Gregory W. Albert

Seizure termination by acidosis depends on ASIC1a

Most seizures stop spontaneously; however, the molecular mechanisms that terminate seizures remain unknown. Observations that seizures reduced brain pH and that acidosis inhibited seizures indicate that acidosis halts epileptic activity. Because acid-sensing ion channel 1a (ASIC1a) is exquisitely sensitive to extracellular pH and regulates neuron excitability, we hypothesized that acidosis might activate ASIC1a, which would terminate seizures. Disrupting mouse ASIC1a increased the severity of chemoconvulsant-induced seizures, whereas overexpressing ASIC1a had the opposite effect. ASIC1a did not affect seizure threshold or onset, but shortened seizure duration and prevented seizure progression. CO2 inhalation, long known to lower brain pH and inhibit seizures, required ASIC1a to interrupt tonic-clonic seizures. Acidosis activated inhibitory interneurons through ASIC1a, suggesting that ASIC1a might limit seizures by increasing inhibitory tone. Our results identify ASIC1a as an important element in seizure termination when brain pH falls and suggest both a molecular mechanism for how the brain stops seizures and new therapeutic strategies.

Chiari malformation Type I in children younger than age 6 years: presentation and surgical outcome

OBJECT The authors conducted a study to evaluate the unique presenting signs and symptoms of Chiari malformation Type I (CM-I) in children younger than 6 years of age and highlight the benefits of early surgical treatment in this patient population. METHODS The authors reviewed the medical records of patients who presented to the neurosurgery department before their 6th birthday and subsequently underwent surgery for CM-I. They identified 39 patients who had been evaluated between 1984 and 2007 and examined the medical records for presentation, surgical intervention, and outcome. RESULTS Children aged 0-2 years commonly presented with oropharyngeal dysfunction (77.8%). Children aged 3-5 years more frequently presented with syringomyelia (85.7%), scoliosis (38.1%), and/or headache (57.1%). All patients underwent posterior fossa craniectomy. Additionally, in many patients cervical laminectomy and/or duraplasty was performed. A few patients required transoral decompression and occipitocervical fusion. In most cases, surgery led to resolution or dramatic improvement of initial symptoms. CONCLUSIONS Early recognition and surgical treatment of CM-I in young children leads to good outcomes in the majority of patients. Additional therapies for oropharyngeal dysfunction, syringomyelia, and scoliosis can frequently be avoided.

A method for placing Heschl gyrus depth electrodes

A wide range of devices is used to obtain intracranial electrocorticography recordings in patients with medically refractory epilepsy, including subdural strip and grid electrodes and depth electrodes. Penetrating depth electrodes are required to access some brain regions, and 1 target site that presents a particular technical challenge is the first transverse temporal gyrus, or Heschl gyrus (HG). The HG is located within the supratemporal plane and has an oblique orientation relative to the sagittal and coronal planes. Large and small branches of the middle cerebral artery abut the pial surface of the HG and must be avoided when planning the electrode trajectory. Auditory cortex is located within the HG, and there are functional connections between this dorsal temporal lobe region and medial sites commonly implicated in the pathophysiology of temporal lobe epilepsy. At some surgical centers, depth electrodes are routinely placed within the supratemporal plane, and the HG, in patients who require intracranial electrocorticography monitoring for presumed temporal lobe epilepsy. Information from these recordings is reported to facilitate the identification of seizure patterns in patients with or without auditory auras. To date, only one implantation method has been reported to be safe and effective for placing HG electrodes in a large series of patients undergoing epilepsy surgery. This well-established approach involves inserting the electrodes from a lateral trajectory while using stereoscopic stereotactic angiography to avoid vascular injury. In this report, the authors describe an alternative method for implantation. They use frameless stereotaxy and an oblique insertion trajectory that does not require angiography and allows for the simultaneous placement of subdural grid arrays. Results in 19 patients demonstrate the safety and efficacy of the method.

Loss of Acid Sensing Ion Channel-1a and Bicarbonate Administration Attenuate the Severity of Traumatic Brain Injury

Traumatic brain injury (TBI) is a common cause of morbidity and mortality in people of all ages. Following the acute mechanical insult, TBI evolves over the ensuing minutes and days. Understanding the secondary factors that contribute to TBI might suggest therapeutic strategies to reduce the long-term consequences of brain trauma. To assess secondary factors that contribute to TBI, we studied a lateral fluid percussion injury (FPI) model in mice. Following FPI, the brain cortex became acidic, consistent with data from humans following brain trauma. Administering HCO3 − after FPI prevented the acidosis and reduced the extent of neurodegeneration. Because acidosis can activate acid sensing ion channels (ASICs), we also studied ASIC1a−/− mice and found reduced neurodegeneration after FPI. Both HCO3 − administration and loss of ASIC1a also reduced functional deficits caused by FPI. These results suggest that FPI induces cerebral acidosis that activates ASIC channels and contributes to secondary injury in TBI. They also suggest a therapeutic strategy to attenuate the adverse consequences of TBI.

Ankylosing spondylitis of the craniovertebral junction: a single surgeon's experience

OBJECT The objective of this study was to describe a single surgeons experience managing craniovertebral junction (CVJ) disease due to ankylosing spondylitis. METHODS The authors undertook a retrospective review of the records of patients with CVJ disease due to ankylosing spondylitis who were evaluated and treated by the senior author. Charts were reviewed for symptoms and signs at presentation, radiography results, treatment, and outcome. In addition, some of the patients had pathology reports available for review. RESULTS Eight patients with CVJ disease due to ankylosing spondylitis were identified who were evaluated by the senior author in the years 1990-2008. The most common presenting symptoms were neck pain (37.5%), cranial neuropathy (37.5%), and sensory disturbance (62.5%). On examination, the most common findings were limited cervical range of motion (37.5%), weakness (50%), and myelopathy (75%). Radiographic evaluation revealed atlantoaxial subluxation, retroodontoid pannus formation, basilar invagination, and bone erosion. Surgery was offered to all of the patients, 7 of whom underwent operations. In most cases, the treatment was transoral-transpalatopharyngeal decompression followed by occipitocervical fusion. One patient with a reducible lesion underwent dorsal fusion alone. Neurological outcomes were favorable overall. CONCLUSIONS The incidence of CVJ disease in patients with ankylosing spondylitis varies among reports. These cases are rare in most neurosurgery clinics. It is important to recognize that patients with ankylosing spondylitis are at risk for CVJ disease, similar to patients with rheumatoid arthritis. Principles common to the management of other CVJ pathologies apply to these patients as well.

Magnetoencephalography-guided resection of epileptogenic foci in children

OBJECT Resective surgery is increasingly used in the management of pediatric epilepsy. Frequently, invasive monitoring with subdural electrodes is required to adequately map the epileptogenic focus. The risks of invasive monitoring include the need for 2 operations, infection, and CSF leak. The aim of this study was to evaluate the feasibility and outcomes of resective epilepsy surgery guided by magnetoencephalography (MEG) in children who would have otherwise been candidates for electrode implantation. METHODS The authors reviewed the records of patients undergoing resective epilepsy surgery at the Hospital for Sick Children between 2001 and 2010. They identified cases in which resections were based on MEG data and no intracranial recordings were performed. Each patients chart was reviewed for presentation, MRI findings, MEG findings, surgical procedure, pathology, and surgical outcome. RESULTS Sixteen patients qualified for the study. All patients had localized spike clusters on MEG and most had abnormal findings on MRI. Resection was carried out in each case based on the MEG data linked to neuronavigation and supplemented with intraoperative neuromonitoring. Overall, 62.5% of patients were seizure free following surgery, and 20% of patients experienced an improvement in seizures without attaining seizure freedom. In 2 cases, additional surgery was performed subsequently with intracranial monitoring in attempts to obtain seizure control. CONCLUSIONS MEG is a viable alternative to invasive monitoring with intracranial electrodes for planning of resective surgery in carefully selected pediatric patients with localization-related epilepsy. Good candidates for this approach include patients who have a well-delineated, localized spike cluster on MEG that is concordant with findings of other preoperative evaluations and patients with prior brain pathologies that make the implantation of subdural and depth electrodes somewhat problematic.

Predictors of the need for cerebrospinal fluid diversion in patients with myelomeningocele

OBJECT Many patients with myelomeningocele (MMC) develop hydrocephalus, and most will undergo CSF diversion. The goal of this retrospective study was to determine whether there was a change in the shunt rate over the 7 consecutive years of the study. The authors will also identify the criteria used to determine the need for shunt placement. METHODS During a 7-year period, 73 patients underwent MMC closure at Arkansas Childrens Hospital. The shunt rate for each year was calculated. Clinical characteristics were evaluated, including apneic and bradycardic spells, CSF leak, level of the MMC, head circumference, and rate of head growth. In addition, radiological images were reviewed, and the frontooccipital horn ratio (FOHR), ventricular index (VI), and thalamooccipital distance (TOD) were calculated. Comparisons were made between those patients who underwent shunt placement and those who did not. RESULTS One patient was excluded due to death in the perinatal period. Of the 72 remaining patients, 54 (75%) underwent placement of a ventriculoperitoneal shunt. This rate did not change significantly over time. Between the cohorts with and without a shunt there was no significant difference in age, sex, or race. There was no significant difference in apneic episodes or bradycardic episodes. There was a statistically significant difference in fontanelle characteristics, head circumference at birth, and rate of head growth. Patients who required CSF diversion had a mean head growth of 0.32 cm/day compared with those who did not receive a shunt (0.13 cm/day; p < 0.05). All radiological parameters were found to be statistically significant. CONCLUSIONS In this study, several classic indicators of hydrocephalus in the neonate were not found to be significantly associated with the need for CSF diversion. Fontanelle characteristics, head circumference at birth, and head growth velocity were associated with the need for shunt placement. Imaging information including the VI, TOD, and FOHR are statistically significant measures to evaluate prior to placement of a ventriculoperitoneal shunt. The optimal patient with MMC for CSF diversion will have full to tense fontanelle, increasing head circumference of more than 3 mm/day, and radiological evidence of an elevated VI, TOD, and/or FOHR.

Occipital lobe epilepsy in children: Characterization, evaluation and surgical outcomes

INTRODUCTION Occipital lobe epilepsy (OLE) poses a diagnostic challenge to clinicians. Here, we present our experience in the surgical management of OLE in children using magnetoencephalography (MEG) in the pre-operative evaluation. METHODS Retrospective chart review was performed from 2000 to 2010 to identify patients with OLE. Patients were analyzed in two categories: isolated OLE (11 patients) and extended OLE (parietooccipital, temporooccipital, and temporoparietooccipital; 30 patients). Survival analysis and multivariate Cox proportional hazards regression were used to identify independent predictors of seizure outcome. RESULTS Forty-one patients with a mean follow-up of 3.1 years were identified with an overall 68% rate of satisfactory seizure outcome. Patients with extended OLE had younger ages at seizure onset and different seizure semiologies compared with those with isolated OLE. None of the latter underwent insertion of subdural grid electrodes for localization of the epileptogenic zone compared with 77% of the former (p<0.001). On multivariate analysis, the strongest independent predictor of unsatisfactory outcome was MEG dipoles in the occipital lobe contralateral to resection. CONCLUSION Here, we find similar seizure outcomes for isolated and extended OLE foci despite the use of less invasive strategies for the former. Furthermore, we describe the role of MEG in evaluation, surgical planning and prognostication of children with OLE.

Postoperative radiographic findings in patients undergoing intracranial electrode monitoring for medically refractory epilepsy

OBJECT In this study the authors sought to determine whether any correlations existed between postimplantation head CT findings and the need to perform decompression surgery in patients with grid electrodes. METHODS The authors identified 74 patients who underwent intracranial electrode monitoring for medically refractory epilepsy from January 2000 through June 2008. Only the 46 patients who had head CT scans available for review were included in the study. The authors were able to determine the number and types of electrodes placed as well as complications experienced. They reviewed the CT scans for abnormal findings including extraaxial fluid collections, intracranial hemorrhages, and signs of mass effect. RESULTS All patients developed some degree of extraaxial fluid collection following the placement of intracranial electrodes. The maximum width of the extraaxial fluid collection and the degree of midline shift were not predictive of the need for decompressive surgery. The presence, but not degree, of midline shift was associated with the need for decompressive surgery. Likewise, the presence of ventricular asymmetry was correlated with the need for removal of the electrodes and bone flap. Patients without midline shift or ventricular asymmetry on CT did not require decompressive surgery. CONCLUSIONS After undergoing placement of intracranial electrodes all patients develop extraaxial fluid collections. In addition, many patients develop signs of mass effect including midline shift and ventricular asymmetry. When these findings are absent it is highly unlikely that surgical decompression is required.

Spine ultrasounds should not be routinely performed for patients with simple sacral dimples

Primary care providers commonly obtain spine ultrasounds for neonates with simple sacral dimples due to perceived concerns about underlying spinal dysraphism, despite a lack of scientific evidence. Nine papers addressing routine spine ultrasounds for children with sacral dimples showed that 3.4% of the 5166 patients had abnormal spine ultrasounds, compared with the 4.8% reported by another study for children without sacral dimples. Most of the abnormal findings in patients with sacral dimples were of no clinical significance.