Neurofibromatosis Type II (NF2) Fact Sheet
August 20, 2008
DESCRIPTION Neurofibromatosis Type II (NF2) is a genetic disease (autosomal of NF2: dominant) of the nervous system characterized by tumors (schwannomas) growing on both vestibular nerves that adversely affect the auditory and facial nerves. This disease occurs approximately one in 25,000 live births in the U.S. Profound hearing loss and some facial paralysis result from the growth of bilateral tumors on these nerves. Because of the location of the tumors, their removal often necessitates severing the auditory nerve.
TREATMENT: If the auditory nerve is severed, a cochlear implant (CI) cannot be used to treat an individual with NF2 because the auditory nerve is not able to carry signals from the cochlea to the cochlear nucleus in the brainstem. In such cases, an NF2 patient may benefit from an auditory brainstem implant (ABI), which is designed to stimulate the auditory portion of the cochlear nucleus in the brainstem and send sound signals directly to the brain. In some cases, such as where small tumors have been removed with preservation of the auditory nerve, or where the tumor has been treated with x-ray therapy with auditory nerve preservation, a cochlear implant may be beneficial. This option has given variable results, in some cases providing good hearing benefit, and in other cases providing no better than an ABI. Where possible, the CI option is given careful consideration. In some cases, CI use may be of limited duration if there is further growth in residual or recurrent acoustic tumor. If further surgery is required and CI use is no longer possible then an ABI may be a good option.
RESEARCH: In the past decade, great strides have been made in terms of radiographic diagnosis, treatments, surgical approaches to vestibular schwannomas and understanding of the molecular biology of NF2. Similar advances also have been made in understanding the natural history of vestibular schwannomas, which is fundamental to the advancement of treatments, have not been made. HEI has undertaken a clinical study to define the growth rate and clinical course of vestibular schwannomas in NF2-affected individuals. Results of the study have led to a better understanding of vestibular schwannomas in NF2 and improved the framework of clinical centers, data management and scientific expertise for future studies and treatment trials.
TREATMENT: If the auditory nerve is severed, a cochlear implant (CI) cannot be used to treat an individual with NF2 because the auditory nerve is not able to carry signals from the cochlea to the cochlear nucleus in the brainstem. In such cases, an NF2 patient may benefit from an auditory brainstem implant (ABI), which is designed to stimulate the auditory portion of the cochlear nucleus in the brainstem and send sound signals directly to the brain. In some cases, such as where small tumors have been removed with preservation of the auditory nerve, or where the tumor has been treated with x-ray therapy with auditory nerve preservation, a cochlear implant may be beneficial. This option has given variable results, in some cases providing good hearing benefit, and in other cases providing no better than an ABI. Where possible, the CI option is given careful consideration. In some cases, CI use may be of limited duration if there is further growth in residual or recurrent acoustic tumor. If further surgery is required and CI use is no longer possible then an ABI may be a good option.
RESEARCH: In the past decade, great strides have been made in terms of radiographic diagnosis, treatments, surgical approaches to vestibular schwannomas and understanding of the molecular biology of NF2. Similar advances also have been made in understanding the natural history of vestibular schwannomas, which is fundamental to the advancement of treatments, have not been made. HEI has undertaken a clinical study to define the growth rate and clinical course of vestibular schwannomas in NF2-affected individuals. Results of the study have led to a better understanding of vestibular schwannomas in NF2 and improved the framework of clinical centers, data management and scientific expertise for future studies and treatment trials.
Department of Auditory Implants and Perception (DAIP) at HEI worked to improve the technology of the existing auditory brainstem implant (ABI) through the development of the penetrating auditory brainstem implant (PABI). Findings from this study demonstrated that microstimulation with penetrating electrodes provided useful pitch information at low stimulation levels to device recipients. The sound cues were useful in combination with sensations provided by traditional surface ABI electrodes.. Further work is continuing on other penetrating electrode designs. The current FDA approved ABI provides most recipients benefit through increased sound awareness, which aids in lipreading, and a small percentage of recipients have achieved near cochlear implant levels of performance. ABI candidates are thoroughly counseled about what to expect from an ABI, including the fact that the ABI always works best in combination with lipreading cues, and that regular use of the ABI contributes greatly to long-term benefit. ABI recipients have shown the ability to continue to improve in performance for 10 years or longer.
CONTACT:
Kirsten Holguin
Kirsten Holguin
Communications Manager,
House Ear Institute
House Ear Institute
