One of the main criticisms of vestibular schwannoma (VS) radiosurgery is that the risk of surgical morbidity is increased for patients whose tumor progresses in cases of failed procedures. The authors reviewed the French neurosurgical experience of operated patients after failed Gamma Knife radiosurgery (GKR). From July 1992 to December 2000, 23 unilateral VS out of the 1,000 treated patients have undergone a microsurgical procedure after failed GKR. In order to analyze the difficulties observed during the surgery, a questionnaire was completed by the surgeons. The mean interval between radiosurgery and removal was 39 months (range: 10-92 months). The mean increasing volume was 389% (range: 37-1,600) and the median was 150%. Seven patients have been operated on for radiological tumor growth and 13 for clinicoradiological evolution. In 10 cases, the surgeon considered that he had to face unusual difficulties mainly because of adhesion of the tumor to neurovascular structures. Tumor removal was total in 15 cases, near total in 4 cases and subtotal in 4 cases. One case of venous infarction was noticed on the 2nd day following surgery and was responsible for hemiparesis and aphasia that gradually recovered. At the last follow-up examination, facial nerve was normal or near normal (House-Brackmann grades 1 and 2) in 12 cases (52%) while it was grade 3 in 9 cases and grades 4 and 5 in 2 cases. Our results show that the quality of removal and of facial nerve preservation might be impaired after GKR in half of cases. However, these results do not support a change in our policy of first intention radiosurgical treatment of small- to medium-sized 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.

Recurrent and regrowing large vestibular schwannomas (VSs) may require another microsurgical procedure. Little is known about the incidence and the consequences of this second surgical procedure. We reviewed our own 10 reoperated cases during a 20-year period. Eight of them were supposed to have a radical surgery at the initial step, while 2 had experienced a subtotal resection. The mean interval between the 2 surgeries was 8.3 years with an ultra-late recurrent case at 20 years. Additional surgery was justified by a large-sized growing tumor in main cases and/or occurrence of new symptoms. We used a widened translabyrinthine approach in 9 cases and a retrosigmoid route in 1 case. Preservation of a good facial nerve motion (H-B gd I or II) was obtained in 3 out of the 6 cases who displayed this preoperative status. Excluding the facial nerve injury, no major complication was observed in these cases. These results confirm that the iterative surgical procedure for VS carries additional difficulties with respect to functional preservation. Assuming that radiosurgery is an effective tool to control small- to middle-sized VSs, priority was recently given to the facial nerve preservation during the surgical removal of recurrent and regrowing VSs.

No abstract