Brain stem implants are used to improve hearing in patients with neural hearing loss. This loss is mostly caused by cancer of the auditory (hearing) nerve or an auditory nerve which failed to develop properly. These brain stem implants then convert sound into electrical impulses which stimulate the brain directly, bypassing the auditory nerve. An auditory brain stem implant inserted surgically and works in that way that it stimulates the brain stem of the recipient. There are not many people in the world who have done this surgery, around a thousand five hundred people in total, because it is a surgery and even more it is a brain surgery which can always be risky. In the beginning this surgery was only approved for people above 18 years old in the United States, in January 2013 a trial was approved for children as well. In Europe these surgeries were done with both children and adults. The auditory brain stem implants were developed originally in the House Ear Institute in 1979. The brain stem implant is consisted of two parts: an external part and the surgically implanted part. An auditory brainstem implant has two parts: an external part (the ‘processor’, worn on the ear) and the surgically implanted internal part. A microphone on the processor picks up the sound around it, and turns it from a sound wave into an electrical signal. The processor then transmits the sound signal to the internal part of the hearing implant. This consists of a receiver just below the skin, together with the implant array which is positioned within the brain stem.