A woman in her 20s was referred to the Division of Otolaryngology–Head and Neck Surgery at Duke Medicine for evaluation. She had been diagnosed in her teens with neurofibromatosis type 2 (NF2), a rare hereditary disorder characterized by the development of bilateral Schwann cell tumors (also known as acoustic neuromas) affecting the vestibulocochlear nerve.
The patient was a single mother who previously left her job because of hearing loss associated with NF2, but she now wanted to return to employment. She had visited several specialty centers across the country seeking alternatives to treatment. She was advised to undergo surgery to remove the tumors and to either learn sign language or receive an auditory brain stem implant to partially restore her hearing.
Question: Are there any new technologies in the surgical treatment of NF2 that can restore or preserve hearing function?
Answer: Yes, a unilateral cochlear implant with partial removal of the acoustic neuroma on the implant side and full removal of the tumor on the nonimplant side can help restore or preserve hearing in NF2.
Because the tumors that develop in NF2 can grow large enough to cause hearing loss and compression of the brain stem, tumor removal is typically recommended. However, removal also severs the auditory (cochlear) portion of the vestibulocochlear nerve, subsequently causing complete deafness.
Although the recent development of auditory brain stem implants has helped individuals with NF2 retain some level of hearing, hearing capacity remains substantially impaired in many patients.
At the time the patient came to Duke, she had hearing loss and brain stem compression from bilateral acoustic neuromas, although she had not yet developed symptoms associated with the compression.
The patient saw Duke otolaryngologist David Kaylie, MD, who recommended a novel approach to treatment—a unilateral cochlear implant with partial removal of the acoustic neuroma on that side and full removal of the tumor on the opposite side. This approach, which is rarely performed in the United States, preserves the integrity of the auditory nerve and provides sufficient tumor debulking to decompress the brain stem for an extended period of time.
Although cochlear implants can provide superior results in restoring hearing in patients with deafness, such implants have not been considered an option in patients with NF2 because surgical removal of the neuromas severs the auditory nerve, thus rendering cochlear implants ineffective. This is because the implants function by sending electrical impulses to the brain via the auditory nerve.
Kaylie said that he and his colleagues at Duke sometimes use cochlear implants in patients with NF2 who are deaf and whose tumors are small enough that immediate removal is not required. However, the planned treatment approach for this patient will be truly unique.
“Right now, her brain stem is very compressed by both tumors, so we’ll partially remove this tumor and put in a cochlear implant that will restore hearing in that ear,” Kaylie described. “Then, in a few months, we can perform a second surgery to completely remove the tumor on the other side.”
Unilateral cochlear implantation with partial tumor removal in patients with NF2 has been undertaken a few times in the United States. To prevent injury to the auditory nerve, Kaylie said he will use new technology to help him assess whether he is getting too close to the auditory nerve during tumor resection.
“We are using a technique where we monitor hearing while the tumor is being resected using wireless cochlear implant technology. This allows us to get a more complete resection without damaging the nerve,” Kaylie expounded. “No one has ever done this before.”
The take-home message, Kaylie said, is that approaches to hearing loss—whether caused by NF2 or another condition—should be centered on the patient. “Here at Duke, rather than saying everyone with NF2 should get an auditory brainstem implant or everyone has to learn sign language, we’re implementing novel ways to preserve hearing for as long as possible,” he explained.