Potential differences between monolingual and bilingual patients in approach and outcome after awake brain surgery

Abstract

Introduction: 20.8% of the United States population and 67% of the European population speak two or more languages. Intraoperative different languages, mapping, and localization are crucial. This investigation aims to address three questions between BL and ML patients: (1) Are there differences in complications (i.e. seizures) and DECS techniques during intra-operative brain mapping? (2) Is EOR different? and (3) Are there differences in the recovery pattern post-surgery?

Methods: Data from 56 patients that underwent left-sided awake craniotomy for tumors infiltrating possible dominant hemisphere language areas from September 2016 to June 2019 were identified and analyzed in this study; 14 BL and 42 ML control patients. Patient demographics, education level, and the age of language acquisition were documented and evaluated. fMRI was performed on all participants.

Results: 0 (0%) BL and 3 (7%) ML experienced intraoperative seizures (P = 0.73). BL patients received a higher direct DECS current in comparison to the ML patients (average = 4.7, 3.8, respectively, P = 0.03). The extent of resection was higher in ML patients in comparison to the BL patients (80.9 vs. 64.8, respectively, P = 0.04). The post-operative KPS scores were higher in BL patients in comparison to ML patients (84.3, 77.4, respectively, P = 0.03). BL showed lower drop in post-operative KPS in comparison to ML patients (- 4.3, - 8.7, respectively, P = 0.03).

Conclusion: We show that BL patients have a lower incidence of intra-operative seizures, lower EOR, higher post-operative KPS and tolerate higher DECS current, in comparison to ML patients.

Keywords: Bilingual patients; Direct cortical stimulation; Electrocorticography; Extent of resection; Intraoperative speech mapping; Language cortex.

Figure 1:

A 3D reconstruction of a brain image highlighting variation in language localization and lateralization derived from fMRI and intraoperative direct cortical stimulation in three patients. A) Sagittal brain illustration showing the native and the secondary language for three patients. Patient#1 showed a unilateral cortical representation of both English (Native), and Latvian (Secondary) languages, and was represented by light blue and blue color, respectively. Patient#2 showed a unilateral cortical representation of both Spanish (Native), and English (Secondary) languages, and was represented by light green and green color, respectively. Patient#3 showed a bilateral cortical representation of Spanish (Native), while unilateral cortical representation of English (Secondary) language, and was represented by light red and red color, respectively. B) Axial brain illustration showing the unilateral and bilateral cortical language representation.

Figure 2:

Reconstructive functional MRI (fMRI) results from a word-generation task in a bilingual patient with a WHO Grade III astrocytoma of the left frontoparietal operculum. A) The results for the patient’s native language is shown in blue and secondary language in orange. The native language shows an expected pattern of language activation in the left hemisphere, including both frontal and posterior language areas. B) fMRI representation of the secondary language in the right hemisphere. Non-contrast enhancing T1-weighted imaging showing the tumor in C) Left-sided sagittal cut and D) Axial cut on the left hemisphere.

Figure 3:

A) Intra-operative surgical field photograph showing the circular grid over the brain surface. B) Direct cortical stimulation using Ojemann stimulator with showing after-discharge on the electrocorticography (ECoG) monitoring using the circular grid. C) Intra-operative photograph showing the stickers identifying the eloquent cortical and subcortical areas: mouth motor, Broca’s, IFOF (inferior fronto-occipital fasciculus), and SLF (superior longitudinal fasciculus). D) Showing intra-operative neuropsychology language testing in both languages for bilingual patients.