[Short-term effectiveness of interlaminar lumbar instrumented fusion through a small incision for lumbar spinal stenosis].

OBJECTIVE: To evaluate the short-term effectiveness of local laminectomy and interlaminar lumbar instrumented fusion (ILIF) through a small incision for lumbar spinal stenosis. METHODS: Between November 2009 and January 2011, 16 patients with lumbar spinal stenosis were treated by local laminectomy and ILIF through a small incision. There were 7 males and 9 females with an average age of 52.8 years (range, 49-67 years). Sixteen patients had lumbar degenerative stenosis with an average disease duration of 4 years and 7 months (range, 2 years-9 years and 4 months). Four cases complicated by lateral recessus stenosis, 3 by lumbar disc herniation. Involved segments included L3,4 in 2 cases, L4,5 in 4 cases, L5, S1 in 4 cases, L3,4 and L4,5 (double segments) in 2 cases, L4,5 and L5, S1 (double segments) in 4 cases. The effectiveness was evaluated with the pre- and post-operative Visual Analogue Scale (VAS) scores, Oswestry Disability Index (ODI). The cross-sectional areas of spinal canal were measured by CT scanning and were compared between pre- and post-operation. RESULTS: The average operative time was 47 minutes (range, 35-80 minutes); the average blood loss was 145 mL (range, 120-350 mL); and the average hospitalization days were 7.8 days (range, 4-15 days). Cerebrospinal fluid leakage occurred in 1 case, and healing of incisions by first intention was achieved in the others. The patients were followed up 12-22 months (mean, 14.8 months). CT scanning showed interspinous fusion in 14 cases and possible fusion in 2 cases after operation, with an average fusion time of 4.6 months (range, 3-10 months). The postoperative VAS score, ODI, and cross-sectional area were significantly improved when compared with preoperative values (P < 0.05). CONCLUSION: The ILIF can promote fusion between spinous processes, provide spine stabilization, and protect the spinal cord. The procedure has small incision, simple method of fixation and fusion.

Postischemic reperfusion: ultrastructural blood-brain barrier and hemodynamic correlative changes in an awake model of transient forebrain ischemia.

OBJECTIVE: In nonrecovery models of cerebral ischemia, blood-brain barrier (BBB) and cerebral blood flow (CBF) changes are known to occur during reperfusion. It is unknown, however, whether those CBF and BBB alterations occur after brief, transient ischemia with neurological recovery. The purpose of this study was to characterize the time course of CBF and BBB ultrastructural changes during reperfusion in an awake, recovery model of transient global forebrain ischemia (GFI). METHODS: Forty-five adult Sprague-Dawley rats were subjected, while awake, to 10 minutes of GFI by the nine-vessel occlusion method. Thirty-five age-matched animals composed a sham-operated group. Normal control (n = 5), sham-operated (n = 5), and nine-vessel occlusion/reperfusion (n = 15) rats were selected for ultrastructural analysis. Electroencephalography was performed, and CBF, mean arterial blood pressure, and intracranial pressure were measured during ischemia and reperfusion up to 24 hours. Quantitative morphological analysis of cortical BBB capillaries was performed by transmission electron microscopy at the same time points at which specific CBF changes occurred during reperfusion. RESULTS: CBF decreased to 6% of preocclusion values during GFI. This correlated with coma and decerebrate rigidity. During reperfusion, short-lived hyperemia (225 +/- 18%, P < 0.001) was characterized by increased intracranial pressure (28.3 +/- 2.6 mm Hg, P < 0.001) and isoelectric electroencephalogram. This was followed by hypoperfusion, which reached a nadir of 59.7% (59.7 +/- 8.8%, P < 0.01) from baseline by 90 minutes. At this time point, the electroencephalogram recovered, and intracranial pressure and mean arterial blood pressure showed no abnormalities. By 8.5 hours, CBF returned to normal, and this coincided with complete recovery of the animal. Ultrastructural BBB analysis revealed astrocyte end-foot process edema and patent capillaries during hyperemia. Severe interstitial BBB edema and capillary lumen collapse was observed during hypoperfusion. Detachment and migration of pericytes was observed during hypoperfusion and beyond. CONCLUSION: A biphasic CBF response is elicited during reperfusion after brief nonlethal GFI under awake conditions.

Long-term neuroprotection induced by regional brain cooling with saline infusion into ischemic territory in rats: a behavioral analysis.

The neuroprotective effect of hypothermia has long been recognized. Our recent studies have demonstrated the significant therapeutic value of local brain cooling in the ischemic territory prior to reperfusion in stroke, with reduced infarction and inflammatory responses up to 48 hours of reperfusion. The goal of this study was to determine if local brain cooling, produced by infusion of cold saline, could induce long-term functional improvement after stroke. A hollow filament was used to block the middle cerebral artery (MCA) for 3 hours, and then to locally infuse the ischemic territory with 6 ml cold saline (20 degrees C) for 10 minutes prior to reperfusion. This brain cooling infusion induced a significant (p < 0.01) decrease in neurologic deficits and significantly (p < 0.01) improved motor behavior in ischemic rats after 14 days of reperfusion, compared with ischemic rats without local cold saline infusion. This improvement continued for up to 28 days after reperfusion. No significant difference in motor performance was observed between the brain cooling infusion and normal control groups. Significant (p < 0.01) reductions in infarct volume were also evident. In conclusion, a local cerebral hypothermia induced by local saline infusion prior to reperfusion produced a long-term functional recovery after ischemic stroke. A therapeutic procedure, which combines prereperfusion infusion into an ischemic region with coincident cerebral hypothermia and perhaps subsequent recanalization of an occluded intracranial vessel, may improve the outcome for stroke patients.

Local saline infusion into ischemic territory induces regional brain cooling and neuroprotection in rats with transient middle cerebral artery occlusion.

OBJECTIVE: The neuroprotective effect of hypothermia has long been recognized. Use of hypothermia for stroke therapy, which is currently being induced by whole-body surface cooling, has been limited primarily because of management problems and severe side effects (e.g., pneumonia). The goal of this study was to determine whether local infusion of saline into ischemic territory could induce regional brain cooling and neuroprotection. METHODS: A novel procedure was used to block the middle cerebral artery of rats for 3 hours with a hollow filament and locally infuse the middle cerebral artery-supplied territory with 6 ml cold saline (20 degrees C) for 10 minutes before reperfusion. RESULTS: The cold saline infusion rapidly and significantly reduced temperature in cerebral cortex from 37.2 +/- 0.1 to 33.4 +/- 0.4 degrees C and in striatum from 37.5 +/- 0.2 to 33.9 +/- 0.4 degrees C. The significant hypothermia remained for up to 60 minutes after reperfusion. Significant (P < 0.01) reductions in infarct volume (approximately 90%) were evident after 48 hours of reperfusion. In ischemic rats that received the same amount of cold saline systemically through a femoral artery, a mild hypothermia was induced only in the cerebral cortex (35.3 +/- 0.2 degrees C) and returned to normal within 5 minutes. No significant reductions in infarct volume were observed in this group or in the ischemic group with local warm saline infusion or without infusion. Furthermore, brain-cooling infusion significantly (P < 0.01) improved motor behavior in ischemic rats after 14 days of reperfusion. This improvement continued for up to 28 days after reperfusion. CONCLUSION: Local prereperfusion infusion effectively induced hypothermia and ameliorated brain injury from stroke. Clinically, this procedure could be used in acute stroke treatment, possibly in combination with intra-arterial thrombolysis or mechanical disruption of clot by means of a microcatheter.

Regional brain cooling induced by vascular saline infusion into ischemic territory reduces brain inflammation in stroke.

The neuroprotective effect of hypothermia has long been recognized. Use of hypothermia for stroke therapy, which is currently being induced by whole body surface cooling, has been largely limited because of management problems and severe side effects (i.e., pneumonia). Our recent studies have demonstrated the significant therapeutic value of local brain cooling in the ischemic territory prior to reperfusion in stroke. The goal of this study was to determine if cerebral local cooling infusion could reduce stroke-mediated brain injury by inhibiting inflammatory responses. A hollow filament was used to block the middle cerebral artery (MCA) for 3 hours, and then to locally infuse the ischemic territory with 6 ml cold saline (20 degrees C) for 10 min prior to 48-h reperfusion. This cold saline infusion significantly ( P<0.01) reduced temperature of the MCA supplied territory (in cerebral cortex from 37.2+/-0.1 degrees C to 33.4+/-0.4 degrees C, in striatum from 37.5+/-0.2 degrees C to 33.9+/-0.4 degrees C), with the hypothermia remaining for at least 45 min after reperfusion. Consequently, significant ( P<0.01) reductions in endothelial expression of intracellular adhesion molecule-1 (ICAM-1), the key step for inflammatory progress, as well as leukocyte infiltration, were evident in both cortex and striatum after reperfusion. As a control, ischemic rats received the same amount of cold saline systemically through a femoral artery. A mild hypothermia was induced in the cerebral cortex (35.3+/-0.2 degrees C) but not in the striatum (36.8+/-0.2 degrees C). The reduced cortical temperature returned to normal within 5 min. Brain temperature in ischemic rats perfused locally with saline at 37 degrees C remained normal. Intensive expression of ICAM-1 and accumulation of leukocytes was observed in ischemic control groups without brain cooling infusion. In conclusion, brain hypothermia induced by local pre-reperfusion infusion ameliorated brain inflammation from stroke.

Exercise-induced overexpression of angiogenic factors and reduction of ischemia/reperfusion injury in stroke.

The purpose of this study was to determine if exercise could induce expression of vascular endothelial growth factor (VEGF) and angiopoietin 1 and 2, in association with angiogenesis; and if angiogenic changes correlated with reduced brain injury in stroke. Adult male Sprague Dawley rats (3 month old, n=44) were exercised on a treadmill 30 minutes each day for 1, 3 or 6 weeks, or housed as non-exercised controls for 3 weeks. Some 3 week-exercised rats were then housed for an additional 3 weeks. Exercise significantly (p<0.01) increased mRNA (determined by real-time reverse transcriptase-polymerase chain reaction) expression of angiopoietin 1 and 2 as early as 1 week, with further increases occurring at 3 weeks. A mild increase after 1 week and a robust increase after 3 weeks of exercise in four isoforms (120, 144, 164, 188) of VEGF mRNA levels were significantly (p<0.01) observed, with VEGF(144) being more markedly up-regulated. Overexpression of the mRNAs decreased upon withdrawal of exercise. A significant increase (p<0.01) in the density of microvessels (determined by laminin-immunocytochemistry) was found at 3 weeks of exercise and this continued after exercise was withdrawn. In exercising rats subjected to 2-h MCA occlusion followed by 48-h reperfusion, neurological deficits and infarct volume were significantly reduced. Neuroprotection continued after 3 weeks of rest. This study indicates that pre-ischemic exercise reduces brain injury in stroke. The reduced damage is associated with angiogenesis, possibly induced by angiogenic factors following exercise. Physical exercise up-regulates mRNA levels of the angiopoietin family and VEGF.

Reduced inflammatory mediator expression by pre-reperfusion infusion into ischemic territory in rats: a real-time polymerase chain reaction analysis.

The aim in this study was to investigate if our new experimental model for stroke therapy, flushing the ischemic territory with saline prior to reperfusion, could reduce overexpression of inflammatory mediators during reperfusion. Stroke in Sprague-Dawley rats (n=24) was induced by a 2-h middle cerebral artery occlusion using a novel intraluminal hollow filament. Prior to reperfusion, 12 of the ischemic rats received 6 ml isotonic saline at 37 degrees C infused into the ischemic area through the filament. Expression of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) and intercellular adhesion molecule 1 (ICAM-1) mRNA was analyzed by real-time reverse transcriptase-polymerase chain reaction (real-time RT-PCR). A significant overexpression (9-26 fold) of the genes encoding TNF-alpha, IL-1beta and ICAM-1 in ischemic rats was found during early reperfusion without flushing at 6 and 12 h. This increase was significantly reduced at both 6 and 12 h post-reperfusion as a result of saline flushing.

Brain retraction injury.

This paper reviews the literature of the brain retraction injury during the last century. The review focused on the instrument characteristic as well as the physiopathological and histopathological damage of the brain induced by brain retraction. It was found that lesions were induced by cerebral ischemia. We conclude that a better monitoring system needs to be developed to avoid brain injury.

Free fatty acids in cerebrospinal fluids from patients with traumatic brain injury.

Free fatty acid (FFA) concentrations in cerebrospinal fluid (CSF) are recognized as markers of brain damage in animal studies. There is, however, relatively little information regarding FFA concentrations in human CSF in normal and pathological conditions. The present study examined FFA concentrations in CSF from 15 patients with traumatic brain injury (TBI) and compared the data with values obtained from 73 contemporary controls. Concentrations of specific FFAs from TBI patients, obtained within 48 h of the insult were significantly greater than those in the control group (arachidonic, docosahexaenoic and myristic, P<0.001; oleic, palmitic, P<0.01; linoleic, P<0.05). Higher concentrations of total polyunsaturated fatty acids (P<0.001) and of arachidonic, myristic and palmitic acids measured individually in CSF (P<0.01) obtained 1 week after the insult were associated with a worse outcome at the time of hospital discharge using the Glasgow Outcome Scale. This preliminary investigation suggests that CSF FFA concentrations may be useful as a predictive marker of outcome following TBI.

Advances in ICP monitoring techniques.

With the advent of newer devices for measuring intracranial pressure (ICP) and cerebral metabolism, more alternatives continue to rise aiming to control ICP. This manuscript presents a proposed analysis of different ICP monitoring devices in order to make appropriate selection of them in our clinical setting including general and pediatric applications. A systematic review of the literature was made analyzing the technical advances in ICP monitoring. The recent in vitro and in vivo tests as well as mathematical/computer models were reviewed. Practical applications of principles were discussed and compared based on the mode of pressure transformation. A ventricular catheter connected to an external strain gauge transducer or catheter tip pressure transducer device is considered to be the most accurate method of monitoring ICP and enables therapeutic CSF drainage. The significant infections or hemorrhage associated with ICP devices causing patients morbidity are clinically rare and should not deter the decision to monitor ICP. Parenchymal catheter tip pressure transducer devices are advantageous when ventricular ICP cannot be obtained or if there is an obstruction in the fluid couple, though they have the potential for significant measurement differences and drift due to the inability to recalibrate. Subarachnoid or subdural fluid-coupled devices and epidural ICP devices are currently less accurate. With an increasing miniaturization of the transducers, fiberoptic systems have been developed, however, there is a problem of measurement accuracy during the period of patient monitoring and external calibration should be performed frequently to ensure constant accuracy. Ventriculostomies continue to have a pivotal role in ICP control. With a rational understanding of the applications and limitations of the different ICP monitoring devices, the outcome for critically ill neurological patients is optimized.

Stereolithography: neurosurgical and medical implications.

We present material to define and understand the concept of Stereolithography (STL) and its potential benefits to the field of neurosurgery and other medical specialties. A historical and scientific review of the literature on stereolithography, its evolution and uses in neurosurgery, forensic medicine, and other medical specialties are described. Considerations regarding different techniques used to obtain STL are discussed. The reproduction of cranial and vascular structures using this technique is evaluated. Data acquisition and model fabrication are the two basic steps required for stereolithography to create custom models for multiple applications in cranio-facial surgery, vascular studies, orthopedic surgery, urology and forensic medicine, among others. Stereolithography is a relatively new technique which continues to grow in many medical fields. Pre-operative education of patients, better understanding of patient anatomy, and the creation of custom-made prostheses are proven benefits of this technique.

Synaptic plasticity in thalamic nuclei enhanced by motor skill training in rat with transient middle cerebral artery occlusion.

The goal of this study was to determine if synaptic plasticity in the thalamus of rats subjected to stroke could be altered by motor training. Transient occlusion of right middle cerebral artery in adult female Sprague-Dawley rats (n = 35) was induced with an intraluminal filament followed by three training conditions, 1. motor skill training on Rota-rod requiring balance and coordination skills, 2. simple exercise on treadmill, and 3. nontrained controls. Synaptic plasticity in brain was evaluated by synapotophysin immunocytochemistry at 14 or 28 days after training procedures. Infarct volume was determined in Nissl stained sections. Both at 14 and 28 days after Rota-rod training, intense synaptophysin immunoreactivity was present in the right but not the left mediodorsal and ventromedial nuclei of thalamus of ischemic rats. In treadmill-trained animals, however, similarly intense synaptic plasticity in these two thalamic nuclei was seen only at 28 days. Immunostaining was found also in other brain regions adjacent to or remote from infarct site. The data suggest that motor training, particularly motor skill training involving balance and coordination, facilitates a uniquely lateralized synaptogenesis in the thalamus.

Late outcome following central nervous system injury in child abuse.

OBJECTIVE: The object of this study was to increase our understanding of the social, clinical, radiographic and psychological consequences of child abuse after the initial insult and to describe the role of neurosurgery and other specialties in this context. METHODS: A review of the literature on child abuse (using scientific journals, textbooks, and internet reports) was conducted, with special attention given to child abuse in infants. The biomechanical patterns of injury, the long-term neurological, psychological, and social outcomes and methods of rehabilitation are reviewed. CONCLUSIONS: Head injury associated with physical abuse carries a significantly worse clinical outcome than accidental trauma. Late findings in CT scans and MRI show evidence of cerebral atrophy in 100% and cerebral ischemia in 50% of physical abuse cases. Abuse and neglect have a strong impact in developing children, producing emotional, cognitive, and social problems that may persist throughout the rest of their lives. Outcome cannot be improved without an integrated rehabilitation strategy encompassing early field management, hospital therapy, precise targeting of educational and cognitive needs, and finally return to the community. New ancillary tests have emerged that are aimed at improving rehabilitation and illuminating the long-term physiological and functional impact of abuse.

Paraclinoid Carotid Aneurysms: Surgical Management, Complications, and Outcome Based on a New Classification Scheme.

The site of origin, projection, and relationship of aneurysms arising from the ophthalmic segment of the internal carotid artery (ICA) to adjacent structures are heterogeneous. Based on a retrospective analysis of 61 patients with aneurysms in this location, we developed a simple numerical classification system to guide surgical planning. We used angiographic findings to categorize the aneurysms. We followed the nomenclature of the carotid segments by Bouthillier et al (Neurosurgery 1996;38:425-432), C4 being the intracavernous ICA, C5 the clinoidal segment, and C6 the ophthalmic segment of the ICA. The aneurysms were divided into four major types: Types Ia and Ib projected superiorly and arose from the dorsal surface of C6. Type Ia was related to the ophthalmic artery. Type Ib aneurysms were sessile and had no branch relations. Type II aneurysms were related to the ventral wall of the C6 segment without any branch relation. Type IIIa variant arose from medial wall of the C6 segment and was related to the superior hypophyseal artery. Type IIIb arose from the medial wall of the C5 segment below the dural reflection without any branch relation. Large type IV aneurysms arose from the C5 and C6 segments, widening the distal dural ring. Patients' postoperative status and visual and overall outcomes were analyzed. Ultimately, this classification helped us to plan operative approaches and clip selection.

Functional improvement after motor training is correlated with synaptic plasticity in rat thalamus.

The goals of this study were to determine whether functional outcome after motor training in rats was linked to synaptic plasticity in thalamus, and whether the Rota-rod apparatus, widely used to test motor function, could be used as an easy and quantitative motor skill training procedure. Adult female Sprague-Dawley rats (n = 39) were evaluated under three training conditions: 1. Movement requiring balance and coordination skills on Rota-rod; 2. simple exercise on treadmill; 3. nontrained controls. Motor function was evaluated by a series of motor tests (foot fault placing, parallel bar crossing, rope and ladder climbing) before and 14 or 28 days after training procedure. Synaptic strength in brain was assessed by synaptophysin immunocytochemistry. After 14 days of training, Rota-rod-trained animals significantly (p < 0.01) improved motor performance, compared to treadmill and nontrained animals. Animals with up to 28 days of simple exercises on the treadmill did not show a significantly improved performance on most motor tasks, except for an improvement in foot fault placing. Intensive synaptophysin immunoreactivity was present in the right but not the left mediodorsal and ventromedial nuclei of thalamus in Rota-rod-trained rats at 14 and 28 days, and in treadmill-trained rats at 28 days. The data suggested that functional outcome is effectively improved by motor skill training rather than by simple exercises, and this may be related, at least partially, to uniquely lateralized synaptogenesis in the thalamus. Both Rota-rod and treadmill could be quantitatively used in rats for motor training of different complexity.

Biomechanical properties of high-density polyethylene for pterional prosthesis.

The pterional approach is the most popular surgical technique in aneurysm and skull base tumor removal. Reconstruction of the temporal contour deformity due to craniotomy requires graft implantation. Porous high-density polyethylene (PHDPE) as a craniofacial and pterional implant material recently became available. However, material properties of the pterional implant are not yet known. In order to measure the biomechanical properties of PHDPE, we implemented the tensile test, the three-point bending test and the water displacement method for density measurement. Elastic modulus varies from 227 to 307MPa. Density range is 0.68 and 0.7 depending on the size of pores. The data can be used to study the character of the porous high-density polyethylene implant, how it resists stress or fatigue in combination with conventional plating systems.

Prereperfusion saline infusion into ischemic territory reduces inflammatory injury after transient middle cerebral artery occlusion in rats.

BACKGROUND AND PURPOSE: In ischemic stroke, the ischemic crisis activates a cascade of events that are potentiated by reperfusion, eventually leading to cell death. The chief aim in this study was to investigate whether our new experimental model for stroke therapy, flushing the ischemic territory with saline before reperfusion, could minimize this damage by (1) reducing the inflammatory reaction and (2) improving regional microcirculation. METHODS: Stroke in Sprague-Dawley rats (n=39) was induced by a 2-hour middle cerebral artery occlusion with the use of a novel intraluminal hollow filament. Before 48-hour reperfusion, 20 of the ischemic rats received 7 mL isotonic saline at 23 degrees C or 37 degrees C infused into the ischemic area through the filament. Regional cerebral blood flow in cortex supplied by the right middle cerebral artery was measured by laser-Doppler flowmetry during ischemia and reperfusion. Leukocyte infiltration, microvascular plugging, and infarct volume were compared with the use of hematoxylin and eosin staining. Expression of intercellular adhesion molecule 1 (ICAM-1) was determined by immunocytochemistry. Neurological deficits were evaluated. RESULTS: After the prereperfusion infusion of saline, significantly (P<0.001) improved cerebral blood flow (105+/-12% of baseline) was obtained up to 48 hours after reperfusion, compared with 45+/-7% at 24 hours and 25+/-3% at 48 hours after reperfusion without local saline infusion. Significant (P<0.001) reductions in leukocyte infiltration (61%), vascular plugging (45%), infarct volume (approximately 65%), and neurological deficits were also produced. ICAM-1 expression in the infarct region was significantly (P<0.05) minimized by 37%. CONCLUSIONS: The reduced brain infarct and neurological deficits may be attributed to adequate reperfusion and ameliorated inflammation induced by local prereperfusion infusion.

Free fatty acids in human cerebrospinal fluid following subarachnoid hemorrhage and their potential role in vasospasm: a preliminary observation.

OBJECT: The mechanisms leading to vasospasm following subarachnoid hemorrhage (SAH) remain unclear. Accumulation in cerebrospinal fluid (CSF) of free fatty acids (FFAs) may play a role in the development of vasospasm; however, in no previous study have concentrations of FFAs in CSF been examined after SAH. METHODS: We collected samples of CSF from 20 patients with SAH (18 cases of aneurysmal SAH and two cases of spontaneous cryptogenic SAH) and used a high-performance liquid chromatography assay to determine the FFA concentrations in these samples. We then compared these findings with FFA concentrations in the CSF of control patients. All FFA concentrations measured 24 hours after SAH were significantly greater than control concentrations (p < 0.01 for palmitic acid and < 0.001 for all other FFAs). All measured FFAs remained elevated for the first 48 hours after SAH (p < 0.05 for linoleic acid, p < 0.01 for palmitic acid, and p < 0.001 for the other FFAs). After 7 days, a second elevation in all FFAs was observed (p < 0.05 for linoleic acid, p < 0.01 for palmitic acid, and p < 0.001 for the other FFAs). Samples of CSF collected within 48 hours after SAH from patients in whom angiography and clinical examination confirmed the development of vasospasm after SAH were found to have significantly higher concentrations of arachidonic, linoleic, and palmitic acids than samples collected from patients in whom vasospasm did not develop (p < 0.05). CONCLUSIONS: Following SAH, all FFAs are initially elevated. A secondary elevation occurs between 8 and 10 days after SAH. This study provides preliminary evidence of FFA elevation following SAH and of a potential role for FFAs in SAH-induced vasospasm. A prospective study is warranted to determine if CSF concentrations of FFAs are predictive of vasospasm.

Future of extracranial-intracranial bypass.

Total occlusion of internal carotid artery in the cervical region is an end result of progressive occlusive vascular disease. A small proportion of these patients will have symptoms of cerebral ischemia due to cerebral hypoperfusion in a delayed fashion. Identification of those individuals who are at risk of developing symptoms and prophylactically treating with a revascularization procedure will prevent such catastrophic events. With the co-operative study for bypass not supporting the bypass procedure and trial being questioned for its design and conclusions, a new trial of extracranial-intracranial bypass, The Carotid Occlusion Surgery Study, using the currently available technology will be undertaken to verify that the bypass will decrease the future stroke rate by at least 40% in patients with total carotid occlusion. A subset of patients with skull base pathology including tumors and aneurysms who may have to undergo carotid sacrifice as part of the surgical procedure are at risk of peri-operative and delayed stroke. Identification of these patients at risk by pre-operative tests may allow performance of extracranial-intracranial bypass prior to undertaking complex skull base procedures. The new imaging technology will guide management of these patients at risk and help identify patients who may need a bypass procedure.