Radiosurgery: a minimally interventional alternative to microsurgery in the management of acoustic neuroma

Cost analysis of vestibular schwannoma screening with contrast-enhanced magnetic resonance imaging in patients with asymmetrical hearing loss

BACKGROUND

Vestibular schwannomas are a rare cause of asymmetrical hearing loss, and routine screening with magnetic resonance imaging can be costly. This paper reports results on vestibular schwannoma screening at our institution and compares the cost of screening to a utility of hearing benefit.

METHOD

All screening examinations with magnetic resonance imaging performed for asymmetrical hearing loss between 2006 and 2011 were retrospectively reviewed. The cost per new vestibular schwannoma diagnosis was calculated. The cost per patient for those who benefitted from intervention was estimated based on rates of hearing preservation reported in the literature.

RESULTS

Forty-five (4.3 per cent) of 1050 screening examinations with magnetic resonance imaging performed for asymmetrical hearing loss were positive for vestibular schwannoma, and the cost per new diagnosis was $11,436. The estimated screening cost per patient for those who benefitted from surgery or radiation was $147,030, while US federal compensation for unilateral hearing loss was $44,888.

CONCLUSION

Although we achieved a lower screening cost per new diagnosis than reported in the current literature, there remains disparity between the screening cost per benefitted patient and the 'benefit' of hearing.

Long-term outcome of gamma knife radiosurgery for vestibular schwannoma

Objective We evaluated the long-term outcome of vestibular schwannoma (VS) treated with gamma knife radiosurgery (GKRS) as a primary treatment as well as an adjunct therapy. Materials and Methods We performed a retrospective review (2000-2012) of 82 patients with VS who received GKRS. Of 82 patients, 20 patients with prior resection received GKRS treatment as an adjunct therapy. The remainder of the patients (62) received GKRS as a primary treatment. Results GKRS for VS showed significant variations in tumor growth control (decreased in 44 patients [54%], arrested growth in 30 patients [36%], and increased tumor size in 8 patients [10%]). Progression-free survival rates after GKRS at 3, 5, and 10 years were 98%, 95%, and 95%, respectively. Hearing, facial nerve function, and Karnofsky performance scale were significantly improved after GKRS compared with pretreated status (79 versus 90). Two patients (2.5%) required resection again due to tumor progression and worsening of signs and symptoms. Conclusion Long-term follow-up demonstrated that GKRS offers a high rate of tumor control, preservation of multiple nerve functions, and a good quality of life in both new and recurrent patients with VS.

The impact of comorbidities, regional trends, and hospital factors on discharge dispositions and hospital costs after acoustic neuroma microsurgery: a United States nationwide inpatient data sample study (2005-2009)

OBJECT

Hospitalization cost and patient outcome after acoustic neuroma surgery depend on several factors. There is a paucity of data regarding the relationship between demographic features such as age, sex, race, insurance status, and patient outcome. Apart from demographic factors, there are several hospital-related factors and regional issues that can affect outcomes and hospital costs. To the authors' knowledge, no study has investigated the issue of regional disparity across the country in terms of cost of hospitalization and discharge disposition.

METHODS

The authors analyzed the Nationwide Inpatient Sample (NIS) database over the years 2005-2009. Several variables were analyzed from the database, including patient demographics, comorbidities, and surgical complications. Hospital variables, such as bedsize, rural/urban location, teaching status, federal or private ownership, and the region, were also examined. Patient outcome and increased hospitalization costs were the dependent variables studied.

RESULTS

A total of 2589 admissions from 242 hospitals were analyzed from the NIS data over the years 2005-2009. The mean age was 48.99 ± 13.861 years (± SD), and 304 (11.7%) of the patients were older than 65 years. The cumulative cost incurred by the hospitals from 2005 to 2009 was $948.77 million. The mean expenditure per admission was $76,365.09 ± $58,039.93. The mean total charges per admission rose from $59,633.00 in 2005 to $97,370.00 in 2009. The factors that predicted most significantly with other than routine (OTR) disposition outcome were age older than 65 years (OR 2.22, 95% CI 1.411-3.518; p < 0.001), aspiration pneumonia (OR 16.085, 95% CI 4.974-52.016; p < 0.001), and meningitis (OR 11.299, 95% CI 3.126-40.840; p < 0.001). When compared with patients with Medicare and Medicaid, patients with private insurance had a protective effect against OTR disposition outcome. Higher comorbidities predicted independently for OTR disposition outcome (OR 1.409, 95% CI 1.072-1.852; p = 0.014). The West region predicted negatively for OTR disposition outcome. Large hospitals were independently associated with higher hospital charges (OR 4.269, 95% CI 3.106-5.867; p < 0.001). The West region had significantly higher (p < 0.001) mean hospital charges than the other regions. Patient factors such as meningitis and aspiration pneumonia were strong independent predictors of increased hospital charges (p < 0.001). Higher comorbidities (OR 1.297, 95% CI 1.036-1.624; p = 0.023) and presence of neurofibromatosis Type 2 (OR 2.341, 95% CI 1.479-3.707; p < 0.001) were associated with higher hospital charges.

CONCLUSIONS

The authors' study shows that several factors can affect patient outcome and hospital charges for patients who have undergone acoustic neuroma surgery. Factors such as younger age, higher ZIP code income, less comorbidity, private insurance, elective surgery, and the West region predicted for better disposition outcome. However, the West region, higher comorbidities, and weekend admissions were associated with higher hospitalization costs.

Therapeutic profile of single-fraction radiosurgery of vestibular schwannoma: unrelated malignancy predicts tumor control

Radiosurgery has become an accepted treatment option for vestibular schwannomas. Nevertheless, predictors of tumor control and treatment toxicity in current radiosurgery of vestibular schwannomas are not well understood. To generate new information on predictors of tumor control and cranial nerve toxicity of single-fraction radiosurgery of vestibular schwannomas, we conducted a single-institution long-term observational study of radiosurgery for sporadic vestibular schwannomas. Minimum follow-up was 3 years. Investigated as potential predictors of tumor control and cranial nerve toxicity were treatment technology; tumor resection preceding radiosurgery; tumor size; gender; patient age; history of cancer, vascular disease, or metabolic disease; tumor volume; radiosurgical prescription dose; and isodose line. Three hundred eighty-six patients met inclusion criteria. Treatment failure was observed in 27 patients. History of unrelated cancer (strongest predictor) and prescription dose significantly predicted tumor control. The cumulative incidence of treatment failure was 30% after 6.5 years in patients with unrelated malignancy and 10% after ≥15 years in patients without such cancer (P < .02). Tumor volume was the only predictor of trigeminal neuropathy (observed in 6 patients). No predictor of facial nerve toxicity was found. On the House and Brackmann scale, 1 patient had a permanent one-level drop and 7 a transient drop of 1 to 3 levels. Serviceable hearing was preserved in 75.1%. Tumor hearing before radiosurgery, recurrence, and prescription isodose predicted ototoxicity. Unrelated malignancy is a strong predictor of tumor control. Tumor recurrence predominantly predicts ototoxicity. These findings potentially will aid future clinical decision making in ambiguous cases.

Magnetic resonance imaging dynamics of contrast medium uptake in vestibular schwannomas

OBJECT

Efficacy of radiosurgery in vestibular schwannoma (VS) is usually documented by changes of tumor size and by loss of contrast enhancement in MR imaging within the central portion of the lesion. Until now, however, correlation between contrast enhancement and timing of image acquisition in nontreated VS has not been analyzed systematically. The authors undertook this study to investigate changes in contrast enhancement with respect to latency of image acquisition after contrast agent administration.

METHODS

The dynamics of contrast medium uptake were evaluated with T1-weighted VIBE MR imaging sequences performed immediately and 1.5, 3.5, 4.5, 9.5, and 11.5 minutes after administration of single dose of Gd in 21 patients with nontreated medium- to large-sized VSs. Signal-to-noise (SNR) and contrast-to-noise ratio (CNR) of tumors were evaluated, and volumes of central nonenhancing areas (NEAs) were determined.

RESULTS

The interior appearance of the tumors changed considerably over time. The NEA significantly diminished in size (p < 0.0001, Friedman test) and almost completely disappeared in all but 2 patients. Compared to images at 1.5 minutes, NEA volumes decreased to a median of 36% at 3.5 minutes and 34% at 4.5 minutes, showing smaller changes after that-9% at 9.5 minutes and 3% at 11.5 minutes. Tumor SNR and CNR increased over time. The maximum change in the median values for SNR and CNR were a 72% increase and 117% increase, respectively; both occurred at 1.5 minutes after Gd administration.

CONCLUSIONS

Contrast enhancement in VS MR imaging varies according to the duration of the delay between contrast agent administration and image acquisition. Postradiotherapy changes in contrast enhancement of VS can therefore not be attributed only to effective radiotherapy. So-called "loss of central contrast enhancement" may be falsely detected because of timing. A standardized protocol with defined timing of image acquisition may increase comparability of contrast uptake in VS.

Optimal dose of stereotactic radiosurgery for acoustic neuromas: a systematic review

Radiosurgery is increasingly employed in the treatment of acoustic neuroma, but the optimal dose in terms of long-term tumour control and minimal adverse effects has not been established. We performed a systematic review of the published literature of radiosurgery of acoustic neuroma to assess whether the use of low dose radiosurgery is as effective as high dose treatment. Reports of radiosurgery for acoustic neuroma were identified through a Medline search. Studies with at least 15 patients and a median follow-up longer than 12 months were included. The relationship between actuarial 5-year progression-free survival (PFS), and tumour and treatment parameters was examined. Forty-two studies were included. Tumour control following lower radiosurgery doses was similar to that reported following high doses. Only 12 studies reported actuarial outcomes at 5 years. There was no relationship between PFS at 5 years and dose to the tumour margin. Radiosurgery of larger tumours was associated with lower 5 year PFS (p < 0.05). Although on initial inspection radiosurgery of acoustic neuroma with doses of 12 - 13 Gy seems to be as effective as higher dose treatment, the available reports are subject to a number of confounding factors, are not sufficiently statistically powered and there is only limited long-term actuarial outcome data. Currently, available studies do not provide sufficient confidence to support the claim that low dose radiosurgery is equally effective as higher doses in the long-term control of acoustic neuroma.

Current concepts in stereotactic radiosurgery - a neurosurgical and radiooncological point of view

Stereotactic radiosurgery is related to the history of "radiotherapy" and "stereotactic neurosurgery". The concepts for neurosurgeons and radiooncologists have been changed during the last decade and have also transformed neurosurgery. The gamma knife and the stereotactically modified linear accelerator (LINAC) are radiosurgical equipments to treat predetermined intracranial targets through the intact skull without damaging the surrounding normal brain tissue. These technical developments allow a more precise intracranial lesion control and offer even more conformal dose plans for irregularly shaped lesions. Histological determination by stereotactic biopsy remains the basis for any otherwise undefined intracranial lesion. As a minimal approach, it allows functional preservation, low risk and high sensitivity. Long-term results have been published for various indications. The impact of radiosurgery is presented for the management of gliomas, metastases, brain stem lesions, benign tumours and vascular malformations and selected functional disorders such as trigeminal neuralgia. In AVM's it can be performed as part of a multimodality strategy including resection or endovascular embolisation. Finally, the technological advances in radiation oncology as well as stereotactic neurosurgery have led to significant improvements in radiosurgical treatment opportunities. Novel indications are currently under investigation. The combination of both, the neurosurgical and the radiooncological expertise, will help to minimize the risk for the patient while achieving a greater treatment success.

Long-term results of stereotactic proton beam radiotherapy for acoustic neuromas

BACKGROUND AND PURPOSE

A retrospective study evaluating the role of hypofractionated stereotactic proton beam therapy for acoustic neuromas.

MATERIALS AND METHODS

The data of 51 patients treated with hypofractionation (3 fractions) and followed up for a minimum of 2 years, were analyzed. Mean dose prescribed to ICRU reference point (isocenter) was 26 cobalt gray equivalent (CGyE) in 3 fractions. Mean minimum tumor dose was 21.4 CGyE/3. Cranial nerve functions were evaluated clinically. Serial MR Scans were used to evaluate local control.

RESULTS

With a mean clinical and radiological follow-up of 72 and 60 months respectively, the 5-year results showed a 98% local control, with a hearing preservation of 42%, a facial nerve preservation of 90.5% and a trigeminal nerve preservation of 93%.

CONCLUSION

For those patients harboring large acoustic neuromas that are inoperable, hypofractionated stereotactic proton beam offers long-term control with minimal side-effects.

Guiding patients through the choices for treating vestibular schwannomas: balancing options and ensuring informed consent. 2007

Counseling patients who are diagnosed with vestibular schwannomas, formerly known as acoustic neuromas, can be challenging. The health care provider has the responsibility to explain, in understandable language, to the patient or legal representative the proposed treatment options, risks and complications associated with each form of treatment, and alternatives to treatment, including no therapy. Patients should be encouraged to gather information before making a treatment decision. For the physicians managing these patients, information should be delivered in a balanced way to ensure patient understanding of their options leading to adequate informed consent.

Stereotactic radiation techniques in the treatment of acoustic schwannomas. 2007

Medical decision-making is based on benefit-to-cost analysis. Optimally, treatment obtains a high degree of benefit while minimizing the physical, social, and financial costs. The goals of the treatment of acoustic schwannomas are prohibiting tumor growth and alleviation of symptoms caused by damage to local structures. These symptoms-tinnitus, ataxia, and hearing loss-secondary to eighth nerve dysfunction, as well as symptoms arising from damage to adjacent structures such as the facial nerve, trigeminal nerve, or pons, can be caused by tumor growth or treatment. Determination of optimal therapy must also take into account an understanding of the natural history of the disease, because acoustic schwannomas are slow-growing benign tumors that when left untreated, usually enlarge over time and cause problems.

Stereotactic radiation techniques in the treatment of acoustic schwannomas

Medical decision-making is based on benefit-to-cost analysis. Optimally, treatment obtains a high degree of benefit while minimizing the physical, social, and financial costs. The goals of the treatment of acoustic schwannomas are prohibiting tumor growth and alleviation of symptoms caused by damage to local structures. These symptoms-tinnitus, ataxia, and hearing loss--secondary to eighth nerve dysfunction, as well as symptoms arising from damage to adjacent structures such as the facial nerve, trigeminal nerve, or pons, can be caused by tumor growth or treatment. Determination of optimal therapy must also take into account an understanding of the natural history of the disease, because acoustic schwannomas are slow-growing benign tumors that when left untreated, usually enlarge over time and cause problems.

Guiding patients through the choices for treating vestibular schwannomas: balancing options and ensuring informed consent

Counseling patients who are diagnosed with vestibular schwannomas, formerly known as acoustic neuromas, can be challenging. The health care provider has the responsibility to explain, in understandable language, to the patient or legal representative the proposed treatment options, risks and complications associated with each form of treatment, and alternatives to treatment, including no therapy. Patients should be encouraged to gather information before making a treatment decision. For the physicians managing these patients, information should be delivered in a balanced way to ensure patient understanding of their options leading to adequate informed consent.

Long-term outcome of stereotactic radiosurgery (SRS) in patients with acoustic neuromas

PURPOSE

To evaluate the effectiveness and long-term outcome of stereotactic radiosurgery (SRS) for acoustic neuromas (AN).

PATIENTS AND METHODS

Between 1990 and 2001, we treated 26 patients with 27 AN with SRS. Two patients suffered from neurofibromatosis type 2. Before SRS, a subtotal or total resection had been performed in 3 and in 5 patients, respectively. For SRS, a median single dose of 13 Gy/80% isodose was applied.

RESULTS

The overall actuarial 5-year and 10-year tumor control probability in all patients was 91%. Two patients developed tumor progression after SRS at 36 and 48 months. Nineteen patients (73%) were at risk of treatment-related facial nerve toxicity; of these, 1 patient developed a complete facial nerve palsy after SRS (5%). A total of 93% of the lesions treated were at risk of radiation-induced trigeminal neuralgia. Two patients (8%) developed mild dysesthesia of the trigeminal nerve after SRS. The hearing preservation rate in patients with useful hearing before SRS was 55% at 9 years.

CONCLUSION

Stereotactic radiosurgery results in good local control rates of AN and the risk of cranial nerve toxicities is acceptable. As toxicity is lower with fractionated stereotactic radiotherapy, SRS should be reserved for smaller lesions.

Staged Stereotactic Irradiation for Acoustic Neuroma

OBJECTIVE:

Stereotactic radiosurgery has proven effective in the treatment of acoustic neuromas. Prior reports using single-stage radiosurgery consistently have shown excellent tumor control, but only up to a 50 to 73% likelihood of maintaining hearing at pretreatment levels. Staged, frame-based radiosurgery using 12-hour interfraction intervals previously has been shown by our group to achieve excellent tumor control while increasing the rate of hearing preservation at 2 years to 77%. The arrival of CyberKnife (Accuray, Inc., Sunnyvale, CA) image-guided radiosurgery now makes it more practical to treat acoustic neuroma with a staged approach. We hypothesize that such factors may further minimize injury of adjacent cranial nerves. In this retrospective study, we report our experience with staged radiosurgery for managing acoustic neuromas.

METHODS:

Since 1999, the CyberKnife has been used to treat more than 270 patients with acoustic neuroma at Stanford University. Sixty-one of these patients have now been followed up for a minimum of 36 months and form the basis for the present clinical investigation. Among the treated patients, the mean transverse tumor diameter was 18.5 mm, whereas the total marginal dose was either 18 or 21 Gy using three 6- or 7-Gy fractions. Audiograms and magnetic resonance imaging were obtained at 6-months intervals after treatment for the first 2 years and then annually thereafter.

RESULTS:

Of the 61 patients with a minimum of 36 months of follow-up (mean, 48 mo), 74% of patients with serviceable hearing (Gardner-Robinson Class 1–2) maintained serviceable hearing at the last follow-up, and no patient with at least some hearing before treatment lost all hearing on the treated side. Only one treated tumor (2%) progressed after radiosurgery; 29 (48%) of 61 decreased in size and 31 (50%) of the 61 tumors were stable. In no patients did new trigeminal dysfunction develop, nor did any patient experience permanent injury to their facial nerve; two patients experienced transient facial twitching that resolved in 3 to 5 months.

CONCLUSION:

Although still preliminary, these results indicate that improved tumor dose homogeneity and a staged treatment regimen may improve hearing preservation in acoustic neuroma patients undergoing stereotactic radiosurgery.

Gamma knife surgery for vestibular schwannoma: 10-year experience of 195 cases

Object. The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation.

Methods. A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm3 (range 0.04–23.1 cm3). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months.

A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor.

Conclusions. Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.

Gamma knife surgery for vestibular schwannoma: 10-year experience of 195 cases

Object.The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation.

Methods.A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm3(range 0.04–23.1 cm3). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months.

A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor.

Conclusions.Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.

Radiosurgical Planning of Meningiomas: Compromises with Conformity

The radiosurgical planning of meningiomas frequently necessitates compromises between irradiating tumour and risking damage to adjacent structures. In selected cases, we resolved this by excluding part of the tumour from the prescription isodose volume. Most of these compromises or 'suboptimal' plans achieved growth control. Growth control could not be related to conformity indices or to various measures of the radiation dose received by the meningioma. Examining recurrences, 75% arose from dura outside the original treatment field. These findings are discussed in terms of dose prescription protocols and the use of conformity indices in planning. The importance of the dural origin of meningiomas is well established in surgical practice, as reflected by Simpson's grades, but may be equally significant in radiosurgical practice.

Quality of life following microsurgery, radiosurgery and conservative management for unilateral vestibular schwannoma

The best way to manage small and medium-sized vestibular schwannomas is currently a matter of heated debate. As these tumours are not immediately life-threatening, patients are invariably concerned about how management would affect their quality of life. Until now, no study has compared the three treatment modalities in terms of physical, psychological and social wellbeing. This study is based on a retrospective database analysis and postal questionnaire survey of unilateral vestibular schwannoma patients who had either been managed conservatively, or treated with microsurgery or radiosurgery. The results showed that: quality of life (measured by the Glasgow Benefit Inventory) deteriorated after microsurgery, particularly for small tumours; conservative management did not lead to a change in quality of life, and there was a trend towards poorer quality of life following radiosurgery. The findings suggest that a conservative management approach may be more appropriate for small tumours, and that patients who are due to undergo microsurgery or radiosurgery may benefit from counselling about the potential impact of treatment on quality of life.

Gamma knife stereotactic radiosurgery for unilateral acoustic neuromas

OBJECTIVE

To evaluate the clinical results achievable using current techniques of gamma knife stereotactic radiosurgery to treat sporadic unilateral acoustic neuromas.

METHODS

A retrospective review of 234 consecutive patients treated for unilateral acoustic neuromas between 1996 and 1999, with a mean (SD) follow up of 35 (16) months. Tumour control was assessed with serial radiological imaging and by the need for surgical intervention. Hearing preservation was assessed using Gardner-Robertson grades. Details of complications including cranial neuropathies and non-specific vestibulo-cochlear symptoms are included.

RESULTS

A tumour control rate in excess of 92% was achieved, with only 3% of patients undergoing surgery after radiosurgery. Results were less good for larger tumours, but control rates of 75% were achieved for 35-45 mm diameter lesions. Of patients with discernible hearing, Gardner-Robertson grades were unchanged in 75%. Facial nerve function was adversely affected in 4.5%, but fewer than 1% of patients had persistent weakness. Trigeminal symptoms improved in 3%, but developed in 5% of patients, being persistent in less than 1.5%. Transient non-specific vestibulo-cochlear symptoms were reported by 13% of patients.

CONCLUSIONS

Tumour control rates, while difficult to define, are comparable after radiosurgery with those experienced after surgery. The complications and morbidity after radiosurgery are far less frequent than those encountered after surgery. This, combined with its minimally invasive nature, may make radiosurgery increasingly the treatment of choice for small and medium sized acoustic neuromas.

Facial neuropathy due to axonal degeneration and microvasculitis following gamma knife surgery for vestibular schwannoma: a histological analysis

✓ Complete facial palsy (House—Brackmann Grade VI) developed in a 63-year-old man with a vestibular schwannoma 25 months after he had undergone two gamma knife surgeries performed 33 months apart and involving a cumulative dose of 24 Gy directed to the tumor margin at the 50% isodose line. Magnetic resonance imaging demonstrated tumor enlargement with central nonenhancement, which initially had been recognized 21 months after the second radiosurgery. Microsurgery was performed to achieve total removal of the tumor. Histological and immunohistochemical examinations of the facial nerve specimen removed from the edge of the tumor revealed a loss of axons, proliferation of Schwann cells, and microvasculitis. In this case, microvasculitis and axonal degeneration were probably the major causes of the radiation-induced facial neuropathy.

Treatment of acoustic neuroma: stereotactic radiosurgery vs. microsurgery

PURPOSE

Two major treatment options are available for patients with acoustic neuroma, microsurgery and radiosurgery. Our objective was to compare these two treatment modalities with respect to tumor growth control, hearing preservation, development of cranial neuropathies, complications, functional outcome, and patient satisfaction.

METHODS AND MATERIALS

To compare radiosurgery with microsurgery, we analyzed 96 patients with unilateral acoustic neuromas treated with Leksell Gamma Knife or microsurgery at Memorial Hermann Hospital, Houston, Texas, between 1993 and 2000. Radiosurgery technique involved multiple isocenter (1-30 single fraction fixed-frame magnetic resonance imaging) image-based treatment with a mean dose prescription of 14.5 Gy. Microsurgery included translabyrinthine, suboccipital, and middle fossa approaches with intraoperative neurophysiologic monitoring. Preoperative patient characteristics were similar except for tumor size and age. Patients undergoing microsurgery were younger with larger tumors compared to the radiosurgical group. The tumors were divided into small <2.0 cm, medium 2.0-3.9 cm, or large >4.0 cm. Median follow-up of the radiosurgical group was longer than the microsurgical group, 48 months (3-84 months) vs. 24 months (3-72 months).

RESULTS

There was no statistical significance in tumor growth control between the two groups, 100% in the microsurgery group vs. 91% in the radiosurgery group (p > 0.05). Radiosurgery was more effective than microsurgery in measurable hearing preservation, 57.5% vs. 14.4% (p = 0.01). There was no difference in serviceable hearing preservation between the two groups. Microsurgery was associated with a greater rate of facial and trigeminal neuropathy in the immediate postoperative period and at long-term follow-up. The rate of development of facial neuropathy was significantly higher in the microsurgical group than in the radiosurgical group (35% vs. 0%, p < 0.01 in the immediate postsurgical period and 35.3% vs. 6.1%, p = 0.008, at long-term follow-up). Similarly, the rate of trigeminal neuropathy was significantly higher in the microsurgical group than in the radiosurgical group (17% vs. 0% in the immediate postoperative period, p < 001, and 22% vs. 12.2%, p = 0.009, at long-term follow-up). There was no significant difference in exacerbation of preoperative tinnitus, imbalance, dysarthria, dysphagia, and headache. Patients treated with microsurgery had a longer hospital stay (2-16 days vs. 1-2 days, p < 0.01) and more perioperative complications (47.8% vs. 4.6%, p < 0.01) than did patients treated with radiosurgery. There was no correlation between the microsurgical approach used and postoperative symptoms. There was no difference in the postoperative functioning level, employment, and overall patient satisfaction. There was no correlation between the radiation dose, tumor size, number of isocenters used, and postoperative symptoms in the radiosurgical group.

CONCLUSION

Radiosurgical treatment for acoustic neuroma is an alternative to microsurgery. It is associated with a lower rate of immediate and long-term development of facial and trigeminal neuropathy, postoperative complications, and hospital stay. Radiosurgery yields better measurable hearing preservation than microsurgery and equivalent serviceable hearing preservation rate and tumor growth control.

Acute symptoms after gamma knife radiosurgery

Object. The purpose of this study was to examine the widely held assumption that early-onset symptoms after gamma knife radiosurgery (GKS) are uncommon. The study was designed to include all types of morbidity and not just those that lead to neurological dysfunction. It was hoped that the results of the study could lead to a more rational follow-up protocol.

Methods. Data regarding adverse events were collected prospectively (within 2–3 weeks post-GKS) by telephone interview from 47 of the first 65 patients who could be reached. Immediate adverse events were defined as any new or unexpected symptom developing within 2 weeks of treatment and were graded as mild, moderate, or severe.

Two thirds of all patients complained of new adverse symptoms; three patients required prolonged hospitalization, although in one case this was not related to the radiosurgery. The majority of symptomatic patients (91%) experienced mild or moderate complications. More than 50% of patients had headache. One third described pin site—related complications and one fifth suffered from nausea/vomiting or marked tiredness. Patients with moderate symptoms had a larger mean tumor volume and higher radiation dose than other patient groups. Prior radiation therapy, lesion type, or the posttreatment administration of steroid agents did not significantly influence the development of acute symptoms.

Conclusions. Acute adverse events following GKS are not uncommon if all types of morbidity are considered. An increased appreciation of these other complications may improve posttreatment care.

Stereotactic radiosurgery versus stereotactic radiotherapy for patients with vestibular schwannoma: a Leksell Gamma Knife Society 2000 debate

✓ By definition, the term “radiosurgery” refers to the delivery of a therapeutic radiation dose in a single fraction, not simply the use of stereotaxy. Multiple-fraction delivery is better termed “stereotactic radiotherapy.” There are compelling radiobiological principles supporting the biological superiority of single-fraction radiation for achieving an optimal therapeutic response for the slowly proliferating, late-responding, tissue of a schwannoma. It is axiomatic that complication avoidance requires precise three-dimensional conformality between treatment and tumor volumes. This degree of conformality can only be achieved through complex multiisocenter planning. Alternative radiosurgery devices are generally limited to delivering one to four isocenters in a single treatment session. Although they can reproduce dose plans similar in conformality to early gamma knife dose plans by using a similar number of isocenters, they cannot reproduce the conformality of modern gamma knife plans based on magnetic resonance image—targeted localization and five to 30 isocenters.

A disturbing trend is developing in which institutions without nongamma knife radiosurgery (GKS) centers are championing and/or shifting to hypofractionated stereotactic radiotherapy for vestibular schwannomas. This trend appears to be driven by a desire to reduce complication rates to compete with modern GKS results by using complex multiisocenter planning. Aggressive advertising and marketing from some of these centers even paradoxically suggests biological superiority of hypofractionation approaches over single-dose radiosurgery for vestibular schwannomas. At the same time these centers continue to use the term radiosurgery to describe their hypofractionated radiotherapy approach in an apparent effort to benefit from a GKS “halo effect.” It must be reemphasized that as neurosurgeons our primary duty is to achieve permanent tumor control for our patients and not to eliminate complications at the expense of potential late recurrence. The answer to minimizing complications while maintaining maximum tumor control is improved conformality of radiosurgery dose planning and not resorting to homeopathic radiosurgery doses or hypofractionation radiotherapy schemes.

Gamma surgery for vestibular schwannoma

OBJECT

The goal of this study was to assess the results of gamma surgery (GS) for vestibular schwannoma (VS) in 200 cases treated over the last 10 years and to review the role of this neurosurgical procedure in the management of VS.

METHODS

Follow-up reviews ranging from 1 to 10 years were available in 153 of these patients. Follow-up images in these cases were analyzed using computer software that we developed to obtain volume measurements for the tumors, and the clinical condition of the patients was assessed using questionnaires. Gamma surgery was the primary treatment modality in 96 cases and followed microsurgery in 57 cases. Tumors ranged in volume from 0.02 to 18.3 cm(3). In the group in which GS was the primary treatment, a decrease in volume was observed in 78 cases (81%), no change in 12 (12%), and an increase in volume in six cases (6%). The decrease was more than 75% in seven cases. In the group treated following microsurgery, a decrease in volume was observed in 37 cases (65%), no change in 14 (25%), and an increase in volume in six (11%). The decrease was more than 75% in eight cases. Five patients experienced trigeminal dysfunction; in three cases this was transient and in the other two it was persistent, although there has been improvement. Three patients had facial paresis (in one case this was transient, lasting 6 weeks; in one case there was 80% recovery at 18 months posttreatment; and in one case surgery was performed after the onset of facial paresis for presumed increase in tumor size). Over a 6-year period, hearing deteriorated in 60% of the patients. Three patients showed an improvement in hearing. No hearing deterioration was observed during the first 2 years of follow-up review.

CONCLUSIONS

Gamma surgery should be used to treat postoperative residual tumors as well as tumors in patients with medical conditions that preclude surgery. Microsurgery should be performed whenever a surgeon is confident of extirpating the tumor with a risk-benefit ratio superior to that presented in this study.

Microanatomical variations in the cerebellopontine angle associated with vestibular schwannomas (acoustic neuromas): a retrospective study of 1006 consecutive cases

OBJECT

Great advances in neuroimaging, intraoperative cranial nerve monitoring, and microsurgical technique have shifted the focus of acoustic neuroma surgery from prolonging life to preserving cranial nerve function in patients. An appreciation of the vascular and cranial nerve microanatomy and the intimate relationship between neurovascular structures and the tumor is essential to achieve optimum results. In this paper the authors analyze the microanatomical variations in location of the facial and cochlear nerves in the cerebellopontine angle (CPA) associated with acoustic neuromas and, additionally, describe the frequency of involvement of surrounding neural and vascular structures with acoustic tumors of varying size. The authors base these findings on their experience with 1006 consecutive patients who underwent surgery via a retrosigmoid or translabyrinthine approach.

METHODS

Between July 1969 and January 1998, the senior author (D.M.L.) performed surgery in 1022 patients for acoustic neuroma: 705 (69%) via the retrosigmoid (suboccipital); 301 (29%) via the translabyrinthine; and 16 (2%) via the middle fossa approach. Patients undergoing the middle fossa approach were excluded from the study. The remaining 1006 patients were subdivided into three groups based on tumor size: Group I tumors (609 patients [61%]) were smaller than 2.5 cm; Group II tumors (244 patients [24%]) were between 2.5 and 4 cm; and Group III tumors (153 patients [15%]) were larger than 4 cm. The senior author's operative notes were analyzed for each patient. Relevant cranial nerve and vascular "involvement" as well as anatomical location with respect to the tumor in the CPA were noted. "Involvement" was defined as adherence between neurovascular structure and tumor (or capsule), for which surgical dissection was required to free the structure. Seventh and eighth cranial nerve involvement was divided into anterior, posterior, and polar (around the upper or lower pole) locations. Anterior and posterior locations were further subdivided into upper, middle, or lower thirds of the tumor. The most common location of the seventh cranial nerve (facial) was the anterior middle third of the tumor for all groups, although a significant number were found on the anterior superior portion. The posterior location was exceedingly rare (< 1%). Interestingly, patients with smaller tumors (Group I) had an incidence (3.4%) of the seventh cranial nerve passing through the tumor itself, equal to that of patients with larger tumors. The most common location of the eighth cranial nerve complex was the anterior inferior portion of the tumor. Not surprisingly, larger tumors (Group III) had a higher incidence of involvement of fourth cranial nerve (41%), fifth cranial nerve (100%), ninth-11th cranial nerve complex (99%), and 12th cranial nerve (31%), as well as superior cerebellar artery (79%), anterior inferior cerebellar artery (AICA) trunk (91.5%), AICA branches (100%), posterior inferior cerebellar artery (PICA) trunk (59.5%), PICA branches (79%), and the vertebral artery (VA) (93.5%). A small number of patients in Group III also had AICA (3.3%), PICA (3.3%), or VA (1.3%) vessels within the tumor itself.

CONCLUSIONS

In this study, the authors show the great variation in anatomical location and involvement of neurovascular structures in the CPA. With this knowledge, they present certain technical lessons that may be useful in preserving nerve function during surgery and, in doing so, hope to provide neurosurgeons and neurootologists with valuable information that may help to achieve optimum outcomes in patients.

Spinal melanotic schwannoma: a tumour with poor prognosis

AIM

To clarify the prognosis of melanotic schwannoma. This is a rare tumour which is generally considered as a benign lesion, reported in many cases with a short follow-up only.

METHODS AND RESULTS

Five cases of spinal melanotic schwannoma were retrospectively studied. The tumours were examined using standard histological, immunohistochemical and ultrastructural methods. No features of malignancy (high mitotic count, atypia or necrosis) were found in the primary tumours. The follow-up period ranged from 3 to 7 years. Malignant clinical behaviour was clear-cut in four cases: three patients died from metastases to various sites and one presented several discrete spinal tumours of the same type seven years after the first operation. Only one patient presented no recurrence and was free of disease 6 years after initial diagnosis. The review of 57 cases of the literature (including our cases), showed that 15% of the cases had recurrences and 26.3% were complicated by metastasis. Only 53% of the cases followed for more than 5 years, were free of disease vs. 67.5% of the cases with shorter follow-up. Twenty additional cases had no follow-up.

CONCLUSION

Appropriate long-term follow-up is required for all melanotic schwannomas, as it may recur or metastasize after more than 5 years, even in the absence of overt malignant histological features.

Vestibular schwannoma management. Part I. Failed microsurgery and the role of delayed stereotactic radiosurgery

OBJECT

The purpose of this study was to analyze patient outcomes and to define the role of radiosurgery in patients who have undergone prior microsurgical resection of their vestibular schwannoma.

METHODS

The authors evaluated the pre- and postoperative clinical and neuroimaging characteristics of 76 consecutive patients with 78 vestibular schwannomas who underwent radiosurgery after previous surgical resection. Twenty-nine patients (37% of tumors) had undergone more than one prior resection. Forty-three patients (55% of tumors) had significant impairment of facial nerve function (House-Brackmann Grades III-VI) after their microsurgical procedure; 50% had trigeminal sensory loss, and 96% had poor speech discrimination (< 50%). The median evaluation period following radiosurgery was 43 months (range 12-101 months). Tumor growth control after radiosurgery was achieved in 73 tumors (94%). Six patients underwent additional surgical resection despite radiosurgery (median of 32 months after radiosurgery), and one patient underwent repeated radiosurgery for tumor progression outside the irradiated volume. Eleven (23%) of 47 patients with Grades I to III facial function before radiosurgery developed increased facial weakness after radiosurgery. Eleven patients (14%) developed new trigeminal symptoms.

CONCLUSIONS

Radiosurgery proved to be a safe and effective alternative to additional microsurgery in patients in whom the initial microsurgical removal failed. Stereotactic radiosurgery should be considered for all patients who have regrowth or progression of previously surgically treated vestibular schwannomas.

Vestibular schwannoma management. Part II. Failed radiosurgery and the role of delayed microsurgery

OBJECT

The indications, operative findings, and outcomes of vestibular schwannoma microsurgery are controversial when it is performed after stereotactic radiosurgery. To address these issues, the authors reviewed the experience at two academic medical centers.

METHODS

During a 10-year interval, 452 patients with unilateral vestibular schwannomas underwent gamma knife radiosurgery. Thirteen patients (2.9%) underwent delayed microsurgery at a median of 27 months (range 7-72 months) after they had undergone radiosurgery. Six of the 13 patients had undergone one or more microsurgical procedures before they underwent radiosurgery. The indications for surgery were tumor enlargement with stable symptoms in five patients, tumor enlargement with new or increased symptoms in five patients, and increased symptoms without evidence of tumor growth in three patients. Gross-total resection was achieved in seven patients and near-gross-total resection in four patients. The surgery was described as more difficult than that typically performed for schwannoma in eight patients, no different in four patients, and easier in one patient. At the last follow-up evaluation, three patients had normal or near-normal facial function, three patients had moderate facial dysfunction, and seven had facial palsies. Three patients were incapable of caring for themselves, and one patient died of progression of a malignant triton tumor.

CONCLUSIONS

Failed radiosurgery in cases of vestibular schwannoma was rare. No clear relationship was demonstrated between the use of radiosurgery and the subsequent ease or difficulty of delayed microsurgery. Because some patients have temporary enlargement of their tumor after radiosurgery, the need for surgical resection after radiosurgery should be reviewed with the neurosurgeon who performed the radiosurgery and should be delayed until sustained tumor growth is confirmed. A subtotal tumor resection should be considered for patients who require surgical resection of their tumor after vestibular schwannoma radiosurgery.

Microanatomical variations in the cerebellopontine angle associated with vestibular schwannomas (acoustic neuromas)

Great advances in neuroimaging, intraoperative cranial nerve monitoring, and microsurgical technique have shifted the focus of acoustic neuroma surgery from prolonging life to preserving cranial nerve function in patients. An appreciation of the vascular and cranial nerve microanatomy and the intimate relationship between neurovascular structures and the tumor is essential to achieve optimum results. In this paper the authors analyze the microanatomical variations in location of the facial and cochlear nerves in the cerebellopontine angle (CPA) associated with acoustic neuromas and, additionally, describe the frequency of involvement of surrounding neural and vascular structures with acoustic tumors of varying size. The authors base their findings on their experience treating 1006 consecutive patients who underwent surgery via a retrosigmoid or translabyrinthine approach.

Between July 1969 and January 1998, the senior author (D.M.L.) performed surgery in 1022 patients for acoustic neuroma: 705 (69%) via the retrosigmoid (suboccipital); 301 (29%) via translabyrinthine; and 16 (2%) via middle fossa approach. Patients undergoing the middle fossa approach were excluded from the study. Patients were subdivided into three groups based on tumor size: Group 1 tumors (609 patients [61%]) were smaller than 2.5 cm; Group 2 tumors (244 patients [24%]) were between 2.5 and 4 cm; and Group 3 tumors (153 patients [15%]) were larger than 4 cm. Operative notes were analyzed for each patient. Relevant cranial nerve and vascular “involvement” as well as anatomical location with respect to the tumor in the CPA were noted. “Involvement” was defined as intimate contact between neurovascular structure and tumor (or capsule), where surgical dissection was required to free the structure. Seventh and eighth cranial nerve involvement was divided into anterior, posterior, and polar (around the upper or lower pole) locations. Anterior and posterior locations were further subdivided into upper, middle, or lower thirds of the tumor.

The most common location of the seventh cranial nerve (facial) was the anterior middle third of the tumor for Groups 1, 2, and 3, although a significant number were found on the anterior superior portion. The posterior location was exceedingly rare (< 1%). Interestingly, patients with smaller tumors (Group 1) had an incidence (3.4%) of the seventh cranial nerve passing through the tumor itself equal to that of patients with larger tumors. The most common location of the seventh cranial nerve complex was the anterior inferior portion of the tumor. Not surprisingly, larger tumors (Group 3) had a higher incidence of involvement of sixth cranial nerve (41%), fifth cranial nerve (100%), ninth-11th cranial nerve complex (99%), 12th cranial nerve (31%), as well as superior cerebellar artery (79%), anterior inferior cerebellar artery (AICA) trunk (91.5%), AICA branches (100%), posterior inferior cerebellar artery (PICA) trunk (59.5%), PICA branches (79%), and the vertebral artery (93.5%). A small number of patients in Group 3 also had AICA (3.3%), PICA (3.3%), or vertebral artery (1.3%) vessels within the tumor itself.

In this study, the authors show the great variation in anatomical location and involvement of neurovascular structures in the CPA. With this knowledge, they present certain technical lessons that may be useful in preserving function during surgery and, in doing so, hope to provide neurosurgeons and neurootologists with valuable information that may help to achieve optimum cranial nerve outcomes in patients.

Vestibular schwannoma management in the next century: a radiosurgical perspective

PURPOSE

To discuss how the evolution of vestibular schwannoma radiosurgery, changes in health care delivery, and patient accessibility to medical information will affect the management of vestibular schwannomas in the future.

CONCEPT

In comparison with microsurgical resection of vestibular schwannomas, radiosurgery has a lower morbidity rate, a similar risk of requiring further surgery, and higher patient satisfaction. As this information becomes more widely available to patients and third-party payors, radiosurgery may replace surgical resection as the preferred management strategy for patients with small to medium sized vestibular schwannomas in the United States.

RATIONALE

It is estimated that 2500 patients are diagnosed with vestibular schwannomas each year in the United States. Assuming that 80% undergo surgery, 2000 operations are performed annually for newly diagnosed vestibular schwannomas. Data available since 1987 regarding the number of cases for which gamma knife radiosurgery was performed were used to predict the number of patients who will undergo vestibular schwannoma radiosurgery in the future. If the current trend continues, an equal number of patients will undergo surgical resection and radiosurgery to treat their vestibular schwannomas (approximately 1000/yr) sometime between 2005 and 2010. Moreover, it is predicted that by 2020, two-thirds of the patients who are newly diagnosed with vestibular schwannomas will undergo radiosurgery, with surgical resection being reserved for patients with large tumors associated with symptomatic brain stem compression.

DISCUSSION

Early data regarding vestibular schwannoma radiosurgery predicted an exponential growth curve. Although it is premature to assume that the current trend will continue, it is likely that an ever increasing percentage of patients will undergo radiosurgery as accessibility to this alternative increases, and more data are published regarding long-term tumor growth control rates. If the mathematical model proves to be accurate, then stereotactic radiosurgery will replace surgical resection as the preferred management strategy for the majority of patients with vestibular schwannomas.

Acute hearing loss following fractionated stereotactic radiosurgery for acoustic neuroma. Report of two cases

Two cases of acute hearing loss are reported following fractionated stereotactic radiosurgery for acoustic neuroma. Both patients had neurofibromatosis type 2 and were treated with a peripheral tumor dose of 21 Gy delivered in three fractions (7 Gy each) with a minimum interfraction interval of 10 hours. One patient who had previously undergone surgical resection of the treated tumor presented with only rudimentary hearing in the treated ear secondary to an abrupt decrease in hearing prior to treatment. That patient reported total loss of hearing before complete delivery of the third fraction. The second patient had moderately impaired hearing prior to treatment; however, within 10 hours after delivery of the final fraction, he lost all hearing. Both patients showed no improvement in response to glucocorticoid therapy. Possible explanations for this phenomenon are presented.