Visual vs. quantitative electroencephalographic analysis in patients with and without posttraumatic epilepsy

We investigated traces of EEG records from two groups of patients with brain trauma: with and without posttraumatic epilepsy (PTE) with respect to the control group by means of two methods: visual and quantitative EEG (QEEG) analysis. The aim of this study was to compare these methods in their sensibility for traumatic and epileptic alterations of the brain tissue in the two experimental conditions: after hyperventilation (HV) and after photo stimulation (FS), and in regard to the basic condition. 36 patients with PTE and 33 without PTE, and the control group of 34 healthy subjects participated in this study. EEG was registered in three 1-min epochs: before activation, after HIV, and after FS on digital 32-channel EEG apparatus XLTEK. Mean amplitudes were calculated in 10 frequency ranges from 0 to 30 Hz on projections F7-C3, T5-O1, F8-C4 and T6-O2 from 16-s segments without artefacts. Data evaluation was performed using program package PERSYST Insight II (Persyst Development Co). Statistical package GRAPII-PAD was used for ANOVA test and Bonferroni post-test. Visual analysis used to distinguish between normal EEG, with pathological alterations, non-epileptiform and epileptiform transients showed that there was no statistically significant difference between patients with and without post-traumatic epilepsy. On the contrary, QEEG of registered epochs before activation, after HV and after FS showed statistically significant differences between the control group and the patients without PTE and with PTE. These results indicate that quantitative analysis provides more subtle data about el ectrophysiological alterations after traumatic brain injury, which leads to better classification of patients.