Effects of hypercapnia on cerebral blood flow following prophylactic and delayed experimental superficial temporal artery-middle cerebral artery bypass

Cerebral blood flow was studied in dogs to ascertain whether preexisting superficial temporal artery-middle cerebral artery bypass could preserve hypercapnic reactivity following acute ischemia and whether postischemic-delayed revascularization would restore hypercapnic reactivity. In six dogs flow was preserved and some degree of hypercapnic response remained following proximal occlusion with a patent bypass. During complete ischemia (bypass occluded) there was no hypercapnic reactivity in the ischemic zone. Significant flow was restored to the ischemic area following bypass reopening, but a cerebral blood flow decrease was seen with subsequent hypercapnia. In the opposite (control) hemisphere hypercapnia always produced significant cerebral blood flow increases. These data support the superiority of prophylactic over delayed superficial temporal artery-middle cerebral artery bypass in appropriate clinical situations.     

A study of regional cerebral blood flow before and after superficial temporal artery-to-middle cerebral artery anastomosis

Regional cerebral blood flow (rCBF), using a single photon emission CT with Xe-133 inhalation method, was measured before and after the operation in 30 patients who underwent a superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis. The purpose of this study is to assess the effect of STA-MCA anastomosis from the standpoint of hemodynamics and the results obtained were as follows: rCBF at rest increased after the operation, which was approximately 10% alterations and was localized in temporal region of operated hemisphere and frontal region of non-operated hemisphere respectively. rCBF during STA compression test after surgery decreased only in temporal region (anastomotic site) of operated hemisphere. This findings might indicate that blood flow via the bypass artery become to provide mainly to the confined area. CO2 reactivity was disturbed in 6 patients before operation, but it restored in 4 patients after operation. Autoregulation was also abolished in 8 patients before operation, but it restored in 6 patients after operation. In the group of severe degree of ischemia, however, autoregulation did not show the tendency to recover after the operation, whereas CO2 reactivity somewhat recovered. Angiographical retrograde filling which indicates collateral circulation reduced or disappeared in 12 out of 14 patients, in which postoperative rCBF in temporal region increased, in addition autoregulation and CO2 reactivity tended to recover after the bypass operation. These data mentioned above probably indicated the influences of CBF increase via the bypass artery. In summary, it might be concluded that the hemodynamic change such as disappearance of collateral circulation seen on angiography, additionally postoperative rCBF increase in anastomotic site seemed to be related to the restoration of these vascular responses such as CO2 reactivity and autoregulation in ischemic brain.     

Cerebral autoregulation following prophylactic and delayed experimental STA-MCA bypass

Summary Cerebral autoregulation is impaired in ischaemic regions. We hypothesized that pre-existing STA-MCA bypass would be superior to delayed revascularization in maintaining ipsilateral rCBF and preserving cerebral autoregulation following experimental stroke. Two series of dogs were tested to evaluate this hypothesis, but which was disproved for the chosen experimental conditions.In the first, eight dogs underwent craniotomy, STA-MCA bypass, and radiolabeled microsphere rCBF determinations. Blood pressure was manipulated with intravenous adenosine and levarterenol. Ischaemic zone rCBF was measured at MAP 60 mm Hg (97.2 ml·min^–1·100 g^–1) and MAP 140 mm Hg (113.6) (p=NS), in the intact arterial system with the patent bypass in place. An hemispheric ipsilateral ischaemic lesion was then created, and three further microsphere rCBF determinations were made at MAP 60 mm Hg (41.7ml·min^–1·100 g^–1), MAP 100 mm Hg (52.6) and MAP 140 mm Hg (58.3). There were no significant differences between these measurements (ANOVA p=NS).In a second series of five animals the bypass was placed and the stroke lesion created first. Ischaemic zone rCBF was then measured at MAP 60 mm Hg (35 ml·min^–1·100 g^–1) and MAP 140 mm Hg (44 ml·min^–1·100 g^–1) (p=NS), with the patent bypass in place. The bypass was then clamped for 15 minutes and profound ischaemia confirmed (5 ml·min^–1·100 g^–1, p < 0.05). Three further microspherer CBF determinations were made following bypass reopening at MAP 60 mm Hg (29 ml·min^–1·100 g^–1), MAP 100 mm Hg (33 ml·min^–1·100 g^–1) and MAP 140 mm Hg (36 ml·min^–1·100 g^–1). There were no significant differences between these measurements (ANOVA p=NS).In the first series hypertension did not significantly affect rCBF in the intact system. The risk of a prophylactic bypass producing deleterious flow increases thus appears minimal. In both series no significant rCBF changes occurred despite extremes of blood pressure in the post-occlusive hemisphere protected by a pre-existing bypass. In the second series ischaemic zone rCBF was not significantly affected by hypo- or hypertension even following fifteen minutes of profound ischaemia with delayed revascularization.Both prophylactic and delayed revascularization were effective in preserving ischaemic zone autoregulatory function, disproving our hypothesis. These data support the continued utility of prophylactic or delayed STA-MCA bypass in clinical situations when the potential for acute vascular injury is high.     

Regional cerebral blood flow and oxygen utilization in superficial temporal-middle cerebral artery anastomosis patients: an exploratory definition of clinical problems.

Regional cerebral blood flow (rCBF) and regional cerebral oxygen utilization (rCMRO2) were measured before and after surgery in nine patients undergoing a superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis to bypass cerebrovascular lesions not amenable to extracranial operative procedures. The objective of these studies was to determine whether measurements of this type could provide objective criteria for surgery as well as assess the effect of surgery. The preliminary data, although limited, suggest that measurements of regional cerebral hemodynamics and metabolism in these patients before and after surgery provide valuable data upon which to develop criteria and assess results. For example, 1) a significant depression of rCBF and rCMRO2 in patients in whom a major cerebral infarction has not occurred, or 2) relative preservation of rCMRO2 despite depressed rCBF seem to be favorable indications for establishing a functioning STA-MCA anastomosis. In such patients, STA-MCA anastomosis can be followed by a return of rCBJ and rCMRO2 to virtually normal levels. Relatively normal rCBF and rCMRO2 in the presence of an occluded internal carotid artery in asymptomatic patients indicates satisfactory collateral circulation and is probably a contraindication to surgery.     

颞浅动脉-大脑中动脉搭桥术治疗成人烟雾病效果分析

目的分析颞浅动脉-大脑中动脉搭桥术治疗成人烟雾病(MD)的效果。方法收集2017-06-2020-01间在惠州市第一人民医院接受颞浅动脉-大脑中动脉(STA-MCA)搭桥术的30例MD患者的临床资料,进行回顾性分析。结果术后6个月患者的神经功能评分(mRS)明显优于术前,差异有统计学意义(P<0.05)。术后3个月时脑血流量(rCBF)、相对脑血容量(rCBV)均高于术前,相对平均时间(rMTT)、相对达峰时间(rTTP)均低于术前,差异均有统计学意义(P<0.05)。术后复查造影示吻合口通畅,无严重并发症。结论STA-MCA术治疗成人MD,效果显著、安全性高,能增加缺血区域的脑血流量、减少烟雾状血管的生产、改善神经功能和降低脑卒中的风险。     

Regional cerebral blood flow studies following superficial temporal-middle cerebral artery anastomosis.

Regional cerebral blood flow (rCBF) studies were performed during the postoperative period on 16 patients with internal carotid occlusions and inaccessible stenoses, and middle cerebral artery occlusion and stenoses, who underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomoses. The intra-arterial xenon method with selective application of the xenon bolus through the internal carotid and the newly established superficial temporal channel has allowed comparison of the flow provided by the pathological input with flow through the new input. The results show that initial rCBF (rCBF1) was globally reduced in all patients to a mean of 28.4 +/- 11.9 ml/100 gm/min at a mean pCO2 of 29.6 +/- 9.55 mm Hg. Patients with transient ischemic attacks (TIA) and minor strokes with minimal residua (RIND) had a mean rCBF1 of 30.4 +/- 11.6 ml/100 gm/min at a mean pCO2 of 30 +/- 10 mm Hg, while patients with completed strokes had a mean rCBF1 of 25.0 +/- 12.4 ml/100 gm/min at a mean pCO2 of 29.1 +/- 8.8 mm Hg. There was no significant difference between these two groups. This finding suggests that in this small group of patients with TIA's and RIND's, the cause of the stroke is probably related more to decreased perfusion than embolus, and may explain why these patients' symptoms improve after STA-MCA anastomosis. The results of this study suggest that in addition to an inaccessible lesion, global or focal decreased rCBF is a necessary criterion in the definition of indications for intracranial revascularization procedures.     

Intraoperative monitoring of cerebral blood oxygenation and hemodynamics during extracranial-intracranial bypass surgery by a newly developed visible light spectroscopy system

BACKGROUND: Cerebrovascular reconstruction procedures run the risk of changing the balance between oxygen supply and consumption during surgery. We assessed the value of visual light spectroscopy for detecting changes in cerebral blood oxygenation (CBO) during superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. METHODS: We developed a VLS monitoring system which permits continuous monitoring of CBO changes during surgery. Using the VLS, we evaluated the CBO changes in the MCA territory on the lesion side in 18 patients who underwent STA-MCA anastomosis. RESULTS: Temporary occlusion of the MCA (M4 portion) did not change the CBO in 17 patients. However, in the patient with dissecting aneurysm, it caused decreases of oxyhemoglobin and cortical oxygen saturation (CoSo(2)) associated with an increase of deoxyhemoglobin, although these CBO changes were normalized by STA blood flow. In 5 patients, STA blood flow increased the oxyhemoglobin and CoSo(2) and decreased the deoxyhemoglobin, indicating that cortical blood flow (CoBF) was increased. The CoSo(2) before anastomosis was significantly low in the patients who showed an increase of CoSo(2) by STA blood flow (63.0% +/- 2.5%) as compared with those who did not (72.0 +/- 6.1%, P = .024). CONCLUSION: Temporary occlusion of a cortical artery during bypass surgery did not affect the CBO in patients who had chronic cerebral ischemia, but caused acute ischemia in the patient who did not. STA blood flow increased the CoBF during surgery more frequently in patients who showed a low perfusion pressure. The VLS monitoring system is considered useful for evaluating bypass function and facilitates safe and accurate bypass surgery.     

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.     

STA-MCA anastomosis in patients with skull base tumours involving the internal carotid artery—Haemodynamic assessment by ultrasonic Doppler flowmeter

Summary The role of superficial temporal artery -middle cerebral artery (STA-MCA) anastomosis was investigated with an ultrasonic Doppler flowmeter in 3 patients with sphenoid ridge meningiomas and one with a parasellar malignant teratoma, all of which involved the intracranial internal carotid artery. The intraoperative Doppler flow study revealed a remarkable increase in flow volume of the STA after trial occlusion of the middle cerebral artery in one case and permanent occlusion in two cases. These results substantiate the effectiveness of STA-MCA anastomosis. We also discuss surgical and other contrivances for obtaining sufficient blood supply from this bypass to prevent cerebral ischaemia in the acute phase after elective or accidental occlusion of a major cerebral artery. This is the first report of STA-MCA anastomosis in cases with brain tumour.     

Measurement of regional cerebral blood flow and somatosensory evoked potentials in a canine model of hemispheric ischemia

Regional cerebral blood flow (rCBF) was studied using the radiolabeled microsphere technique in a canine model of hemispheric ischemia that others have previously examined morphologically with carbon perfusion. It was our goal to ascertain whether this ischemic model, which involves easily accessible occlusions of the ipsilateral circle of Willis, could produce reproducible and significant reduction of hemispheric cerebral blood flow. Seven animals underwent the surgical procedure with measurements of rCBF at base line, after arterial microdissection and brain retraction only, and finally after creation of the lesion. Simultaneous somatosensory evoked potential recordings were also obtained. Bilateral symmetrical flow decreases were referable to anesthetic normalization and maintenance alone before creation of the lesion. The arterial occlusions, however, produced further significant decreases in flow on the ipsilateral side only, sparing all contralateral structures and sparing the brain stem and cerebellum bilaterally. Evoked responses, which had shown no changes in latency or amplitude after dissection and retraction procedures, were completely abolished 15 minutes after the arterial occlusion. Control animals that underwent surgical positioning and anesthesia alone did not show concomitant decreases is rCBF. This model of open craniotomy and direct vascular occlusion is suitable for studies of cerebral ischemia where the therapeutic intervention proposed (such as cerebral revascularization) involves similar surgical manipulations. By this method, a standard and reproducible ischemic lesion is achieved through the surgical field without the need for exposure of the basilar artery.     

Clinical experience with extra-intracranial arterial anastomosis in 65 cases.

Clinical results of an extra-intracranial arterial bypass (EIAB) procedure for cerebral ischemia are assessed in 65 patients. The 5-year-study suggests that the EIAB procedure has a protective effect against further clinically significant cerebrovascular accidents in properly selected patients. Correlation with angiography and regional cerebral blood flow (rCBF) studies are discussed. It is felt that rCBF measurements offer the best diagnostic test to determine which patients are suitable for surgery by revealing if an ischemic or relative ischemic focus is present. The surgical procedure is contraindicated in acute cerebral ischemia and when the rCBF study reveals general reduction of cerebral blood flow as opposed to a localized ischemic focus.     

Hemodynamic evaluation of vascular reconstructive surgery for childhood moyamoya disease using single photon emission computed tomography.

To evaluate the efficacy of vascular reconstructive surgery for childhood moyamoya disease, the cerebral blood flow (CBF) in 31 hemispheres of 16 patients was examined by single photon emission computed tomography (SPECT) using the 133Xe inhalation method. Results were divided into two groups; 17 hemispheres with superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis [A(+) group] and 14 hemispheres without anastomosis [A(-) group]. The mean hemispheric CBF (mCBF) and regional CBF (rCBF) in the frontal, temporal, occipital, and basal ganglia regions were calculated. Pre- and postoperative SPECT on the 10 hemispheres of the A(+) group showed an increase in mCBF in 6 hemispheres, the disappearance of the low perfusion area (LPA) in all 5 hemispheres where LPA was present before surgery, and an improvement in rCBF distribution (an increase in rCBF in the frontal and temporal lobes and a decrease in the basal ganglia). This suggests that vascular reconstruction is greatly effective in treating this disease. A comparison between the A(+) group and the A(-) group by postoperative SPECT, as well as the clinical outcomes and the postoperative findings of electroencephalography and angiography, revealed that the A(+) group was superior to the A(-) group in the frequency of LPA (12% and 43%, respectively) and rCBF in the frontal region where STA-MCA anastomosis was usually performed. These results indicate that STA-MCA anastomosis with indirect synangiosis is the most effective treatment of childhood moyamoya disease.     

Extra-intracranial bypass and internal carotid artery ligation in one-stage operation for intracavernous and giant carotid aneurysm

The combined one-stage operations, STA-MCA anastomosis and internal carotid artery (ICA) ligation (or trapping) were carried out in 11 cases (Age): 18-79 yrs, Av.: 45.8 yrs) of ICA aneurysms which were inaccessible for a direct operation because of their locations and sizes. First the STA-MCA anastomosis was performed under general anesthesia. Then the patient was awaken and thereafter under local anesthesia the ICA was temporarily clamped for 30 min. under induced hypotension to check whether any ischemic signs appeared. This was followed by proximal ICA ligation when no ischemic signs were observed. In all 11 cases, the anastomosis was patent. The aneurysms disappeared. Neither cerebral ischemia nor rebleeding from the aneurysms was seen during the long follow-up. The mean value of the bypass flow was 119 m/min which was twice as much as that in the cases of other occlusive cerebrovascular diseases and which was about one third of the blood flow of the ICA. Cerebral blood flow measurements through 133Xe inhalation method revealed that there was no difference in rCBF values between the operated and non-operated sides and that their values were within normal limits. The postoperative blood pressure was unchanged in 42% of our 11 cases, temporarily elevated and thereafter normalized in 33% and persistently elevated in 25%. Ophthalmodynamometry showed that the pressure of the central retinal artery decreased postoperatively in a degree of 5-10% in comparison to the non-operated side. No visual impairment was observed postoperatively (except case 3, see the text). These combined operations, STA-MCA anastomosis and ICA ligation were beneficial in preventing the potential postoperative cerebral ischemia. Intra-arterial pressure measurements of the STA and MCA suggested that the one-stage operations of these two procedures are better than the two-stage operations for the patency of the anastomosis because the pressure gradient between the donor and recipient vessels is increased (from 10.3 mmHg to 49.3 mmHg) by this technique. Temporary ICA clamp for 30 min. under induced hypotension in local anesthesia is useful to check whether the one-stage operations can be tolerated or not. EC/IC bypass with an interposed saphenous vein graft is a more beneficial surgical technique than a routine STA-MCA anastomosis, because an immediate and larger amount of bypass flow can be obtained.     

A case of spontaneous fusiform aneurysm in a middle cerebral artery branch which causes rapidly thrombosed formation in a short period

A 61-year-old man presented with the complaint of headache. Investigations revealed a fusiform middle cerebral artery aneurysm at the M2 part. The formation of the aneurysm rapidly developed to a partially thrombosed aneurysm in the course of four months. As regards the treatment of the aneurysm, at first we tried surgery with a superficial temporal artery middle cerebral artery bypass (STA-MCA bypass) and trapping of the aneurysm. However, during the procedure, it was difficult to control bleeding from the temporal muscle, bone flap, and subdural space. Because of this, we finished the STA-MCA bypass without trapping of the aneurysm and then, four days later, we confirmed bypass patency and treated the aneurysm using endovascular coil embolization. Based on both surgical and interventional investigations in this case and a review of the reported literature, the authors propose that there are two mechanisms causing the middle cerebral artery fusiform aneurysm to develop thrombosed formation rapidly: (i) Peripheral middle cerebral artery branches demand less blood flow than other major trunk arteries. (ii) Bypass flow maintains perfusion to the distal branches. On the other hand, this flow alteration caused by surgical vascular bypass may promote the development of the aneurysm to thrombosed formation. The treatment of a fusiform middle cerebral artery aneurysm at the M2 part is also discussed.     

Diagnostic value of perfusion-weighted MRI for evaluating postoperative alteration of cerebral hemodynamics following STA-MCA anastomosis in patients with moyamoya disease

OBJECTIVE: Surgical revascularization for moyamoya disease prevents cerebral ischemic attacks by improving cerebral blood flow (CBF). But little is known about the changes of CBF and its effect on neurological status during the acute stage after direct bypass for moyamoya disease. METHODS AND RESULTS: Perfusion-weighted magnetic resonance imaging (PWI) by the SE-EPI method was performed 4 and 10 days after superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis on 11 sides of 9 patients (male:female = 2:7, 24-61 years old) with moyamoya disease. All patients underwent single-photon emission computed tomography (SPECT) 1 and 7 days after surgery. The time-to-peak (TTP) by PWI showed focal decrease at the site of the anastomosis 4 days after STA-MCA anastomosis compared to preoperative TTP, and was further decreased in larger territory 10 days after surgery in all patients. Postoperative cerebral blood volume (CBV) by PWI showed significant increase compared to preoperative CBV in four patients who suffered symptomatic cerebral hyperperfusion after surgery. Postoperative SPECT revealed apparent increase of CBF in all patients and the patency of the STA-MCA bypass was confirmed by MRA. All patients were discharged without neurological deterioration compared to preoperative neurological status, and none of them suffered ischemic attack after surgery. CONCLUSION: Postoperative decrease in TTP by PWI could be a sensitive parameter for the normalization of CBF after STA-MCA anastomosis in patients with moyamoya disease. Postoperative increase in CBV may suggest cerebral hyperperfusion and could be the optimal predictor for hyperperfusion syndrome after STA-MCA anastomosis in patients with moyamoya disease.     

Efficacy of Direct Revascularization in Adult Moyamoya Disease: Haemodynamic Evaluation by Positron Emission Tomography

Summary  To evaluate the efficacy of direct cerebrovascular reconstruction to prevent intracranial bleeding from the point of view of haemodynamic status, we performed positron emission tomography (PET) studies in 5 adult patients with Moyamoya disease before and after superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis. Regional cerebral blood flow (rCBF), regional cerebral metabolic rate of oxygen (rCMRO₂) and regional oxygen extraction fraction (rOEF) in the MCA territories and regional cerebral blood volume (rCBV) in the striatum were measured before and after STA-MCA anastomosis. Correlation between the change of these PET parameters and post-operative decreased opacification of Moyamoya vessels were analyzed. Pre-operatively, significant elevation of rCBV were observed in the basal ganglia as well as significant reduction of rCBF and elevation of rOEF with reduction of rCMRO₂ in the MCA territories, indicating “misery” perfusion in the cerebral hemisphere and blood pooling in the Moyamoya vessels under increased haemodynamic stress. Post-operative PET study showed improvement of misery perfusion and reduction of rCBV in the basal ganglia. Reduction of rCBV in the basal ganglia generally compatible with decreasing Moyamoya vessels on angiographic findings. Our results suggests that direct bypass surgery could have a potential both for decreasing haemodynamic stress on Moyamoya vessels and to improve misery perfusion in the hemisphere.     

Changes in Computed Tomography Perfusion Parameters after Superficial Temporal Artery to Middle Cerebral Artery Bypass: An Analysis of 29 Cases

Introduction Analysis of computed tomography perfusion (CTP) studies before and after superficial temporal artery to middle cerebral artery (STA-MCA) bypass is warranted to better understand cerebral steno-occlusive pathology. Methods Retrospective review was performed of STA-MCA bypass patients with steno-occlusive disease with CTP before and after surgery. CTP parameters were evaluated for change after STA-MCA bypass. Results A total of 29 hemispheres were bypassed in 23 patients. After STA-MCA bypass, mean transit time (MTT) and time to peak (TTP) improved. When analyzed as a ratio to the contralateral hemisphere, MTT, TTP, and cerebral blood flow (CBF) improved. There was no effect of gender, double vessel versus single vessel bypass, or time until postoperative CTP study to changes in CTP parameters after bypass. Conclusions Blood flow augmentation after STA-MCA bypass may best be assessed by CTP using baseline MTT or TTP and ratios of MTT, TTP, or CBF to the contralateral hemisphere. The failure of cerebrovascular reserve to improve after cerebral bypass may indicate irreversible loss of autoregulation with chronic cerebral vasodilation or the inability of CTP to detect these improvements.     

Effects of verapamil and diltiazem on acute stroke in cats

To test the effect of verapamil and diltiazem in acute stroke, three groups of mongrel cats of either sex underwent occlusion of the middle cerebral artery (MCA) via a transorbital approach under ketamine anesthesia. The first group served as controls, the second received an intravenous infusion of verapamil (0.1 microgram/kg/min), and the third received an intravenous infusion of diltiazem (0.1 to 1.0 microgram/kg/min). All drug infusions began 2 hours before MCA occlusion and continued for the remainder of the experiment. Before and for up to 24 hours after MCA occlusion, regional cerebral blood flow (rCBF), somatosensory evoked potentials (SSEP's), arterial blood gases, blood pressure, temperature, and hematocrit were measured at least every 2 hours. At the experiment's end, brains were perfused with India ink, removed, sliced, photographed for determination of nonperfused brain area, and weighed, dried, and reweighed for H2O content determination. In these studies, verapamil was associated with worsening of rCBF in ischemic regions and inappropriate increases in rCBF in nonischemic regions, indicating intracerebral steal. Diltiazem increased rCBF in marginally ischemic regions. Changes in SSEP's paralleled blood flow changes, with verapamil decreasing amplitude and conduction velocity while diltiazem slightly improved conduction in the ischemic brain. Verapamil increased the area of nonperfused brain and the content of cerebral H2O. Diltiazem-treated animals had decreased cerebral H2O content, but had a marked increase in the area of nonperfused brain, a finding associated with the high incidence of transtentorial herniation in the diltiazem-treated animals. These findings agree with in vitro studies demonstrating high sensitivity of cerebral blood vessels to calcium channel blockers. These studies further support the notion that calcium channel blockers probably affect several different classes of calcium channels, at different brain sites.     

Follow-up results after STA-MCA anastomosis in cases of middle cerebral artery stenosis

To elucidate hemodynamic changes and prognosis after STA-MCA anastomosis, thirteen cases with middle cerebral artery stenosis were systematically analyzed from the pre- and postoperative findings of cerebral angiography, CT scan and rCBF. They were followed up about 3 years long on the average postoperatively. Postoperative angiography revealed patent bypass in all cases. No remarkable changes at the site of stenosis were observed in the group A (6 in 13 cases), who had angiographically sufficient inherent collateral circulation. By contrast, group B (7 in 13 cases), who had insufficient inherent collateral circulation, showed remarkable progress in the degree of stenosis and significant changes of flow patterns were observed after operation. However, these postoperative changes did not bring any clinical deterioration. During follow-up period (31.2 months on the average) after operation, no cerebrovascular accident were encountered in all cases and clinically improved. In conclusion, the STA-MCA bypass rendered more beneficial effect to the patient with MCA stenosis when compared with natural histories reported in the literature.     

Anastomosis of the superficial temporal artery to the middle cerebral artery for occlusive disease of the bilateral internal carotid arteries with dementia

Two cases are reported of occlusive disease of the bilateral internal carotid arteries with dementia in which the anastomosis of the superficial temporal artery to the middle cerebral artery (STA-MCA bypass) resulted in marked improvement in clinical aspects. One patient was a 29-year-old male who complained of transient weakness of the extremities and memory impairment. Computerized tomography (CT) scans showed multiple small infarctions, while cerebral angiography demonstrated findings of Moya-like disease. The cognitive function tests were subnormal and the study of cerebral blood flow (CBF study) showed diffuse low flow in both hemispheres. Based on his clinical symptoms and CBF study, the STA-MCA bypass was performed on both sides in two stages without complications. Postoperatively, his clinical symptoms and cognitive function improved gradually, in accordance with increased CBF in both hemispheres. Six months after the operation, cognitive function tests were within normal limits. Another patient was a 61-year-old hypertensive male who complained of motor weakness, impairment of memory and urinary incontinence. CT scans showed multiple small infarctions, while cerebral angiography revealed occlusion of both internal carotid arteries at the cervical portion. The cognitive function was at the pre-dementia level, and CBF study revealed diffuse low flow in both hemispheres. Based on the clinical symptoms and CBF study, the STA-MCA bypass was performed on both sides in two stages. Postoperatively, clinical symptoms and cognitive function markedly improved. From our results, the diagnosis of vascular dementia, and indications for the use of STA-MCA bypass in this category of patients are discussed.