Cell-Mediated Delivery of Brain-Derived Neurotrophic Factor Enhances Dopamine Levels in an Mpp+ Rat Model of Substantia Nigra Degeneration

Brain-derived neurotrophic factor (BDNF) promotes the survival of fetal mesencephalic dopaminergic cells and protects dopaminergic neurons against the toxicity of MPP+ in vitro. Supranigral implantation of fibroblasts genetically engineered to secrete BDNF attenuates the loss of substantia nigra pars compacta (SNc) dopaminergic neurons associated with striatal infusion of MPP+ in the adult rat. Using this MPP+ rat model of nigral degeneration, we evaluated the neurochemical effects of supranigral, cell-mediated delivery of BDNF on substantia nigra (SN) dopamine (DA) content and turnover. Genetically engineered BDNF-secreting fibroblasts (~12 ng BDNF/24 h) were implanted dorsal to the SN 7 days prior to striatal MPP+ administration. The present results demonstrate that BDNF-secreting fibroblasts, as compared to control fibroblasts, enhance SN DA levels ipsilateral as well as contralateral to the graft without altering DA turnover. This augmentation of DA levels suggests that local neurotrophic factor delivery by genetically engineered cells may provide a therapeutic strategy for preventing neuronal death or enhancing neuronal function in neurodegenerative diseases characterized by dopaminergic neuronal dysfunction, such as Parkinson's disease.

Estimation of in vivo human brain-to-skull conductivity ratio from simultaneous extra- and intra-cranial electrical potential recordings

OBJECTIVE

The present study aims to accurately estimate the in vivo brain-to-skull conductivity ratio by means of cortical imaging technique. Simultaneous extra- and intra-cranial potential recordings induced by subdural current stimulation were analyzed to get the estimation.

METHODS

The effective brain-to-skull conductivity ratio was estimated in vivo for 5 epilepsy patients. The estimation was performed using multi-channel simultaneously recorded scalp and cortical electrical potentials during subdural electrical stimulation. The cortical imaging technique was used to compute the inverse cortical potential distribution from the scalp recorded potentials using a 3-shell head volume conductor model. The brain-to-skull conductivity ratio, which leads to the most consistent cortical potential estimates with respect to the direct intra-cranial measurements, is considered to be the effective brain-to-skull conductivity ratio.

RESULTS

The present estimation provided consistent results in 5 human subjects studied. The in vivo effective brain-to-skull conductivity ratio ranged from 18 to 34 in the 5 epilepsy patients.

CONCLUSIONS

The effective brain-to-skull conductivity ratio can be estimated from simultaneous intra- and extra-cranial potential recordings and the averaged value/standard deviation is 25+/-7.

SIGNIFICANCE

The present results provide important experimental data on the brain-to-skull conductivity ratio, which is of significance for accurate brain source localization using piece-wise homogeneous head models.

High-resolution EEG: cortical potential imaging of interictal spikes

BACKGROUND

It is of clinical importance to localize pathologic brain tissue in epilepsy. Noninvasive localization of cortical areas associated with interictal epileptiform spikes may provide important information to facilitate presurgical planning for intractable epilepsy patients.

METHODS

A cortical potential imaging (CPI) technique was used to deconvolve the smeared scalp potentials into the cortical potentials. A 3-spheres inhomogeneous head model was used to approximately represent the head volume conductor. Five pediatric epilepsy patients were studied. The estimated cortical potential distributions of interictal spikes were compared with the subsequent surgical resections of these same patients.

RESULTS

The areas of negativity in the reconstructed cortical potentials of interictal spikes in 5 patients were consistent with the areas of surgical resections for these patients.

CONCLUSIONS

The CPI technique may become a useful alternative for noninvasive mapping of cortical regions displaying epileptiform activity from scalp electroencephalogram recordings.

A single-incision laparoscopic technique for retrieval and replacement of disconnected ventriculoperitoneal shunt tubing found in the peritoneum

A 7-year-old girl presented with signs and symptoms of increased intracranial pressure 2 years after insertion of a ventriculoperitoneal (VP) shunt. Evaluation revealed disconnection of the distal shunt catheter and migration into the peritoneal cavity. A single-incision laparoscopic procedure was performed to locate and remove the disconnected shunt tubing, and the new shunt catheter was inserted through the laparoscopic port site. Laparoscopy is being used more frequently for evaluation and repair of distal VP shunt malfunctions, but generally still requires multiple incisions for port placement and insertion of the new shunt catheter. The single-incision technique used here is technically feasible, allows excellent visualization of the peritoneal cavity and does not require any incisions beyond the previous one used for initial shunt insertion.

Measurements of intraventricular pressure in a patient shunted from the ventricle to the internal jugular vein against the direction of blood flow (the El-Shafei shunt)

OBJECT

After demonstrating the anti-siphoning properties of a distensible tube in vitro, El-Shafei constructed a shunting system that directs CSF flow into the internal jugular vein against the flow of blood. Though clinically effective, the in vivo pressure dynamics of this type of shunt system have not been investigated.

METHODS

After failure at multiple other extracranial absorptive sites, an 18-year-old woman was shunted from the lateral ventricle to the internal jugular vein against the direction of blood flow. The shunt system contained an in-line noninvasive telemonitor allowing examination of postural intracranial pressure dynamics in the awake state. This shunt system demonstrated postural pressure dynamics that were consistent with a stringent nonsiphoning shunting system.

CONCLUSIONS

These observations validate the use of the El-Shafei shunt placement as a biologically nonsiphoning CSF absorptive system. In addition, the stringency of the anti-siphoning properties of the internal jugular vein open the possibility of preferentially using this shunting system in patients who clearly exhibit symptoms of shunt overdrainage.

Intraventricular pressure dynamics in ventriculocholecystic shunting: a telemetric study

Extracranial cerebrospinal fluid shunting is the current mainstay of therapy for hydrocephalus. The generally preferred extracranial site for cerebrospinal fluid absorption is the peritoneal space; however, the cardiac atrium and the pleura are also commonly used. On occasion other CSF recipient sites, such as the gallbladder, are used secondarily when the more common absorptive spaces are unavailable or unsuitable. The gallbladder, though, exhibits its own pressure dynamics in response to physiological stimuli. The effects of gallbladder contraction on intraventricular pressure (IVP) in the presence of a ventriculocholecystic (VGB) shunt are unknown. We had the opportunity to place a VGB shunt in a 4-year-old child who was coupled to a noninvasive telemonitor. After a period of acclimation, we examined the IVP dynamics of that shunting system both pre- and postprandially. We found that before ingestion of food, the gallbladder provides a CSF recipient site similar to that of the peritoneal space. However, after ingestion of a meal containing fat, we found that IVP rose more than 10 cm water in a stereotypic fashion consistent with postprandial gallbladder contraction. The increase in IVP lasted for several hours reaching a peak at approximately 75 min postprandially. We conclude that the VGB shunt is a viable alternative for extracranial cerebrospinal fluid shunting; however, one must be aware of the peculiar dynamics of this shunt in relation to food ingestion and the potential for unusually high IVPs.

Telemetric assessment of intracranial pressure changes consequent to manipulations of the Codman-Medos programmable shunt valve

INTRODUCTION

Noninvasive manipulation of programmable shunt valves may allow customization of intracranial pressure (ICP) dynamics in individual shunted patients. Manipulations of the recently FDA-approved Codman-Medos variable pressure valve (VPV) are monitored by radiographic changes in the valve mechanism, necessitating a skull radiograph with each pressure change. We wished to assess the in vivo impact of VPV manipulations on ICP changes using a noninvasive telemonitor as an alternative to radiographic confirmation and as a method for validating the ICP changes.

METHODS

TeleSensor devices (Radionics) were implanted in-line with 12 VPV shunt systems. ICP was assessed telemetrically in the supine position whenever the valve pressure was adjusted (both before and 2-5 min after the manipulation).

RESULTS

Valve manipulation was confirmed by radiograph for the initial manipulations only and matched the telemetric pressure changes observed in all cases. Confirmed manipulations of the valve were generally followed by a near equivalent relative change in ICP (</=2 cm difference 74% of the time); however, the absolute value of the supine ICP was dependent on the entire shunting system and was equivalent to the valve setting only 11% of the time. Supine ICP and ICP dynamics were also dependent more on the shunt system than simply on the valve setting and were different for each of the shunt systems tested.

CONCLUSIONS

We have confirmed that the VPV does cause ICP changes in shunted hydrocephalic patients that are essentially equivalent to programmed relative changes in the valve settings. These changes can be as easily monitored by noninvasive telemetry as by repeated radiography. However, our observations demonstrate that additional factors in the shunting system render the ICP absolutely equivalent to the VPV setting only rarely, implying that a programmable shunt valve is not necessarily equivalent to programmable ICP.

A theoretical model of benign external hydrocephalus that predicts a predisposition towards extra-axial hemorrhage after minor head trauma

INTRODUCTION

There is controversy over whether there exists a predisposition towards bleeding into the subdural space in infants with benign external hydrocephalus (BEH) or other enlargement of the extra-axial space (e.g. subdural hygroma). The presumed etiology implicates shear forces in over-stretching the extra-axial blood vessels. We have created a model of the intracranial space that approximates certain aspects of BEH. Using this model, we predict situations where children with BEH will bleed into the extra-axial space when normal infants will not.

METHODS

The cranial model consists of two spheres representing the brain and the skull. The distance between them represents the width of the extra-axial space. The spheres are concentric (with interspheric distance equal to N) in the normal condition and nonconcentric in BEH. In BEH, the distance between the two spheres varies from N to Q (0 < N </= Q) over a 906 M </= Q, with the translation orthogonal to the vector of N and parallel to that of M or vice versa), then the final length V(f) of a vein V is V(f) = (N(2) + M)(1/2), and the stretch ratio V(f)/V(i) is: V(f)/V(i) = (N(2) + M(2))(1/2)/N.S(i), with S(i) the slack factor, where i represents either n for normal or b for BEH and M = N in the normal condition.

RESULTS

Given an equivalent capacity of veins to resist stretch injury (based on the proportion of change in length), for brain translations after a low-impact head injury, stretch ratios for BEH veins range from 1.677 to 3.436, whereas in the normal condition they range from 1.061 to 1.179. Therefore, for an increase in subarachnoid space from 3 (normal) to 6 mm (BEH), brain translocation in BEH will stretch veins beyond an average breaking point when the translation for the normal condition will not.

CONCLUSIONS

Mathematical modeling of the cranial vault produces a relationship between venous stretch and the width of the extra-axial space. These equations predict an increased frequency of venous stretch injury in the situation of widened extra-axial space. Such venous injury is consistent with forces generated by minor trauma. This relationship, as predicted by our model, could underlie a predisposition towards extra-axial bleeding after minor head trauma in infants with BEH.

The selective toxicity of 1-methyl-4-phenylpyridinium to dopaminergic neurons: the role of mitochondrial complex I and reactive oxygen species revisited

1-Methyl-4-phenylpyridinium (MPP(+)) is selectively toxic to dopaminergic neurons and has been studied extensively as an etiologic model of Parkinson's disease (PD) because mitochondrial dysfunction is implicated in both MPP(+) toxicity and the pathogenesis of PD. MPP(+) can inhibit mitochondrial complex I activity, and its toxicity has been attributed to the subsequent mitochondrial depolarization and generation of reactive oxygen species. However, MPP(+) toxicity has also been noted to be greater than predicted by its effect on complex I inhibition or reactive oxygen species generation. Therefore, we examined the effects of MPP(+) on survival, mitochondrial membrane potential (DeltaPsim), and superoxide and reduced glutathione levels in individual dopaminergic and nondopaminergic mesencephalic neurons. MPP(+) (5 microM) selectively induced death in fetal rat dopaminergic neurons and caused a small decrease in their DeltaPsim. In contrast, the specific complex I inhibitor rotenone, at a dose (20 nM) that was less toxic than MPP(+) to dopaminergic neurons, depolarized DeltaPsim to a greater extent than MPP(+). In addition, neither rotenone nor MPP(+) increased superoxide in dopaminergic neurons, and MPP(+) failed to alter levels of reduced glutathione. Therefore, we conclude that increased superoxide and loss of DeltaPsim may not represent primary events in MPP(+) toxicity, and complex I inhibition alone is not sufficient to explain the selective toxicity of MPP(+) to dopaminergic neurons. Clarifying the effects of MPP(+) on energy metabolism may provide insight into the mechanism of dopaminergic neuronal degeneration in PD.

In vivo intracranial pressure dynamics in patients with hydrocephalus treated by shunt placement

OBJECT

With the commercial availability of a variety of shunt systems, there is considerable controversy over the choice of the most appropriate shunt valve for each individual with hydrocephalus. Although the performance characteristics of all shunt systems are well documented in the laboratory setting, there is little description of the in vivo dynamics of intracranial pressure (ICP) after implantation of commonly used shunt systems in humans. The authors coupled telemonitoring devices to several different shunt systems to measure the performance characteristics of these valve systems with respect to intraventricular pressure (IVP) at increments of head elevation.

METHODS

Twenty-five patients with different shunt systems and three control patients without shunts were studied for IVP at 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees of head elevation, and the resultant curves were analyzed for the best-fit regression coefficient. For purposes of analysis the authors grouped shunt valve systems by design characteristics into three groups: differential-pressure valves (r = -0.321 +/- 0.061; 11 patients), nonsiphoning systems (r = -0.158 +/- 0.027; 10 patients), and flow-regulated valves (r = -0.16 +/- 0.056; four patients); there were three control patients without shunts (r = -0.112 +/- 0.037).

CONCLUSIONS

The authors found that differential-pressure valves always caused ICP to drop to 0 by 30 degrees of head elevation, whereas all other valve systems caused a more gradual drop in ICP, more consistent with pressures observed in the control patients without shunts. Not surprisingly, the differential-pressure valve group was found to have a significant difference in mean regression coefficient when compared with those in whom nonsiphoning shunts (p < 0.023) or no shunts were placed (p < 0.049). These data provide a basis for evaluating shunt valve performance and for predicting valve appropriateness in patients in whom characteristics such as pressure and flow dynamics are weighed in the choice of a specific valve for implantation.

A child with neurofibromatosis-1 and a lumbar epidural arteriovenous malformation

A 10-year-old child with neurofibromatosis-1 was evaluated for progressive lumbar scoliosis, back pain, and foot numbness. Magnetic resonance imaging showed several lumbar intraspinal and extraspinal masses consistent with neurofibromas. The mass at L3-L5 compressed the thecal sac and was thought to be the source of the symptoms. On operative exploration, a lumbar epidural arteriovenous malformation was found, which was removed in its entirety. The child's back pain and foot numbness resolved. Epidural arteriovenous malformations in patients with neurofibromatosis-1 are rare and have been reported only in the cervical spine. Our finding of a lumbar epidural arteriovenous malformation in a child with neurofibromatosis-1 demonstrates that vascular anomalies can be present throughout the spine of patients with neurofibromatosis-1 and should be considered in the differential diagnosis of any neurofibromatosis-1-related epidural mass.

Delayed repair of open depressed skull fracture

INTRODUCTION

Elevation and repair of an open depressed skull fracture is often thought of as an emergency procedure. Common indications for emergent elevation of a depressed skull fracture have been dural tear, seizure, gross contamination or mass effect from bone or a sizable underlying intracerebral hematoma. As treatment of head injury moves towards management of cerebral perfusion pressure (CPP) rather than intracranial pressure (ICP), we sought a way to maximize CPP in the initial treatment of head-injured patients with depressed skull fractures that would eventually require surgery by delaying surgery, when possible, until after the initial period of elevated ICP.

METHODS

Over a 12-month period, 7 patients (all male, ages 1-15 years) were admitted to our institution with the diagnosis of open depressed skull fracture without significant mass effect requiring urgent decompression. All had significant head trauma with altered mental status and a Glasgow Coma Score of 3-12. Patients were treated with antibiotic prophylaxis (nafcillin, ceftriaxone, metronidazole), seizure prophylaxis (phenytoin) and underwent CPP management in an intensive care unit setting as indicated by intracranial pressure monitoring or clinical assessment. Length of medical management of CPP ranged from 4 to 12 days. Upon stabilization of CPP, patients were operated for repair of their dural, bone and scalp injuries.

RESULTS

All 7 patients treated in the above manner suffered no ill effects from their delayed surgery: there was no meningitis, no late seizures, and no cerebrospinal fluid leak. Complications attributable to delay were not present at follow-up ranging from 12 to 24 months.

CONCLUSIONS

We have delayed surgery for repair of open depressed skull fractures in order to maximize medical management of CPP in the setting of acute trauma. Among other considerations, the risk of intraoperative hypotension occurring at a time of acutely raised ICP was avoided by this delay. We conclude that there is a role, in this specifically defined subset of head trauma patients, for delayed surgical repair of open depressed skull fractures.

Endoscopic approach to noncommunicating fluid spaces in the shunted patient

INTRODUCTION

It is well known that shunted hydrocephalic patients can, over time, develop entrapped ventricles or cystic spaces not in communication with the remaining ventricles. This situation has traditionally been treated with placement of an additional catheter or shunt system in the noncommunicating fluid space. With the advent of minimally invasive endoscopic techniques, it has become possible to fenestrate trapped fluid spaces into the shunted ventricular system, thus preventing the need for additional catheters.

METHODS

Fifteen shunted patients presented with noncommunicating fluid spaces over a 4-year period at our two institutions. We attempted fenestration procedures in 14 of those patients. The various procedures included: septum pellucidum fenestration, cyst fenestration, third ventriculocisternostomy and a combination of the above.

RESULTS

Thirteen of 16 (81%) endoscopic fenestrations successfully prevented the need for a complicated shunting system. There were 3 technical failures (3/16, 19%) in which an additional catheter was added to the existing shunt system at the time of the endoscopic procedure. There were no adverse neurologic effects from the endoscopic procedures; however, in 4 of the 14 patients (29%) a shunt revision was performed between 2 and 30 days following the fenestration.

CONCLUSIONS

These results show that the endoscopic approach to establishing communication between noncommunicating CSF spaces in the shunted patient is safe and efficacious in preventing the need for additional CSF catheters. Though we encountered failures, the majority of cases are technically feasible. In these patients early shunt malfunction may occur, most likely due to intraoperative bleeding and will require shunt revision.

Management of cavernous malformations in the pediatric population

The management of cavernous malformations (CMs) in a child is similar in many ways to that of CMs in an adult. There are specific general principles that need to be considered when approaching these lesions in children, however. The long life span anticipated in the pediatric patient may favor an aggressive surgical approach for single, small asymptomatic cavernous malformations or for certain symptomatic lesions in eloquent locations. The observed history of a given malformation may be the best guide to determine its treatment. The authors discuss some of these principles and review their experience with a series of children who have presented for management of cerebral CM.

C2/3 instability in a child with Down's syndrome . case report and discussion

Down's syndrome patients are prone to cervical ligamentous laxity, the vast majority of which is at the C1/2 level. We describe the case of a 2-year-old girl with Down's syndrome who was found to have cervical instability at the C2/3 level on screening cervical spine radiographs with 9 mm of anterolisthesis of C2 on C3. She was without clinically evident neurological deficit from this condition; however, T2-weighted magnetic resonance imaging of her cervical spine revealed high intensity signal changes within the spinal cord at and above that level. She underwent posterior fusion that was complicated by poor tolerance of her Minerva-type cervical brace. She eventually developed a stable fusion with 5 mm of anterolisthesis at the C2/3 level. This is the only Down's syndrome patient with instability at the C2/3 level that we have found reported. Our experience suggests that Down's syndrome patients can have instability at C2/3 that can be successfully treated with posterior fusion.

Intraventricular pressure dynamics in patients with ventriculopleural shunts: a telemetric study

Extracranial CSF shunting to the pleural absorptive surface is sometimes used as an alternative to ventriculoperitoneal shunting. The pressure dynamics of this type of shunt would be expected to differ from peritoneal shunting due to active changes in pleural pressures caused by the ventilatory cycle. We have had opportunity to examine the in vivo intraventricular pressure (IVP) dynamics of ventriculopleural shunts utilizing a commercially available implantable telemonitor (Telesensor; Radionics, Burlington, Mass.). Four patients with ventriculopleural shunts were monitored telemetrically while supine and at increments of head elevation to 90 degrees. Two patients with 'medium' grade differential pressure valves exhibited IVPs which were never greater than zero. One patient with an in-line antisiphoning device in the shunt system appeared to have IVPs closely resembling those seen in shunting to the peritoneal space. Another patient with valve opening pressure set at 19 cm of water consistently had supine intraventricular pressures less than 10 cm of water that readily fell to zero with minimal head elevation. We conclude that the negative intrapleural pressures generated by the ventilatory cycle tend to cause IVPs in ventriculopleural shunts to be lower than those expected in peritoneal shunting. This observation suggests that ventriculopleural shunts may be appropriate for patients requiring very low intraventricular pressures in order to resolve their hydrocephalic symptoms.

Surgical management of neonatal hydrocephalus

Maintenance of normal intracranial pressure is crucial to the development of the neonatal brain. Certainly, neonatal hydrocephalus will perturb cerebral development and calls for careful and timely intervention. Many competing factors must be taken into account when evaluating the neonate with hydrocephalus. A neurosurgical approach to the management of neonatal hydrocephalus is presented with emphasis on practical treatment paradigms.

Telemetric intraventricular pressure measurements after third ventriculocisternostomy in a patient with noncommunicating hydrocephalus

OBJECTIVE

To examine and document intraventricular pressure (IVP) dynamics in an adult after endoscopic third ventriculocisternostomy performed as treatment for hydrocephalus associated with aqueductal stenosis.

METHODS

A 30-year-old man who had undergone ventriculoperitoneal shunting at age 21 years for aqueductal stenosis caused by a tectal mass presented with symptoms and imaging studies consistent with shunt malfunction. He underwent urgent ventriculoscopic third ventricular ventriculocisternostomy, which resolved his symptomatology. The existing shunt was not revised. At the time of surgery, a catheter connected to an intracranial pressure TeleSensor device (Radionics, Burlington, MA) was inserted into the ventricular system. Postoperatively, the patient's recovery was assessed by IVP recordings. This system allowed us to record IVP in an awake patient with a functioning third ventriculocisternostomy.

RESULTS

We observed an initial postoperative IVP of 17 cm H2O in the supine position, which decreased to 0 cm H2O at 90 degrees of head elevation. The IVP decreased during the first 48 hours postoperatively to 0 to 2 cm H2O when supine. By 1 week postoperatively, the patient's IVP had returned to a baseline of 15 to 17 cm H2O when supine, with a gradual decrease to 0 cm H2O at 30 degrees of head elevation. Three months postoperatively, the patient's IVP in the supine position was 8 cm H2O, with IVP decreasing to 0 cm H2O at 45 degrees of head elevation. Magnetic resonance (MR) imaging performed at that time revealed evidence of flow through the third ventriculocisternostomy.

CONCLUSION

We conclude that after an initial period of adjustment, the IVP in this patient returned to an unremarkable baseline despite the novel fluid pathway into the prepontine cistern. This may represent maturation of the breach through the third ventricular floor or brain recovery from a period of high pressure. Also, the shape of the postural IVP curve closely resembled that observed in patients who are not hydrocephalic. These data represent the first documentation of the intraventricular pressure response to ventriculocisternostomy and suggest possible intracerebral responses to this alteration in cerebrospinal fluid flow.

The use of clinical practice guidelines (CPGs) to evaluate practice and control costs in ventriculoperitoneal shunt management

BACKGROUND

As a step toward maximizing the quality and cost-effectiveness of neurosurgical care, we designed clinical practice guidelines (CPGs) for the management of VP shunt malfunctions and infections at a tertiary care pediatric teaching institution. The detailed CPGs determine the use of radiographic studies, laboratory tests, and invasive procedures in the management of this problem. One purpose of the CPGs is to provide clear clinical guidelines for the medical trainee, thereby reducing variability in care and unnecessary utilization of resources.

METHODS

The CPGs were developed in stages over a 2-year period. The practice patterns in our institution for the management of shunt malfunctions and infections were articulated. They were compared with those published in the neurosurgical literature, and areas of clinical decision-making variability were identified. Preliminary guidelines were formulated, and data regarding patient care were prospectively collected. Based on this data, final CPGs were formulated and implemented. Total and itemized hospital charges for patients managed according to the CPGs were compared with those for patients in the 3 years before CPG implementation.

RESULTS

CPG-managed patients had generally lower total and itemized charges as compared with control patients. Decreased charges per hospital day and charges for shunt films in the CPG group were statistically significant.

CONCLUSIONS

The process by which the CPGs were developed and implemented, as well as the CPGs themselves, are described. We also present the clinical, demographic, and financial data that were prospectively collected for all patients managed within the CPGs over an initial 1-year period and compare it with data obtained for control groups of shunt malfunction patients admitted during the 3 years before implementation of the CPGs. We find a trend toward reduction of charges after implementation of the CPG.

Treatment of hydrocephalus with third ventriculocisternostomy: outcome and CSF flow patterns

Third ventriculocisternostomy was performed in 23 patients for management of hydrocephalus. The procedure was offered as the first treatment in 18 cases and in lieu of a shunt revision in 4 cases. Median follow-up was 17 months (range 7-44 months). In 16 patients the operation was successful in treating their symptoms (73%). Cine MRI was helpful in evaluating patients with persistent ventriculomegaly. Resolution of symptoms in association with decreased ventricular size correlated best with outcome following this procedure. Third ventriculocisternostomy is technically safe and minimally invasive and should be offered as the first procedure in the management of noncommunicating hydrocephalus.

Surgery of the spine in myelodysplasia. An overview

Significant spinal deformity is particularly common in nonambulatory patients with myelodysplasia. Progressive deformity may be caused by congenital anomalies, paralytic collapse, hip contractures, or spinal cord tethering. Existing or projected functional impairment should be the principle indication for treatment. Surgical treatment is complicated by poor soft tissue coverage, associated contractures, lack of sensation, weak bone, and absence of posterior elements. Successful fusion can be achieved by circumferential (anterior and posterior) fusion and current rigid segmental instrumentation. The unique deformities and bony anatomy require individualized techniques to achieve fixation.

Hydrocephalus requiring urgent external ventricular drainage in a patient with diabetic ketoacidosis and cerebral edema: case report

OBJECTIVE AND IMPORTANCE

Neurological deterioration, typically attributed to cerebral edema, is a rare but life-threatening complication in the treatment of diabetic ketoacidosis (DKA). We report the case of a child with DKA who became comatose but demonstrated acute obstructive hydrocephalus, instead of cerebral edema.

CLINICAL PRESENTATION

An 11-year-old male patient presented with new-onset insulin-dependent diabetes mellitus and DKA. He was initially responsive but, after several hours of treatment, became unresponsive, with dilated pupils and decerebrate posturing. Cranial computed tomographic scanning demonstrated obstructive hydrocephalus resulting from focal cerebellar and brain stem edema.

INTERVENTION

The patient was initially managed with medical treatment but ultimately required urgent ventricular drainage to arrest a progressive herniation syndrome. To our knowledge, this report describes only the second such case reported and the first requiring urgent ventriculostomy.

CONCLUSIONS

These observations emphasize the importance of recognizing hydrocephalus as a potentially reversible cause of coma in DKA and of initiating prompt neurosurgical intervention, if warranted.

Acute pulmonary edema after low-level air embolism during craniotomy. Case report

Acute pulmonary edema after a large air embolus occurring during neurosurgery is a recognized phenomenon. The authors describe the course of a 76-year-old man who presented with noncardiogenic pulmonary edema shortly after undergoing resection of a high convexity meningioma. Transthoracic Doppler sonography, however, showed no evidence of a large intraoperative emboli; the evidence for ongoing but low-magnitude air embolus included visualization of bone aspiration of irrigant before bone-edge waxing, transient intraoperative declines in end-tidal CO2 tension, and an increase of the fraction of inspired oxygen to maintain adequate saturation after removal of the craniotomy flap. There was no hemodynamic instability noted. The airspace disease was self-limited and resolved on supportive treatment after approximately 1 week, as would be expected for pulmonary edema caused by a single large intravenous air embolus. The authors present this case as the first report of pulmonary edema resulting from low-level air embolus occurring during craniotomy. This situation may go unrecognized intraoperatively but can cause the same significant postoperative morbidity as larger, more easily identified air emboli.

Immunohistochemically identifiable tissue plasminogen activator in cavernous angioma: mechanism for re-hemorrhage and lesion growth

The mechanisms governing growth of cavernous angiomas of the brain and their propensity to hemorrhage remain unknown. Repetitive hemorrhage with neovascularization during clot organization and maturation of new vessels into a larger cavernous angioma has been hypothesized as one mechanism. This hypothesis is largely based on the histopathological similarity between the organizing clot surrounding cavernous malformations and the organizing phase of the membranes surrounding chronic subdural hematoma. The presence of tissue plasminogen activator (TPA) in the vascular endothelium of vessels contained within chronic subdural membranes has been used to argue that an intrinsic thrombolytic process is responsible, in part, for rebleeding within chronic subdural cavities. By analogy, we sought to identify whether TPA is located in tissues in and around cavernous angiomas. Cavernous malformations, surgically removed and pathologically confirmed by standard staining techniques, were immunohistochemically stained for TPA. Eleven of thirteen lesions (85%) studied contained vascular endothelial cells which stained for TPA. Of the 2 lesions which did not contain TPA, 1 was non-hemorrhagic and calcified; 7 of 11 (64%) lesions which contained TPA presented clinically with hemorrhage. These data support the hypothesis that a local thrombolytic process may be responsible for the frequent hemorrhagic nature of cavernous angiomas. Alternatively, since local elaboration of TPA is common to both chronic subdural membranes and cavernous angiomas, this finding may represent a more global characteristic of fibrinolytic homeostasis in cerebral tissues.

Cell-mediated delivery of brain-derived neurotrophic factor enhances dopamine levels in an MPP+ rat model of substantia nigra degeneration

Brain-derived neurotrophic factor (BDNF) promotes the survival of fetal mesencephalic dopaminergic cells and protects dopaminergic neurons against the toxicity of MPP+ in vitro. Supranigral implantation of fibroblasts genetically engineered to secrete BDNF attenuates the loss of substantia nigra pars compacta (SNc) dopaminergic neurons associated with striatal infusion of MPP+ in the adult rat. Using this MPP+ rat model of nigral degeneration, we evaluated the neurochemical effects of supranigral, cell-mediated delivery of BDNF on substantia nigra (SN) dopamine (DA) content and turnover. Genetically engineered BDNF-secreting fibroblasts (approximately 12 ng BDNF/24 h) were implanted dorsal to the SN 7 days prior to striatal MPP+ administration. The present results demonstrate that BDNF-secreting fibroblasts, as compared to control fibroblasts, enhance SN DA levels ipsilateral as well as contralateral to the graft without altering DA turnover. This augmentation of DA levels suggests that local neurotrophic factor delivery by genetically engineered cells may provide a therapeutic strategy for preventing neuronal death or enhancing neuronal function in neurodegenerative diseases characterized by dopaminergic neuronal dysfunction, such as Parkinson's disease.

Mandibular subluxation as an adjunct to exposure of the distal internal carotid artery in endarterectomy surgery. Technical note

The location of the carotid artery bifurcation and the distance atherosclerotic disease extends distally in the internal carotid artery (ICA) are two factors that contribute to the technical difficulty of carotid endarterectomy. When the bifurcation is high (above C-3) or the disease extends distally, standard approaches may not provide adequate exposure for dissection of plaque or for arteriotomy repair. A simple method of mandibular subluxation is described for added exposure of the distal carotid artery. The criteria for use of this method include: a carotid bifurcation at or above C-2; disease extending to within 2 cm of the skull base; and a small-caliber distal ICA lumen with the expectation of a patch graft extending close to the skull base. In dentulous patients, the mandible is subluxed by attaching an intradental wire from the ipsilateral mandibular bicuspid to an intradental wire around the contralateral maxillary bicuspid. In edentulous patients, a wire is placed around the ipsilateral mandible and secured to a wire placed through the anterior nasal spine. The entire preoperative subluxation requires 10 to 15 minutes under anesthesia and an additional 1 to 2 minutes postoperatively to remove the wires. A single skin suture and an absorbable intraoral suture were placed in some edentulous patients. This technique has been evaluated over a 15-month reference period during which 115 carotid endarterectomies were performed. The criteria stated above were met in seven cases (six patients, 6%) and jaw subluxation was performed preoperatively. An additional 1 to 2 cm of distal exposure was obtained by using this technique and endarterectomy proceeded without complication. A slight "shift" of the standard anatomical landmarks occurred due to the movement of the mandible, which was easily recognized. There were no significant postoperative complaints related to the subluxation; specifically, no temporomandibular joint pain, no other postoperative pain, and no tooth damage were encountered. It is concluded that this relatively simple approach to mandibular subluxation provided significant added exposure to the distal ICA without notably increasing operative time. In addition, there was no morbidity and little additional care was needed when compared with other more radical approaches to high carotid artery exposure.

Astrocytes retrovirally transduced with BDNF elicit behavioral improvement in a rat model of Parkinson's disease

Neurotrophic factors that improve the survival of specific neuronal types during development and after exposure to various neuronal insults hold potential for treatment of neurodegenerative diseases. In particular, brain-derived neurotrophic factor (BDNF) has been shown to exert trophic and protective effects on dopaminergic neurons, the cell type known to degenerate in Parkinson's disease. To determine whether increased levels of biologically produced BDNF affect the function or regeneration of damaged dopaminergic neurons, the effects of grafting astrocytes transduced with the human BDNF gene into the striatum of the partially lesioned hemiparkinsonian rat were examined. Replication deficient retroviruses carrying either human prepro-BDNF or human alkaline phosphatase (AP) cDNA were used to transduce primary type 1 astrocytes purified from neonatal rat cortex. In vitro, BDNF mRNA was expressed by BDNF transduced astrocytes (BDNF astrocytes), but not control AP transduced astrocytes (AP astrocytes), as determined by reverse transcription polymerase chain reaction (RT-PCR). The modified astrocytes were injected into the right striatum 15 days after partial lesioning of the right substantia nigra with 6-hydroxydopamine. Transplantation of BDNF astrocytes, but not AP astrocytes, significantly attenuated amphetamine-induced rotation by 45% 32 days after grafting. Apomorphine-induced rotation increased over time in both groups, but was not significantly different in the BDNF-treated group. The modified BDNF astrocytes survived well with non-invasive growth in the brain for up to 42 days. Although BDNF mRNA positive cells were not detected within the graft site using in situ hybridization, alkaline phosphatase immunoreactive (IR) cells were present in control graft sites suggesting that the retroviral construct continued to be expressed at 42 days. Analysis of the density of tyrosine hydroxylase (TH)-IR fibers showed no effect of BDNF on TH-IR fiber density in the striatum on the lesioned side. These findings suggest that ex vivo gene therapy with BDNF ameliorates parkinsonian symptoms through a mechanism(s) other than one involving an effect of BDNF on regeneration or sprouting from dopaminergic neurons.

Symptomatic syringomyelia following surgery to treat retethering of lipomyelomeningoceles

The authors report the cases of three children in whom symptomatic syringomyelia occurred de novo following an operation to relieve retethering of a previously treated lipomyelomeningocele. No patient had a Chiari malformation. In two cases, magnetic resonance imaging performed before the first operation did not show a syrinx. At the time of surgery to relieve retethering, it was discovered that one of these patients had a minor degree of terminal hydromyelia and the other had a prominent central canal within the conus medullaris. The third patient was initially studied by means of myelography, which gave no indication of a syrinx, and one was not found at the time of the surgery to release the retethering. Neurological deficits appeared abruptly within several months of operation in two children, and insidiously after 12 to 18 months in the other symptomatic individual. In all three cases, the syrinx involved the distal spinal cord adjacent to the site of the lipoma. Treatment consisted of syringosubarachnoid shunting, which arrested the progression of deficits but only partially reversed them. The details of each case are presented and the possible mechanism of syrinx formation discussed. Early recognition and treatment of this unusual but important problem are emphasized.

Mutism and cerebellar dysarthria after brain stem surgery: case report

Transient mutism resolving to cerebellar speech after posterior fossa surgery is a well-recognized phenomenon, particularly in pediatric patients. The anatomic basis for this postoperative functional change is unclear but may reside in the dominant superior cerebellar hemisphere or the medial deep cerebellar nuclei. We report a case of an 8-year-old girl who presented for surgical resection of a cavernous malformation of the right pons (at the level of the middle cerebellar peduncle) after hemorrhage. Preoperatively, her complaints consisted of contralateral motor deficits. She had normal speech. Her lesion was resected through a subtemporal approach to the pons. She awoke unable to speak. She was able to communicate through a variety of verbal cues, including sign language. Her mutism lasted 12 days after which she underwent a prolonged period of slowly resolving cerebellar dysarthria. Her preoperative motor deficits also slowly resolved. This is the first reported case of mutism resolving to cerebellar dysarthria after a supratentorial approach to the brain stem. We discuss the anatomic basis for postoperative mutism in light of previous observations combined with the unusual finding of mutism after pontine surgery. In particular, reports of mutism after bilateral cerebellar hemispheric injury, bilateral or unilateral medial deep nuclear injury, and, now, pontine tegmental injury implicate the superior cerebellar hemispheres, the deep cerebellar nuclei, and the nuclear outflow through the superior cerebellar peduncle as the anatomic bases for cerebellar participation in the production of human speech.

Elevation of neuronal MAO-B activity in a transgenic mouse model does not increase sensitivity to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

To examine whether expressing high levels of monoamine oxidase (MAO-B) activity abberently in neurons results in increased sensitivity of dopaminergic neurons to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 8-week-old transgenic mice expressing high neuronal levels of MAO-B were compared with age-matched nontransgenic littermates following i.p. injections of 30 mg/kg body weight of the protoxin. Levels of striatal dopamine (DA) and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC), as well as tyrosine hydroxylase (TH)-immunopositive cell numbers in the substantia nigra (SN) were compared 1 week later between transgenics and controls. No difference was found in any of these parameters, indicating that high neuronal MAO-B levels does not cause increased sensitivity to MPTP, and therefore neither conversion of MPTP to its active form, 1-methyl-4-phenyl pyridium (MPP+) by MAO-B nor MPP+ uptake by the dopaminergic transporter are likely to be the rate-limiting step in the toxicity of this compound.

Implanted NGF-producing fibroblasts induce catalase and modify ATP levels but do not affect glutamate receptor binding or NMDA receptor expression in the rat striatum

Neurotrophic factors, in particular NGF, have been shown to potently protect against glutamate-receptor-mediated toxicity. In order to further investigate the mechanism of this protection, we investigated the in vivo effects of fibroblasts, genetically modified to secrete NGF and implanted near the striatum, on striatal excitatory amino acid binding and receptor expression, on the induction of the peroxidative enzyme catalase, and on cellular energy metabolism in the striatum. Seven days after implantation into the corpus callosum of either a genetically altered NGF-producing (NGF[+]) or unaltered parental (NGF[-]) fibroblast cell-line, there is a time point at which NGF[+] cells have been shown to prevent excitotoxic insults. At that time point after implantation, we found that NGF[+] grafts caused a marked increase in catalase mRNA expression in and around the NGF[+] grafts. The NGF[+] grafts also reduced basal levels of striatal ATP when compared to the effects of NGF[-] grafts. No changes were observed in [3H]glutamate binding and NMDA receptor mRNA expression. We conclude that effects of NGF[+] fibroblast grafts on glutamate receptor mediated toxicity are not by direct effects on glutamate receptors or glutamate binding, but rather appear to be a process involving enzymatic induction and modification of cellular energy stores. The observed increase in catalase mRNA suggests that peroxidative metabolism may be involved in these NGF-mediated effects.

Retinal ganglion cell survival is promoted by genetically modified astrocytes designed to secrete brain-derived neurotrophic factor (BDNF)

Genetically engineered cells carrying genes for neurotrophic factors have potential application for treatment of neurodegenerative diseases and injuries to the nervous system. Brain-derived neurotrophic factor (BDNF) promotes the survival of specific neurons, including retinal ganglion cells (RGC). To determine whether genetically engineered astrocytes might be used for delivering bioactive BDNF, we infected primary type 1 rat astrocytes with a retrovirus harboring a human prepro-BDNF cDNA and assayed the medium conditioned by these astrocytes for effects on survival of rat RGCs in vitro. High levels of BDNF mRNA were expressed by infected astrocytes, but not by control astrocytes as determined by RNase protection assay using a BDNF specific probe. To test for secretion of bioactive BDNF from the transgenic astrocytes, embryonic day 17 rat retinas were dissociated and grown in medium conditioned (CM) for 24 h by astrocytes infected with a replication deficient retrovirus carrying BDNF, NGF, or alkaline phosphatase (AP) cDNA. After 3 days, the number of Thy-1 immunoreactive RGCs was counted. BDNF astrocyte CM significantly enhanced RGC survival by 15-fold compared to the AP control. NGF astrocyte CM had no significant effect. The rate of BDNF secretion was estimated at 83-166 pg/10(5) cells/h. This study demonstrates that astrocytes can be genetically engineered to synthesize and secrete bioactive BDNF. These techniques may be applicable to rescuing neurons from degenerative processes and also for enhancing their survival following transplantation.

Implanted fibroblasts genetically engineered to produce brain-derived neurotrophic factor prevent 1-methyl-4-phenylpyridinium toxicity to dopaminergic neurons in the rat

The trophism of brain-derived neurotrophic factor (BDNF) for dopaminergic cells in culture has led to significant interest in the role of BDNF in the etiology and potential treatment of Parkinson disease. Previous in vivo investigation of BDNF delivery to axotomized substantia nigra dopaminergic neurons in the adult rat has shown no protective effect. In this study, we produced nigral degeneration by infusing 1-methyl-4-phenylpyridinium (MPP+), a mitochondrial complex I inhibitor and the active metabolite of 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP), into the rat striatum. The subsequent loss of nigral neurons was presumably due to mitochondrial toxicity after MPP+ uptake and retrograde transport to the substantia nigra. We engineered immortalized rat fibroblasts to secrete human BDNF and implanted these cells near the substantia nigra 7 days before striatal MPP+ infusion. We found that BDNF-secreting fibroblasts markedly increased nigral dopaminergic neuronal survival when compared to control fibroblast implants. The observation that BDNF prevents MPTP-induced dopaminergic neuronal degeneration in the adult brain has significance for the treatment of neurodegenerative disorders, which may involve mitochondrial dysfunction, such as Parkinson disease.

The effects of megadose methylprednisolone and U-78517F on toxicity mediated by glutamate receptors in the rat neostriatum

Mechanisms of neuronal death after acute insults are unknown but may involve energy depletion and resultant glutamate toxicity. One potential pathway leading to cell death is the formation of oxygen free radicals in an energy-depleted state. Megadoses of glucocorticoids as well as the lazaroid compounds (e.g., 21-aminosteroids and 2-methylaminochromans) have been shown to be potent antioxidants, capable of mitigating the effects of oxygen radicals on lipid membranes in vitro. The authors investigated the protective antioxidant effects of megadose methylprednisolone (MPSS) and the lazaroid 2-methylaminochroman (U-78517F) on the size of striatal lesions caused by quinolinic acid, an N-methyl-D-aspartate (NMDA) receptor agonist that mimics certain aspects of the secondary injury surrounding the pan-necrosis central to stroke or cerebral contusion. Treatment with MPSS (60 mg/kg/day) before quinolinate infusion and continuing through the first postoperative day caused a significant (P < 0.01) 56% increase in the size of striatal lesions. In contrast, treatment with MPSS given 2 to 6 hours after creation of the lesion did not affect lesion size. Animals treated with U-78517F also failed to exhibit any neuroprotective effects. The detrimental effect of pretreatment with megadose MPSS is likely the result of deleterious energy-depleting glucocorticoid effect of pretreatment with megadose MPSS is likely the result of deleterious energy-depleting glucocorticoid effects that outweight any positive antioxidant effects. We conclude that megadose MPSS, although found to be beneficial in the treatment of spinal cord injury, may not be beneficial in the treatment of intracranial insults involving glutamate toxicity.

PET- and MRI-based assessment of glucose utilization, dopamine receptor binding, and hemodynamic changes after lesions to the caudate-putamen in primates

In vivo physiological changes associated with striatal pathology were determined by measurement of glucose utilization, binding to D1 receptors and dopamine reuptake sites, regional blood flow, and behavior before and after unilateral quinolinate infusions into caudate-putamen in three nonhuman primates (Macaca fascicularis and Macaca mulatta). Following the quinolinate lesion, symptoms similar to those of Huntington's disease could be induced by dopamine agonist treatment. In addition, all animals showed a long-term decrease in glucose utilization in the caudate by [19F]fluoro-2-deoxy-D-glucose positron emission tomography (PET). At 4-6 weeks following the lesion the average decrease in glucose utilization in the caudate-putamen was between 40 and 50% of the prelesion values in primates with large lesions. Corresponding caudate-putamen regional blood volume in these animals showed a 61 and 74% decrease as studied by magnetic resonance imaging with somewhat smaller changes observed in an index of cerebral blood flow. The caudate-putamen uptake rate constants for D1 receptors reflected neuronal loss and decreased by an average 40 and 48%, as determined by 11C-labeled Schering compound (SCH 39 166) and PET. Dopamine reuptake sites and fibers assessed by the 11C-labeled cocaine analog, WIN 35 428 compound, and PET showed a temporary decrease in areas with mild neuronal loss and a long-term decrease in striatal regions with severe destruction. These results, which were consistent with behavioral changes and neuropathology seen at postmortem examination, can be related to in vivo physiological studies of Huntington's disease patients.

Marked tissue eosinophilia within organizing chronic subdural hematoma membranes

Chronic subdural hematoma (CSDH) with membranes is a common problem in neurosurgery. Despite its frequency, the pathogenesis of this lesion is poorly understood. We conducted a systematic pathologic review, with clinical correlation, of all CSDH presenting to our institution over a two-year period which had undergone pathological examination. Surprisingly, we found marked tissue eosinophilia in most CSDH membranes in the process of organization. Eosinophils were not evident in fresh hemorrhage or in older membranes which were completely organized. These results demonstrated that eosinophils are frequently present in large numbers in the early phases of chronic subdural membrane (CSM) formation but not associated with chronic, organized membranes. No specific clinical cause for tissue eosinophilia was identified in the cases reviewed. Though the significance of these observations remains unclear, recognition of eosinophilia as a pathological feature of organizing CSM is important in order to avoid confusion with other diagnoses.

Herpesvirus-mediated gene delivery into the rat brain: specificity and efficiency of the neuron-specific enolase promoter

1. Herpesvirus infection with genetically engineered vectors is a way to deliver foreign gene products to various cell populations in culture and in vivo. Selective neuronal gene expression can be achieved using the neuron-specific enolase (NSE) promoter regulating expression of a transgene placed in and delivered by a herpesvirus vector. 2. We sought to determine the anatomical specificity and efficiency of herpesvirus-mediated gene transfer into the rat brain following placement of virus particles carrying a transgene (lacZ) under control of the NSE promoter. The virus utilized was thymidine kinase (TK) deficient and therefore replication deficient in the brain. 3. Infusion of 10(6) plaque-forming units of virus into the striatum caused a limited number of striatal neurons to express the lacZ transgene mRNA and protein product 7 days postinfection. In addition, small numbers of neurons expressing the transgene mRNA and protein were found ipsilateral to the viral injection in the frontal cortex, substantia nigra pars compacta, and thalamus. Neurons at these anatomic loci project directly to the striatal injection site. No other cells within the brains of injected animals expressed the lacZ gene. 4. While this herpesvirus NSE vector was capable of introducing novel functional genetic information into postmitotic neurons within defined neuroanatomic constraints, the numbers of neurons expressing detectable levels of beta-galactosidase was minimal. The calculated efficiency of delivery and transgene expression at 7 days postinfection was 1 transgenic neuron per 10(4) virus particles infused. 5. We conclude that NSE probably is not an optimal promoter for use in gene delivery to CNS neurons in herpesvirus vectors and that the efficacy of gene delivery using other neuron-specific promoters placed at various sites in the herpes viral genome needs to be explored.

Striatal degeneration induced by mitochondrial blockade is prevented by biologically delivered NGF

Consistent with the notion that a defect in cellular energy metabolism is a cause of human neurodegenerative disease, systemic treatment with the mitochondrial complex II inhibitor 3-nitropropionic acid (3-NPA) can model the striatal neurodegeneration seen in Huntington's disease. Previously, we have found that nerve growth factor (NGF), delivered biologically by the implantation of a genetically altered fibroblast cell-line, can protect locally against striatal degeneration induced by infusions of high doses of glutamate receptor agonists. We now report that implantation of NGF-secreting fibroblasts reduces the size of adjacent striatal 3-NPA lesions by an average of 64%. We conclude that biologically delivered NGF protects neurons against excitotoxicity and mitochondrial blockade--both energy-depleting processes--implying that appropriate neurotrophic support in the adult brain could protect against neurodegenerative diseases caused in part by energy depletion.

Relationships between stress protein induction and NMDA-mediated neuronal death in the entorhinal cortex

The entorhinal cortex (EC) appears to be one of the earliest regions to express cellular pathology in aging and Alzheimer's disease. The relationships between cellular stress protein responses and the temporal and spatial aspects of cell death induced by N-methyl-D-aspartate (NMDA) was investigated in this anatomical region. Low doses of NMDA were infused stereotactically into the medial EC of the rat. At intervals starting from 0.5 h up to 7 days after a 1.25-microliters EC infusion of 15 mM NMDA, 30 mM NMDA, or saline, the expression of ubiquitin (Ub), 72-kDa heat shock protein (HSP 72), and c-Fos was determined in relation to neuronal death. Volumes of entorhinal Ub- and HSP 72-like immunoreactivity peaked between 18 and 48 h after either 15 or 30 mM NMDA infusions. After 15 mM NMDA infusions, maximal volumes of HSP 72- and Ub-like immunoreactivity in the EC at 48 h were similar to the subsequent maximal volume of neuronal loss in the EC seen after 96 hours. After infusion of 30 mM NMDA, the final EC volume of neuronal loss seen at 7 days after NMDA corresponded to 70-80% of the maximal HSP-Ub stress protein response seen at 2 days, implying that a population of HSP 72- and Ub-immunopositive cells survived the NMDA insult. C-Fos expression as determined by immunoreactivity for the nuclear phosphoprotein (Fos) indicated neuronal activation at NMDA infusion sites, in the perirhinal cortex, hippocampus, and other sites throughout the injected hemisphere. In the EC, c-Fos immunoreactivity returned to baseline levels by 8 h, well before the dramatic increases in HSP 72 and Ub volumes. Our results demonstrate that HSP 72 and Ub expression in vivo precedes and correlates with, but does not necessarily lead to, neuronal death following glutamate receptor-mediated toxicity in the EC.

NGF reduces striatal excitotoxic neuronal loss without affecting concurrent neuronal stress

Nerve growth factor (NGF) has protective effects against striatal excitotoxic injury in the adult brain. To begin to define the mechanism of NGF-mediated sparing, we sought to determine the effects of biologically delivered NGF on the degree of neuronal stress and the development of excitotoxic lesions in the rat striatum. Immortalized fibroblasts genetically altered to secrete NGF (NGF[+]) or control fibroblasts (NGF[-]) were stereotactically implanted near the striatum 7 d before striatal infusion of an NMDA-receptor agonist. Two days after excitotoxin infusion, the volume of neuronal loss was reduced by 34% (p < 0.001) in the NGF[+] group when compared to the NGF[-] group; however, there was no difference in the volume of 72 kD heat shock protein (HSP72) immunoreactivity expressed in the two groups after 2 d. The final volumes of neuronal loss at 10 d were significantly greater than seen at 2 d, with the volume of neuronal loss in the NGF[+] group reduced by 20% (p < 0.004) when compared to the NGF[-] group. Interestingly, the volume of neuronal loss at 10 d in the NGF[-] group, but not the NGF[+] group, closely approximated the HSP72 immunoreactive volumes seen at 2 d. These results suggest that the cell stress marker, HSP72, is predictive of neuronal loss after striatal excitotoxic insult and while NGF treatment does not alter the overall HSP72 response, it significantly reduces subsequent neuronal loss. We conclude that NGF-mediated neuroprotective mechanisms alter neuronal response to injury without affecting the primary cell stress response to NMDA-receptor activation.

Effects of biologically delivered NGF, BDNF and bFGF on striatal excitotoxic lesions

Immortalized rat fibroblasts, genetically altered to secrete NGF, BDNF, and bFGF, were implanted in rat brain near the striatum 7 days before striatal infusion of excitotoxic quantities of an NMDA-receptor agonist. Analysis of striatal damage 7 days after lesioning revealed that implantation of NGF-secreting cells reduced the size of the excitotoxic lesions by more than 80% when compared with control cells, while implanting of bFGF-secreting cells caused a 30% decrease in excitotoxic lesion size. BDNF-secreting fibroblasts caused no protective sparing in the striatum in this lesion model. This finding shows that biological delivery of NGF and bFGF by grafting of genetically altered cells protects against glutamate toxicity in the adult striatum while grafting of BDNF-producing cells does not. Such observations begin to define a spectrum of neurotrophic agents able to mitigate the cell loss seen in neurodegeneration.

Local protective effects of nerve growth factor-secreting fibroblasts against excitotoxic lesions in the rat striatum

Neurotrophic factors, such as nerve growth factor (NGF), in addition to their role in neuronal development, have protective effects on neuronal survival. Intracerebral implantation of cells genetically altered to secrete high levels of NGF is also found to promote neuronal survival in experimental lesioning models of the brain. The range of activity for such biological delivery systems has not yet been well described either spatially or temporally. Therefore, the authors chose to study the local and distant protective effects of an NGF-secreting rat fibroblast cell line implanted in an excitotoxic lesion model of Huntington's disease. They found that preimplantation of NGF-secreting fibroblasts placed within the corpus callosum reduced the maximum cross-sectional area of a subsequent excitotoxic lesion in the ipsilateral striatum by 80% when compared to the effects of a non-NGF-secreting fibroblast graft, and by 83% when compared to excitotoxic lesions in ungrafted animals (p < 0.003). However, NGF-secreting cells placed in the contralateral corpus callosum failed to affect striatal lesion size significantly when compared to contralateral or ipsilateral non-NGF-secreting cell implants. Of note, fibroblasts were clearly visible within the graft site at 7 and 18 days after implantation; however, few cells within the grafts stained positively for NGF peptide or for the messenger ribonucleic acid (mRNA) encoding the transfected NGF gene-construct at either time point. These results show that biological delivery systems for NGF appear to have a profound but local effect on neuronal excitotoxicity, which will necessitate careful neurosurgical placement for maximum effect. Furthermore, the ability of this genetically altered cell line to synthesize NGF mRNA and peptide appears to decrease spontaneously in vivo, a characteristic that will need to be addressed before this method of biological delivery can be utilized as a treatment for chronic degenerative diseases.

Postoperative low-dose heparin decreases thromboembolic complications in neurosurgical patients

Thromboembolic complications are a major cause of postoperative morbidity and mortality in the neurosurgical patient. Prophylaxis with lower extremity pneumatic compression boots (PCBs) reduces the incidence of lower extremity deep vein thrombosis (DVT) but has not been shown to affect the incidence of pulmonary embolism (PE). Prophylaxis with low-dose heparin has consistently reduced the incidence of both DVT and PE in studies on general surgical patients but has not been adopted for use in neurosurgery primarily for fear of causing catastrophic hemorrhage. We report on a series of 138 consecutive adult patients who underwent major neurosurgical procedures on a general neurosurgical service at our institution. Patients were treated with intraoperative PCBs and, starting on the morning of the first postoperative day, with a regimen of 5000 U of heparin administered subcutaneously twice daily. This treatment was continued until patients were fully ambulatory. PCBs were discontinued 24 hours after the first administration of heparin. None of the heparin-treated patients suffered postoperative hemorrhage. We compared this series with a control group of 473 adult patients who had previously undergone major neurosurgical procedures on the same neurosurgical service. These patients had been treated with intraoperative and postoperative PCBs alone. The control group had a 3.2% incidence of thromboembolic complications (15 of 473; eight DVT, seven PE). Prophylaxis with PCBs plus heparin significantly (P = 0.020) reduced the incidence of thromboembolic complications: no PCBs/heparin-treated patient exhibited clinical evidence of PE or DVT (0%, 0/138). We conclude that a combination of intraoperative PCBs and postoperative low-dose heparin is a safe and effective method by which to reduce thromboembolic complications in the neurosurgical patient.

Is intracerebral schwannoma a developmental tumor of children and young adults? Case report and review

A case of intracerebral schwannoma in an 11-year-old girl is presented. Of the small number of intracerebral schwannomas reported without association to a cranial nerve, the majority have occurred in children or young adults. Several possible etiologies for this tumor type are discussed. Based upon the distribution of ages at presentation and theories of the pathological origin of this tumor, the possibility that intracerebral schwannoma represents a developmental tumor is suggested.

Regulated expression of the human corticotropin releasing hormone gene by cyclic AMP

The factors controlling the expression of the hypothalamic neuropeptide, corticotropin releasing hormone (CRH), are poorly understood. We have used a mouse anterior pituitary cell line, AtT-20, permanently transfected with the human CRH gene as a model for studying the regulation of the CRH gene by cyclic AMP. Previously, we demonstrated that in this system the CRH gene is correctly expressed and appropriately negatively regulated by glucocorticoids. Treatment of five CRH-producing cell lines with an activator of adenylate cyclase (forskolin, 0.1-50 microM for 24 h) caused a dose-dependent and specific increase in the amount of CRH mRNA and radioimmunoassay-detectable CRH peptide secreted into the medium. Ribonuclease protection analysis revealed that the CRH gene was transcribed from multiple transcriptional initiation sites located over several hundred nucleotides. Forskolin treatment resulted in a specific increase in the CRH mRNA transcripts initiating from one of these many transcriptional start sites.

Differential regulation of corticotropin-releasing hormone mRNA in rat brain

Corticotropin-releasing hormone (CRH), a major hypothalamic component of the hypothalamic-pituitary-adrenal axis, has been localized to both the paraventricular nucleus (PVN) and cerebral cortex. Adrenalectomy causes an increase in PVN CRH content, whereas its effect on cortical CRH content is not clear. In the present study, adrenalectomy resulted in a threefold rise in the CRH mRNA content of anatomic micropunches of the PVN of individual rats (P less than 0.001), which was abolished by dexamethasone replacement. In parietal cortex, adrenalectomy did not affect CRH mRNA content, whereas hypophysectomy resulted in a twofold rise in CRH mRNA content (P less than 0.02), which was not significantly reduced by dexamethasone replacement. These results demonstrate that the CRH gene is negatively regulated by glucocorticoid in the PVN but not in cerebral cortex and that the increase in cortical CRH mRNA content after hypophysectomy may be evidence for negative regulation of cortical CRH gene expression by a second pituitary-dependent factor other than glucocorticoid.

Development of symptomatic Chiari malformation in a child with craniofacial dysmorphism

We present the case of a 28-month-old child with craniofacial anomalies who presented for evaluation of apnea. The patient had associated symptoms referable to a Chiari malformation and MRI scanning of the head and cervical spine revealed some, but not all, of the anatomical features classically associated with the Chiari II malformation. The child has mid-face hypoplasia and it appeared that his posterior fossa hypertension was partially caused by anterior compression of the brain stem as a result of the malformation at the base of the skull. The patient responded dramatically to posterior fossa decompression. Evidence from this and other cases from the literature suggests that different pathophysiological mechanisms may cause the classic Chiari malformation and/or other anatomical abnormalities in the continuum between Chiari I and II.

Effects of restricted feeding schedules on circadian organization in squirrel monkeys

Free running circadian rhythms of motor activity, food-motivated lever-pressing, and either drinking (N = 7) or body temperature (N = 3) were recorded from 10 squirrel monkeys maintained in constant illumination with unlimited access to food. Food availability was then restricted to a single unsignaled 3-hour interval each day. The feeding schedule failed to entrain the activity rhythms of 8 monkeys, which continued to free-run. Drinking was almost completely synchronized by the schedule, while body temperature showed a feeding-induced rise superimposed on a free-running rhythm. Nonreinforced lever-pressing showed both a free-running component and a 24-hour component that anticipated the time of feeding. At the termination of the schedule, all recorded variables showed free-running rhythms, but in 3 animals the initial phase of the postschedule rhythms was advanced by several hours, suggesting relative coordination. Of the remaining 2 animals, one exhibited stable entrainment of all 3 recorded rhythms, while the other appeared to entrain temporarily to the feeding schedule. These results indicate that restricted feeding schedules are only a weak zeitgeber for the circadian pacemaker generating free-running rhythms in the squirrel monkey. Such schedules, however, may entrain a separate circadian system responsible for the timing of food-anticipatory changes in behavior and physiology.