Surgical treatment of gliomas in motor zone under control of neurophysiological monitoring
Authors: Dimertsev A. V. , Zuev A. A. , Podgurskaya M. G. 
Published: April 2023

Background. Primary tumors of central nervous system account for about 2 % of all human tumors. Generally, the tumor removal is a necessary treatment step. The main goal of the intracerebral tumors surgical treatment is the formation removal in the most radical physiologically possible way, because this directly affects the patients’ life length and its quality.

Aim. To assess the results of surgical treatment of motor zone tumors and identify predictors of development of irreversible motor disorders.

Materials and methods. A retrospective analysis of results of surgical treatment from 105 patients with tumors that affect corticospinal tract and primary motor cortex of the brain or localized in close proximity to those areas (up to 10 mm). All patients were treated in the neurosurgical department of N.I. Pirogov National Medical and Surgical Center, Ministry of Health of Russia (Moscow) in the period from 2014 to 2020. There were 48 (46 %) men, 57 (54 %) women aged from 22 to 79 (mean age 47.6 ± 14.5) years. Tumors volume before surgery ranged from 5.16 to 283.3 (mean volume 80.9 ± 55.1) cm3. The tumors’ size and their relationship with the surrounding structures were assessed by pre‑surgery magnetic resonance imaging and magnetic resonance tractography. For the intraoperative assessment of motor zone state dynamics, the transcranial electrical stimulation (n = 105, 100 %) and direct transcortical stimulation (with the eight‑contact electrode stripe) (n = 68, 64.8 %) of the primary motor cortex were used. To assess the proximity of the motor zones, a straight cortical and subcortical bi‑ or monopolar electrical stimulation was used (n = 105, 100 %).

Results. Sixty‑seven tumors (63.8 %) were removed completely, close to total removal was in 22 (20.9 %) tumors, 11 (10.5 %) tumors removal was subtotal and 5 (4.8 %) tumors were removed partially. Tumor volume after surgery ranged from 0 to 84.4 (mean volume – 3.54 ± 5.01) cm3, Development of novel motor deficiency or increase in pre‑surgery motor deficiency was observed in 46 (43.8 %) patients 24 hours after surgery and in 32 (30.5 %) of them 7 days after the treatment. However, during course of conservative therapy, the majority of patients showed regress of motor deficit and it remained only in 12 (11.4 %) patients on examination that was performed 6 months after surgery. Assessment of factors affecting development of persistent motor deficiency revealed its statistically significant association with intraoperative response decrease according to transcranial stimulation (p < 0.001) and transcortical stimulation (p < 0.001) data. There were no significant changes in the functional status of patients during postoperative period depending on strength of the direct stimulation when the resection was stopped (р = 0.9) or depending on radicality of tumor removal (p = 0.393).

Conclusion.

Removal of tumors of motor cortex and corticospinal tract using the multimodal neurophysiological mapping allows to achieve maximal resection of the tumor tissue with good functional outcomes. All of the above leads to significant improvement of patients’ life quality and allows further chemoradiotherapy.

Combined use of 4 methods of the neurophysiological mapping (transcranial, transcortical, direct cortical ang sub‑cortical stimulation) helps to minim ize the disadvantages of each of the methods and achieve radicality of the motor zone tumor removal with maintai ning their functional status.

Motor deficiency in patients increases after removal of motor zone tumors and then gradually restores to the original level or is improved 6 months after surgery.

A predictor of development of persistent motor deficiency is decrease in amplitude of motor evoked potentials by 50 % or more from baseline (according to transcranial and transcortical neurophysiological stimulation data).

When the motor evoked potentials in response to 1 mA direct monopolar neurostimulation are preserved then resection of the tumor is not a predictor of irreversible motor disorders during postoperative period.