Perspectives

Commentary on:Minimally Invasive Endoscopic Resection ofIntraparenchymal Brain Tumorsby Plaha et al. pp. 1198-1208.

Hugues Duffau, M.D., Ph.D.

Professor and ChairmanDepartment of Neurosurgery

Hôpital Gui de ChauliacMontpellier University Medical Center

Is There a Place for Endoscopy in Glioma Surgery?

Hugues Duffau

he recent neuro-oncological literature strongly supports

the significant impact of surgery on overall survival in

T patients with glioma, both concerning high-grade gliomas

(17, 21) and low-grade gliomas (1, 22). The goal of extensiveresection is not only to increase survival but also to preserve or

even to improve quality of life (5), especially by controlling epi-lepsy (16). To this end, technological advances have contributed

to an optimization of the benefit-to-risk ratio of surgery (e.g.,functional neuroimaging such as functional magnetic resonance

imaging [MRI; fMRI] and diffusion tensor imaging [DTI]) as wellas awake procedure with intraoperative electrophysiologic map-

ping (3).

In this issue of WORLD NEUROSURGERY, Plaha et al. (18)report a series with 50 consecutive fully endoscopic intra-

parenchymal tumor resections—most of them being a glioma.More than 95% resection was performed in 70% of patients with

total resection in 48% of cases. The investigators conclude thatminimally invasive endoscopic resection is technically feasible

and allows the achievement of good tumor removal. They have tobe congratulated for their favorable results. It is important to add

new tools to the armamentorium against gliomas. However, a

few issues should be extensively discussed before to claim thatendoscopy has some advantages versus a traditional technique.

First, in the study by Plaha et al. (18), the extent of resection has

been calculated on postoperative computed tomographic scan, atleast regarding high-grade gliomas (i.e., most tumors in this se-

ries). It has been extensively demonstrated that MRI was

Key words- Endoscopic- Intraparenchymal brain tumors- Minimally invasive

Abbreviations and AcronymsDTI: Diffusion tensor imagingfMRI: Functional MRIMRI: Magnetic resonanceimagingWHO: World HealthOrganization

1020 www.SCIENCEDIRECT.com WORLD NEU

mandatory to objectively evaluate the actual volume of residual

tumor, even in glioblastoma (23). As a consequence, it isimpossible to state that the overall mean percent resection

was 96%.

Second, although Plaha et al. (18) claimed that endoscopic

resection was safe, there were 3 wound infections (6%) in thisseries, which is a high rate in comparison with the modern

literature in neuro-oncology (many series have no or exceptionalwound infections). In my personal experience with more than

500 awake surgerie for gliomas, only 3 wound infections

occurred (0.6%), despite wide bone flaps to obtain a positiveelectrical mapping (11). Furthermore, results of accurate neuro-

logical examinations (motor, sensory, visuospatial, languagefunctions) and extensive neuropsychologic assessments (cogni-

tive and emotional functions) before and after tumor resectionshould be provided before concluding that the surgery was safe

(8). For example, the investigators used the World Health Orga-nization (WHO) functional status immediately postoperative at

discharge, which is not adapted. WHO grade 0 means that thepatient is “asymptomatic (fully active, able to carry on all pre-

disease activities without restriction)” (15). In essence, it is notpossible to evaluate whether the patient is fully active (especially

able to work full time) at discharge, because it is too early. Finally,regarding specifically patients with low-grade glioma, that is,

patients with a long survival beyond 10 years (1) and in whomquality of life should absolutely be preserved (12). In the series by

Plaha et al. (18). 1 of the 5 patients with low-grade glioma hadinfarct with new postoperative deficit. The risk is now less than

Department of Neurosurgery, Hôpital Gui de Chauliac, Montpellier UniversityMedical Center; and the National Institute for Health and Medical Research

(INSERM), U1051 Laboratory, Team “Brain Plasticity, Stem Cells and Glial Tumors,” Institutefor Neurosciences of Montpellier, Montpellier University Medical Center, Montpellier, France

To whom correspondence should be addressed: Hugues Duffau, M.D., Ph.D.[E-mail: h-duffau@chu-montpellier.fr]

Citation: World Neurosurg. (2014) 82, 6:1020-1022.http://dx.doi.org/10.1016/j.wneu.2014.08.037

ROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.08.037

PERSPECTIVES

2% in huge experiences with hundreds of low-grade patientswhen using awake mapping (11, 19).

From a technical point of view, Plaha et al. (18) used a navigation

guidance system, and chose the shortest distance to the tumor.Nonetheless, to select the closest cortical surface for surgical

access is not always the best option, because this entry doormay correspond to an eloquent epicenter, and the underlying

white matter tracts could be crucial for neurological functions (2).The incorporation of fMRI and DTI data into the neuronavigational

system cannot allow the planning of a safe trajectory with a highlevel of specificity and sensitivity with regard to the detection of

critical structures. Because of numerous methodologic limita-

tions, fMRI is not a reliable tool, as extensively demonstrated bycomparing preoperative fMRI and intraoperative electro-

stimulation mapping (13). In the same vein, correlation betweenDTI and direct stimulation of the subcortical pathways showed

that the reliability of DTI was only about 82%, and that negativetractography did not rule out the persistence of a fiber tract,

especially when invaded by the tumor (9, 14).

In addition, Plaha et al. (18) wrote that they tried to identify theplane between the tumor and the surrounding brain. By defini-

tion, this is impossible in diffuse (high-grade or low-grade) gli-omas, which are not a tumor mass but an invasive disease of the

brain, migrating along the white matter bundles (5, 7). This is thereason why neurosurgeons involved in glioma removal should

switch from an image-guided resection to a functional-mappingguided resection (i.e., to continue to remove the parenchyma

invaded by tumoral cells until eloquent boundaries have beenencountered, at cortical and subcortical levels) (6). At present,

the sole surgical technique able to provide such functional in-formation in real-time throughout the surgical resection with re-

gard to cortical epicenters as well as white matter tracts is theawake procedure with direct electrostimulation mapping. In a

recent meta-analysis with more than 8000 low-grade and high-grade gliomas, it has been shown that this method enabled an

increase of that extent of resection, yet significantly decreasingthe rate of permanent neurological deficits—even in eloquent

WORLD NEUROSURGERY 82 [6]: 1020-1022, DECEMBER 2014

areas (3). As a consequence, this technique should be universallyimplemented as standard of care for glioma surgery (3). There-

fore, it does not seem reasonable to conclude that endoscopicresection has some advantages versus a traditional technique

before comparing this new tool to awake procedures.

Finally, it is puzzling to note that there were no insular tumors inthe series by Plaha et al. (18). This is a possible bias of selection,

because gliomas are known to frequently involve the insular lobe(10). Interestingly, in several recent studies (4, 20) focusing on

surgery for insular gliomas, one of the main limitation (beyond theinvasion of the anterior-perforating substance and the risk of

damaging lenticulostriate arteries) was the removal of the portion

of the tumor located in the posterosuperior part of the insula,especially in the dominant hemisphere. This corresponds to the

zone II according to the classification proposed by Sanai et al.(20). This zone is significantly associated with the smallest extent

of resection. This approach is difficult, as it is deeper than theanterior insula. The bifurcation of the superficial sylvian vein is

often located at its level, making the splitting of the sylvianfissure very complex. In addition, retraction or removal of the

opercula is questionable, because these structures are ofteneloquent, at least within the dominant hemisphere. The mid-

posterior part of the superior temporal gyrus or ventral premotorcortex are usually essential for language (24). Therefore, it could

be suggested to use the endoscope at the end of removal ofinsular/paralimbic tumors to explore more specifically and more

accurately this zone II to improve its resection without increasingthe rate of postoperative morbidity.

In conclusion, although it is interesting to benefit from a new tool

in neuro-oncology, it is nonetheless crucial to validate first theactual usefulness of endoscopy and to acknowledge its limita-

tions, with the aim of selecting possible specific indications ofthis method for glioma surgery (e.g., for tumors involving the

posterior insula). “Minimally invasive technique” does not meanthat the surgical approach should be perform through a small

craniotomy, but should mean that the quality of life has beenpreserved and survival has been significantly increased.

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To create a principal for the global commuand channels

To serve as a forum fand issues for global

To act as a primary in

To enhance and movfuture neurosurgical

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international information conduit for establishing modernity of neuronity through contemporary and innovative journalistic communication

or scientific, clinical, educational, social, cultural, economic, and poli neurosurgery

tellectual catalyst for the field

e toward complete global communication related to all aspects of curpractice, research, and progress

MISSION STATEM

WORLD NEUROSURGERY, http://

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