Slow-wave EEG activity is related to language functioning in glioma patients

Background: Patients with a glioma in eloquent brain areas frequently suffer from language problems, before and after surgery. How these difficulties relate to their functional brain organisation can be studied with electroencephalography (EEG). Gliomas cause increased brain activity in lower frequency bands (0.5-8 Hz; slow-wave activity), which is correlated with cognitive dysfunction. However, relationship of this activity to language has not been investigated. We examined whether slow-wave activity is related to language functioning in glioma patients.
Method: Twenty-one presumed low-grade glioma patients, who underwent surgery, were retrospectively included. They had available language and EEG data, obtained within one year preoperatively or postoperatively. Mean composite language z-scores were calculated, consisting of object naming, verbal fluency, comprehension, repetition, reading and/or writing scores. EEG recordings were analysed visually by categorising slow-wave activity, and quantitatively by calculating relative slow-wave power during wakeful, resting conditions.
Results: Visual EEG analysis showed that patients with moderate/severe slow-wave activity had lower language scores than patients with normal/mild slow-wave activity. Quantitative EEG analysis revealed a significant negative correlation between slow-wave power and language scores.
Conclusion: We demonstrate that slow-wave activity in resting-state EEG is related to language functioning in glioma patients. Limited slow-wave activity is associated with better language performance and increased slow-wave activity is associated with poorer language performance. These findings contribute to knowledge of the underlying neural mechanisms of language problems. The potential use of slow-wave activity for predicting language outcome after surgery remains to be investigated, as it may have clinical applications for the perisurgical procedure.