A hearing loss is condition which significantly affects the quality of life. The prevalence of the hearing disorders is relatively high due to many conditions which may result in a deafness. In those cases where hearing aids are not a sufficient solution to these difficulties, cochlear implantation is the standard treatment. It has been more than 30 years since the first implantation in the Czech Republic. These days it is common surgical procedure for adults and even children and it replaces, at least in part, the function of the hair cells that are no longer able to stimulate the primary auditory neurons.. Recent studies have reported that cochlear implant does not affect only hearing, but also other functions of the inner ear - the vestibular system resulting in stability and spatial orientation. Postural control is provided by coordination of movement strategies and sensory functions. If one ore more of these components are compromised postural instability appears. Instability is one of the most common causes of reduced quality of life. The deaf are characterized by their compensatory mechanisms, where visual system dominates over somatosensory and vestibular. After the cochlear implantation the postural behavior and compensations are changing apparently. The investigators assume that these mechanisms can be affected by vestibular rehabilitation. The purpose of this projet, will be to evaluate whether electrical stimulation of the eighth cranial nerve also affects vestibular functions and determine if the stimulaton changes postural stability and created compensations.