Somatosensory evoked responses during and after graded brain ischaemia in goats

Somatosensory evoked potentials (SEPs) were studied during graded incomplete cerebral ischaemia in eight goats and for the following 2 h. Anaesthesia was maintained with etomidate 1-1.5 mg kg-1 h-1 and 50% nitrous oxide in oxygen. Global cerebral blood flow (gCBF) was measured by a magnetic flow transducer at one internal maxillary artery after surgical occlusion of all other major extracranial cerebral arteries. CBF was reduced every 30 min by 25% with a lower limit of 15-20 ml 100 g-1 min-1. Regional cerebral blood flow (rCBF) in the brainstem and cortex was measured by the microsphere technique. The main findings were: (a) a graded decline in cortical SEP and a concurrent prolongation of the central conduction time (CCT) at gCBF values below 35 ml 100 g-1 min-1 and (b) an incomplete recovery of cortical SEP components during recirculation. Reduction of gCBF affected cortical rCBF more severely than brainstem rCBF. As a result, only cortical SEPs were changed. Our data suggest that reduced cerebral perfusion may result in altered cortical brain electrical activity that may be monitored by SEP recordings.     

Evaluation of extracranial-intracranial arterial bypass function by using near-infrared spectroscopy

OBJECT: It has been reported that extracranial-intracranial (EC-IC) arterial bypass surgery can be useful in preventing stroke in patients with hemodynamic compromise. Little is yet known, however, regarding the extent to which the bypass contributes to maintaining adequate cerebral blood oxygenation (CBO) and its temporal changes following surgery. The authors evaluated bypass function repeatedly by using near-infrared spectroscopy (NIRS) after surgery. METHODS: The authors investigated 30 patients who had undergone EC-IC bypass surgery. Single-photon emission computerized tomography revealed a decrease in regional cerebral blood flow (rCBF) and a lowered rCBF response to acetazolamide. Changes in CBO were evaluated in the sensorimotor cortex during compression of the anastomosed superficial temporal artery (STA). When decreases in oxyhemoglobin (HbO2) and total hemoglobin (Hb) concentrations were observed, the bypass was considered to have maintained CBO in the sensorimotor cortex given that decreases in HbO2 and total Hb indicate cerebral ischemic changes. The bypass maintained CBO immediately after surgery in 36.7% of patients (Group I, 11 patients) and at some time after surgery, mostly within 1 year, in 43.3% of patients (Group II, 13 patients); however, it did not maintain it throughout the follow-up period in 20% of patients (Group III, six patients). Note that the preoperative rCBF in patients in Groups I and II was lower than that in patients in Group III (p < 0.004). In fact, the preoperative rCBF predicted whether a bypass would maintain CBO at a cutoff value of 24.5 to 25 ml/100 g/min. Among Groups I and II, 18 patients demonstrated an increase in deoxyhemoglobin during STA compression. The preoperative rCBF in these cases was lower than that in the six remaining patients (p < 0.006). Note that the preoperative rCBF predicted the postoperative deoxyhemoglobin response at a cutoff value of 22.2 to 24 ml/100 g/min. CONCLUSIONS: The EC-IC bypass surgery can maintain CBO immediately after surgery or gradually within 1 year when the preoperative rCBF is below 24.5 to 25 ml/100 g/min. Furthermore, bypass flow plays a critical role in maintaining an adequate CBO when preoperative rCBF is below 22.2 to 24 ml/100 g/min.     

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.     

Clinical results of extracranial-intracranial bypass surgery in patients with hemodynamic cerebrovascular disease

The importance of hemodynamic factors in the pathogenesis and treatment of cerebrovascular disease remains uncertain. The extracranial-intracranial (EC-IC) bypass trial has been criticized for failing to identify and separately analyze those patients with chronic reduction in regional cerebral perfusion pressure (rCPP) who might be most likely to benefit from surgery. Positron emission tomography (PET) measurements of regional cerebral blood flow (rCBF) and blood volume (rCBV) were performed on 29 patients with symptomatic occlusion or intracranial stenosis of the carotid arterial system prior to undergoing EC-IC bypass surgery. Twenty-four patients had evidence of reduced rCPP (increased rCBV/rCBF ratio) distal to the arterial lesion. Of 21 patients who survived surgery without stroke, three suffered ipsilateral ischemic strokes during the 1st postoperative year. A nonrandomized control group of 23 nonsurgical patients' with similar clinical, arteriographic, and PET characteristics experienced no ipsilateral ischemic strokes during the 1st year following PET. Based on these results in 44 patients, the probability that successful surgery reduces the occurrence of ipsilateral ischemic stroke 1 year later was calculated. This probability ranged from 0.045 for a 50% reduction to 0.168 for a 10% reduction. Thus, there was little evidence to suggest that measurements of cerebral hemodynamics can identify a group of patients who would benefit from EC-IC bypass surgery.     

Improvement of oxygen metabolic reserve after extracranial-intracranial bypass surgery in patients with severe haemodynamic insufficiency

Summary The effectiveness of extracranial-intracranial arterial bypass (EC-IC bypass) surgery on impaired haemodynamic status was studied in 12 patients with reduced regional cerebral perfusion pressure (rCPP) and elevated regional oxygen extraction fraction (rOEF) in the area distal to the symptomatic arterial lesion. Postoperative positron emission tomography (PET) study demonstrated a statistically significant decrease of rOEF in the operated hemispheres with disappearance of the pre-operative interhemispheric rOEF difference. Regional cerebral blood flow (rCBF) and regional cerebral oxygen metabolism (rCMRO2) were also increased in the operated hemispheres with disappearance of the pre-operative interhemispheric differences. Regional CBF/regional cerebral blood volume (rCBV) ratios of the symptomatic hemispheres were increased after surgery, but were still lower than in the contralateral hemispheres. We conclude that EC-IC bypass surgery improves impaired cerebral oxygen metabolic reserve.     

Effects of preexisting bypass graft on rCBF and SSEP's following acute stroke in dogs

Regional cerebral blood flow (rCBF) was measured with radiolabeled microspheres in a canine model of superficial temporal artery-middle cerebral artery (STA-MCA) bypass and acute ischemia. Ischemic zone flows in seven dogs with the bypass first closed and then open showed no significant contribution of bypass flow in the intact vascular system. Following acute proximal occlusion, rCBF was preserved by bypass flow. A significant flow decrease ensued when the bypass was then clipped, confirming the adequacy of the lesion and the protective effect of the bypass. Reopening the bypass after 15 minutes of ischemia restored 76% of the previous flow. This was a significant increase from the global ischemia values, and was not statistically different from preocclusive values. Preocclusion somatosensory evoked potentials (SSEP's) in these animals showed a consistent biphasic wave at 8 to 10 msec after stimulation. This wave, with some decrease in amplitude, was preserved by bypass flow following creation of the arterial lesion. Bypass clipping abolished these ipsilateral SSEP's. Variable return of SSEP's occurred following reopening of the graft, but the recordings never reached preischemic amplitudes. This experimental study shows that, in this model, a prophylactic bypass subjected to immediate demand (with no time for "maturation") can adequately augment cortical rCBF and is superior to delayed revascularization. The data lend theoretical support to placement of a prophylactic STA-MCA bypass prior to elective carotid artery sacrifice or in surgery where the risk of acute vascular injury is high.     

Intra operative indocyanine green video-angiography in cerebrovascular surgery: An overview with review of literature

Microscope integrated Near infra red Indocyanine green video angiography (NIR ICG VA) has been frequently used in cerebrovascular surgery. It is believed to be a simple and reliable method with acquisition of real time high spatial resolution images. The aim of this review article was to evaluate the efficacy of intra operative Indocyanine green video angiography (ICG VA) in Aneurysm, brain arteriovenous malformations (AVM) and extracranial-intracranial (EC-IC) bypass surgeries and also to analyze its limitations. Intra operative imaging is a very useful tool in guiding surgery; thus, avoiding surgical morbidity. Now-a-days, many cerebrovascular units are using ICG VA rather than Doppler and intra operative DSA in most of their aneurysm surgeries, and surgeons are incorporating this technique for AVM and in EC-IC bypass surgeries too. This article is an overview of the beneficial effects of ICG VA in cerebrovascular surgery and will also point out its limitations in various circumstances. Intra operative ICG VA gives high resolution, real time images of arterial, capillary, and venous flow of cerebral vasculature. Although it gives adequate information about the clipped neck, parent/branching artery and perforator involvement, it has some limitations like viewing the neck residuals located behind the aneurysm, thick walled atherosclerotic vessels, and thrombosed aneurysms. In AVM surgery, it is useful in detecting the residual nidus in diffuse type AVM, but cannot be relied in deep seated AVMs and it gives exact information about the anastomosis site in EC-IC bypass, thus, avoiding early bypass graft failure. NIR ICG VA is a simple, reliable, and quick method to pick up subtle findings in cerebrovascular procedures. But in selected cases of aneurysms, endoscopy and intra operative Digital substraction angiography (DSA) may be helpful, whereas in deep seated AVMs, navigation may be required as an adjunct to confirm intra operative findings.     

Extracranial-intracranial bypass in atherosclerotic cerebrovascular disease: report of a single centre experience

Despite the failure of the international extracranial-intracranial (EC-IC) bypass study in showing the benefit of bypass procedure for prevention of stroke recurrence, it has been regarded to be beneficial in a subgroup of well-selected patients with haemodynamic impairment. This report includes the EC-IC bypass experience of a single centre over a period of 14 years. All consecutive 72 patients with atherosclerotic occlusive cerebrovascular lesions associated with haemodynamic compromise treated by EC-IC bypass surgery were retrospectively reviewed. Pre-operatively, 61% of patients presented with minor stroke and the remaining 39% with recurrent transient ischemic attacks (TIAs) despite maximal medical therapy. Angiography revealed a unilateral internal carotid artery (ICA) stenosis/occlusion in 79%, bilateral ICA stenosis/occlusion in 15%, MCA stenosis/occlusion in 3% and other multiple vessel stenosis/occlusion in 3% of the cases. H(2)(15)O positron emission tomography (PET) or 99mTc-HMPAO SPECT with acetazolamide challenge was performed for haemodynamic evaluation of the cerebral blood flow (CBF). All the patients had impaired haemodynamics pre-operatively in terms of reduced regional cerebrovascular reserve capacity and rCBF. Standard STA-MCA bypass procedure was performed in all patients. A total of 68 patients with 82 bypasses were reviewed with a mean follow-up period of 34 months. Stroke recurrence took place in 10 patients (15%) resulting in an annual stroke risk of 5%. Improved cerebral haemodynamics was documented in 81% of revascularised hemispheres. Patients with unchanged or worse haemodynamic parameters had significantly more post-operative TIAs or strokes when compared to those with improved perfusion reserves (30% vs.5% of patients, p<0.05). In conclusion, EC-IC bypass procedure in selected patients with occlusive cerebrovascular lesions associated with haemodynamic impairment has revealed to be effective for prevention of further cerebral ischemia, when compared with a stroke risk rate of 15% reported to date in patients only under antiplatelet agents or anticoagulant therapy.     

Specific recognition of arteriovenous malformations using Xenon-133 RCBF technique

Summary With respect to the methodology of the atraumatic Xenon-133 technique the problem whether or not the proposed and introduced arterial artifact (AA) truely represents radiation from intravascular volume and to what extent it affects regional cerebral blood flow (rCBF) calculation is unresolved.We performed rCBF measurements in 22 patients with angiomas to clarify this issue in those patients known to have pathologically enlarged intracranial vessels. P 4 — the parameter suggested to represent the AA — as well as the conventional blood flow parameter for gray matter (F 1) were compared to those of 50 volunteers using four criteria of abnormality: 1. intrahemispheric distribution, 2. interhemispheric differences of homologous detector pairs, 3. differences of mean hemispheric values, 4. visual evaluation of CBF maps.19 of the 22 patients with angioma fulfilled at least two of the four criteria of abnormality, in comparison to 1 of 50 volunteers. P4's sensitivity for detecting angiomas proved to be higher (86%) than the perfusion parameters of gray matter. Focal increase of P 4 proved to be highly specific for the presence of arteriovenous malformation (AVM, specifity 98%). A true arterial artifact exists in most instances in the presence of an AVM. Disregarding AA in the algorithm for calculation rCBF leads to an artificial overestimation of tissue flow in the region of the AVM.Abbreviations rCBF regional cerebral blood flow - AA arterial artifact - AVM arteriovenous malformation     

Hemodynamic compensation via an excimer laser-assisted, high-flow bypass before and after therapeutic occlusion of the internal carotid artery

OBJECTIVE: High-flow, extracranial-intracranial (EC-IC) bypass operations are performed to prevent strokes among patients with giant aneurysms who cannot tolerate internal carotid artery (ICA) occlusion. However, the volume flow through the bypass, compared with preoperative ICA flow, has not been evaluated for any type of bypass. We describe a prospective case study that tested the ability of the high-flow EC-IC bypass to replace the volume flow of the ipsilateral ICA after deliberate ICA occlusion. METHODS: Seven consecutive patients with giant aneurysms of the ICA who experienced test occlusion failure underwent nonocclusive, excimer laser-assisted, EC-IC bypass surgery before permanent ICA occlusion. Volume flow values in the ICAs, the basilar artery, the EC-IC bypass, and the middle cerebral arteries were measured with magnetic resonance angiography. RESULTS: No significant changes in volume flow to the ipsilateral and contralateral hemispheres were observed after bypass surgery and therapeutic ICA occlusion. Before bypass surgery, the volume flow through the ipsilateral ICA was 243 +/- 74 ml/min, that through the contralateral ICA was 264 +/- 32 ml/min, and that through the basilar artery was 141 +/- 43 ml/min. After bypass surgery and therapeutic occlusion of the ipsilateral ICA, the volume flow through the bypass was 199 +/- 72 ml/min, that through the contralateral ICA was 303 +/- 82 ml/min, and that through the basilar artery was 153 +/- 72 ml/min. No significant preoperative versus postoperative changes in middle cerebral artery flow were observed on either side. CONCLUSION: The flow through the high-flow EC-IC bypass was able to replace the volume flow of the ipsilateral ICA after deliberate ICA occlusion for the treatment of giant aneurysms.     

Bypass surgery in patients with intracranial stenotic lesions. Postoperative morbidity and angiographic findings

Postoperative morbidity in patients with intracranial stenotic lesions following extracranial-intracranial arterial (EC-IC) bypass is not well defined. A high rate of neurological complications associated with occlusion of the stenotic arteries after surgery has recently been reported. In the period June, 1976, to March, 1984, the authors performed EC-IC bypass procedures in 19 patients with intracranial stenotic arteries. Most of the patients were initially treated pharmacologically (usually by anticoagulant therapy). Surgery was performed if the symptoms recurred while the patients were under pharmacological treatment and if angiography confirmed arterial stenosis. Antiplatelet therapy was given until the day of surgery and during the entire follow-up period. No permanent postoperative morbidity was observed in the series. One patient, with stenosis of the left siphon, the A1 segment of the anterior cerebral artery, and the M1 segment of the middle cerebral artery, had a transient dysphasia and right hemiparesis (lasting 3 days) in the presence of an unchanged arterial stenosis. In five patients early postoperative angiography (at 5 to 21 days) revealed occlusion of previously stenotic arteries. In one patient the occlusion was disclosed only on a later angiographic study, 2 months after surgery. Although EC-IC bypass is generally not a very high-risk operation in patients with intracranial arterial stenosis, there is a high percentage of immediate postoperative occlusion, and the authors suggest caution in determining indication for surgical treatment.     

Is extracranial-intracranial bypass surgery effective in certain patients?

Cerebral revascularization can be performed through a variety of extracranial-intracranial (EC-IC) bypass operations, using several different donor and recipient vessels, interposition grafts, and anastomotic techniques. The choice of bypass option is dependent on many factors, including the goals of the operation and the availability and accessibility of particular donor and recipient vessels. Potential indications for EC-IC bypass fall into two major categories: (1) flow replacement, in the treatment of complex aneurysms or tumors that require vessel sacrifice and (2) flow augmentation, for treatment of cerebral ischemia. The effectiveness of EC-IC bypass for these indications is reviewed in this article.     

Cerebral revascularization: extracranial-intracranial bypass

Extracranial-intracranial (EC-IC) bypass remains an important revascularization technique for management of complex cerebrovascular disease. Despite evolving endovascular techniques, the role of bypass for the purpose of flow replacement prior to planned vessel sacrifice remains relevant for treatment of complex and fusiform aneurysms. The role of bypass for purposes of flow augmentation in the setting of cerebral ischemia is limited based on current data, but remains an important option for selected cases of athero-occlusive disease, in addition to a primary treatment for symptomatic moyamoya disease. An objective flow-based approach to EC-IC bypass can enhance decision-making in preoperative patient selection, intraoperative graft assessment, and postoperative follow-up.     

The clinical utility of the Kopitnik arteriovenous malformation microclip during STA-MCA bypass surgery

Purpose  

Yasagil temporary clips have been widely used in extracranial-intracranial (EC-IC) arterial bypass surgery. However, the extremely delicate vessels involved often require the application of finer clips. We report on the use of the Kopitnik arteriovenous malformation (AVM) microclip system for superficial temporal artery-middle cerebral artery (STA-MCA) bypass.     

Clinical application of the central somatosensory conduction time (CCT)

We tried to prove the usefulness of CCT as an index of cerebral functions. CCT, regional cerebral blood flow (CBF) and CT scan findings were studied in 213 neurological patients with CVD (66 cases), cerebral tumors (66 cases) and head traumas (81 cases). The technique of CCT recording was modified from that of Jones (1977) using CADWELL 5200 system. CCT was defined as the difference of the peak latency between N13 recorded at the C-7 vertebral electrode and N20 recorded at the somatosensory cortex. The control CCT in normal volunteers (N = 20) was 5.7 +/- 0.4 msec. RCBF was measured with 133 Xe intra carotid injection method of Lassen & Ingvar using gammacamera (DEC GAMM 11/34). CCT tended significantly to become more prolonged in affected hemisphere than in unaffected hemisphere of patients with three groups (CVD, tumor and trauma) (p less than 0.01). Forty percent reduction of control rCBF caused a prolongation of CCT over 7 msec. The degrees of CCT prolongations appeared to be proportional to the degree of rCBF diminution. Prolongation of CCT was remarkable in the side of low density area on CT scan. The prolongation of CCT were revealed in the patients before they did not manifest their neurological deficits especially in the disease of metastatic tumors and glioma. In the case of patients with trauma who we could follow to measure rCBF, CCT tended to become shorten as rCBF increased till normal range. CCT was not significantly prolonged in congenital hydrocephalus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Usefulness of intraoperative laser Doppler flowmetry and thermography to predict a risk of postoperative hyperperfusion after superficial temporal artery-middle cerebral artery bypass for moyamoya disease

We investigated whether postoperative hyperperfusion in moyamoya disease can be predicted using intraoperative laser Doppler flowmetry and/or thermography. A prospective study was conducted on 27 patients (39 hemispheres) with moyamoya disease who underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass. During surgery, regional cerebral blood flow (rCBF) was measured with a laser Doppler flowmeter and the temperature of the cortical surface was measured with an infrared thermograph. Postoperative hyperperfusion was assessed immediately after surgery based on CBF study under sedation (propofol) as >100% increase in corrected rCBF compared to preoperative values. Postoperative hyperperfusion on CBF was observed in two patients (7.4%). A significant correlation was observed between intraoperative rCBF changes and postoperative rCBF increase (Pearson's method: r=0.555, p=0.0003; simple regression: Y=1.22X+3.289, r (2)=0.308, p=0.0004). Furthermore, the rCBF changes measured by laser Doppler flowmetry were significantly greater in patients with postoperative hyperperfusion (p=0.0193) and CHS (p=0.0193). The present study suggests that intraoperative rCBF measurement using laser Doppler flowmetry may predict a risk of post-EC-IC bypass cerebral hyperperfusion in moyamoya disease.     

Emergency EC-IC bypass for symptomatic atherosclerotic ischemic stroke

Previous studies have shown that extracranial–intracranial (EC-IC) bypass surgery has no preventive effect on subsequent ipsilateral ischemic stroke in patients with symptomatic atherosclerotic internal carotid occlusion and hemodynamic cerebral ischemia. A few studies have assessed whether an urgent EC-IC bypass surgery is an effective treatment for main trunk stenosis or occlusion in acute stage. The authors retrospectively reviewed 58 consecutive patients who underwent urgent EC-IC bypass for symptomatic internal carotid artery or the middle cerebral artery stenosis or occlusion between January 2003 and December 2011. Clinical characteristics and neuroimagings were evaluated and analyzed. Based on preoperative angiogram, responsible lesions were the internal carotid artery in 19 (32.8 %) patients and the middle cerebral artery in 39 (67.2 %). No hemorrhagic complication occurred. Sixty-nine percent of patients showed improvement of neurological function after surgery, and 74.1 % of patients had favorable outcome. Unfavorable outcome was associated with insufficient collateral flow and new infarction after bypass surgery.     

Rupture of a giant carotid aneurysm after extracranial-to-intracranial bypass surgery

We report a case of a fatal rupture of a previously unruptured giant aneurysm of the bifurcation of the internal carotid artery (ICA), which occurred after an extracranial-intracranial (EC-IC) bypass and the partial occlusion of the ICA. Interim angiography showed retrograde filling of the proximal middle cerebral artery to the aneurysm. There have been four previously reported cases of giant aneurysms rupturing after treatment with an EC-IC bypass and carotid ligation, and it appears likely that a change in pressure/flow dynamics produced by the bypass may have been the cause. The technique of carotid ligation with an EC-IC bypass is used frequently to treat unclippable intracranial aneurysms, and the resulting hemodynamic changes need to be considered carefully to prevent this type of complication. To minimize hemodynamic stress on the aneurysm, we suggest that 1) the bypass caliber should be as small as possible consistent with sufficient cerebral blood flow after ICA occlusion, and 2) complete ICA occlusion should be performed as soon as possible after the bypass.     

The effect of low-flow cardiopulmonary bypass on cerebral function: an experimental and clinical study

Systemic flow rates (Q) during nonpulsatile hypothermic cardiopulmonary bypass (CPB) that are consistent with preservation of cerebral function have not to our knowledge been objectively defined. The effect of a sequential reduction in flow rates on cerebral cortical metabolism and function was evaluated in 6 mongrel dogs during hypothermic (25 degrees C) CPB. Cerebral function was assessed using somatosensory cortical evoked potentials (SSEP); cerebral metabolism was assessed by adenosine triphosphate (ATP) and lactate content of snap-frozen gray matter biopsies taken from the hemisphere contralateral to that monitored for SSEP. A progressive decline in ATP levels was observed during flow reduction with virtually complete depletion of ATP at 0.25 L min-1 m-2(p = .0003). The significant (p = .028) dependence of cortical ATP levels on perfusion pressure was no longer evident after adjusting for the effects of flow rate. Lactate levels increased during flow reduction (p = .028), especially at flow rates less than 0.5 L min-1 m-2. Somatosensory neural transmission remained intact until flow was reduced to 0.25 L min-1 m-2 in 5 animals and until total circulatory arrest in 1, at which time loss of the signal occurred. In addition, 5 patients were subjected to brief periods of low-flow CPB (Q = 1.0 L min-1 m-2) at 21 degrees to 25 degrees C. SSEPs remained intact during flow reduction, and postoperative neurologic evaluation was normal in all patients. We conclude that, in the absence of cerebral vascular disease, the flow rate threshold for incurring functional cerebral injury during hypothermic (25 degrees C) nonpulsatile CPB is less than 1.0 L min-1 m-2.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.