Are Stage IV Vestibular Schwannomas Preoperatively Different From Other Stages?

Vestibular Schwannoma Hypofractionated Stereotactic Radiation Therapy in Five Fractions

AIM

To retrospectively analyse the long-term results of hypofractionated stereotactic radiation therapy (HSRT) applied in five fractions for vestibular schwannomas.

MATERIALS AND METHODS

One hundred and thirty-four patients with vestibular schwannomas underwent medical treatment of HSRT. The median follow-up time interval was 54 months (range 6-121 months). All patients had a prescribed dose of 22 Gy in five fractions to D90. Restaging was carried out by thin-slice contrast-enhanced T1 magnetic resonance imaging. Progression was defined as 2 mm post-treatment tumour enlargement. Progression or death for any reason was counted as an event in progression-free survival rates. Acute toxicity was defined as adverse events occurring within 3 months of HSRT; long-term toxicity was defined as such events occurring after 3 months.

RESULTS

In 74/128 patients who had >6 months of follow-up (54%), the HSRT resulted in a partial or a complete response. The mean time interval for response in 50% of these was 4 years, whereas in 49 patients (38%) vestibular schwannomas failed to show any response, resulting in stable disease. Five of 128 patients (4%) showed marked progressive vestibular schwannomas after treatment in the first 3 years; two of them received conventionally fractionated radiation therapy. Local control at 3, 5 and 7 years was 96%, 95% and 94%, respectively. Seven were lost to follow-up. The median planning target volume was 2.1 ml (range 0.78-8.66). The 3- and 5-year progression-free survival rates were 95% and 94%, respectively. Seven patients reported a marked deterioration in hearing ability. Post-radiation therapy magnetic resonance imaging showed variability in oedema collection, but no patient suffered from radio-necrosis. Grade 2 temporary facial nerve disorders were observed in 10 patients (8%) 3-6 months after HSRT.

CONCLUSION

Delivering HSRT in five fractions for vestibular schwannoma appears safe and efficient, combining both efficiency and short treatment time while optimising neurological function preservation.

Current Understanding of Hearing Loss in Sporadic Vestibular Schwannomas: A Systematic Review

Objective

Hearing loss is the most common initial symptom in patients with sporadic vestibular schwannomas (SVS). Hearing preservation is an important goal of both conservative and surgical therapy. However, the mechanism of SVS-associated hearing loss remains unclear. Thus, we performed this systematic review to summarize the current understanding of hearing loss in the SVS and distill a testable hypothesis to further illuminate its underlying mechanism.

Methods

A systematic review querying four databases (PubMed, Medline, Embase, and Web of Science) was performed to identify studies evaluating hearing loss in patients with SVS and exploring the potential mechanisms of hearing impairment.

Results

A total of 50 articles were eligible and included in this review. After analysis, the retrieved studies could be categorized into four types: (1) 29 studies explore the relationship between hearing loss and the growth pattern of the tumor (e.g., tumor size/volume, growth rate, tumor location, etc.); (2) ten studies investigate the potential role of cochlear dysfunction in hearing deterioration, including structural abnormality, protein elevation in perilymph, and cochlear malfunctioning; (3) two studies looked into SVS-induced impairment of auditory pathway and cortex; (4) in the rest nine studies, researchers explored the molecular mechanism underlying hearing loss in SVS, which involves molecular and genetic alterations, inflammatory response, growth factors, and other tumor-associated secretions.

Conclusions

Multiple factors may contribute to the hearing impairment in SVS, including the growth pattern of tumor, cochlear dysfunction, impairment of auditory pathway and cortex, genetic and molecular changes. However, our current understanding is still limited, and future studies are needed to explore this multifactorial hypothesis and dig deeper into its underlying mechanism.

Vestibular Schwannoma: Results of Hypofractionated Stereotactic Radiation Therapy

PURPOSE

Our purpose was to study the outcomes of hypofractionated stereotactic radiation therapy (HSRT) in terms of hearing and radiologic response for vestibular schwannomas.

METHODS AND MATERIALS

This was a longitudinal retrospective study at a referral center from 2011 to 2016. All treatments were performed on a Cyberknife device with a dose of 21 Gy (3 × 7 Gy) or 25 Gy (5 × 5 Gy). We assessed tumor response, neurologic outcomes (hearing and facial nerve function), and treatment toxicity.

RESULTS

A total of 82 patients were included. Fifty-three patients were treated with the 3 × 7 Gy scheme and 29 with the 5 × 5 Gy. Sixteen patients (20%) had a previous surgery. The median follow-up was 48 months (range, 12-88 months). We noted 3 recurrences leading to a control rate of 96.3%. In our cohort, predictive factors of vestibular schwannoma growth were a tumor volume >2 mm3 and a conformal index <1.1 (P < .0001). The treatment was well tolerated with only 5 grade III acute toxicities (4 vertigo and 1 headache) and no grade IV or V. As for late toxicity, we noticed 2 cases of mild peripheral facial palsy (House and Brackman grade II) in previously operated patients. There was 46.0% hearing preservation among patients with serviceable hearing after HSRT.

CONCLUSIONS

Our results suggest that HSRT using 3 or 5 fractions is a well-tolerated and effective regimen. These findings are in addition to the few previous hypofractionation studies and contribute to the validity of this treatment modality.

Volume quantification of endolymphatic hydrops in patients with vestibular schwannoma

OBJECTIVE

The origin of vestibular symptoms in patients with vestibular schwannoma (VS) is uncertain. We used intratympanic gadolinium-enhanced magnetic resonance imaging (MRI) to confirm the labyrinthine lesions in patients with VS and to explore the features of endolymphatic hydrops (EH) in these patients.

METHODS

In total, 66 patients diagnosed with unilateral VS were enrolled in this study and underwent intratympanic gadolinium-enhanced MRI. The borders of the vestibule and endolymph were mapped on the axial MRI images, and the area and volume of vestibule and endolymph were automatically calculated using Osirix software, and the area and volume percentage of vestibular endolymph were obtained.

RESULTS

The area and volume percentages of vestibular endolymph on the affected side were significantly larger than those on the healthy side (both p < 0.001). Using Kendall's W test, we found that the area and volume percentages of vestibular endolymph on the affected side were consistent (p < 0.001), but the consistency was moderate (k = 0.574). The healthy side was also consistent (p < 0.001), and the degree of consistency was moderate (k = 0.444). We used 19.1% as the cut-off point to distinguish the presence or absence of vestibular EH; that is, the volume percentage of vestibular endolymph that was more than 19.1% were defined as the subgroup with hydrops, while the subgroup without hydrops included patients with a baseline level below 19.1%. No volume classification for vestibular EH was proposed. Based on this standard, 11/66 (16.7%) of the patients with VS in this study had vestibular EH.

CONCLUSIONS

The volume percentage of the vestibular endolymph was more accurate than the area percentage for assessing vestibular EH. Using 19.1% as the cut-off point to distinguish the presence or absence of vestibular EH, we found that 16.7% of patients with VS had varying degrees of vestibular EH. We believe that the vestibular symptoms in patients with VS may originate from the peripheral lesions.

Quantitative Vestibular Labyrinthine Otopathology in Temporal Bones with Vestibular Schwannoma

Objective

Dizziness associated with vestibular schwannoma is usually ascribed to retrolabyrinthine mechanisms. The goal of this study was to determine if quantitative peripheral vestibular (labyrinthine) otopathology was present in a series of patients with vestibular schwannoma.

Study Design

Comparative human temporal bone study.

Setting

Otopathology laboratory.

Subjects and Methods

Temporal bones from 12 subjects with unilateral sporadic vestibular schwannoma were included. Based on differential interference contrast microscopy, type I and II vestibular hair cell counts were performed on each vestibular sense organ with minimal autolysis in which the neuroepithelium was oriented perpendicular to the plane of section. Hair cell densities (cells per 0.01-mm2 surface area) and the presence of endolymphatic hydrops and precipitate within the endolymph or perilymph were compared between the tumor ears and the contralateral (control) ears.

Results

Compared with the contralateral ears, vestibular schwannoma ears had significantly more endolymphatic hydrops ( P = .049) and precipitate in the endolymph and perilymph ( P = .005), lower densities of type I and II vestibular hair cells in the lateral canal cristae (mean differences, respectively: 25.2 [ P = .001] and 10.8 [ P < .001]) and utricle (mean differences, respectively: 26.8 and 10.4 [ P < .001]), and lower densities of type I hair cells and the same density of type II hair cells in the saccule (mean differences, respectively: 26.5 [ P < .001] and 0.9 [ P = .46]).

Conclusion

Peripheral vestibular otopathology, manifested as reductions of vestibular hair cell densities, was identified in ears with vestibular schwannoma. Labyrinthine as well as retrolabyrinthine pathology may contribute to tumor-related vestibular dysfunction.

Preoperative balance control compensation in patients with a vestibular schwannoma: does tumor size matter?

OBJECTIVE

The influence of tumor size on postural control of patients with vestibular schwannoma (VS) remains to be determined. This study aimed to compare the postural performances of VS patients, according to the size of the tumor, with healthy subjects.

METHODS

The six conditions (C1-C6) of the sensory organization test (SOT) were carried out in 87 patients, split into four groups according to the Koos classification (stage I-IV), and in 72 aged-matched controls to evaluate postural control. The vestibular reflectivity and compensation were estimated with videonystagmography.

RESULTS

Among patients, lower C5 and C6 scores were found in stage I and IV patients than in stage II and III patients, whereas vestibular compensation did not impact the tumor size influence on the postural control. The scores were significantly (p<0.001) lower for all the groups of patients than the controls in the vestibular-related SOT conditions (C5-C6).

CONCLUSIONS

Patients with an unilateral VS displayed altered postural performances compared to the control subjects and tumor size had a bell-like pattern effect on balance control.

SIGNIFICANCE

The tumor size could be seen as a determining factor in the implementation of adaptive mechanisms that lead to the postural compensation and might be dissociated from vestibular compensation.

Perioperative complications after translabyrinthine removal of large or giant vestibular schwannoma: Outcomes for 123 patients

CONCLUSION

Large vestibular schwannomas are benign but dangerous tumors. The translabyrinthine approach allows the surgeon to limit vital and functional complications due to the disease itself or to its surgical removal.

OBJECTIVE

Morbi-mortality study focused on large vestibular schwannoma surgically treated by translabyrinthine removal.

METHODS

This was a retrospective review of prospectively collected data in a series of 123 patients who underwent translabyrinthine removal of a large vestibular schwannoma (>4 cm in the cerebellopontine angle, stage IV). All surgical and medical complications and facial function were reviewed, with a 1-year follow-up.

RESULTS

Mortality during the first year was 0.8% (one case of infarct of the anterior inferior cerebellar artery, fatal after 8 months). In all, 4.9% of patients underwent a second surgery (for delayed hemorrhage or cerebrospinal fluid leak) during the first months after removal of a large vestibular schwannoma; 3.2% of patients experienced definitive neurologic complications (one death, one cerebellar disturbance, and two cases of 10th cranial nerve palsy).

Asymmetric hearing loss: rule 3,000 for screening vestibular schwannoma

OBJECTIVE

To assess the diagnostic yield of audiograms associated to electronystagmography (ENG) for screening vestibular schwannomas (VSs), to determine what definition of asymmetric sensorineural hearing loss (ASNHL) fits best for the diagnosis of VS, and to determine if cochleovestibular symptoms and atherosclerotic potential risk factors play a role in the VS screening.

STUDY DESIGN

Retrospective chart review in a tertiary care center.

METHODS

One hundred twenty-two patients were included in the study and divided into 2 groups: 1) patients presenting a VS (n = 74) and 2) patients without VS (n = 48). They had received an audiometry assessment, an ENG, and a posterior fossa magnetic resonance imaging (MRI). In addition, a variety of risk factors and clinical data were collected. Mean hearing threshold by frequency, mean asymmetries by frequency, speech discrimination score (SDS), ENG results, and presence or absence of vertigo are studied. Cochleovestibular symptoms and atherosclerotic potential risk factors were collected. Characteristics were studied with analysis of variance, chi2 test, or a paired t test. A receiver operating characteristic curve was obtained. A logistic regression with a step-wise selection based on the likelihood ratio was used to identify the best subgroup of predictors of the VS.

RESULTS

The most revealing data were the mean ASNHL at 3,000 Hz (p < 0.001), the interaural SDS asymmetry (p < 0.001), the vestibular deficit (p < 0.049), and the absence of vertigo (p < 0.001). The ASNHL at 3,000 Hz was the most representative value of all the frequencies and for the SDS asymmetry. Interaural difference of 15 dB or more at 3,000 Hz is sufficient to consider hearing loss as asymmetric. When the cutoff for a positive test was placed at 50% probability, the receiver operating characteristic curve shows a sensitivity of 73%. The grade of the tumor was also related with the degree of ASNHL at 3,000 Hz. Caloric test does not predict the localization or the grade of the VS. Tinnitus and atherosclerotic potential risk factors were not considered significantly linked with VS.

CONCLUSION

To reduce the number of negative MRI performed in the investigation of an ASNHL, we propose the "rule 3,000," ASNHL of 15 dB or more at the 3,000-Hz frequency. In this case, an investigation with MRI is crucial. If this ASNHL is less than 15 dB, we recommend a biannual audiometric follow-up.