Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder, and bilateral vestibular nerve sheath tumors are the characteristic manifestation of NF2. Although vestibular nerve sheath tumors are benign, they can still cause severe cranial nerve symptoms and even death due to their anatomical location. Surgery is currently the main treatment modality for NF2 vestibular nerve sheath tumors. 1. Treatment strategy and timing: Vestibular nerve sheath tumor is the most common cranial nerve sheath tumor, which is clinically treated with conservative observation, microsurgery or radiation therapy based on factors such as tumor volume, severity of symptoms and treatment risk. Hearing and facial nerve function preservation have become the most important indicators for objective evaluation of the efficacy of vestibular nerve sheath tumors, with hearing and facial nerve preservation rates of 50%-88% and 94-100%, respectively, for tumors <2.0 cm in diameter, recurrence, or postoperative residual tumors. Surgical procedures have a slightly lower rate of neurological preservation than radiotherapy, but can preserve function for a long time if the tumor is completely excised. NF2 is characterized by bilateral vestibular nerve sheath tumors, and if not optimally treated, patients are ultimately at risk for deafness and bilateral facial palsy. However, due to the low incidence of NF2, there are controversies in the treatment: some studies have shown that the average growth rate of NF2 vestibular nerve sheath tumors with a maximum diameter <2 cm is 1 to 2 mm/year, suggesting that the growth can be observed for a long time until the hearing is severely impaired or brainstem compression symptoms appear, so that patients can preserve their hearing for as long as possible; some scholars believe that early surgical excision of the tumor can better preserve the function of the facial and auditory nerves. Most of the NF2 patients in this group are young, and the hearing loss from decline to basic loss is usually 2-4 years, but some of the tumors may cause the pressure in the internal auditory canal to rise for a short time, causing sudden hearing loss. Therefore, we believe that:Patients with nerve sheath tumors <25px< span="">maximum diameter at diagnosis and with good hearing (PTA not exceeding 20dB or speech ≥80%) may be selected for conservative observation, during which treatment with VEGF, EGFR and ErbB receptor inhibitors is recommended. Prompt surgical removal of the tumor should be considered when further hearing loss occurs. Treatment in the presence of tumor compression of the brainstem or loss of functional hearing greatly reduces the chances of preserving neurological function. In controlling the growth of NF2 vestibular nerve sheath tumor and preserving facial nerve function, stereotactic radiation therapy has better results. One study showed that more than 2/3 of cases were progression-free within 5 years after gamma-knife irradiation, and damage to the facial nerve rarely occurred. However, radiation therapy has limitations on long-term hearing preservation, especially for cases with early onset and large tumor size, which not only tend to have more severe tinnitus and/or hearing loss in a short period of time, but also cannot provide useful hearing for a long period of time. Also, intraoperative visible irradiation makes the tumor more prone to adhesions, which increases the difficulty of intraoperative tumor and nerve separation. Therefore, the following NF2 patients (i) patients with one side of the tumor removed and useful hearing preserved, and (ii) middle-aged and elderly patients with tumor maximum diameter <2 cm and hearing loss, may choose to use body directed radiation therapy. The choice of surgical approach for NF2 vestibular nerve sheath tumor mainly depends on the patient's hearing, tumor location and the operator's experience, and the commonly used surgical approaches include: transvagal approach, inferior occipital-posterior ethmoid sinus approach and transcranial base approach. This approach can fully expose the pontocerebellar horn area and provide a good surgical field, which can effectively protect the brainstem and adjacent neurovascular when resecting the tumor, and can also remove other adjacent nerve sheath tumors and meningiomas, and has good effect on relieving hydrocephalus and chronic occipital foramen hernia. However, preoperative judgment of the pressure in the posterior cranial recess and the severity of cerebellar tissue compression is needed. Before opening the dura, spinal fluid can be released from the arachnoid of the occipital foramen to reduce tension, and the cerebellum should be gently stretched during exposure to avoid contusion of brain tissue. Maximizing tumor removal while effectively preserving neurological function is the key to the success of NF2 vestibular nerve sheath tumor resection surgery. While sporadic vestibular nerve sheath tumors usually compress the facial nerve to the ventral side, NF2 vestibular nerve sheath tumors tend to be hard, lobulated or multi-layered, and often encase and infiltrate the facial and vestibular snail fibers. In our group, about 40% of the cases showed lobar infiltrative growth, especially the larger tumors would completely wrap the facial and vestibular nerves, which caused great difficulties in tumor resection and tissue separation. Intraoperatively, close electrophysiological monitoring should be used to determine and alert the nerve alignment in advance. After intra-tumoral decompression, the brain stem end of the facial nerve and the endo-aural tract end need to be carefully identified. For tumors that cannot be separated from the facial nerve, a small amount of residual can be left after sharp resection, and the upper pole of the tumor should be traced along the nerve distally and separated, and the ipsilateral talocrine and trigeminal nerves should be carefully separated. The lower pole of the tumor mostly has a more obvious demarcation with the posterior group of cranial nerves. If multiple nerve sheath tumors are seen, they should be resected at the same time. Hearing preservation and reconstruction The postoperative hearing preservation of patients with NF2 vestibular neuroma depends on many factors, which are closely related to preoperative hearing, tumor growth site and volume, surgical approach and surgical technique. In our group, 21.9% of NF2 patients preserved useful hearing, and their preoperative AAO-HNS classification were all in groups A and B. It is less likely for patients with preoperative hearing impairment to preserve and recover their hearing. In contrast, hearing loss for more than 2 years or vestibular neuroma >75px are important factors that increase the risk of postoperative hearing loss. In addition, direct stretching and separation of the cochlear nerve and grinding and drilling to open the bone of the inner ear canal during surgery can cause some degree of hearing loss. The choice of hearing reconstruction is based on whether the anatomical structure of the cochlear nerve is preserved. Intraoperative ABR testing can initially determine residual hearing, while CNAP testing can clarify the integrity of the cochlear nerve. If the tumor is <2 cm in diameter and the function of the cochlear nerve can be preserved, intraoperative or secondary implantation of a cochlear implant may be chosen to improve hearing function in patients with NF2. Patients whose bilateral cochlear nerve is not preserved may opt for an auditory brainstem implant (ABI), which is used to stimulate the cochlear nucleus in the brainstem to obtain partial hearing. 4. Conclusion Bilateral vestibular nerve sheath tumors are the most important feature of NF2, and microsurgery is an effective method for treating NF2 vestibular nerve sheath tumors. While removing the tumor and reducing brainstem compression, preservation of facial auditory nerve function is crucial. Early diagnosis and accurate timing of surgery should avoid damage to facial and auditory nerve function when removing the tumor as much as possible through microsurgery, which can effectively improve the long-term survival quality of NF2 patients.