As in all tumors of the central nervous system, the basic three treatment options are neurosurgical resection, radiotherapy, and chemotherapy. Since VS are benign tumors, WHO I, standard chemotherapy and conformal radiotherapy are per se no primary treatment options. Purely from the point of tumor biology, gross total surgical resection is the treatment of choice since it carries the strongest potential of cure. However, in VS surgery functionality of the involved cochlear nerve and facial nerve is the most important cofactor. The rate of functional preservation is on one hand strongly dependent on the experience of the surgeon and the employed microsurgical technique; on the other hand, it depends on tumor-associated factors like adherence/infiltration, tumor size, and level of preoperative hearing [15, 16]. In case of bilateral VS in NF2, a real long-term threat of bilateral deafness and facial nerve paralysis exists. Therefore, the avoidance of functional deficits has even higher priority, especially in children. Consequently, we have shifted our surgical strategy in children away from GTR as outlined below.

In sporadic unilateral VS in adults, Gamma Knife radiosurgery is meanwhile a firmly established alternative treatment option for smaller- to medium-sized tumors with a large body of available literature, suggesting good tumor control rates in the 90 % range, preservation rate for serviceable hearing of 50–80 %, and long-term facial nerve injury rate of 1 % [17–20] Long-term outcome analysis beyond 15 years however is still rare in the literature.

Only a few studies have targeted a larger number of NF2 patients with radiosurgery [21–25]. However, in none of those series, the few included pediatric patients have been analyzed separately. Concerns regarding Gamma Knife treatment in VS of NF2, as evident from the most recent series [21] like lower control rates in younger patients, rather rapidly decrease of hearing function over the first 5 years from 76 % after 1 year to 48 % after 5 years and the fact that there is a 18.8 relative risk for induction of new schwannomas and a real risk of malignant transformation after radiosurgery [26] do apply even more to the pediatric age group, where long-term stability is the most prominent treatment goal in smaller tumors with preserved hearing. In one series of NF2 patients treated with Gamma Knife, only 6 of 14 NF2 patients (43 %) maintained their preoperative useful hearing at 3 years [25]. Furthermore, our adult experience from surgical intervention in growing tumors after radiosurgery is that of very difficult tumor removals with a high risk of facial nerve injury. We therefore do not recommend radiosurgery in the management of pediatric VS, especially in the most common setting of NF2.

An experimental chemotherapeutic approach with bevacizumab has shown some promising results very recently in NF2 patients regarding tumor response and hearing improvement [27, 28]. However, it could be shown that this effect is only sustained under continued therapy and rebound occurs after therapy stops [29]. No experiences in adolescence have been published so far. Therefore, this option, which remains experimental since the drug is not approved for the use in NF2 and schwannomas, is not suitable for pediatric application.

Children without NF2 and sporadic vestibular schwannomas will most likely be diagnosed at a time of beginning hearing loss when the tumor has already grown to a considerable size of at least T3, mostly T4a and T4b. In a series of seven sporadic pediatric VS [30], the average tumor size was even considerably larger than in a meta-analysis of 1,345 adult patients [31]. In these children both the (beginning of) hearing impairment and brain stem compression are indications for surgical treatment.

Children with NF2 are different, especially if they are diagnosed early at a time of unimpaired hearing harboring still small tumors. The major threat coming from those early diagnosed bilateral VS to children is the development of complete deafness in the next 10–20 years, not brain stem compression. The latter is most of the time present in late discovered cases which are often unilaterally deaf. Therefore, a pediatric treatment algorithm has to aim primarily at hearing preservation and, consequently, only second at facial nerve integrity and then at brain stem compression and lastly at gross total resection. Multiple management strategies are at hand. Already the question of timing of interventions ranges theoretically from prophylactic treatment despite unimpaired hearing at the time of discovery to prophylactic treatment despite unimpaired hearing at the time of proven growth, to intervention at the time of beginning hearing loss, to treatment after loss of functional hearing, to, finally, treatment only at the time of brain stem compression.

Figure 50.2 presents the “Tübingen algorithm” for the treatment of pediatric VS in NF2 patients, which is derived from treatment principles put forward by Samii and coworkers already years ago [9]. According to this algorithm, a treatment indication exists in T1 and T2 tumors at the time of tumor growth; in T3a we discuss with the family to wait or not until tumor growth has been proven. In T3b and T4a and T4b, we recommend treatment at time of diagnosis.

In all cases of functional hearing and bilateral T1, T2, and T3a, the goal is to perform a decompression of the cochlear nerve by (a) opening the bony posterior circumference of the internal auditory canal and (b) partial resection of the tumor under strict control of the integrity of BAEP. The resection is stopped if BEAP starts to deteriorate and does not recover within a short time to the baseline levels.

The quality of preoperative bilateral BAEP is essential in the decision-making process. If the tumor size is similar, the side with the better BEAP is operated first since the better BEAP, the more sensitive and reliable is the intraoperative guidance according to neurophysiological monitoring and the higher are the chances of preservation of functional hearing. If BEAP is of similar good quality on both sides, we operate on the side of the larger VS first. If the presurgical goal of hearing preservation has been achieved, we operate on the other side, as soon as there is documented growth. If hearing has deteriorated to a nonfunctional level due to surgery, the patient has to undergo training for lip reading and sign language. Treatment of the other side is then delayed and performed, according to the same principles, if tumor size is progressing significantly. Only in rare case BEAP is deteriorating without discernible tumor growth.

If tumors are uni- or bilaterally larger than T3a and the child has maintained bilateral functional hearing, we recommend surgery at the time of diagnosis and treat the side of more significant brain stem compression first, again aiming at hearing preservation and not at total removal. In case of preservation or loss of hearing, treatment of the other size is as in smaller tumors.

In patients with unilateral functional hearing loss or complete deafness at the time of diagnosis, tumors are almost always larger than T3a on the more severely affected side. The aim is now to resect the VS on this side as radical as possible, guided by the preservation of facial nerve function according to intraoperative facial motor evoked potentials and responses to direct stimulation of the facial nerve. The treatment of the other, still hearing, side follows the same principles as outlined above.

In patients with bilateral loss of functional hearing, the side with the larger brain stem compression is of course treated first, again aiming primarily at preservation of facial nerve function and not at total removal.

In T1, T2, and T3a tumors, we perform surgery in supine position with the head turned to the contralateral side, the same positioning as used for vascular decompression procedures in the cerebellopontine angle. A park bench position is not necessary in children who usually have no limitations in head rotation. In larger tumors we prefer a semi-lying position under permanent surveillance of the right atrium via transesophageal ultrasound for early and highly sensitive detection of air embolism. The semi-lying position combines an upright head position with higher intrathoracic and cervical venous pressure than in sitting position which reduces the risk of air embolism. The major surgical advantage of the vertical head position is the fact that irrigation replaces suction to keep the operating field clear of blood and that bimanual dissection by the surgeon, which in our experience is the key feature for preservation of function, is enabled.

We perform a retrosigmoid lateral suboccipital approach via craniotomy, which is placed just medial to the sigmoid sinus and below the transverse sinus according to landmarks and thorough study of the bone window CT scans. A craniectomy, which is our standard procedure in adults, is not warranted since the dura is not firmly attached to the bone and robust in children and adolescents. Dura opening is performed in parallel to the transverse and sigmoid sinus and the CPA cistern opened to drain CSF. Afterward the cerebellum is smoothly retracted and the tumor exposed. The dura covering the posterior petrous bone is cut in a semicircular fashion with its base at the meatus of the internal auditory canal (IAC) and the dura excised. The posterior wall of the IAC is then completely removed with a diamond drill exposing the IAC as far lateral as possible. The preoperative bone window CT scan provides the necessary information to define the limits of a safe approach sparing functionally important structures like the labyrinth [32, 33]. Opening of labyrinthine structures results in irreversible hearing loss due to outflow of the endolymph from the inner ear.