Prognostic value of multimodal evoked potentials in patients in a persistent vegetative state

Background. Numerous studies have demonstrated the usefulness of neurophysiological investigations with somatosensorial, brainsteim auditory and visual evoked potentials (SEPs, BAEPs, VEPs) for completing the clinical examination and evaluation of coma patients. Recently, new noninvasive techniques for transcranial stimulation of the motor cortex have been utilised with electrical or magnetic stimulation, which allow the recording of motor evoked potentials (MEPs) in the corresponding muscles of the stimulated area. This provides information on the integrity of the cortico- spinal motor pathways. Few neurophysiological studies have been carried out in patients in a persistent vegetative state (PVS). Methods. A perspective neurophysiological study was performed in 8 patients in a persistent vegetative state (PVS). The clinical pattern was evaluated using the Glasgow Outcome Scale at 4, 7 and 10 months after the pathological event. Neurophysiological investigations including brainstem auditory evoked potentials (BAEPs), median nerve somatosensory evoked potentials (MNSEPs) and motor evoked potentials (MEPs) were carried out at 4 months, with follow-up at 7 months. Results. At the first assessment and follow-up, BAEPs were normal in all but one of the patients (monolateral absence of all waves due to a peripheral lesion). SEPs were normal in only 1 patient in whom the clinical situation evolved to severe disability; in the remaining patients SEPs revealed different degrees of alteration. At follow-up, SEP recordings had improved in 3 patients: 2 evolved to severe disability and 1 to moderate disability. Conclusions. Our study suggests that SEPs could have a prognostic value for the clinical evolution of patients in a PVS.