bluuebunny/crossref_metadata_2025_split huggingface dataset:
CBF and time thresholds for the formation of ischemic cerebral edema, and effect of reperfusion in baboons
Authors: Bell B. A. , Symon Lindsay , Branston Neil M. 
Published: May 2009

✓ Ischemic cerebral edema has been studied in 41 baboons, with regional cerebral blood flow (CBF) determined by hydrogen clearance, and edema measured by microgravimetry. A threshold of ischemia has been identified for baboon cortex and subcortical white matter, which has to be crossed before edema formation begins. This threshold is 40.5% of normal CBF in cortex, and 34.4% of normal flow in subcortical white matter. A time threshold has also been determined, and the baboon brain can withstand 30 minutes of ischemia of the middle cerebral artery without significant edema formation. Reperfusion of ischemic brain has no effect on tissue water if the ischemic flow and time thresholds have not been crossed. Reperfusion of cortex, where water has begun to accumulate, exacerbates the water accumulation in proportion to the extent of the reperfusion.
If these results are applicable to man, restoration of flow should not be attempted after an ischemic insult that reduces flow to less than 40% of normal unless it can be accomplished within 30 minutes of the insult. Provided CBF can be restored to above the 40% threshold within 30 minutes, reversal of the neurological deficit and prevention of ischemic edema can be expected.
Cerebrovascular reactivity in patients with ruptured intracranial aneurysms
Authors: Voldby Bo , Enevoldsen Erna M. , Jensen Finn T. 
Published: May 2009

✓ The cerebral vasomotor reactivity to arterial hypotension and hypocapnia was studied in 34 patients between the 3rd and 13th day after rupture of an intracranial saccular aneurysm. Using the intra-arterial xenon-133 injection method, regional cerebral blood flow (rCBF) and cerebral metabolic rate of oxygen (CMRO2) were measured. The intraventricular pressure and cerebrospinal fluid (CSF) lactate and pH levels were determined. The degree of vasospasm was measured on angiograms taken immediately following the rCBF study. The patients were graded clinically according to the system of Hunt and Hess.
Cerebral autoregulation was intact in patients in good clinical condition, but was impaired in patients in poor clinical condition. There was a close correlation between the degree of vasospasm and the degree of autoregulatory impairment, which varied from focal disturbances to global impairment. Intracranial hypertension and CSF lactic acidosis were commonly found in association with vasoparalysis. Cerebrovascular response to hyperventilation was generally preserved, although often reduced. During hyperventilation, the cerebral perfusion pressure became elevated, and increases in CMRO2 were often found, even in patients with severe diffuse spasm and cerebral ischemia. The clinical significance of the results in relation to the treatment of delayed cerebral ischemia and to the use of intraoperative induced hypotension is discussed.
Inhibition of primate spinothalamic tract cells by TENS
Authors: Lee Kyu Ho , Chung Jin Mo , Willis William D. 
Published: May 2009

✓ Transcutaneous electrical nerve stimulation (TENS) was applied in an experimental animal model to investigate the underlying mechanisms of this treatment. Recordings were made from identified spinothalamic tract (STT) neurons in the lumbosacral spinal cords of seven anesthetized monkeys. The STT cells were activated by stimulating the common peroneal nerve at a suprathreshold intensity for C-fibers. Evoked responses of C-fibers were compared before, during, and after application of TENS for 5 minutes from a commercially available TENS unit. The current delivered by the TENS unit was monitored.
In 14 STT cells, some degree of inhibition of C-fiber evoked responses occurred only when the intensity of TENS exceeded the threshold of Aδ fibers. At a given stimulus intensity, bursts of pulses repeated at a low rate were more effective than high-rate pulses. When TENS was applied to an area of the skin within a cell's receptive field, it was more effective than when it was applied outside the receptive field. The C-fiber volley recorded from a peripheral nerve was not reduced in size, and there were no substantial changes in its latency due to TENS. The inhibition of the activity of STT cells was not altered appreciably after intravenous injection of naloxone hydrochloride.
These results suggest that TENS produces central nervous system inhibition by activating Aδ afferent fibers. The inhibitory effects of TENS on STT cells appear to be due to a mechanism that does not involve release of endogenous opioid substances.
Stable xenon CT blood flow mapping for evaluation of patients with extracranial-intracranial bypass surgery
Authors: Yonas Howard , Gur David , Good Barbara C. , Latchaw Richard E. , Wolfson Sidney K. , Good Walter F. , Maitz Glenn S. , Colsher James G. , Barnes J. Edward , Colliander Kristine G. , Teeter Bruce C. 
Published: May 2009

✓ Xenon computerized tomography (Xe CT) blood flow studies were conducted in 25 patients referred for a possible extracranial-intracranial bypass procedure for occlusive vascular disease in one or more extra- or intracranial vessels. These studies were helpful in selecting eight candidates for surgery. The Xe CT studies were performed at one or two brain levels using a prototype Xe CT system for measurement of cerebral blood flow which was designed in collaboration with the General Electric Co., and adapted for the GE 9800 scanner. In those patients selected to undergo operation, Xe CT demonstrated compromise of flow reserve regionally, globally, and/or in the watershed area. All eight patients who underwent the procedure showed a favorable clinical response postoperatively, and seven had a dramatic increase in flow. The 17 patients whose baseline CT studies showed no reduction of flow with the Xe CT method were not selected for surgery. All 25 patients have remained neurologically stable to date. Case studies of three of the eight patients undergoing bypass surgery are presented.
This limited but consistent experience suggests that Xe CT blood flow mapping makes possible the recognition of brain regions in which flow reserves are compromised. This is due to the relatively high degree of spatial resolution that this technique provides and to the fact that mapping can be correlated directly with the anatomy. Used in combination with a careful clinical examination and an accurate medical history, this study method appears to be a useful guide in the selection of patients who are most at risk from hemodynamic instability and those who are most likely to benefit from flow-augmentation surgery.
Zygomatic approach for lesions in the interpeduncular cistern
Authors: Fujitsu Kazuhiko , Kuwabara Takeo 
Published: May 2009

✓ Lesions in the interpeduncular cistern include basilar tip aneurysms, craniopharyngiomas, and chordomas. The surgical approach to these lesions presents a special technical problem, particularly when they are located high in the interpeduncular fossa. For the purpose of minimizing brain retraction and achieving excellent exposure within the interpeduncular cistern, the authors have developed a new surgical technique which involves detachment of the zygomatic arch.
The patient is placed in the supine position with the head rotated 45° to the contralateral side and tilted down 30° so that the surgeon can see into the interpeduncular cistern obliquely from below. The zygomatic arch of the temporal bone as well as a portion of the lateral orbital rim (the posterior ridge of the frontal process of the zygomatic bone) is removed to expose the anterior temporal base. With posterior retraction of the temporal lobe, the arachnoid membranes covering the Sylvian stem are opened in a retrograde fashion until the tentorial edge is sufficiently exposed. The posterior communicating artery and the optic tract are elevated to enter the interpeduncular cistern, after which the oculomotor nerve is dissected free of its surrounding arachnoid membranes and displaced posteroinferiorly.
Two patients with basilar tip aneurysms were operated on with this zygomatic approach, and a subtemporal modification of the zygomatic approach was used to treat a craniopharyngioma and a chordoma in two other patients. The procedure is described and a short description of its clinical use is given.
Role of monoamines in experimental spinal cord injury in rats
Authors: Kurihara Masaki 
Published: May 2009

✓ A spinal cord injury was produced in Wistar rats by extradural compression of the cord with a Sugita aneurysm clip for 5 seconds. During a 2-week observation period following the injury, the tissue norepinephrine (NE), dopamine (DA), and serotonin (5-HT) concentrations decreased uniformly at and below the injured site. The chemical denervation of NE or 5-HT neurons produced by the intraspinal injection of 6-hydroxydopamine (6-OHDA) or 5,7-dihydroxytryptamine (5,7-DHT) 2 weeks before the injury did not cause a marked difference in the extent of hemorrhagic necrosis of the spinal cord after trauma as compared to control animals without pretreatment. In the rats pretreated with 6-OHDA, NE was decreased to less than 30% of control (non-pretreated) values, and, beginning at 5 days after injury, motor performance (assessed quantitatively with the inclined-plane method) was significantly improved compared to results in the non-pretreated control rats. The rats pretreated with 5,7-DHT showed no change from control animals. Spinal cord samples from non-pretreated control animals obtained at the injury site 30 minutes after the compression injury showed a marked decrease in the activity of synaptosomal Na+-K+-ATPase (adenosine triphosphatase) of about 50%, and an increase in both thiobarbituric acid reaction substance (about 170%) and cyclic guanine monophosphate (about 150%). The NE-denervated rats showed no significant changes in these three parameters.
The results indicated that NE released after crush injury may impair the neuronal cell membrane around the lesion site by induction of lipid peroxidation. The possible mechanisms by which released NE may alter membrane function are discussed.
Extracranial-intracranial arterial bypass for middle cerebral artery stenosis and occlusion
Authors: Andrews Brian T. , Chater Norman L. , Weinstein Philip R. 
Published: May 2009

✓ Forty-seven patients with middle cerebral artery (MCA) stenosis and 18 patients with MCA occlusion underwent extracranial-intracranial arterial bypass procedures. Patients presented with a history of transient ischemic attacks (TIA's), reversible ischemic neurological deficits, TIA's after initial stroke, stroke-in-evolution, or completed stroke. Angiography revealed that the MCA stenosis ranged from 70% to over 95%. Two patients (4.3%) in the stenosis group had a perioperative stroke (within 30 days of operation). There was no perioperative mortality. In the occlusion group, no patient had a perioperative stroke, and one patient (5.5%) died from a non-neurological disease. The TIA's resolved completely in 90% of the patients with stenosis and in 91.6% of those with occlusion. No patient with MCA stenosis had a late ipsilateral stroke, although five had a contralateral or vertebrobasilar stroke. One patient with MCA occlusion had a late ipsilateral stroke. The bypass patency rate at late follow-up review was 100%.
The results of intracranial-extracranial arterial bypass procedures appear to be similar for patients with either stenosis or occlusion of the MCA. Symptomatic relief of TIA's was excellent and, in two patients with progressive stroke-in-evolution, the deficit was stabilized. The incidence of postoperative ipsilateral stroke was low in patients with TIA's alone or with TIA's after an initial stroke, but among patients with completed stroke, improvement was confined to slight reduction in the neurological deficit.
Indomethacin-mediated improvement following middle cerebral artery occlusion in cats
Authors: Dempsey Robert J. , Roy Mark W. , Meyer Kathleen L. , Donaldson David L. 
Published: May 2009

✓ Focal cerebral ischemia initiates multiple detrimental effects in the brain. Chief among these are the regional development of ischemic edema, decreased local perfusion, altered neuronal function, and eventual infarction. To determine if pretreatment with the cyclo-oxygenase inhibitor, indomethacin, would result in improvement in these parameters, adult cats were given indomethacin or control solvent (4 mg/kg intraperitoneally twice daily) and were studied for periods up to 24 hours after right middle cerebral artery occlusion. The interaction of anesthetic agents with indomethacin was also examined in separate groups of experimental animals using pentobarbital and ketamine. In cats allowed to recover from pentobarbital anesthesia, indomethacin reduced gray and white matter edema at 6 and 24 hours after occlusion (p < 0.05). This was noted in densely ischemic areas (indomethacin = 84.3%, control = 87.5%), in “penumbra” regions (indomethacin = 82.5%, control = 85.3%), and in nonischemic zones (indomethacin = 81.5%, control = 82.3%) at 24 hours. Somatosensory evoked potential amplitude and central latency were also improved in the indomethacin group (p < 0.05), as was cerebral perfusion (p < 0.05). In animals anesthetized with continuous ketamine administration, cerebral edema and perfusion as well as evoked potentials were not significantly improved in any region by indomethacin. Regional cerebral blood flow in the group was increased by indomethacin in the nonischemic opposite hemisphere (indomethacin = 64.7 cc/100 gm/min, control = 48.5 cc/100 gm/min, p < 0.05), but not in the penumbra region of the ischemic hemisphere (indomethacin = 15.0 cc/100 gm/min, control = 18.6 cc/100 gm/min, p < 0.05), when measured 4 hours after occlusion. This suggested a steal phenomenon.
Beneficial effects of indomethacin were evident in the presence of pentobarbital, but not after ketamine anesthesia. This suggests a synergism dependent on decreased arachidonic acid production from pentobarbitalstabilized membranes coupled with diminished production of cyclic endoperoxides from available arachidonate due to inhibition of cyclo-oxygenase with indomethacin.
Cerebral revascularization to a main limb of the middle cerebral artery in the Sylvian fissure
Authors: Diaz Fernando G. , Umansky Felix , Mehta Bharat , Montoya Salvador , Dujovny Manuel , Ausman James I. , Cabezudo Jose 
Published: May 2009

✓ Thirteen patients underwent an anastomosis of the superficial temporal artery (STA) or a saphenous vein graft to one of the secondary trunks of the middle cerebral artery (MCA). They included five patients with giant MCA trifurcation aneurysms, four patients in whom an earlier conventional STA-MCA anastomosis had become occluded, two patients who had stenosis of one of the secondary limbs of the MCA, and one patient who had a carotid-cavernous fistula. One patient had a saphenous vein graft from the common carotid artery to a secondary trunk of the MCA to bypass an occluded internal carotid artery and severely stenosed external carotid artery. The primary advantages of this procedure are that a large-caliber anastomosis to one of the secondary limbs of the MCA immediately restores flow into the MCA tree with a larger amount of vessel filling than with a standard cortical bypass, and large vessels can be used for the anastomosis. The disadvantages are that one of the secondary branches of the MCA must be occluded, the cerebral hemisphere around the Sylvian fissure must be retracted, a lumbar subarachnoid drain is needed, and the anastomosis must be performed deep within the Sylvian fissure.
The procedure is a satisfactory alternative in cases in which a conventional STA-MCA anastomosis has either failed or would be less likely to succeed.
Effect of the skull and dura on neural axis pressure-volume relationships and CSF hydrodynamics
Authors: Shapiro Kenneth , Fried Arno , Takei Futoshi , Kohn Ira 
Published: May 2009

✓ The pressure-volume index (PVI) technique of bolus manipulation of cerebrospinal fluid (CSF) was used to measure changes of neural axis volume buffering-capacity and CSF dynamics produced by different conditions of the skull and dura. Twenty-eight cats were studied in the intact state, after bilateral craniectomy, and with the dura opened. At each stage of altering the container of the brain, the following parameters were obtained: steady-state intracranial pressure (ICP), sagittal sinus venous pressure, PVI, and the resistance to the absorption of CSF. The resistance to absorption of CSF was determined using both the bolus injection and the continuous infusion of fluid.
After craniectomy, PVI increased from 0.76 ± 0.04 to 1.3 ± 0.07 ml (± standard error of the mean) (p < 0.001) and increased further to 3.6 ± 0.17 ml (p < 0.001) after opening the dura. The resistance to absorption of CSF (Ro), determined by bolus injection, decreased after craniectomy from 91.3 ± 7.5 to 56.3 ± 6.2 mm Hg/ml/min (p < 0.001) and decreased further to 8.9 ± 0.66 mm Hg/ml/min (p < 0.001) after opening the dura. Although resistance determined by constant infusion was similar, results were dependent on the rate of infusion. Despite these changes of resistance and PVI, steady-state ICP and sagittal sinus venous pressure were similar in all three conditions of the skull and dura. These studies indicate that changes of the container of the brain affect pressure-volume relationships within the neural axis. However, the changes of resistance to absorption of CSF are in a direction that preserves a steady-state hydrodynamic equilibrium.
Intracranial germ-cell tumors: natural history and pathogenesis
Authors: Jennings Mark T. , Gelman Rebecca , Hochberg Fred 
Published: May 2009

✓ The natural history of primary intracranial germ-cell tumors (GCT's) is defined from 389 previously published cases, of which 65% were germinomas, 18% teratomas, 5% embryonal carcinomas, 7% endodermal sinus tumors, and 5% choriocarcinomas. Intracranial GCT's display specificity in site of origin. Ninety-five percent arise along the midline from the suprasellar cistern (37%) to the pineal gland (48%), and an additional 6% involve both sites. The majority of germinomas (57%) arise in the suprasellar cistern, while most nongerminomatous GCT's (68%) preferentially involve the pineal gland (p < 0.0001). The age distribution of afflicted patients is unimodal, centering with an abrupt surge in frequency in the early pubertal years; 68% of patients are diagnosed between 10 and 21 years of age. Nongerminomatous GCT's demonstrate an earlier age of onset than do germinomas (p < 0.0001). Prolonged symptomatic intervals prior to diagnosis are common in germinomas (p = 0.0007), in suprasellar GCT's (p = 0.001), and among females (p = 0.02). Parasellar germinomas commonly present with diabetes insipidus, visual field defects, and hypothalamic-pituitary failure. Nongerminomatous GCT's present as posterior third ventricular masses with hydrocephalus and midbrain compression. Germ-cell tumors may infiltrate the hypothalamus (11%), or disseminate to involve the third ventricle (22%) and spinal cord (10%). Among a subpopulation of 263 conventionally treated patients, two factors were of prognostic significance: 1) histological diagnosis; germinomas were associated with significantly longer survival than nongerminomatous GCT's (p < 0.0001); and 2) staging of the extent of disease; this emphasizes the ominous character of involvement of the hypothalamus (p = 0.0002), third ventricle (p = 0.02), or spinal cord (p = 0.01). Specific recommendations regarding the necessity of histological diagnosis and staging of the extent of disease are made in light of modern chemotherapeutic advances.
The pathogenesis of GCT's may be revealed by their specificity of origin within the positive (suprasellar cistern-suprachiasmatic nucleus) and negative (pineal) regulatory centers for gonadotropin secretion within the diencephalon. The abrupt rise in age distribution at 10 to 12 years suggests that the neuroendocrine events of puberty are an “activating” influence in the malignant expression of these embryonal tumors.
A Phase I trial of naloxone treatment in acute spinal cord injury
Authors: Flamm Eugene S. , Young Wise , Collins William F. , Piepmeier Joseph , Clifton Guy L. , Fischer Boguslav 
Published: May 2009

✓ Results of a Phase I trial of the opiate antagonist naloxone for treatment of patients with acute spinal cord injury are reported. Naloxone was administered in doses ranging from 5 to 200 mg/sq m (0.14 to 5.4 mg/kg) for up to 48 hours. The patients ranged in age from 16 to 79 years (mean 37 years). Twenty patients received naloxone as a loading dose of 5 to 50 mg/sq m (0.14 to 1.43 mg/kg), followed by a maintenance dose of 20% of the loading dose given as a continuous infusion hourly for 47 hours (Group 1). Nine patients received a loading dose of 100 to 200 mg/sq m (2.7 to 5.4 mg/kg) and a maintenance dose of 75% of the initial dose hourly for 23 hours (Group 2). These higher doses (2.7 to 5.4 mg/kg) have been found to be effective in experimental spinal cord injury. Neurological examinations were performed and somatosensory evoked potentials (SEP's) were obtained as soon after admission as possible and again 1, 2, 3, and 7 days, 3 weeks, and 6 weeks to 6 months after admission.
The 20 Group 1 patients who received 1.43 mg/kg or less of naloxone showed no improvement in neurological status or SEP's. All but three (15%) of these patients had a complete neurological deficit at the time of admission. Treatment was begun an average of 12.9 hours after injury. Among the nine Group 2 patients treated with 2.7 mg/kg or more, there were five patients (56%) with incomplete deficits. This group received naloxone an average of 6.6 hours after admission. Two of the five Group 2 patients with incomplete lesions showed improvement in their neurological condition and/or SEP's within 36 hours of receiving the drug. One of the four Group 2 patients with a complete lesion at the time of admission was able to localize pressure sensation in his legs 36 hours after completion of the drug infusion. Four Group 2 patients (two with complete and two with incomplete lesions) have shown improvement in their SEP's, suggesting recovery of SEP's in a dose-related fashion. Four patients experienced increased pain after administration of the loading dose and during the maintenance infusion; in only one patient was this severe enough to require discontinuation of the drug. Of the 29 patients treated with naloxone, four died within 6 weeks of admission, for a mortality rate of 13.8%.
This study demonstrates that, in spinal cord-injured patients, naloxone given as an intravenous loading dose of 200 mg/sq m, followed by a continuous infusion of up to 150 mg/sq m/hr for 23 hours, has minimal side effects. The observed improvement in the clinical examination and SEP's at the higher doses, while not statistically verified in this Phase I trial, is encouraging.