**2.1. Surgical techniques**

surgeries for every neurosurgeon. The history of glioma surgery changed during the past century following all technical progresses. One of the biggest technical improvements started with the discovery of nuclear magnetic resonance in the 1950s, now known as magnetic resonance imaging [3]. After MRI introduction, the concept of maximal MRI visible tumor resection started to be the standard approach to glioma surgery. Nevertheless, this concept had a significant rate of morbidity, and it stranded to be valid for decades. During the past 25 years, the concept of surgical removal of gliomas has changed from a maximally aggressive for high grade glioma to minimally invasive but maximally efficient resection. The concept for low grade glioma changed also from "watch and wait" to active surgical

In the course of years, *subtotal resection* (STR) and *gross total resection* (GTR) evolved to *supratotal resection,* which became the surgical option especially for low grade glioma in the eloquent area and younger patients. With supratotal resection, neurosurgeons are trying to utilize minimally invasive surgery for the preservation of life quality as much as possible, but resecting most of tumor tissue using brain monitoring techniques, intraoperative imaging, awake surgery options, etc. The overall survival period with this approach was extended. As the new surgical concept, supratotal resection, which is actually also aggressive but selective, controlled, and monitored approach, over the years confirmed the highest level of general development of glioma surgery. In this respect, supratotal resection is probably becoming the most important part of *state of the art* in glioma management generally, but we are waiting for the results of big clinical trials. When the tumor infiltrates eloquent brain areas the challenge is how much to resect in balance of maximal safe resection and possible neurological deficit or worsening of func-

In this review, we are going to discuss surgical options for glioma treatment and the impact

Gliomas represent 30% of all brain tumors and 80% of all malignant brain tumors [1]*.* The origin of gliomas are the transformed glioma cells of the central nervous system. Gliomas can be classified by cell type, localization, and grade. The grade classification is performed by

Grade III—malignant glioma: anaplastic astrocytoma, anaplastic oligodendroglioma;

Grade IV—glioblastoma multiforme (IDH wild type and mutant), diffuse midline glioma, H3

World Health Organization (WHO) in 2016 and widely used [2].

Grade II—diffuse astrocytoma, oligodendroglioma;

treatment [4].

150 Glioma - Contemporary Diagnostic and Therapeutic Approaches

tional status [4].

K27M-mutant.

of it on the patient's life.

**2. Different surgical options**

There are four grades of gliomas: Grade I—pilocytic astrocytoma;

In this review, we will present contemporary surgical techniques used in treatment of both glioma groups: LGG and HGG and the impact on patient's life. Surgery remains the core treatment for management of gliomas. Surgical resection of pathological tumor mass, almost nonfunctional brain region, is common, standard, and the oldest neurosurgical approach to contemporary neuro-oncology. Historically, glioma surgery was a controversial topic, but many recent studies have demonstrated the crucial place of glioma resection in the management of low and high grade gliomas [5]. Concerning glioma surgery, there are two big questions: what the actual impact of resection is on progression of glioma and what the functional risk of it is [6]. To improve the outcomes of these two questions in past decades, a huge improvement has been made in intraoperative techniques (neuronavigation, intraoperative MRI, intraoperative ultrasound, stimulation mapping techniques, and fluorescence-guided surgery; **Figure 1**) [7, 8]. These techniques were developed to maximize the resection of glioma and preserve or improve the quality of life [6, 7]. Before glioma surgery, the neurosurgeon must calculate all benefits and possible hazards which could influence on morbidity, mortality, and quality of the rest of life.

There are few surgical options based on glioma type:


**Figure 1.** Typical intraoperative arrangement of the patient who undergoes tumor resection and the neurosurgeon, in the early stage of glioma surgery, immediately before dural opening. Microscope is positioned close to the surgeon's left arm and neuronavigation tool is in front (picture on the left). After the opening of the dura, characteristic findings of differently colored glioma affecting the brain cortex are presented. Tumor tissue bulks over the dural edge; it is obviously white-grayish and much lighter, with strange pathological vascularization (picture on the right).

### *2.1.1. Glioma biopsy*

Glioma biopsy is the standard procedure for taking tissue samples of tumors with a minimally invasive approach. It consists of taking a sample of tissue through a minimum opening of the skull. Biopsy indications are tumors in difficultly accessible brain zones, multicenter lesions, and pathology where it is advisable to establish a pathohistological diagnosis, which will then determine further surgical or nonsurgical treatment (e.g., whether it is tumor glioma or lymphoma; the former will then undergo resection, while the latter is mainly nonsurgically treated). On the other hand, very advanced gliomas and gliomas in the elderly who are not candidates for a more aggressive approach (open surgery) are also indications for biopsy. Minimally invasive approaches have been favored for a long time in neurosurgery for glioma resection.

field or coordinate systems relative to preoperative images and patients during surgery. To connect these two coordinate systems, "registration" is necessary to establish a common rela-

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The frameless system consists of two parts, an infrared scanner and a dynamic frame, that is fixed to the Mayfield holder. The dynamic scanner transmits the coordination system data to the operating field and integrates them with software with preoperative images. The dynamic framework requires at least three fixed registration points (nasion, lateral cannula, frontal tuber, and tragus). In the further course, an additional multipoint registration on the curvature of the skull is used for the purpose of co-registration and refining the matching of the two coordinating systems. Registration is performed by marker or laser. Once the registration has been made, it is necessary to carry out a check for early identification of errors. The advantages of the frameless system are ease of use, as well as intraoperative possibility, altering the route or plan without the need for additional CT scanning, not taking up a large space, the possibility of absolute freedom of manipulation of the operating field, and no preoperative

As the leading flaw of the frameless system, there is a decrease in precision compared to frame based, most likely because of less defined registration points in comparison to clearly defined points. However, these deviations from the target point in the brain do not exceed a value of 2–5 mm; they are expected and they are generally accepted when executing the

**a.** Neuronavigation driven resections, subtotal resections, and reduction of gliomas (determination of tumor margins, edges of craniotomy, as well as limitations of the form and

• patients with a high operative risk in case of prolonged anesthesia or those with

• patients with "unsafe" radiological diagnosis and suspicion of infectious or demyelinat-

planning and determination of the coordination point on CT or MRI.

Most important indications for neuronavigation in glioma surgery are:

advanced diseases and poor prognosis compared to co-morbidity

tionship between two coordinate systems [9].

procedure.

*2.1.1.3. Navigation-guided glioma biopsy*

**b.** Neuronavigational inducement of glioma biopsy

• deep lesions (thalamic gliomas, basal ganglia etc.)

• patients who reject the proposed surgery for resection

• early diagnosis with minimal risk

length of skin incisions)

• multiple lesions

ing disease
