Glioma surgery

see US National Comprehensive Cancer Network glioma surgery guidelines.

see High-grade glioma surgery.

see Low-grade glioma surgery.

The optimal surgical management of gliomas requires a balance between surgical cytoreduction and preservation of neurological function. Preoperative functional neuroimaging, such as functional MRI (fMRI) and diffusion tensor imaging (DTI), has emerged as a possible tool to inform patient selection and surgical planning. However, evidence that preoperative fMRI or DTI improves the extent of resection, limits neurological morbidity, and broadens surgical indications in classically eloquent areas is lacking. In a review, Azad and Duffau described facets of functional neuroimaging techniques that may limit their impact on neurosurgical oncology and critically evaluate the evidence supporting fMRI and DTI for patient selection and operative planning in glioma surgery. The authors also propose alternative applications for functional neuroimaging in the care of glioma patients 1).

Glioma surgery is an essential part of glioma treatment; however, fully achieving the goal of surgery has been uncommon. The goal of surgery is 'maximal safe resection' with the accepted target for maximal being complete resection of the contrast-enhancing tumor. This ideal result was obtained in less than 30% of cases in centers of excellence until a few years ago.

Fluorescence guided surgery (FGS) is a technique used to enhance visualization of tumor margins in order to increase the extent of resection in glioma surgery.

The role of glioma surgery has been debated for decades, as sceptics questioned the rationale of surgery for such an infiltrative disease. However, modern guidelines recommend primary surgical removal for all types of gliomas provided that neurological function is preserved and the tumour appears locally circumscribed on magnetic resonance imaging (MRI).

The benefits of a larger resection, however, must be weighed against the cost of deficits incurred in areas of eloquent cortex, particularly in motor and language areas 2).

Identification of the resection border for gliomas depends on the surgeon's interpretation of visual inspection and touch sensation, and such information depends on the tumor characteristics. One critical factor is the sharpness of the tumor borders as defined on T2-weighted MR images 3).

Because there is a high degree of individual variability in these areas, presurgical localization and intraoperative cortical mapping are often required to optimize the clinical outcome.

White matter tractography is limited by biological variables such as edema, mass effect, and tract infiltration or selection biases related to region of interest or fractional anisotropy values.

An automated tract identification paradigm was developed and evaluated for glioma surgery. A fiber bundle atlas was generated from 6 healthy participants. Fibers of a test set (including 3 healthy participants and 10 patients with brain tumors) were clustered adaptively with this atlas. Reliability of the identified tracts in both groups was assessed by comparison with 2 experts with the Cohen κ used to quantify concurrence. They evaluated 6 major fiber bundles: cingulum bundle, fornix, uncinate fasciculus, arcuate fasciculus, inferior frontooccipital fascicle, and inferior longitudinal fasciculus, the last 3 tracts mediating language function.

The automated paradigm demonstrated a reliable and practical method to identify white mater tracts, despite mass effect, edema, and tract infiltration. When the tumor demonstrated significant mass effect or shift, the automated approach was useful for providing an initialization to guide the expert with identification of the specific tract of interest.

Tunç et al., report a reliable paradigm for the automated identification of white matter pathways in patients with gliomas. This approach should enhance the neurosurgical objective of maximal safe resections 4).

Functional magnetic resonance imaging (fMRI) has played an important role in the preoperative assessment of patients with lesions adjacent to eloquent cortex.

Glioma is resistant to the apoptotic effects of chemotherapy and the mechanism underlying its chemoresistance is not currently understood.

Satoer et al. systematically searched the electronical databases Embase, Medline OvidSP, Web of Science, PsychINFO OvidSP, PubMed, Cochrane, Google Scholar, Scirius and Proquest aimed at cognitive performance in glioma patients preoperatively and postoperatively.

They included 17 studies with tests assessing the cognitive domains: language, memory, attention, executive functions and/or visuospatial abilities. Language was the domain most frequently examined. Immediately postoperatively, all studies except one, found deterioration in one or more cognitive domains. In the longer term (3-6/6-12 months postoperatively), the following tests showed both recovery and deterioration compared with the preoperative level: naming and verbal fluency (language), verbal word learning (memory) and Trailmaking B (executive functions).

Cognitive recovery to the preoperative level after surgery is possible to a certain extent; however, the results are too arbitrary to draw definite conclusions and not all studies investigated all cognitive domains. More studies with longer postoperative follow-up with tests for cognitive change are necessary for a better understanding of the conclusive effects of glioma surgery on cognition 5).

Intraoperative direct electrocortical stimulation for glioma surgery

Awake surgery for glioma

Azad TD, Duffau H. Limitations of functional neuroimaging for patient selection and surgical planning in glioma surgery. Neurosurg Focus. 2020 Feb 1;48(2):E12. doi: 10.3171/2019.11.FOCUS19769. PubMed PMID: 32006948.
Sanai N, Mirzadeh Z, Berger MS. Functional outcome after language mapping for glioma resection. N Engl J Med. 2008;358(1):18-27.
Hentschel SJ, Lang FF: Surgical resection of intrinsic insular tumors. Neurosurgery 57:1 Suppl176–183, 2005
Tunç B, Ingalhalikar M, Parker D, Lecoeur J, Singh N, Wolf RL, Macyszyn L, Brem S, Verma R. Individualized Map of White Matter Pathways: Connectivity-Based Paradigm for Neurosurgical Planning. Neurosurgery. 2016 Oct;79(4):568-77. doi: 10.1227/NEU.0000000000001183. PubMed PMID: 26678299; PubMed Central PMCID: PMC4911597.
Satoer D, Visch-Brink E, Dirven C, Vincent A. Glioma surgery in eloquent areas: can we preserve cognition? Acta Neurochir (Wien). 2016 Jan;158(1):35-50. doi: 10.1007/s00701-015-2601-7. Epub 2015 Nov 14. PubMed PMID: 26566782; PubMed Central PMCID: PMC4684586.
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