Anatomic Neuroimaging Characteristics of Posterior Fossa Type A Ependymoma Subgroups.

BACKGROUND AND PURPOSE: Posterior fossa type A (PFA) ependymomas have 2 molecular subgroups (PFA-1 and PFA-2) and 9 subtypes. Gene expression profiling suggests that PFA-1 and PFA-2 tumors have distinct developmental origins at different rostrocaudal levels of the brainstem. We, therefore, tested the hypothesis that PFA-1 and PFA-2 ependymomas have different anatomic MR imaging characteristics at presentation. MATERIALS AND METHODS: Two neuroradiologists reviewed the preoperative MR imaging examinations of 122 patients with PFA ependymomas and identified several anatomic characteristics, including extension through the fourth ventricular foramina and encasement of major arteries and tumor type (midfloor, roof, or lateral). Deoxyribonucleic acid methylation profiling assigned ependymomas to PFA-1 or PFA-2. Information on PFA subtype from an earlier study was also available for a subset of tumors. Associations between imaging variables and subgroup or subtype were evaluated. RESULTS: No anatomic imaging variable was significantly associated with the PFA subgroup, but 5 PFA-2c subtype ependymomas in the cohort had a more circumscribed appearance and showed less tendency to extend through the fourth ventricular foramina or encase blood vessels, compared with other PFA subtypes. CONCLUSIONS: PFA-1 and PFA-2 ependymomas did not have different anatomic MR imaging characteristics, and these results do not support the hypothesis that they have distinct anatomic origins. PFA-2c ependymomas appear to have a more anatomically circumscribed MR imaging appearance than the other PFA subtypes; however, this needs to be confirmed in a larger study.

Diffusion tensor imaging of tract involvement in children with pontine tumors.

BACKGROUND AND PURPOSE: Conventional MR imaging permits subcategorization of brain stem tumors by location and focality; however, assessment of white matter tract involvement by tumor is limited. Diffusion tensor imaging (DTI) is a promising method for visualizing white matter tract tumor involvement supratentorially. We investigated the ability of DTI to visualize and quantify white matter tract involvement in pontine tumors. METHODS AND MATERIALS: DTI data (echo-planar, 1.5T) were retrospectively analyzed in 7 patients with pontine tumors (6 diffuse, 1 focal), 4 patient controls, and 5 normal volunteers. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were calculated from the diffusion tensor in 6 regions of interest: bilateral corticospinal tracts, transverse pontine fibers, and medial lemnisci. Relationships between FA and ADC values and results of the neurologic examinations were evaluated. RESULTS: The corticospinal tracts and transverse pontine fibers were affected more often than the medial lemnisci. The DTI parameters (FA and ADC) were significantly altered in all tracts of patients with pontine tumors (P < .05), compared with those values in the control groups. A marginally significant (P = .057) association was seen between the severity of cranial nerve deficit and decreased FA. CONCLUSION: DTI provided superior visualization and quantification of tumor involvement in motor, sensory, and transverse pontine tracts, compared with information provided by conventional MR imaging. Thus, DTI may be a sensitive measure of tract invasion. Further prospective studies are warranted to assess the ability of DTI to delineate tumor focality and improve risk stratification in children with pontine tumors.

Postoperative intraspinal subdural collections after pediatric posterior fossa tumor resection: incidence, imaging, and clinical features.

BACKGROUND AND PURPOSE: Postoperative intraspinal subdural collections in children after posterior fossa tumor resection may temporarily hinder metastasis detection by MR imaging or CSF analysis, potentially impacting therapy. We investigated the incidence, imaging and clinical features, predisposing factors, and time course of these collections after posterior fossa tumor resection. MATERIALS AND METHODS: Retrospective review of postoperative spine MRI in 243 children (5.5 ± 4.6 years of age) from our clinical data base postresection of posterior fossa tumors from October 1994 to August 2010 yielded 37 (6.0 ± 4.8 years of age) subjects positive for postoperative intraspinal subdural collections. Their extent and signal properties were recorded for postoperative (37/37), preoperative (15/37), and follow-up spine (35/37) MRI. Risk factors were compared with age-matched internal controls (n = 37, 5.9 ± 4.5 years of age). Associations of histology, hydrocephalus and cerebellar tonsillar herniation, and postoperative intracranial subdural collections with postoperative intraspinal subdural collections were assessed by the Fisher exact test or χ(2) test. The association between preoperative tumor volume and postoperative intraspinal subdural collections was assessed by the Wilcoxon rank sum test. RESULTS: The overall incidence of postoperative intraspinal subdural collections was 37/243 (15.2%), greatest ≤7 days postoperatively (36%); 97% were seen 0-41 days postoperatively (12.9 ± 11.0 days). They were T2 hyperintense and isointense to CSF on T1WI, homogeneously enhanced, and resolved on follow-up MR imaging (35/35). None were symptomatic. They were associated with intracranial subdural collections (P = .0011) and preoperative tonsillar herniation (P = .0228). CONCLUSIONS: Postoperative intraspinal subdural collections are infrequent and clinically silent, resolve spontaneously, and have a distinctive appearance. Preoperative tonsillar herniation appears to be a predisposing factor. In this series, repeat MR imaging by 4 weeks documented improvement or resolution of these collections in 88%.

Chromosome aberrations in four ependymomas.

Cytogenetic analysis of short-term cultures from three untreated and one recurrent ependymoma revealed clonal aberrations in three of the four tumors. A posterior fossa ependymoma from a 3-year-old male patient showed trisomy 11 as the sole clonal chromosome aberration. A recurrent spinal ependymoma from a 35-year-old male showed hypertriploid clones with abnormalities involving chromosomes 1p11,7q21, and 10p13. A 62-year-old male patient with a cerebellar ependymoma showed a hypodiploid stem-cell line with clonal structural aberrations of both the long and short arms of chromosome 1, an interstitial deletion of 2q, trisomy 7, and monosomy for chromosomes 11, 13, and 16. A 3-year-old female patient with posterior fossa ependymoma showed a normal 46,XX karyotype. Chromosome 1 aberrations appear to be the most consistent finding in this small series of tumors, with the net loss or rearrangement of chromosome 1 pter-->p22 material from two of the four tumors. These findings, in addition to a previously published case [1], suggest a possible role for genes on the short arm of chromosome 1 in the cytogenetic evaluation of ependymomas.

Telomeric associations evolving to ring chromosomes in a recurrent pleomorphic xanthoastrocytoma.

Telomeric associations observed in a recurrent untreated pleomorphic xanthoastrocytoma were apparently the primary cytogenetic events that evolved by fusion and breakage events, resulting in subclones with ring chromosomes. The telomeric fusions between chromosomes 15pter and 20qter, and between an extra copy of the long arm of chromosome 1 and chromosome 22qter, evolved in a stepwise fashion to ring chromosomes 20 and 22. The findings in this tumor demonstrate that telomeric association is one mechanism that can initiate chromosome instability by generating subclones with unstable chromosome intermediates and result in ring chromosomes and subsequent chromosome loss.

Cytogenetic findings in a pleomorphic xanthoastrocytoma.

We report a pleomorphic xanthoastrocytoma with an abnormal clonal cell line of 48,XY, +3, +5, -20, -22, +der(7)t(7;?)(p22;?), +der(20)t(15;20)(q11;q13).

Molecular cytogenetic analysis of a medulloblastoma with isochromosome 17 and double minutes.

Cytogenetic analysis of a medulloblastoma revealed two abnormal cell lines of 48,XY, +8, +8, -14, +der(14)t(1;14)(q11;p11),i(17q) and 51,XY, +5, +6, +8, +8, -14 + 20, +der (14)t(1;14)(q11;p11),i(17q), + dmin. The finding of double minute chromosomes in some medulloblastomas has been associated with amplification of the c-myc or N-myc oncogenes. We were unable to detect gene amplification with these probes by Southern blot analysis.

Proliferation of astroglia from the adult human cerebrum is inhibited by ethanol in vitro.

Chronic alcoholism is associated with atrophy of the adult brain, while fetal exposure to ethanol can cause microencephaly. Since astroglial pathology is a common feature of ethanol exposure in both humans and animal models, the direct influence of ethanol on proliferation of human astroglia from the gray and white matter of adult temporal lobe was determined and compared. Astroglial cultures were exposed to constant concentrations of ethanol at realistic social and clinical levels (0.1, 0.2 or 0.5%; w/v) for 1 to 5 days. Proliferation was quantified by bromodeoxyuridine labeling and enumeration of replicating cells. Ethanol exposure significantly inhibited proliferation of both gray and white matter astroglia in a dose and duration dependent manner. Gray matter was slightly more sensitive than white matter to inhibition by low to moderate concentrations of ethanol; in contrast, white matter was more sensitive to high ethanol concentrations. Maximum inhibition was 20% in gray matter and 25% in white matter. Human astroglial proliferation was directly inhibited in the absence of neurons, microglia, neuronal degeneration or systemic factors that have confounded in vivo studies. Restricted astroglial proliferation may underlie aspects of the astroglial pathology associated with ethanol exposure.

Heterogeneity of astroglia cultured from adult human temporal lobe.

This study characterized the morphological and electrophysiological diversity of astroglia cultured from adult human cerebral temporal lobe, and explored the influence of the cytokine interleukin-1beta on these cells. The cultures contained astroglia positive for glial fibrillary acidic protein which were flat, bipolar or multipolar in shape and variable in size. A subpopulation of the bipolar and multipolar cells was positive for S100 protein. The most striking feature of these cultures was the presence of glia with long (600 micrometer) processes with few branches or only terminal branches. Patch clamp recordings of the non-stellate process bearing cells revealed prominent inward Na(+) and transient and sustained outward K(+) conductances. Distinct differences in the relative proportion of these conductances were evident among cells but did not appear to be correlated with cell morphology. Treatment of cultures with interleukin-1beta for 96 h did not change total protein content, but increased the content of S100beta protein and decreased the content of glial fibrillary acidic protein. The findings indicate that cultures of adult human cerebrum contain subpopulations of morphologically and electrophysiologically pleomorphic glial fibrillary acidic protein positive astroglia, exhibit increased levels of the neurotrophic factor S100beta when exposed to interleukin-1beta, and may serve as a useful model for investigation of glial involvement in neuropathology.

Meningiomas in children: MR and histopathologic findings.

PURPOSE: To present the MR and histopathologic findings in five children with meningiomas. METHODS: Five children aged 3 months to 16 years with pathologically proved meningiomas underwent preoperative contrast enhanced MR. Tissue in four patients was sent for chromosomal analysis in addition to routine histopathologic studies. RESULTS: All five tumors were extra-axial, two supratentorial and three in the posterior fossa. MR showed variable signal intensity on precontrast T1-weighted images. All of the tumors were hyperintense on proton density- and T2-weighted images and showed intense contrast enhancement. Histopathologic analysis showed two meningotheliomatous, one transitional, one chordoid, and one hemangiopericytic variant of meningioma. Chromosomal analysis showed deletions involving chromosome 22 in two of four tumors studied. CONCLUSION: Meningiomas in children have a higher incidence of posterior fossa location and different histologic types than seen in adults. MR showed the tumors in our patients to be extra-axial, hyperintense on proton density- and T2-weighted images with intense enhancement on postcontrast T1-weighted images. Chromosomal aberrations were noted in two patients.

A middle-latency auditory-evoked potential in the rat.

Previous studies have established the presence of a middle-latency auditory-evoked potential that is characterized by a) sleep-state dependence, b) low following frequency (i.e., rapid habituation to repetitive stimulation), and c) blockade by the cholinergic antagonist, scopolamine. A vertex-recorded evoked potential having these characteristics was described in humans at a 50-80 ms latency (termed the P1 or.P50 potential) and in the cat at a 20-25 ms latency (termed wave A). These studies were undertaken to determine if a click stimulus-evoked potential having the same characteristics was present in the intact rat. Vertex and auditory cortex recordings in intact rats studied in a sound-attenuating chamber and exposed to free-field click stimuli showed a) the presence of a vertex recorded potential at a 11-15 ms latency, termed P13, and of an auditory cortex recorded potential at a 7-11 ms latency, termed Pa; b) the P13 was present during waking and paradoxical sleep but absent in slow-wave sleep, while Pa was present in all sleep-wake states; c) the P13 habituated markedly at stimulation rates above 1 Hz while Pa did not; and d) the P13 was blocked by low doses of scopolamine while Pa was not. These studies demonstrate the presence of a P1-like potential in the rat at a 13 +/- 2 ms latency.

Spontaneous spinal subdural hematoma: case report and review of the literature.

We report the case of a pediatric patient with a spontaneous spinal subdural hematoma that was not associated with a coagulation abnormality. Six cases have been reported previously. The patient improved after surgical drainage. The possible causes of this rare problem are discussed.

Silastic duraplasty in pediatric patients.

The role of adhesions in the retethering of the neural elements after surgical treatment of spinal dysraphism has produced refinements in the technique of the closure of the neural tube. Silastic, because of its relative inert property, has been used for duraplasty, but a few reports of late complications of hemorrhage or fibrotic capsule formation have caused concern over its use. We report 33 patients with the following diagnoses--eight spinal lipomyelomeningoceles, three myelomeningoceles, six symptomatic Chiari II malformations, seven tethered cords, six spinal cord tumors, two diastematomyelia, and one cerebellar astrocytoma--in whom Silastic dural grafts were used to prevent the adherence of neural structures to the overlying tissues. Our surgical technique is presented here. The patients have been observed for up to 6 years. Only one became infected, was treated with antibiotics without graft removal, and has remained without sequelae for over 3 years. One had an incidental pseudomeningocele that was noted on follow-up magnetic resonance imaging scan that was not clinically apparent. There have been no hemorrhages, leakage of cerebrospinal fluid, nor other complications from using nonreinforced Silastic sheeting. In one patient, Dacron-reinforced Silastic was used and, upon reexploration, a marked fibroblastic response was noted. A review of the literature suggests that fibrotic complications are related to this Dacron-reinforced Silastic. The hemorrhagic complications that were reported occurred in instances where Silastic grafts were large and no technical modifications were made preventively. We conclude that the use of nonreinforced Silastic dural grafts, with appropriate technical modifications in surgical technique, is safe and may prevent retethering of neural tissues in a variety of neurosurgical lesions.

The subarachnoid spaces in craniosynostosis.

A review of 85 patients with various forms of craniosynostosis showed predictable patterns of dilatation of the subarachnoid spaces in regions of compensatory skull growth. The characteristic pattern in sagittal synostosis (43 patients) included dilatation of the frontal and occipital subarachnoid spaces associated with the elongation of the anteroposterior dimension of the skull and widening of the interhemispheric fissure. In 11 patients with unilateral coronal synostosis, dilatations of the subarachnoid spaces over the contralateral frontal lobe, the sylvian regions, and the ipsilateral temporal lobe tip were consistent with the skull changes of contralateral frontal bossing, increased bitemporal dimension, and elevation of the sphenoid wing, respectively. Four patients with bilateral coronal synostosis also had enlarged subarachnoid spaces high over the convexities of the brain consistent with the towering configuration of the skull. Four patients with true lambdoid synostosis had dilatation of the subarachnoid space only over the ipsilateral frontal lobe associated with compensatory bossing of the frontal bone. Ten of 14 patients with lambdoid deformities had bilateral enlargement of the subarachnoid spaces suggesting brain atrophy and an underlying motor delay accounting for the position-induced skull changes. The findings suggest that focal hydrodynamic mechanisms are involved in the compensatory skull changes seen in craniosynostosis.

Meningioma and sagittal craniosynostosis in an infant: case report.

The occurrence of a frontal base meningioma in a 3-month-old infant seen for the treatment of sagittal craniosynostosis is reported. The association of the two lesions is of interest both because it is unique and may lend support to theories of the cause of some forms of craniosynostosis.

Randomized trial of cerebrospinal fluid shunt valve design in pediatric hydrocephalus.

OBJECTIVE: Forty percent of standard cerebrospinal fluid shunts implanted for the treatment of pediatric hydrocephalus fail within the first year. Two new shunt valves designed to limit excess flow, particularly in upright positions, were studied to compare treatment failure rates with those for standard differential-pressure valves. METHODS: Three hundred-forty-four hydrocephalic children (age, birth to 18 yr) undergoing their first cerebrospinal fluid shunt insertion were randomized at 12 North American or European pediatric neurosurgical centers. Patients received one of three valves, i.e., a standard differential-pressure valve; a Delta valve (Medtronic PS Medical, Goleta, CA), which contains a siphon-control component designed to reduce siphoning in upright positions; or an Orbis-Sigma valve (Cordis, Miami, FL), with a variable-resistance, flow-limiting component. Patients were monitored for a minimum of 1 year. Endpoints were defined as shunt failure resulting from shunt obstruction, overdrainage, loculations of the cerebral ventricles, or infection. Outcome events were assessed by blinded independent case review. RESULTS: One hundred-fifty patients reached an endpoint; shunt obstruction occurred in 108 (31.4%), overdrainage in 12 (3.5%), loculated ventricles in 2 (0.6%), and infection in 28 (8.1%). Sixty-one percent were shunt failure-free at 1 year and 47% at 2 years, with a median shunt failure-free duration of 656 days. There was no difference in shunt failure-free duration among the three valves (P = 0.24). CONCLUSION: Cerebrospinal fluid shunt failure, predominantly from shunt obstruction and infection, remains a persistent problem in pediatric hydrocephalus. Two new valve designs did not significantly affect shunt failure rates.

Outcome analysis of 85 patients undergoing the pi procedure for correction of sagittal synostosis.

The authors present a retrospective review of their experience with 85 cases using the pi procedure to correct sagittal synostosis. A male preponderance of four to one was recognized in this group. Sixty-five infants underwent computerized tomography scanning of the head prior to surgery; these scans revealed unexpected intracranial pathology in 5% of cases. Surgical complications included three intraoperative dural lacerations. All children received blood transfusions with no complications. Cosmetic outcomes were excellent in 53%, good in 43%, and poor in 4% of cases. One patient required reoperation. All poor outcomes were in infants who were younger than 8 weeks of age at the time of surgery and who underwent a "reverse pi" procedure. Most of the excellent outcomes occurred in infants who were between 3 and 6 months of age at the time of surgery. Although more extensive than strip craniectomy, the pi procedure can be accomplished with minimal morbidity. In the authors' opinion, the pi procedure provides better immediate and long-term cosmetic results than synostectomy alone.

Involution of enhancing intrinsic tectal tumors after endoscopic third ventriculostomy. Report of two cases.

For benign intrinsic tectal tumors causing triventricular obstructive hydrocephalus, cerebrospinal fluid diversion followed by neuroimaging is a widely accepted treatment plan. In this report, the authors describe two children with focal enhancing tectal lesions that caused acute, symptomatic hydrocephalus. One child had neurofibromatosis Type 1 (NF1). In both children the hydrocephalus was effectively treated by endoscopic third ventriculostomy. Following this procedure, serial imaging studies revealed not only that the ventriculomegaly had resolved, but also that the enhancing tectal tumors had regressed and disappeared over time. The time to complete involution of these tumors was 18 months for the child with NF1 and 12 months for the other child. To the authors' knowledge, this is the first report of the involution of enhancing tectal tumors after endoscopic third ventriculostomy. The possible mechanisms for this unexpected result are discussed.

Inside-outside technique for posterior occipitocervical spine instrumentation and stabilization: preliminary results.

OBJECT: The authors present a series of 16 patients who underwent inside-outside occipital and posterior cervical spine stabilization. METHODS: In this technique, the screw was placed from the inside of the occiput to the outside. An articular (lateral) mass plate was contoured to the shape of the occipital bone and the cervical spine and affixed to the occiput with a flat-headed screw or stud placed through a burr hole in the calvaria with the flat head of the screw in the epidural space and the threads facing outward. The bone plate was then secured with a nut to the occipital screw and the cervical plate was attached to the spine with a bone screw that coursed through the plate and into the articular pillar. Our series included six children and 10 adults. In five patients, previous fusion had failed; in two patients spinal instability was secondary to Down's syndrome; two patients' instability was related to developmental anomalies; and in five patients spinal instability was due to the presence of tumor. One patient with rheumatoid arthritis had undergone a transoral procedure. Two patients had suffered traumatic fracture. Three patients died of causes unrelated to the procedure, one patient died of metastatic cancer, and one patient died in a long term care facility of cardiopulmonary complications. One patient with renal failure suffered a hemorrhage from an arteriovenous fistula after being treated with dialysis. In one child, a nut backed off after 3 months. The nut was reseated, and a maturing arthrodesis was present. CONCLUSIONS: The authors conclude that the inside-outside occipitocervical fixation is an effective technique for stabilizing the cervical spine.

Combat veterans with posttraumatic stress disorder exhibit decreased habituation of the P1 midlatency auditory evoked potential.

The current study used a paired stimulus paradigm to investigate the P1 midlatency auditory evoked potential in Vietnam combat veterans with posttraumatic stress disorder (PTSD) and three comparison groups: alcohol dependents, combat-exposed normals, and combat-unexposed normals. Compared to each comparison group, PTSD subjects exhibited significantly diminished habituation of the P1 potential. P1 potential habituation within the PTSD group, correlated significantly with intensity of PTSD reexperiencing symptoms, such as trauma-related nightmares and flashbacks. These findings are discussed as consistent with a sensory gating defect at the brainstem level in PTSD, and are further discussed in the context of other psychophysiological measures in PTSD and of P1 potential findings in psychiatric disorders other than PTSD.