Awake craniotomy with intraoperative electrical mapping is a reliable method to minimize the risk of permanent deficit during surgery for low-grade glioma located within eloquent areas classically considered inoperable. However, it could be argued that preservation of functional sites might lead to a lesser degree of tumor removal. To the best of our knowledge, the extent of resection has never been directly compared between traditional and awake procedures.

OBJECTIVE: We report for the first time a series of patients who underwent 2 consecutive surgeries without and with awake mapping.

METHODS: Nine patients underwent surgery for a low-grade glioma in functional sites under general anesthesia in other institutions. The resection was subtotal in 3 cases and partial in 6 cases. There was a postoperative worsening in 3 cases. We performed a second surgery in the awake condition with intraoperative electrostimulation. The resection was performed according to functional boundaries at both the cortical and subcortical levels.

RESULTS: Postoperative magnetic resonance imaging showed that the resection was complete in 5 cases and subtotal in 4 cases (no partial removal) and that it was improved in all cases compared with the first surgery (P = .04). There was no permanent neurological worsening. Three patients improved compared with the presurgical status. All patients returned to normal professional and social lives.

CONCLUSION: Our results demonstrate that awake surgery, known to preserve the quality of life in patients with low-grade glioma, is also able to significantly improve the extent of resection for lesions located in functional regions.

Recent surgical studies have demonstrated that the extent of resection is significantly correlated with median survival in WHO Grade II gliomas. Consequently, thanks to advances in intraoperative functional mapping, the authors questioned whether it is actually necessary to leave a “security” margin around eloquent structures.
Methods. The authors first reviewed the classic literature, especially that based on epilepsy surgery and functional neuroimaging techniques, which led them to propose the rule of a security margin. Second, they detailed new developments in the field of intrasurgical electrical mapping, especially with regard to subcortical stimulation of the projection and long-distance association pathways. On the basis of these advances, the removal of gliomas according to functional boundaries has recently been suggested, with no margin around eloquent structures.
Results. Comparative results showed that the rate of permanent deficit was similar with or without a security margin, that is, < 2%. However, a higher rate of transient neurological worsening in the immediate postsurgical period was associated with the absence of a margin, with recovery following adapted rehabilitation. On the other hand, the extent of resection was in essence improved with no margin.
Conclusions. This no-margin technique, based on the subpial dissection, and the repetition of both cortical and subcortical stimulation to preserve eloquent cortex as well as the white matter tracts (U-fibers, projection pathways, and long-distance connectivity) allow optimization of the extent of resection while preserving the quality of life (despite transitory impairment) thanks to mechanisms of brain plasticity.

Low-grade gliomas ([LGGs] WHO Grade II) are slow-growing intrinsic cerebral lesions that diffusely infiltrate the brain parenchyma along white matter tracts and almost invariably show a progression toward malignancy. The treatment of these tumors forces the neurosurgeon to face uncommon difficulties and is still a subject of debate. At the authors’ institution, resection is the first option in the treatment of LGGs. It requires the combined efforts of a multidisciplinary team of neurosurgeons, neuroradiologists, neuropsychologists, and neurophysiologists, who together contribute to the definition of the location, extension, and extent of functional involvement that a specific lesion has caused in a particular patient. In fact, each tumor induces specific modifications of the brain functional network, with high interindividual variability. This requires that each treatment plan is tailored to the characteristics of the tumor and of the patient. Consequently, surgery is performed according to functional and anatomical boundaries to achieve the maximal resection with maximal functional preservation. The identification of eloquent cerebral areas, which are involved in motor, language, memory, and visuospatial functions and have to be preserved during surgery, is performed through the intraoperative use of brain mapping techniques. The use of these techniques extends surgical indications and improves the extent of resection, while minimizing the postoperative morbidity and safeguarding the patient’s quality of life.

In this paper the authors present their paradigm for the surgical treatment of LGGs, focusing on the intraoperative neurophysiological monitoring protocol as well as on the brain mapping technique. They briefly discuss the results that have been obtained at their institution since 2005 as well as the main critical points they have encountered when using this approach.

Methods
Twenty-four patients underwent surgery for an insular Grade II glioma involving the dominant hemisphere (22 left, 2 right), revealed by seizures in all but 1 case. The preoperative neurological examination result was normal in 17 patients (71%), whereas 7 patients presented with language disorders detected using an accurate language assessment performed by a speech therapist. All surgeries were performed on awake patients utilizing intra-operative language mapping involving cortical and subcortical stimulation.

Results
There were no intrasurgical complications or postsurgical sensorimotor deficits. Despite an immediate postoperative language worsening in 12 cases (50%), all patients recovered to a normal status within 3 months, and 6 cases even improved in comparison with their preoperative examination results. The 24 patients returned to normal social and professional lives. Moreover, the surgery had a favorable impact on epilepsy in all but 4 cases (83%). On control MR imaging, 62.5% of resections were total or subtotal. Three patients underwent a second or third awake surgery, with no additional deficit. All but 2 patients (92%) are alive after a mean follow-up of 3 years (range 3–133 months).

Conclusions
Although insular surgery was long believed to be too risky, the present results show that the rate of permanent deficit, especially dysphasia, following resection of Grade II gliomas involving the dominant insula has been dramatically reduced (none in this patient series), thanks to the systematic use of intraoperative awake mapping, even in cases of repeated operations. Furthermore, patient quality of life may be improved due to a decrease of epilepsy after surgery. Thus, the authors suggest systematically considering resection when an insular Grade II glioma is diagnosed after seizures in a patient with no or mild deficit, even a glioma invading the dominant hemisphere.

Background

Controversy still exists about neural basis underlying writing and its relation with the sites subserving oral language. Our objective is to study functional areas involved in writing network, based on the observations of different postoperative writing disorders in a population of patients without preoperative agraphia.

Methods

We analyzed the postoperative agraphia profiles in 15 patients who underwent surgery for cerebral LGGs in functional language areas, using electrical mapping under local anesthesia. These profiles were then correlated to the sites of the lesions, shown by preoperative cerebral imaging.

Results

Our findings showed that (1) spoken language and writing functions could be dissociated, and that (2) writing is subserved, at least partially, by a network of 5 areas located in the dominant hemisphere for language: the superior parietal region, the supramarginalis gyrus, the second and third frontal convolutions, the supplementary motor area, and the insula. Each of these areas seems to have a different role in writing, which will be detailed in this article. However, among the patients, only those with lesions of the supplementary motor area did not recover from agraphia in the postoperative period (in 50% of cases).

Conclusions

On the basis of these results, and in the light of the recent literature, we discuss the relevance of each area in this anatomo-functional network as well as the clinical implications of such better knowledge of the neural basis of writing, especially for brain surgery and functional rehabilitation.