Auditory canal decompression is another surgical technique that can prolong usable hearing when a vestibular schwannoma has grown too large to remove without damage to the cochlear nerve. In the IAC (internal auditory canal) decompression, a middle fossa approach is employed to expose the bony roof of the IAC without any attempt to remove the tumor. The bone overlying the acoustic nerve is removed, allowing the tumour to expand upward into the middle cranial fossa. In this way, pressure on the cochlear nerve is relieved, reducing the risk of further hearing loss from direct compression or obstruction of vascular supply to the nerve. Radiosurgery is a conservative alternative to cranial base or other intracranial surgery. With conformal radiosurgical techniques, therapeutic radiation focused on the tumour, sparing exposure to surrounding normal tissues. Although radiosurgery can seldom completely destroy a tumor, it can often arrest its growth or reduce its size. While radiation is less immediately damaging than conventional surgery, it incurs a higher risk of subsequent malignant change in the irradiated tissues, and this risk is higher in NF2 than in sporadic (non-NF2) lesions. Medications
There are no prescription medicines currently indicated for reduction in tumor burden for NF2 patients, although in patient studies Bevacizumab has resulted in reduction in tumor growth rates and hearing improvements in some patients.
The last revision of the NF2 criteria was done by M.J. Smith in 2017. This included the consideration of a LZTR1 mutation (schwannomatosis) instead of NF2 and excluded bilateral vestibular schwannomas that occur after 70 years of age. Treatment
Surgery
There are several different surgical techniques for the removal of acoustic neuroma. The choice of approach is determined by size of the tumour, hearing capability, and general clinical condition of the person. The retrosigmoid approach offers some opportunity for the retention of hearing. The translabyrinthine approach will sacrifice hearing on that side, but will usually spare the facial nerve. Post-operative cerebrospinal fluid leaks are more common. The middle fossa approach is preferred for small tumors and offers the highest probability of retention of hearing and vestibular function. Less invasive endoscopic techniques have been done outside of the United States for some time. Recovery times are reported to be faster. However, this technique is not yet mainstream among surgeons in the US.Larger tumors can be treated by either the translabyrinthine approach or the retrosigmoid approach, depending upon the experience of the surgical team. With large tumors, the chance of hearing preservation is small with any approach. When hearing is already poor, the translabyrinthine approach may be used for even small tumors. Small, lateralized tumours in people with NF2 with good hearing should have the middle fossa approach. When the location of the tumour is more medial a retrosigmoid approach may be better.