Pediatric infectious aneurysms: individual patient pooled analysis on presentation, management and outcomes

BACKGROUND

Infectious intracranial aneurysms (IIAs) are a rare sequel of systemic infection and occur most commonly in patients with infective endocarditis (IE). Despite the increasing use of non-invasive screening angiography in patients with IE, the incidence remains low, yielding limited data on the management of IIAs in pediatric populations. We performed a pooled analysis of all published series of pediatric patients with IIAs to study the disease landscape including presentation, management, and outcomes.

METHODS

Data included in this study were pooled from published literature on IIAs between 1960 and 2023. Abstracts were selected for full review to include only manuscripts reporting at least one case of pediatric IIA (age 0-18 years).

RESULTS

A total of 145 pediatric patients with 178 IIAs were included. Patients presented with rupture in 68% of cases, of which 36% had intraparenchymal hemorrhage and 39% had subarachnoid hemorrhage. Using multivariate logistic regression, independent predictors of rupture were posterior location (aOR 10, P=0.041) and history of IE (aOR 7.2, P=0.001). Primary medical management was successful in 82% of cases with unruptured aneurysms while, in those with ruptured IIAs, medical management was successful in 26% of cases. The 90-day mortality rate was 28%. Using multivariate logistic regression, ruptured IIAs (aOR 5.4, P<0.01) and failure of medical management (aOR 11.1, P<0.05) were independent predictors of 90-day mortality.

CONCLUSION

Pediatric IIAs remain a rare complication of systemic or localized CNS infection in the pediatric population. Medical management of unruptured aneurysms is highly successful, while ruptured aneurysms have a remarkably high rate of failure of medical management and should be treated by early surgical or endovascular intervention when feasible.

Measurement of the ν_{e}-Nucleus Charged-Current Double-Differential Cross Section at ⟨E_{ν}⟩=2.4 GeV Using NOvA

The inclusive electron neutrino charged-current cross section is measured in the NOvA near detector using 8.02×10^{20} protons-on-target in the NuMI beam. The sample of GeV electron neutrino interactions is the largest analyzed to date and is limited by ≃17% systematic rather than the ≃7.4% statistical uncertainties. The double-differential cross section in final-state electron energy and angle is presented for the first time, together with the single-differential dependence on Q^{2} (squared four-momentum transfer) and energy, in the range 1  GeV≤E_{ν}<6  GeV. Detailed comparisons are made to the predictions of the GENIE, GiBUU, NEUT, and NuWro neutrino event generators. The data do not strongly favor a model over the others consistently across all three cross sections measured, though some models have especially good or poor agreement in the single differential cross section vs Q^{2}.

Utility of ventriculogallbladder shunts in complex cases of hydrocephalus related to extreme prematurity

OBJECTIVE

The management of hydrocephalus resulting from intraventricular hemorrhage related to extreme prematurity remains demanding. Given the complexities of controlling hydrocephalus in this population, less commonly used procedures may be required. The authors examined the utility of ventriculogallbladder (VGB) shunts in a series of such children.

METHODS

The authors retrospectively reviewed the medical records of all children who underwent surgery for hydrocephalus in the period from 2011 through 2019 at Children's Healthcare of Atlanta. Six patients who underwent VGB shunt placement were identified among a larger cohort of 609 patients who had either a new shunt or a newly changed distal terminus site. The authors present an analysis of this series, including a case of laparoscopy-assisted distal VGB shunt revision.

RESULTS

The mean age at initial shunt placement was 5.1 months (range 3.0-9.4 months), with patients undergoing a mean of 11.8 shunt procedures (range 5-17) prior to the initial VGB shunt placement at a mean age of 5.3 years (range 7.9 months-12.8 years). All 6 patients with VGB shunt placement had hydrocephalus related to extreme prematurity (gestational age < 28 weeks). At the time of VGB shunt placement, all had complex medical and surgical histories, including poor venous access due to congenital or iatrogenic thrombosis or thrombophlebitis and a peritoneum hostile to distal shunt placement related to severe necrotizing enterocolitis. VGB complications included 1 case of shunt infection, identified at postoperative day 6, and 2 cases of distal shunt failure due to retraction of the distal end of the VGB shunt. In all, there were 3 conversions back to ventriculoperitoneal or ventriculoatrial shunts due to the 2 previously mentioned complications, plus 1 patient who outgrew their initial VGB shunt. Three of 6 patients remain with a VGB shunt, including 1 who underwent laparoscopy-assisted distal shunt revision 110.5 months after initial VGB shunt insertion.

CONCLUSIONS

Placement of VGB shunts should be considered in the armamentarium of procedures that may be used in the particularly difficult cohort of children with hydrocephalus related to extreme prematurity. VGB shunts show utility as both a definitive treatment and as a "bridge" procedure until the patient is larger and comorbid abdominal and/or vascular issues have resolved sufficiently to allow conversion back to ventriculoperitoneal or ventriculoatrial shunts, if needed.

Application of a Halo Fixator for the Treatment of Pediatric Spinal Deformity

Background

In spine surgery, the halo fixator was initially utilized to stabilize cervical fusions in patients with poliomyelitis. More recently, the indications for halo fixation have evolved to include stabilization and definitive treatment for upper cervical spine injuries (Jefferson fractures, atlanto-occipital dissociations, odontoid fractures, etc.), treatment of atlantoaxial rotatory subluxation, stabilization of long cervical fusions, and preoperative traction. In the realm of pediatric spinal deformity, halo fixation has proved to be a valuable resource for severe or neglected spinal deformities. In this video article, we demonstrate the application of a halo fixator in a pediatric patient with severe scoliosis.

Description

The procedure includes appropriate pin placement in the safe zones of the skull performed under either general anesthesia or local anesthesia. Pins are secured to a halo frame that is sized to be 2 cm larger than the circumference of the skull and are tightened according to age-specific torque guidelines.

Alternatives

Alternative treatments vary from cervical spine immobilization to definitive surgical treatment in the spine, or even spinal osteotomies, depending on the underlying spinal pathology.

Rationale

The halo fixator works by limiting motion of the cervical spine in flexion, extension, and axial rotation. The halo is also able to control and correct translational injuries of the cervical spine. In the setting of spinal deformity, the halo fixator can also be utilized to overcome the effects of gravity and lengthen the spine.

Expected Outcomes

For spinal deformities, the halo fixator can be expected to lengthen the spine and increase deformity flexibility prior to definitive surgical treatment in the spine or growth-friendly spinal instrumentation.

Important Tips

Correct identification of safe zones for pin placement is vital to correct pin placement.For pediatric patients, it is important to obtain fixation with a minimum of 6 to 8 pins.Pins should be tightened with use of a torque-limiting wrench, up to no more than 1 in/lb (55.9 mm/kg) per year of age, up to a maximum of 8 in/lb (447.9 mm/kg).Applied traction should be a maximum of 50% of the body weight of the patient.Neurovascular examination is vital following application of weight.

Primary breast lymphoma - a case report

BACKGROUND

Primary breast lymphoma is a rare disease and accounts for 0.4-0.5% of malignant breast neoplasms and 1.7-2.2% of extra-nodal lymphomas, with diffuse large B-cell lymphoma (DLBCL) as the most common histologic subtype.

CASE

A 47-year-old female with beta thalassemia presented with a lump of the left breast, redness, pain, and swelling of her left breast. Physical examination showed tender, red, swollen left breast. Laboratory findings show mild anemia and normal level of lactate dehydrogenase 329 U/L (normal range: 240-480 U/L). PET scan showed hypermetabolic mass with irregular margins covering the whole left breast quadrants with the size of 11.25 x 5.17cm with left pectoralis major, left parasternal, and left axillary hypermetabolic nodules. Histopathology and immunohistochemistry staining showed a non-germinal center B-cell-like subtype of DLBCL CD20+. We administered the R-CHOP regimen (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednison) every 3 weeks for 6 cycles. The response was complete remission. The patient tolerated the chemotherapy well and achieved long term complete remission.

CONCLUSION

Primary breast lymphoma is a rare disease with the most common subtype is diffuse large B-cell lymphoma. Systemic chemother-apy R-CHOP is the treatment option for primary breast diffuse large B-cell lymphoma.

Prospective feasibility and safety assessment of surgical biopsy for patients with newly diagnosed diffuse intrinsic pontine glioma

Background

Diagnosis of diffuse intrinsic pontine glioma (DIPG) has relied on imaging studies, since the appearance is pathognomonic, and surgical risk was felt to be high and unlikely to affect therapy. The DIPG Biology and Treatment Study (DIPG-BATS) reported here incorporated a surgical biopsy at presentation and stratified subjects to receive FDA-approved agents chosen on the basis of specific biologic targets.

Methods

Subjects were eligible for the trial if the clinical features and imaging appearance of a newly diagnosed tumor were consistent with a DIPG. Surgical biopsies were performed after enrollment and prior to definitive treatment. All subjects were treated with conventional external beam radiotherapy with bevacizumab, and then stratified to receive bevacizumab with erlotinib or temozolomide, both agents, or neither agent, based on O6-methylguanine-DNA methyltransferase status and epidermal growth factor receptor expression. Whole-genome sequencing and RNA sequencing were performed but not used for treatment assignment.

Results

Fifty-three patients were enrolled at 23 institutions, and 50 underwent biopsy. The median age was 6.4 years, with 24 male and 29 female subjects. Surgical biopsies were performed with a specified technique and no deaths were attributed to the procedure. Two subjects experienced grade 3 toxicities during the procedure (apnea, n = 1; hypertension, n = 1). One subject experienced a neurologic deficit (left hemiparesis) that did not fully recover. Of the 50 tumors biopsied, 46 provided sufficient tissue to perform the study assays (92%, two-stage exact binomial 90% CI: 83%-97%).

Conclusions

Surgical biopsy of DIPGs is technically feasible, associated with acceptable risks, and can provide biologic data that can inform treatment decisions.

Evidence of positive selection and concerted evolution in the rapidly evolving PRDM9 zinc finger domain in goats and sheep

Meiotic recombination contributes to augmentation of genetic diversity, exclusion of deleterious alleles and proper segregation of chromatids. PRDM9 has been identified as the gene responsible for specifying the location of recombination hotspots during meiosis and is also the only known vertebrate gene associated with reproductive isolation between species. PRDM9 encodes a protein with a highly variable zinc finger (ZF) domain that varies between as well as within species. In the present study, the ZF domain of PRDM9 on chromosome 1 was characterized for the first time in 15 goat breeds and 25 sheep breeds of India. A remarkable variation in the number and sequence of ZF domains was observed. The number of ZF repeats in the ZF array varied from eight to 12 yielding five homozygous and 10 heterozygous genotypes. The number of different ZF domains was 84 and 52 producing 36 and 26 unique alleles in goats and sheep respectively. The posterior mean of dN/dS or omega values were calculated using the codeml tool of pamlx to identify amino acids that are evolving positively in goats and sheep, as positions -1, +3 and +6 in the ZF domain have been reported to experience strong positive selection across different lineages. Our study identified sites -5, -1, +3, +4 and +6 to be experiencing positive selection. Small ruminant zinc fingers were also found to be evolving under concerted evolution. Our results demonstrate the existence of a vast diversity of PRDM9 in goats and sheep, which is in concert with reports in many metazoans.

Outcome of Transsphenoidal Surgery for Cushing Disease: A Single-Center Experience Over 32 Years

BACKGROUND

Transsphenoidal surgery is the standard approach for treating Cushing disease. Evidence is needed to document effectiveness.

OBJECTIVE

To analyze results of transsphenoidal surgery in 276 consecutive patients, including 19 children.

METHODS

Medical records were reviewed for patients treated initially with surgery for Cushing disease from 1980 to 2012. Radiographic features, pathology, remissions, recurrences, and complications were recorded. Patients were categorized for statistical analysis based on tumor size (microadenomas, macroadenomas, and negative imaging) and remission type (type 1 = morning cortisol ≤3 μg/dL; type 2 = morning cortisol normal).

RESULTS

Females comprised 78% of patients and were older than men. Imaging showed 50% microadenomas, 13% macroadenomas, and 37% negative for tumor. Remission rates for microadenomas, macroadenomas, and negative imaging were 89%, 66%, and 71%, respectively. Patients with microadenomas were more likely to have type 1 remission. Pathology showed adrenocorticotropic hormone-secreting adenomas in 82% of microadenomas, in 100% of macroadenomas, and in 43% of negative imaging. The incidence of hyperplasia was 8%. The finding of hyperplasia or no tumor on pathology predicted treatment failure. The recurrence rate was 17%, with an average time to recurrence of 4.0 years. Patients with type 1 remission had a lower rate of recurrence (13% type 1 vs 50% type 2) and a longer time to recurrence. Children had similar imaging findings, remission rates, and pathology. There were no operative deaths.

CONCLUSION

Transsphenoidal surgery provides a safe and effective treatment for Cushing disease. For both adults and children, the best outcomes occurred in patients with microadenomas and/or those with type 1 remission.

Exon skipping creates novel splice variants of DMC1 gene in ruminants

Disrupted meiotic cDNA1 (DMC1) recombinase plays a pivotal role in homology search and strand exchange reactions during meiotic homologous recombination. In the present study, full length coding sequence of DMC1 gene was sequence characterized for the first time from four ruminant species (cattle, buffalo, sheep and goat) and phylogenetic relationship of ruminant DMC1 with other eukaryotes was analyzed. DMC1 gene encodes a putative protein of 340 amino acids in cattle, sheep and buffalo and 341 amino acids in goat. A high degree of evolutionary conservation at both nucleotide and amino acid level was observed for the four ruminant orthologs. In cattle and sheep, novel alternatively spliced mRNAs with skipping of exons 7 and 8 (Transcript variant 1, TV1) were isolated in addition to the full length (FL) transcript. Novel transcript variants with partial skipping of exon 7 and complete skipping of exon 8 (Transcript variant 2, TV2) were found in sheep and goat. The presence of these variants was validated by amplifying cDNA isolated from testis tissue of ruminants using two oligonucleotides flanking the deleted region. To accurately estimate their relative proportions, real-time PCR was performed using primers specific for each variant. Expression level of DMC1-FL was significantly higher than that of TV1 in cattle and TV2 in goat (P < 0.05). Relative ratio for expression of DMC1-FL: TV1: TV2 in sheep was 6.78: 1.43: 1. In-silico analysis revealed presence of splice variants of DMC1 gene across other mammalian species underpinning the role of alternative splicing in functional innovation.

Successful Retreatment of a Child with a Refractory Brainstem Ganglioglioma with Vemurafenib

A child with brainstem ganglioglioma underwent subtotal resection and focal radiation. Magnetic resonance imaging confirmed tumor progression 6 months later. Another partial resection revealed viable BRAF V600E-positive residual tumor. Vemurafenib (660 mg/m(2) /dose) was administered twice daily, resulting in >70% tumor reduction with sustained clinical improvement for 1 year. Vemurafenib was then terminated, but significant tumor progression occurred 3 months later. Vemurafenib was restarted, resulting in partial response. Toxicities included Grade I pruritus and Grade II rash. Vemurafenib was effectively crushed and administered in solution via nasogastric tube. We demonstrate benefit from restarting vemurafenib therapy.

Utility of surveillance imaging after minor blunt head trauma

OBJECT

Nonoperative blunt head trauma is a common reason for admission in a pediatric hospital. Adverse events, such as growing skull fracture, are rare, and the incidence of such morbidity is not known. As a result, optimal follow-up care is not clear.

METHODS

Patients admitted after minor blunt head trauma between May 1, 2009, and April 30, 2013, were identified at a single institution. Demographic, socioeconomic, and clinical characteristics were retrieved from administrative and outpatient databases. Clinical events within the 180-day period following discharge were reviewed and analyzed. These events included emergency department (ED) visits, need for surgical procedures, clinic visits, and surveillance imaging utilization. Associations among these clinical events and potential contributing factors were analyzed using appropriate statistical methods.

RESULTS

There were 937 admissions for minor blunt head trauma in the 4-year period. Patients who required surgical interventions during the index admission were excluded. The average age of the admitted patients was 5.53 years, and the average length of stay was 1.7 days; 15.7% of patients were admitted for concussion symptoms with negative imaging findings, and 26.4% of patients suffered a skull fracture without intracranial injury. Patients presented with subdural, subarachnoid, or intraventricular hemorrhage in 11.6%, 9.19%, and 0.53% of cases, respectively. After discharge, 672 patients returned for at least 1 follow-up clinic visit (71.7%), and surveillance imaging was obtained at the time of the visit in 343 instances. The number of adverse events was small and consisted of 34 ED visits and 3 surgeries. Some of the ED visits could have been prevented with better discharge instructions, but none of the surgery was preventable. Furthermore, the pattern of postinjury surveillance imaging utilization correlated with physician identity but not with injury severity. Because the number of adverse events was small, surveillance imaging could not be shown to positively influence outcomes.

CONCLUSIONS

Adverse events after nonoperative mild traumatic injury are rare. The routine use of postinjury surveillance imaging remains controversial, but these data suggest that such imaging does not effectively identify those who require operative intervention.

Guiding intracortical brain tumour cells to an extracortical cytotoxic hydrogel using aligned polymeric nanofibres

Glioblastoma multiforme is an aggressive, invasive brain tumour with a poor survival rate. Available treatments are ineffective and some tumours remain inoperable because of their size or location. The tumours are known to invade and migrate along white matter tracts and blood vessels. Here, we exploit this characteristic of glioblastoma multiforme by engineering aligned polycaprolactone (PCL)-based nanofibres for tumour cells to invade and, hence, guide cells away from the primary tumour site to an extracortical location. This extracortial sink is a cyclopamine drug-conjugated, collagen-based hydrogel. When aligned PCL-nanofibre films in a PCL/polyurethane carrier conduit were inserted in the vicinity of an intracortical human U87MG glioblastoma xenograft, a significant number of human glioblastoma cells migrated along the aligned nanofibre films and underwent apoptosis in the extracortical hydrogel. Tumour volume in the brain was significantly lower following insertion of aligned nanofibre implants compared with the application of smooth fibres or no implants.

Return to system within 30 days of pediatric neurosurgery

OBJECT

Quality assessment measures have not been well developed for pediatric neurosurgical patients. This report documents the authors' experience in extracting information from an administrative database to establish the rate of return to system within 30 days of pediatric neurosurgical procedures.

METHODS

Demographic, socioeconomic, and clinical characteristics were prospectively collected in administrative, business, and operating room databases. The primary end point was an unexpected return to the hospital system within 30 days from the date of a pediatric neurosurgical procedure. Statistical methods were used to identify clinical and demographic factors associated with the primary end point.

RESULTS

There were 1358 pediatric neurosurgical procedures performed in the Children's Healthcare of Atlanta operating rooms in 2012, with 37.4% of these surgeries being preceded by admissions through the emergency department. Medicare or Medicaid was the payor for 54.9% of surgeries, and 37.6% of surgeries were shunt related. There were 148 unexpected returns to the system within 30 days after surgery, and in 109 of these cases, the patient had a presenting complaint that was attributable to the index surgery (related returns). The most common complaints were headache, nausea, vomiting, or seizure after shunt revision or cranial procedures (n = 62). The next most common reason for re-presentation was for wound concerns (n = 30). Thirty-seven of the 109 related returns resulted in a reoperation. The monthly rate of related returns was 8.1% ± 2.5% over the 12-month study period. When using related returns as the dependent variable, the authors found that patients who underwent a shunt-related surgery were both more likely to unexpectedly return to the system (OR 1.86, p = 0.008) and to require surgery upon readmission (OR 3.28, p = 0.004). Because an extended hospitalization shortened the window of time for readmission after surgery, extended length of stay was protective against return to system within 30 days of surgery. Importantly, if related and unrelated returns were analyzed together as the dependent variable (n = 148), no independent clinical and demographic risk factor could be identified.

CONCLUSIONS

Quality assessment measures need to be clearly and carefully defined, as the definition itself will impact the analytical results. Clinicians must play a leading role in the development of these measures to ensure their clinical meaningfulness.

The use of inside-outside screws for occipitocervical fusion in pediatric patients

OBJECT

The authors describe the use of inside-outside occipital screws in 21 children with occipitocervical instability requiring occipitocervical fusion.

METHODS

The ages of the patients were from 2 to 15 years, and patients presented with a variety of causes of occipitocervical instability, including congenital disorders, posttraumatic instability, idiopathic degeneration, and postoperative instability. Surgeries frequently included foramen magnum decompression, duraplasty, and laminectomy, but all patients required occipitocervical instrumentation and arthrodesis. Postoperative orthosis included the use of either a cervical collar or halo device. In all but one case, patients were followed postoperatively for at least 12 months.

RESULTS

The mean age of patients was 9.93 years. Inside-outside screws were used in all reported cases. Rib autograft was used in all patients. In addition, demineralized bone matrix was used in 2 cases, and bone morphogenetic protein was used in 2 patients. Two patients required halo placement, and the other 19 were placed in cervical collars. The average time postoperative orthotics were used was 2.82 months. Arthrodesis was determined radiographically and was noted in all patients. No operative complications were noted; however, postoperative complications included 1 wound infection, 2 cases of hardware loosening, and the need for tracheostomy in 2 patients.

CONCLUSIONS

Inside-outside screws were found to be a useful component of occipitocervical instrumentation in pediatric patients ranging from 2 to 15 years of age. Arthrodesis was demonstrated in all cases.

Transient enlargement of craniopharyngioma after radiation therapy: pattern of magnetic resonance imaging response following radiation

Clinical experience suggests that craniopharyngiomas may temporarily increase in size after radiation therapy (RT). The study goal is to determine the incidence and natural history of this response in a cohort of patients managed at Children's Healthcare of Atlanta (CHOA) or Emory Healthcare (EHC). Between 08/1998 and 06/2009, 41 children and young adults were diagnosed with craniopharyngioma at CHOA and/or EHC. Of these, 21 received external-beam radiation and were included in our analysis. Serial magnetic resonance imaging (MRI) studies were evaluated volumetrically to assess response to RT. Median age at diagnosis was 8.2 years (range 3.2-23.5 years). Median radiation dose was 54.0 Gy using standard fractionation (1.8-2.0 Gy/day). With median follow-up of 41.3 months (range 7.2-121.8 months), actuarial local control and overall survival rates at 5 years were 78.7 % and 100 %, respectively. Of subjects, 52.4 % of subjects (11 of 21) were noted on serial MRI evaluation to have tumor enlargement (mostly cystic component) after radiation before eventual shrinkage without further intervention. For tumors that expanded, the median volume increase was 33.9 % (range 15.6-224.4 %). Median time to maximal tumor/cyst expansion was 1.5 months (range 1.0-5.0 months). Finally, nearly all patients (20 of 21) showed a measurable objective response to therapy by MRI regardless of ultimate disease control. Median time to maximal response post-radiation, as defined by MRI, was 9.5 months (range 3.5-39.9 months). In summary, RT is effective for managing craniopharyngioma. However, despite good ultimate responses, approximately 50 % of the patients show tumor/cyst expansion on MRI over the first few months post-radiation. Caution should be taken not to subject these patients to "salvage surgery" or cyst aspiration during this early time unless there are other overriding surgical indications. Understanding the natural history of this phenomenon could potentially help guide the management of these craniopharyngioma patients.

Peripheral nerve injuries in weight training: sites, pathophysiology, diagnosis, and treatment

Direct trauma, compression caused by muscle hypertrophy or other soft tissue changes, or excessive stretching of a peripheral nerve in the upper extremity may lead to uncommon-but potentially serious-complications. Clinicians are seeing more of these injuries as weight training, power lifting, bodybuilding, cross-training, and general physical conditioning with weights become more popular. Symptoms of pain, weakness, paresthesia, or palsy; physical exam findings; electromyography; and nerve conduction studies are used to make the diagnosis. Most conditions respond well to conservative measures, such as rest from the offending exercise and correction of poor technique, but surgery may be required for complete clinical resolution in severe cases.

Massive symptomatic subependymoma of the lateral ventricles: case report and review of the literature

Subependymomas are benign intraventricular tumors with an indolent growth pattern, which are usually asymptomatic, and most commonly occur in the fourth and lateral ventricles. When symptomatic, subependymomas often obstruct critical portions of the cerebrospinal fluid (CSF) pathway, causing hydrocephalus, and range from 3 cm to 5 cm in size. We report a case of an unusually massive subependymoma of the lateral ventricles treated with subtotal resection, ventriculoperitoneal shunt, and post-surgical radiation. The clinical course, radiographic and pathologic characteristics of this massive intraventricular subependymoma are discussed, as well as the differential diagnosis of lateral ventricular masses and a review of the literature concerning subependymomas.

Ascorbate inhibits edema in brain slices

Ascorbate is an essential antioxidant in the CNS, localized predominantly in neuronal cytosol. Slices of mammalian brain rapidly lose ascorbate, however, when incubated in ascorbate-free media; brain slices also take up water and swell. Here we investigated water gain in coronal slices of rat forebrain incubated with and without ascorbate for 1-3 h at 34 degrees C. Slices progressively gained water in ascorbate-free media, with a significant 12% water increase after 3 h at 34 degrees C, compared with the water content of slices after a 1-h recovery period at 24 degrees C, immediately following slice preparation. Inclusion of 400 micro M ascorbate in the medium led to an increase in tissue ascorbate content and prevented water gain at 34 degrees C. By contrast, water gain was not inhibited by isoascorbate or thiourea, which are antioxidants that are not accumulated in brain cells. The oxidant H2O2 enhanced water gain, whereas a cocktail of NMDA and non-NMDA receptor blockers inhibited edema formation to the same extent as ascorbate. These data demonstrate that brain edema, linked to glutamate-receptor activation, can result from intracellular oxidative stress and that this can be prevented by ascorbate.