to determine rCBF in nine healthy male subjects at baseline and during 1 minimum alveolar concentration (MAC) of xenon (63%). Anesthesia was based solely on xenon. Absolute changes in rCBF were quantified using region-of-interest analysis and voxel-based analysis. RESULTS: Mean arterial blood pressure and arterial partial pressure for carbon dioxide remained unchanged. The mean (+/-SD) xenon concentration during anesthesia was 65.2+/-2.3%. Xenon anesthesia decreased absolute rCBF by 34.7+/-9.8% in the cerebellum (P<0.001), by 22.8+/-10.4% in the thalamus (P=0.001), and by 16.2+/-6.2% in the parietal cortex (P<0.001). On average, xenon anesthesia decreased absolute rCBF by 11.2+/-8.6% in the gray matter (P=0.008). A 22.1+/-13.6% increase in rCBF was detected in the white matter (P=0.001). Whole-brain voxel-based analysis revealed widespread cortical reductions and increases in rCBF in the precentral and postcentral gyri. CONCLUSIONS: One MAC of xenon decreased rCBF in several areas studied. The greatest decreases were detected in the cerebellum, the thalamus and the cortical areas. Increases in rCBF were observed in the white matter and in the pre- and postcentral gyri. These results are in clear contradiction with ketamine, another N-methyl-D-aspartate antagonist and neuroprotectant, which induces a general increase in cerebral blood flow at anesthetic concentrations.     

Congenital multiple cavernous angiomas associated with thrombosed arteriovenous malformation of the brain--case report

A 16-year-old girl presented with multiple cerebral cavernous angiomas with calcifications due to repeated hemorrhages and a thrombosed cerebral arteriovenous malformation (AVM). Her 18-year-old elder sister also had multiple cerebral cavernous angiomas associated with calcifications, which suggested presence of repeated previous hemorrhages. Surgical removal via a right occipital craniotomy resulted in a good outcome. The histological diagnosis was thrombosed AVM. Evaluation of congenital vascular anomaly needs to take into consideration the combination of other congenital vascular anomalies and their familial occurrence.     

Effects of Xenon Anesthesia on Cerebral Blood Flow in Humans: A Positron Emission Tomography Study

Background: Animal studies have demonstrated a strong neuroprotective property of xenon. Its usefulness in patients with cerebral pathology could be compromised by deleterious effects on regional cerebral blood flow (rCBF).

Methods: 15O-labeled water was used to determine rCBF in nine healthy male subjects at baseline and during 1 minimum alveolar concentration (MAC) of xenon (63%). Anesthesia was based solely on xenon. Absolute changes in rCBF were quantified using region-of-interest analysis and voxel-based analysis.

Results: Mean arterial blood pressure and arterial partial pressure for carbon dioxide remained unchanged. The mean (+/- SD) xenon concentration during anesthesia was 65.2 +/- 2.3%. Xenon anesthesia decreased absolute rCBF by 34.7 +/- 9.8% in the cerebellum (P < 0.001), by 22.8 +/- 10.4% in the thalamus (P = 0.001), and by 16.2 +/- 6.2% in the parietal cortex (P < 0.001). On average, xenon anesthesia decreased absolute rCBF by 11.2 +/- 8.6% in the gray matter (P = 0.008). A 22.1 +/- 13.6% increase in rCBF was detected in the white matter (P = 0.001). Whole-brain voxel-based analysis revealed widespread cortical reductions and increases in rCBF in the precentral and postcentral gyri.     

Progression of arteriovenous malformation in moyamoya syndrome

Summary We report a case of moyamoya disease (MMD) associated with arteriovenous malformation (AVM). The 30-year-old female patient presented with left-hemispheric transient ischaemic attacks (TIAs) involving dysphasia and right-sided hemiparesis. CT-scan and lumbar puncture showed no evidence of intracranial haemorrhage. Cerebral angiography revealed typical moyamoya vessels and occlusion of multiple cerebral arteries with consecutive collateral blood supply. Moreover, a left-parietal AVM with a diameter of approximately 2 cm was detected. An extra-intracranial arterial bypass (EIAB) connecting the left superficial temporal artery (STA) with a cortical branch of the left middle cerebral artery (MCA) was performed (STA-MCA anastomosis) and yielded subsequent resolution of the neurological deficit. Nine months post-operatively neurological deficits similar to those of the initial presentation recurred. Repeated angiography suggested comparatively increased AVM blood flow, and successful extirpation of the AVM gradually re-established almost full functional ability. However, deterioration of the neurological condition developed again. We herewith present the first European case of moyamoya disease associated with arteriovenous malformation and report the clinical course under an alternative neurosurgical treatment consisting of STA-MCA anastomosis and delayed extirpation of the AVM.     

CBF studies with Xenon-133 in arteriovenous malformations: a methodological study.

A new model for the two dimensional rCBF technique using the inhalation of Xenon 133 was tested in patients with arteriovenous malformations. It was hypothetized that, in contrast to the conventional CBF model, it corrects for the artifactual shunt flow through the AVM and thus yields physiological CBF data. Four regions of interest (AVM, contralateral to AVM, ipsilateral hemisphere, contralateral hemisphere) were defined in 17 patients with AVMs and analyzed for differences in grey matter flow (F1). In contrast to the conventional CBF model, the new model shows a decreased flow over the AVM area, corresponding to the results of Xenon CT and SPECT. Furthermore, the blood pool parameter P4 is very sensitive to the location of the AVM. Thus further investigations of the hemodynamics of AVMs with this model are encouraged.     

What factors are related to impairment of cerebrovascular reserve before and after arteriovenous malformation resection? A cerebral blood flow study using xenon-enhanced computed tomography

OBJECTIVE: To examine the incidence and possible determinants of impaired vascular reserve in arteriovenous malformation (AVM)-affected brain, before and after surgery. METHODS: In a prospective study of 30 patients, the regional cerebrovascular reserve capacity (rCRC) and the vasodilated regional cerebral blood flow (rCBF) were assessed during an acetazolamide challenge, using xenon-enhanced computed tomography, before and after complete AVM resection. Single brain slices at the level of the basal ganglia were examined, and scanning through the AVMs was avoided. Five regions of interest in the AVM-bearing hemisphere were compared with their counterparts in the unaffected hemisphere. Vasodilated rCBF reductions of at least 20% in one or more regions of interest and rCRC values of less than 10 ml/100 g/min were considered to be significant. RESULTS: Ipsilateral vasodilated rCBF was significantly reduced in 17 patients before surgery and 15 patients after surgery. Ipsilateral rCRC was impaired in 14 patients before surgery and 12 patients after surgery. Large AVM size, venous congestion, and AVM-related vascular territories were correlated with impaired vascular reserve in AVM-nonadjacent brain tissue before surgery. Similar correlations were observed after surgery, except that not AVM size but a large number of AVM-supplying vascular territories was correlated. Moreover, the smallest AVMs and those supplied by a single vascular territory, as well as hemorrhage and nonhemorrhagic neurological deficits as presenting symptoms, were correlated with reduced ipsilateral vasodilated rCBF before surgery. Among patients with AVMs and nonhemorrhagic epilepsy, a trend of impaired cerebrovascular reserve was observed. In the only case of postresectional "breakthrough," the preoperative rCRC was not impaired but abnormally high. CONCLUSION: Among the determinants of impaired cerebrovascular reserve, AVM size is already a constituent of current grading scales and decision-making paradigms, whereas factors such as venous congestion have been less closely considered or less obvious but may deserve increased attention in the future. Nonhemorrhagic epilepsy in patients with AVMs may constitute the clinical equivalent of chronic cerebral ischemia in a murine model. Postresectional breakthrough may be partly attributable to individual predisposition to excessive vasoreactivity in the whole brain.     

Cerebral arteriovenous malformations (C. AVM) and associated arterial aneurysms (AA)

Summary We report a series of 101 patients with cerebral arteriovenous malformations (CAVM), in which 23 cases presented with one or several arterial aneurysm(s) (AA). Each AA could be classified into distal intra-lesional, proximal or remote. Patients with CAVM+AA tend to be older and more frequently present with epilepsy, haemorrhage events and neurological deficits. Of these 23 patients, 16 had their AVM treated partially or totally by embolization. In our series, the endovascular treatment of the arteriovenous shunt with a proximal AA on the same vessel has resulted in at least a regression, and sometimes a disappearance of the arterial ectasia. Although partial treatment of the AVM does no erase the risk of haemorrhage from the malformation itself, it may diminish the chance of developing a flow-related AA or any other expression of the high-flow angiopathy.Presented at the Sendai Symposium, May 1987 and at the European Congress of Neurosurgery, Barcelona, September 1987.     

Cerebral blood flow measurements using stable xenon CT with very short inhalation times.

A noninvasive, simplified method using inhalation of stable xenon (Xe(s)) and computed tomographic (CT) scanning to estimate regional cerebral blood flow (rCBF) and regional partition coefficient (r lambda) is described. Twenty-four patients with cerebrovascular occlusive disease and six volunteer controls inhaled 30% Xe(s) and 70% oxygen for 180 seconds and exhaled for 144 seconds during serial CT scanning without denitrogenation. The end-tidal Xe(s) concentration was continuously monitored with a thermoconductivity analyzer to determine the build-up range (A value) and build-up rate constant (K value) for arteries with the curve fitting method. The time-CT number (Hounsfield unit) curve for cerebral tissue during the Xe(s) washin and washout phases was used to calculate r lambda and rCBF using least squares curve fitting analysis. The resultant r lambda and rCBF map demonstrated a reliable distribution between the gray and white matter, and infarcted areas. rCBF was high in gray matter, low in white matter, and much lower in infarcted areas than in white matter, r lambda was high in white matter, low in gray matter, and much lower in infarcted areas. Xe(s) CT-CBF studies with very short inhalation of 180 seconds is a clinically useful method for evaluation of rCBF in patients with cerebrovascular diseases.     

Cerebral circulation and metabolism in adults' Moyamoya disease-PET study

Summary Regional cerebral blood flow (rCBF), oxygen extraction fraction (rOEF), cerebral metabolic rate for oxygen (rCMRO₂) and cerebral blood volume (rCBV) in nine cases of moyamoya disease in adults were studied with positron emission CT (PET) scan, using¹⁵O steady-state methods. Three cases showed ischaemic symptoms and the other six cases showed haemorrhagic symptoms. PET scan was performed during the chronic stage. Control data were obtained from eight normal volunteers. Regional cerebral blood flow and other physiological parameters in cerebral gray matter, white matter and basal ganglia were compared with normal controls.All nine cases of Moyamoya disease showed decreased rCBF, though not significant, in cerebral gray matter, white matter and basal ganglia. Reduction of rCBF was significant in the cerebral cortex of six haemorrhagic cases. This significant decrease was considered to be due to diaschisis and also brain atrophy caused by the cerebral haemorrhage. There was a significant increase in rCBV in white matter of the both ischaemic and haemorrhagic cases. The calculated value of CBF/CBV is considered to be an index of perfusion pressure. This value was significantly decreased in all three regions, though rOEF was not significantly increased in moyamoya disease. Hence the cerebral circulation in adults with moyamoya disease appears to be characterized by a mild decrease in perfusion pressure and prolonged circulated time.     

Xenon-enhanced CT CBF measurements in intracranial vascular malformations

In the management of intracranial vascular malformations, it is important to know the regional cerebral blood flow in its surrounding structure. However, CT scan with contrast medium and angiography have only a limited ability to estimate the rCBF. In this study, stable xenon-computerized tomography scanning by means of the end-tidal gas-sampling method was performed in eleven patients with intracranial vascular malformations. Seven of the patients had arteriovenous malformations, three had venous angiomas and one had aneurysm of the vein of Galen. In two patients with large arteriovenous malformations, in two with "larger" venous angioma and in one with aneurysm of the vein of Galen, rCBF values were significantly reduced, particularly adjacent to the malformations. In contrast, there were no areas showing reduced rCBF in cases where the malformations were small. This indicates development of ischemia correlates with the size of malformations. From the xenon-enhanced CT scan and angiographic findings, the presence of steal phenomenon with venous congestion might be a cause of rCBF reduction in those cases where ischemia exists.     

氙气麻醉对健康受试者大脑糖代谢与脑血流耦联关系的影响:采用正电子计算机断层显像技术的研究

背景 全身麻醉药能够改变脑局部糖代谢(regional cerebral glucose metabolism,rCMRglc)和脑血流(cerebral blood flow,CBF)之间的相互关系.本研究应用正电子计算机断层显像(positron emission tomography,PET)研究技术评价氙气麻醉...     

Cerebral hemodynamics and metabolism in patients with cerebral arteriovenous malformations: an evaluation using positron emission tomography scanning

OBJECT: The purpose of this study was to evaluate cerebral hemodynamic and metabolic features in patients with arteriovenous malformations (AVMs) by using positron emission tomography (PET) scanning. METHODS: Twenty-four patients with supratentorial cerebral AVMs participated in PET studies in which 15O inhalation steady-state methods were used. The authors recorded the values of regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), the regional oxygen extraction fraction (rOEF), and the regional cerebral metabolic rate of O2 (rCMRO2) at three designated regions of interest (ROIs) in each patient. These ROIs included perilesional (ROI-p), ipsilateral remote (ROI-i), and contralateral symmetrical (ROI-c) brain regions. To identify the factors that exert a direct effect on the hemodynamics of brains affected by AVM, we also separated the lesions according to their size and flow type shown on angiograms, and grouped the patients according to the presence or absence of progressive neurological deficits. We then compared the PET parameters at different ROIs in individual patients and evaluated the mean values obtained for all 24 patients according to AVM flow type and size, and the presence or absence of progressive neurological deficits. CONCLUSIONS: Overall, mean rCBV and rOEF values were significantly higher in ROI-p than in ROI-c (p = 0.00046 and p = 0.015, respectively). No significant differences were seen between the ROI-i and ROI-c with respect to rCBF, rCBV, and rOEF. Mean rCMRO2 values were similar in the three ROIs; however, the mean rCBF was significantly lower in the ROI-p than in the ROI-c in patients with high-flow AVMs (p = 0.019), large AVMs (p = 0.017), and progressive neurological deficits (p = 0.021). Furthermore, the mean rOEF values were significantly higher in the ROI-p than in the ROI-c in patients with high-flow AVMs (p = 0.005), large AVMs (p = 0.019), and progressive neurological deficits (p = 0.017). The PET studies revealed hemodynamic impairment characterized by decreased rCBF and increased rOEF and rCBV values in the ROI-p of patients with large, high-flow AVMs regardless of whether they exhibited progressive neurological deficits.     

Regional cerebral blood flow after a localized cerebral contusion in pigs

Summary Regional cerebral blood flow (rCBF) in anaesthetized pigs is investigated before and after an induced focal cerebral contusion. Mean intracranial pressure increased for a short period following the contusion and reduced perfusion pressure to 60% of control pressure. Forty five minutes later the mean intracranial pressure was still high and different from the control values. Global flow and cerebral production of CO² increased concomitantly. In the cortical region where the contusion was visible macroscopically the rCBF diminished from 36.5 to 29.1 ml/min/100g. In the rest of the grey matter the rCBF raised after the contusion with an increase away from the centre of the lesion. CBF of cortical grey matter in the region symmetrically to the contusion increased significantly more than in the traumatized hemisphere. White matter rCBF changed least in the region underlying the contusion, while an increase was observed away from the contusion and on the opposite side of the brain. The correlation between tension of CO₂ in arterial blood and regional cerebral blood flow disappeared in the region of the contusion. The correlation between global metabolism and regional cerebral blood flow disappeared after the contusion in all regions. Local flow modulating factors influencing flow in the region of macroscopically visible injury has influence abating with distance from the centre of the injury together with a possible neuronally transmitted drive on flow in the opposite hemisphere.     

The use of hypercapnia in the study of regional cerebral blood flow abnormalities with 133Xe

Induced hypercapnia was utilized for the study of regional cerebral blood flow (rCBF) using ¹³³Xe inhalation. Washout data were grossly biexponential with fast and slow components representing gray and white matter, respectively. Corrected washout data were fitted to a two-compartment model using a nonlinear least squares regression to calculate rCBF. In normal patients, hypercapnia resulted in a 2–4% increase in hemispheric flow for each Torr rise in PCO₂. In abnormal studies either a lesser increase in flow was effected, or new regional or hemispheric asymmetries were seen, or both. The use of hypercapnia increased the sensitivity of the rCBF determinations from 30 to 90% in patients with transient ischemic attacks, and from 40 to 82% in patients with other varieties of cerebrovascular disease.     

Beagle pup model of brain injury: regional cerebral blood flow and cerebral prostaglandins

Asphyxia is the most common cause of severe brain injury in very young children, and frequently results in lesions of the periventricular white matter in addition to other neuropathological changes. This study examines the effects of asphyxia on regional cerebral blood flow (rCBF) and the role of prostaglandins (PG's) in its control in the newborn beagle pup. Pups were anesthetized, tracheotomized, paralyzed, artificially ventilated, and randomly assigned to two groups: asphyxial insult produced by discontinuing ventilatory support, and no insult. Experiments for carbon-14-iodoantipyrine autoradiographic determination of rCBF and regional cerebral PG determination were performed on separate groups of pups. These studies demonstrated a significant increase in cortical gray PGE2 levels at a time when rCBF was significantly impaired in response to severe asphyxial insult. No such increase was noted in the periventricular white matter zones.