Due to continuous improvements in acute medical care, the number of patients surviving severe brain damage has increased over the past decades. While some patients improve significantly during the first days after the injury, other patients remain in altered states of consciousness (i.e. coma, unresponsive wakefulness syndrome or minimally conscious state). In patients with disorders of consciousness (DOC), the auditory modality is preferably examined because the responsiveness within the motor and visual modality is often difficult to assess or impaired. Music is a special type of auditory stimulation that can be of particular benefit in DOC patients. The positive effects of music are attributed to the restoration of specific brain networks that are necessary for processing sensory inputs, as well as the emotional aspects of music, which can increase arousal and activate the reward system. Previous studies have shown that music, including passive listening to music, is associated with psychological and physical changes in both healthy and clinical populations. For example, listening to preferred music can reduce pain and anxiety and the need for sedation in different patient groups.

Music therapy has a long tradition in neurological rehabilitation. In DOC patients, passive listening to music is used (in contrast to active therapies used in fully conscious patients). Efficacy results are inconsistent, however, since only a few studies have systematically investigated the effects of music therapy. In previous investigations, either the sample size is very small or no control conditions have been used. A study that met both quality criteria was published by Sun \& Chen in 2015. The authors compared two groups: while the music group (n = 20) listened to their favorite music for 15 to 30 minutes three times a day for a period of four weeks, the control group received no stimulation. Although the GCS values increased significantly in both groups, the music group showed a significantly stronger improvement in the level of consciousness. Based on this study, the present study wants to compare the effectiveness of passive listening to music with two control conditions (alternative auditory stimulation and no auditory stimulation) in early neurological rehabilitation patients.

It is a prospective, double-blind, controlled and randomized intervention study that is carried out monocentrically. Over a period of 24 months, 66 patients undergoing early neurological and neurosurgical rehabilitation after severe brain damage are included. For the individual patient, the study duration is a maximum of 38 days (preliminary phase: 3-7 days; intervention phase: 28 days; follow-up phase: 1-3 days). Patients are randomly assigned to one of three study arms (1. Musical stimulation; 2. Alternative auditory stimulation, 3. No auditory stimulation). In the preliminary phase (days 1 to 7), a native MRI (without contrast agent) and a CRS-R assessment are performed. In addition, there is a neurophysiological examination in which evoked potentials are recorded. In the subsequent main phase, the intervention takes place: Over a period of 28 days, the study participants wear headphones for 30 minutes a day, through which they are presented with preferred music (experimental arm), an audio book (comparative arm) or silence (control arm). In the main phase, a CRS-R test is carried out weekly to record the current state of consciousness. In the follow-up phase (1 to 3 days), the (native) MRI examination, the CRS-R assessment and the neurophysiological examination are repeated. The primary outcome measure is an improvement of the level of consciousness, measured with the Coma-Recovery-Scale-Revised (CRS-R).