Hearing rehabilitation in patients with vestibular schwannomas.

Hearing loss affects 95% of patients with vestibular schwannoma (VS), either because of the disease or its treatment. In untreated tumors, hearing loss is usually progressive but can be sudden and profound in up to 10%. In neurofibromatosis type 2-related schwannomatosis (NF2), where bilateral VS are almost universal, bilateral hearing loss has a greater impact on quality of life than any other factor. Hearing loss may result from vascular compromise of the cochlea, direct damage to the cochlear nerve by the tumor, direct growth of tumor into the cochlea, distortion of the cochlear nucleus by larger tumors, or the buildup of toxic metabolites in CSF, particularly at the fundus of the internal auditory canal. There are numerous means by which hearing can be rehabilitated. Hearing aids are helpful for those who have reasonable residual hearing although hearing distortion is common in VS patients and may limit the amount of benefit. If treatment of a tumor is required, then hearing preservation options such as stereotactic radiosurgery or hearing preservation surgery may be considered if the tumor is small- or medium-sized. However, hearing loss often progresses more quickly following stereotactic radiosurgery and the risk of losing hearing following hearing preservation surgery is as high as 60% depending on tumor size and the approach used. Patients with profound hearing loss often benefit from cochlear implantation as long as the cochlear nerve is intact and open-set speech discrimination is not uncommon. In patients in whom the cochlear nerve is no longer intact (usually following surgery for VS in NF2), auditory brainstem implantation is a viable option although auditory benefit is limited, mainly providing an aid to lip reading.