P06.07.A REVISING THE NARRATIVE OF THE RIGHT NON-DOMINANT HEMISPHERE: PATTERNS OF IMPAIRED COGNITION AND LANGUAGE IN RIGHT SIDED DIFFUSE LOW-GRADE GLIOMA.

Abstract BACKGROUND In neurosurgical treatment of diffuse low-grade glioma (DLGG), the right (non- dominant) hemisphere of the brain is commonly seen as less eloquent and therefore less susceptible to cognitive decline and emotional symptoms caused by tumor growth and treatment. Procedures to preserve cognitive function during surgery, e.g. awake brain mapping, are still more often planned for left hemisphere tumors although there is accumulating evidence of the important role of the right hemisphere for cognition and even language. The aim of this study was to compare the preoperative cognitive and emotional symptoms of patients with DLGG in the right non-dominant and the left dominant hemisphere. MATERIAL AND METHODS This was an observational Swedish cohort study from two neurosurgical centers. The same comprehensive battery of neuropsychological tests was completed by 169 patients with untreated DLGG WHO-grade 2 and 3 prior to surgical treatment. Mean test performances, percentage of patients with impairment and self-reported symptoms of depression and anxiety (Hospital Anxiety and Depression Scale) were analyzed in the patients with right-sided (RS) DLGG (N=81) and compared with those with left-sided (LS) DLGG (N=88). RESULTS There were no significant differences in test performance nor psychological symptoms between patients with RS and LS DLGG (Mann Whitney U-test, p<.05). The lowest mean scores were found in the language domain for tumors in both hemispheres (RS mean score z= -0.5, SD 1.31; LS mean score z -0.4, SD 1.20). Impairment (z= -1.5 SD or more) was most frequent in the domains of language (RS=23%, LS=13%), working memory (RS=20%, LS=26%) and verbal episodic memory (RS=14%, LS=7%). Patients overall reported more symptoms of anxiety (mean RS 7.7, SD 4.27; LS 8.1, SD 4.52) than of depression (mean RS 4.7, SD 3.58; LS 3.9, SD 3.27) independently of the tumor’s side. CONCLUSION Both dominant and non-dominant sided DLGG displayed the same frequency and pattern of cognitive impairment and emotional symptoms prior to surgery. This supports the importance of cognitive assessment and intraoperative mapping also in patients with tumors in the non-dominant hemisphere. Further studies are needed to explore the long-term effects of tumor laterality on cognition and treatment outcome.