[Multimodal evoked potentials and heart rate variability in comatose patients. 2. Visual evoked potentials and...

Visual evoked potentials (VEPs) were examined as an integrated parameter in a multimodal EP study of brain bioelectrical activity in 33 comatose patients (Glasgow Coma Score 3-6) after craniocerebral trauma. Recordings were performed not only from the occipital (01-02) but also from the central (Cz-C3, Cz-A1, Cz-C4) and frontal (F3-F4) areas. The results show an attenuation of the vertex VEP (SNR 3.2 +/- 1.7) and an increase in the occipital VEP (SNR 4.8 +/- 2.3) as compared to the control group (SNR vertex 7.0 +/- 3.0/SNR occipital 3.9 +/- 2.0). In addition, 16 of the comatose patients showed a very considerable loss of the normally polyphasic character of the occipital VEP in favour of a potential that looked almost monophasic; this was either left or right dominant, and was recorded as a negative or positive potential, respectively, in bipolar recording (01-02). Comparison of the electrophysiological and computer tomography findings showed a laterally correlated change in the occipital VEP: contralateral to the injured hemisphere, the VEP was dominant, ipsilateral it was reduced or extinguished.