Chad A. Glenn

Seizure Freedom Rates and Prognostic Indicators After Resection of Gangliogliomas: A Review.

Gangliogliomas are rare tumors that comprise up to 40% of lesional epilepsy. Seizure control represents an important quality-of-life determinant in patients with these tumors. Here we present results of a literature review addressing rates of seizure freedom in in patients with gangliogliomas. Across studies, seizure freedom occurred in 63%-100% of patients. Many studies included follow-up times of greater than 5 years, suggesting that the responses are durable. We discuss potential prognostic factors associated with seizure freedom, including the duration of epilepsy, patient age, frequency and semiology of seizures, tumor location, extent of surgical resection, and operative strategy, including surgical approach and use of invasive monitoring. Although significant differences in study populations and treatments preclude meta-analysis, we discuss prognostic factors identified in individual studies. Increased extent of resection, lesser duration of epilepsy, and younger age at surgery have been associated with increased seizure freedom rates in at least 2 studies each. Although all studies were retrospective in nature and are consequently limited by the weaknesses inherent to such investigations, the literature suggests that surgery is able to relieve most ganglioglioma patients--regardless of patient demographics, tumor characteristics, and operative variables--of seizures.

A method for safely resecting anterior butterfly gliomas: the surgical anatomy of the default mode network and the relevance of its preservation

OBJECTIVE Gliomas invading the anterior corpus callosum are commonly deemed unresectable due to an unacceptable risk/benefit ratio, including the risk of abulia. In this study, the authors investigated the anatomy of the cingulum and its connectivity within the default mode network (DMN). A technique is described involving awake subcortical mapping with higher attention tasks to preserve the cingulum and reduce the incidence of postoperative abulia for patients with so-called butterfly gliomas. METHODS The authors reviewed clinical data on all patients undergoing glioma surgery performed by the senior author during a 4-year period at the University of Oklahoma Health Sciences Center. Forty patients were identified who underwent surgery for butterfly gliomas. Each patient was designated as having undergone surgery either with or without the use of awake subcortical mapping and preservation of the cingulum. Data recorded on these patients included the incidence of abulia/akinetic mutism. In the context of the study findings, the authors conducted a detailed anatomical study of the cingulum and its role within the DMN using postmortem fiber tract dissections of 10 cerebral hemispheres and in vivo diffusion tractography of 10 healthy subjects. RESULTS Forty patients with butterfly gliomas were treated, 25 (62%) with standard surgical methods and 15 (38%) with awake subcortical mapping and preservation of the cingulum. One patient (1/15, 7%) experienced postoperative abulia following surgery with the cingulum-sparing technique. Greater than 90% resection was achieved in 13/15 (87%) of these patients. CONCLUSIONS This study presents evidence that anterior butterfly gliomas can be safely removed using a novel, attention-task based, awake brain surgery technique that focuses on preserving the anatomical connectivity of the cingulum and relevant aspects of the cingulate gyrus.

Management of Petroclival Meningiomas: A Review of the Development of Current Therapy

The surgical management of petroclival meningioma remains challenging, due to the difficulty of accessing the region and the vital structures adjacent to the origin of these tumors. Petroclival meningiomas were originally considered largely unresectable. Until the 1970s, resection carried a 50% mortality rate, with very high rates of operative morbidity if attempted. However, in the past 40 years, advances in neuroimaging and approaches to the region were refined, and results from resection of petroclival meningiomas have become more acceptable. Today, the developments of a multitude of surgical approaches as well as innovations in neuroimaging and stereotactic radiotherapy have proved powerful options for multimodality management of these challenging tumors.

Proximal ventricular shunt malfunctions in children: Factors associated with failure.

Ventricular shunt failures and subsequent revisions are a significant source of patient morbidity. We conducted a review of pediatric patients undergoing placement or revision of ventricular shunts at our institution between January 2007 and December 2008. Patients were followed through to July 2014. Data collected included patient demographics, shunt history and indication for procedure, approach taken for shunt placement, and location of shunt tip in relation to the foramen of Monro. Univariate and multivariate analyses were conducted to identify factors associated with proximal failure. A total of 87 procedures were identified in 40 patients, consisting of 23 initial placements and 64 revisions. Thirty-nine proximal catheter malfunctions were identified. Indications for shunt placement included Chiari II malformation (33%) and intraventricular hemorrhage (33%). Mean follow-up period was 5.5 years. Median time to shunt failure was 1.57 years. In the multivariate model, younger age at placement was associated with decreased time to proximal failure (hazard ratio [HR]=0.80 per increasing year of age, 95% confidence interval [CI] 0.64-0.98). Both anterior approach (HR=0.39, 95% CI 0.23-0.67) and farther distance to foramen of Monro (HR=0.02 per increasing 10mm, 95% CI 0.00-0.22) were associated with increased time to proximal failure when the catheter tip was located within the contralateral lateral ventricle. Optimizing outcomes in patients with shunt-dependent hydrocephalus continues to be a challenge. Despite unsatisfactory outcomes, particularly in the pediatric population, few conclusions can be drawn from studies assessing operative variables.

The Use of the Target Cancellation Task to Identify Eloquent Visuospatial Regions in Awake Craniotomies: Technical Note.

The success of awake craniotomies relies on the patient’s performance of function-specific tasks that are simple, quick, and reproducible. Intraoperative identification of visuospatial function through cortical and subcortical mapping has utilized a variety of intraoperative tests, each with its own benefits and drawbacks. In light of this, we developed a simple software program that aids in preventing neglect by simulating a target-cancellation task on a portable electronic device. In this report, we describe the interactive target cancellation task and have reviewed seven consecutive patients who underwent awake craniotomy for parietal and/or posterior temporal infiltrating brain tumors of the non-dominant hemisphere. Each of these patients performed target cancellation and line bisection tasks intraoperatively. The outcomes of each patient and testing scenario are described. Positive intraoperative cortical and subcortical sites involved with visuospatial processing were identified in three of the seven patients using the target cancellation and confirmed utilizing the line-bisection task. No identification of visuospatial function was accomplished utilizing the line-bisection task alone. Complete visuospatial function mapping was completed in less than 10 minutes in all patients. No patients had preoperative or postoperative hemineglect. Our findings highlight the feasibility of the target cancellation technique for use during awake craniotomy to aid in avoiding postoperative hemineglect. Target cancellation may offer an alternative method of cortical and subcortical visuospatial mapping in patients unable to perform other commonly used modalities.

Utilization of the O-arm after Ommaya reservoir placement

The authors demonstrate the utility of portable intraoperative CT scans for the rapid identification of ventricular catheter tip location after Ommaya reservoir placement. The O-arm (Medtronic Sofamor Danek, Memphis, TN, USA) was utilized to confirm ventricular catheter placement intraoperatively. Conventionally, a postoperative CT scan is obtained prior to Ommaya reservoir use to ensure proper catheter placement. By obtaining these images intraoperatively, revisions may be performed without the need for an additional surgical procedure, and the reservoir may be utilized immediately postoperatively.

White matter connections of the inferior parietal lobule: A study of surgical anatomy

Interest in the function of the inferior parietal lobule (IPL) has resulted in increased understanding of its involvement in visuospatial and cognitive functioning, and its role in semantic networks. A basic understanding of the nuanced white‐matter anatomy in this region may be useful in improving outcomes when operating in this region of the brain. We sought to derive the surgical relationship between the IPL and underlying major white‐matter bundles by characterizing macroscopic connectivity.

368 Anatomy and White Matter Connections of the Orbitofrontal Gyrus.

INTRODUCTION The orbitofrontal cortex is understood to have a role in outcome evaluation and risk assessment, and is commonly involved by infiltrative tumors. A detailed understanding of the exact location and nature of associated white tracts could go far to prevent postoperative morbidity related to declining capacity. Through diffusion tensor imaging (DTI)-based fiber tracking validated by gross anatomical dissection as ground truth, we have characterized these connections based on relationships to other well-known structures. METHODS Diffusion imaging from the Human Connectome Project for 10 healthy adult controls was used for tractography analysis. We evaluated the orbitofrontal cortex as a whole based on connectivity with other regions. All orbitofrontal cortex tracts were mapped in both hemispheres, and lateralization index was calculated with resultant tract volumes. Ten postmortem dissections were then performed using a modified Klingler technique to demonstrate the location of major tracts. RESULTS We identified 3 major connections of the orbitofrontal cortex: a bundle to the thalamus and anterior cingulate gyrus passing inferior to the caudate and medial to the vertical fibers of the thalamic projections; a bundle to the brainstem traveling lateral to the caudate and medial to the internal capsule; and radiations to the parietal and occipital lobes traveling with the inferior fronto-occipital fasciculus. There was no significant lateralization for any of the tracts described. CONCLUSION The orbitofrontal cortex is an important center for processing visual, spatial, and emotional information. Subtle differences in executive functioning following surgery for frontal lobe tumors may be better understood in the context of the fiber-bundle anatomy highlighted by this study.

Clinical significance of changes in pB-C2 distance in patients with Chiari Type I malformations following posterior fossa decompression: a single-institution experience.

OBJECT The coexistence of Chiari malformation Type I (CM-I) and ventral brainstem compression (VBSC) has been well documented, but the change in VBSC after posterior fossa decompression (PFD) has undergone little investigation. In this study the authors evaluated VBSC in patients with CM-I and determined the change in VBSC after PFD, correlating changes in VBSC with clinical status and the need for further intervention. METHODS Patients who underwent PFD for CM-I by the senior author from November 2005 to January 2013 with complete radiological records were included in the analysis. The following data were obtained: objective measure of VBSC (pB-C2 distance); relationship of odontoid to Chamberlains, McGregors, McRaes, and Wackenheims lines; clival length; foramen magnum diameter; and basal angle. Statistical analyses were performed using paired t-tests and a mixed-effects ANOVA model. RESULTS Thirty-one patients were included in the analysis. The mean age of the cohort was 10.0 years. There was a small but statistically significant increase in pB-C2 postoperatively (0.5 mm, p < 0.0001, mixed-effects ANOVA). Eleven patients had postoperative pB-C2 values greater than 9 mm. The mean distance from the odontoid tip to Wackenheims line did not change after PFD, signifying postoperative occipitocervical stability. No patients underwent transoral odontoidectomy or occipitocervical fusion. No patients experienced clinical deterioration after PFD. CONCLUSIONS The increase in pB-C2 in patients undergoing PFD may occur as a result of releasing the posterior vector on the ventral dura, allowing it to relax posteriorly. This increase appears to be well-tolerated, and a postoperative pB-C2 measurement of more than 9 mm in light of stable craniocervical metrics and a nonworsened clinical examination does not warrant further intervention.

Risk factors for surgical site infection after instrumented fixation in spine trauma.

Surgical site infection (SSI) represents a significant complication after instrumented fixation in spine trauma. Institutional practice changes have emphasized early fracture correction, shortened intraoperative times, early ambulation, and prompt nutritional supplementation. This retrospective study evaluates the senior authors experience of instrumented spinal trauma SSI occurring at a single Level I trauma center over two equal and contiguous time periods, 2005-2007 (before nutritional supplementation was added to the institutional protocol) and 2008-2010 (after nutritional supplementation was added). This study assessed whether SSI varied depending on the primary surgical site and/or by the chosen approach. Lastly, the incidence of SSI among demographic and other clinical variables was evaluated. In total, 358 patients underwent an index procedure for spinal trauma correction. Fourteen patients developed a SSI requiring reoperation for an incidence of 4.0%. In assessing nutritional supplementation, the probability of infection tended to be lower in the supplemented group (3.7%) than the pre-supplement group (4.3%), but this did not reach significance. The difference in approach for the cervical spine was statistically significant (p=0.045) with rates of infection via posterior approach at 8.1% and no infections via anterior approach. Presence of comorbidities (p=0.03) and time to surgery >3days (p=0.006) were predictors of developing SSI. Benefit is shown from early surgical correction of spinal trauma patients in the reduction of postoperative SSI. Nutritional supplementation may provide a small reduction in infections in the spine trauma population.