[Computer assisted analysis of EEG, evoked potentials, EEG reactivity and heart rate variability in comatose...

A multifunctional system for combined evaluation of EEG, visual (VEP), somatosensory (SEP) and auditory brainstem evoked potentials (BAEP) is introduced. For the light stimulation an array of light emitting diodes are used for tactile stimulation a vibration stimulus is applied to he distal digit of one finger. Stimulus-synchronous EEG segments are used for EP averaging and also for quantification of either the blocking or the activation of rhythmic EEG activity. Using this technique, alpha spindles characteristic of certain comatose states can be quantified for the first time. An important parameter is the alpha frequency, which is slowed down when there is evidence of cortical lesions, but remains unchanged in primary brain stem lesions. Comparing SEP and VEP also allows for differentiation of brain stem lesions from lesions in other areas. VEP were found to be maintained in predominant brain stem disorders. The auditory brain stem potentials and the heart rate variability are of further diagnostic significance. The importance of the individual parameters such as alpha-frequency, VEP, SEP, BAEP and alpha-spindles is demonstrated by follow-up studies in comatose patients.