Speech and Language Errors during Awake Brain Surgery and Postoperative Language Outcome in Glioma Patients: A Systematic Review

SIMPLE SUMMARY: Many glioma patients suffer from postoperative language problems after awake brain surgery, which have a negative effect on their quality of life. We investigated which language-related factors before and during surgery predicted language problems after surgery (language outcome). We found that language problems before surgery and word-finding and production problems during surgery were predictors for the language outcome. After surgery, the language problems that occurred most often were production deficits and spontaneous speech deficits. In conclusion, during surgery, word-finding problems and production errors should carry particular weight during decision making concerning the optimal onco-functional balance for a given patient, and spontaneous speech should be monitored. These new insights should be investigated further and may facilitate decision-making during surgery in the future, which can improve the procedure. This may improve the language outcome and ultimately the quality of life in this patient group. ABSTRACT: Awake craniotomy with direct electrical stimulation (DES) is the standard treatment for patients with gliomas in eloquent areas. Even though language is monitored carefully during surgery, many patients suffer from postoperative aphasia, with negative effects on their quality of life. Some perioperative factors are reported to influence postoperative language outcome. However, the influence of different intraoperative speech and language errors on language outcome is not clear. Therefore, we investigate this relation. A systematic search was performed in which 81 studies were included, reporting speech and language errors during awake craniotomy with DES and postoperative language outcomes in adult glioma patients up until 6 July 2020. The frequencies of intraoperative errors and language status were calculated. Binary logistic regressions were performed. Preoperative language deficits were a significant predictor for postoperative acute (OR = 3.42, p < 0.001) and short-term (OR = 1.95, p = 0.007) language deficits. Intraoperative anomia (OR = 2.09, p = 0.015) and intraoperative production errors (e.g., dysarthria or stuttering; OR = 2.06, p = 0.016) were significant predictors for postoperative acute language deficits. Postoperatively, the language deficits that occurred most often were production deficits and spontaneous speech deficits. To conclude, during surgery, intraoperative anomia and production errors should carry particular weight during decision-making concerning the optimal onco-functional balance for a given patient, and spontaneous speech should be monitored. Further prognostic research could facilitate intraoperative decision-making, leading to fewer or less severe postoperative language deficits and improvement of quality of life.