Auditory brainstem implant
An auditory brainstem implant (ABI) is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf, due to sensorineural hearing impairment (due to illness or injury damaging the cochlea or auditory nerve, and so precluding the use of a cochlear implant).
The auditory brain stem implant uses similar technology as the cochlear implant, but instead of electrical stimulation being used to stimulate the cochlea, it is instead used to stimulate the brain stem of the recipient.
Only about a thousand recipients have been implanted with an auditory brain stem implant, due to the nature of the surgery required to implant the device (as it requires brain surgery to implant the device) and the reduced effectiveness of the implant (most auditory brain stem implant recipients only have an awareness of sound - recipients won't be able to hear musical melodies, only the beat).
In the United States ABIs are only approved for adults (18 & over) and only for patients with neurofibromatosis type II (NF2). In Europe, ABIs have been used in children and adults, and in patients with NF2 as well as other auditory complications, such as auditory nerve aplasia and cochlea ossification. Speech perception in non-NF2 patients on average has been reported to be higher than that of NF2 patients.
Implant history 
The auditory brainstem was first implanted in humans in 1979 at the House Ear Institute, CA, USA. This original ABI consisted of two ball electrodes which were implanted near the surface of the cochlear nucleus. A change from a percutaneous connection to a wireless transcutaneous connection, and from ball electrodes to flat electrodes were the only changes to the implant until 1991, where 25 people had received the ABI.
In the US in 1992 an eight electrode implant developed by Cochlear Limited, the House Ear Institute and Huntington Medical Research Institute. An electrode array with 21 electrodes developed by Cochlear Limited was developed for the European market at the same time. The processor for both the eight and 20 electrode implants used Nucleus 22 ABI (Cochlear Limited) external speech processors. Since 1999 a 21 electrode array implant has been used with the Nucleus 24 ABI (Cochlear Limited) speech processor.
A 12 electrode array implant with a speech processor based on the C40+ cochlear implant (Med-El) and a 16 electrode array implant with the Clarion-1.2 cochlear implant (Advanced Bionics) have also been developed.
See also 
-  Reading Eagle, Feb 25, 1993
- Colletti et al. 2004, Auditory Brainstem Implant (ABI): New frontiers in adults and Children,Otolarangol head neck surg
- Colletti and Shannon 2005, Open Set Speech Perception with Auditory Brainstem Implant? The Larongoscope.
- Edgerton et al. 1982, Hearing by cochlear nucleus stimulation in humans, Ann Otol Rhinol
- House and Hitselberger 2001, Twenty year report of the first auditory brain stem nucleus implant, Ann Otol Rhinol Laryngol
- Brackmann et al. 1993, Auditory brainstem implant: I. Issues in surgical implantation, Otol Head Neck Surg
- Otto et al. 1998, The Multichannel Auditory Brainstem Implant: Performance in Twenty Patients, Otol Head Neck Surg
- Laszig et al. 1991, The Hanover Auditory Brainstem Implant: A Multiple-electrode prosthesis, European Arch Otol Rhinol Laryngol
- Jackson et al. 2002, An auditory Brainstem Implant System, Am J Audiol
- Lenarz et al. 2001, Auditory Brainstem Implant: Part 1. Performance and its Evolution Over Time, Otol Neurotol
Further reading 
- Colletti V, Fiorino F, Sacchetto L, Miorelli V, Carner M (Aug 2001). "Hearing habilitation with auditory brainstem implantation in two children with cochlear nerve aplasia". Int J Pediatr Otorhinolaryngol 60 (2): 99–111. doi:10.1016/S0165-5876(01)00465-7. ISSN 0165-5876. PMID 11518586.
- Davis NL, Rappaport JM, MacDougall JC (Fall/Winter 1997). "Cochlear and Auditory Brainstem Implants in the Management of Acoustic Neuroma and Bilateral Acoustic Neurofibromatosis". McGill Journal of Medicine (3): 115–120.
- Elvsåshagen T, Solyga V, Bakke SJ, Heiberg A, Kerty E (Aug 2009). "Neurofibromatosis type 2 and auditory brainstem implantation". Tidsskr Nor Laegeforen 129 (15): 1469–1473. PMID 19690597.
- Kanowitz SJ, Shapiro WH, Golfinos JG, Cohen NL, Roland JT Jr (Dec 2004). "Auditory brainstem implantation in patients with neurofibromatosis type 2". Laryngoscope 114 (12): 2135–2146. PMID 15564834.
- Møller AR (2006). "History of Cochlear Implants and Auditory Brainstem Implants". Adv Otorhinolaryngol. 64: 1–10. PMID 16891833.