Cordell M Baker

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.

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.

Anatomy and white matter connections of the orbitofrontal gyrus

OBJECTIVE The orbitofrontal cortex (OFC) is understood to have a role in outcome evaluation and risk assessment and is commonly involved with infiltrative tumors. A detailed understanding of the exact location and nature of associated white matter tracts could significantly improve postoperative morbidity related to declining capacity. Through diffusion tensor imaging-based fiber tracking validated by gross anatomical dissection as ground truth, the authors 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. The OFC was evaluated as a whole based on connectivity with other regions. All OFC tracts were mapped in both hemispheres, and a 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 The authors identified 3 major connections of the OFC: 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. CONCLUSIONS The OFC 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.

Dural Closure in Confined Spaces of the Skull Base with Nonpenetrating Titanium Clips

BACKGROUND Dural repair in areas with limited operative maneuverability has long been a challenge in skull base surgery. Without adequate dural closure, postoperative complications, including cerebrospinal fluid (CSF) leak and infection, can occur. OBJECTIVE To show a novel method by which nonpenetrating, nonmagnetic titanium microclips can be used to repair dural defects in areas with limited operative access along the skull base. METHODS We reviewed 53 consecutive surgical patients in whom a dural repair technique utilizing titanium microclips was performed from 2013 to 2016 at our institution. The repairs primarily involved difficult-to-reach dural defects in which primary suturing was difficult or impractical. A detailed surgical technique is described in 3 selected cases involving the anterior, middle, and posterior fossae, respectively. An additional 5 cases are provided in more limited detail to demonstrate clip artifact on postoperative imaging. Rates of postoperative CSF leak and other complications are reported. RESULTS The microclip technique was performed successfully in 53 patients. The most common pathology in this cohort was skull base meningioma (32/53). Additional surgical indications included traumatic dural lacerations (9/53), nonmeningioma tumors (8/53), and other pathologies (4/53). The clip artifact present on postoperative imaging was minor and did not interfere with imaging interpretation. CSF leak occurred postoperatively in 3 (6%) patients. No obvious complications attributable to microclip usage were encountered. CONCLUSION In our experience, intracranial dural closure with nonpenetrating, nonmagnetic titanium microclips is a feasible adjunct to traditional methods of dural repair.

Frontal keyhole craniotomy for resection of low- and high-grade gliomas

BACKGROUND Minimally invasive techniques are increasingly being used to access intra-axial brain lesions. OBJECTIVE To describe a method of resecting frontal gliomas through a keyhole craniotomy and share the results with these techniques. METHODS We performed a retrospective review of data obtained on all patients undergoing resection of frontal gliomas by the senior author between 2012 and 2015. We describe our technique for resecting dominant and nondominant gliomas utilizing both awake and asleep keyhole craniotomy techniques. RESULTS After excluding 1 patient who received a biopsy only, 48 patients were included in the study. Twenty-nine patients (60%) had not received prior surgery. Twenty-six patients (54%) were diagnosed with WHO grade II/III tumors, and 22 patients (46%) were diagnosed with glioblastoma. Twenty-five cases (52%) were performed awake. At least 90% of the tumor was resected in 35 cases (73%). Three of 43 patients with clinical follow-up experienced permanent deficits. CONCLUSION We provide our experience in using keyhole craniotomies for resecting frontal gliomas. Our data demonstrate the feasibility of using minimally invasive techniques to safely and aggressively treat these tumors.

The crossed frontal aslant tract: A possible pathway involved in the recovery of supplementary motor area syndrome

Supplementary motor area (SMA) syndrome is a constellation of temporary symptoms that may occur following tumors of the frontal lobe. Affected patients develop akinesia and mutism but often recover within weeks to months. With our own case examples and with correlations to fiber tracking validated by gross anatomical dissection as ground truth, we describe a white matter pathway through which recovery may occur.

Rates of Seizure Freedom After Surgical Resection of Diffuse Low-Grade Gliomas

OBJECTIVE Patients with diffuse low-grade gliomas (DLGGs) typically present with seizures. We sought to review the neurosurgical literature for seizure outcome after resection of these tumors. METHODS Using PubMed, we identified surgical series reporting seizure freedom rates for grade II astrocytoma, oligoastrocytoma, and oligodendroglioma. Inclusion criteria included seizure outcomes reported specifically for DLGGs and at least 10 patients with follow-up data. RESULTS Twelve articles met the inclusion criteria. The median seizure-free rate after surgery in these patients was 71%, with an interquartile range of 64%-82%. In 10 studies, more than 60% of patients were seizure free. Studies used varying reporting times for seizure outcome determination. In the 6 studies that reported postoperative antiepileptic medication use, 5%-69% of seizure-free patients were weaned off these agents (median, 32%). The durability of seizure freedom has not been clearly studied to date. The most commonly reported prognostic factor for seizure freedom after resection was increasing extent of resection. CONCLUSIONS Among articles reporting seizure outcomes after resection of DLGG, the median seizure-free rate was 71% (interquartile range, 64%-82%). Seizure freedom is likely associated with extent of resection.

Method for temporal keyhole lobectomies in resection of low- and high-grade gliomas

OBJECTIVE The purpose of this study was to describe a method of resecting temporal gliomas through a keyhole lobectomy and to share the results of using this technique. METHODS The authors performed a retrospective review of data obtained in all patients in whom the senior author performed resection of temporal gliomas between 2012 and 2015. The authors describe their technique for resecting dominant and nondominant gliomas, using both awake and asleep keyhole craniotomy techniques. RESULTS Fifty-two patients were included in the study. Twenty-six patients (50%) had not received prior surgery. Seventeen patients (33%) were diagnosed with WHO Grade II/III tumors, and 35 patients (67%) were diagnosed with a glioblastoma. Thirty tumors were left sided (58%). Thirty procedures (58%) were performed while the patient was awake. The median extent of resection was 95%, and at least 90% of the tumor was resected in 35 cases (67%). Five of 49 patients (10%) with clinical follow-up experienced permanent deficits, including 3 patients (6%) with hydrocephalus requiring placement of a ventriculoperitoneal shunt and 2 patients (4%) with weakness. Three patients experienced early postoperative anomia, but no patients had a new speech deficit at clinical follow-up. CONCLUSIONS The authors provide their experience using a keyhole lobectomy for resecting temporal gliomas. Their data demonstrate the feasibility of using less invasive techniques to safely and aggressively treat these tumors.

Vertebral artery injury in patients with isolated transverse process fractures

We sought to assess the rate of CTA-diagnosed vertebral artery injury in patients with isolated transverse process fractures, with and without extension into the transverse foramen, in the blunt-trauma population served by our hospital. We queried our universities trauma registry between January 2009 and July 2014 for ICD-9 codes pertaining to cervical spine fractures. Of 330 patients identified, 45 patients had fractures limited to the transverse process and were selected for the study population. For each patient identified, demographics, injury mechanism, imaging reports, angiography findings, and treatments were recorded. In total, 69 fractures were identified in 45 patients. Of the 45 patients, 15 (33%) had transverse process fractures at multiple cervical levels. 23/45 (51%) patients had at least one fracture extending into TF. Four patients with transverse process fractures and one patient without transverse process fractures were diagnosed with vertebral artery injury by CT angiogram (17.4% vs. 4.5%, p=0.35). The number of transverse process fractures in patients with VAI was greater than those without VAI (3.0 vs. 1.4, p<0.001). None of the 30 patients with any one-level TPF (with or without extension into TF) was diagnosed with VAI (p=0.003). None of 17 patients with isolated C7-level TPFs were diagnosed with VAI (p=0.15). The incidence of cervical VAI was greater in patients with multiple-level TPFs than in patients with single-level TPFs. While patients with a single, isolated TPF have a low probability of VAI, patients with numerous TPF fractures may benefit from CTA.

Common Disconnections in Glioma Surgery: An Anatomic Description

Within the surgical treatment of glioma, extended survival is predicated upon extent of resection which is limited by proximity and/or invasion of eloquent structures. Diffusion tensor imaging (DTI) tractography is a very useful tool for guiding supramaximal surgical resection while preserving eloquence. Although gliomas can vary significantly in size, shape, and invasion of functionally significant brain tissue, typical surgical disconnection patterns emerge. In this study, our typical surgical paradigm is outlined. We describe our surgical philosophy for resecting gliomas supramaximally summarized as define, divide, and destroy with the adjuvant utilization of neuronavigation and DTI. We describe the most common disconnections involved in glioma surgery at our institution; specifically, delineating tumor disconnections involving the medial posterior frontal, lateral posterior frontal, posterior temporal, anterior occipital, medial parietal, and insular regions. Although gliomas are highly variable, common patterns emerge in relation to the necessary disconnections required to preserve eloquent brain while maximizing the extent of resection.