Effect of coat protein mutations in bacteriophage fd studied by sedimentation analysis

(a) Bacteriophage fd is a filamentous virus that has previously been well characterized. (b) Earlier work using point mutagenesis indicated that a lysine residue at position 48 in the major coat protein plays a crucial role in interacting with the DNA and governing the assembly into an intact virion. (c) In this study the sedimentation properties (sedimentation velocity and equilibrium) of wild-type fd and two mutants substituted at lysine-48 (K48Q and K48A) were compared. (d) Both mutants are similar to each other [M(r) approximately (19.5 +/- 1.5) x 10(6)] but somewhat bigger than the wild-type [M(r) approximately (15.1 +/- 1.5) x 10(6)]. The value for the wild-type is consistent with earlier published values. (e) By combining these data with sedimentation coefficient data, it is possible to compare the contour lengths and relative flexibilities of the mutants with those of the wild-type virion. (f) The mutants are shown hydrodynamically to have larger contour lengths (as also observed by electron microscopy): the approximately 20% difference in values obtained assuming rigid particle hydrodynamics with those obtained from electron microscopy is strongly suggestive of some difference in flexibility between the wild-type and mutants.

Spinal cord changes after the evacuation of a spinal subdural haematoma

Spinal subdural haematoma is a rare entity. Only a few cases have been reported, mainly in patients with coagulopathies or bleeding diathesis, and also in patients undergoing anticoagulant therapy following surgery, trauma, or lumbar puncture. Symptoms of spinal cord compression produced by spinal subdural haematoma may progress rapidly causing complete and irreversible deficits. However, rapid diagnosis and surgical intervention can result in a good functional outcome for the patient. We report on a 41-year-old woman with a normal coagulation profile who developed a spinal subdural haematoma after a minor motor vehicle accident. Although initially asymptomatic, she developed a dense quadriparesis over a 36-h period. A magnetic resonance imaging study demonstrated a subdural mass compressing the spinal cord, and at surgery a spinal subdural haematoma was found. She was discharged to an inpatient rehabilitation facility. Follow-up at 1 year showed significant improvement in motor function, but absence of posterior column function. A follow-up magnetic resonance study demonstrated widening of the spinal cord, advanced myelomalacia and a large, central, multi-loculated syrinx.

Exercise pre-conditioning reduces brain damage in ischemic rats that may be associated with regional angiogenesis and cellular overexpression of neurotrophin

There is increasing evidence that physical activity is associated with a decreased stroke risk. The purpose of this study was to determine if exercise could also reduce brain damage in rats subjected to transient middle cerebral artery (MCA) occlusion, and if the reduced brain injury is associated with angiogenesis as well as cellular expression of the nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in regions supplied by the MCA. Adult male Sprague Dawley rats (n=36) exercised 30 min each day for 3 weeks on a treadmill on which repetitive locomotor movement was required. Then, stroke was induced by a 2-h MCA occlusion using an intraluminal filament, followed by 48 h of reperfusion. In addition to the two exercised groups of animals with or without MCA occlusion, there were two other groups of animals, with or without MCA occlusion, housed for the same duration and used as non-exercised controls. Brain damage in ischemic rats was evaluated by neurologic deficits and infarct volume. Exercise preconditioned and non-exercised brains were processed for immunocytochemistry to quantify the number of microvessels or NGF- and BDNF-labeled cells. Pre-ischemic motor activity significantly (P<0.01) reduced neurologic deficits and infarct volume in the frontoparietal cortex and dorsolateral striatum. Cellular expressions of NGF and BDNF were significantly (P<0.01) increased in cortex (neuron) and striatum (glia) of rats under the exercise condition. Significant (P<0.01) increases in microvessel density were found in striatum. Physical activity reduced stroke damage. The reduced brain damage may be attributable to angiogenesis and neurotrophin overexpression in brain regions supplied by the MCA following exercise.

Motor balance and coordination training enhances functional outcome in rat with transient middle cerebral artery occlusion

The goal of this study was to determine if relatively complex motor training on Rota-rod involving balance and coordination plays an essential role in improving motor function in ischemic rats, as compared with simple locomotor exercise on treadmill. Adult male Sprague-Dawley rats with (n=40) or without (n=40) ischemia were trained under each of three conditions: (1) motor balance and coordination training on Rota-rod; (2) simple exercise on treadmill; and (3) non-trained controls. Motor function was evaluated by a series of tests (foot fault placing, parallel bar crossing, rope and ladder climbing) before and at 14 or 28 days after training procedures in both ischemic and normal animals. Infarct volume in ischemic animals was determined with Nissl staining. Compared with both treadmill exercised and non-trained animals, Rota-rod-trained animals with or without ischemia significantly (P<0.01) improved motor performance of all tasks except for foot fault placing after 14 days of training, with normal rats having better performance. Animals trained for up to 28 days on the treadmill did not show significantly improved function. With regard to foot fault placing task, performance on foot placing was improved in ischemic rats across the three measurements at 0, 14 and 28 days regardless of training condition, while the normal group reached their best performance at the beginning of measurement. No significant differences in infarct volume were found in rats trained either with Rota-rod (47+/-4%; mean+/-S.E.), treadmill (45+/-5%) or non-exercised control (45+/-3%). In addition, no obvious difference could be detected in the location of the damage which included the dorso-lateral portion of the neostriatum and the frontoparietal cortex, the main regions supplied by the middle cerebral artery. The data suggest that complex motor training rather than simple exercise effectively improves functional outcome.

Measurement of free fatty acids in cerebrospinal fluid from patients with hemorrhagic and ischemic stroke

Free fatty acid (FFA) concentrations in cerebrospinal fluid (CSF) from patients with ischemic and hemorrhagic stroke (n=25) and in contemporary controls (n=73) were examined using HPLC. Concentrations of CSF FFAs from ischemic and hemorrhagic stroke patients obtained within 48 h of the insult were significantly greater than in control patients. Higher concentrations of polyunsaturated fatty acids (PUFAs) in CSF obtained within 48 h of insult were associated with significantly lower (P<0.05) admission Glasgow Coma Scale scores and worse outcome at the time of hospital discharge, using the Glasgow Outcome Scale (P<0.01).

Interactive Image-Guided Management of Colloid Cysts of the Third Ventricle

OBJECT

Image guidance provides a three-dimensional view of the lesion and allows the surgeon to plan a surgical strategy that takes the relationship of the lesion and the surrounding brain into account. We evaluated the degree of resection and the functional outcome of patients with colloid cysts from the third ventricle submitted to surgical resection using interactive image-guided approach.

METHOD

Using image-guided methodology and an endoscopic approach we analyzed the functional outcome of 11 patients with diagnosis of colloid cyst of the third ventricle who were treated at our institution from August 1993 to September 2000. The mean age was 39.5 years and the mean follow-up was 36.5 months. Analyzing the clinical outcome, 54.5% of the patients developed short-term memory disturbance in the first 30 days after surgery. None of these patients persisted with this symptomatology for more than one month. In terms of late post-operative morbidity, 1 patient developed persistent post-operative seizures, which were controlled with anti-seizure medications. Complete resection of the cyst was achieved in all patients.

CONCLUSIONS

The low rate of complications and high rate of total resection encourage us to continue using the multimodal technique. Longer follow-up and an increase in the number of patients are needed to assess the efficacy of this methodology.

Effects of immunosuppressants, calcineurin inhibition, and blockade of endoplasmic reticulum calcium channels on free fatty acid efflux from the ischemic/reperfused rat cerebral cortex

Elevated levels of free fatty acids (FFA) have been implicated in the pathogenesis of neuronal injury and death induced by cerebral ischemia. This study evaluated the effects of immunosuppressants agents, calcineurin inhibitors and blockade of endoplasmic reticulum (ER) calcium channels on free fatty acid formation and efflux in the ischemic/reperfused (I/R) rat brain. Changes in the extracellular levels of arachidonic, docosahexaenoic, linoleic, myristic, oleic and palmitic acids in cerebral cortical superfusates during four-vessel occlusion-elicited global cerebral ischemia were examined using a cortical cup technique. A 20-min period of ischemia elicited large increases in the efflux of all six FFAs, which were sustained during the 40 min of reperfusion. Cyclosporin A (CsA) and trifluoperazine, which reportedly inhibit the I/R elicited opening of a mitochondrial permeability transition (MPT) pore, were very effective in suppressing ischemia/reperfusion evoked release of all six FFAs. FK506, an immunosuppressant which does not directly affect the MPT, but is a calcineurin inhibitor, also suppressed the I/R-evoked efflux of FFAs, but less effectively than CsA. Rapamycin, a derivative of FK506 which does not inhibit calcineurin, did not suppress I/R-evoked FFA efflux. Gossypol, a structurally unrelated inhibitor of calcineurin, was also effective, significantly reducing the efflux of docosahexaenoic, arachidonic and oleic acids. As previous experiments had implicated elevated Ca(2+) levels in the activation of phospholipases with FFA formation, agents affecting endoplasmic reticulum stores were also evaluated. Dantrolene, which blocks the ryanodine receptor (RyR) channel of the ER, significantly inhibited I/R-evoked release of docosahexaenoic, arachidonic, linoleic and oleic acids. Ryanodine, which can either accentuate or block Ca(2+) release, significantly enhanced ischemia/reperfusion-elicited efflux of linoleic acid, with non-significant increases in the efflux of myristic, arachidonic, palmitic and oleic acids. Xestospongin C, an inhibitor of the inositol triphosphate (IP(3)R) channel, failed to affect I/R-evoked FFA efflux. Thapsigargin, an inhibitor of the Ca(2+)-ATPase ER uptake pump, elicited significant elevations in the efflux of myristic, arachidonic and linoleic acids, in the absence of ischemia. Collectively, the data suggest an involvement of both ER and mitochondrial Ca(2+) stores in the chain of events which lead to PLA(2) activation and FFA formation.

Differential effects of phospholipase inhibitors on free fatty acid efflux in rat cerebral cortex during ischemia-reperfusion injury

Free fatty acid (FFA) elevation in the brain has been shown to correlate with the severity of damage in ischemic injury. The etiology of this increase in FFA remains unclear and has been hypothesized to result from phospholipase activation. This study examines the effects of specific phospholipase inhibitors on FFA efflux during ischemia-reperfusion injury. A four-vessel occlusion model of cerebral ischemia was utilized to assess the effects of PLA(2) and PLC inhibitors on FFA efflux from rat cerebral cortex. In addition, FFA efflux from non-ischemic cortices exposed to PLA(2) and PLC was measured. Concentrations of arachidonic, docosahexaenoic, linoleic, myristic, oleic, and palmitic acids in cortical superfusates were determined using high performance liquid chromatography (HPLC). Exposure to the non-selective PLA(2) inhibitor 4-bromophenylacyl bromide (BPB) significantly inhibited FFA efflux during ischemia-reperfusion injury (P<0.01 arachidonic, oleic and palmitic; P<0.05 all others); exposure to the PLC inhibitor U73122 had no observed effect. The effects of the Ca(2+)-dependent PLA(2) inhibitor arachidonyl trifluoromethyl ketone (AACOCF(3)) mirrored the effects of BPB and led to reductions in all FFA levels (P<0.01 arachidonic, oleic and palmitic; P<0.05 all others). Exposure to the secretory PLA(2) inhibitor 3-(3-acetamide-1-benzyl-2-ethyl-indolyl-5-oxy) propane sulfonic acid (LY311727) and to the Ca(2+)-independent PLA(2) inhibitor bromoenol lactone (BEL) had only minimal effects on FFA efflux. Application of both PLA(2) and PLC to non-ischemic cortices resulted in significant increases in efflux of all FFA (P<0.05). The study suggests that FFA efflux during ischemia-reperfusion injury is coupled to activation of Ca(2+)-dependent PLA(2) and provides further evidence of the potential neuroprotective benefit of Ca(2+)-dependent PLA(2) inhibitors in ischemia.

Quantification of free fatty acids in human cerebrospinal fluid

Free fatty acids (FFA) in cerebrospinal fluid (CSF) are well-recognized markers of brain damage in animal studies. Information is limited regarding human CSF in both normal and pathological conditions. Samples of CSF from 73 patients, who had undergone lumbar puncture for medically indicated reasons, came from a core laboratory upon completion of ordered tests. Using high performance liquid chromatography, mean FFA concentrations (microg/L +/- SEM) were: arachidonic 26.14 +/- 3.44; docosahexaenoic 60.74 +/- 5.70; linoleic 105.07 +/- 10.98; myristic 160.38 +/- 16.17; oleic 127.91 +/- 10.13; and palmitic 638.34 +/- 37.27. No differences in FFA concentrations were seen with gender, race, age, and/or indication for lumbar puncture. This is the first study to document normal human CSF FFA concentrations in a large series. Further characterization of FFA in pathological conditions may provide markers for evaluating clinical treatments and assisting in prognostication of neurological disease.

Inhibition of Na(+)/Ca(2+) exchange by KB-R7943, a novel selective antagonist, attenuates phosphoethanolamine and free fatty acid efflux in rat cerebral cortex during ischemia-reperfusion injury

Reversal of the Na(+)/Ca(2+) exchanger (NCX) occurs during ischemia-reperfusion injury as a result of changes in intracellular pH and sodium concentration. Inhibition of NCXs has been shown to be neuroprotective in vitro. In this study, we evaluated the effects of KB-R7943 (50 microM), a specific inhibitor of the reverse mode of NCX, applied topically onto rat cerebral cortex prior to and during ischemia. Amino acid and free fatty acid levels in cortical superfusates, withdrawn at 10-min intervals from bilateral cortical windows, were analyzed by high-performance liquid chromatography. During a 20-min period of ischemia in control animals, there were significant increases in all amino acids and in all FFAs. Following reperfusion, all FFAs remained significantly elevated. Application of KB-R7943 (50 microM) significantly inhibited effluxes of phosphoethanolamine, but had no effect on glutamate, aspartate, taurine or GABA levels. KB-R7943 also resulted in significant reductions in levels of myristic, docosahexaenoic and arachidonic acid during ischemia and in reperfusion levels of arachidonic and docosahexaenoic acids. These data indicate that inhibition of Na(+)/Ca(2+) exchange likely prevented the activation of phospholipases that usually occurs following an ischemic insult as evidenced by its attenuation of phosphoethanolamine and free fatty acid efflux. The inhibition of phospholipases may be an essential component of the neuroprotective benefits of Na(+)/Ca(2+) exchange inhibitors in ischemia-reperfusion injury and may provide a basis for their possible use in therapeutic strategies for stroke.

Long-term neuroprotective effect of inhibiting poly(ADP-ribose) polymerase in rats with middle cerebral artery occlusion using a behavioral assessment

Poly(ADP-ribose) polymerase (PARP) can initiate an energy-consuming and inefficient repair cycle following cerebral ischemia/reperfusion by transferring ADP ribose units to nuclear proteins eventually leading to cellular dysfunction and neuronal death. 3-Aminobenzamide (3-AB) is a selective inhibitor of PARP that can significantly reduce brain damage after focal ischemia in rats and displays a low toxicity in vivo. The goals of this study were to determine if inhibiting PARP with 3-AB has a long-term neuroprotective effect and if functional outcome improves in rats following focal ischemia and treatment with 3-AB. Focal ischemia was induced by a 2-h occlusion of the middle cerebral artery (MCA), using an intraluminal filament. Motor functions were evaluated from 5 to 28 days after reperfusion in four groups of rats: stroke without treatment; stroke treated with 3-AB at doses of 15 mg/kg, stroke treated with 3-AB at doses of 55 mg/kg; and the non-ischemic control rats. Functional behaviors were tested by a series of motor function tasks (foot placing, parallel bar crossing, rope and ladder climbing), as well as a neurological examination. Infarct volume of stroke brain in the same rat was determined by Nissl staining 28 days after surgery. Comparison of the untreated stroke group (n=11) and the treated stroke groups indicates that impairment of motor function was significantly (P<0.001) reduced by administration of 3-AB at doses of 15 mg/kg (n=9) or 55 mg/kg (n=10). Neurological outcome was also improved significantly (P<0.001). Infarct volume was significantly (P<0.01) reduced in both treated groups. Long-term neuroprotection following ischemia/reperfusion injury to the brain can be obtained by administration of a PARP inhibitor. The motor tests employed in this study can be used as sensitive, objective and reproducible measurements of functional impairment in rats following an ischemic stroke.

Inhibition of Na(+)/H(+) exchange by SM-20220 attenuates free fatty acid efflux in rat cerebral cortex during ischemia-reperfusion injury

The Na(+)/H(+) exchanger (NHE) is activated during ischemia-reperfusion in an effort to restore intracellular pH to normal levels. Inhibition of NHE with non-selective amiloride derivatives has been shown to be neuroprotective and to attenuate free fatty acid efflux during ischemia-reperfusion. We evaluated the effects of SM-20220 (20 microM), a highly selective and specific NHE inhibitor, applied topically onto rat cerebral cortex prior to and during a 20-min period of ischemia. SM-20220 application significantly reduced the ischemia-evoked efflux of myristic, palmitic, and arachidonic acids during both ischemia and reperfusion with significant decreases in linoleic and docosahexaenoic levels during reperfusion. This study confirms the importance of NHEs in eliciting free fatty acid efflux, inhibition of which may be an essential component of the neuroprotective benefits of NHE inhibitors in ischemia-reperfusion injury.

Transplantation of human fetal brain cells into ischemic lesions of adult gerbil hippocampus

OBJECT

The goal of this study was to establish whether transplanted cells derived from fetal human brain can survive in an ischemic lesion.

METHODS

Sixteen adult male Mongolian gerbils underwent transient bilateral common carotid artery occlusion. One week later, cell suspensions prepared from fetal human brain were injected using stereotactic guidance into the CA1 region of the hippocampus on one side. On the contralateral side injection of the cell suspension medium only was performed. One week after transplantation, the animals were perfusion fixed and their brains were processed for histological studies as well as expression of neuron and glia-specific antigens. Data from ischemic animals were compared with eight nonischemic gerbils that served as sham-operated controls. Last, the in vivo data were correlated with observations made from matching in vitro cultures of the fetal brain cell suspension. The in vivo data indicated that transplanted human fetus-derived brain cells survived in ischemic lesions of gerbil hippocampus after 1 week, provided that the host animal underwent adequate immunosuppression and the transplanted cells were not incorporated into the scar caused by the transplantation procedure. Unlike their in vivo counterparts, after 1 week, most cultured fetal brain cells expressed either neuron- or astrocyte-specific antigens.

CONCLUSIONS

This work demonstrates that xenotransplanted fetal human brain cells are able to survive in an ischemic lesion in a rodent model. These data might be useful for future neural transplantation studies of treatments for cerebrovascular ischemia in humans.

An efficient method for the culturing and generation of neurons and astrocytes from second trimester human central nervous system tissue

The isolation, culturing and expansion of human neural progenitors cells has important potential clinical applications in cellular transplantation strategies as well as in developmental studies involving the central nervous system (CNS). This study describes an efficient method to culture neurons and astrocytes as primary cultures, as well as from proliferative progenitor cells derived from second trimester fetal CNS tissue. Second trimester fetal human tissue was mechanically dissociated and subjected to trypsin-dissociation and trituration. The resulting suspension was passed over a Percoll density gradient. The middle (second) fraction of cells was centrifuged to yield a homogenous population of cells with 80%-90% viability. These cells were either cultured directly on laminin coated dishes with defined medium supplemented with fetal bovine serum or in defined medium supplemented with growth factors including epidermal growth factor, basic fibroblast growth factor and leukemia inhibitory factor. The primary cell cultures yielded neurons and astrocytes after 3-5 days in vitro verified by immunostaining with MAP2ab and GFAP. Cells exposed to growth factor supplemented medium formed free-floating spheres within one week. Upon growth factor removal and plating on laminin-coated dishes, brain derived spheres gave rise to neurons, astrocytes and oligodendrocytes; spinal cord derived spheres generated only astrocytes. This protocol describes an efficient method to generate and culture neurons and astrocytes from second trimester human CNS tissue that may be useful in transplantation and developmental studies.

Intervertebral foraminal ligaments of the lumbar spine: anatomy and biomechanics

The anatomical existence of the transforaminal ligaments has been studied extensively. However, there are very few studies examining how the transforaminal ligaments could be involved in the causation of nerve root compression and the low back pain syndrome. In this article, the authors review earlier studies in an attempt to find anatomical and biomechanical correspondence between the intervertebral foraminal ligaments of the lumbar spine and the low back pain syndrome.

Biomechanical properties of calvarium prosthesis

There are many materials available for the reconstruction of calvarial defects. Even though their biomaterial properties are well known, the biomechanical properties as part of the calvarium have not been investigated. In this article, calvarial implants are reviewed with their historic development into modern cranioplasty. Materials for trephined skulls are classified by their category. Individual parameters to describe their mechanical properties are collected and revealed in detail. The laboratory testing methodology for cranioplasty material is introduced to understand each parameter. At last, we discuss an engineering technique to look into the implant behavior. Since there is no standard goal for the biomechanical and biomaterial point of view for cranioplasty, this article suggests the finite element method for evaluation of the implant behavior and the degree of damage upon the impact injury.

Comparison of neural precursor cell fate in second trimester human brain and spinal cord

Neural transplantation holds promise for the treatment of traumatic brain and spinal cord injury by replacing lost cellular elements as well as repairing neural damage. Fetal human stem cells derived from central nervous system (CNS) tissue are potential transplantable sources for all cell types found in the mature human nervous system including neurons, astrocytes and oligodendroglia. Although nearly all areas of the fetal human neuraxis contain undifferentiated neural precursor cells, the phenotypic fate of the daughter cells might vary from one region to another during a specific developmental period. The purpose of this study was to compare the various cell types derived from neural precursors cultured from second trimester fetal human brain and spinal cord. To this end, brains (n = 8) and spinal cords (n = 8) of 15-24 week fetuses were dissociated and grown in culture medium supplemented with epidermal growth factor (EGF), basic fibroblast growth factor (FGF) and leukemia inhibitory factor (LIF). The proliferating precursor cells from both brain and spinal cord grew as spherical masses that were plated on laminin-coated dishes after seven days in culture. During the next 5-7 days, the cells that emerged from these spheres were fixed and processed for immunocytochemistry. Brain derived spheres gave rise to cells expressing antigens specific for neurons (MAP-2ab and neuron specific-intermediate filaments), astrocytes (GFAP) and oligodendrocytes (A007). In contrast, cells that emerged from spinal cord derived spheres were only immunoreactive for GFAP. These data suggest that neuroepithelial precursor cells from different CNS regions, although similar in their responsiveness to proliferative growth factors, might differ in their ability to generate different cell types in the adult CNS.

Vascular injury in neurotrauma

Traumatic vascular lesions can occur after severe or even the most mild of head and cervical trauma. The initial evaluation of the injured patient must be thorough and the clinical suspicion of vascular injury must be highly suspected based on the mechanism of injury. Traumatic vascular injuries can be broadly classified into traumatic aneurysms, dissections and occlusions and fistulae of the carotid or vertebral arteries. The current management and treatment options of each condition are discussed.

Real-time measurement of glutamate release from the ischemic penumbra of the rat cerebral cortex using a focal middle cerebral artery occlusion model

Following permanent middle cerebral artery occlusion, extracellular penumbral glutamate levels, measured by a real-time glutamate electrode, increased in two different patterns. In 7/11 rats, glutamate increased from baseline levels of 19+/-4 (mean+/-SEM) to 208+/-29 microM and then declined towards baseline levels. Blood flow in the penumbral area declined to 30% of pre-ischemic levels with recovery to 60 and 70% of baseline values by 3 and 6 h, respectively. Four of 11 rats in the study also exhibited late peaks of glutamate release (120+/-40 microM ) 2 h after the onset of ischemia. There were no changes in the EEG recordings or cerebral blood flow during these late glutamate peaks.

The effect of streptozotocin-induced diabetes on the release of excitotoxic and other amino acids from the ischemic rat cerebral cortex

OBJECTIVE

Hyperglycemic stroke results in increased neuronal damage, the exact mechanism of which is unknown. Lactic acidosis has been implicated; however, increases in the excitotoxic amino acid glutamate, which correlate with increased neuronal damage, may be the cause for the increased damage seen in hyperglycemic stroke.

METHODS

Ten Sprague-Dawley rats were treated with streptozotocin (STZ; 50 mg/kg), and 12 normoglycemic rats were used as controls. Using a four-vessel occlusion model, global ischemia was assessed at 5 to 7 days after treatment in five animals (acute STZ group) or at 4 to 6 weeks after treatment in five animals (chronic STZ group). The cortical cup model was used to collect superfusates under basal, ischemic, and reperfusion conditions and analyzed for nine different amino acids using high-performance liquid chromatography.

RESULTS

Plasma glucose levels were significantly higher in the acute and chronic STZ groups as compared with the control group. Plasma lactate levels were higher in the acute STZ group as compared with the control or chronic STZ groups. Extracellular cortical glutamate levels were significantly reduced during reperfusion in the acute STZ group and during ischemia/reperfusion in the chronic STZ group as compared with the controls. Levels of extracellular gamma-aminobutyric acid were significantly reduced in the acute and chronic STZ groups as compared with the controls.

CONCLUSION

A chronic state of hyperglycemia results in reduction in extracellular brain glutamate levels during ischemia/reperfusion and therefore does not appear to be responsible for the increased neuronal damage seen in diabetic stroke. Chronic hyperglycemia also causes decreased extracellular gamma-aminobutyric acid levels, which, because of the loss of the inhibitory effects of this neurotransmitter, could contribute to the increased damage observed in hyperglycemic stroke.

Application of finite element analysis in neurosurgery

With the rapid development of computer equipment, approximation by analytical solutions has become popular in mathematical modeling. Finite element (FE) analysis uses numerical methods to solve problems with physical phenomena, and these can be applied to various geometrically complex materials, such as brain. The FE formulation can provide such diverse domains as heat conduction, torsion of elastic material, diffusion and fluid flow, and it can view different objects of study in the neurosurgical field. In this article, the various applications of FE methods are introduced to illustrate the usefulness of the technique and the link between the external biomechanical aspect and internal phenomena in brain research.

An unusual subdural empyema: case report

Subdural empyema in a 38-year-old patient with congenital hemangioma, suppurative parotitisis, soft tissue phlegmonia and osteomyelitis is reported. The clinical, radiological and surgical features are outlined. A review of the literature reveals the uniqueness of this case.

Cellular transplantation and spinal cord injury

Spinal cord injury is often characterized by immediate and irreversible loss of sensory and motor functions below the level of injury. Cellular transplantation in various experimental models of spinal cord injury has been used as a strategy for reducing deficits and improving functional recovery. The general strategy has been aimed at promoting regeneration of intrinsic injured axons with the development of alternative pathways that facilitate a partial functional connection. Other objectives of cellular transplantation studies have included replacement of lost cellular elements, alleviation of chronic pain, and modulation of the inflammatory response after injury. This review focuses on the cell types that have been used in spinal cord transplantation studies in the context of evolving biological perspectives, technological advances, and new therapeutic strategies and serves as a point of reference for future studies.

The effect of topical insulin on the release of excitotoxic and other amino acids from the rat cerebral cortex during streptozotocin-induced hyperglycemic ischemia

Insulin has been demonstrated to be neuroprotective in brain and spinal cord ischemia. The mechanism of neuroprotection may involve alterations in metabolism, protein synthesis or uptake of GABA by astrocytes. Conversely, hyperglycemia increases the extent of neurologic damage observed during ischemia/reperfusion. Diabetic patients are 2-4 times more likely to suffer a stroke as normoglycemic patients and they also have worsened neurologic outcome. Determining if insulin, which many diabetics already use as therapy, can be neuroprotective, would be a possible means of alleviating the detrimental outcome from diabetic stroke. This study looked at the relationship between topically administered insulin (1 mIU insulin/ml and 100 mIU insulin/ml) during a four vessel occlusion model of global ischemia and the release of amino acids, especially glutamate, from the cortex in streptozotocin (STZ)-treated rats. The rats were utilized either 5-7 days (ASTZ) or 4-6 weeks (CSTZ) after a single STZ injection. In the ASTZ animals both doses of insulin increased the amount of the excitotoxic amino acids, aspartate and glutamate, released during reperfusion and the higher dose also increased the levels of taurine and GABA during reperfusion. In the CSTZ animals, both doses of insulin increased the amount of excitotoxic amino acids during reperfusion and the lower dose increased GABA levels released during reperfusion. The differences between the ACTZ and CSTZ animals may be due to metabolic differences in the utilization of glucose. Insulin may act as a neuroprotectant by increasing extracellular GABA resulting in neuroinhibition.

The effect of intravenous insulin on accumulation of excitotoxic and other amino acids in the ischemic rat cerebral cortex

Insulin has been reported to be neuroprotective during cerebral ischemia/reperfusion. However, it may also increase the sensitivity of cultured cortical neurons to glutamate toxicity. The experiments described here utilized a rat four-vessel occlusion model with cerebral cortical windows to determine the effects of intravenous insulin, alone (I) or combined with glucose (IG) to maintain physiologic blood glucose levels, on the extracellular accumulation of amino acids in superfusates of the cerebral cortex. Aspartate, phosphoethanolamine, taurine and gamma-aminobutyric acid were increased in the I and IG groups and glutamate was increased in the IG group compared to controls during ischemia/reperfusion. Insulin treatment attenuated the rebound in cortical superfusate glucose levels in both groups of animals during reperfusion. The increases in amino acid release during reperfusion may be due to a lack of glycolytically derived energy available for amino acid uptake systems and ionic pumps.

Impact simulation on pre-formed prosthesis for large cranial defect

Cranioplasty greater than 10 cm2 in size is challenging task for neurosurgeon. There are many successful trials to fill the small defect with various materials. Proper cranioplasty can provide subsequently restoration of cerebral protection, cosmetic aspect and neuronal function. However, larger defect may not provide adequate protection from the auto, industrial or sport accident even with cranioplasty. In this study, patch design using two popular materials was evaluated and compared with bone material. Then impact-releasing holes were implemented to the patch. The movement of the large patch and its effect on the underlying brain tissue upon simulated impact was evaluated by using finite element analysis.

Application accuracy study of a semipermanent fiducial system for frameless stereotaxis

The accuracy of a semipermanent fiducial marker system developed at Wayne State University in collaboration with Fisher-Leibinger (Freiburg, Germany) was compared with reference to a standard stereotactic frame (Zamorano-Dujovny Localizing Unit; Fisher-Leibinger). For each patient in our study, 10 semipermanent markers were placed on the skull through a small incision and a pilot hole drilled for the marker; five markers were used for registration, and five were used for comparison. Gadolinium-enhanced magnetic resonance imaging was performed, and, upon registration using both ring and fiducial markers, 184 random points were collected by infrared digitization. All three-dimensional measurements (x, y, z) were converted into distance values correlating each value to the origin by the formula dij = SQRT (xij2 + yij2 + zij2). The mean difference of fiducial coordinates vs. absolute image coordinates was 1.72 +/- 0.42 mm (P = .0001), implying no significant difference. The mean difference in dij of the stereotactic ring coordinates vs. the absolute image coordinates was 3.35 +/- 0.59 mm (P = .00011). The mean difference in the fiducial markers vs. the stereotactic ring coordinates was 2.95 +/- 0.45 mm (P = .0001). All tests were declared significant at alpha = .016. The combination of interactive guidance with semipermanent fiducial markers allows for accurate localization of intracranial targets (as accurate or even more accurate than the stereotactic frame). Semipermanent fiducial markers facilitate the procedure logistically, allow for staged procedures (i.e., at the skull base or in epilepsy), and provide access for combined supra- and infratentorial approaches. We believe that the semipermanent fiducial markers system might represent an important development leading toward widespread use of interactive image guidance in conventional neurosurgery.

Three-dimensional magnetic resonance angiography in the planning of aneurysm surgery

Standard planning for intracranial aneurysm surgery relies on the surgeon's intellectual reconstruction of the three-dimensional (3D) surgical field on the basis of a two-dimensional (2D) imaging modality, biplanar cerebral angiography. This method is relatively imprecise, and it relies on previous experience for optimal results. We describe a stereotactic magnetic resonance angiographic (MRA)-guided method based on computer segmentation techniques for the planning of aneurysm surgery that has the potential of bringing a 3D perspective to the lesion. The method has been evaluated retrospectively on 20 surgical patients in whom the aneurysm orientation and relationship to parent vessels were shown to match presurgical 3D stereotactic display. When it is adapted to frameless interactive surgical navigation, this method may become a useful adjunct in the surgical obliteration of these life-threatening lesions.

Topical insulin and accumulation of excitotoxic and other amino acids in ischemic rat cerebral cortex

Insulin plays a neuroprotectant role in the brain and spinal cord during ischemia. However, studies have shown insulin to increase the sensitivity of cultured cortical cells to glutamate toxicity. The present study looked at the relationship between topically administered insulin (1 mIU insulin/ml and 100 mIU insulin/ml) during a four-vessel model of global ischemia and the accumulation of amino acids, especially glutamate, from the ischemic rat cerebral cortex. The lower dose of insulin was found to attenuate the release of excitotoxic and other amino acids from the cortex in ischemia/reperfusion. This may occur because insulin increases glucose availability to glial cells resulting in maintenance of glycolysis and ionic pumps that can reduce glutamate release and maintain uptake during ischemia/reperfusion. The higher dose of insulin, which significantly increased the amount of aspartate, glutamate, taurine, and GABA during reperfusion, may act to stimulate the amount of glycogen stored in astrocytes, reducing the availability of glucose for metabolic purposes.

The relationship of blunt head trauma, subarachnoid hemorrhage, and rupture of pre-existing intracranial saccular aneurysms

Patients with a history of closed head trauma and subarachnoid hemorrhage are uncommonly diagnosed with an intracranial saccular aneurysm. This study presents a group of patients in whom a pre-existing aneurysm was discovered during work-up for traumatic subarachnoid hemorrhage. Without an accurate pre-trauma clinical history, it is difficult to define the relationship between trauma and the rupture of a pre-existing intracranial saccular aneurysm. We retrospectively reviewed 130 patients who presented to Detroit Receiving Hospital between 1993 and 1997 with a diagnosis of subarachnoid hemorrhage (SAH). Of these 130 patients, 70 were spontaneous, and 60 had a history of trauma. Mechanisms of trauma include motor vehicle accident, assault, or fall from a height. Of the 60 patients with subarachnoid hemorrhage and a history of trauma, 51 (86%) did not undergo conventional four-vessel angiography, and had no further neurological sequelae. Nine patients (14%) had a suspicious quantity of blood within the basal cisterns or Sylvian fissure and had a four-vessel angiogram. Five patients (8%) were diagnosed with a saccular intracranial aneurysm, and all underwent surgical clipping of the aneurysm. We conclude that the majority of patients (92%), with post-traumatic SAH do not harbor intracranial aneurysms. However, during initial evaluation, a high level of suspicion must be entertained when post-traumatic subarachnoid hemorrhage is encountered in the basal cisterns or Sylvian fissure, as 8% of our population were diagnosed with aneurysms.

A brief review of the effects of chronic hydrocephalus on the gonadotropin releasing hormone system: implications for amenorrhea and precocious puberty

Precocious puberty and amenorrhea have been associated with hydrocephalus, but the pathogenesis has not been determined. Approximately 22 cases of amenorrhea, and a few cases of precocious puberty, have been reported in hydrocephalic patients. Shunt treatment leads to initiation and maintenance of normal reproductive cycles in most cases. An underlying mechanism responsible for reproductive dysfunction may involve the role of gonadotrophin releasing hormone (GnRH). The exact pathway by which hydrocephalus disrupts the hypothalamic GnRH system is unknown. However, compressive forces, ischemia, and impairment of neurotransmitter feedback loops are likely candidates.

Topical glucose and accumulation of excitotoxic and other amino acids in ischemic cerebral cortex

Pre-ischemic hyperglycemia aggravates brain damage due to transient global ischemia as demonstrated by exacerbation of brain lesions. Lactacidosis and elevated glutamate levels have been implicated as mechanisms of the increased damage. Our objective was to determine the effects of different levels of glucose (0, 66.5, 450 mg/dL) in cortical superfusates on the ischemia/reperfusion-evoked release of amino acids from the rat cerebral cortex. Physiologic levels of glucose significantly reduced the amount of aspartate, glutamate and gamma-aminobutyric acid and the supra-physiologic levels of glucose reduced the amount of aspartate and phosphoethanolamine released from the cortex during ischemia/reperfusion in comparison with no glucose. The decrease in glutamate release may be due to increased availability of glucose for glycolysis with the subsequent formation of ATP and lactate, which has been shown to act as an energy source for neurons. The decreased levels may also reflect the continued energy-dependent uptake of glutamate by glial cells.

Spinal aspergillus osteomyelitis

Aspergillus species are uncommon etiologic agents of vertebral osteomyelitis. We describe two patients with lumbar vertebral aspergillosis precipitated by the use of corticosteroids and review 39 cases in the literature. The mean age of the population was 40.04 years. There was male predominance (78% of cases), mainly lumbar involvement (53.7%), and monomicrobial nature of infection; 65.8% of the patients had predisposing factors, while 34.1% had none. Back pain (53.6% of cases) was the predominant symptom, while neurological deficits were present in 29.2% of the patients. White blood cell counts were elevated in 12.2% of the patients, and erythrocyte sedimentation rates were >40 mm/h in 39%. The overall recovery rate was 68.3%, and the mortality rate was 26.8%. Although aspergillus osteomyelitis is primarily treated medically, certain cases may require surgical intervention.

Surgical management of complex middle cerebral artery aneurysms

Complex middle cerebral artery (MCA) aneurysms are defined in this review as aneurysms larger than 20 mm, arising from the MCA bifurcation, and requiring unusual surgical approaches for their obliteration. The direct surgical approaches to complex MCA aneurysms can be divided into five techniques: 1) direct clipping, 2) trapping, 3) trapping and extracranial-intracranial anastomosis, 4) excision and end-to-end anastomosis, and 5) external wrapping. The pertinent surgical anatomy, preoperative preparation, intraoperative procedures, operative approaches, and potential complications will be reviewed.

Patterns of immediate early gene mRNA expression following rodent and human traumatic brain injury

Cell stimulation which leads to degeneration triggers a prolonged wave of immediate early gene (IEG) transcription that correlates with neuronal demise. In order to determine the relevance of the prolonged IEG response to human traumatic brain injury, we analyzed IEG mRNA levels in brain tissue isolated following a controlled penetrating injury and an injection of the excitotoxin Quinolinic acid (QA), as well as from tissue recovered during routine neurosurgery for trauma. Total RNA was extracted from tissue and subjected to Northern analysis of IEG mRNAs (c-fos and zif/268). Both models produced rapid and prolonged waves of IEG transcription that appeared to correlate with the severity of injury. Increases in zif/268 mRNA were observed within 1 h with levels reaching their peak at 6 h following excitotoxic injury and 3 h following a controlled penetration. In general, human traumatic brain injury resulted in variable increases in IEG mRNA levels following traumatic injury with the largest IEG mRNA increases observed in tissue collected 0-10 h after injury. This post-injury time corresponds to the peak of the prolonged IEG response observed in rodents following excitotoxic injury. Comparisons were made in IEG response between rodent frontal cortex and human cortex, because the majority of the human tissue originated from the cerebral cortex. These results further support the hypothesis that prolonged IEG transcription serves as a marker of traumatic brain injury and may play a role in neurodegeneration and/or glial activation. Moreover, observations of similar IEG patterns of expression reinforces the importance of rodent models of brain injury providing useful information directly applicable to human brain injury.

Experimental animal models of traumatic brain injury: medical and biomechanical mechanism

The numerous traumatic brain injury models were designed to study the nature of the human brain injury. The properties of six experimental injury models were reviewed in this article. Weight-drop models with or without skull protection were compared in terms of experimental setup, possible error source, and biomechanical prospect. The modified percussion models with or without rigid cortical impact were contrasted with regard to reliability, histopathological production, and deformation. The focal contusion model by mechanical suction force represented isolated cortical injury without compression brain injury. As a class of traumatic brain injury, brain retraction damage was reviewed in this article.

Cerebral monitoring devices: analysis of complications

The use of indwelling cerebral monitoring devices (ICMDs) is common in the intensive care of neurosurgical patients. ICMDs are used to measure and treat intracranial pressure (ICP), temperature, blood flow and the microchemical environment. Intracranial hemorrhage (ICH) and infection are risks of ICMD use [4]. This study presents ICMD use at Detroit Receiving Hospital (DRH) from July 1993- March 1997. Analysis of complications associated with ICMD placement will test the hypothesis that complication rate depends upon type of ICMD used. A log of all patients having ICMDs at DRH has been kept since 1993. This log was used to identify complications of ICMD placement. Each case was reviewed and the following data obtained: diagnosis, patient age, initial Glasgow Coma Score, Glasgow Outcome Score, type of ICMD, number of ICMDs per patient, duration of implant and complication. Descriptive and non-parametric statistics were used to compare samples of interest. The following number of ICMDs were placed: 274 ventriculostomies, 229 Camino intra parenchymal ICP monitors, and 33 other ICMDs. Complications in these 536 cases include 21 infections, 15 ICHs, 1 granuloma and 1 persistent cerebrospinal fluid leak. Complication was analyzed as a function of ICMD type using Chi-Square test for independence. The rate of infection and ICH was significantly higher in the ventriculostomy group (p = 0.0001). These results support the hypothesis that complications of ICMD use are due to the type of device implanted. The determinants of ICMD complication is undoubtedly multifactorial. The clinician must consider the complication rate related to a particular ICMD among other factors when choosing to place an ICMD.

Use of interactive-intraoperative guidance during vertebrectomy and anterior spinal fusion with instrumental fixation: technical note

Anterior decompressive procedures for the treatment of vertebral tumors have become increasingly popular in an attempt to improve the quality of life, relieve pain, and preserve or restore neurologic function. However, these procedures carry a significant rate of complications including hardware failure, due in part to technical factors. A computer-assisted system allowing for precise preoperative planning and real-time intraoperative interactive image localization has been implemented for spine instrumentation to optimize anterior instrumental fixation. We discuss our initial clinical experience and application to anterior vertebrectomy, and vertebral reconstruction with anterior instrumental fixation. We believe that computer-assisted spine surgery using infrared-based technology offers the necessary elements to make its use fast, reliable, and intuitive, providing an accurate and safe approach for optimization of spine surgery.

A cohort study of the safety and feasibility of intraventricular urokinase for nonaneurysmal spontaneous intraventricular hemorrhage

BACKGROUND AND PURPOSE

Small case series have reported potential benefit from thrombolysis after spontaneous intraventricular hemorrhage (IVH). Our objective was to review our experience using intraventricular urokinase (UK) in treating selected patients with IVH.

METHODS

Using medical records, we identified all patients who received ventriculostomies for CT-confirmed nonaneurysmal nontraumatic spontaneous IVH from December 1992 through November 1996. We reviewed charts and CT images and examined the data for associations with specific outcomes.

RESULTS

We identified 40 patients, 18 treated with ventriculostomy alone and 22 receiving adjunctive intraventricular UK. The initial Glasgow Coma Scale (GCS) scores of the two groups were similar (P = 0.5). While there was a trend for patients with any intraparenchymal hemorrhage (IPH) to receive UK (P = 0.07), the mean size of IPH in those who received ventriculostomy alone was larger than in those who received adjunctive UK (P = 0.002). There was lower mortality in the group treated with UK (31.8 versus 66.7%; P = 0.03), but there was only a trend toward an increase in favorable outcome (22.2% versus 36.4%; P = 0.3). Overall, the most significant association with outcome was neurological condition at presentation (GCS >5 versus < or = 5; P = 0.003). Receiving UK did not increase the occurrence of complications or hospital length of stay for survivors (P = 0.5).

CONCLUSIONS

Intraventricular UK remains a safe and potentially beneficial intervention. While it appeared to lower mortality, a randomized, placebo-controlled trial is needed to explore whether the therapy can increase the incidence of favorable outcomes.

Heat-shock protein 72 expression in excitotoxic versus penetrating injuries of the rodent cerebral cortex

The induction of heat shock protein 72 (hsp72) has been described in various experimental models of brain injury. The present study examined hsp72 expression patterns within the rodent cerebral cortex in experimental paradigms designed to mimic two mechanisms of damage produced by penetration of the cerebral cortex: (1) tissue tearing from the missile track and (2) diffuse excitotoxicity during temporary cavitation and shock wave formation. Adult male Spaque-Dawley rats received controlled penetration (stab) or injection of the NMDA receptor excitotoxin, quinolinic acid (QA), into the frontal cortex and were killed 1-24 h later. Tissue from the lesioned, sham-operated, or contralateral uninjected cortex was processed for Western and immunocytochemical analyses of hsp72 protein expression. By 12 h, both controlled penetration and excitotoxic brain injuries produced significant increases in hsp72 immunoreactivity, which decreased toward control levels at 24 h. However, the severity and regional distribution of hsp72 expression varied between the two models. Specifically, the controlled penetration injury produced many hsp72-expressing cells near the needle track, while immunoreactive cells within the QA-injected cortex were found in the periphery of the lesion site. Morphological assessment of brain sections subjected to dual-labeling procedures demonstrated that cells expressing hsp72 were primarily neuronal in both models of injury. These results suggest that although controlled penetration and diffuse excitotoxicity may induce similar temporal and cellular patterns of hsp72 expression, the spatial location of hsp72-immunoreactive cells may differ between the two models.

Patterns of heat-shock protein 70 biosynthesis following human traumatic brain injury

Heat-shock protein 70 (hsp70) is activated upon cellular stress/injury and participates in the folding and intracellular transport of damaged proteins. The expression of hsp70 following CNS trauma has been speculated to be part of a cellular response which is involved in the repair of damaged proteins. In this study, we measured hsp70 mRNA and protein levels within human cerebral cortex subjected to traumatic brain injury. Specimens were obtained during routine neurosurgery for trauma and processed for Northern mRNA and Western protein analysis. The largest increase in hsp70 mRNA levels was detected in trauma tissue obtained 4-6 h following injury. By 24 h, hsp70 mRNA levels were similar to nontrauma comparison tissues. hsp70 protein expression exhibited its greatest increases at 12-20 h post-injury. Immunocytological techniques revealed hsp70 protein expression in cells with neuronal-like morphology at 12 h after injury. These results suggest a role for hsp70 in human cortex following TBI. Moreover, since the temporal induction pattern of hsp70 biosynthesis is similar to that reported in the rodent, our observations validate the importance of rodent brain injury models in providing useful information directly applicable to human brain injury.

Multiresolution EEG comparison of rat ischemia models

Fourier transform of Electroencephalography (EEG) restricts EEG analysis due to its stationary properties with time change. It makes analysis difficult to ascertain the global effects of transient change in EEG signals. This study tested that multi-resolution analysis distinguishes different depths of ischemic insult related to the degree of residual blood flow in animal models. The results suggest that multi-resolution analysis demonstrate that little blood flowing to the brain has more detrimental effect to the EEG properties than no blood flowing, which is contrary to the common sense.

Real-time measurement of ischemia-evoked glutamate release in the cerebral cortex of four and eleven vessel rat occlusion models

Interstitial levels of the neurotransmitter glutamate and cerebral blood flow changes were compared in two models of rat forebrain ischemia using the dialysis electrode technique and laser doppler flowmetry with brain temperature controlled. Ten-minute periods of cerebral ischemia were elicited by the four and an eleven vessel occlusion and compared to carotid artery transection. Elapsed time from the onset of ischemia to the ischemic plateau was 76.8+/-57.9 s in 4VO vs. 14.8+/-1.3 s in 11VO animals. Percent residual cerebral blood flow (CBF) was 13.5+/-8.8% during 4VO as opposed to 4.5+/-2.9% during 11VO. Concomitantly, cerebral glutamate levels rose to 255. 7+/-72.8 micromol l-1 in the 4VO animals in comparison with levels of 138.5+/-78.7 and 135.7+/-40.2 micromol l-1 in the 11VO and carotid transection animals. During the first 89.6+/-47.4 s of reperfusion, glutamate levels rose to a second higher peak of 315. 1+/-179.2 micromol l-1 in 7 of 12 animals. Following reperfusion, glutamate levels in the 4VO and 11VO animals returned towards basal levels. This study demonstrates that 11VO causes a rapid drop in CBF to near zero levels, better mimicking complete forebrain ischemia than the traditional 4VO technique. Moreover, the 'low flow' state of cerebral ischemia, produced by traditional 4VO, results in a higher interstitial level of glutamate than a 'no flow' state, as exhibited by the 11VO technique. The dialysis electrode, used simultaneously with laser doppler flowmetry, real-time data acquisition, and continuous brain temperature control, in this new rat model, provides real-time evidence that glutamate levels in the interstitial space are enhanced during a low flow state of cerebral ischemia. Furthermore, not before demonstrated, glutamate transients are seen to occur during the first 90 s of reperfusion, and, to the best of our knowledge, the glutamate levels recorded by this technique are the highest in the literature.

Microsurgical anatomy of the suboccipital segment of the vertebral artery

The craniocervical regions of seven cadavers (14 sides) injected with silicone rubber were dissected under a Zeiss OPMI surgical microscope. The present study provides a detailed description of the suboccipital segment of the vertebral artery, with particular attention to its loops, branches, supporting osteofibrous structures, adjacent nerves, and surrounding venous structures. Several ligaments fixating the vertebral artery to surrounding structures, which have not been described in previous anatomical studies, were found. The authors propose an anatomically based subdivision of the suboccipital segment of the vertebral artery into five subsegments: infraforaminal, foraminal, supraforaminal, horizontal, and intramembranous. Measurements of surgically and clinically important features were obtained. Surgical approaches to this region are suggested based on a more informed understanding of the local anatomy.

Microanatomical considerations for the fenestration of the septum pellucidum

The anatomical foundations for the endoscopic fenestration of the septum pellucidum have not been presented previously in an isolated fashion. Using a surgical microscope, the microsurgical anatomy of the septum pellucidum, lateral ventricles, and surrounding structures was examined in ten adult brains injected with silicone rubber. The mean anteroposterior length of the septum pellucidum was 41 mm (range 40-42). Its mean height was 13.11 mm (range 12-15) at the level of the foramen of Monro; 10 mm (range 9-11) at the frontal horns, and 8 mm (range 7-10) at the ventricular atrium. One to three septal veins delimited 2 or 3 avascular areas in the septum pellucidum. We found an anterior area which was consistently avascular and large enough to be fenestrated safety. More posterior areas, while avascular, were inconsistent in their size and shape.

Management of elevated intracranial pressure in patients with Cryptococcal meningitis

BACKGROUND

The most important predictor of early mortality in patients with HIV-associated cryptococcal meningitis is mental status at presentation; patients who present with altered mental status have up to 25% mortality. Historically, cerebrospinal fluid (CSF) diversion in HIV-negative patients with cryptococcal meningitis and signs of elevated intracranial pressure (ICP) has improved survival. In an effort to affect survival and morbidity rates in patients with HIV-associated cryptococcal meningitis, we have initiated aggressive management of elevated ICP in patients with focal neurologic deficits, mental obtundation, or both.

METHODS

We identified 10 patients with HIV-associated cryptococcal meningitis who presented with symptoms consistent with elevated ICP, including headache, mental obtundation, papilledema, and cranial nerve palsies. Elevated opening pressure was defined as > 20 cm CSF during lumbar puncture. In patients with elevated opening pressures who had focal neurologic deficits or mental status changes refractory to serial lumbar puncture, management consisted of immediate placement of lumbar drains for continuous drainage of CSF to maintain normal ICP (10 cm CSF). Patients with persistent elevations of spinal neuraxis pressure following lumbar drainage underwent placement of lumbar peritoneal shunts.

RESULTS

All patients returned to their baseline level of consciousness following normalization of ICP. Two patients were weaned from lumbar drainage. Eight patients eventually required placement of lumbar peritoneal shunts for persistently elevated ICP despite successful antifungal therapy. Follow-up ranged from 1 to 15 months. One shunt infection occurred, one lumbar peritoneal shunt was converted to a ventriculoperitoneal shunt, and one shunt was removed.

CONCLUSIONS

Elevated ICP in patients with HIV-associated cryptococcal meningitis is a significant source of morbidity and mortality. The use of lumbar drainage and selective placement of lumbar peritoneal shunts in the management of elevated ICP in patients with HIV-associated cryptococcal meningitis can ameliorate the sequelae of elevated ICP.

[15O]-water PET and intraoperative brain mapping: a comparison in the localization of eloquent cortex

[15O]-water PET was performed on 12 patients with structural lesions for localization of the motor (n = 5), language (receptive and expressive; n = 6), and visual cortex (n = 1). All these patients underwent interactive image-guided surgery using an infrared digitizer and intraoperative electrical stimulation mapping for motor, sensory, language, and visual cortex location. MRI-PET coregistration was performed using a surface matching approach that integrated functional information with interactive image guidance during the surgical procedure. An awake craniotomy with motor and sensory intraoperative stimulation was performed using a registered bipolar electrode that was tracked on real-time during the surgical procedure. Intraoperative functional findings were displayed and saved on the registered MRI images. The sites of functional PET activation during the performance of motor, visual and language tasks were then compared to the results of intraoperative cortical stimulation in 11 patients and visual evoked potentials in one. The results of the PET activation studies were concordant with the findings of intraoperative stimulation in all cases. During resection of the structural lesions, intraoperative stimulation was continued in the subcortical pathways, and five patients had positive responses on areas not identified by the functional PET. Furthermore, 3 patients showed transitory changes in function (speech arrest 1, naming difficulty 1, and motor weakness 1) that were reversible after changing the dissection technique or a brain retractor. [15O]-water PET was reliable in identifying the motor, visual, and language cortex. Language-related rCBF increases were highly distributive, although only part of these activations were subjected to intraoperative stimulation. We conclude that [15O]-water PET can be used for preoperative noninvasive identification of functional cortex and may be useful in neurosurgical preplanning. Intraoperative mapping still remains the main means to avoid neurological damage as it can be performed during the entire surgical procedure to avoid damage to cortex, pathways, and damage secondary to ischemia or edema (brain retraction).

Use of an open stereotactic ring for neurosurgical procedures

We describe an open ring as a new design to the Zamorano-Dujovny (Z-D) stereotactic unit. The titanium base ring has an opening of 45 degrees that can be located in any chosen position. Imaging studies such as computed tomography, X-ray, positron emission tomography, digital angiography, and digital substraction angiography can be performed with the open stereotactic ring for multimodality image localization. Preoperatively and intraoperatively, this open design provides the anesthesiologist with an unobstructed pathway for airway management. During the surgical procedure, it facilitates approach to any intracranial lesion, including orbitozygomatic, combined supra-infratentorial, and others. During awake craniotomies it not only allows for easy airway management, but also provides good access to the patient's face for intraoperative evaluation of speech and visual functions. Accuracy and reliability of this unit were similar to results obtained with the original circular ring. This system can be used in conventional stereotaxis with the Z-D arc, as well as a reference for intraoperative registration with any digitizer system. The open stereotactic unit is a relatively inexpensive, reliable, and easy-to-use solution for resections using conventional stereotaxis or interactive image guidance in any intracranial site.