Dominated EEG patterns and their prognostic value in coma caused by traumatic brain injury.

Study aimed at investigation of dominated EEG patterns in traumatic coma of different severity and to elucidate their prognostic value for outcome of disease within month. A total of 53 coma patients with severe traumatic brain injury have been investigated. Exclusion criteria comprised the patients needing the neurosurgical intervention due to hemorrhage. Brain injury was visualized by conventional CT at admission. The level of consciousness was evaluated by Glasgow Coma Scale (GCS). Patients were divided in 5 groups according to GCS. Electrophysiological investigations were performed on 5th day from development of coma by application of 16 channel computer encephalography. Outcome of coma (death, vegetative state, recovery) was evaluated within month from disease onset. According to dominated EEG background activity patterns the 1st group (GCS=4) showed the delta EEG pattern in 50 % of patients, the beta EEG pattern- in 33.4% and the alpha EEG pattern - in 16.6%. The 2nd group (GCS=5) revealed the delta EEG in 40%, the beta EEG- in 6.7% and the theta EEG - in 53.3%. The 3rd group (GCS=6) showed the delta EEG pattern in 27.8% and the theta EEG pattern- in 72.2%. In 4th group (GCS=7) the theta EEG pattern found in 77.7% and the beta EEG pattern in 22.3%. The 5th group (GCS=8) revealed the theta EEG activity in 80% and beta EEG activity - in 20%. Positive correlation was found between the GCS and the frequency of theta EEG pattern (r=+0.62; p<0.05). Positive correlation was established between the frequency of delta EEG pattern, death and persistent vegetative state (r=+0.57 and r=+0.16 respectively, p<0.05) within month. Positive correlation was established between the frequency of delta EEG pattern and the size of brain injury (r=+0.3; p=0.04). Multinomial logistic regression revealed the significance of brain lesion size, GCS and EEG pattern for functional outcome of coma. In severe traumatic coma patients the delta EEG pattern is associating with deep coma state and predicts the poor functional outcome within month.