Chasing language through the brain: Successive parallel networks

OBJECTIVE

To describe the spatio-temporal dynamics and interactions during linguistic and memory tasks.

METHODS

Event-related electrocorticographic (ECoG) spectral patterns obtained during cognitive tasks from 26 epilepsy patients (aged: 9-60 y) were analyzed in order to examine the spatio-temporal patterns of activation of cortical language areas. ECoGs (1024 Hz/channel) were recorded from 1567 subdural electrodes and 510 depth electrodes chronically implanted over or within the frontal, parietal, occipital and/or temporal lobes as part of their surgical work-up for intractable seizures. Six language/memory tasks were performed, which required responding verbally to auditory or visual word stimuli. Detailed analysis of electrode locations allowed combining results across patients.

RESULTS

Transient increases in induced ECoG gamma power (70-100 Hz) were observed in response to hearing words (central superior temporal gyrus), reading text and naming pictures (occipital and fusiform cortex) and speaking (pre-central, post-central and sub-central cortex).

CONCLUSIONS

Between these activations there was widespread spatial divergence followed by convergence of gamma activity that reliably identified cortical areas associated with task-specific processes.

SIGNIFICANCE

The combined dataset supports the concept of functionally-specific locally parallel language networks that are widely distributed, partially interacting in succession to serve the cognitive and behavioral demands of the tasks.

Diagnostic Accuracy of Non-Invasive Thermal Evaluation of Ventriculoperitoneal Shunt Flow in Shunt Malfunction: A Prospective, Multi-Site, Operator-Blinded Study

BACKGROUND

Thermal flow evaluation (TFE) is a non-invasive method to assess ventriculoperitoneal shunt function. Flow detected by TFE is a negative predictor of the need for revision surgery. Further optimization of testing protocols, evaluation in multiple centers, and integration with clinical and imaging impressions prompted the current study.

OBJECTIVE

To compare the diagnostic accuracy of 2 TFE protocols, with micropumper (TFE+MP) or without (TFE-only), to neuro-imaging in patients emergently presenting with symptoms concerning for shunt malfunction.

METHODS

We performed a prospective multicenter operator-blinded trial of a consecutive series of patients who underwent evaluation for shunt malfunction. TFE was performed, and preimaging clinician impressions and imaging results were recorded. The primary outcome was shunt obstruction requiring neurosurgical revision within 7 d. Non-inferiority of the sensitivity of TFE vs neuro-imaging for detecting shunt obstruction was tested using a prospectively determined a priori margin of −2.5%.

RESULTS

We enrolled 406 patients at 10 centers. Of these, 68/348 (20%) evaluated with TFE+MP and 30/215 (14%) with TFE-only had shunt obstruction. The sensitivity for detecting obstruction was 100% (95% CI: 88%-100%) for TFE-only, 90% (95% CI: 80%-96%) for TFE+MP, 76% (95% CI: 65%-86%) for imaging in TFE+MP cohort, and 77% (95% CI: 58%-90%) for imaging in the TFE-only cohort. Difference in sensitivities between TFE methods and imaging did not exceed the non-inferiority margin.

CONCLUSION

TFE is non-inferior to imaging in ruling out shunt malfunction and may help avoid imaging and other steps. For this purpose, TFE only is favored over TFE+MP.

Dural Ectasia in Neurofibromatosis 1: Case Series, Management, and Review

BACKGROUND

The natural history and management of dural ectasia in Neurofibromatosis 1 (NF1) is still largely unknown. Dural ectasias are one of the common clinical manifestations of NF1; however, the treatment options for dural ectasias remain unstudied.

OBJECTIVE

To investigate the natural history, diagnosis, management, and outcome of the largest case series of patients with NF1-associated dural ectasia to date.

METHODS

Records from our NF1 clinic were reviewed to identify NF1 patients with computed tomography or magnetic resonance imaging evidence of dural ectasia(s) to determine their clinical course. Demographics, symptoms, radiographic and histopathologic findings, treatment, and clinical course were assessed.

RESULTS

Thirty-four of 37 patients were managed without surgery. Of the 18 initially asymptomatic patients, 5 (27.8%) progressed to symptoms attributable to a dural ectasia (onset of 2.7% per patient-year). Three patients required surgical intervention because of extraspinal mass effect. All 3 initially improved but had symptom recurrence within 2 yr. Reoperation involved shunt placement for cerebrospinal fluid (CSF) diversion. On imaging review, 26 (76.5%) of the nonsurgical patients harbored an associated nearby plexiform neurofibroma. Pathology of one surgical case revealed dural infiltration by diffuse neurofibroma.

CONCLUSION

Using the largest NF1-associated dural ectasia group to date, we report the first symptom-onset rate for nonsurgical patients. In the few cases requiring surgery for decompression, primary resection, and patching of ectasias failed, subsequently requiring CSF shunting. We demonstrate imaging evidence of nearby plexiform neurofibroma in a majority of cases, which, when combined with histopathology, provides a novel explanation for the formation of dural ectasias.

Outcomes in children undergoing posterior fossa decompression and duraplasty with and without tonsillar reduction for Chiari malformation type I and syringomyelia: a pilot prospective multicenter cohort study

OBJECTIVE

Despite significant advances in diagnostic and surgical techniques, the surgical management of Chiari malformation type I (CM-I) with associated syringomyelia remains controversial, and the type of surgery performed is surgeon dependent. This study's goal was to determine the feasibility of a prospective, multicenter, cohort study for CM-I/syringomyelia patients and to provide pilot data that compare posterior fossa decompression and duraplasty (PFDD) with and without tonsillar reduction.

METHODS

Participating centers prospectively enrolled children suffering from both CM-I and syringomyelia who were scheduled to undergo surgical decompression. Clinical data were entered into a database preoperatively and at 1-2 weeks, 3-6 months, and 1 year postoperatively. MR images were evaluated by 3 independent, blinded teams of neurosurgeons and neuroradiologists. The primary endpoint was improvement or resolution of the syrinx.

RESULTS

Eight clinical sites were chosen based on the results of a published questionnaire intended to remove geographic and surgeon bias. Data from 68 patients were analyzed after exclusions, and complete clinical and imaging records were obtained for 55 and 58 individuals, respectively. There was strong agreement among the 3 radiology teams, and there was no difference in patient demographics among sites, surgeons, or surgery types. Tonsillar reduction was not associated with > 50% syrinx improvement (RR = 1.22, p = 0.39) or any syrinx improvement (RR = 1.00, p = 0.99). There were no surgical complications.

CONCLUSIONS

This study demonstrated the feasibility of a prospective, multicenter surgical trial in CM-I/syringomyelia and provides pilot data indicating no discernible difference in 1-year outcomes between PFDD with and without tonsillar reduction, with power calculations for larger future studies. In addition, the study revealed important technical factors to consider when setting up future trials. The long-term sequelae of tonsillar reduction have not been addressed and would be an important consideration in future investigations.

Whole-Proteome Analysis of Human Craniosynostotic Tissue Suggests a Link between Inflammatory Signaling and Osteoclast Activation in Human Cranial Suture Patency

BACKGROUND

The pathophysiology of nonsyndromic craniosynostosis remains poorly understood. The authors seek to understand the cause of this condition with a specific focus on how osteoclasts may contribute to craniosynostosis. Here, the authors characterize proteins differentially expressed in patent and fused cranial sutures by comparing their respective proteomes.

METHODS

Fused and patent suture samples were obtained from craniosynostotic patients undergoing surgery at a single academic medical center. Extracted protein from samples was interrogated using mass spectrometry. Differential protein expression was determined using maximum likelihood-based G-test with a q-value cutoffs of 0.5 after correction for multiple hypothesis testing. Immunolocalization of lead protein candidates was performed to validate proteomic findings. In addition, quantitative polymerase chain reaction analysis of corresponding gene expression of proteins of interest was performed.

RESULTS

Proteins differentially expressed in patent versus fused sutures included collagen 6A1 (Col6A1), fibromodulin, periostin, aggrecan, adipocyte enhancer-binding protein 1, and osteomodulin (OMD). Maximum likelihood-based G-test suggested that Col6A1, fibromodulin, and adipocyte enhancer-binding protein 1 are highly expressed in patent sutures compared with fused sutures, whereas OMD is up-regulated in fused sutures compared with patent sutures. These results were corroborated by immunohistochemistry. Quantitative polymerase chain reaction data point to an inverse relationship in proteins of interest to RNA transcript levels, in prematurely fused and patent sutures that potentially describes a feedback loop mechanism.

CONCLUSIONS

Proteome analysis validated by immunohistochemistry may provide insight into the mechanism of cranial suture patency and disease from an osteoclast perspective. The authors results suggest a role of inflammatory mediators in nonsyndromic craniosynostosis. Col6A1 may aid in the regulation of suture patency, and OMD may be involved in premature fusion. Additional validation studies are required.

Prevalence of Psychiatric Diagnoses in Pediatric Chiari Malformation Type 1

This cross-sectional study investigates the prevalence and risks for psychiatric diagnoses in a large cohort of children with Chiari malformation type 1 (CM1) presenting for neurosurgical evaluation. Children between the ages of 6 and 17 years who were evaluated and diagnosed with CM1 at a neurosurgery clinic were identified. Eighty-six participants were recruited for this study with an average age of 11 years. Parents of participants completed a pediatric medical history questionnaire and a semistructured interview regarding the child's psychiatric, developmental, medical, and family history. A review of medical records was completed to complement interview data. Elevated rates of psychiatric diagnoses, including attention deficit hyperactivity disorder (ADHD) (22.1%), anxiety (12.8%), and depression (10.5%), were identified in the study population when compared to published norms in the general population documented by the American Psychiatric Association in 2013. In addition, elevated rates of psychiatric diagnoses in first-degree relatives of study participants were also identified. A 2-step binary logistic regression analysis revealed that maternal complications during pregnancy (Wald = 6.52, p = 0.01) increased the risk of a psychiatric diagnosis 9-fold. Premature birth (Wald = 6.79, p = 0.01) also significantly predicted a psychiatric diagnosis amongst participants. The current findings suggest a high prevalence of psychiatric illness in children with CM1. Pregnancy complications were associated with a high risk of a psychiatric diagnosis. Early CNS developmental disturbance may explain this relationship. Prematurity only slightly improved the prediction model. Limitations and future directions are discussed, including the cross-sectional nature of the present study, possible self-selection bias, and the importance of future investigation of other causative and/or associative factors of CM1, such as cognitive, psychiatric, and medical influences on health status.

Magnetic resonance imaging in the prone position and the diagnosis of tethered spinal cord

OBJECTIVE Tethered cord syndrome (TCS) is a neurosurgical disorder with varied clinical manifestations believed to result from vascular compromise due to stretch forces on the spinal cord. Conventional supine MRI findings may include a low-lying conus medullaris, thickened or fat-infiltrated filum terminale, or lipoma; however, imaging sensitivity and specificity for tethered cord can be low. The purpose of this study was to evaluate the utility of prone MRI in the diagnosis of tethered and retethered spinal cord. METHODS Medical records were reviewed in 41 patients who underwent surgical release of tethered cord and in whom preoperative prone MRI sequences were available. Patients were divided into Group 1 (new TCS diagnosis) and Group 2 (recurrent TCS after previous untethering). Absolute conus ventral motion and motion as a percentage of canal width between supine and prone positions was measured in these 2 groups via sagittal T2-weighted sequences; these groups were compared with 30 consecutive patients (Group 3) who were classified as the normal control group. RESULTS The mean ventral motion was as follows: Group 1 (absolute: 0.5 ± 0.5 mm [range 0-2.4 mm]; canal percentage: 3.7% ± 3.9% [range 0%-16.3%]); Group 2 (absolute: 0.4 ± 0.7 mm [range 0-2.6 mm]; canal percentage: 2.2% ± 3.7% [range 0%-14.0%]); and Group 3 (absolute: 3.4 ± 1.3 mm [range 1.4-5.6 mm]; canal percentage: 22.0% ± 7.2% [range 10.5%-36.1%]). Whereas 38/41 surgically treated patients with TCS had diminished (< 10% canal width) ventral motion on preoperative MRI, 30/30 controls had > 10% canal width motion. Sensitivity and specificity were thereby calculated as 92.7% and 100%, respectively. CONCLUSIONS In the present series, prone imaging is found to be a sensitive and specific tool, and the authors believe it may have a role as supportive evidence in the diagnosis of tethered and retethered spinal cord.

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

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

Transcardiac migration of ventriculoperitoneal shunt requiring open cardiac surgery: case report and review of the literature

INTRODUCTION

Cardiac migration of ventriculoperitoneal (VP) shunts has been reported, with most easily removed or shortened via a cervical incision. We present a review of the literature, highlighting our unique case with significant scarring requiring open, on-pump, cardiac surgery for removal of migrated distal tubing.

CASE PRESENTATION

A 7-year-old boy underwent VP shunt insertion for hydrocephalus secondary to intracranial astrocytoma. He presented at age 17 with evidence of right heart strain, associated with the distal shunt catheter proximally migrated into his heart and pulmonary arteries. Due to his delayed presentation, the catheter was knotted and partially immobilized by scar formation, finally requiring open-heart surgery to remove the catheter.

CONCLUSIONS

A multi-disciplinary evaluation with endovascular, neurosurgery, and cardiothoracic surgery may be the safest approach, especially in those patients with knotting on preoperative imaging.

In situ repair of vagus nerve stimulator lead damage: technical note

Vagus nerve stimulators (VNSs) are currently an accepted treatment for intractable epilepsy not amenable to ablative surgery. Battery death and lead damage are the main reasons for reoperation in patients with VNSs. In general, any damage to the lead requires revision surgery to remove the helical electrodes from the vagus nerve and replace the electrode array and wire. The electrodes are typically scarred and difficult to remove from the vagus nerve without injury. The authors describe 6 patients with VNSs who presented with low lead impedance on diagnostic testing, leading to the intraoperative finding of lead insulation disruption, or who were found incidentally at the time of implantable pulse generator battery replacement to have a tear in the outer insulation of the electrode wire. Instead of replacement, the wire insulation was repaired and reinforced in situ, leading to normal impedance testing. All 6 devices remained functional over a follow-up period of up to 87 months, with 2 of the 6 patients having a relatively shorter follow-up of only 12 months. This technique, applicable in a subset of patients with VNSs requiring lead exploration, obviates the need for lead replacement with its attendant risks.

Parent-Reported Executive Dysfunction in Children and Adolescents with Chiari Malformation Type 1

BACKGROUND

Children with Chiari malformation type 1 (CM1) have increasingly presented to neurosurgery clinics. Limited research relating to the cognitive dysfunction experienced by this population has been completed. In adults, inhibition problems and executive dysfunction have been documented.

METHODS

Seventy-seven parental reports of children with CM1 were included in the study. Parents completed questions on a scale rating daily executive functioning as well as reporting on common neurological symptoms.

RESULTS

The sample consisted of 41 males and 36 females with a mean age of 133.57 ± 42.18 months. Thirty-eight subjects had had decompression surgery. The most common neurological symptoms included: headache (69%), a history of pain (31%) and gait disturbance (20%). One third of the sample demonstrated overall executive functioning impairment, with working memory elevations being most prevalent (44%). Depression, gender, age and decompression surgery were not related to executive dysfunction.

CONCLUSIONS

The parental report of executive dysfunction in children with CM1 was higher than the standardized healthy sample. Metacognitive problems, especially working memory and initiation problems were most prevalent. A quick parental rating scale identifying children with executive dysfunction may be beneficial for neurosurgeons and assist with referrals for a more comprehensive neuropsychological assessment.

Is pelvic plexus nerve documentation feasible during robotic assisted laparoscopic ureteral reimplantation with extravesical approach?

PURPOSE

Urinary retention is a known complication of using an extravesical approach for ureteral reimplantation, especially in bilateral cases. The etiology may be secondary damage to pelvic nerves during ureteral dissection. Recent literature suggests that it is possible to visually identify these nerves during a robotic assisted laparoscopic approach. We performed an exploratory study to identify and document them in pediatric patients by means of electrophysiologic recordings.

MATERIAL AND METHODS

Seven consecutive patients undergoing robotic assisted laparoscopic ureteral reimplantation with extravesical approach were prospectively enrolled in the study. Following dissection of the ureter below the level of vas deferens in male and the uterine artery in female, staying close to the adventitia and approaching the ureterovesical junction, the fibers as described in human cadaveric studies were identified dorsomedial to the ureter and preserved. Stimulating and recording electrodes were passed through to record post-synaptic compound muscle action potentials of the bladder.

RESULTS

Even though the nerve fibers were visually identified, we were unable to consistently and reproducibly record compound muscle action potentials after stimulation of putative pelvic plexus fibers at the distal ureter, despite modulation in stimulation intensity, pulse characteristics, signal recording sensitivity and stimulator probe variation.

CONCLUSIONS

In this pilot study, the inconsistent findings raise questions about the exact location of the neurovascular bundle, nature of bladder smooth muscle electrophysiology and the appropriate methodology of evaluation. This may provide a reason to reexamine the intraoperatively expected location of pelvic plexus nerve fibers.

Intrapleural migration of a spinal catheter in a patient with arachnoiditis and extensive epidural scarring after tethered cord release: a case report and review of literature

OBJECTIVE

The objective of this study was to report a case of new onset refractory pain from intrapleural migration of a spinal catheter five months after the implantation of an intrathecal drug delivery system (IDDS).

MATERIALS AND METHODS

A 57-year-old man had intractable pain because of multiple intradural spinal explorations for tethered cord release. His pain was effectively treated with intrathecal morphine via an IDDS. Five months after the implantation, the patient developed return of the original pain more than two weeks after intrapleural migration of the intrathecal catheter.

RESULTS

The migration was documented by computed tomography, and repositioning of the catheter rendered the patient comfortable. The gradual onset of pain may have been due to decreasing delivery of drug to the cerebrospinal fluid as the catheter tip migrated further away from the dura. To our knowledge, this complication has not been reported in the literature.

CONCLUSION

Physicians and nursing staff that place and manage an IDDS should be aware of this complication.

Chiari malformation type I: related conditions

Chiari malformation type I (CMI) is a morphological diagnosis defined as the inferior displacement of the cerebellum through the foramen magnum. In parallel to this basic definition of CMI, there are diagnoses that co-exist with CMI in selected patients. In addition, there are specific constellations of clinical symptoms and signs reported in the literature that occur non-randomly in patients affected by CMI. There is no established system that categorizes these CMI-related conditions or even defines them as causes or consequences of CMI. Identifying the relationship between CMI and these associated disorders may allow greater understanding of CMI etiology and potentially inform CMI management.

Olig1 is expressed in human oligodendrocytes during maturation and regeneration

Myelin repair is inhibited in multiple sclerosis (MS), ultimately leading to axonal damage and disability. We aimed to understand the transcriptional mechanisms of regeneration in primary human oligodendrocyte cultures isolated from white matter of medically intractable epilepsy patients. Cultures at isolation contained 84% mature oligodendrocytes and 16% oligodendrocyte progenitor cells (OPC). The two populations showed a protracted regeneration of membranes expressing myelin proteins after 2-3 weeks in culture, and were kept long-term to study membranes maintenance. We profiled by quantitative PCR (qPCR) the sequential mRNA expression of transcription factors Olig1, Olig2, Nkx2.2, Sox10, PPARδ, PPARγ, cyclic nucleotide phosphodiesterase (CNP), myelin basic protein (MBP), myelin-associated glycoprotein (MAG) and myelin oligodendrocyte glycoprotein (MOG). In summary, Olig1 was not expressed in freshly isolated oligodendrocytes, but was expressed from the beginning of process extension until membranes maintenance. In contrast, Olig2 expression was restricted to isolation and during membranes production. We show for the first time PPARδ expression and absence of PPARγ in human oligodendrocytes. Nkx2.2, Sox10, PPARδ, CNP, MBP and MOG messengers were expressed at any time, while MAG messenger was expressed at mature stage only. Myelin proteins CNP, MBP, MAG, and MOG were confirmed by immunocytochemistry. Our findings point to different roles of Olig1 and Olig2 in regeneration of cultured adult human oligodendrocytes. Noticeably, the transcriptional profiles found in cultured neonatal rodent OPC are different. More studies are necessary to elucidate myelin repair in the adult human brain.

The impact of a 'resident replacement' nurse practitioner on an Academic Pediatric Neurosurgical service

INTRODUCTION

The introduction of 80-hour workweek limitations has challenged resident training programs with creative scheduling while maintaining comprehensive training experiences. The work hour restrictions may be more adaptable to a medical service, but have been very challenging to an academic surgical program. The particular challenges include maximizing academic learning opportunities, operating room experiences and direct bedside patient care while adhering to the 80-hour restriction. This paper examines the addition of a pediatric nurse practitioner (NP) to a pediatric neurosurgical academic program in response to the resident work hour restrictions.

METHOD

A survey questionnaire asking for responses to questions on a 1-10 rating scale was distributed to physicians, nurses and allied care providers approximately 1 year after addition of the NP. Participants were asked to rate satisfaction with the service's availability, responsiveness and assessment of patient clinical satisfaction prior to the addition of the NP and at the time of questionnaire distribution. In addition, the hospital paging log was reviewed over a several-month epoch before and after addition of the NP. Finally, the number of quality assurance sentinel events was reviewed for the year prior to and the year after the initiation of the NP program.

RESULTS

The satisfaction scores in all categories, including overall satisfaction, significantly improved (p < 0.001) after the addition of the NP to the neurosurgery service. Also, during the NP on-duty coverage hours, the number of paging calls received by the residents was reduced commensurate to the large number of calls received by the NP. This change was presumed to be due to the confidence of other services in obtaining a timely and appropriate response. Finally, the number of sentinel event reports remained stable.

DISCUSSION

The addition of an NP in response to resident training changes has been a positive influence on satisfaction with the pediatric neurosurgical service while reducing the reliance on residents for bedside clinical care. Patient safety appears not to have been affected. Presumably, this response to resident work hour limitations will provide the needed time to enhance resident didactic and intraoperative training experiences.

Priorities for hydrocephalus research: report from a National Institutes of Health-sponsored workshop

OBJECT

Treatment for hydrocephalus has not advanced appreciably since the advent of cerebrospinal fluid (CSF) shunts more than 50 years ago. Many questions remain that clinical and basic research could address, which in turn could improve therapeutic options. To clarify the main issues facing hydrocephalus research and to identify critical advances necessary to improve outcomes for patients with hydrocephalus, the National Institutes of Health (NIH) sponsored a workshop titled "Hydrocephalus: Myths, New Facts, and Clear Directions." The purpose of this paper is to report on the recommendations that resulted from that workshop.

METHODS

The workshop convened from September 29 to October 1, 2005, in Bethesda, Maryland. Among the 150 attendees was an international group of participants, including experts in pediatric and adult hydrocephalus as well as scientists working in related fields, neurosurgeons, laboratory-based neuroscientists, neurologists, patient advocates, individuals with hydrocephalus, parents, and NIH program and intramural staff. Plenary and breakout sessions covered injury and recovery mechanisms, modeling, biomechanics, diagnosis, current treatment and outcomes, complications, quality of life, future treatments, medical devices, development of research networks and information sharing, and education and career development.

RESULTS

The conclusions were as follows: 1) current methods of diagnosis, treatment, and outcomes monitoring need improvement; 2) frequent complications, poor rate of shunt survival, and poor quality of life for patients lead to unsatisfactory outcomes; 3) investigators and caregivers need additional methods to monitor neurocognitive function and control of CSF variables such as pressure, flow, or pulsatility; 4) research warrants novel interdisciplinary approaches; 5) understanding of the pathophysiological and recovery mechanisms of neuronal function in hydrocephalus is poor, warranting further investigation; and 6) both basic and clinical aspects warrant expanded and innovative training programs.

CONCLUSIONS

The research priorities of this workshop provide critical guidance for future research in hydrocephalus, which should result in advances in knowledge, and ultimately in the treatment for this important disorder and improved outcomes in patients of all ages.

ECoG gamma activity during a language task: differentiating expressive and receptive speech areas

Electrocorticographic (ECoG) spectral patterns obtained during language tasks from 12 epilepsy patients (age: 12-44 years) were analysed in order to identify and characterize cortical language areas. ECoG from 63 subdural electrodes (500 Hz/channel) chronically implanted over frontal, parietal and temporal lobes were examined. Two language tasks were performed. During the first language task, patients listened to a series of 50 words preceded by warning tones, and were asked to repeat each word. During a second memory task, subjects heard the 50 words from the first task randomly mixed with 50 new words and were asked to repeat the word only if it was a new word. Increases in ECoG gamma power (70-100 Hz) were observed in response to hearing tones (primary auditory cortex), hearing words (posterior temporal and parietal cortex) and repeating words (lateral frontal and anterior parietal cortex). These findings were compared to direct electrical stimulation and separate analysis of ECoG gamma changes during spontaneous inter-personal conversations. The results indicate that high-frequency ECoG reliably differentiates cortical areas associated with receptive and expressive speech processes for individual patients. Compared to listening to words, greater frontal lobe and decreased temporal lobe gamma activity was observed while speaking. The data support the concept of distributed functionally specific language modules interacting to serve receptive and expressive speech, with frontal lobe 'corollary discharges' suppressing low-level receptive cortical language areas in the temporal lobe during speaking.

Comparison of seizure detection algorithms in continuously monitored pediatric patients

SUMMARY

Robust, automated seizure detection has long been an important goal in epilepsy research because of both the possibilities for portable intervention devices and the potential to provide prompter, more efficient treatment while in clinic. The authors present results on how well four seizure detection algorithms (based on principal eigenvalue [EI], total power, Kolmogorov entropy [KE], and correlation dimension) discriminated between ictal and interictal EEG and electrocorticoencephalography (ECoG) from four patients (aged 13 months to 21 years). Test data consisted of 46 to 78 hours of continuously acquired EEG/ECoG for each patient (245 hours total), and the detectors' accuracy was checked against seizures found by a board-certified neurologist and an experienced registered EEG technician. The results were patient-specific: no algorithm performed well on a 13-month-old patient, and no algorithm consistently performed best on the other three patients. One of the metrics (EI) supported the existence of a postictal period of 5 to 15 minutes in the three oldest patients, but no strong evidence of a preictal anticipation was found. Two metrics (EI and KE) cycled continuously with a period of several hours in a 21-year-old patient, highlighting the importance of continuous analysis to differentiate background cycling from anticipation.

Observations regarding failure of cerebrospinal fluid shunts early after implantation

✓Despite advances in cerebrospinal fluid (CSF) diversionary techniques, shunt failure due to infection or malfunction remains a persistent problem in hydrocephalus care. The aim of this study was to evaluate the independent predictors of early shunt survival after implantation in a large cohort of patients. The authors retrospectively reviewed the records of all patients who had undergone shunt implantation procedures at their institution during an 8-year period. They analyzed the independent predictors of shunt survival in 116 failed shunt placement procedures (infection or malfunction) by performing univariate and multivariate factorial analyses. Analysis of the 116 failed shunts in the 396 new shunt placement procedures performed revealed that age was a significant independent predictor of shunt survival time in failures due to malfunction (p < 0.05) as well as infection (p < 0.05). In addition, a significant relationship between patient race and shunt survival was also found. As suggested by data in other studies focused on this outcome, early shunt failure occurs sooner in younger patients. Interestingly, this study is one of few whose data have revealed that race may affect shunt failure after implantation. Specifically, shunt failure due to infection resulted in significantly shorter shunt survival time in non-white patients compared with that in white patients. Among the shunts that failed due to malfunction, however, white patients had shorter shunt survival times.

Frequency Domain Analysis of Human Subdural Recordings

SUMMARY

It is possible to localize many aspects of cortical function and dysfunction without the use of direct electrical stimulation of cortex. This study explores the degree to which information can be obtained about functional cortical organization relative to epileptogenic regions through analysis of electrocorticographic recordings in the frequency domain. Information about the extent of seizure regions and the location of the normal sensory and motor homunculus and some higher language and memory related areas can be obtained through the analysis of task-related power spectrum changes and changes in lateral interelectrode coherence patterns calculated from interictal and ictal recordings.

Neuroprotective effect of the surfactant poloxamer 188 in a model of intracranial hemorrhage in rats

OBJECT

Neuronal injury remains a leading cause of morbidity in both neonates and adults with injuries induced by intracranial hemorrhage, ischemia-reperfusion, and excitotoxicity. To date, a number of neuroprotective strategies have been evaluated, but they have shown little benefit. Poloxamer 188 (P-188), a membrane-active triblock copolymer, has been studied extensively as a cell-membrane sealant. The authors used an animal model to study the neuroprotectant effects of P-188 administered by intracisternal (IC) injection after experimentally induced intraparenchymal hemorrhage.

METHODS

Sprague-Dawley rats received an IC injection of either P-188 or vehicle (artificial cerebrospinal fluid) 10 minutes after striatal infusion of 50 microl of autologous blood. Animals from both treatment groups were killed either 2 or 7 days later. In a second experiment, after striatal blood infusion and early IC injection of either P-188 or vehicle, animals received daily IC injections of either P- 188 or vehicle for 5 days, and were killed 7 days after induction of the experimental hemorrhage. Striatal tissues were histologically analyzed for neuronal loss, and lesion volumes were determined. Lesion volumes in the animals that received a single dose of P-188 were significantly smaller (mean+/-standard deviation 18.3+/-4.3 mm(3), six rats; p = 0.04) than those in the control group (31.4+/-4.3 mm(3), seven rats) when measured 2 days postinjection; however, no difference in lesion volumes was present 7 days postinjection. Lesion volumes in the animals who received 5 days of daily P-188 injections were significantly smaller (1.50+/-0.58 mm(3), 10 rats; p = 0.04) than those in the corresponding control group (5.04+/-1.85 mm(3), eight rats) when measured at 7 days.

CONCLUSIONS

A single dose of P- 188 protects against early neuronal loss after hemorrhage but has no effect on long-term hemorrhage-induced neuronal loss. However, repeated daily P-188 treatment appears to produce effective long-term neuronal protection.

ADJUSTABLE SHUNT VALVE REPROGRAMMING AT HOME

OBJECTIVE

Shunt valve resistance changes using a specialized magnetic programming device permit noninvasive changes to cerebrospinal fluid drainage. In selected cases between 2001 and 2005, patients and families used shunt valve programming devices at home. This study examines the safety and efficacy of this practice.

METHODS

We conducted a retrospective review of the medical records of patients who had been given a shunt valve-programming device for home use. A survey was mailed to patients or family members requesting information regarding their experiences with the shunt valve programming device. Patient and family responses were tabulated and a statistical analysis was performed.

RESULTS

Twenty patients or families returned the survey. The median patient age was 19.6 years (range, 6–48 yr); 25% were male. Seventeen patients had pseudotumor cerebri, one had an arachnoid cyst, and two had slit ventricle syndrome. Fifteen patients had lumboperitoneal shunts, one had a ventriculoperitoneal shunt, three had cisterna magna shunts, and one had an arachnoid cyst-to-peritoneal shunt. No adverse events were attributable to the use of the home shunt valve programmer. Thirty-five percent of respondents used the programmer at least once every week, 40% used the programmer between once a week and once a month, and 25% used the programmer less frequently than once per month. Overall, 85% of respondents reported that they benefited “very much” from the use of a home shunt valve programmer and 15% of respondents benefited “somewhat.”

CONCLUSION

Providing shunt valve programming devices to selected patients for home use is a safe practice associated with high patient satisfaction. However, the selection of appropriate patients, comprehensive patient education, and close patient-physician communication are crucial to the success of this practice.

Correction of sagittal craniosynostosis using a novel parietal bone fixation technique: results over a 10-year period

Isolated sagittal synostosis is a common form of craniosynostosis affecting roughly 1 in 5,000 children at birth. This results in a scaphocephalic head shape with a characteristically elongated anterior-posterior dimension and narrowed biparietal diameter. We present our experience with the correction of scaphocephaly due to sagittal synostosis using cranial vault reconstruction with a novel form of parietal bone fixation in 21 patients over 10 years. The medial fixation results in a hinging effect whereby transverse brain growth at the squamoid suture is enhanced. This results in excellent cosmetic results that are immediate and durable without the need for postoperative molding helmets. Furthermore, the complications associated with this procedure are limited.

Mutually suppressive interrelations of symmetric epileptic foci in bitemporal epilepsy and their inhibitory stimulation

OBJECTIVES

The goal of this study is to analyze the suppressive interaction of symmetric temporal lobe epileptic foci, assess some failures of epilepsy surgery, and evaluate the possibility of terminating focal seizures with stimulation of symmetric epileptic foci.

MATERIALS AND METHODS

One hundred and twenty-nine intractable epilepsy patients (age range 6-53 years) with bitemporal epileptiform abnormalities in multiple scalp EEGs were evaluated with chronically implanted depth and subdural electrodes. Interelectrode coherence and power spectra were studied using internally developed software.

RESULTS

Bitemporal epileptic foci were found in 85/129 (66%) patients with reciprocal relations between these foci in 57/85 (67%) patients. Temporal lobectomy was performed for 67/85 patients. 12/67 patients became free of seizures (Engel's Class I), 32/67 improved (Classes II and III), and 23/67 did not improve. 14/23 patients demonstrated post-surgical activation of the contralateral temporal lobe epileptic focus. For 8/14 of these patients, the stereotactic cryoamygdalatomy was performed in the temporal lobe contralateral to the first surgery. 5/8 patients became free of seizures. It was found that stimulation of temporal lobe deep epileptic focus may terminate focal seizures in the contralateral symmetric structures.

CONCLUSION

A mutually suppressive relationship is one of variants of the interaction of symmetric epileptic foci. Some epilepsy surgery failures may be a result of post-surgical activation of the intact focus. The increase of coherence between both temporal lobes before the seizure onset of the seizure suggests the establishment of functional interrelations between two epileptic foci at an early, "hidden" phase of seizures, and may predict the direction of seizure spread. Mutually suppressive interrelations of symmetric epileptic foci might be employed for chronic therapeutic stimulation.

A cortical potential imaging study from simultaneous extra- and intracranial electrical recordings by means of the finite element method

In the present study, we have validated the cortical potential imaging (CPI) technique for estimating cortical potentials from scalp EEG using simultaneously recorded electrocorticogram (ECoG) in the presence of strong local inhomogeneity, i.e., Silastic ECoG grid(s). The finite element method (FEM) was used to model the realistic postoperative head volume conductor, which includes the scalp, skull, cerebrospinal fluid (CSF) and brain, as well as the Silastic ECoG grid(s) implanted during the surgical evaluation in epilepsy patients, from the co-registered magnetic resonance (MR) and computer tomography (CT) images. A series of computer simulations were conducted to evaluate the present FEM-based CPI technique and to assess the effect of the Silastic ECoG grid on the scalp EEG forward solutions. The present simulation results show that the Silastic ECoG grid has substantial influence on the scalp potential forward solution due to the distortion of current pathways in the presence of the extremely low conductive materials. On the other hand, its influence on the estimated cortical potential distribution is much less than that on the scalp potential distribution. With appropriate numerical modeling and inverse estimation techniques, we have demonstrated the feasibility of estimating the cortical potentials from the scalp EEG with the implanted Silastic ECoG gird(s), in both computer simulations and in human experimentation. In an epilepsy patient undergoing surgical evaluation, the cortical potentials were reconstructed from the simultaneously recorded scalp EEG, in which main features of spatial patterns during interictal spike were preserved and over 0.75 correlation coefficient value was obtained between the recorded and estimated cortical potentials. The FEM-based CPI technique provides a means of connecting the simultaneous recorded ECoG and the scalp EEG and promises to become an effective tool to evaluate and validate CPI techniques using clinic data.

The Chiari pseudotumor cerebri syndrome: symptom recurrence after decompressive surgery for Chiari malformation type I

INTRODUCTION

The etiology of Chiari malformation type I (CM1) as well as other anomalies associated with CM1 remains poorly defined. We have noted the presence of elevated CSF pressures with small ventricles, consistent with the pseudotumor cerebri (PTC) syndrome in a group of CM1 patients that did not respond over the long term to posterior fossa decompression. In order to better understand this association, we reviewed a series of CM1 patients treated by posterior fossa decompression to define the prevalence and nature of post-Chiari PTC.

METHODS

We performed a retrospective chart review of 192 patients diagnosed with CM1 and treated by posterior fossa decompression. Patients who failed to respond to surgery were evaluated by CINE MR flow studies to assess presence of CSF flow at the foramen magnum and then by lumbar puncture if flow was present. The diagnosis of Chiari PTC was defined by recurrence of Chiari-like symptoms after decompression, elevated lumbar CSF pressure in the absence of ventriculomegaly, and transient resolution of symptoms with large volume lumbar CSF drainage.

RESULTS

Thirty-six of 192 patients did not improve with surgical decompression. Fifteen of 36 operative CM1 patients (41.6%) were found to have Chiari PTC. The most frequent symptoms of CM1/PTC patients were head pain, body aches, and balance difficulties. Three patients also experienced visual complaints. The mean maximum lumbar CSF pressure documented in this cohort was 26 cm of water in adults and 25.3 in children. All patients received treatment for the CM1/PTC that culminated with CSF shunt placement in 14/15. Seven of 9 pediatric patients had significant symptom resolution while 6/6 adult patients remained variably symptomatic.

CONCLUSION

CM1 and PTC co-exist in a surprising percentage of failed operative CM1 patients and present with a syndrome that is difficult to treat. The etiology of this association after Chiari decompression is unclear, though perhaps posterior fossa surgery in the setting of abnormal anatomy and potentially anomalous CSF flow dynamics contributes to CSF malabsorption and resultant or coexistant PTC.

Surfactant poloxamer 188-related decreases in inflammation and tissue damage after experimental brain injury in rats

OBJECT

The surfactant, poloxamer 188 (P-188), has been found to protect against tissue injury in various experimental models. Its protective mechanism may involve the effects of the surfactant against oxidative stress and inflammation. The authors investigated the role of P- 188 in the reduction of tissue injury and macrophage response in a model of excitotoxic brain injury in the rat striatum.

METHODS

Fifteen Sprague-Dawley rats underwent stereotactic injection of 120 nmol of quinolinic acid into the striatum and received intracisternal injection of vehicle or P-188 (40 mg/kg) at 10 minutes and 4 hours postinjury. Rats were killed after 1 week, and the histological score was determined based on the degree of overall tissue injury (Grades 1-4) at the lesion site. The number of macrophages within the lesioned striatum was compared with that found within the striatum on the nonoperated contralateral side. The scores related to tissue damage and the macrophage ratios of each group were then compared using t-tests. Striatal injection of the toxin produced a lesion characterized by necrosis and inflammation surrounding the injection site in all six control animals. In rats in which intracisternal P-188 was administered, significantly less tissue injury was demonstrated (mean score 2.45 +/- 0.74) than in controls (mean score 3.14 +/- 0.75) (p = 0.045). The rats that received intracisternal surfactant also had significantly less macrophage infiltrate (mean ratio 1.06 +/- 0.18) than control animals (mean ratio 2.00 +/- 0.48) (p = 0.004).

CONCLUSIONS

The surfactant P-188 reduces tissue loss and macrophage infiltrate after excitotoxic brain injury in the rat. Possible mechanisms of this effect may include direct surfactant modulation of inflammatory cell membrane fluidity.

Pseudotumor cerebri patients with shunts from the cisterna magna: clinical course and telemetric intracranial pressure data

OBJECTIVE

Shunting of cerebrospinal fluid (CSF) to an extracranial site is the mainstay of treatment of absorptive hydrocephalus and pseudotumor cerebri. On occasion, both lateral ventricles and the lumbar space become unsuitable for placement of a functioning CSF drainage catheter. We have encountered several such patients and describe our strategy of shunting from the cisterna magna to the pleural space or cardiac atrium.

METHODS

We report a retrospective review of the clinical course of five patients with cisternal shunts and intracranial pressure telemonitoring devices.

RESULTS

Cisternal shunting was able to successfully drain CSF to a normal pressure in all five patients. CSF pressure data collected from those patients indicate that the CSF pressure dynamics in cisternal shunts is similar to that of ventricular shunts. However, the cisternal shunting and subsequent high revision rate did result in a significant number of complications and two shunt infections.

CONCLUSION

Shunting CSF from the cisterna magna in the absence of another suitable drainage site does result in acceptable reduction of elevated intracranial pressure. However, the technique is associated with a high complication rate that may reflect the population of patients in whom this technique is required.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE

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

Lumbar CSF shunting preferentially drains the cerebral subarachnoid over the ventricular spaces: implications for the treatment of slit ventricle syndrome

Based on a proposed pathophysiology of slit ventricle syndrome (SVS), we have hypothesized that lumboperitoneal shunting exerts effects in SVS patients by increasing the buffering capacity for raised intracranial pressure (ICP) via an increase in cerebrospinal fluid drainage from the cerebral subarachnoid space (SAS). We describe 3 SVS patients with patent lumbar subarachnoid drainage but under-functioning ventriculoperitoneal shunts (VPS) who presented with ventriculomegaly (not SVS), and persistence of shunt malfunction like symptoms. Revision of the VPS resulted in complete resolution of symptoms despite a finding of low pressure in the ventricular space. This supports the hypothesis that lumboperitoneal shunting preferentially drains the SAS over the intraventricular space and in these cases allows the 'SVS' ventricles to enlarge by creating a pressure gradient from ventricles to SAS through the cortical mantle.

Poloxamer 188 Volumetrically Decreases Neuronal Loss in the Rat in a Time-dependent Manner

OBJECTIVE

Excitotoxicity is a multistep process that results in either necrosis or apoptosis. It has been associated with neuronal death in trauma, ischemia, and neurodegeneration. The final step in necrotic cell death is the rupture of a cell's plasma membrane; repair of this membrane rupture is a potentially powerful technique of neuroprotection. Poloxamer 188 (P-188) is a synthetic surfactant that seals experimentally porated membranes. This study investigated the usefulness and time dependence of intrathecal P-188 in protecting neurons in an in vivo model of excitotoxicity in the rat.

METHODS

Twenty-eight Sprague-Dawley rats underwent striatal infusion of quinolinic acid to produce a spherical excitotoxic lesion. Each animal then received either vehicle or P-188 at 10 minutes, 4 hours, or both time points after surgery by direct cisterna magna injection. Animals were killed at 1 week, and brains were stained immunohistochemically for the neuronal marker Neu-N. Volumes of neuronal loss were calculated and compared between groups by analysis of variance.

RESULTS

All animals were found to have spherical, stereotyped lesions. The animals that received intrathecal poloxamer at the early injection time had statistically smaller lesions (8.16 +/- 6.12 mm(3); n = 5; P = 0.0015) than controls (18.25 +/- 11.42 mm(3); n = 11). Those animals that received poloxamer at both injection times also had statistically smaller lesions (10.57 +/- 9.00 mm(3); n = 7; P = 0.0095). The group that received poloxamer at the late injection time only did not have significantly decreased lesion size (14.86 +/- 7.95 mm(3); n = 5).

CONCLUSION

Intrathecal P-188 reduces neuronal loss after excitotoxic injury in the rat only when delivered immediately after the toxin. This observation confirms the potential of surfactant molecules as neuroprotectants but predicts that their usefulness is best realized by early and potentially ongoing treatment.

Initial endoscopic management of pineal region tumors and associated hydrocephalus: clinical series and literature review

OBJECT

The authors report their experience in six patients with pineal tumors and associated hydrocephalus who underwent an endoscopic biopsy procedure and third ventriculocisternostomy (ETVC) in a single sitting.

METHODS

The ETVC was successfully performed without complication in all patients; however, a ventriculoperitoneal shunt was eventually required in four. Histological diagnosis was successfully established in four patients. The authors also reviewed the literature to assess reports involving ETVC and tumor biopsy sampling in patients with pineal tumors and hydrocephalus. A total of 54 cases, including those in this study, have been reported. Fifteen percent of the patients eventually required placement of a ventricular shunt. The transient complication rate was 15% with no death. A positive tissue diagnosis was established in 89% of the cases overall.

CONCLUSIONS

The authors conclude that the endoscopic management of patients with pineal region masses and hydrocephalus may be a preferred initial strategy.

Endoscopic cyst fenestration outcomes in children one year of age or less

The use of endoscopic fenestration (EF) is becoming an increasingly common treatment for symptomatic intracranial cysts. Very little data exist regarding outcomes for this procedure in children 1 year of age or younger. We retrospectively reviewed the clinical outcomes of 8 children 1 year of age or less treated at our institution with endoscopic cyst fenestration. The mean follow-up was roughly 2.5 years. These data were combined with 17 other cases obtained from the published literature. EF was successful in rendering patients shunt-free or minimizing the number of ventricular catheters in 18 of 26 operations. There were 8 outright failures -- two in 1 patient. Given the risks and complications of cerebrospinal fluid shunting in children less than 1 year of age, we advocate the consideration of EF as initial treatment of symptomatic intracranial cysts.

The surfactant poloxamer-188 protects against glutamate toxicity in the rat brain

Membrane repair of damaged neurons by surfactant poloxamers has been noted in experimental spinal cord injury and in vitro excitotoxicity. We examined poloxamer-188 (P-188)-mediated neuroprotection in a rat model of glutamate toxicity. Quinolinate was infused into the striatum followed 10 min and 4 h later by P-188 administered either i.v. or intracisternally (i.c.), or by vehicle. Mean neuronal loss examined volumetrically 7 days later in control animals was 50% greater (P < 0.01) than after i.c. P-188 treatment; control lesion volumes were 38% greater than lesion volumes after i.v. P-188 treatment; however, that comparison did not reach significance. This robust protection against glutamate toxicity may predict P-188-mediated neuroprotection against a broad range of clinically relevant neural insults.