[Surgical treatment of eloquent brain area tumors using neurophysiological mapping of the speech and motor areas and conduction tracts]

Application value of intraoperative electrophysiological monitoring in cerebral eloquent area glioma surgery: a retrospective cohort study

INTRODUCTION

Surgery for gliomas involving eloquent areas is a very challenging microsurgical procedure. Maximizing both the extent of resection (EOR) and preservation of neurological function have always been the focus of attention. Intraoperative neurophysiological monitoring (IONM) is widely used in this kind of surgery. The purpose of this study was to evaluate the efficacy of IONM in eloquent area glioma surgery.

METHODS

Sixty-eight glioma patients who underwent surgical treatment from 2014 to 2019 were included in this retrospective cohort study, which focused on eloquent areas. Clinical indicators and IONM data were analysed preoperatively, two weeks after surgery, and at the final follow-up. Logistic regression, Cox regression, and Kaplan‒Meier analyses were performed, and nomograms were then established for predicting prognosis. The diagnostic value of the IONM indicator was evaluated by the receiver operating characteristic (ROC) curve.

RESULTS

IONM had no effect on the postoperative outcomes, including EOR, intraoperative bleeding volume, duration of surgery, length of hospital stay, and neurological function status. However, at the three-month follow-up, the percentage of patients who had deteriorated function in the monitored group was significantly lower than that in the unmonitored group (23.3% vs. 52.6%; P < 0.05). Logistic regression analysis showed that IONM was a significant factor in long-term neurological function (OR = 0.23, 95% CI (0.07-0.70). In the survival analysis, long-term neurological deterioration indicated worsened overall survival (OS) and progression-free survival (PFS). A prognostic nomogram was established through Cox regression model analysis, which could predict the probability 3-year survival rate. The concordance index was 0.761 (95% CI 0.734-0.788). The sensitivity and specificity of IONM evoked potential (SSEP and TCeMEP) were 0.875 and 0.909, respectively. In the ROC curve analysis, the area under the curve (AUC) for the SSEP and TCeMEP curves was 0.892 (P < 0.05).

CONCLUSIONS

The application of IONM could improve long-term neurological function, which is closely related to prognosis and can be used as an independent prognostic factor. IONM is practical and widely available for predicting postoperative functional deficits in patients with eloquent area glioma.

[Mapping the musician brain during awake craniotomy]

Direct cortical stimulation during awake craniotomy with speech testing became the «gold standard» in brain mapping and preserving speech zones during neurosurgical procedures. However, there are many other cerebral functions, and their loss can be very critical for certain patients. For example, such a function is production and perception of music for musicians. This review presents the latest data on functional anatomy of musician brain, as well as aspects of neurosurgical treatment with awake craniotomy and music testing under brain mapping.

Surgical treatment of glial tumors of the paralimbic system

BACKGROUND

Tumors of the paralimbic system were considered inoperable for a long time due to high risk of postoperative complications. However, there have been significant changes in surgical tactics for these neoplasms over the past decades. Despite the improvement of surgical principles for these tumors and development of new approaches, risks of surgical treatment are still high (up to 33.6%).

OBJECTIVE

To assess the results of surgical treatment of paralimbic glial tumors and identify predictors of adverse outcomes.

MATERIAL AND METHODS

We retrospectively analyzed postoperative outcomes in 52 patients with paralimbic glial tumors at the neurosurgical department of the Pirogov National Medical Surgical Center between 2016 and 2020. Tumor dimensions and topography with surrounding structures were evaluated using preoperative MRI. Resection quality was evaluated within the first postoperative day considering MRI data. We applied transcranial or transcortical electrostimulation, direct cortical and subcortical bi- and monopolar stimulation for intraoperative functional assessment of corticospinal tract. Neurological examination was performed prior to surgery, after 24 hours, 7 days, and 6 months.

RESULTS

Total resection was performed in 39 patients, almost total - 5 patients, subtotal - 6 patients, partial resection - 2 patients. Mean volume of tumors before surgery was 95.1±55.1 cm³. After surgery, volume ranged from 0 to 24.7 cm³ (mean 2.2±5.01 cm³). After 24 hours, neurological symptoms de novo or aggravation of preoperative motor deficit was revealed in 17 (33%) patients. However, this impairment regressed in most patients, and only 4 (7%) patients retained these disorders after 6 months.

CONCLUSION

Transcortical or combined surgical approach in conjunction with multimodal neurophysiological monitoring allows total or close to total resection of paralimbic glioma in 85% of cases. Risk of postoperative complications is 7%. Unfavorable prognostic factors of neurological impairment are decrease in muscle response amplitude ≥50% according to transcranial neurophysiological stimulation and tumor spread medial to perforator arteries.

Clinical Pearls and Methods for Intraoperative Motor Mapping

Resection of brain tumors involving motor areas and pathways requires the identification and preservation of various cortical and subcortical structures involved in motor control at the time of the procedure, in order to maintain the patient's full motor capacities. The use of brain mapping techniques has now been integrated into clinical practice for many years, as they help the surgeon to identify the neural structures involved in motor functions. A common definition of motor function, as well as knowledge of its neural organization, has been continuously evolving, underlining the need for implementing intraoperative strategies at the time of the procedure. Similarly, mapping strategies have been subjected to continuous changes, enhancing the likelihood of preservation of full motor capacities. As a general rule, the motor mapping strategy should be as flexible as possible and adapted strictly to the individual patient and clinical context of the tumor. In this work, we present an overview of current knowledge of motor organization, indications for motor mapping, available motor mapping, and monitoring strategies, as well as their advantages and limitations. The use of motor mapping improves resection and outcomes in patients harboring tumors involving motor areas and pathways, and should be considered the gold standard in the resection of this type of tumor.