Outpatient gamma knife surgery for vestibular schwannoma: definition of the therapeutic profile based on a 10-year experience

Stereotactic radiosurgery as the primary management for patients with Koos grade IV vestibular schwannomas

OBJECTIVE

While extensive long-term outcome studies support the role of stereotactic radiosurgery (SRS) for smaller-volume vestibular schwannomas (VSs), its role in the management for larger-volume tumors remains controversial.

METHODS

Between 1987 and 2017, the authors performed single-session SRS on 170 patients with previously untreated Koos grade IV VSs (volumes ranged from 5 to 20 cm3). The median tumor volume was 7.4 cm3. The median maximum extracanalicular tumor diameter was 27.5 mm. All tumors compressed the middle cerebellar peduncle and distorted the fourth ventricle. Ninety-three patients were male, 77 were female, and the median age was 61 years. Sixty-two patients had serviceable hearing (Gardner-Robertson [GR] grades I and II). The median margin dose was 12.5 Gy.

RESULTS

At a median follow-up of 5.1 years, the progression-free survival rates of VSs treated with a margin dose ≥ 12.0 Gy were 98.4% at 3 years, 95.3% at 5 years, and 90.7% at 10 years. In contrast, the tumor control rate after delivery of a margin dose < 12.0 Gy was 76.9% at 3, 5, and 10 years. The hearing preservation rates in patients with serviceable hearing at the time of SRS were 58.1% at 3 years, 50.3% at 5 years, and 35.9% at 7 years. Younger age (< 60 years, p = 0.036) and initial GR grade I (p = 0.006) were associated with improved serviceable hearing preservation rate. Seven patients (4%) developed facial neuropathy during the follow-up interval. A smaller tumor volume (< 10 cm3, p = 0.002) and a lower margin dose (≤ 13.0 Gy, p < 0.001) were associated with preservation of facial nerve function. The probability of delayed facial neuropathy when the margin dose was ≤ 13.0 Gy was 1.1% at 10 years. Nine patients (5%) required a ventriculoperitoneal shunt because of delayed symptomatic hydrocephalus. Fifteen patients (9%) developed detectable trigeminal neuropathy. Delayed resection was performed in 4% of patients.

CONCLUSIONS

Even for larger-volume VSs, single-session SRS prevented the need for delayed resection in almost 90% at 10 years. For patients with minimal symptoms of tumor mass effect, SRS should be considered an effective alternative to surgery in most patients, especially those with advanced age or medical comorbidities.

Tumor Control Following Stereotactic Radiosurgery in Patients with Vestibular Schwannomas - A Retrospective Cohort Study

BACKGROUND

To better counsel vestibular schwannoma patients, it is necessary to understand the tumor control rates of stereotactic radiosurgery (SRS).

OBJECTIVES

To determine tumor control rates, factors determining control and complication rates following SRS.

METHODS

Tertiary hospital retrospective cohort.

RESULTS

579 tumors (576 patients) were treated with SRS. 477 tumors (474 patients, 82%) had ≥1 year follow up and 60% (344) ≥3 years follow up. 88% of tumors had primary SRS and 6.7% salvage SRS. Median follow up time was 4.6 years. At 3 years, the tumor control rate of primary SRS was 89% (258 of 290) in sporadic tumors compared to 43% in Neurofibromatosis type II (3 of 17) (p < 0.01). Our bivariable survival data analysis showed that Neurofibromatosis type II, documented pre-SRS growth, tumor measured by maximum dimension, SRS given as nonprimary treatment increased hazard of failure to control. There was one case of malignancy and another of rapid change following intra-tumoral hemorrhage. For tumors undergoing surgical salvage (25 of 59), 56% had a total or near-total resection, 16% had postoperative CSF leak, with 12% new facial paralysis (House-Brackmann grade VI) and worsening of facial nerve outcomes (House-Brackmann grade worse in 59% at 12 mo).

CONCLUSIONS

Control of vestibular schwannoma after primary SRS occurs in the large majority. Salvage surgical treatment was notable for higher rates of postoperative complications compared to primary surgery reported in the literature.

Clinical evaluation of a real-time inverse planning for Gamma Knife radiosurgery by convex optimization: a prospective comparative trial in a series of vestibular schwannoma patients

BACKGROUND

Gamma Knife radiosurgery (GKRS) inverse dose planning is currently far from competing effectively with the quality of dose planning developed by experienced experts. A new inverse planning (IP) method based on « efficient convex optimization algorithms » is proposed, providing high-quality dose plans in real time.

MATERIALS AND METHODS

Eighty-six patients treated by GKRS for vestibular schwannomas (VS) were recruited. The treatment plans created by the first author, who has 27 years of experience and has developed and delivered more than 15,000 dose plans, served as reference. A first set of basic constraints determined by default led the IP for an initial real-time dose plan. Additional constraints were interactively proposed by the planner to take other parameters into account. A second optimized plan was then calculated by the IP. The primary endpoint was the Paddick Conformity Index (PCI). The statistical analysis was planned on a non-inferiority trial design. Coverage, selectivity, and gradient indexes, dose at the organ(s) at risk, and 12 Gy isodose line volume were compared.

RESULTS

After a single run of the IP, the PCI was shown to be non-inferior to that of the "expert." For the expert and the IP, respectively, the median coverage index was 0.99 and 0.98, the median selectivity index 0.92 and 0.90, the median gradient index 2.95 and 2.84, the median dose at the modiolus of the cochlea 2.83 Gy and 2.86 Gy, the median number of shots 14.31 and 24.13, and the median beam-on time 46.20 min and 26.77 min. In a few specific cases, advanced tools of the IP were used to generate a second run by adding new constraints either globally (for higher selectivity) or locally, in order to increase or decrease these constraints focally.

CONCLUSION

These preliminary results showed that this new IP method based on « efficient convex optimization algorithms », called IntuitivePlan®, provided high-quality dose plans in real time with excellent coverage, selectivity, and gradient indexes with optimized beam-on time. If the new IP evaluated here is able to compete in real time with the quality of the treatment plans of an expert with extensive radiosurgical experience, this could allow new planners/radiosurgeons with limited or no experience to immediately provide patients with high-quality GKRS for benign and malignant lesions.

Stereotactic Radiosurgery for Vestibular Schwannomas: Tumor Control Probability Analyses and Recommended Reporting Standards

PURPOSE

We sought to investigate the tumor control probability (TCP) of vestibular schwannomas after single-fraction stereotactic radiosurgery (SRS) or hypofractionated SRS over 2 to 5 fractions (fSRS).

METHODS AND MATERIALS

Studies (PubMed indexed from 1993-2017) were eligible for data extraction if they contained dosimetric details of SRS/fSRS correlated with local tumor control. The rate of tumor control at 5 years (or at 3 years if 5-year data were not available) were collated. Poisson modeling estimated the TCP per equivalent dose in 2 Gy per fraction (EQD2) and in 1, 3, and 5 fractions.

RESULTS

Data were extracted from 35 publications containing a total of 5162 patients. TCP modeling was limited by the absence of analyzable data of <11 Gy in a single-fraction, variability in definition of "tumor control," and by lack of significant increase in TCP for doses >12 Gy. Using linear-quadratic-based dose conversion, the 3- to 5-year TCP was estimated at 95% at an EQD2 of 25 Gy, corresponding to 1-, 3-, and 5-fraction doses of 13.8 Gy, 19.2 Gy, and 21.5 Gy, respectively. Single-fraction doses of 10 Gy, 11 Gy, 12 Gy, and 13 Gy predicted a TCP of 85.0%, 88.4%, 91.2%, and 93.5%, respectively. For fSRS, 18 Gy in 3 fractions (EQD2 of 23.0 Gy) and 25 Gy in 5 fractions (EQD2 of 30.2 Gy) corresponded to TCP of 93.6% and 97.2%. Overall, the quality of dosimetric reporting was poor; recommended reporting guidelines are presented.

CONCLUSIONS

With current typical SRS doses of 12 Gy in 1 fraction, 18 Gy in 3 fractions, and 25 Gy in 5 fractions, 3- to 5-year TCP exceeds 91%. To improve pooled data analyses to optimize treatment outcomes for patients with vestibular schwannoma, future reports of SRS should include complete dosimetric details with well-defined tumor control and toxicity endpoints.

Is There a Need for a 6-Month Postradiosurgery Magnetic Resonance Imaging in the Treatment of Vestibular Schwannoma?

BACKGROUND

Stereotactic radiosurgery (SRS) is a common treatment modality for vestibular schwannoma (VS), with a role in primary and recurrent/progressive algorithms. At our institution, routine magnetic resonance imaging (MRI) is obtained at 6 and 12 mo following SRS for VS.

OBJECTIVE

To analyze the safety and financial impact of eliminating the 6-mo post-SRS MRI in asymptomatic VS patients.

METHODS

A prospectively maintained SRS database was retrospectively reviewed for VS patients with 1 yr of post-treatment follow-up, 2005 to 2015. Decisions at 6-mo MRI were binarily categorized as routine follow-up vs clinical action-defined as a clinical visit, additional imaging, or an operation as a direct result of the 6-mo study.

RESULTS

A total of 296 patients met screening criteria, of whom 53 were excluded for incomplete follow-up and 8 for NF-2. Nine were reimaged prior to 6 mo due to clinical symptoms. Routine 6-mo post-SRS MRI was completed by 226 patients (76% of screened cohort), following from which zero instances of clinical action occurred. When scaled using national insurance database-derived financials-which estimated the mean per-study charge for MRI of the brain with and without contrast at $1767-the potential annualized national charge reduction was approximated as $1 611 504.

CONCLUSION

For clinically stable VS, 6-mo post-SRS MRI does not contribute significantly to management. We recommend omitting routine MRI before 12 mo, in patients without new or progressive neurological symptoms. If extrapolated nationally to the more than 100 active SRS centers, thousands of patients would be spared an inconvenient, nonindicated study, and national savings in health care dollars would be on the order of millions annually.

Temporal Dynamics of Pseudoprogression After Gamma Knife Radiosurgery for Vestibular Schwannomas-A Retrospective Volumetric Study

BACKGROUND

The optimal observation interval after the radiosurgical treatment of a sporadic vestibular schwannoma, prior to salvage intervention, is unknown.

OBJECTIVE

To determine an optimal postradiosurgical treatment interval for differentiating between pseudoprogression and true tumor growth by analyzing serial volumetric data.

METHODS

This single-institution retrospective study included all sporadic vestibular schwannomas treated with Gamma Knife radiosurgery (Eketa AB, Stockholm, Sweden; 12-13 Gy) from 2002 to 2014. Volumetric analysis was performed on all available pre- and posttreatment magnetic resonance imaging scans. Tumors were classified as "stable/decreasing," "transient enlargement", or "persistent growth" after treatment, based on incrementally increasing follow-up durations.

RESULTS

A total of 118 patients included in the study had a median treatment tumor volume of 0.74 cm3 (interquartile range [IQR] = 0.34-1.77 cm3) and a median follow-up of 4.1 yr (IQR = 2.6-6.0 yr). Transient tumor enlargement was observed in 44% of patients, beginning at a median of 1 yr (IQR = 0.6-1.4 yr) posttreatment, with 90% reaching peak volume within 3.5 yr, posttreatment. Volumetric enlargement resolved at a median of 2.4 yr (IQR 1.9-3.6 yr), with 90% of cases resolved at 6.9 yr. Increasing follow-up revealed that many of the tumors initially enlarging 1 to 3 yr after stereotactic radiosurgery ultimately begin to shrink on longer follow-up (45% by 4 yr, 77% by 6 yr).

CONCLUSION

Tumor enlargement within ∼3.5 yr of treatment should not be used as a sole criterion for salvage treatment. Patient symptoms and tumor size must be considered, and giving tumors a chance to regress before opting for salvage treatment may be worthwhile.

Comparing Outcomes Following Salvage Microsurgery in Vestibular Schwannoma Patients Failing Gamma-knife Radiosurgery or Microsurgery

OBJECTIVE

The increasing use of primary gamma-knife radiosurgery (GKS) for the treatment of vestibular schwannoma (VS) has led to a concomitant increase in the number of patients requiring salvage surgery for GKS failure. When patients underwent GKS as the primary treatment, it is known that dissecting tumor from adjacent nerves during salvage surgery is more difficult. In this report, we share our clinical experience with such patients and analyze the clinical findings of patients with tumor regrowth/recurrence.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary center.

PATIENTS

Nine patients who underwent salvage surgery for VS regrowth/recurrence after GKS or microsurgery were enrolled.

MAIN OUTCOME MEASURES

Symptom progression, radiological changes, intraoperative findings, and surgical outcomes were evaluated and compared.

RESULTS

Six patients with previous GKS and three with previous microsurgery underwent salvage microsurgery. The most obvious symptom of tumor regrowth was aggravation of hearing loss. Salvage surgery in all patients was limited to subtotal or near-total resection via a translabyrinthine/transotic approach. Severe adhesion, thickening, and fibrosis were more prominent findings in the GKS than in the previous microsurgery group. Dissection of the tumor from the facial nerve was more difficult in the GKS than in the microsurgery patients. Despite anatomical preservation of the facial nerve in all the six patients, three in the GKS group, but none in the revision microsurgery group, had worsening of facial nerve function.

CONCLUSION

Salvage microsurgery of VS after failed GKS is more difficult than revision microsurgery, and the facial nerve outcomes are relatively poor. Therefore, the primary method of VS treatment should be carefully chosen. Additional imaging studies are recommended in patients with a sudden change in hearing loss who underwent GKS.

Inhibition of c-Jun N-terminal kinase activity enhances vestibular schwannoma cell sensitivity to gamma irradiation

BACKGROUND

Radiosurgery is increasingly used to treat vestibular schwannomas (VSs). Increasing the sensitivity of VS cells to irradiation (IR) could allow for lower and/or more effective doses of IR, improving safety and efficacy. Persistent c-Jun N-terminal kinase (JNK) activity in VS cells reduces cell death by suppressing the accumulation of reactive oxygen species (ROS), raising the possibility that JNK activity protects against IR-induced VS cell death, which is mediated by ROS.

OBJECTIVE

To determine the extent to which JNK signaling contributes to VS cell radiosensitivity.

METHODS

Primary human VS cultures, derived from acutely resected tumors, received single doses (5-40 Gy) of gamma irradiation. Histone 2AX phosphorylation, a marker of IR-induced DNA damage, was assayed by Western blot and immunostaining. ROS levels were quantified by measuring 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) fluorescence. Cell apoptosis was determined by terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling.

RESULTS

The JNK inhibitors SP6000125 and I-JIP reduced histone 2AX phosphorylation after IR. They also increased H2DCFDA fluorescence in nonirradiated cultures and significantly increased IR-induced (5-10 Gy) H2DCFDA fluorescence 72 hours, but not 2 hours, after IR. Finally, I-JIP (50 μmol/L) significantly increased VS cell apoptosis in cultures treated with 20 to 40 Gy. I-JIP (20 μmol/L), SP600125 (20 μmol/L), and JNK1/2 short interfering RNA knockdown each increased VS cell apoptosis in cultures treated with 30 to 40 Gy, but not lower doses, of IR.

CONCLUSION

Inhibition of JNK signaling decreases histone 2AX phosphorylation and increases ROS and apoptosis in VS cells after gamma irradiation. These results raise the possibility of using JNK inhibitors to increase the effectiveness of radiosurgery for treatment of VSs.

An update on unilateral sporadic small vestibular schwannoma

Advances in neuroimaging have increased the detection rate of small vestibular schwannomas (VSs, maximum diameter < 25 mm). Current management modalities include observation with serial imaging, stereotactic radiosurgery, and microsurgical resection. Selecting one approach over another invites speculation, and no standard management consensus has been established. Moreover, there is a distinct clinical heterogeneity among patients harboring small VSs, making standardization of management difficult. The aim of this article is to guide treating physicians toward the most plausible therapeutic option based on etiopathogenesis and the highest level of existing evidence specific to the different cohorts of hypothetical case scenarios. Hypothetical cases were created to represent 5 commonly encountered scenarios involving patients with sporadic unilateral small VSs, and the literature was reviewed with a focus on small VS. The authors extrapolated from the data to the hypothetical case scenarios, and based on the level of evidence, they discuss the most suitable patient-specific treatment strategies. They conclude that observation and imaging, stereotactic radiosurgery, and microsurgery are all important components of the management strategy. Each has unique advantages and disadvantages best suited to certain clinical scenarios. The treatment of small VS should always be tailored to the clinical, personal, and social requirements of an individual patient, and a rigid treatment protocol is not practical.

Multisession stereotactic radiosurgery for vestibular schwannomas: single-institution experience with 383 cases

BACKGROUND

Single-session stereotactic radiosurgery (SRS) treatment of vestibular schwannomas results in excellent tumor control. It is not known whether functional outcomes can be improved by fractionating the treatment over multiple sessions.

OBJECTIVE

To examine tumor control and complication rates after multisession SRS.

METHODS

Three hundred eighty-three patients treated with SRS from 1999 to 2007 at Stanford University Medical Center were retrospectively reviewed. Ninety percent were treated with 18 Gy in 3 sessions, targeting a median tumor volume of 1.1 cm3 (range, 0.02-19.8 cm3).

RESULTS

During a median follow-up duration of 3.6 years (range, 1-10 years), 10 tumors required additional treatment, resulting in 3- and 5-year Kaplan-Meier tumor control rates of 99% and 96%, respectively. Five-year tumor control rate was 98% for tumors < 3.4 cm3. Neurofibromatosis type 2-associated tumors were associated with worse tumor control (P = .02). Of the 200 evaluable patients with pre-SRS serviceable hearing (Gardner-Robertson grade 1 and 2), the crude rate of serviceable hearing preservation was 76%. Smaller tumor volume was associated with hearing preservation (P = .001). There was no case of post-SRS facial weakness. Eight patients (2%) developed trigeminal dysfunction, half of which was transient.

CONCLUSION

Multisession SRS treatment of vestibular schwannomas results in an excellent rate of tumor control. The hearing, trigeminal nerve, and facial nerve function preservation rates reported here are promising.

Non-audiofacial morbidity after Gamma Knife surgery for vestibular schwannoma

OBJECT

While many studies have been published outlining morbidity following radiosurgical treatment of vestibular schwannomas, significant interpractitioner and institutional variability still exists. For this reason, the authors conducted a systematic review of the literature for non-audiofacial-related morbidity after the treatment of vestibular schwannoma with radiosurgery.

METHODS

The authors performed a comprehensive search of the English-language literature to identify studies that published outcome data of patients undergoing radiosurgery treatment for vestibular schwannomas. In total, 254 articles were found that described more than 50,000 patients and were analyzed for satisfying the authors' inclusion criteria. Patients from these studies were then separated into 2 cohorts based on the marginal dose of radiation: < or = 13 Gy and > 13 Gy. All tumors included in this study were < 25 mm in their largest diameter.

RESULTS

A total of 63 articles met the criteria of the established search protocol, which combined for a total of 5631 patients. Patients receiving > 13 Gy were significantly more likely to develop trigeminal nerve neuropathy than those receiving < 13 Gy (p < 0.001). While we found no relationship between radiation dose and the rate of developing hydrocephalus (0.6% for both cohorts), patients with hydrocephalus who received doses > 13 Gy appeared to have a higher rate of symptomatic hydrocephalus requiring shunt treatment (96% [> 13 Gy] vs 56% [< or = 13 Gy], p < 0.001). The rates of vertigo or balance disturbance (1.1% [> 13 Gy] vs 1.8% [< or = 13 Gy], p = 0.001) and tinnitus (0.1% [> 13 Gy] vs 0.7% [< or = 13 Gy], p = 0.001) were significantly higher in the lower dose cohort than those in the higher dose cohort.

CONCLUSIONS

The results of our review of the literature provide a systematic summary of the published rates of nonaudiofacial morbidity following radiosurgery for vestibular schwannoma.

GAMMA KNIFE RADIOSURGERY IN YOUNGER PATIENTS WITH VESTIBULAR SCHWANNOMAS

OBJECTIVE

Management options for patients with vestibular schwannoma include observation, surgical resection, stereotactic radiosurgery (SRS), and stereotactic radiation therapy. In younger patients, resection is often advocated because of concern regarding the long-term effects of radiation. We studied tumor response and clinical outcomes after SRS in such patients.

METHODS

We reviewed long-term outcomes in 55 patients with vestibular schwannomas. Patients were 40 years of age or younger, underwent gamma knife (GK) SRS between 1987 and 2003, and were followed up for a minimum of 4 years. The median patient age was 35 years (range, 13–40 years). Forty-one patients had Gardner-Robertson class 1 to 4 hearing. Thirteen patients (24%) had undergone surgical removal. The median tumor volume was 1.7 mm3. The median tumor margin dose was 13.0 Gy (range, 11–20 Gy).

RESULTS

At a median of 5.3 years, (range, 4–20 years), 2 of 55 patients underwent GK SRS for a second time; 1 of these patients had had a recurrence after initial resection. The 5-year rate of freedom from additional management was 96%. Hearing preservation rates (i.e., remaining within the same Gardner-Robertson hearing class) were 93%, 87%, and 87% at 3, 5, and 10 years, respectively. In patients with serviceable hearing before SRS, it was maintained in 100%, 93%, and 93% of patients at 3, 5, and 10 years, respectively. Hearing preservation was related to a margin dose lower than 13 Gy (P = 0.017). At the last assessment, facial and trigeminal nerve function was preserved in 98.2% and 96.4% of patients, respectively; the only facial deficit (House-Brackmann grade III) occurred in a patient who received a tumor dose of 20 Gy early in our experience (1988). None of the patients treated with doses lower than 13 Gy experienced facial or trigeminal neuropathy. All patients continued their previous level of activity or employment after GK SRS. No patient developed a secondary radiation-related tumor.

CONCLUSION

Our experience indicates that GK SRS is an effective management strategy for younger patients with vestibular schwannoma, most of whom have no additional cranial nerve dysfunction.

Vestibular schwannoma: surgery or gamma knife radiosurgery? A prospective, nonrandomized study

OBJECTIVE

To conduct a prospective, open, nonrandomized study of treatment-associated morbidity in patients undergoing microsurgery or gamma knife radiosurgery (GKRS) for vestibular schwannomas.

METHODS

Ninety-one patients with vestibular schwannomas with a maximum tumor diameter of 25 mm in the cerebellopontine angle were treated according to a prospective protocol either by GKRS (63 patients) or open microsurgery (28 patients) using the suboccipital approach. Primary end points included hearing function, according to the Gardner-Robertson scale, and facial nerve function, according to the House-Brackmann scale at 2 years. Clinical data included a balance platform test, score for tinnitus and vertigo using a visual analog scale, and working ability. Patients responded to the quality-of-life questionnaires Short-Form 36 and Glasgow Benefit Inventory.

RESULTS

Three elderly GKRS patients withdrew; all remaining patients were followed for 2 years. Both primary end points were highly significant in favor of GKRS (P < 0.001). Evidence of reduced facial nerve function (House-Brackmann grade 2 or poorer) at 2 years was found in 13 of 28 open microsurgery patients and 1 of 60 GKRS patients. Thirteen of 28 patients who underwent surgery had serviceable hearing (Gardner-Robertson grade A or B) preoperatively, but none had serviceable hearing postoperatively. Twenty-five of 60 GKRS patients had serviceable hearing before treatment, and 17 (68%) of them had serviceable hearing 2 years after treatment. The tinnitus and vertigo visual analog scale score, as well as balance platform tests, did not change significantly after treatment, and working status did not differ between the groups at 2 years. Quality of life was significantly better in the GKRS group at 2 years, based on the Glasgow Benefit Inventory questionnaire. One GKRS patient required operative treatment within the 2-year study period.

CONCLUSION

This is the second prospective study to demonstrate better facial nerve and hearing outcomes from GKRS than from open surgery for small- and medium-sized vestibular schwannomas.

Repeated treatment of vestibular schwannomas after gamma knife radiosurgery

PURPOSE

When gamma knife radiosurgery (GKS) does not achieve control of the growth of a tumour, the need to repeat treatment is considered. The results and risks of repeat treatment of patients with a vestibular schwannoma were reviewed to assess its efficacy and safety.

METHODS

Between 1992 and 2001, we treated 351 patients with a vestibular schwannoma by GKS, control of the growth of the tumour was not achieved in 32. 26 patients underwntrepeat GKS and five patients had an open microsurgical operation and one stereotactic aspiration of a tumour cyst.

RESULTS

Twenty-four of 26 patients were followed up after the repeat GKS for a median of 43 months. 15 tumours became smaller, seven remained unchanged and two enlarged. After the second GKS one patient's hearing deteriorated, one developed facial weakness and three facial spasms. One patient required insertion of ventriculo-peritoneal drainage. An operation to radically resect the tumour was performed in five patients after the first GKS and for a subtotal removal in one after repeated GKS.

CONCLUSIONS

In the small proportion of patients (9%) in whom initial GKS does not control the growth of a vestibular schwannoma, most can be controlled by further GKS with a very low risk of a complications.

Transient expansion of vestibular schwannoma following stereotactic radiosurgery

OBJECT

The authors prospectively analyzed volume changes in vestibular schwannomas (VSs) after stereotactic radiosurgery.

METHODS

One hundred consecutive patients with unilateral VS treated with Gamma Knife surgery (GKS) at Chiba Cardiovascular Center between 1998 and 2006 were analyzed in this study. For each lesion the Gd-enhanced volume was measured serially every 3 months in the 1st year, then every 6 months thereafter, using volumetric software. The frequency and degree of transient tumor expansion were documented and possible prognostic factors were analyzed. Concurrently, neurological deterioration involving trigeminal, facial, and cochlear nerve functions were also assessed.

RESULTS

The mean observation period was 65 months (range 25-100 months). There were 32 men and 68 women, whose mean age was 59.1 years (range 29-80 years). Tumor volumes at GKS averaged 2.7 cm3 (range 0.1-13.2 cm3), and the lesions were irradiated at the mean 52.2% isodose line for the tumor margin (range 50-67%), with a mean dose of 12.2 Gy (range 10.5-13 Gy) at the periphery. The tumor volume was increased by 23% at 3 months and 27% at 6 months. Tumors shrank to their initial size over a mean period of 12 months. The maximum volume increase was < 10% (no significant increase) in 26 patients, 10-30% in 23, 30-50% in 22, 50-100% in 16, and > 100% in 13. The peak tumor expansion averaged 47% (range 0-613%). A high-dose (> or = 3.5 Gy/min) treatment appears to be the greatest risk factor for transient tumor expansion, although the difference did not reach statistical significance. Transient facial palsy and facial dysesthesia correlated strongly with tumor expansion, but only half of the hearing loss was coincident with this phenomenon.

CONCLUSIONS

Transient expansion of VSs after GKS was found to be much more frequent than previously reported, strongly suggesting a correlation with deterioration of facial and trigeminal nerve functions.

Tumor-volume changes after radiosurgery for vestibular schwannoma: implications for follow-up MR imaging protocol

BACKGROUND AND PURPOSE

The outcome of radiosurgery for vestibular schwannoma (VS) is assessed by posttreatment measurement of tumor size and could be influenced by the timing and quality of the assessment. This study evaluates the volumetric changes of VS after radiosurgery and proposes a radiologic follow-up program.

MATERIALS AND METHODS

Of 142 patients with VS treated with radiosurgery, we selected patients who were followed at least 3 times during a minimum of 32 months with a T1-weighted gadolinium-enhanced high-resolution 3D MR imaging examination identical to the pretreatment MR imaging. Forty-five patients were identified with a mean follow-up of 50 months (range, 32-78 months). Pre- and posttreatment tumor volumes were calculated by using BrainSCAN software by manually contouring tumors on each MR imaging study. Volume changes of >13% were defined as events.

RESULTS

At last follow-up MR imaging, volumes were smaller in 37 (82.2%) of the 45 patients. Eleven (29.7%) of these 37 tumors showed transient swelling preceding regression, with a median time to regression of 34 months (range, 20-55 months). Seven (15.6%) of the 45 tumors had volume progression compared with the tumor on pretreatment MR imaging studies. Of these 7 tumors, 3, however, had volume regression compared with the preceding MR imaging study, and in 4, volume progression was ongoing. One tumor remained the same.

CONCLUSIONS

Tumor-volume measurements by standardized T1-weighted gadolinium-enhanced high-resolution 3D MR imaging follow-up protocols revealed good local control of VS after radiosurgery. The first-follow-up MR imaging at 2 years and the second at 5 years postradiosurgery differentiated transient progression from ongoing progression and may prevent unnecessary therapeutic interventions.

Treatment of vestibular schwannomas. Why, when and how?

Sporadic vestibular schwannoma (VS) causes unilateral hearing loss, tinnitus, vertigo and unsteadiness. In many cases, the tumour size may remain unchanged for many years following diagnosis, which is typically made by MRI. In the majority of cases the tumour is small, leaving the clinician and patient with the options of either serial scanning or active treatment by gamma knife radiosurgery (GKR) or microneurosurgery. Despite the vast number of published treatment reports, comparative studies are few, and evidence is no better than class III (May, 2006). The predominant clinical endpoints of VS treatment include tumour control, facial nerve function and hearing preservation. Less focus has been put on symptom relief and health-related quality of life (QOL). It is uncertain if treating a small tumour leaves the patient with a better chance of obtaining relief from future hearing loss, vertigo or tinnitus than by observing it without treatment. Recent data indicate that QOL is reduced in untreated VS patients, and may differ between patients who have been operated and patients treated with GKR. In the present paper we review the natural course and complaints of untreated VS patients, and the treatment alternatives and results. Furthermore, we review the literature concerning quality of life in patients with VS. Finally, we present our experience with a management strategy applied to more than 300 cases since 2001.

Intracochlear Hemorrhage After Gamma Knife Radiosurgery

PURPOSE

To describe an acute complication after gamma knife stereotactic radiosurgery (GKRS) for vestibular schwannoma (VS) in a neurofibromatosis type 2 (NF2) patient.

STUDY DESIGN

Case report.

SETTING

Tertiary care center.

PATIENT

A 20-year-old man, who had bilateral VS and was having right-sided profound deafness, underwent GKRS for a 2-cm left-sided VS in an attempt to preserve his only hearing ear. He received a margin dose of 13 Gy to the 50% isodose line. Twenty-four hours after treatment, he presented with spinning vertigo, left-sided dead ear, and ipsilateral mild facial paralysis (House-Brackmann grade 3).

RESULTS

Magnetic resonance imaging demonstrated an intracochlear hemorrhage at the level of the basal turn of the left cochlea. Hearing did not recover, and the patient had to resort to lip reading. The facial paralysis regressed completely after 3 months.

CONCLUSION

Many cases of hemorrhage caused by GKRS have previously been reported, but all were related to meningiomas or brain metastases. Because the patient had no coagulation defect, sign of trauma, or any history of infection, the hemorrhage might have been caused by a direct thermal effect on the endothelial cells or to an immediate tumoral swelling, inducing an increase in intravascular outflow resistance and leading to venous obliteration. To our knowledge, this is the first report of acute intracochlear hemorrhage after GKRS for VS.

Controversies in building a management algorithm for vestibular schwannomas

PURPOSE OF REVIEW

The present review examines the various mainstream treatment options, benefits and risks, and controversies involved in developing a management algorithm for treatment of vestibular schwannoma.

RECENT FINDINGS

Advances in microsurgery and radiosurgery have made tremendous contributions to management of vestibular schwannoma; however, considerable controversy still exists. The auditory and facial nerve functional outcomes have improved with use of intraoperative monitoring for vestibular schwannoma removal and with lower radiosurgery doses; however, risks to the facial and auditory nerves still exist. Observing vestibular schwannomas for growth with serial magnetic resonance imaging is an increasingly popular option for small vestibular schwannomas that allows patients to enjoy hearing and facial function.

SUMMARY

The risks and benefits of each treatment option must be weighed for each patient, and management decisions regarding vestibular schwannomas should be individualized for each patient depending on tumor anatomy, patient preferences, and symptoms.

Evaluation of Tumor Expansion after Stereotactic Radiosurgery in Patients Harboring Vestibular Schwannomas

OBJECTIVE:

Stereotactic radiosurgery has been accepted as a safe and effective treatment in patients harboring a vestibular schwannoma. However, during follow-up, tumor expansion induced by high-dose irradiation can occur. Tumor expansion is more likely to be transient, but this phenomenon causes some confusion regarding whether further treatment should be performed. Our purpose was to clarify what type of tumor expansion requires additional treatment.

METHODS:

Between May 1991 and December 1998, 346 patients with a vestibular schwannoma, excluding two with neurofibromatosis, were treated using gamma knife radiosurgery. Of these, serial follow-up images to evaluate tumor expansion were available for 254 patients. Tumor expansion was classified into three types: central necrosis (Type A), solid expansion (Type B), and cyst enlargement or formation (Type C).

RESULTS:

Forty-two patients (17%) had tumor expansion during follow-up. Seventeen patients required additional treatment and 25 did not have any treatments after gamma knife radiosurgery. Type A, B, and C expansion was found in 14, 16, and 12 patients, respectively. Of these, three Type A patients, seven Type B patients, and seven Type C patients underwent salvage treatments. All patients in whom cyst formation developed eventually required craniotomy.

CONCLUSION:

Although tumor expansion was more likely to be transient, additional treatments should be considered in patients who experience neurological deterioration. We strongly recommend simply waiting and obtaining frequent follow-up images until the patients experience neurological deterioration, even when tumor expansion is developing, excluding cyst formation, which tends to continue.