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.
They derive from the nerve sheaths of the upper part of the nervus vestibularis in the region between the central and peripheral myelin (Obersteiner-Redlich-Zone) within the area of the porus acousticus, 1 cm from the brainstem. Genotype–phenotype correlation
Many people with NF2 were included in studies that were designed to compare disease type and progression with exact determination of the associated mutation. The goal of such comparisons of genotype and phenotype is to determine whether specific mutations cause respective combinations of symptoms. This would be extremely valuable for the prediction of disease progression and the planning of therapy starting at a young age. The results of such studies are the following:
In most cases the mutation in the NF2 gene causes shortened peptides. There are no mutational hot spots. People with frameshift mutations or nonsense mutations have poor prognosis. People with missense mutations have a better prognosis. In cases with mutations in the splice-acceptor-region, there is no good correlation to determine. Point mutations may have only minor effects. Cases are published in which exactly the same mutation is associated with clearly different outcomes.These results suggest that other factors (environment, other mutations) will probably determine the clinical outcome. Diagnosis
NF2 is a genetically transmitted condition. Diagnosis is most common in early adulthood (20–30 years); however, it can be diagnosed earlier. NF2 can be diagnosed due to the presence of a bilateral vestibular schwannoma, or an acoustic neuroma, which causes a hearing loss that may begin unilaterally.