Hearing loss is common among patients with acoustic neuromas. Severe hearing loss may present as a result of the tumor itself or its treatment. Patients with single-sided deafness can experience significant difficulty hearing in noisy environments and determining the direction in which sounds come from. At times, they may experience tinnitus, or ringing in the ears, which becomes a distraction to the normal hearing ear.
Treatments currently available to patients with single-sided deafness include CROS (contralateral routing of signal) and BiCROS hearing aids and bone anchored hearing aids. These devices are designed to capture sound from the side of the head with hearing loss and send it to the normal hearing side. These devices do not restore hearing, nor do they allow patients to determine where the sound is coming from. They do allow patients to overcome the “head shadow” effect, which requires them to constantly turn their heads towards the source of the sound.
CROS and BiCROS hearing aids involve the use of a hearing aid on the ear with normal hearing and a small microphone on the deaf ear. The microphone then sends the sounds (using radiowaves or Bluetooth) from the microphone to the hearing aid. This nonsurgical option can be easily fitted by an audiologist. The BiCROS hearing aids are particularly helpful for patients that have some degree of hearing loss on the better ear. BiCROS devices not only route the sounds from the microphone to the hearing aid, but they also amplify sounds to the ear experiencing a lesser degree of hearing loss.
Bone-anchored hearing aids function in a similar manner. These devices send sound waves through the bone of the skull from the side with hearing loss to the other side. These hearing aids function best if the hearing is normal on the non-deaf side. The patient undergoes a minor surgical procedure to implant a small metal device into the skull behind the ear. Some of these metal implants go through the skin and are visible. They are about the size of a metal snap button. Others are magnetic and are completely under the scalp. For both, an outer processor – similar in size to a small Bluetooth headpiece – is then attached to the metal device either directly or via a magnet. The processor captures the sounds and transmits it to the implant that then sends the sound through the bone to the other ear.
Cochlear implants are also available to treat deafness but are currently only FDA-approved for individuals with deafness in both ears. These devices, unlike hearing aids, restore hearing to the deaf ear. The quality of the sounds is very different than normal hearing and can vary from person to person, but they have been shown to be very beneficial in the treatment of hearing loss. Further research is underway at the Keck School of Medicine of USC to examine the benefit of cochlear implants in patients with single-sided deafness.
By Elina Kari, MD
Clinical Assistant Professor of Otolaryngology, Caruso Department of Otolaryngology – Head and Neck Surgery