Assessing Tumor Volume for Sporadic Vestibular Schwannomas: A Comparison of Methods of Volumetry.

INTRODUCTION: The size of vestibular schwannomas (VS) is a major factor guiding the initial decision of treatment and the definition of tumor control or failure. Accurate measurement and standardized definition are mandatory; yet no standard exist. Various approximation methods using linear measures or segmental volumetry have been reported. We reviewed different methods of volumetry and evaluated their correlation and agreement using our own historical cohort. METHODS: We selected patients treated for sporadic VS by Gammaknife radiosurgery (GKRS) in our department. Using the stereotactic 3D T1 enhancing MRI on the day of GKRS, 4 methods of volumetry using linear measurements (5-axis, 3-axis, 3-axis-averaged, and 1-axis) and segmental volumetry were compared to each other. The degree of correlation was evaluated using an intraclass correlation test (ICC 3,1). The agreement between the different methods was evaluated using Bland-Altman diagrams. RESULTS: A total of 2,188 patients were included. We observed an excellent ICC between 5-axis volumetry (0.98), 3-axis volumetry (0.96), and 3-axis-averaged volumetry (0.96) and segmental volumetry, respectively, irrespective of the Koos grade or Ohata classification. The ICC for 1-axis volumetry was lower (0.72) and varied depending on the Koos and Ohata subgroups. None of these methods were substitutable. CONCLUSION: Although segmental volumetry is deemed the most accurate method, it takes more effort and requires sophisticated computation systems compared to methods of volumetry using linear measurements. 5-axis volumetry affords the best adequacy with segmental volumetry among all methods under assessment, irrespective of the shape of the tumor. 1-axis volumetry should not be used.

Dynamics of tumor evolution after Gammaknife radiosurgery for sporadic vestibular schwannoma: defining volumetric patterns characterizing individual trajectory.

BACKGROUND: Definition of tumor control and treatment failure after Gammaknife radiosurgery (GKRS) for vestibular schwannoma (VS) is still debated. The lack of knowledge on the dynamics of tumor evolution can lead to misinterpretation and subsequent inappropriate second treatment. The aim of this study was to evaluate the post-GKRS dynamics of evolution of tumor volume, and characterize volumetric patterns. METHODS: We included patients with sporadic VS treated by GKRS with an MRI follow-up of minimum 3 years. A clustering in 2 steps was performed: definition of the patterns of evolution based on a subset of patients with the most comprehensive follow-up, then assignment of the remaining patients on a best fit basis. The minimum length of follow-up was assessed by measuring the consistency of the clusters over time (Adjusted Rand Index and Normalized Mutual Information). An analysis of the discriminant variables was finally performed. RESULTS: 1,607 patients were included (median follow-up: 67 months). Five patterns were defined with one pattern gathering almost all cases of treatment failure. The clustering at 5 years afforded the highest consistency with long-term follow-up. Discriminant variables for clusters were: sex, initial symptoms, delay of diagnosis, Koos grading, fundus invasion, and number of isocenters. CONCLUSIONS: The definition of these robust distinct patterns is likely to help tremendously the physicians to distinguish tumor control from potential failure. We advocate for no retreatment decision before 5 years post-GKRS. Further investigations are required to decide if the dynamics of evolution can be predicted at GKRS on an individual basis.

Long-Term Hearing Outcome After Radiosurgery for Vestibular Schwannoma: A Systematic Review and Meta-Analysis.

BACKGROUND: Stereotactic radiosurgery (SRS) is one of the main treatment options in the management of small to medium size vestibular schwannomas (VSs), because of high tumor control rate and low cranial nerves morbidity. Series reporting long-term hearing outcome (>3 years) are scarce. OBJECTIVE: To perform a systematic review of the literature and meta-analysis, with the aim of focusing on long-term hearing preservation after SRS. METHODS: Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we reviewed articles published between January 1990 and October 2020 and referenced in PubMed or Embase. Inclusion criteria were peer-reviewed clinical study or case series of VSs treated with SRS (single dose), reporting hearing outcome after SRS with a median or mean audiometric follow-up of at least 5 years. Hearing preservation, cranial nerves outcomes, and tumor control were evaluated. RESULTS: Twenty-three studies were included. Hearing preservation was found in 59.4% of cases (median follow-up 6.7 years, 1409 patients). Main favorable prognostic factors were young age, good hearing status, early treatment after diagnosis, small tumor volume, low marginal irradiation dose, and maximal dose to the cochlea. Tumor control was achieved in 96.1%. Facial nerve deficit and trigeminal neuropathy were found in 1.3% and 3.2% of patients, respectively, both significantly higher in Linear Accelerator series than Gamma Knife series ( P < .05). CONCLUSION: Long-term hearing preservation remains one of the main issues after SRS, with a major impact on health-related quality of life. Our meta-analysis suggests that hearing preservation can be achieved in almost 60% of patients after a median follow-up of 6.7 years, irrespective of the technique.

Open surgical reconstruction of the internal carotid artery aneurysm at the base of the skull.

OBJECTIVES: Aneurysms of the internal carotid artery (ICA) at the base of the skull are uncommon dangerous lesions whose management remains unclear. The aim of this retrospective study is to report a standardized surgical technique of ICA reconstruction with long-term results. METHODS: Between 1988 and 2005, 13 patients (11 men; age 18 to 76 years, mean 42.6 years) underwent lateral skull base approach with cervical-to-petrous carotid artery bypass for repair of ICA aneurysms. Principal elements of the technique were: partial resection of the parotid gland without rerouting of the facial nerve; luxation of mandibula; drilling of the bone. RESULTS: The 13 patients had unilateral aneurysm of the ICA at the base of the skull. Four aneurysms were of atherosclerotic origin; six fibromuscular dysplasia; two post-traumatic; one cause was undetermined. The mean diameter of the aneurysms was 12 mm (range, 7-21 mm). Twelve patients were symptomatic: six presented neurological events (four strokes, two transient ischemic attack [TIA]); two retinal events; three compressive symptoms (two Horner's syndrome and one paralysis of the glossopharyngeal nerve); one patient presented a visible pulsatile mass in the neck. One patient was asymptomatic. There were no post-operative deaths, one TIA, 13 transient palsies of the lower facial nerve, and one transient palsy of accessory nerve. Palsy of cranial nerves was partial and disappeared within a mean of 5.6 months (range, 1-10 months). The postoperative angiogram showed patency in all but one case (one asymptomatic thrombosis). During follow-up (mean, 152 months), there was one unrelated death, one focal epileptic seizure, and one controlateral TIA. In November 2008, duplex showed patency of all 11 grafts (one death, one thrombosis). At 10 years, the survival, cumulative stroke-free survival, ipsilateral stroke-free, and patency rates was were 90.9%, 100%, 100%, and 92.3%. CONCLUSION: Venous graft bypass from the cervical-to-petrous ICA can be performed safely with such an approach and produces durable satisfactory results.

Place of Gamma Knife Stereotactic Radiosurgery in Grade 4 Vestibular Schwannoma Based on Case Series of 86 Patients with Long-Term Follow-Up.

INTRODUCTION: Grade IV vestibular schwannoma (Koos classification) is generally considered to be an indication for microsurgical resection or combined radiosurgery-microsurgery. However, the place of Gamma Knife stereotactic surgery (GK-SRS), either as first-line treatment or when progression of residual tumor compresses the brainstem, has not been clearly evaluated. This article reports the results of a large case series of patients with grade 4 vestibular schwannoma treated by GK-SRS. MATERIAL AND METHOD: All consecutive patients with grade IV vestibular schwannoma treated by GK-SRS in our department between 1996 and 2011 with a minimum follow-up of 3 years were included in this study. RESULTS: 86 patients were treated by GK-SRS with a minimum follow-up of 3 years. Mean follow-up was 6.2 years (3-16 years). The mean age of the patients at the time of GK-SRS was 54.6 years (range: 23-84) and the sex ratio was 0.6. At the time of radiosurgery, no patient presented brainstem dysfunction prior to GK-SRS. 38 patients had functional hearing before treatment. One patient presented mild trigeminal neuralgia before GK-SRS. Tumor control with no clinical deterioration was obtained in 78 patients (90.7%). No radiation-induced brainstem or cranial nerve toxicity was observed in any of these patients. Functional hearing was maintained in 25 patients. 8 (9.3%) patients presented tumor growth and required microsurgical resection in 7 cases and ventricular shunt in 1 case. CONCLUSION: On the basis of this large series, GK-SRS appears to be a safe and effective treatment option for grade IV vestibular schwannoma for patients with no signs of brainstem dysfunction.

Audiological results of endoscopic surgical repair of the long process of incus.

OBJECTIVE: The purpose of this study is to evaluate our experience with endoscopic repair of ossicular discontinuity at the incudostapedial joint, with or without an intact stapes suprastructure, and present our hearing results. We classify results based on the causative pathology, the type of ossiculoplasty, and type of lesion. We demonstrate the ability to endoscopically place a total ossicular replacement prosthesis (TORP), measuring 4.25 mm, between the stapes footplate and the incus remnant to reestablish ossicular continuity. METHODS: This was a retrospective case series conducted in tertiary referral center (Hopital de la Timone) Marseille, France. 25 patients underwent incudostapedial rebridging ossiculoplasty between 2009 and 2013. Fifteen cases of chronic otitis media and 10 otosclerosis revisions were included in the study. Three different materials were used in ossiculoplasty, hydroxyapatite cement, incus remnant, and partial/total ossicular replacement prostheses. Audiometric results were evaluated before and after ossiculoplasty. Twelve month follow-up data is provided. RESULTS: The mean postoperative air-bone gap was 15 dB (5-25 dB). Hearing results were better inotosclerosis revisions. Hydroxyapatite cement produced an air-bone gap of 5 dB, TORP placed under the incus produced a 12 dB gap, and TORP placed under the malleus resulted in a 12 dB gap and one deaf ear. In cases of chronic otitis media, the residual air-bone gap was 17 dB with PORP, 12 dB with TORP, and 20 dB with incus transposition. CONCLUSION: The hydroxyapatite cement is effective in the reconstruction of ossicular discontinuity but the high price limits its utilization. TORP placed under the incus is a reliable and stable method of ossicular reconstruction that is cost effective and offers satisfactory hearing results in selected patients.

Aberrant internal carotid artery in the temporal bone: imaging findings and management.

OBJECTIVES: To describe the clinical and radiological features of the vascular anomaly aberrant internal carotid artery (ICA) in the temporal bone and to discuss management strategies. DESIGN: Retrospective study. PATIENTS: Sixteen cases of aberrant ICA were diagnosed between 1982 and 2003. RESULTS: Of 16 cases, 11 were recognized by imaging assessment, 4 were recognized during middle ear surgery, and 1 was recognized clinically. Among the 11 cases, 8 malformations were diagnosed because of otologic symptoms related to the abnormal ICA or chronic otitis, while the other 3 were identified incidentally because of an underlying accompanying disease. In 4 cases, the diagnosis was made during surgery related to chronic otitis media (n = 2) or conductive hearing loss (n = 2). In these 4 cases, massive bleeding resulted from surgical injury to the vessel. Packing the external auditory canal and the middle ear first controlled the bleeding. Endovascular procedure was required in 2 cases to exclude an aneurysm or to control bleeding but was followed by anterior cerebral stroke in 1 case. The aberrant ICA could be identified on computed tomographic scan by the following features: intratympanic mass, enlarged inferior tympanic canaliculus, absence of the vertical segment of the ICA canal, and absence of bone covering the tympanic portion of the ICA. Conventional angiography was mandatory when intervention was planned to control bleeding or aneurysm. CONCLUSIONS: This study highlights that aberrant ICA has to be identified before any middle ear surgery because misdiagnosis may lead to dramatic surgical complications, whereas diagnosis with computed tomographic scan is easy. Bleeding is a minor complication compared with the putative neurologic deficit due to endovascular occlusion.

Functional outcome after gamma knife surgery or microsurgery for vestibular schwannomas.

OBJECT: Microsurgical excision is an established treatment for vestibular schwannoma (VS). In 1992 the authors used a patient questionnaire to evaluate the functional outcome and quality of life in a series of 224 consecutive patients. In addition, starting with gamma knife surgery (GKS) in 1992, the authors decided to use the same methodology to evaluate prospectively the results of this modality to compare the two alternatives. METHODS: Among the 500 patients who were included prospectively, the authors only evaluated patients in whom GKS was the primary treatment for unilateral VS. Four years of follow up was available for the first 104 consecutive patients. Statistical analysis of the GKS and microsurgery populations has shown that only a comparison of Stage II and III (according to the Koos classification) was meaningful in terms of group size and preoperative risk factor distribution. Objective results and questionnaire answers from the first 97 consecutive patients were compared with the 110 patients in the microsurgery group who fulfilled the inclusion criteria. Questionnaire answers indicated that 100% of patients who underwent GKS compared with 63% of patients who underwent microsurgery had no new facial motor disturbance. Forty-nine percent of patients who underwent GKS (17% in the microsurgery study) had no ocular symptoms, and 91% of patients treated with GKS (61% in the microsurgery study) had no functional deterioration after treatment. The mean hospitalization stay was 3 days after GKS and 23 days after microsurgery. All the patients who underwent GKS who had been employed, except one, had kept the same professional activity (56% in the microsurgery study). The mean time away from work was 7 days for GKS (130 days in the microsurgery study). Among patients whose preoperative hearing level was Class 1 according to the Gardner and Robertson scale, 70% preserved functional hearing after GKS (Class 1 or 2) compared with only 37.5% in the microsurgery group. CONCLUSIONS: Functional side effects happen during the first 2 years after radiosurgery. Findings after 4 years of follow up indicated that GKS provided better functional outcomes than microsurgery in this patient series.

Radiosurgery for vestibular schwannomas.

This article investigates the role of radiosurgery and stereotactic radiotherapy in the management of vestibular schwannomas (VS), reviewing the authors' own prospective cohort and the current literature. For patients with large Stage IV VS (according to the Koos classification), a combined approach with deliberate partial microsurgical removal followed by radiosurgery to the residual tumor is proposed. The authors' cohort is unique with respect to the size of the population and the length of the follow-up, and demonstrates the efficacy and safety of VS radiosurgery, with particular regard to its high rate of hearing preservation.

Longitudinal analysis of hearing before and after radiosurgery for vestibular schwannoma.

OBJECT: The aim of this study was to perform an accurate analysis of changes in hearing in patients with vestibular schwannoma (VS) who have undergone Gamma Knife surgery (GKS) and distinguish the impact of radiosurgery from the natural course of hearing deterioration due to the tumor itself. METHODS: This study was a retrospective review of prospectively collected patient data. A group of 154 patients with unilateral nonsurgically treated VS was conservatively monitored for more than 6 months and then treated with GKS between July 1997 and September 2005. They were followed up with serial clinical examination, MRI, and audiometry. The annual hearing decrease rate (AHDR) was measured before and after radiosurgery, and the possible prognostic factors for hearing preservation were investigated. RESULTS: The mean dose prescribed to the tumor margins was 12.1 Gy. The mean radiological follow-up period after GKS was 60 months (range 7-123 months). The tumor control rate was 94.8%, and 8 patients underwent subsequent intervention due to tumor progression. The mean audiological follow-up times before and after GKS were 22 and 52 months, respectively. The mean AHDRs before and after GKS were 5.39 dB/year (95% CI 3.31-7.47 dB/year) and 3.77 dB/year (95% CI 3.13-4.40 dB/year), respectively (p > 0.05). The mean pre- and post-GKS AHDRs in patients who initially had Gardner-Robertson (GR) Class I hearing were -0.57 dB/year (95% CI -2.95 to 1.81 dB/year) and 3.59 dB/year (95% CI 2.52-4.65 dB/year), respectively (p = 0.007). The mean pre- and post-GKS AHDRs in patients who initially had GR Class II hearing were 5.09 dB/year (95% CI 1.36-8.82 dB/year) and 4.98 dB/year (95% CI 3.86-6.10 dB/year), respectively (p > 0.05). A subgroup of 80 patients had both early and late post-intervention AHDR assessment (with early referring to the period from GKS to the assessment closest to the 2-year follow-up point and late referring to the period from that assessment to the most recent one); in these patients, the mean early post-GKS AHDR was 5.86 dB/year (95% CI 4.25-7.50 dB/year) and the mean late post-GKS AHDR was 1.86 dB/year (95% CI 0.77-2.96 dB/year) (p < 0.001). A maximum cochlear dose of less than 4 Gy was found to be the sole prognostic factor for hearing preservation. CONCLUSIONS: The present study demonstrated the absence of an increase in AHDR after radiosurgery as compared with the preoperative AHDR. There was even a trend indicating a reduction in the annual hearing loss after radiosurgery over the long term. To fully elucidate a possible protective effect of radiosurgery, longer-term follow-up with a larger group of patients will be required.

Wait-and-see strategy compared with proactive Gamma Knife surgery in patients with intracanalicular vestibular schwannomas.

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.

Repeat gamma knife surgery for regrowth of vestibular schwannomas.

OBJECTIVE: Gamma knife surgery (GKS) has become established as a minimally invasive treatment modality for patients with vestibular schwannomas. Treatment failure and/or tumor regrowth, however, is occasionally encountered, and microsurgical resection is usually warranted in such cases. The role of repeat GKS in these situations is still unclear. The goal of this study was to investigate whether repeat GKS is an effective treatment for recurrent vestibular schwannomas and to assess the conservation of residual neurological function. METHODS: Between July 1992 and December 2007, 1951 patients harboring a unilateral vestibular schwannoma were treated with GKS. Of these, 48 patients (2.5%) had to undergo a subsequent intervention because of progression or regrowth of the tumor. Repeat GKS was performed in a total of 15 patients, 8 of whom had more than 2 years of follow-up and were eligible to be enrolled in the present study. The median follow-up period after repeat GKS was 64 months, and the median interval between these interventions was 46 months. The median tumor volume was 0.51 and 1.28 mL at the initial and second GKS treatments, respectively. Patients received a median prescription dose of 12.0 Gy at both interventions. RESULTS: We report no cases of failure. Six patients demonstrated a significant reduction in tumor volume. In 1 patient, the final tumor volume was less than the initial volume. The other 2 patients showed stabilization of tumor growth. Useful hearing ability was preserved in only 1 of the 3 patients who had serviceable hearing ability at the time of the second GKS. Neither aggravation of facial nerve dysfunction nor other neurological deficits secondary to GKS were observed. CONCLUSION: This is the first report to address repeat GKS for vestibular schwannomas. After long-term follow-up, repeat GKS with a low marginal dose seems to be a safe and effective treatment in selected patients harboring regrowth of small vestibular schwannomas that have previously been treated with GKS.

Microsurgical removal of vestibular schwannomas after failed previous microsurgery.

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.

Translabyrinthine approach for vestibular schwannomas: operative technique.

For large vestibular schwannomas (VSs) for which removal is the primary therapy, the goals are complete tumor resection and maintenance of normal neurological function. The authors analyzed their results about facial nerve preservation, extent of resection and complications following resection of large VSs via a widened translabyrinthine approach. Between 1991 and 2001, 110 patients with a unilateral large VS (Koos stage IV) were operated on using the same technique in the same institution. The main steps of the operative technique were detailed and the clinical outcomes analyzed and compared with the results that were extracted from matched series in the literature. The main postoperative complications were cerebrospinal fluid leakage through the scalp wound in 4%, cerebrospinal fluid rhinorrhea in 4% requiring surgical revision in 3%. One percent of meningitis, 1% of posterior fossa hematoma and 4% of transient lower cranial nerve palsies were observed. There was no death related to the surgery. Total tumor removal was achieved in 85% of cases, near-total in 11% and subtotal in 4% of cases. Sixty-two percent of patients obtained normal to near-normal facial function (House-Brackmann grades 1 and 2). The authors suggest that the translabyrinthine approach is a suitable route for the safe removal of large VSs.

The wait and see strategy for intracanalicular vestibular schwannomas.

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.

Morphological changes of vestibular schwannomas after radiosurgical treatment: pitfalls and diagnosis of failure.

RATIONALE: Evaluate the morphological changes following radiosurgery in order to better define failure parameters. METHODS: 332 non-neurofibromatosis type 2 vestibular schwannomas not previously treated surgically or radiosurgically were subjected to Gamma Knife radiosurgery between 1992 and 2004 at the Gamma Knife Center in Marseille with at least three sequential MRI scans after radiosurgery. Five length measurements were systematically obtained. RESULTS: Mean follow-up was 4.6 years. Transient loss of contrast enhancement appeared in 213 patients (68%). Significant increase was present at 6 months in 178 patients. In 74 patients, the volume at 3 years was still higher than on the day of radiosurgery but remained stable. Failure occurred in 16 patients. Most showed progressive growth at all MRI controls after radiosurgery but late failure after initial response was possible. CONCLUSIONS: Sequential MRI scans after radiosurgery are necessary. A progressive and continuous growth at 3 years is essential to make diagnosis of failure.

Vestibular schwannomas: complications of microsurgery.

Current microsurgical treatment of vestibular schwannomas usually brings satisfactory results for the patients. However, transient or permanent complications may occur, especially when treating large tumors. Precise information about these potential complications has to be given to the patient at the time of the surgical decision. Based on their personal experience of large operated vestibular schwannomas and analyzing a review of the international literature, the authors detail these complications and the way to prevent and manage them. The problems that are linked to the variety of surgical approaches are also commented. The most frequent complication is cerebrospinal fluid leak that requires medical management and in less than one third of cases, surgical exploration. Vascular problems including ischemia or hemorrhage inside the posterior fossa represent the main source of permanent morbidity. Lower cranial nerve deficits are unusual but may expose to early and delayed aspiration pneumonias. The authors conclude that careful selection of cases, meticulous operative management and intensive postoperative care are essential steps to prevent and to treat these complications.

Recurrence of vestibular schwannomas after surgery.

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.

Hearing preservation in patients with unilateral vestibular schwannoma after gamma knife surgery.

INTRODUCTION: The majority of patients still lose the functionality of their hearing in spite of the technical advances in microsurgery. Our aim was to evaluate the hearing preservation potential of Gamma Knife Surgery. We have reviewed our experience and the literature in order to evaluate the probability to obtain such functional preservation and the factors influencing it. METHODS: Since July 1992, 2,053 patients have been operated on by Gamma Knife Radiosurgery in Timone University Hospital. This population included 184 unilateral schwannoma patients with functional preoperative hearing (Gardner-Robertson 1 or 2) treated by first intention radiosurgery with a marginal dose lower than 13 Gy. The population included 74 patients with subnormal hearing (class 1). All have been studied with a follow-up longer than 3 years. Univariate and multivariate analyses have been carried out. RESULTS: Numerous parameters greatly influence the probability of functional hearing preservation at 3 years, which is globally 60%. The main preoperative parameters of predictability are limited hearing loss that is Gardner-Robertson stage 1 (vs. 2), presence of tinnitus, young age of the patient and small size of the lesion. The functional hearing preservation at 3 years is 77.8% when the patient is initially in stage 1, 80% in patients with tinnitus as a first symptom and 95% when the patient has both. In these patients, the probability of functional preservation at 5 years is 84%. Comparison of these results with the main series of the literature confirms the reproducibility of our results. Additionally, we have demonstrated a higher chance of hearing preservation when the dose to the cochlea is lower than 4 Gy. CONCLUSION: We report a large population of patients treated by radiosurgery with functional preoperative hearing. These results demonstrate the possibility to preserve functional hearing in a high percentage of selected patients. Radiosurgery offers them a higher chance of functional hearing preservation than microsurgery or simple follow-up.