The Use of Event-Related Potentials for Predicting the Degree of Mental Recovery in Patients with Severe Brain Injury – A Prospective Study

Gradual recovery from a prolonged coma through vegetative state and different types of mutism are detected in one-third of patients with a severe brain injury. Event-related potentials (ERPs) could be used as correlates of mental functions.

Aims: We focused on the correlation between ERP within first three months after severe traumatic brain injury (sTBI) and the degree of mental recovery one year, and several years later (up to 15 years after sTBI).

Place and Duration of Study: Burdenko National Medical Research Center of Neurosurgery, Moscow, Russia. Between 2000 and 2015.

Methodology: Dynamic examinations were carried out in 22 patients (53 studies) with sTBI followed up by a prolonged coma. During the first ERP session, patients were in a vegetative state, mutism, or had an unstable contact with the environment. The follow-up was up to 15 years after sTBI.

ERPs were recorded with and without the instruction to count target tones regardless of conscious recovery or the presence/absence of verbal contact with a patient. The amplitude and latency of components N100, N200 and P300, recorded in reply to both deviant and standard tones, were calculated. The topography of P300 was analysed.

Results: The connection between P300 lateralisation in the vegetative state and the outcome was revealed. Mere eliciting P300 recorded without instruction was considered to be a favourable prognostic factor. Although the full deficiency of P300 was unfavourable, it was not a rigorous criterion, as one-third of patients without P300 had mental recovery up to clear consciousness.

Conclusion: It can be concluded from the study that the analysis of N100, N200, P300 amplitude/latency and P300 topography recorded with and without instruction could be used for predicting mental recovery in patients in a vegetative state and mutism after sTBI.