Electrocorticography in patients with severe traumatic brain injury
Introduction. The frequency of adverse outcomes in patients with severe traumatic brain injury (TBI) exceeds 25%. Epileptic seizures and vasospasm, in the absence of pathogenetic treatment, cause irreversible brain damage and thus complicate the course of severe TBI. Bedside electroencephalography (EEG) is traditionally used to diagnose these conditions. However, its low spatial resolution when recording from the scalp and a large number of artefacts that make it challenging to analyse the data. Materials and methods. Electrocorticography (ECoG) monitoring was performed using subdural electrodes implanted in the traumatic brain lesion during TBI surgery in 11 patients during the acute period of severe TBI. All patients were concurrently monitored using scalp EEG with subdermal needle electrodes. Results. Analysis of scalp recordings showed frequency disturbances and oscillation asymmetry in all patients, while sporadic epileptiform activity and rhythmic and periodic patterns were detected in 18% and 64% of subjects, respectively. Analysis of invasive EEG showed sporadic epileptiform activity in 27% of patients, while rhythmic and periodic patterns were present in 91%. Moreover, epileptiform activity was registered only by the subdural leads in 3 patients. The total percentage of subjects in whom we registered clinical and electrographic signs of convulsive and nonconvulsive status epilepticus using EEG and ECoG was 55%. We found indirect EEG signs of slowspreading cortical depolarization in one patient whose level of consciousness was coma, followed by an electrographic pattern of status epilepticus on ECoG. Conclusion. ECoG recording, while patients with severe TBI are in the intensive care unit, increases the diagnostic capabilities of this method, allowing electrographic seizures to be recorded more often and more accurately, but also to detect indirect signs of slowspreading cortical depolarization using standard EEG amplifiers. Electrode implantation during TBI surgery is safe and does not significantly change the surgical approach.