Abstract
Traditionally, otolaryngologists have embraced new technology. In this era of rapid technology changes, it is important for us to be familiar with advances in various subspecialties. The field of otologic implants and procedures is in constant flux. New devices under investigational studies have resulted in various alternatives for specific indications.
The technology and philosophy of cochlear implant design are evolving rapidly. Advances are being made in the processor size and speed, durability, water resistance (Neptune; Advanced Bionics; Valencia, Calif.), an all-in-one unit (Rondo; MED-EL; Innsbruck, Austria), and especially in electrode design. The concept of modiolar hugging electrodes places the contacts of the electrodes closer to the eighth nerve and spiral ganglia. The cochlear implant manufacturers have current electrodes that are of smaller diameter and are less rigid. These are meant to follow the contour of the antimodiolar wall. Although they are of equivalent or longer length than the standard electrodes, they travel a greater span of distance since their position is on the outside wall of the scala tympani. They do not necessarily go farther into the cochlea. This should minimize trauma to the basilar membrane and will help maintain residual hearing if the implant is inserted in an atraumatic fashion. This has promising implications for future processor designs that will combine electrical and auditory stimulation.
Bone-conducting hearing devices are approved for both single-sided deafness and conductive hearing loss. Patients with mixed loss are also candidates, since the magnitude of the stimulus is sufficient to drive the ipsilateral cochlea. Patients with bone-conduction loss of up to 55 dB may be helped with the Baha (Cochlear Corp.; Sydney, Australia) and Ponto system (Oticon Medical AB; Askim, Sweden). This expands the indications for patients with otorrhea from a chronic ear cavity who cannot tolerate a conventional hearing aid.
Although bone-anchored devices are usually well tolerated, the skin around the abutment of the device can develop local wound problems, such as granulation tissue and focal infection. Hypertrophic scar formation may result in skin growth over the abutment, causing pain and inability to attach the processor. Abutments are available that are longer and/or have a coating of hydroxyapatite, offering the potential for less skin interaction. This also allows placement in thick skin and does not require as much tissue debridement. These can be changed in the clinic, although getting insurance coverage can be a hurdle.
Recent options are available for bone-conduction hearing that do not have a percutaneous post implanted through the skin. The SoundBite system (Sonitus Medical; San Mateo, Calif.) affixes a removable bone-stimulating intraoral device to the molar teeth, often on the side contralateral to the ear with single-sided deafness. The small microphone and FM transmitting unit is worn on the anacoustic ear and transmits the signal to the intraoral device, providing bone conduction to the good ear. The SoundBite system received FDA clearance in July 2011.
A bone-conduction design, the Alpha 2 (Sophono, Inc.; Boulder, Colo.), has an internal plate containing two magnets that are attached directly to the mastoid under the skin. This device does not entail a percutaneous abutment. Once the skin incision has healed (approximately 1 month), an external amplifier is attached that sends its vibratory signal across the skin through a transcutaneous connection by magnetic attraction. This is approved for adults and children above 5 years of age. They can have single-sided deafness if the contralateral good ear has thresholds of less than 20 dB. As with the percutaneous devices, the patients can also have conductive or mixed losses up to 45 dB. In April 2013, the FDA cleared this device to be safe for use in a patient undergoing magnetic resonance imaging despite its having internal magnets.
Another percutaneous device called the Baha 4 Attract System (Cochlear Corp.; Sydney, Australia) received FDA clearance in December 2013. This system involves a magnetic plate attached to the bone by a fixture screw and spreads the contact surface over a greater area.
Because the Alpha 2, SoundBite, and Baha 4 Attract systems were released by the FDA so recently, long-term success and rates of complications remain to be seen. Nevertheless, the advantage of not having an implant protruding through the skin provides patients and physicians with alternatives in worn or implantable hearing devices.
Modification is the mainstay of progress and product development. Progress in technology facilitates progress in patient care. It is incumbent upon all of us to maintain familiarity with current advances in technology so that we can provide our patients with state-of-the-art care.