Cochlear FLAIR Signal Changes in Hearing Preservation Vestibular Schwannoma Surgery

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.

Brazilian Society of Otology task force - Vestibular Schwannoma ‒ evaluation and treatment

OBJECTIVE

To review the literature on the diagnosis and treatment of vestibular schwannoma.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy.

CONCLUSIONS

Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

Prognostic Factors for Hearing Preservation Surgery in Small Vestibular Schwannoma

OBJECTIVE

to evaluate recent contributions to the literature on prognostic factors of hearing preservation in small vestibular schwannoma microsurgery.

METHODS

review of the most recent studies.

RESULTS

factors such as tumor size, preoperative hearing status, tumor growth rate, tumor origin, surgical approach, radiological characteristics, results of preoperative neurophysiological tests, preoperative symptoms and demographic features have been investigated and some of them reported to be significant in the prediction of hearing preservation.

CONCLUSIONS

tumor size and preoperative hearing status are the most impactful factors and play a key role in patient selection for hearing preservation surgery. Other features such as fundal extension, tumor origin and impaired ABR could have prognostic value on hearing preservation. Tumor growth rate, preoperative impedance, cVEMPs and age have also recently been found to be significant, but more studies are needed. The role of preoperative tinnitus, vertigo and gender is lacking and controversial, whereas the differences between available surgical approaches have been smoothed out in recent years.

Automated Whole Cochlear T2 Signal Demonstrates Weak Correlation with Hearing Loss in Observed Vestibular Schwannoma

INTRODUCTION

We sought to evaluate the correlation between whole cochlear T2 signal changes obtained with a novel automated segmentation method and hearing levels, both at diagnosis and over time, in patients with observed vestibular schwannoma.

METHODS

This retrospective correlation study within an academic medical center neurotology practice evaluated 127 patients with vestibular schwannoma observed over time, each with ≥2 MRI scans (367 total) and ≥2 audiograms (472 total). 86 patients had T2-weighted sequences with sufficient resolution for cochlear signal analysis, yielding 348 unique timepoint intervals. The main outcome measure was correlation of the ipsilateral-to-contralateral ratio of whole cochlear T2 signal with hearing outcomes as measured by pure tone average (PTA) and word recognition score (WRS).

RESULTS

Whole cochlear T2 signal ratios did not show a correlation with hearing levels at diagnosis. Change in signal ratio over time showed weak correlation with changes in PTA, but not WRS, over time. Cochlear signal ratio did not precede changes in hearing but did follow changes in both PTA and WRS.

CONCLUSION

Whole cochlear T2 signal ratios were weakly correlated with changes in hearing in patients with observed vestibular schwannoma. The technology of automated segmentation and signal processing holds promise for future evaluation of clinical entities causing cochlear signal changes.

Labyrinthine Fluid Signal Intensity on T2-Weighted MR Imaging in Patients With Vestibular Schwannomas Undergoing Proton Radiotherapy: A Longitudinal Assessment

OBJECTIVE

In vestibular schwannoma patients, a loss of signal intensity (SI) on T2-weighted magnetic resonance imaging (MRI) has been reported within the ipsilateral labyrinth. The purpose of this study was to quantitatively evaluate the occurrence and course of this intensity loss in relation to proton radiotherapy and its possible association with hearing loss.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Patients who received proton therapy for a vestibular schwannoma and underwent at least two high-resolution T2-weighted cisternographic sequence (constructive interference in steady state/fast imaging employing steady-state acquisition/DRIVE) MRIs and audiometry assessments.

MAIN OUTCOME MEASURES

Relative T2 SIs from the vestibules and basal/apical cochlear turns of the labyrinth, bilaterally.

RESULTS

Ninety-five MRI scans from 34 patients were included. The apical turn of the ipsilateral cochlea showed a lower mean cochlear SI than on the contralateral side (±3.5 versus 5.0). The mean relative cochlear SI did not significantly change after proton radiotherapy. The ipsilateral vestibule showed a higher SI than the cochlea. The relative mean cochlear SI was not directly correlated to (the degree of) hearing loss before or after proton radiotherapy, nor did it predict future hearing loss.

CONCLUSION

The relative mean cochlear SI on cisternographic T2-MRI in vestibular schwannoma patients is diminished on the treated side, when compared with the ipsilateral vestibule and the contralateral cochlea/vestibule. The SI of the ipsilateral cochlea does not further decrease after proton radiotherapy and seems to be related to the tumor rather than the therapy. The diminished cochlear SI does not correlate with subsequent loss of hearing.

Cochlear T2 Signal May Predict Hearing Outcomes After Resection of Acoustic Neuroma

OBJECTIVE

Examine the impact of preoperative cochlear Fast Imaging Employing Steady-state Acquisition (FIESTA) and Constructive Interference in Steady State (CISS) signal intensity on hearing outcomes after middle cranial fossa (MCF) resection of acoustic neuroma (AN).

METHODS

Adult patients (≥18 years) who underwent MCF AN resection for hearing preservation (HP) between November 2017 and September 2019 were retrospectively reviewed. All patients had preoperative word recognition score (WRS) ≥50%. HP was defined as postoperative WRS ≥50%. A neuroradiologist blinded to patients' clinical and audiometric outcomes reviewed patients' preoperative magnetic resonance images. Ipsilateral-to-contralateral cochlear FIESTA/CISS signal intensity ratios were determined using hand-drawn regions of interest focused on the cochlear fluid. Preoperative and postoperative pure tone average (PTA) and WRS were reviewed.

RESULTS

Fifty-one patients were reviewed (60.8% female). Mean age was 47 years and mean tumor size 9.2 mm (±3.8). Hearing was preserved in 56.9% (n = 29). FIESTA/CISS signal ratios did not significantly differ between patients with and without HP. Lower FIESTA/CISS signal ratios correlated with greater declines in hearing (r = 0.322, p = 0.011 for PTA; and r = 0.384, p = 0.004 for WRS). On multivariate analysis accounting for tumor size and preoperative PTA/WRS, decreases in FIESTA/CISS signal ratios independently predicted greater declines in hearing by PTA (b = -100.9, p = 0.012) and WRS (b = 76.208), although the latter result was not statistically significant (p = 0.078).

CONCLUSIONS

Cochlear FIESTA/CISS signal intensity may be a predictor of postoperative hearing loss after MCF AN resection. In this cohort, degraded preoperative cochlear FIESTA/CISS signal strongly predicted postoperative hearing loss.Level of Evidence: IV.

Preoperative Sudden Hearing Loss May Predict Hearing Preservation After Retrosigmoid Resection of Vestibular Schwannoma

OBJECTIVES

Describe the effect of preoperative sudden hearing loss (SHL) on likelihood of hearing preservation (HP) after surgical resection of vestibular schwannoma (VS).

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Adult patients (≥18 years) who underwent retrosigmoid VS resection for HP between February 2008 and December 2018 were reviewed. All patients had preoperative word recognition score (WRS) of at least 50%. Similarly, HP was defined as postoperative WRS of more than or equal to 50%. Regression analysis was used to describe the effect of SHL on HP, accounting for tumor size, and preoperative hearing quality.

INTERVENTIONS

All patients underwent retrosigmoid VS resection for HP.

MAIN OUTCOME MEASURES

WRS of at least 50%.

RESULTS

Of 160 patients who underwent retrosigmoid VS resection during the study period, 153 met inclusion criteria. Mean tumor size was 14.0 (±6) mm. Hearing was preserved in 41.8% (n = 64). Forty patients (26.1%) had a history of preoperative SHL. Among 138 patients (90.2%) in whom the cochlear nerve was anatomically preserved during surgery, HP was achieved in 61.8% of those with SHL (21 of 34) and 41.3% of those without SHL (43 of 104) (p = 0.0480). On univariate and multivariate analysis (accounting for tumor size and preoperative hearing quality), SHL was a significant positive predictor of HP (odds ratio 2.292, p = 0.0407 and odds ratio 2.778, p = 0.0032, respectively).

CONCLUSION

In patients with VS and retained serviceable hearing, SHL is an independent predictor of HP after retrosigmoid microsurgical resection when the cochlear nerve is preserved.

Cochleo-facial corridor to the vestibule and fundus of the internal auditory canal through oval window: a minimal invasive and cochlea sparing approach

PURPOSE

This cadaveric work aimed to test the effectiveness of a modified surgical corridor (ExpTSA: expanded transcanal supracochlear approach) developed for anatomic cochlear preservation in selected vestibular schwannoma patients necessitating to perform cochlear implantation for appropriate cases to achieve the best outcome.

METHODS

The ears of 10 cadavers (at mean age 75.70 ± 13.75 years, range 45-92 years) were dissected from the external auditory canal (EAC) to the internal auditory canal by ExpTSA under the guidance of a microscope and endoscope. All stages of the surgical process were recorded step by step and evaluated morphometrically.

RESULTS

The vestibular base was successfully reached in all ears without damaging the cochlear morphology and facial nerve. The vestibular base was 23.33 ± 2.02 mm away from the entrance (external orifice) and 10.26 ± 1.33 mm from the exit (internal orifice) of EAC. The oval window and vestibular base were measured to be 2.94 ± 1.05 mm and 5.87 ± 1.24 mm deep from the facial nerve, respectively. The normal areas of the oval window, the exit and entrance of EAC were found as 2.90 ± 0.81 mm², 42.52 ± 13.66 mm², and 110.73 ± 25.32 mm², respectively. After ExpTSA procedure, the areas of the oval window (11.04 ± 2.83 mm²), the exit (122.45 ± 20.41 mm²) and entrance (167.49 ± 30.94 mm²) of EAC were expanded approximately 280%, 188%, and 50%, respectively.

CONCLUSION

The ExpTSA may be performed for accessing to the vestibule and fundus of IAC for tumor removal of intravestibular schwannoma patients (with or without fundus involvement) with unserviceable hearing, preserving the cochlear morphology.

Predicting Hearing Outcomes in Conservatively Managed Vestibular Schwannoma Patients Utilizing Magnetic Resonance Imaging

OBJECTIVE

Management of small vestibular schwannomas has evolved to where observation with interval imaging is an accepted treatment strategy. Loss of residual hearing is a known complication of observation. Magnetic resonance imaging (MRI) may provide critical information to assist in determining which tumors are at highest risk of hearing loss. We wished to determine what effect fundal cap size and cochlear fluid-attenuated inversion recovery (FLAIR) signal had on the progression of hearing loss in a large cohort of observed subjects.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary academic referral center.

PATIENTS

Three hundred ninety-three adults with a vestibular schwannoma who underwent expectant management with serial audiograms and MRI.

INTERVENTIONS

Audiogram and MRI.

MAIN OUTCOME MEASURES

Hearing outcomes included pure-tone average and word discrimination score (WRS). Cochlear FLAIR signal was measured as a ratio between the affected and nonaffected cochlea. Cerebrospinal fluid fundal cap was measured from the most lateral aspect of the tumor to the fundus of the internal auditory canal.

RESULTS

An increased cochlear FLAIR ratio was associated with a worse initial WRS (p = 0.0001, β=-0.25). A multivariate regression analysis demonstrated the variables fundal cap and initial WRS to significantly predict change in WRS over time. The larger the fundal cap size, the smaller the change in the WRS (p = 0.047, β=-0.35).

CONCLUSIONS

Cerebrospinal fluid fundal cap size predicts the natural history of hearing in vestibular schwannoma patients. The presence of a smaller fundal cap is correlated with a greater risk of progression of hearing loss and should be a variable considered in the management of small vestibular schwannomas.

Current imaging tools for vestibular schwannoma

PURPOSE OF REVIEW

Of the tumors found in the cerebellopontine angle (CPA), vestibular schwannomas are by far the most common. Modern diagnostic imaging enables excellent visualization of the CPA and detection of very small tumors while optimizing patient comfort and time. This review addresses the current imaging tools available for diagnosis of vestibular schwannomas.

RECENT FINDINGS

The current gold-standard imaging study for vestibular schwannomas is a gadolinium-enhanced T1-weighted MRI. The yield of this expensive study is only about 3-4% given the low incidence of vestibular schwannomas, thus there is utility in screening with noncontrast T2-weighted MRI, which is a quicker and more economical study.

SUMMARY

Vestibular schwannomas are best evaluated with gadolinium-enhanced T1-weighted MRI, which can detect tumors as small as 2-3 mm. Recent studies have found that the reported sensitivity and specificity of noncontrast MRI is almost equivalent to that of gadolinium-enhanced T1-weighted MRI. As such, this modality is increasingly being adopted by institutions for both diagnosis and surveillance of vestibular schwannomas and shows promise for broader implementation. Newer protocols, such as FLAIR and DTI may provide additional information and further aid preoperative counseling and surgical planning in the future.