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Mitchel S. Berger, Ilona V. Garner, and Michael W. McDermott

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Edward F. Chang, Kunal P. Raygor, and Mitchel S. Berger

Classic models of language organization posited that separate motor and sensory language foci existed in the inferior frontal gyrus (Broca's area) and superior temporal gyrus (Wernicke's area), respectively, and that connections between these sites (arcuate fasciculus) allowed for auditory-motor interaction. These theories have predominated for more than a century, but advances in neuroimaging and stimulation mapping have provided a more detailed description of the functional neuroanatomy of language. New insights have shaped modern network-based models of speech processing composed of parallel and interconnected streams involving both cortical and subcortical areas. Recent models emphasize processing in “dorsal” and “ventral” pathways, mediating phonological and semantic processing, respectively. Phonological processing occurs along a dorsal pathway, from the posterosuperior temporal to the inferior frontal cortices. On the other hand, semantic information is carried in a ventral pathway that runs from the temporal pole to the basal occipitotemporal cortex, with anterior connections. Functional MRI has poor positive predictive value in determining critical language sites and should only be used as an adjunct for preoperative planning. Cortical and subcortical mapping should be used to define functional resection boundaries in eloquent areas and remains the clinical gold standard. In tracing the historical advancements in our understanding of speech processing, the authors hope to not only provide practicing neurosurgeons with additional information that will aid in surgical planning and prevent postoperative morbidity, but also underscore the fact that neurosurgeons are in a unique position to further advance our understanding of the anatomy and functional organization of language.

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John P. Andrews, Tarun Arora, Philip Theodosopoulos, and Mitchel S. Berger

BACKGROUND

Meningiomas of the atrium of the lateral ventricle present a unique operative challenge. Parietal transcortical approaches have been described with an oblique approach, but a strictly paramedian approach may offer advantages in a dominant hemisphere atrial meningioma.

OBSERVATIONS

The patient presented with several weeks of intermittent headaches. Magnetic resonance imaging (MRI) showed an enhancing intraventricular mass in the atrium of the left lateral ventricle. Three-dimensional reconstructions were created from a preoperative MRI, with 1-mm slices for neuronavigation. Diffusion tensor imaging (DTI) was obtained, and tracts were reconstructed in the patient’s three-dimensional brainspace. DTI tractography delineated a paramedian transparietal corridor devoid of functional white matter tracks. The patient was positioned supine, in a semislouch position. A left parietal craniotomy was performed. Neuronavigation identified a gyrus posterior to the sensory cortex, anterior to the optic radiations and medial to superior longitudinal and arcuate fasciculus fiber tracts. The tumor was debulked to allow mobilization to coagulate capsular blood supply. Gross total resection was achieved. The patient was discharged postoperatively on day 3 without neurological deficits.

LESSONS

A paramedian transparietal approach to a dominant hemisphere meningioma of the lateral ventricle can be a safe and effective way to resect tumors in this anatomically unique operative corridor.

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G. Evren Keles, Kathleen R. Lamborn, and Mitchel S. Berger

Object. The goal of this study was to perform a critical review of literature pertinent to low-grade gliomas of the cerebral hemisphere in adults and, on the basis of this review, to evaluate systematically the prognostic effect of extent of resection on survival and to determine if treatment-related guidelines could be established for patients in whom these tumors have been newly diagnosed. Quality of evidence for current treatment options, guidelines, and standards as well as methodological limitations were evaluated.

Methods. Several prognostic factors thought to affect outcome in patients with low-grade gliomas include the patient's age and neurological status, tumor volume and histological characteristics, and treatment-related variables such as timing of surgical intervention, extent of resection, postoperative tumor volume, and radiation therapy. Patient age and the histological characteristics of the lesion are generally accepted prognostic factors. Among treatment-related factors, timing and extent of resection are controversial because of the lack of randomized controlled trials addressing these issues and the difficulty in obtaining information from available studies that have methodological limitations.

All English-language studies on low-grade gliomas published between January 1970 and April 2000 were reviewed. Thirty studies that included statistical analyses were further evaluated with regard to the prognostic effect of extent of resection. Of these 30 studies, those that included pediatric patients, unless adults were analyzed separately, were excluded from further study because of the favorable outcome associated with the pediatric age group. Also excluded were studies including pilocytic and gemistocytic astrocytomas, because the natural histories of these histological subtypes are significantly different from that of low-grade gliomas. Series in which there were small numbers of patients (< 75) were also excluded. Results for oligodendrogliomas are reported separately.

Currently, for patients with low-grade glial tumors located in the cerebral hemisphere, the only management standard based on high-quality evidence is tissue diagnosis. All other treatment methods are practice options supported by evidence that is inconclusive or conflicting. The majority of published series that the authors identified had design-related limitations including a small study size, a small number of events (that is, deaths for survival studies), inclusion of pediatric patients, and/or inclusion of various histological types of tumors with different natural histories. Of the 30 series addressing the issue of timing and extent of surgery, almost all had additional design limitations. Methods used to determine the extent of resection were subjective and qualitative in almost all studies. Only five of the 30 series met the authors' criteria, and these studies are discussed in detail.

Conclusions. Management of low-grade gliomas is controversial and practice parameters are ill defined. This is caused by limited knowledge regarding the natural history of these tumors and the lack of high-quality evidence supporting various treatment options. Although a prospective randomized study seems unlikely, both retrospective matched studies and prospective observational trials will improve the clinician's ability to understand the importance of various prognostic factors.

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Victoria T. Trinh, Jason M. Davies, and Mitchel S. Berger

OBJECT

The object of this study was to examine how procedural volume and patient demographics impact complication rates and value of care in those who underwent biopsy or craniotomy for supratentorial primary brain tumors.

METHODS

The authors conducted a retrospective cohort study using data from the Nationwide Inpatient Sample (NIS) on 62,514 admissions for biopsy or resection of supratentorial primary brain tumors for the period from 2000 to 2009. The main outcome measures were in-hospital mortality, routine discharge proportion, length of hospital stay, and perioperative complications. Associations between these outcomes and hospital or surgeon case volumes were examined in logistic regression models stratified across patient characteristics to control for presentation of disease and comorbid risk factors. The authors further computed value of care, defined as the ratio of functional outcome to hospital charges.

RESULTS

High-case-volume surgeons and hospitals had superior outcomes. After adjusting for patient characteristics, high-volume surgeon correlated with reduced complication rates (OR 0.91, p = 0.04) and lower in-hospital mortality (OR 0.43, p < 0.0001). High-volume hospitals were associated with reduced in-hospital mortality (OR 0.76, p = 0.003), higher routine discharge proportion (OR 1.29, p < 0.0001), and lower complication rates (OR 0.93, p = 0.04). Patients treated by high-volume surgeons were less likely to experience postoperative hematoma, hydrocephalus, or wound complications. Patients treated at high-volume hospitals were less likely to experience mechanical ventilation, pulmonary complications, or infectious complications. Worse outcomes tended to occur in African American and Hispanic patients and in those without private insurance, and these demographic groups tended to underutilize high-volume providers.

CONCLUSIONS

A high-volume status for hospitals and surgeons correlates with superior value of care, as well as reduced in-hospital mortality and complications. These findings suggest that regionalization of care may enhance patient outcomes and improve value of care for patients with primary supratentorial brain tumors.

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Nader Sanai, Juan Martino, and Mitchel S. Berger

Object

The impact of parietal lobe gliomas is typically studied in the context of parietal lobe syndromes. However, critical language pathways traverse the parietal lobe and are susceptible during tumor resection. The authors of this study reviewed their experience with parietal gliomas to characterize the impact of resection and the morbidity associated with language.

Methods

The study population included adults who had undergone resection of parietal gliomas of all grades. Tumor location was identified according to a proposed classification system for parietal region gliomas. Low- and high-grade tumors were volumetrically analyzed using FLAIR and T1-weighted contrast-enhanced MR imaging.

Results

One hundred nineteen patients with parietal gliomas were identified—34 with low-grade gliomas and 85 with high-grade gliomas. The median patient age was 45 years, and most patients (53) presented with seizures, whereas only 4 patients had an appreciable parietal lobe syndrome. The median preoperative tumor volume was 31.3 cm3, the median extent of resection was 96%, and the median postoperative tumor volume was 0.9 cm3. Surprisingly, the most common early postoperative neurological deficit was dysphasia (16 patients), not weakness (12 patients), sensory deficits (14 patients), or parietal lobe syndrome (10 patients). A proposed parietal glioma classification system, based on surgical anatomy, was predictive of language deficits.

Conclusions

This is the largest reported experience with parietal lobe gliomas. The findings suggested that parietal language pathways are compromised at a surprisingly high rate. The proposed parietal glioma classification system is predictive of postoperative morbidity associated with language and can assist with preoperative planning. Taken together, these data emphasize the value of identifying language pathways when operating within the parietal lobe.

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Andrew T. Dailey, Guy M. McKhann II, and Mitchel S. Berger

✓ Mutism following posterior fossa tumor resection in pediatric patients has been previously recognized, although its pathophysiology remains unclear. A review of the available literature reveals 33 individuals with this condition, with only a few adults documented in the population. All of these patients had large midline posterior fossa tumors.

To better understand the incidence and anatomical substrate of this syndrome, the authors reviewed a 7-year series of 110 children who underwent a posterior fossa tumor resection. During that time, nine (8.2%) of the 110 children exhibited mutism postoperatively. They ranged from 2.5 to 20 years of age (mean 8.1 years) and became mute within 12 to 48 hours of surgery. The period of mutism lasted from 1.5 to 12 weeks after onset: all children had difficulty coordinating their oral pharyngeal musculature as manifested by postoperative drooling and inability to swallow. Further analysis of these cases revealed that all children had splitting of the entire inferior vermis at surgery, as confirmed on postoperative magnetic resonance studies. Lower cranial nerve function was intact in all nine patients.

Current concepts of cerebellar physiology emphasize the importance of the cerebellum in learning and language. The syndrome described resembles a loss of learned activities, or an apraxia, of the oral and pharyngeal musculature. To avoid the apraxia, therefore, the inferior vermis must be preserved. For large midline tumors that extend to the aqueduct, a combined approach through the fourth ventricle and a midvermis split may be used to avoid injuring the inferior vermis.

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Mitchel S. Berger, Wendy A. Cohen, and George A. Ojemann

✓ Brain maps derived intraoperatively from patients undergoing tumor resection were correlated retrospectively with magnetic resonance (MR) images with respect to the precise localization of the motor cortex in an attempt to identify useful preoperative MR imaging landmarks that correspond to functional brain regions. Superior axial T2-weighted MR images consistently localized the central sulcus, whereas parasagittal and far-lateral sagittal images readily identified the rolandic (sensorimotor) cortex, as a functional unit, based on the cingulate-marginal sulcus and insula, respectively. It is therefore concluded that multiplanar MR images may serve as a useful preoperative planning aid prior to removing intrinsic brain tumors within or adjacent to the motor cortex.

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Mitchel S. Berger

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Mark Bernstein