Results of SRA Nucleus Freedom CI in population of children with functional residual hearing

Introduction and objectives Hearing impairment is a condition, which especially severely affects children, having an extremely intense impact on the child’s development. Development of spoken language, which is one of modes of representation of the external world and also the basis for common social communication, will not be started without delivery of auditory input. The condition of limited auditory delivery, such as profound hearing impairment affecting only some frequencies, does not constitute an appropriate ground for language development. A complex acoustic environment is an especially challenging auditory situation for these children, and so natural everyday circumstances, like noisy school classrooms and crowded rooms become just too difficult for them (Hogan and Turner, 1998). This makes for poor integration with their peers and progressive isolation of hard of hearing children. Lack of the acoustic energy provided to spiral ganglion cells and then to the upper auditory pathways by means of acoustic enhancement has considerable consequences, and so many hard of hearing children, even though bilaterally aided since early childhood, present with no or very poor gain from acoustic stimulation. Also in cases when amplification was sufficient in early years, if there is deterioration of hearing the benefit from these decreases, even when using high powered hearing devices (Hogan and Turner, 1998). In this situation, the auditory cortex lacks the auditory stimulation required and the development of language slows up in comparison with the child’s normal hearing peers or may stop altogether. With growing experience in cochlear implantation and also development of new techniques, new indications for this procedure have appeared. The biggest group constitutes patients with considerable residual hearing, who are just outside the qualification criteria for acoustic amplification but who receive severely limited benefit from their hearing. The condition of profound sensory-neural hearing loss in the high and mid frequencies and preserved normal or near normal hearing in low frequencies has been named partial deafness by the first author of this paper (Skarzynski et al., 2010). The surgical technique of cochlear implantation in a partially working cochlea, with functional hearing in low frequencies, brings the challenge of preserving this function so that it remains usable either for natural hearing or acoustic amplification. Function preservation is equivalent to structure preservation in the cochlea. For this reason, changes were introduced to the technical parameters of the cochlear implant electrode arrays. The new array, Straight Research Array (SRA), has been designed as thinner and much more flexible compared to current standard arrays. Also, the surgical technique itself has evolved, according to the principles of organ preservation surgery, into ‘soft surgery’ cochlear implantation with its crucial round window approach to the cochlea. (Skarzynski et al., 2007a, 2007b) The round window membrane is the most physiological approach to the scala tympani, giving a surgeon the feeling of following the natural anatomy. The introduction of a soft array into the basal turn through the round window allows the surgeon to introduce the array into the basal turn perpendicular to the round window membrane and so avoids hitting the modiolus. Reduction of trauma when using a round window approach is believed to allow for successful hearing preservation surgery. The Skarzynski six-step surgical procedure for treatment of partial deafness was proposed as a treatment of choice (Skarzynski et al., 2010). Step 1: automastoidectomy; step 2: posterior tympanotomy to allow visualization of the round window niche; step 3: puncture and incision of the round window membrane; step 4: approach to the scala tympani directly through the round window membrane (partial insertion of electrode array); step 5: electrode fixation at the round window membrane