Posterior Cerebral Artery Occlusion Research Articles

Causes, clinical and imaging characteristics of moyamoya disease in children

Introduction: Moyamoya disease is a progressive, chronic occlusive vascular disease of the circle of Willis arteries leading to the development of collateral circulation to compensate the occlusion. Purpose: This study aims to investigate the potential causes and clinical and imaging characteristics of Moyamoya Disease (MMD) in children. Methods: A retrospective analysis was performed on the clinical data of 14 MMD children, in which the potential causes were analysed, and the clinical and imaging characteristics were observed. Results: The average patient age was 6.15 y (range 21 months-13 y), and the female/male ratio was 1.3:1.0. There were 332 cases of ischemia and 196 hemorrhages. Eight cases had inducing factors including five cases of upper respiratory tract infection. Twelve cases exhibited limb weakness or hemiplegia. Among these patients, eight cases developed these manifestations as initial symptoms. Furthermore, seven cases presented language barriers, two cases had twitch, and two cases had headaches with unclear vision. All 14 patients underwent cranial Magnetic Resonance Imaging (MRI) and the results revealed that twelve cases had cerebral infarction, and two cases had cerebral hemorrhage. Five of 14 patients experienced stenosis or occlusion at the siphon part of the bilateral internal carotid arteries, seven patients had bilateral anterior cerebral artery stenosis or occlusion, 8 were bilateral middle cerebral artery stenosis or occlusion, and 2 were bilateral posterior cerebral artery stenosis or occlusion. All patients smoke-like vessels in the basal ganglia region. Conclusion: High-risk age of child MMD ranged between 4-10 y old, which mostly manifested as transient cerebral ischemic insults; and inducing factors were mostly upper respiratory tract infections.

Resolution of Anton–Babinski syndrome after systemic thrombolysis and mechanical thrombectomy with a stentriever

Anton–Babinski syndrome is a rare neuropsychiatric syndrome characterized by bilateral cortical blindness and anosognosia with visual confabulation. We present the case of a patient presenting with occlusion of both posterior cerebral arteries (PCA), with Anton–Babinski syndrome, completely solved after combined systemic thrombolysis and mechanical thrombectomy with a stent-retriever.

Superficial Temporal Artery: Distal Posterior Cerebral Artery Bypass through the Subtemporal Approach: Technical Note and Pilot Surgical Cases

Posterior cerebral artery (PCA) aneurysms are rare and the majority are fusiform in shape. Proximal occlusion of PCA represents a treatment option for these lesions. However, this procedure carries a high risk of ischemic complications. To describe the technique of trapping a fusiform PCA aneurysm and revascularization of the distal PCA using a superficial temporal artery (STA) graft through the same microsurgical approach. From September 2012 to October 2014, we retrospectively identified 3 patients harboring a fusiform PCA aneurysm (P2 segment aneurysm) who underwent trapping of the aneurysm and reconstruction of the distal PCA through the same subtemporal approach. We analyzed immediate morbidity, surgical complications, and the patency of the bypass to determine the feasibility of this procedure. All 3 patients underwent successful trapping of the fusiform PCA aneurysm and revascularization of the distal PCA. The origin of P3 segment or posterior temporal artery (PTA) served as recipient arteries. In all 3 cases, adequate blood flow was evident after performing the STA-P3/PTA bypass. None of the patients experienced a new permanent neurological deficit. At 1-year follow-up, the STA-PTA/PCA bypasses remained patent. The STA-P3/PTA bypass through the subtemporal approach is a feasible option to maintain blood flow in cases of PCA fusiform aneurysms requiring trapping of the P2 segment.

Early Neurological Deterioration During Alteplase Infusion for Acute Ischemic Stroke

Recognizing new-territory ischemic stroke as an uncommon complication of intravenous thrombolysis is very important as it can lead to neurological deterioration during tissue-plasminogen-activator infusion. We report a case of an 80-year-old patient that has been treated with intravenous thrombolysis for right middle cerebral artery acute ischemic stroke. During infusion he had an abrupt neurological deterioration that proved to be a distal embolization of an asymptomatic non-occluding tip-of-the-basilar thrombus to the territory of left posterior cerebral artery that has been missed by the treating neurologist and radiologist in the pretreatment computed tomography angiography. In the thrombectomy that followed, only the right carotid artery has been catheterized and only the right middle cerebral artery was successfully recanalized, leaving the left posterior cerebral artery occlusion untreated. This case highlights that the use of thrombectomy in clinical practice provides an effective therapeutic option for large vessel occlusion in this setting. However, high clinical suspicion for this rare complication is mandatory to proceed to correct diagnosis and treatment.

Dissecting aneurysms of the distal segment of the posterior cerebral artery: clinical presentation and endovascular management

BackgroudWe aimed to evaluate the clinical presentations and report the acceptable clinical and angiographic outcome of the distal posterior cerebral artery (PCA) dissecting aneurysms with parent artery occlusion (PAO).MethodsFrom June 2006 to July 2013, 26 patients with PCA dissecting aneurysms were planned to be treated via endovascular PAO in our institution. Fourteen patients had ruptured aneurysms, and twelve patients had unruptured aneurysms. The endovascular modalities were the following: 1) PAO (n = 19), 2) palliative embolization (n = 5), and 3) proximal PAO (n = 2). Glasgow Outcome Scale (GOS) was used to assess the clinical outcome.ResultsThe procedure was technically successful in all cases. In the PAO and proximal PAO group, all of the immediate angiography showed occlusion of the parent vessel, and follow-up imaging showed no recurrence of the aneurysms. In the palliative embolization group, one of five patients was died of rebleeding after the procedure, and follow-up digital subtraction angiography (DSA) showed the other four aneurysms recurred. Five procedure related complications occurred totally: rebleeding (n = 1), hemiparesis (n = 2), and hemianopsia (n = 2).ConclusionDissecting aneurysms are dynamic lesions with variable and unpredictable evolution and a thorough treatment is warranted. Sacrificing the parent artery appears to be well tolerated for distal segment of PCA. We propose that this technique could be the first treatment option in treating dissecting aneurysms in this location. However, palliative occlusion of distal PCA dissecting aneurysms is not an advisable treatment option.

Sparing of the hippocampus indicates better collateral blood flow in acute posterior cerebral artery occlusion.

In acute posterior cerebral artery, occlusion involvement of the hippocampus is a common finding. Nevertheless, until today, infarction and ischemic lesion evolution in the hippocampus has not been studied systematically. Evaluation of hippocampal infarction patterns in posterior cerebral artery occlusion in the very early phase (≤six-hours) and ischemic lesion evolution on follow-up magnetic resonance imaging in relation to collateral blood flow assessed by a magnetic resonance imaging-based approach was conducted. In 28 patients [mean age 69·4 ± 13·8 years, 19 (67·9%) males, 10 (32·1%) females] with proximal posterior cerebral artery occlusion, magnetic resonance imaging findings were analyzed, with emphasis on hippocampal infarction patterns on diffusion-weighted images and collateralization on dynamic 4D angiograms derived from perfusion-weighted raw images. On initial diffusion-weighted images, we identified all known hippocampal infarction patterns: type 1 (complete) in 6/18 (33·3%) patients, type 2 (lateral) in 10/18 (55·6%) patients, and type 3 (dorsal) and type 4 (circumscribed) in 1/18 (5·6%) patient respectively. On dynamic 4D angiograms, the grade of collateralization was classified as 1 in 9 (32·1%), 2 in 1 (3·6%), 3 in 10 (35·7%), and 4 in 8 (28·6%) patients. On follow-up diffusion-weighted images, we found new ischemic lesions in three and infarction growth in the hippocampus in five patients. Patients with better collateralization (grades 3 and 4) less often had hippocampal infarctions on initial (P = 0·003)/follow-up diffusion-weighted images (P = 0·046) as well as type 1 on initial (P = 0·007)/follow-up diffusion-weighted images (P = 0·005). Involvement of the hippocampus in proximal posterior cerebral artery occlusion is frequently but not obligatorily observed and highly dependent on the extent of collateralization. The same holds true for hippocampal infarction patterns.

Supermoon-like Thrombus at the Mitral Valve: Struggle between the Bad and the Worse

Figure 1 Cerebral angiography showing acute cerebral infarction due to occlusion of the proximal posterior cerebral artery. An 81 year-old woman was referred to the echocardiography laboratory for evaluation of the cardioembolic source of cerebral infarction. Earlier, the patient was diagnosed with acute cerebral infarction due to occlusion of the proximal posterior cerebral artery (Figure 1), which was successfully treated with mechanical thrombectomy. Echocardiography revealed moderate mitral stenosis (MS) with a mitral valve area of 1.23 cm and a large ball-valve thrombus, which was freely floating within the enlarged left atrium. As blood flowed from the left atrium to the ventricle, this supermoon-like thrombus tried to pass through the mitral valve but failed repeatedly because of MS (Figure 2, Movie I-III in the online-only data supplement). Considering the risk of fatal embolisation, the thrombus was surgically removed and mitral valvuloplasty was performed. A large 4.3 x 2.8 cm round free-floating mass was removed from the left atrium (Figure 3). Histopathological examination showed the mass to be an organised thrombus. Thrombus formation and subsequent embolisation are not uncommon in MS. Sometimes, sudden cardiac death may occur owing to total obstruction of the mitral valve [1,2]. This patient, however, survived and was discharged uneventfully. This case was extremely unusual in that MS prevented

PROBABLE BILATERAL POSTERIOR CEREBRAL ARTERY DISSECTION

Isolated dissection of the posterior cerebral artery (PCA) is rare. A 68 year old male golf enthusiast developed moderately severe occipital headaches followed two weeks later by transient right sided weakness and speech disturbance. Six weeks later he developed difficulty reading and was found to have left upper quadrantanopia. Blood inflammatory and immunological markers were all normal as was CSF analysis. Initial CT brain showed a small, established left occipital lobe infarct. MR brain showed new right occipital, right thalamic and small left hippocampal infarcts. Transthoracic echocardiogram and arrhythmia recording identified no embolic source. CT and catheter angiography showed occlusion of the right PCA and stenosis of the left PCA. Other intracranial and extracranial vessels were normal. Conventional stroke secondary prevention strategies and steroid therapy was initiated due to initial concern of vasculitis. Follow up MR angiography showed no change in vessel status but interval right PCA infarct. We present the clinical features of this highly unusual case and discuss the radiological findings. In the absence of another identified cause and given the proximity to tentorium, we presume the cause is bilateral PCA dissection.

Cerebral Infarction due to Cardiogenic Emboli Originating from Atrial Myxoma: A Case Report

Cardiogenic embolism due to atrial myxoma is a rare cause of cerebral infarction. A 51-year-old woman presented to a hospital elsewhere with sudden onset of vision loss, loss of consciousness and subsequent circulatory collapse. Computed tomography and magnetic resonance imaging of brain revealed a rostral brainstem infarction, cerebral angiography showed evidence of occlusion of the left posterior cerebral artery, and echocardiographic examination revealed the presence of a mass in the left atrium. The patient received palliative care and was discharged. Four months later, she presented with muscle weakness in both legs and was unable to walk. Ultrasonography revealed atherosclerotic plaques in the left and right carotid arteries and multiple segmental emboli in the lower extremities. In addition, physical examination revealed bilateral blepharoptosis, poor pupillary reaction to light, deficient upward and downward eye movements and limited adduction. Anticoagulants and blood-lipid lowering drugs were administered. Auscultation of the precordium revealed systolic murmurs when the patient was in a sitting position. Echocardiographic examination and computed tomography of the chest disclosed a mass in the left atrium. The patient underwent surgical resection of the atrial mass. Histopathological examination of the resected tumor revealed a glandular cardiac myxoma. At four-month follow-up, there was some improvement in neurological symptoms. A cardiac origin of cerebral infarction should be suspected in middleaged patients who present with cardiac myxoma. Early surgical resection of the cardiac myxoma is important to prevent further embolic events.

A novel model of large vessel ischemic stroke in rabbits: microcatheter occlusion of the posterior cerebral artery

Background and purposeThe rabbit small clot embolic model for large vessel occlusion (LVO) is well established, yet has limitations. Blind introduction of autologous thrombus often fails to completely occlude a...

Reply to “Mechanisms of postoperative progression of steno-occlusive lesions in the posterior cerebral artery in moyamoya disease”

We thank Dr. Mugikura and his colleague for their comments on our paper “Posterior cerebral artery involvement in moyamoya disease: initial infarction and angle between PCA and basilar artery.” They have listed in detail three possible mechanisms that may bring about the progression of posterior cerebral artery (PCA) lesions in moyamoya disease (MMD): “primary progression” steno-occlusion of PCA, involution of PCA due to development of sufficient collaterals from the revascularization of anterior circulation, or occlusion of PCA due to presence of major infarctions. The latter two commonly hypothesize that the steno-occlusion of PCA is a secondary phenomenon of decrease in vascular demand from the PCA due to the reasons mentioned. We totally agree with their idea that the delayed progression of PCA is a primary phenomenon, related to the nature of the disease. As we mentioned in our paper, although the presence of preoperative infarction was strongly associated with progression of the PCA stenosis, this should not be interpreted as a causal relationship but as the concurrence of the two most influential factors affecting the prognosis of MMD. As our clinical experience with follow-up of MMD patients accumulate, we feel that many patients with PCA progression are “symptomatic” which means that the progression is not just the result of decreased demand of collaterals from the PCA but a real progression of ischemia of the PCA area. We agree that the second and the third mechanisms may accelerate the stenosis of PCAs. However, our indication for additional revascularization surgery of the PCA area requires presence and dominance of the first mechanism proposed in this commentary. Our paper focused on the clinical aspects, especially the preoperative factors related to delayed progression of PCA stenosis in MMD. The commentary by Dr. Mugikura and his colleague has greatly enriched the academic discussion on the topic of posterior circulation involvement in MMD.

Stent retriever for iatrogenic cerebral thromboembolism treatment

Thromboembolism is one of the dangerous complications of cerebrovascular endovascular surgeries, often resulting in severe disabilities. A clinical case of using stent retriever for treating iatrogenic cerebral thromboembolism occurred as a complication of diagnostic cerebral angiography is presented. Patient M., 49 years, was admitted in the department of neurology with referral diagnosis of subarachnoid hematoma. No pathologic changes of intracranial arteries were revealed on multi-spiral computed tomography, so cerebral angiography was administered. After administration of heparin (100 U/kg), selective cerebral angiography of all the intracranial vascular beds was performed using a diagnostic cerebral catheter with some technical difficulties. After the intervention was finished, the patient developed non-focal neurological symptoms, left-sided hemianopsia. Angiography of posterior circulation system was repeated immediately, left posterior cerebral artery occlusion was found. Stent retriever was used to restore the intracranial blood flow. An intracranial stent retriever Solitaire (EV3) was delivered to the occlusion and deployed with exposition of 5 minutes and further removal. Control angiography showed complete restoration of the intracranial blood flow without signs of distal embolism. The neurologic deficit had completely resolved during first 24 hours after the surgery. The presented clinical case illustrates the effect of stent retriever use to to restore the intracranial blood flow and stresses the need for such devices availability in departments performing cerebral surgeries in patients with cerebrovascular diseases.

Successful Thrombolysis despite Having an Incidental Unruptured Cerebral Aneurysm.

Purpose. To report a case of successful thrombolysis performed in a patient with an incidental unruptured intracranial aneurysm and review the literature. Case Report. Patient admitted for ischemic stroke due to left posterior cerebral artery occlusion, with an incidental right middle cerebral artery aneurysm, who underwent treatment with tissue plasminogen activator (rtPA) resulting in clinical improvement without complications. Conclusion. The presence of unruptured intracranial aneurysms is considered as a contraindication to thrombolysis, due to a potentially higher hemorrhagic risk of aneurysm rupture. Patients, otherwise, eligible for thrombolysis are usually excluded from receiving this emergent treatment, despite its potential benefits. A reevaluation of the strict exclusion criteria for thrombolysis in acute stroke patients should be considered.

Solitaire FR as a first-line device in acute intracerebral occlusion: A single-centre retrospective analysis

Analysing the clinical and angiographical effectiveness of the Solitaire FR as a mechanical thrombectomy device in acute intracerebral occlusion. Sixty-two patients were retrospectively included between January 2010 and March 2012. All of them underwent mechanical thrombectomy with the Solitaire FR device with or without intravenous thrombolysis. Twenty-five patients had an occlusion of the basilar artery, 1 had a posterior cerebral artery occlusion. There were 16 M1 middle cerebral artery occlusions, 9 carotid T occlusions and 11 tandem occlusions. Clinical status was evaluated using the National Institute of Health Stroke Scale (NIHSS) before and 24 hours after treatment and at discharge. The Modified Rankin Scale (mRS) was evaluated at 3 months. Mean age of patients was 64.8 years. Mean NIHSS score on admission was 19.8. Stand-alone thrombectomy was used in 47 patients (75.8%). Recanalization was successful (TICI score 2b or 3) in 23 of 26 (88.5%) patients with posterior circulation occlusion and in 23 of 36 (63.9%) patients with anterior circulation occlusion. NIHSS improved by more than 10 points for 15 of 59 patients with initial NIHSS over 10. MRS was 0-2 in 25 of 62 patients (40.3%). Overall, 23 patients out of 62 died (37%). No complications related to the Solitaire device occurred. These results confirm that the Solitaire FR device is safe and effective in stand-alone thrombectomy.

The Anterior Temporal Approach for Microsurgical Thromboembolectomy of an Acute Proximal Posterior Cerebral Artery Occlusion

In a short window of time, intravenous and intra-arterial thrombolysis is the first treatment option for patients with an acute ischemic stroke caused by the occlusion of one of the major brain vessels. Endovascular treatment techniques provide additional treatment options. In selected cases, high revascularization rates following microsurgical thromboembolectomy in the anterior circulation were reported. A technical note on successful thromboembolectomy of the proximal posterior cerebral artery has not yet been published. To describe the technique of microsurgical thromboembolectomy of an acute proximal posterior cerebral artery occlusion and the brainstem perforators via the anterior temporal approach. The authors present a technical report of a successful thromboembolectomy in the proximal posterior cerebral artery. The 64-year-old male patient had an acute partial P1 thromboembolic occlusion, with contraindications for intravenous recombinant tissue plasminogen activator. The patient underwent an urgent microsurgical thromboembolectomy after a frontotemporal craniotomy. The postoperative computerized tomography angiography showed complete recanalization of the P1 segment and its perforators, which were previously occluded. The early outcome after 1 month and 1 year follow-ups showed improvement from modified Rankin scale 4 to modified Rankin scale 1. Microsurgical thromboembolectomy can be an effective treatment option for proximal occlusion of the posterior cerebral artery in selected cases and experienced hands. Compared with endovascular treatment, direct visual control of brainstem perforators is possible.

Anatomical Variations in the Posterior Part of the Circle of Willis and Vascular Pathology in Bilateral Thalamic Infarction

Bilateral paramedian thalamic infarction is a rare subtype of stroke the etiology of which still remains undetermined in many patients. From a computed tomography (CT)/magnetic resonance imaging report database, we identified and analyzed 48 patients with bilateral paramedian thalamic infarction on diffusion-weighted imaging. Vascular pathologies were noted on CT angiography (CTA)/magnetic resonance angiography (MRA) and the P1 segments of the posterior cerebral artery (PCA) described as normal, hypoplastic, or absent. Vascular imaging revealed top of the basilar artery (BA) occlusion in 6 (12.5%), BA occlusion in 4 (8.3%), BA stenosis in 1 (2.1%), and BA hypoplasia in 3 (6.3%), PCA occlusion in 4 (8.3%), and PCA stenosis in 4 (8.3%) patients. In 18 (37.5%) patients, one or both P1 segments of the PCA were hypoplastic or absent. Patients with hypoplastic/absent P1 segments were more likely to have exclusively bilateral paramedian thalamic lesions (P < .001). An embolic source could be identified in 25 (55.6%) patients; there were no significant differences between both groups. Vascular imaging is useful to determine underlying vascular pathologies and may support the diagnosis of small vessel disease in those patients with isolated bilateral paramedian thalamic infarction, hypoplastic/absent P1 segment of the PCA, and lack of vascular pathology.

Rescue thrombolysis in the treatment of cardiac shock and acute stroke

The patients with ST-elevation myocardial infarction are primarily managed with percutaneous coronary intervention (PCI) or thrombolysis. It is well accepted that rescue PCI should be implemented in case of unsuccessful thrombolysis. However, the reverse, rescue thrombolysis, that is, administering of thrombolytic therapy in a patient in whom primary PCI fails, is not well defined. There are no available data about rescue thrombolysis so far. We represent a 43-year-old male patient with Buerger disease (thromboangiitis obliterans) who was admitted to our emergency department for cardiac shock related to inferior and right ventricular ST-elevation myocardial infarction. He was found to have occlusion of both right coronary artery and left anterior descending artery and managed with rescue thrombolysis. It was subsequently recognized that he had concurrent stroke caused by posterior cerebral artery (PCA) occlusion and improved with thrombolysis. It is reported for the first time that rescue thrombolysis has been put into practice and yielded great result after unsuccessful primary PCI.

Fluid-Attenuated Inversion Recovery Hyperintense Vessels in Posterior Cerebral Artery Infarction

Background: Fluid-attenuated inversion recovery hyperintense vessels (FHVs) are known to reflect stagnant or slow blood flow within the cerebral artery. FHVs are frequently observed in patients with acute cerebral infarction accompanied by arterial occlusion or significant stenosis of the anterior cerebral circulation. However, FHVs have not been studied in the context of posterior cerebral circulation. Thus, we investigated the prevalence of FHVs and its clinical significance in patients with acute posterior cerebral artery (PCA) territory infarction. Methods: In this retrospective study, consecutive patients with PCA territory infarction who underwent MRI within 1 week after symptom onset were enrolled. Two neurologists who were blinded to the angiographic findings read the images and determined the presence of FHVs. Afterwards, FHVs were graded according to the extent (subtle or prominent) and location (proximal or distal) of the hyperintense vessels. Neurologic deficits of the patients were assessed by the National Institutes of Health Stroke Scale (NIHSS) upon admission and after 5 days. The clinical outcome between patient groups based on FHVs grading was compared using the NIHSS. Among the patients with PCA occlusion, infarction volume on the diffusion-weighted image was compared between the two groups with and without distal FHVs. Results: FHVs were observed in 25 of the 87 patients (28.7%) with PCA territory infarction and in 65.7% of the 35 patients with significant arterial stenosis (10 patients) or occlusion (25 patients) in the posterior cerebral circulation. Among the 18 patients with PCA occlusion, the NIHSS score was significantly improved in patients with distal FHVs compared to the others (2.00 ± 2.18 vs. 0.56 ± 1.01, p = 0.04). The infarction volume was smaller in the distal FHV group than in the others (8.3 ± 8.7 vs. 16.8 ± 17.6 ml), but the difference was not statistically significant. Conclusions: FHVs are detected in patients with PCA territory infarction, especially in those with an occlusive lesion in the PCA. FHVs can be used as an imaging marker of PCA occlusion. Although this study showed a better clinical improvement in patients with distal FHVs, further study is needed to elucidate the clinical meaning of FHVs in PCA infarction.

妊娠14週で脳塞栓症を発症しrecombinant tissue plasminogen activator（rt-PA）静注療法を施行したプロテインS欠乏症の1例

When cerebral infarction develops during pregnancy, treatment without adverse effects must be considered not only for the mother but also for the fetus. Because pregnant women were excluded from many clinical trials, clear treatment guidance for them is not shown in the package inserts or guidelines of many drugs. We report the case of a 35-year-old woman (gravida 3, para 2) who developed sudden onset of left visual field defect, left hemiparesis, and dysesthesia over the left forearm during her fourth month of pregnancy. Brain diffusion-weighted MRI showed high intensity areas in the right occipital lobe, and magnetic resonance angiography revealed an occlusion of the right posterior cerebral artery. She was treated with an intravenous injection of recombinant tissue plasminogen activator 2 h 55 min after symptom onset, and the visual field and sensorimotor deficits improved. MRA obtained 3 days after the onset showed recanalization of the right posterior cerebral artery. We also conducted electrocardiography, neck vascular ultrasound, cardiovascular ultrasound, transcranial Doppler recordings from the temple area, and laboratory examinations for complete blood count, biochemistry, coagulation factors, endocrine secretion, and autoantibodies. Reduced protein S activity (35%) along with high intensity transient signals on transcranial Doppler indicated microemboli to be the embolic source. All other tests were negative. Anticoagulation therapy was initiated to prevent recurrence. She was initially given intravenous heparin, and then switched to warfarin therapy at 15 weeks of gestation. The patient delivered a healthy infant via caesarean section. Although reports and experiences of thrombolytic therapy with injection of recombinant tissue plasminogen activator during pregnancy remain scant, this therapy might be carefully used, especially after due consideration and understanding of the risks and benefits for both mother and fetus.

CT Density Changes with Rapid Onset Acute, Severe, Focal Cerebral Ischemia in Monkeys

Computerized tomography (CT) is the most often used imaging modality in the evaluation of acute clinical stroke. However, the rapidity with which CT density changes occur after acute, severe, focal ischemia cannot be determined clinically. Even if the time of symptom onset is known, clinical stroke severity is highly variable. We studied the time course of CT density change after severe, rapid onset, acute, focal ischemia as documented by stable xenon CT cerebral blood flow (CBF) in monkeys. Eight monkeys (Macaca mulatta) were subjected to transorbital occlusion of the left posterior cerebral, anterior, middle, and internal carotid arteries to induce focal ischemia. CT density Hounsfield units (HU), CBF by stable xenon CT, arterial blood pressure, and blood gases were measured before occlusion, immediately after occlusion, at 30min, and hourly for up to 6h. Occlusion of the cerebral arteries decreased CBF to 8 ± 5ml/100g/ min within 15min postocclusion. At 6h, CBF was unchanged at 9 ± 4ml/100g/ min. CT density within the ischemic core fell from 42 to 38HU immediately after occlusion (P < 0.05), rose transiently, then fell at 2h (P < 0.01) and plateaued at 36 ± 5HU for a total decrease of 4-5HU between 4 and 6h poststroke. Changes in CT density lag severe focal ischemia by 2h. Thus, when CT hypodensity is seen in acute stroke, it is likely 2h old. It also provides an explanation for the phenomenon of clinical CT mismatch with clinical deficits and normal CT.