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.

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%.

3T intraoperative MRI for management of pediatric CNS neoplasms.

BACKGROUND AND PURPOSE: High-field-strength intraoperative MR imaging has emerged as a powerful adjunct for resection of brain tumors. However, its exact role has not been firmly established. We sought to determine the impact of 3T-intraoperative MRI on the surgical management of childhood CNS tumors. MATERIALS AND METHODS: We evaluated patient data from a single academic children's hospital during a consecutive 24-month period after installation of a 3T-intraoperative MRI. Tumor location, histology, surgical approach, operating room time, presence and volume of residual tumor, need for tumor and non-tumor-related reoperation, and anesthesia- and MR imaging-related complications were evaluated. Comparison with pre-intraoperative MRI controls was performed. RESULTS: One hundred ninety-four patients underwent intraoperative MRI-guided surgery. Of these, 168 were 18 years or younger (mean, 8.9 ± 5.0 years; 108 males/60 females). There were 65 posterior fossa tumors. The most common tumors were pilocytic astrocytoma (n = 31, 19%), low-grade glioma (n = 31, 19%), and medulloblastoma (n = 20, 12%). An average of 1.2 scanning sessions was performed per patient (maximum, 3). There were no MR imaging-related safety issues. Additional tumor was resected after scanning in 21% of patients. Among patients with a preoperative goal of gross total resection, 93% achieved this goal. The 30-day reoperation rate was <1% (n = 1), and no patient required additional postoperative MR imaging during the same hospital stay. CONCLUSIONS: Intraoperative MRI is safe and increases the likelihood of gross total resection, albeit with increased operating room time, and reduces the need for early reoperation or repeat sedation for postoperative scans in children with brain tumors.

MR imaging evaluation of inferior olivary nuclei: comparison of postoperative subjects with and without posterior fossa syndrome.

BACKGROUND AND PURPOSE: Posterior fossa syndrome is a severe postoperative complication occurring in up to 29% of children undergoing posterior fossa tumor resection; it is most likely caused by bilateral damage to the proximal efferent cerebellar pathways, whose fibers contribute to the Guillain-Mollaret triangle. When the triangle is disrupted, hypertrophic olivary degeneration develops. We hypothesized that MR imaging patterns of inferior olivary nucleus changes reflect patterns of damage to the proximal efferent cerebellar pathways and show association with clinical findings, in particular the presence or absence of posterior fossa syndrome. MATERIALS AND METHODS: We performed blinded, randomized longitudinal MR imaging analyses of the inferior olivary nuclei of 12 children with and 12 without posterior fossa syndrome after surgery for midline intraventricular tumor in the posterior fossa. The Fisher exact test was performed to investigate the association between posterior fossa syndrome and hypertrophic olivary degeneration on MR imaging. The sensitivity and specificity of MR imaging findings of bilateral hypertrophic olivary degeneration for posterior fossa syndrome were measured. RESULTS: Of the 12 patients with posterior fossa syndrome, 9 had bilateral inferior olivary nucleus abnormalities. The 12 patients without posterior fossa syndrome had either unilateral or no inferior olivary nucleus abnormalities. The association of posterior fossa syndrome and hypertrophic olivary degeneration was statistically significant (P < .0001). CONCLUSIONS: Hypertrophic olivary degeneration may be a surrogate imaging indicator for damage to the contralateral proximal efferent cerebellar pathway. In the appropriate clinical setting, bilateral hypertrophic olivary degeneration may be a sensitive and specific indicator of posterior fossa syndrome.

False lateralization of seizure onset by scalp EEG in neocortical temporal lobe epilepsy.

False lateralization of ictal onset by scalp EEG has been reported in patients with severe hippocampal sclerosis associated with hemispheric lesions or atrophy. There has been no report of cases of false lateralization by scalp EEG in patients without detectable structural abnormalities on MRI, or in patients with neocortical temporal lobe epilepsy. We report a case of false lateralization of ictal onset by scalp EEG in a patient with neocortical temporal lobe epilepsy and a normal MRI examination, investigated by intracranial EEG recordings. The ictal activity failed to propagate in the ipsilateral temporal lobe, but was strongly propagated to the contralateral temporal lobe resulting in a false lateralization of seizure onset by scalp EEG. It is possible that the poor homolateral propagation and evolution of ictal activity in this patient may be due to a functional rather than structural abnormality of the ipsilateral hippocampus, causing reduced synchrony and amplitude in the ipsilateral temporal cortex.

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.

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.

Long-term follow-up data from the Shunt Design Trial.

BACKGROUND: A previously reported multicenter randomized trial assessed whether 2 new shunt valve designs would reduce shunt failure rates compared to differential pressure valves. The study did not show a significant difference in the time to first shunt failure. Patients entered the trial between October 1, 1993, and October 31, 1995. The primary results were based on the patients' status as of October 31, 1996 (a minimum follow-up of 1 year). This report describes the late complications based on the patients' most recent follow-up. METHODS: Three hundred and forty-four hydrocephalic children at 12 North American and European centers were randomized to 1 of 3 valves: a standard differential pressure valve; a Delta valve (PS Medical-Medtronic) or a Sigma valve (NMT Cordis). Patients were followed until their first shunt failure. Shunt failure was defined as shunt surgery for obstruction, overdrainage, loculation or infection. If the shunt did not fail, follow-up was continued until August 31, 1999. RESULTS: One hundred and seventy-seven patients had shunt failure. Shunt obstruction occurred in 131, overdrainage in 13, loculated ventricles in 2 and infection in 29. The overall shunt survival was 62% at 1 year, 52% at 2 years, 46% at 3 years, 41% at 4 years. The survival curves for the 3 valves were similar to those from the original trial and did not show a survival advantage for any particular valve. CONCLUSIONS: Prolonged follow-up to date does not alter the primary conclusions of the trial: there does not appear to be one valve that is clearly the best for the initial treatment of pediatric hydrocephalus.

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.

Porcine small intestinal submucosa as a dural substitute.

BACKGROUND: The continuing search for the ideal dural substitute is currently directed toward collagen preparations. Xenogeneic porcine small intestinal submucosa (SIS), a naturally occurring extracellular matrix rich in collagen, has been successfully used as a soft tissue graft in several body organ systems, including preliminary studies as a dural substitute in the rat. METHODS: Eight dogs underwent temporoparietal craniotomy and dural resection with replacement by SIS. Five dogs had contralateral procedures without SIS grafting. Three dogs had contralateral SIS grafts placed 2 months after the initial procedure. Histologic assessment was obtained at 7, 30, 60, 90, and 120 days. Cerebrospinal fluid (CSF) cytological examination and routine serum chemistry preceded sacrifice. RESULTS: Histologic evaluation showed initial graft infiltration by mononuclear round cells, spindle-shaped cells within an eosinophilic staining extracellular matrix, and neovascularity. Complete resorption of the graft was evident by 60 days. This pattern is consistent with the previously described incorporation and remodeling of the SIS graft at other sites. CSF cytology and routine serum chemistry at the time of sacrifice were normal. Response to repeat grafting was identical to that of initial exposure. There was no clinical or histologic evidence of sensitization or graft rejection. No evidence of adverse effect on the underlying cerebral cortex was observed. CONCLUSIONS: Porcine small intestinal submucosa demonstrates a favorable biologic response as a dural substitute in the canine model. It is a promising biomaterial for dural replacement.

Spitting automatism in complex partial seizures: a nondominant temporal localizing sign?

PURPOSE: Spitting as an ictal automatism has been rarely reported. We aimed to establish its potential lateralizing and localizing significance. METHODS: Review of patients undergoing surgery for intractable epilepsy at two comprehensive epilepsy centers. RESULTS: Five patients were found who had spitting as a stereotyped automatism of their complex partial seizures. All had evidence of right temporal ictal onset and underwent resective surgery. Two had tumors; one, a cavernous angioma; one, hippocampal gliosis, and one, hippocampal sclerosis. We found no instances of ictal spitting in patients with left hemisphere onset. CONCLUSIONS: Spitting as an automatism in complex partial seizures, although uncommon, may be a localizing sign to the nondominant temporal lobe.

Cognition and behavior after temporal lobectomy in pediatric patients with intractable epilepsy.

The increased use of surgical intervention for intractable epilepsy during childhood has resulted in a critical need for information concerning possible cognitive and behavioral changes in pediatric patients after surgery. In this pilot study, comprehensive neuropsychologic evaluations were completed on nine children who had a temporal lobectomy for intractable epilepsy before 16 years of age. Performances before and after surgery were compared using cognitive and behavioral measures. Repeated measures analysis of variance did not indicate differences in performance on the basis of laterality of surgery, although the number of left (n = 5) vs right (n = 4) temporal resections was small. Paired comparison t tests, which included all patients, did not suggest marked changes in cognitive functioning after surgery, although decreases in delayed verbal memory were evident. Positive effects on quality of life during the first year after surgical intervention were suggested by reduced internalizing symptoms and increased social interaction. Replication of this study is recommended with a larger number of patients and multicenter collaboration.

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.

Neurologic injuries associated with all-terrain vehicles and recommendations for protective measures for the pediatric population.

OBJECTIVE: To present data and case studies illustrating the danger, especially in the pediatric population, of all-terrain vehicle (ATV) use, and to provide recommendations for pediatricians on how to educate parents concerning ATVs. DESIGN: Retrospective review of 33 patients with neurologic injuries sustained in ATV accidents presenting to one institution over a 40-month period. SETTING: Emergency department and neurosurgery service at Arkansas Children's Hospital and two other hospitals that make up the University of Arkansas for Medical Sciences. PATIENTS: All patients (n = 33) who presented between January 1993 and April 1996 at the emergency departments with neurologic injuries sustained in accidents involving either a three- or four-wheel ATV requiring hospitalization. INTERVENTIONS: Depending on the nature of the injury, various treatments, as described herein. MAIN OUTCOME MEASURES: Demographic measures, the mechanisms of injury, the types of injuries; the current data available regarding the number of injuries nationwide; and the precautionary measures parents should be advised to take. RESULTS: Ages ranged from four to 68 years (mean, 18; median, 14), 21 of the patients were < 16 years old. The predominant age range was 12 to 15 years; most common mechanisms of injury were being thrown to the ground, striking a tree, and flipping backward. Most injuries were cranial (21) or spinal (11). Nationwide, the proportionate number of injuries are decreasing, but the consequences remain severe. Using a helmet and restricting the use of these vehicles will reduce the number and magnitude of injuries. CONCLUSIONS: Although perceived as recreational toys, ATVs can be extremely unsafe, especially for children and adolescents; pediatricians should educate parents and patients on the dangers of riding these vehicles.

Decreased habituation of midlatency auditory evoked responses in Parkinson's disease.

The P1 midlatency auditory evoked potential was studied in patients with Parkinson's disease and compared to that in age-matched controls. Habituation of the potential was determined by using a two-click stimulus paradigm in which the stimuli were presented at 250-, 500-, and 1,000-ms interstimulus intervals. Results showed that habituation of the P1 potential had a statistically significant decrease at the 250-ms and 500-ms interstimulus intervals in patients with Parkinson's disease compared to normal controls. The degree of decreased habituation was found to increase with severity of the disease such that stage 5 patients showed greater decreases in habituation compared to stage 4, as did stage 4 compared to stage 3. These findings may be explained by the presence of a dysregulation of sensory processing, possibly by elements of the reticular activating system, including the pedunculopontine nucleus, in Parkinson's disease.

Fourth ventricular ependymoma in a child with Duane retraction syndrome.

A child with unilateral Duane retraction syndrome developed signs and symptoms of increased intracranial pressure at 3 1/2 years of age. Neuroimaging disclosed a fourth ventricular ependymoma compressing but not invading the floor of the fourth ventricle. The coexistence of Duane syndrome and fourth ventricular ependymoma in a young child raises the possibility that both conditions could have resulted from a mutational event or focus of cellular disorganization (i.e. field defect) localized to the dorsal pons.