Proximal Posterior Cerebral Artery Research Articles

Evaluation of Brain Death by CT Angiography: Initial Experience

Purpose : The angiographic demonstration of absent cerebral blood flow is presently considered to be the most reliable method of confirming brain death. The purpose of this study is to determine whether CT angiography (CTA) with spiral CT can rapidly and specifically establish a diagnosis of brain death. Materials and Methods : A total of fifteen CT angiograms (brain death, n=9;severe coma, n=6 within 24 hours of the study) were obtained prospectively in 12 patients with an established clinical diagnosis; Two patients underwent repeated CTA. Twenty seconds after beginning the injection of contrast media (100 mL at a rate of 3 mL/sec), CT scanning (30 -second continuous exposure and 60 -mm length) was performed with a table speed of 2 mm/sec and a section thickness of 2 mm. For each case, the presence or absence of opacification of inter-nal carotid arteries (ICA), vertebral and basilar arteries (VBA), anterior cerebral arteries (ACA), middle cerebral arteries (MCA), posterior cerebral arteries (PCA), distal branches of cerebral arteries, and superficial temporal arteries (STA) was ascertained. Results : Except in one clinically brain-dead patient, whose EEG was difficult to interpret due to excessive arti-facts, the distal branches of cerebral arteries did not opacify. STA, on the other hand, was always visible on both sides. In all brain-dead patients but three, the ICA and proximal ACA, MCA, or PCA escaped visualiza-tion. In the remaining three cases with large skull defect or skull fracture, however, CT angiography showed faint opacification of the ICA and proximal segments of cerebral arteries. Cerebral arterial flow was preserved in all six patients in whom there was no clinical evidence of brain death. Conclusion : CTA may be used as a confirmatory test for the determination of brain death.

Traumatic brain injury does not alter cerebral artery contractility

Previous studies have shown that traumatic brain injury (TBI) significantly reduces cerebral blood flow determined in vivo and reduces vascular reactivity in the pial circulation measured with cranial window preparations. We have now tested the hypothesis that TBI induces these changes by impairing intrinsic contractile activity of cerebral arteries. Anesthetized rats underwent moderate (2.2 atm) and severe (3.0 atm) midline fluid percussion TBI or sham injury following which posterior cerebral or middle cerebral arteries were isolated and isometric force generation was measured. Moderate (n = 5) and severe (n = 3) trauma had no effect on the magnitude of serotonin- or K+-induced force generation or sensitivity to serotonin in arteries isolated within 10 min of TBI. Functional disruption of the endothelium of posterior cerebral arteries isolated 10 min after moderate trauma or sham injury caused a reduction in the active tension response to serotonin that was similar in both groups. Blockade of cyclooxygenase with 5 microM indomethacin had no effect on serotonin-induced force generated by vessels with moderate trauma or in sham-treated rats. Acetylcholine induced an endothelium-dependent relaxation of posterior and middle cerebral arteries; the magnitude of the response was unaffected by moderate TBI. To determine whether prolonged in situ exposure of vessels to the traumatized cerebral milieu could reveal an alteration in intrinsic contractility, posterior cerebral arteries were isolated 30 min after TBI; again, no differences in the tension or relaxation responses were observed. It is concluded that midline fluid percussion TBI did not affect contraction or relaxation of proximal middle or posterior cerebral arteries in rats.

後大脳動脈遠位部動脈瘤(P<SUB>3</SUB>動脈瘤)に対するoccipital interhemispheric approach

We discribe the occipital interhemispheric approach for an aneurysm on the distal posterior cerebral artery (PCA). The absence of adhesion of the occipital lobe to the falx and few bridging veins allow easy dissection between the bilateral occipital lobes. Utilization of gravity, osmotic agents, and removal of the cerebrospinal fluid provide an interhemispheric slot wide enough to observe and clip the aneurysm. Through the approach the proximal PCA, an aneurysm, and the distal PCA are located vertically as the middle cerebral artery and its aneurysm through the distal trans-Sylvian-fissure approach.

Cerebrovascular Enhancement in Spoiled GRASS (SPGR) Images

The signals and artifacts in cerebral blood vessels were systematically studied using a new three-dimensional Fourier transform (3DFT) technique, spoiled gradient recalled acquisition in steady state (SPGR), with parameters optimized for T1-weighted brain imaging. Twenty consecutive patients referred for routine cranial MR imaging were prospectively studied before and after the intravenous administration of Gd-DTPA using both 3DFT SPGR and conventional 2DFT SE imaging. A significant difference between the two techniques was noted in regard to the appearance of cerebral blood vessels and the degree of vascular pulsation artifact. Precontrast SPGR images demonstrated high signal in all (100%) internal carotid arteries and in nearly all (85-95%) vertebral, basilar, and proximal posterior, middle, and anterior cerebral arteries. High signal was variably present (5-50%) in more distal arterial branches. High signal from venous structures was not seen except in the superior sagittal sinus, which was bright in 75% of cases. Postcontrast SPGR images reliably demonstrated uniform high signal in all (100%) major arterial branches, up to fourth-order branches in the middle cerebral artery, diminishing toward the vertex. All (100%) major deep and superficial venous structures were of uniformly high signal, diminishing slightly as they exited the skull base. Flow related artifacts were found to be significantly (p = 0.001) reduced in contrast enhanced SPGR compared to SE images. As implemented in this study, SPGR and SE images demonstrate significantly different patterns of vascular signal that must be recognized for the proper interpretation of MR images.

Accelerated intracranial occlusive disease, oral contraceptives, and cigarette use

We report clinical and angiographic features of accelerated intracranial occlusive disease resembling moyamoya vasculopathy in five young women who used oral contraceptives (OCs) and smoked cigarettes, but generally had no other obvious risk factors for cerebrovascular disease. Three women had been on OCs for at least 4 years, one woman each had been on OCs for 3 months and for 2 weeks. All five women had smoked cigarettes for at least eight pack-years. Intermittent and progressive multifocal cognitive, visual, motor, or sensory hemispheric symptoms and signs developed in all. All patients developed strokes, four preceded by transient ischemic attacks. Cerebral angiography demonstrated bilateral supraclinoid internal carotid artery stenosis in four patients and proximal posterior cerebral artery stenosis in one. Additional features included rete mirabile, telangiectasias, prominent lenticulostriate collaterals, and multifocal distal cerebral branch occlusions. Three had mild abnormalities of serum fibrinogen, antinuclear antibody, erythrocyte sedimentation rate, or CSF IgG. After discontinuing OCs and reducing cigarette use, four women have not had further strokes over a mean follow-up of approximately 5 years. In certain young women, clinical and angiographic features resembling moyamoya may develop with the use of OCs and cigarettes. We speculate that an immunologically mediated vasculopathy may explain, in part, this unusual cerebrovascular syndrome in otherwise healthy young women.

Proximal posterior cerebral artery occlusion simulating middle cerebral artery occlusion

We describe 12 cases of acute stroke in which clinical features of proximal posterior cerebral artery occlusion simulated the clinical syndrome of middle cerebral artery occlusion. The majority of patients developed contralateral hemiparesis, homonymous hemianopia, hemispatial neglect, and sensory loss or sensory inattention. All 8 patients with dominant hemisphere lesions were aphasic. Accurate diagnosis in each case was achieved only after a head CT, showing occipital lobe, thalamic, and inferomesial temporal lobe infarction. "Cortical" signs are probably explained by thalamic involvement. Recognition of this syndrome has implications for management and prognosis.

Revascularization of the Calcarine Artery in Moyamoya Disease: OA-Cortical PCA Anastomosis

A 38-year-old male presented with moyamoya disease. Occlusion of the bilateral proximal posterior cerebral arteries (PCAs) resulted in homonymous 3/4 (right half and left lower quadrant) anopsia and various mental symptoms. To prevent impending cortical blindness, revascularization to the right PCA was performed by occipital artery (OA) to calcarine artery anastomosis. His neurological state was stabilized. OA-cortical PCA (calcarine artery) anastomosis is an alternative to omentum transplantation or occipital burr hole procedures for impending cortical blindness.

The Use of Electroencephalography and Brain Protection during Operation for Basilar Aneurysms

Abstract Intraoperative monitoring with electroencephalography and the use of brain protection with steroids, phenytoin, mannitol, and pentobarbital or etomidate were evaluated in 15 patients undergoing operation for an aneurysm of the upper basilar artery. One patient harbored a basilar trunk aneurysm, 1 an aneurysm of the proximal posterior cerebral artery, 3 an aneurysm of the superior cerebellar artery, and 10 an aneurysm at the basilar tip. The size of the aneurysms varied between 5 and 30 mm. Subarachnoid hemorrhage was the symptom exhibited in 12, mass effect the symptom in 2, and 1 patient was asymptomatic but had an angiogram because of amaurosis. There were 9 patients with multiple aneurysms, 5 of whom had aneurysms of the bilateral anterior circulation. Four patients underwent operation early. In 2 patients, the basilar artery was the sole or main blood supply of the whole brain. All patients except the one with the basilar trunk aneurysm were operated on via a transsylvian approach. All patients received 500 to 800 mg of phenytoin and 10 to 20 mg of dexamethasone shortly before and during surgery, and mannitol (0.8 g/kg) 15 minutes before the induction of hypotension or temporary clipping. Three patients showed slowing of electrical activity over the right hemisphere as a result of retraction of the internal carotid artery; with repositioning of the retractor, this disappeared within 10 minutes. Electrocortical silence was induced in 8 patients; this was in anticipation of prolonged moderate hypotension in 2, short deep hypotension in 2, temporary clipping of major vessels—including the basilar artery—in 2, and a combination of deep hypotension combined with temporary clipping in 2. At present, etomidate is preferred over thiopental for inducing electrocortical silence because it has no cardiovascular depressant effects, even in massive doses. Three patients awoke with contralateral hemiparesis, 2 of whom had spontaneous changes in the electroencep halogram and 1 in whom electrocortical silence was present for 1 hour. In all 3 patients, the electroencephalogram had returned to normal by the end of the operation, and the hemiparesis had completely resolved within 4 hours. One patient, in whom the basilar artery itself had ruptured and had to be occluded permanently, died. One patient, whose status was Grade 4 when operation was performed on Day 25, remained severely disabled. All other patients made a good recovery. The electroencephalogram was helpful in 10 cases (67%), and it allowed the surgeon to operate without stress in an unhurried manner and, when combined with pharmaceutical brain protection—even in the presence of deep hypotension—to perform temporary clipping.

The use of electroencephalography and brain protection during operation for basilar aneurysms.

Intraoperative monitoring with electroencephalography and the use of brain protection with steroids, phenytoin, mannitol, and pentobarbital or etomidate were evaluated in 15 patients undergoing operation for an aneurysm of the upper basilar artery. One patient harbored a basilar trunk aneurysm, 1 an aneurysm of the proximal posterior cerebral artery, 3 an aneurysm of the superior cerebellar artery, and 10 an aneurysm at the basilar tip. The size of the aneurysms varied between 5 and 30 mm. Subarachnoid hemorrhage was the symptom exhibited in 12, mass effect the symptom in 2, and 1 patient was asymptomatic but had an angiogram because of amaurosis. There were 9 patients with multiple aneurysms, 5 of whom had aneurysms of the bilateral anterior circulation. Four patients underwent operation early. In 2 patients, the basilar artery was the sole or main blood supply of the whole brain. All patients except the one with the basilar trunk aneurysm were operated on via a transsylvian approach. All patients received 500 to 800 mg of phenytoin and 10 to 20 mg of dexamethasone shortly before and during surgery, and mannitol (0.8 g/kg) 15 minutes before the induction of hypotension or temporary clipping. Three patients showed slowing of electrical activity over the right hemisphere as a result of retraction of the internal carotid artery; with repositioning of the retractor, this disappeared within 10 minutes. Electrocortical silence was induced in 8 patients; this was in anticipation of prolonged moderate hypotension in 2, short deep hypotension in 2, temporary clipping of major vessels--including the basilar artery--in 2, and a combination of deep hypotension combined with temporary clipping in 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of intracranial hemodynamics in carotid artery disease by transcranial Doppler ultrasound.

Noninvasive transcranial Doppler recordings were correlated to the angiographic findings in 77 patients with carotid artery disease. Stenoses reducing the luminal area of the internal carotid artery by 75% or more also reduced the pulsatility transmission index (PTI) of the ipsilateral middle cerebral artery (MCA). The PTI is the pulsatility index of the artery under study expressed as a percent of the pulsatility index of another intracranial artery with presumed unimpeded inflow in the same individual. For stenoses in the 75% to 89% category. PTI reduction was significantly greater in patients with bilateral carotid stenosis, indicating an impaired potential for collateral flow in these patients. The PTI reduction probably reflects both the pressure drop across the stenosis and the cerebral autoregulatory response. Two criteria proved useful in demonstrating collateral MCA supply through the circle of Willis. On the recipient side, retrograde flow in the proximal anterior cerebral artery was demonstrated in 29 of the 31 patients when this flow pattern was disclosed angiographically. In 26 of these patients, the anterior cerebral artery on the supplying side also had clearly increased flow velocity. Increased flow velocities in the proximal posterior cerebral artery were present in 26 of the 30 vessels that were acting as a collateral channel to the ipsilateral MCA.

Extracranial-intracranial bypass to the proximal posterior cerebral artery and to the proximal middle cerebral artery for multiple occlusive cerebrovascular disease

A 48-year-old man with a multiple occlusive cerebrovascular disease involving both the carotid and the vertebrobasilar systems is reported. Faced with noneffective conservative treatment, a surgical approach was carried out. As the patient had poorly developed posterior communicating arteries, two extracranial-intracranial bypasses were performed for both the carotid and the vertebrobasilar circulations; extracranial-intracranial bypasses with interposed saphenous vein grafts between the left external carotid artery and the proximal segment of the left middle cerebral artery, and between the right external carotid artery and the proximal segment of the right posterior cerebral artery. Advantages, precautions, and techniques of this kind of bypass procedure are discussed.

Long vein graft for EC/IC bypass surgery

The author performed 11 extracranial - intracranial (EC/IC) bypasses with interposed saphenous vein grafts, 10 for the anterior circulation and 1 for the posterior circulation. The revascularization for the posterior circulation was a bypass to the proximal posterior cerebral artery (P-3 segment). The patency rate of the bypasses with the vein grafts was 82%. Two bypasses were occluded postoperatively, probably because the vein grafts were twisted or the venous valves were not in good condition. The mean bypass flow rate of the EC/IC bypass with an interposed vein graft was 99 ml/min intraoperatively and 126 ml/min postoperatively. The mean values of the routine superficial temporal artery - middle cerebral artery (STA-MCA) anastomosis were 39 ml/min and 52 ml/min, respectively. The mean regional cerebral blood flow (M rCBF) which was measured postoperatively with 133Xe injection through the vein graft was 48.7 ml/100 g/min (PCO2 41.2 mmHg, n=5) which was within normal limits. On the other hand, the postoperative M rCBF in the cases of routine STA-MCA anastomosis, which was measured with 133Xe injection through the STA (donor) was 27.8 ml/100 g/min (PCO2 40.4 mmHg, n = 4). These data show that the EC/IC bypass with a vein graft increases the intracranial blood flow more significantly than the STA-MCA anastomosis. In the present series, 2 cases died postoperatively. One death was due to slipping out of the ligature which was placed at the side branch of the vein graft. The author recommends that the side branches should be ligated at two or three separate places. The other case had a multiple occlusive cerebrovascular disease and died due to myocardial infarction 2 days postoperatively. The preoperative Master ECG had been normal. Therefore, no coronary angiography had been performed. The autopsy showed, however, 90% and 60% stenoses of both coronary arteries. In cases of multiple occlusive disease, it is recommended that a coronary angiography should be performed before considering an operative intervention.

Interposition saphenous vein grafts for advanced occlusive disease and large aneurysms in the posterior circulation.

The authors report their initial experience with the use of interposition saphenous vein grafts between the external carotid artery and the proximal posterior cerebral artery. The indications, results, and technical aspects of the operation are reviewed. All patients accepted for surgery were at high risk for a posterior circulation infarct, and all patients with ischemic symptomatology had continued to progress while on anticoagulant drugs or anti-platelet agents. Thus, all patients were at high risk, and 11 of the 14 patients operated on were confined to bed before surgery. Intraoperative graft flows varied from 35 to 170 ml/min, and postoperative graft flows ranged from 75 to 311 ml/min in the patent grafts. There were three early graft occlusions and two late graft occlusions; these all occurred in patients with relatively low flows at the time of surgery (40 ml/min or lower). Subdural hygroma was the next most frequent complication to graft occlusion. It was thought to be caused by the pulsating graft anastomosed to a major vessel through a small opening in the basal arachnoid, which provided a new path for cerebrospinal fluid flow in patients with a degree of preexisting atrophy. One patient with a large aneurysm in the posterior circulation underwent proximal intracranial clipping of the vertebral artery and bypass grafting simultaneously. There were seven excellent results and two good results in nine patients in whom the graft remained patent. In the five patients with graft occlusion, there were two minor strokes, two major strokes, and one death.

The microsurgical anatomy of the basilar artery bifurcation.

The vascular microsurgical anatomy in the area of the basilar artery bifurcation is described in 30 autopsy dissections. Particular emphasis is placed on variations of the posterior thalamoperforators and their relation to the proximal posterior cerebral artery and basilar bifurcation.