Current Concepts in the Evaluation and Treatment of Neurofibromatosis Type II
Section snippets
Clinical presentation
Patients affected with NF2 are usually diagnosed between the second and fourth decade, but up to 18% of patients present under the age of 15 years [19]. Up to 41% of patients who eventually develop NF2 do not present with bilateral vestibular schwannomas; therefore, some adult patients can present with unilateral sensorineural hearing loss (SNHL) rather than symmetric or asymmetric bilateral SNHL [10]. The hearing loss is usually progressive, but sudden SNHL can occur. The patient can also
Clinical and genetic screening for neurofibromatosis type II
The evaluation of a patient at risk for developing NF2 should begin with audiometric testing. A T1-weighted, gadolinium-enhanced MRI of the brain and internal auditory canals should be obtained if there is asymmetric hearing loss, or if the hearing is normal and there is a family history or other stigmata of NF2 disease. Some physicians advocate auditory brainstem response and acoustic reflex studies, which can be helpful but should not replace the MRI as a screening procedure because they have
Hearing rehabilitation
Early in the course of NF2, conventional hearing aids may be useful for moderate hearing loss. There are two options for bilateral hearing restoration in severely to profoundly deafened individuals with NF2. Both cochlear implant (CI) and auditory brainstem implants (ABI) can be used in specific situations to provide hearing for the NF2 patient. A CI is used to stimulate auditory neurons in the cochlea and requires preservation of an intact cochlear nerve during tumor removal. Even though the
Treatment
The initial treatment decisions are influenced by tumor size, location, patient age, and hearing status. Early surgical intervention with attempted hearing preservation in NF2 patients, as opposed to delaying tumor removal until after all useful hearing has been lost by tumor compression or invasion, is a greatly debated topic. The authors believe that early detection and treatment of NF2 tumors provides much greater opportunity for hearing preservation [7], [38]. Additionally, they believe
Potential future therapies
The NF2 gene encodes a tumor-suppressor protein product, merlin [12]. It is hoped that understanding merlin's interactions with other proteins, signaling pathways, and regulation of the NF2 gene will lead to the development of novel treatments for vestibular schwannomas. Ultimately, targeted molecular interventions and drug therapies will be designed to stop schwannoma progression or to eradicate preexisting tumors altogether. Such treatments will offer alternatives to the current options of
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