Radiological factors related to pre-operative hearing levels in patients with vestibular schwannomas

The use of cochlear-enhancement imaging to predict hearing preservation following vestibular schwannoma removal

BACKGROUND

Hearing preservation is challenging for patients after the removal of large vestibular schwannomas (VSs). Here, using preoperative magnetic resonance (MR) imaging, we investigated the significance of cochlear enhancement (CE) for predicting postoperative hearing preservation.

METHODS

Between January 2014 and December 2019, 34 VS-patients with serviceable hearing underwent tumor-removal surgery using a retrosigmoid approach. The presence or absence of CE using both T2-weighted and gadolinium-enhanced T1-weighted MR images was assessed in VS patients using the pixel-analysis method. Segmented volumetric analyses were also performed using GrowCut 3D slicer software.

RESULTS

There were 17 patients (50%) without CE and 17 (50%) with CE. Ten of the 17 non-CE patients (58.8%) had postoperative hearing preservation. In contrast, only 3 of the 17 patients with CE (17.6%) had postoperative hearing preservation. There were no significant tumor-characteristic differences between the two groups. The presence of CE on both the T2-weighted and the gadolinium-enhanced T1-weighted MR images correlated significantly with postoperative hearing outcomes (P=0.032). Only pure-tone averages were significantly different between the two groups (P=0.049).

CONCLUSIONS

Preoperative serviceable hearing is likely to be preserved after surgery in non-CE VS patients. Preoperative CE assessment using MR imaging may be a useful predictor for postoperative hearing outcomes in VS patients.

Sporadic Vestibular Schwannoma Size and Location Do not Correlate With the Severity of Hearing Loss at Initial Presentation

Vestibular schwannoma (VS) is a non-malignant intracranial neoplasm arising from the vestibular branch of the 8th cranial nerve; sensorineural hearing loss (SNHL) is the most common associated symptom. Understanding whether VS imaging characteristics at the time of VS diagnosis can be associated with severity of VS-induced SNHL can impact patient counseling and define promising areas for future research. Patients diagnosed with VS at Massachusetts Eye and Ear (MEE) from 1994 through 2018 were analyzed if magnetic resonance imaging at VS presentation and sequential audiometry were available. Results were compared with original studies available in PubMed, written in English, on VS imaging characteristics and their impact on hearing in patients. A total of 477 patients with unilateral VS from the MEE database demonstrated no significant correlation between any features of tumor imaging at the time of VS diagnosis, such as VS size, impaction or location, and any hearing loss metric. Twenty-three published studies on the impact of VS imaging characteristics on patient hearing met inclusion criteria, with six solely involving NF2 patients and three including both sporadic and NF2-related VS patients. Fifteen studies reported a significant relationship between SNHL and at least one VS imaging characteristic; however, these trends were universally limited to NF2 patients or involved small patient populations, and were not reproduced in larger studies. Taken together, SNHL in sporadic VS patients is not readily associated solely with any tumor imaging characteristics. This finding motivates future studies to define how VS microenvironment and secreted molecules influence VS-induced SNHL.

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.

Prognostic Factors of Long-Term Hearing Preservation in Small and Medium-Sized Vestibular Schwannomas After Microsurgery

OBJECTIVE

The authors evaluated the long-term hearing outcomes of patients with vestibular schwannoma (VS) to explore appropriate surgical treatment.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

A total of 138 patients diagnosed with small and medium-sized VS with serviceable hearing from January 2006 to December 2015.

INTERVENTIONS

All patients underwent microsurgery via retrosigmoid (RSA) or middle cranial fossa approach (MFA) and were followed up for over 2 years.

MAIN OUTCOME MEASURES

Pre- and postoperative hearing, including pure tone audiometry, speech discrimination score, and auditory brainstem response (ABR), were analyzed.

RESULTS

The mean tumor size and volume were 16.6 ± 3.4 mm and 1711.8 ± 918.5 mm, respectively. Preoperative hearing levels were Class A in 42, Class B in 67, and Class C in 29 patients. Patients with a tumor from the superior vestibular nerve (SVN) had better hearing at diagnosis. Postoperative hearing levels were Class A, B, C, and D for 28, 17, 32, and 61 patients. Hearing outcomes were significantly better in patients with normal intraoperative I wave on ABR. Hearing loss within 6 months had a positive effect on postoperative hearing. Better preoperative hearing and tumors from SVN were correlated with better postoperative hearing outcomes. Tumor size, cystic variation, or extension to the fundus of internal auditory canal had no influence on hearing preservation.

CONCLUSIONS

Better preoperative hearing, shorter hearing loss period, tumors from SVN, and normal intraoperative I wave are prognostic factors for serviceable hearing. RSA and MFA are effective and safe for tumor removal and hearing preservation.

Imaging features and classification of peritumoral edema in vestibular schwannoma

BACKGROUND

Peritumoral edema (PTE) is rarely present in patients with vestibular schwannomas (VS). We studied the correlation between radiological tumor characteristics and the presence of edema, describe its magnetic resonance imaging features and classify the different edema patterns.

METHODS

We analysed 605 consecutive patients treated for VS at our Institute. PTE was found in 30 patients, studied on fluid attenuated inversion recovery sequences and categorised as involving the brachium pontis, cerebellum and/or brainstem. Tumor volume, shape, surface, internal structure and axis of growth were evaluated and compared to a matched series of 30 patients without PTE.

RESULTS

In our population of patients, 5% showed PTE. Edema involved the brachium pontis in 22 cases (88%), cerebellum in 15 (60%) and brainstem in 3 (12%). PTE was classified as mild (one region involved), moderate (two regions) and severe (three regions). Edema was present not only perpendicular to the major tumor growth axis but also parallel to it (91%). The difference between the two groups in regards to tumor shape and surface was not significant. We found no correlation between tumor and edema volumes.

CONCLUSIONS

VS can cause PTE, but its incidence is less frequent than in skull base meningiomas. PTE involves most frequently the brachium pontis, followed by the cerebellum and brainstem. Its occurrence correlates with tumor size but not with other radiological VS features. PTE is not always located perpendicular to the major axis of tumor growth, which indicated that the compressive theory proposed for meningiomas is not plausible explanation for its manifestation.

Prognostic Significance of Preoperative Geometric Changes in the Internal Acoustic Canal for Hearing Preservation in Vestibular Schwannoma Surgery

OBJECTIVE

This study focused on the changes in the internal acoustic canal (IAC) caused by vestibular schwannomas (VSs) and their prognostic significance for postoperative hearing outcome.

METHODS

A total of 125 consecutive cases of VS were included. We used a neuronavigation software to perform the following measurements on both the tumor side and healthy side: volume of the IAC (VIAC), maximal diameter of the IAC (DIAC), and length of the IAC (LIAC). A statistical analysis was realized using Spearman correlation to test the correlation of the morphometric measure of the IAC and postoperative hearing. Multivariate analysis was performed to test the impact of measurements of the IAC and preoperative hearing on postoperative hearing.

RESULTS

The mean VIAC on the tumor side and on the healthy side was 0.271 and 0.169 cm³, respectively. The mean DIAC was 9.438 mm on the tumor side and 7.034 mm contralateral. The correlations tests showed significant correlations of both postoperative hearing deficit and degree of hearing loss with 1) VIAC on the tumor side, 2) difference between VIAC on the tumor side and healthy side, 3) DIAC on the tumor side, and 4) difference between the DIAC on the tumor side and healthy side. The multivariate analysis showed significant impact of the DIAC (P = 0.01) and preoperative hearing status (P = 0.02) on postoperative hearing.

CONCLUSIONS

Enlargement of the VIAC and DIAC are negative prognostic factors for hearing preservation. Reasons may be long-standing compression of the auditory nerve and an increased vulnerability of the inner ear structures during the drilling of the IAC.

Vestibular Schwannomas: Do Linear and Volumetric Parameters on MRI Correlate With Hearing Loss?

PURPOSE

To determine if two-dimensional and volumetric imaging parameters in vestibular schwannomas (VS) correlate with hearing loss at presentation.

STUDY DESIGN

Retrospective.

METHODS

Forty-one cases of pathologically confirmed sporadic VS were analyzed. Maximal tumor dimensions in anteroposterior (AP), coronal (ML), and craniocaudal (CC) dimensions were obtained along with tumor-fundus distance and internal auditory canal (IAC) porus diameters. Volumetric analysis was done on 37 cases. Tumors volumes were calculated through both 3-D volumetric and ABC/2 [AP × ML × CC/2] methodology. With the 3-D method, total tumor volume (TTV), and cerebellopontine angle (CPA) tumor volume were separately calculated and IAC volumes obtained by subtracting CPA tumor volumes from TTV. Pure tone average (PTA) and speech discrimination scores (SDS) were correlated with tumor dimensions.

RESULTS

Non-volumetric analysis was performed on 41 tumors. The AP and ML dimensions correlated with both PTA and SDS (p < 0.05). No significant correlations were seen between hearing loss and tumor-fundus distance or porus diameters. The tumor volume calculated through ABC/2 methodology correlated with PTA and SDS (p < 0.05). The 3-D TTV and CPA volumes only correlated with PTA. IAC tumor volumes did not correlate with hearing loss.

CONCLUSION

Maximal AP and ML dimensions are the only non-volumetric variables, which significantly correlate with hearing loss. Tumor volume calculated through ABC/2 method significantly correlates with hearing impairment while the 3-D TTV and CPA tumor volumes only correlated significantly with PTA scores but not SDS scores.

Vestibular schwannoma with repeated intratumoral hemorrhage

Repeated hemorrhage from a vestibular schwannoma is very rare. We report a 15-year-old male, to our knowledge the fourth known patient with repeated hemorrhage of vestibular schwannoma, who presented with rapidly progressive right-sided hearing loss and tinnitus. MRI showed a mass lesion in the right cerebellopontine angle. T1-weighted and T2-weighted MRI revealed a hyperintense intratumoral area, indicating subacute hemorrhage within the tumor. Nine weeks after the initial onset, the patient again presented with a sudden onset headache, nausea, and ataxia. A CT scan showed recurrence of an intratumoral hemorrhage. A subtotal resection was achieved. A histopathological examination of the resected specimen showed typical features of schwannoma. We review the pertinent literature and discuss the features of repeated hemorrhage from a vestibular schwannoma.

Predictors of volumetric growth and auditory deterioration in vestibular schwannomas followed in a wait and scan policy

OBJECTIVE

The purpose of this study was to identify factors predicting growth and audiologic deterioration during follow-up (FU) in a wait and scan (W&S) policy of vestibular schwannomas (VSs) using a novel volumetric measuring tool. So far, only consecutive magnetic resonance imaging (MRI) is able to show growth objectively, and growth, combined with hearing function, generally dictates further intervention. Other factors predicting growth or hearing deterioration would be invaluable and might ease clinical decision making.

STUDY DESIGN

Retrospective case study.

SETTING

Tertiary referral center.

PATIENTS

Sixty-three patients diagnosed with VS at Maastricht University Medical Center between 2003 and 2008, with FU data available from 36 patients.

INTERVENTION(S)

A W&S policy for unilateral VS with sequential contrast-enhanced T1- and T2-weighted MRI and audiograms during FU.

MAIN OUTCOME MEASURE(S)

1. Patient and radiologic VS features potentially related to growth and auditory function during a W&S policy. 2. The correlation between increase in VS volume and audiologic deterioration during FU.

RESULTS

Labyrinthine hypointensity on T2-weighted magnetic resonance images and complaints of hearing loss at presentation are predictive of a faster deterioration of hearing (p < 0.05). Growth during the first FU year predicts further growth. Vestibular schwannoma volume does not correlate with audiologic deterioration significantly.

CONCLUSION

Hypointensity on T2-weighted image of the affected labyrinth will result in a significant faster deterioration of hearing. Hearing loss was more profound, and hearing will deteriorate significantly faster in patients presenting with complaints of hearing loss. Significant growth during the first year of FU predicts further growth during FU. Sequential MRI cannot be substituted by audiologic examinations solely because increase in VS volume does not correlate with audiologic deterioration significantly.

Intratumoral hemorrhage and fibrosis in vestibular schwannoma: a possible mechanism for hearing loss

OBJECT

Vestibular schwannomas (VSs) are benign lesions with an unpredictable natural history. Perhaps the greatest barrier to predicting which patients need treatment is our poor understanding of how these tumors cause hearing loss in the first place. In this case-control study, the authors investigated the relationship between preoperative hearing loss and histological changes such as intratumoral microhemorrhage and extensive fibrosis.

METHODS

From a prospectively collected database, the authors selected all patients with VS who had undergone microsurgical resection as their initial treatment for histopathologically confirmed VS. Histological specimens obtained in 274 of these patients were systematically reviewed by a blinded neuropathologist who graded the extent of microhemorrhage and fibrosis in these tumors. The effect of these variables on preoperative hearing loss was studied using binary logistic regression.

RESULTS

On univariate analysis, patients with extensive intratumoral microhemorrhage or fibrosis (p < 0.0001), patients with larger tumors (p < 0.05), and patients 65 years of age or older (p < 0.05) were significantly more likely to have unserviceable hearing at the time of surgery. On multivariate analysis, only patients with extensive intratumoral microhemorrhage or fibrosis had an increased risk of having unserviceable hearing at the time of surgery (OR 3.72, 95% CI 1.3-10; p = 0.01). Older age and tumor size greater than 3 cm were not statistically significant risk factors for hearing loss, controlling for the effect of microhemorrhage and fibrosis.

CONCLUSIONS

In this study, the authors have demonstrated a correlation between the extent of nonneoplastic histological changes, such as microhemorrhage and fibrosis, and hearing loss. This alternate hypothesis has the potential to explain many of the exceptions to previously described mechanisms of hearing loss in patients with VS. The advent of high-resolution MR imaging technology to identify microhemorrhages may provide a method to screen for patients with VS at risk for hearing loss.