Mapping of cortical speech zones and arcuate tract in patients with gliomas of temporal lobe of left hemisphere (analysis of a series of 27 observations)
Authors: Zhukov V. Yu. , Goryainov S. A. , Buklina S. B. , Afandiev R. , Vologdina Ya.  O. , Maryashev S. A. , Ogurtsova A. A. , Kobyakov G.  L. 
Published: April 2023

Introduction. Craniotomy in conscious patients is a possible tool for optimizing of tumor resection degree (Extent of Resection) while maintaining the quality of life. Traditionally, the main focus during these operations is on the cortical speech areas. At the same time, there is a shortage of studies on mapping of long associative tracts during the removal of gliomas of dominant speech hemisphere.

Aim. To analyze the data of intraoperative mapping and the postoperative state of speech function in patients with temporal lobe gliomas of left hemisphere (including those involving arcuate bundle) operated by the use of method of craniotomy in consciousness.

Materials and methods. Gliomas of temporal lobe of left hemisphere were removed in 27 patients aged 14 to 67 years (median age 43 years). In 10 patients, the tumor was localized in middle parts of temporal lobe (at the level of middle and upper temporal gyri), in 9 patients – in posterior parts of temporal lobe and exited into the supramarginal zone, in 8 it spread partially from temporal lobe to insular area. Gliomas of high degree of malignancy were detected in 21 patients, 6 had tumors of low degree of malignancy. Surgical intervention was performed with intraoperative “awakening”. All patients underwent cortical electrophysiological stimulation in order to control localization of cortical speech zones, subcortical stimulation was performed in 21 cases to identify terminals of arcuate bundle. Speech disorders before and after surgery (on day 4–6) were evaluated by neuropsychologist using the method proposed by A. R. Luria, an automated test with the naming of pictures was additionally used intraoperatively. The average current strength of direct electrical stimulation was 3 (1.9–6.5) mA. In 12 cases, magnetic resonance (MR) tractography with construction of arcuate tract was performed before and after the surgery.

Results. Cortical temporal speech zones during intraoperative electrical stimulation were detected in 20 (74 %) of 27 patients. In 10 patients, the arcuate tract was mapped in form of appearance of mixed speech disorders in the depth of surgical wound. In 23 (85.2 %) of 27 patients in early postoperative period, an increase in speech disorders was noted of which 13 people had disorders of temporal type only and 10 people (surgery on deep posterior parts of temporal lobe) had a combination of temporal and frontal types of speech disorders (conduction aphasia). Postoperative MR‑tractography (performed in 12 patients) revealed direct intraoperative tract lesion in 5 cases and ischemia of the tract area passage in 2 cases. These 7 patients had combined speech disorders after surgery. Gross sensory aphasia after surgery was manifested in 4 patients, in 2 of them ischemia was revealed according to postoperative magnetic resonance imaging, and 2 more had hemorrhagic impregnation in the removed tumor bed.

Conclusion. When removing tumors of temporal lobe in “awakening” conditions it is necessary to map speech zones not only in the cortical, but also in the subcortical area with terminals of arcuate bundle. Mapping of speech zones in these different localizations makes it possible to identify fundamentally different speech disorders.