Exactly solvable one-dimensional quantum models with gamma matrices.

In this paper we write exactly solvable generalizations of one-dimensional quantum XY and Ising-like models by using 2^{d}-dimensional gamma matrices as the degrees of freedom on each site. We show that these models result in quadratic Fermionic Hamiltonians with Jordan-Wigner-like transformations. We illustrate the techniques using a specific case of four-dimensional gamma matrices and explore the quantum phase transitions present in the model.

Anaplastic glioneuronal tumor with KIAA1549/BRAF fusion.

Glioneuronal tumors are usually low-grade and have favorable prognosis. The anaplastic glioneuronal tumor with KIAA1549/BRAF fusion has not yet been documented. This article reports a case of glioneuronal tumor with anaplasia and KIAA1549/BRAF fusion to illuminate the importance of KIAA1549/BRAF fusion in high-grade glioneuronal tumors. A ten-year-old boy presented with one year of headache and three months of blurry vision and proptosis. Ophthalmologic evaluation revealed bilateral papilledema. Magnetic resonance imaging showed a large mixed cystic and solid mass in the left frontal lobe of cerebrum. Histologic analysis demonstrated a neoplasm with pseudopapillary growth pattern, focal necrosis, microcalcification, and brisk mitotic activity with a high Ki67 labeling index of focally up to 20%. Immunohistochemical assessment identified a mixed glial and neuronal neoplastic cell population. Molecular studies revealed a KIAA1549/BRAF fusion. The histological and molecular changes are consistent with an anaplastic glioneuronal tumor with KIAA1549/BRAF fusion. In view of the fact that the effective, targeted therapies for the tumors with KIAA1549/BRAF fusion are available, detection of KIAA1549/BRAF fusion for high-grade glioneuronal tumors is clinically helpful.

Synchronous Primary Central Nervous System and Pulmonary Lymphoma in a 7-Year-Old Female with Unspecified T-Cell Immunodeficiency.

Primary central nervous system lymphoma (PCNSL) is rare in children with immunocompromise as an important risk factor. A 7-year-old girl with unspecified T-cell immunodeficiency presented with left-sided weakness and was found to have a right-sided frontal lobe mass on imaging. The mass was resected; histopathology and molecular studies evidenced diffuse large B-cell lymphoma. Prior chest imaging had revealed left upper lobe mass, and repeat chest imaging revealed multiple pulmonary nodules, initially concerning for metastasis. Video-assisted thoracoscopic surgical wedge resection of the lung mass was performed; the molecular profile was distinct from the PCNSL, suggesting synchronous de novo lymphomagenesis of brain and pulmonary primaries.

Pharmacokinetics of continuous-infusion meropenem for the treatment of Serratia marcescens ventriculitis in a pediatric patient.

Neither guidelines nor best practices for the treatment of external ventricular drain (EVD) and ventriculoperitoneal shunt infections exist. An antimicrobial regimen with a broad spectrum of activity and adequate cerebrospinal fluid (CSF) penetration is vital in the management of both EVD and ventriculoperitoneal infections. In this case report, we describe the pharmacokinetics of continuous-infusion meropenem for a 2-year-old girl with Serratia marcescens ventriculitis. A right frontal EVD was placed for the management of a posterior fossa mass with hydrocephalus and intraventricular hemorrhage. On hospital day 6, CSF specimens were cultured, which identified a pan-sensitive Serratia marcescens with an initial cefotaxime minimum inhibitory concentration of 1 µg/ml or less. The patient was treated with cefotaxime monotherapy from hospital days 6 to 17, during which her CSF cultures and Gram's stain remained positive. On hospital day 26, Serratia marcescens was noted to be resistant to cefotaxime (minimum inhibitory concentration > 16 µg/ml), and the antimicrobial regimen was ultimately changed to meropenem and amikacin. Meropenem was dosed at 40 mg/kg/dose intravenously every 6 hours, infused over 30 minutes, during which, simultaneous serum and CSF meropenem levels were measured. Meropenem serum and CSF levels were measured at 2 and 4 hours from the end of the infusion with the intent to perform a pharmacokinetic/pharmacodynamic analysis. The resulting serum meropenem levels were 12 µg/ml at 2 hours and "undetectable" at 4 hours, with CSF levels of 1 and 0.5 µg/ml at 2 and 4 hours, respectively. On hospital day 27, the meropenem regimen was changed to a continuous infusion of 200 mg/kg/day, with repeat serum and CSF meropenem levels measured on hospital day 33. The serum and CSF levels were noted to be 13 and 0.5 µg/ml, respectively. The serum level of 13 µg/ml corresponds to an estimated meropenem clearance from the serum of 10.2 ml/kg/minute. Repeat meropenem levels from the serum and CSF on hospital day 37 were 15 and 0.5 µg/ml, respectively. After instituting the continuous-infusion meropenem regimen, only three positive CSF Gram's stains were noted, with the CSF cultures remaining negative. The continuous-infusion dosing regimen allowed for 100% probability of target attainment in the serum and CSF and a successful clinical outcome.

Surgical management of symptomatic Chiari II malformation in infants and children.

PURPOSE: Variation exists in the surgical methods employed for decompression of Chiari II malformation (CIIM), yet an evaluation of these techniques has not been performed. The purpose of this study was to assess the efficacy of bony decompression (cervical laminectomy alone versus suboccipital craniectomy with laminectomy) with or without dural augmentation for the treatment of symptomatic CIIM. METHODS: Clinical records of children 0-18 years of age who underwent surgical repair of myelomeningocele or CIIM decompression at St. Louis Children's Hospital (SLCH) from 1990-2011 were reviewed. Signs/symptoms prompting decompression, surgical technique, operative parameters, and clinical outcomes were recorded for analysis. RESULTS: Thirty-three subjects were treated at SLCH for CIIM decompression. Twenty-six subjects underwent bony decompression only (21 cervical laminectomy alone, 5 suboccipital craniectomy + cervical laminectomy) while seven underwent bony decompression with upfront dural augmentation (three cervical laminectomy alone, four suboccipital craniectomy + cervical laminectomy). Median follow up was 5.0 years (range, 3 months-19 years). Symptomatic improvement was noted in 20/33 subjects (60.6%). Sixty-two (61.5%) percent of children who underwent bony decompression had symptomatic improvement, compared with 57.1% of those with upfront dural augmentation (p = 0.37). Estimated blood loss, operative time, and length of perioperative hospital stay appeared lower in the bony decompression group but were not statistically different in this limited cohort. CONCLUSIONS: The results from this series suggest that bony CIIM decompression via tailored cervical laminectomies alone, without suboccipital craniectomy or upfront dural augmentation, is a reasonable initial management approach for decompression of symptomatic CIIM.

Hemispherotomy: efficacy and analysis of seizure recurrence.

OBJECT: Hemispherotomy generally is performed in hemiparetic patients with severe, intractable epilepsy arising from one cerebral hemisphere. In this study, the authors evaluate the efficacy of hemispherotomy and present an analysis of the factors influencing seizure recurrence following the operation. METHODS: The authors performed a retrospective review of 49 patients (ages 0.2-20.5 years) who underwent functional hemispherotomy at their institution. The first 14 cases were traditional functional hemispherotomies, and included temporal lobectomy, while the latter 35 were performed using a modified periinsular technique that the authors adopted in 2003. RESULTS: Thirty-eight of the 49 patients (77.6%) were seizure free at the termination of the study (mean follow-up 28.6 months). Of the 11 patients who were not seizure free, all had significant improvement in seizure frequency, with 6 patients (12.2%) achieving Engel Class II outcome and 5 patients (10.2%) achieving Engel Class III. There were no cases of Engel Class IV outcome. The effect of hemispherotomy was durable over time with no significant change in Engel class over the postoperative follow-up period. There was no statistical difference in outcome between surgery types. Analysis of factors contributing to seizure recurrence after hemispherotomy revealed no statistically significant predictors of treatment failure, although bilateral electrographic abnormalities on the preoperative electroencephalogram demonstrated a trend toward a worse outcome. CONCLUSIONS: In the present study, hemispherotomy resulted in freedom from seizures in nearly 78% of patients; worthwhile improvement was demonstrated in all patients. The seizure reduction observed after hemispherotomy was durable over time, with only rare late failure. Bilateral electrographic abnormalities may be predictive of posthemispherotomy recurrent seizures.

Obstructive hydrocephalus due to a third ventricular neuroepithelial cyst.

Cysts occupying the third ventricle are rare lesions and may appear as an unusual cause of obstructive hydrocephalus. Various types of lesions occur in this location, and they generally have an arachnoidal, endodermal, or neuroepithelial origin. The authors present a case of acute hydrocephalus following minor trauma in a child due to cerebrospinal fluid outflow obstruction by a third ventricular cyst. Definitive diagnosis of this cystic lesion was possible only with contrast ventriculography and not routine computed tomography or magnetic resonance imaging. The investigation, treatment, and pathological findings are discussed.

Cumulative diagnostic radiation exposure in children with ventriculoperitoneal shunts: a review.

INTRODUCTION: Children may be more vulnerable to diagnostic radiation exposure because of the increased dose-volume ratio and the increased lifetime risk per unit dose of radiation from early exposure. Moreover, recent radiological literature suggests that exposure to ionizing radiation from imaging studies may play a role in the later development of malignancies. MATERIALS AND METHODS: We review the literature and present two illustrative clinical examples of children (each child developed head and neck malignancies during their late teen years) with hydrocephalus requiring multiple cerebrospinal fluid (CSF) shunt revisions and diagnostic computerized tomography (CT) scans throughout their life. DISCUSSION: The literature reviewed suggests that children are more prone to diagnostic radiation exposure. Although it is not possible to prove that the multiple diagnostic studies result in malignancies, our review of the literature and illustrative cases describing malignancy risk and radiation exposure should give clinicians pause when considering requesting multiple diagnostic CT studies in children during the evaluation of possible CSF shunt dysfunction. Alternative tests such as "shunt MRI" protocols should be considered for patients and used whenever possible to minimize exposure to ionizing radiation.

Surgical navigation technology for treatment of pneumosinus dilatans.

The objective of this study is to present the use of surgical navigation in the selective removal of the anterior table of the frontal sinus in a patient with pneumosinus dilatans. A 16-year-old boy presented with progressive deformity of the forehead and left postauricular sulcus due to pneumosinus dilatans. Reconstruction of the anterior table of the frontal bone was assisted by a surgical navigation system that used data from a preoperative computed tomography scan of the head and neck to map out the boundaries of the frontal sinus. The device enabled selective resection of the anterior table without violation of the cranial cavity.

Pediatric neurosurgical injuries associated with all-terrain vehicle accidents: a 10-year experience at St. Louis Children's Hospital.

OBJECT: All-terrain vehicles (ATVs) have been characterized as inherently unstable and are associated with significant pediatric injuries in the US. The authors performed a study to analyze data obtained in pediatric patients who had sustained neurological injuries in ATV-related accidents, identify potential risk factors, and propose preventive measures. The study is based on a 10-year experience at the St. Louis Children's Hospital. METHODS: The authors retrospectively analyzed data obtained in all patients admitted to the St. Louis Children's Hospital between 1993 and 2003, limiting their focus to pediatric cases involving ATV-related accidents. A total of 185 patients were admitted with these criteria. Sixty-two patients (33.5%) suffered neurological injuries; there were 42 male and 20 female patients whose age ranged from 2 to 17 years. The most common injuries included skull fracture (37 cases) and closed head injury (30 cases). There were 39 cases of intracranial hemorrhage and 11 of spinal fracture. A total of 15 types of neurosurgical procedure were performed: six craniotomies for hematoma drainage, five craniotomies for elevation of depressed fractures, two procedures to allow placement of an intracranial pressure monitor, one to allow placement of an external ventricular drain, and one to allow the insertion of a ventriculoperitoneal shunt. Two patients had sustained spinal cord injury, and three procedures were performed for spinal decompression or stabilization. The duration of hospital stay ranged from 1 to 143 days (mean 6.6 days). Fifty-seven patients (30.8%) were eventually discharged from the hospital, three (1.6%) were transferred to another hospital, two (1.1%) died, and 123 (66.4%) required in-patient rehabilitation. CONCLUSIONS: Children suffered significant injuries due to ATV accidents. In passengers there was a statistically significant increased risk of neurological injury. The relative risk of neurological injury in patients not wearing helmets was higher than that in those who wore helmets, but the difference did not reach statistical significance. Further efforts must be made to improve the proper operation and safety of ATVs, both through the education of parents and children and through the creation of legislation requiring stricter laws concerning ATV use.

Early programmable valve malfunctions in pediatric hydrocephalus.

OBJECT: The use of adjustable differential pressure valves has been recommended to improve ventriculoperitoneal (VP) shunt performance in selected patients; however, published data are scarce regarding their clinical reliability. Recently, the identification of a number of malfunctioning programmable valves during shunt revision surgery in children prompted a retrospective review of valve performance in this patient cohort. METHODS: The authors performed a retrospective chart analysis of 100 patients with programmable valve shunts and 89 patients with nonprogrammable valve shunts implanted at the St. Louis Children's Hospital between April 2002 and June 2004. They noted the cause of hydrocephalus, the type of shunt malfunction, and cerebrospinal fluid (CSF) protein levels. Regular clinical follow up ranged from 1 to 26 months, with a mean follow-up time of 9.75 months for patients with programmable valves and 10.4 months for patients with nonprogrammable valves. Patient ages ranged from 2 weeks to 18 years. One hundred patients had 117 programmable valves implanted, and 35 of these patients (35%) underwent shunt revision because of malfunction. The programmable valve itself malfunctioned in nine patients who had undergone shunt revision (11.1%/year of follow up). The nonprogrammable valve group had no valve malfunctions. The overall VP shunt revision rate in the nonprogrammable valve group was 20.2%. No significant differences were identified when CSF protein levels and specific malfunction types were compared within the programmable valve and nonprogrammable valve groups. CONCLUSIONS: In this study the authors demonstrated an annualized intrinsic programmable valve malfunction rate of 11.1%, whereas during the same period no intrinsic valve malfunctions were noted with nonprogrammable valve systems for similar causes of hydrocephalus. The CSF protein levels did not correlate with observed valve malfunction rates. Further evaluation in a prospective, randomized fashion will elucidate specific indications for programmable valve systems and better determine the reliability of these valves in the pediatric population.

Incidental pediatric intraparenchymal xanthogranuloma: case report and review of the literature.

Juvenile xanthogranuloma (JXG) is a specialized form of non-Langerhans cell histiocyte proliferation that occurs in children. The majority of cases present as a solitary cutaneous lesion with a predilection for the head and neck region; however, isolated lesions occasionally have been identified in the central nervous system. The cutaneous forms of JXG usually follow a benign course. Other physicians have reported surgery as the first line of treatment in symptomatic patients with accessible lesions. Adjuvant therapies may be indicated for multicentric or surgically inaccessible lesions. The authors describe an unusual case of isolated intraparenchymal JXG in an asymptomatic child with no cutaneous manifestations and provide a review of the literature.

Surgical treatment of a lenticulostriate artery aneurysm. Case report.

Aneurysms arising from a lenticulostriate artery (LSA) are uncommon. Their causes include hypertension, moyamoya disease, infection, systemic lupus erythematosis, and flow-related saccular aneurysms. Options for treating these aneurysms are limited. The authors present a case in which an LSA aneurysm was identified in a 69-year-old woman with no significant medical history, who experienced a sudden onset of right hemiparesis and aphasia due to a basal ganglia hemorrhage. The different causes and treatment options available for these rare and difficult-to-treat aneurysms are discussed.

Safety and efficacy of concurrent interstitial radiation and hyperthermia in the treatment of progressive malignant brain tumors.

High activity 125I brachytherapy has efficacy in selected recurrent malignant brain tumors, but limited efficacy and risk of radiation necrosis have prompted investigation of additional adjunctive therapies. This study aims to assess the toxicity of interstitial conductive hyperthermia used concurrently with 125I brachytherapy for the treatment of recurrent brain malignancies. Twelve patients with recurrent malignant brain tumors were implanted using afterloading catheters intended to deliver 50 Gy at the isodose line encompassing the enhancing tumor with a 5-mm margin and heated to 41.5 degrees C for 48 h. The average implant volume was 18 cc with 5.3 catheters containing 9.4 sources with a total activity of 265 mCi. Serious toxicities included 8 motor deficits, 2 mood alterations, 4 seizures and 2 catheter wound cerebrospinal fluid leaks. Median survival was 10.35 months with the best responses being 6 with stable disease and 2 with partial responses. Reoperation rate for radiation necrosis was 33%. Concurrent conductive thermoradiotherapy is feasible but is associated with serious toxicity. There is no suggestion of improved survival with thermoradiotherapy over brachytherapy alone. Given the degree of toxicity observed, alternative approaches to improving local control of these tumors are being explored.

Intramedullary spinal cavernous malformation following spinal irradiation. Case report and review of the literature.

There is a growing body of evidence in the literature suggesting that cavernous malformations of the central nervous system may develop after neuraxis irradiation. The authors discuss the case of a 17-year-old man who presented with progressive back pain and myelopathy 13 years after undergoing craniospinal irradiation for a posterior fossa medulloblastoma. Spinal magnetic resonance (MR) imaging, performed at the time of his initial presentation with a medulloblastoma, demonstrated no evidence of a malformation. Imaging studies and evaluation of cerebrospinal fluid revealed no evidence of recurrence or dissemination. Spinal MR imaging demonstrated an extensive lesion in the thoracic spine with an associated syrinx suggestive of a cavernous malformation. A thoracic laminectomy was performed and the malformation was successfully resected. Pathological examination confirmed the diagnosis. The patient did well after surgery and was ambulating without assistance 6 weeks later. To the best of the authors' knowledge, this is the second reported case in the literature and the first in the young adult age group suggesting the de novo development of cavernous malformations in the spinal cord after radiotherapy. An increased awareness of these lesions and close follow-up examination are recommended in this setting.

Effect of spinal disease on successful arthrodesis in lumbar pedicle screw fixation.

OBJECT: Pedicle screw fixation with transverse process fusion has gained widespread acceptance since its inception. Improved rates of arthrodesis have been demonstrated when this technique is used. The authors present one of the largest series of patients to undergo this procedure at a single center; one of the goals was to correlate construct length and spinal disease with rates of successful arthrodesis by conducting a prospective analysis of lumbar fusion in which pedicle screws were placed. METHODS: During a 7-year period, the senior author performed pedicle screw fixation with posterolateral fusion in 457 patients; the mean follow-up period was 28.4 months. Indications for fusion included metastatic tumor, single-level degenerative disc disease (DDD), trauma, degenerative scoliosis, and translational vertebral instability. Successful fusion was based on the radiographic demonstration of a bilateral contiguous osseous bridge over the transverse processes and absence of movement on dynamic x-ray films. Fusion rates were lowest in cases of tumors (54%) and highest in cases of trauma (96%). In patients with single-level DDD the rate was 91%, and in those with translational instability it was 89%. Fusion rates, however, declined steeply in relation to each additional motion segment in the translational instability group. In this group a strong linear trend for proportion was demonstrated (p < 0.001). The overall fusion rate in patients with degenerative scoliosis was 70%. The overall fusion rate for the entire group was 86%. CONCLUSIONS: The data in this study can be used as a benchmark with which to compare newer technologies. Although overall pedicle screw-assisted fusion rate in cases of trauma or selected degenerative lesions approached 90%, the arthrodesis rates are not uniform for the different diagnoses. This appears to be related to the underlying spinal disease and the number of segments included in the fusion.

Stroke and pediatric human immunodeficiency virus infection. Case report and review of the literature.

Stroke is an uncommon complication in pediatric patients with acquired immunodeficiency syndrome (AIDS). However, with the increasing life span of this patient population, more cases of stroke are being reported. We report the case of a 13-year-old girl with a known history of AIDS who presented with new-onset seizures and right hemiparesis. Serial imaging studies revealed progressive occlusion of the left middle cerebral artery and both anterior cerebral arteries with development of collateral circulation. The workup for other etiologies of stroke was negative. This nonatherosclerotic occlusive disease is most likely secondary to vasculopathy caused by the human immunodeficiency virus (HIV). HIV infection should be included in the differential diagnosis of children who present with seizures, mental status change or focal neurological deficits. Treatment options are limited. The different prognoses associated with the etiologies of stroke in this patient population mandate a careful and thorough evaluation.