Strategies to Maximize Resection of Complex, or High Surgical Risk, Low-grade Gliomas

Jessica A. Wilden, M.D.; Jason Voorhies, M.D.; Kristine M. Mosier, D.M.D., Ph.D.; Darren P. O'Neill, M.D.; Aaron A. Cohen-Gadol, M.D., M.Sc.

Disclosures

Neurosurg Focus. 2013;34(2):e5 

In This Article

Abstract and Introduction

Abstract

Object. Early and aggressive resection of low-grade gliomas (LGGs) leads to increased overall patient survival, decreased malignant progression, and better seizure control. This case series describes the authors' approach to achieving optimal neurological and surgical outcomes in patients referred by outside neurosurgeons for stereotactic biopsy of tumors believed to be complex or a high surgical risk, due to their diffuse nature on neuroimaging and their obvious infiltration of functional cortex.

Methods. Seven patients underwent individualized neuroimaging evaluation preoperatively, which included routine brain MRI with and without contrast administration for intraoperative neuronavigation, functional MRI with speech and motor mapping, diffusion tensor imaging to delineate white matter tracts, and MR perfusion to identify potential foci of higher grade malignancy within the tumor. Awake craniotomy with intraoperative motor and speech mapping was performed in all patients. Tumor removal was initiated through a transsylvian approach for insular lesions, and through multiple corticotomies in stimulation-confirmed noneloquent areas for all other lesions. Resection was continued until neuronavigation indicated normal brain, cortical or subcortical stimulation revealed functional cortex, or the patient began to experience a minor neurological deficit on intraoperative testing.

Results. Gross-total resection was achieved in 1 patient and subtotal resection (> 80%) in 6 patients, as assessed by postoperative MRI. Over the average follow-up duration of 31 months, no patient experienced a progression or recurrence. Long-term seizure control was excellent in 6 patients who achieved Engel Class I outcomes. Neurologically, all 7 patients experienced mild temporary deficits or seizures that completely resolved, and 1 patient continues to have mild expressive aphasia.

Conclusions. Significant resection of diffuse, infiltrating LGGs is possible, even in presumed eloquent cortex. Aggressive resection maximizes seizure control and does not necessarily cause permanent neurological deficits. Individualized preoperative neuroimaging evaluation, including tractography and awake craniotomy with intraoperative speech and motor mapping, is an essential tool in achieving these outcomes.

Introduction

Low-grade gliomas account for approximately 15% of all primary brain and CNS tumors in adults.[7] These gliomas are classified based on histology and include WHO Grade I and II gliomas.[26] Grade II gliomas present their own set of therapeutic challenges and will be discussed further. The most common subtypes of Grade II gliomas are astrocytoma, oligodendroglioma, and oligoastrocytoma.[31] The majority of adults with these tumors are diagnosed between the ages of 20 and 64 years, with a median age of 39 years,[11] and the diagnosis is frequently made among otherwise healthy and productive people. Although LGGs are more histologically and radiographically benign than their high-grade counterparts, many patients eventually die of their disease due to tumor progression and/or malignant transformation.[8] The average overall survival for patients with LGGs is approximately 6 years, but up to one-fourth of patients live 20 years after diagnosis,[11] which emphasizes the importance of maintaining patient quality of life when intervening.

Favorable prognostic factors in a 2006 analysis of patients with LGGs included female sex, younger age, Caucasian race, histology, and surgery as the initial treatment.[11] Extent of resection is now a widely accepted factor that influences overall survival, progression-free survival, and malignant transformation in these gliomas.[31] Gross-total resection of LGGs may lower the rate of histological progression nearly 2-fold and alter the natural history of the disease by decreasing tumor burden and therefore its oncological potential.[8] Even if GTR is not achieved, maximal tumor resection has proven more effective than minimal resection at extending overall and progression-free survival.[36] Postoperative neurological deficits have become increasingly uncommon with the use of specialized preoperative and intraoperative neuroimaging,[30,40] as well as intraoperative motor and speech mapping.[6,12] When deficits do occur, they are usually temporary, and patients tend to recover fully without adverse affects on their long-term quality of life.[4,12,36]

Persistent seizures can also adversely affect quality of life in this patient population. Although LGGs can cause headaches or progressive neurological decline such as weakness, sensory loss, apraxia, or aphasia, 60%–80% of patients harboring LGGs initially experience a seizure; thus, seizures are the most common presenting symptom.[22,31] Generalized seizures are the most common type and are often medically refractory.[10] Some authors advocate for the use of intraoperative electrocorticography to assist in the resection of epileptogenic foci beyond the actual tumor boundaries and maximize long-term seizure control.[2,15] Given all the available data, traditional treatment options including observation with serial neuroimaging or diagnostic biopsy followed by observation, radiation, and/or chemotherapy alone, are now frequently reserved for patients with medical comorbidities who are unable to tolerate aggressive surgery.

Maintaining a satisfactory quality of life for patients with LGGs is paramount. Whenever feasible, early and maximal resection should be considered. The purpose of this case series is to describe the modalities used at our institution to achieve reasonable clinical and surgical outcomes in patients whose epileptogenic tumors were considered high surgical risk by referring providers, due to the presumed infiltration of eloquent cortex and their relative diffuse character on neuroimaging.

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