Object The roles of the wait-and-see strategy and proactive Gamma Knife surgery (GKS) in the treatment paradigm for small intracanalicular vestibular schwannomas (VSs) is still a matter of debate, especially when patients present with functional hearing. The authors compare these 2 methods. Methods Forty-seven patients (22 men and 25 women) harboring an intracanalicular VS were followed prospectively. The mean age of the patients at the time of inclusion was 54.4 years (range 20–71 years). The mean follow-up period was 43.8 ± 40 months (range 9–222 months). Failure was defined as significant tumor growth and/or hearing deterioration that required microsurgical or radiosurgical treatment. This population was compared with a control group of 34 patients harboring a unilateral intracanalicular VS who were consecutively treated by GKS and had functional hearing at the time of radiosurgery. Results Of the 47 patients in the wait-and-see group, treatment failure (tumor growth requiring treatment) was observed in 35 patients (74%), although conservative treatment is still ongoing for 12 patients. Treatment failure in the control (GKS) group occurred in only 1 (3%) of 34 patients. In the wait-and-see group, there was no change in tumor size in 10 patients (21%), tumor growth in 36 patients (77%), and a mild decrease in tumor size in 1 patient (2%). Forty patients in the wait-and-see group were available for a hearing level study, which demonstrated no change in Gardner-Robertson hearing class for 24 patients (60%). Fifteen patients (38%) experienced more than 10 db of hearing loss and 2 of them became deaf. At 3, 4, and 5 years, the useful hearing preservation rates were 75%, 52%, and 41% in the wait-and-see group and 77%, 70%, and 64% in the control group, respectively. Thus, the chances of maintaining functional hearing and avoiding further intervention were much higher in cases treated by GKS (79% and 60% at 2 and 5 years, respectively) than in cases managed by the wait-and-see strategy (43% and 14% at 2 and 5 years, respectively). Conclusions These data indicate that the wait-and-see policy exposes the patient to elevated risks of tumor growth and degradation of hearing. Both events may occur independently in the mid-term period. This information must be presented to the patient. A careful sequential follow-up may be adopted when the wait-and-see strategy is chosen, but proactive GKS is recommended when hearing is still useful at the time of diagnosis. This recommendation may be a main paradigm shift in the practice of treating intracanalicular VSs.

The issue of recurrence of vestibular schwannomas is poorly studied by the surgical literature and is probably underestimated. Our own long-term retrospective analysis after translabyrinthine approach has indicated a 9.2% recurrence rate. This long-term event is mainly due to regrowth of microfragments that have been left in the operative field along the course of the facial nerve or at the surface of the pons. Management of recurrence depends on the tumor size and patient's condition. Our current policy is to propose a Gamma Knife radiosurgical treatment in eligible cases. Prospective long-term follow-up studies using serial MR imaging after radical removal should bring reliable data about the incidence of vestibular schwannoma recurrence.

Hydrocephalus may occur at various stages of the natural course of vestibular schwannoma and can also be diagnosed after the therapeutic procedure. The aim of the present study was to analyze the impact of Gamma Knife radiosurgery (GKR) on previously diagnosed hydrocephalus (group A patients) and to evaluate the incidence of de novo hydrocephalus after GKR (group B patients). We reviewed retrospectively our case material and the data from the literature. Among the first 1,000 vestibular schwannoma patients treated by GKR in our institution, 30 patients (3%) belonged to group A and 1% to group B. In both groups, hydrocephalus was more often associated with the following data: Elderly, large tumor, previous MS, NF2 disease and bilateral tumors. Cerebrospinal fluid (CSF) shunting system was needed in 25% of the group A and in all of the group B patients. In this latter group, CSF shunting was justified by poor clinical tolerance, and the mean interval between GKR and CSF shunting was 14.8 months (range: 4-31 months). These data suggest that GKR does not decompensate the majority of preexisting radiological hydrocephalus. De novo post-GKR hydrocephalus is of low incidence, comparable to the postoperative rate. Generally, it comes early after GKR and justifies CSF shunting. Thus, it may be postulated that in a small subgroup of patients, GKR may disturb the normal hydrodynamic pathway. Mechanisms of such event remain controversial.

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To refine our therapeutic policy for intracanalicular tumors, we reviewed our series of patients who where initially treated conservatively. Forty-seven patients (22 men and 25 women) harboring an intracanalicular vestibular schwannoma were followed prospectively. Mean age at the time of inclusion was 54.4 (20-71) years. The mean follow-up period was 43.8 months (+/-40 months) ranging from 9 to 222 months. Failure was defined as significant tumor growth and/or hearing deterioration that required a microsurgical or radiosurgical treatment. Failure was observed in 35 cases while a conservative treatment is still ongoing in 12 patients. Ten patients kept an unchanged tumor size (21.3%), while 36 patients experienced a tumor growth (76.6%), and 1 patient experienced a mild decreased tumor size (2.1%). Among the 40 patients who where available for hearing level study, 24 patients (60%) did not change their Gardner and Robertson hearing class. Fifteen patients (37.5%) experienced a >10-dB hearing loss and 2 of them became deaf. One patient (2.5%) improved her hearing level from 56.3 to 43.8 dB over a 39.5-month follow-up period. These data suggest that the wait and see policy exposes the patient to degradation of hearing and tumor growth. Both events may occur in an independent way in the middle-term period. This information has to be given to the patient, and a careful sequential follow-up may be adopted when the wait and see strategy is chosen.