Does a “Fundal Fluid Cap” Predict Successful Hearing Preservation in Vestibular Schwannoma Resections Via the Middle Cranial Fossa Approach?

Hearing Preservation Outcomes in 230 Consecutive Patients with Small Vestibular Schwannomas Treated with Microsurgery

OBJECTIVE

To evaluate hearing preservation (HP) outcomes for patients with small sporadic vestibular schwannomas (VS) who elect to undergo microsurgical resection.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary single-academic institution.

PATIENTS

Individuals 18 years or older with small sporadic VS (≤15 mm) who underwent microsurgical resection from 2018 to 2023.

INTERVENTIONS

Microsurgical resection via a middle cranial fossa (MCF) or retrosigmoid (RS) approach.

MAIN OUTCOME MEASURES

Postoperative HP (word recognition score ≥ 50%) and facial nerve function.

RESULTS

Of the 230 consecutive patients with small sporadic VS who elected to undergo microsurgical resection, hearing was preserved in 61% of patients. When stratified by tumor size, patients with tumors ≤10 mm had a 72% hearing preservation rate. On multivariate analysis, the most important prognostic factors for hearing preservation were the presence of preoperative vertigo (OR, 0.33; 95% CI, 0.17-0.52) and tumor size. Patients with tumors between 0 to 5 mm and 5.1 to 10 mm had 3.62 higher odds (95% CI, 1.39-9.4) and 2.52 higher odds (95% CI, 1.30-4.9) of hearing preservation, respectively, when compared to patients with tumors that were larger than 10 mm. At the time of last follow-up, a House-Brackmann (HB) 1 or 2 was maintained in 95% (n = 218) patients.

CONCLUSIONS

Microsurgical resection for patients with small VS is associated with good hearing preservation and excellent facial nerve outcomes. Because larger tumor size portends poorer hearing outcomes, for patients who elect to undergo microsurgical resection for hearing preservation, proactive surgical intervention when tumors are ≤10 mm should be considered to increase the likelihood of hearing preservation.

Reduced Cochlear MRI Signal and Hearing Outcomes in Conservatively Managed Vestibular Schwannoma Patients

OBJECTIVE

This study aimed to determine if hypointense cochlear magnetic resonance imaging (MRI) constructive interference in steady-state (CISS) signal correlates with hearing outcomes in conservatively managed vestibular schwannoma (VS) patients.

STUDY DESIGN

Retrospective review of 657 cases from 1992 to 2020.

SETTING

Tertiary academic referral center.

PATIENTS

A retrospective review was performed to identify conservatively managed VS patients with appropriate baseline MRI, audiology, and at least 12-month audiological follow-up. Patients were excluded if they progressed to surgery or radiotherapy in less than 12 months, bilateral tumors, or surgery on the contralateral ear.

INTERVENTION

Conservatively managed patients with CISS imaging studies and audiology testing.

MAIN OUTCOME MEASURES

Primary outcome measure change in pure-tone average (PTA) and word recognition score (WRS). Secondary outcome measures tumor size, presence of lateral fluid cap, or cystic changes.

RESULTS

A total of 92 individuals (47% male, 58 ± 11.6 yr) met the inclusion criteria, with 36 (39%) of patients demonstrating abnormal cochlear CISS signal. At baseline, abnormal cochlear CISS signal was associated with higher intracanalicular (IC) length (7.9 versus 6.6 mm, p = 0.0177) and lower WRS (55.7 versus 78.8 dBHL, p = 0.0054). During follow-up, individuals with abnormal cochlear CISS signal had significantly higher PTA (62.4 versus 46.4 dBHL, p = 0.0010). After adjusting for baseline covariates, abnormal cochlear CISS signal was consistently associated with a greater increase in PTA of 8.3 dBHL (95% confidence interval, 2.9-13.7; p = 0.0032) from baseline when compared with the normal group.

CONCLUSIONS

Abnormal cochlear signal on MRI CISS sequences is associated with poorer hearing outcomes in conservatively managed VS patients.

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.

Machine Learning to Predict Hearing Preservation After Middle Cranial Fossa Approach for Sporadic Vestibular Schwannomas

OBJECTIVE

Predict hearing preservation after middle cranial fossa approach for vestibular schwannomas.

STUDY DESIGN

Application of machine learning algorithms, including classification and regression trees and random forest models to observational data.

SETTING

Single-tertiary referral center.

PARTICIPANTS

Patients (n = 144) with a previously untreated sporadic vestibular schwannoma who underwent microsurgical resection by middle cranial fossa approach between November 2017 and November 2021.

INTERVENTIONS

Middle cranial fossa approach.

MAIN OUTCOME AND MEASURES

Hearing preservation, defined by postoperative word recognition score of 50% or greater and pure tone average below 50 dB HL or less than 10% reduction in word recognition score. Model performance was evaluated with classification accuracy in an independent validation sample. Variable importance for the random forest model is reported according to entropy, a measure of mean decrease in model accuracy incurred by excluding each variable from the model.

RESULTS

Hearing preservation was achieved in 60% of patients (86 of 144) overall. The classification and regression tree model identified preoperative pure tone average with a cut point of 30 dB HL, and more posterior tumor position to be the most important prognostic features for hearing preservation. Model accuracy was 0.68. The random forest model demonstrated perfect accuracy (1). Baseline pure tone average, word recognition score, and anteroposterior tumor position were among the most influential features for hearing preservation prediction.

CONCLUSION

Machine learning algorithms have the potential for accurate prediction of hearing preservation rates after middle fossa approach for vestibular schwannomas at a single institution. These models have the capacity for continued refinement with ongoing addition of data.

Analysis of Hearing Preservation in Middle Cranial Fossa Resection of Vestibular Schwannoma

OBJECTIVE

Describe the effect of preoperative hearing on the likelihood of hearing preservation after middle cranial fossa (MCF) approach for resection of vestibular schwannoma (VS) and the effect of hearing preservation on disease-specific quality of life (QOL).

STUDY DESIGN

Retrospective chart review.

SETTING

Academic tertiary care skull base surgery program.

PATIENTS

Sixty three adult patients with preoperative word recognition score (WRS) ≥50% who underwent MCF resection of VS between 2017 and 2020.

INTERVENTIONS

All patients underwent MCF VS resection with attempted hearing preservation.

MAIN OUTCOME MEASURES

Hearing preservation (postoperative WRS ≥50%), hearing-related Penn Acoustic Neuroma Quality of Life (PANQOL) score.

RESULTS

Sixty three patients with mean age 47.4 (±9.6) years and tumor size 11.5 (±0.5) mm were analyzed. Hearing was preserved (+HP) and lost (-HP) in 37 (58.7%) and 26 (41.3%) patients, respectively. Preoperatively, pure tone average audiometry was significantly lower among the +HP group (20.0 dB) versus -HP (31.0 dB, p < 0.003). WRS was higher among +HP versus -HP (94% vs. 84%, respectively; p < 0.002). Linear regression showed that intra- versus extra-canalicular tumor location, sudden hearing loss history, fundal fluid cap thickness, and tumor size had no relationship to hearing preservation outcomes. When evaluating postoperative QOL data (n = 37) hearing-related PANQOL score differed between +HP and -HP (t35 = 2.458, p = 0.0191) groups.

CONCLUSIONS

In this cohort of patients undergoing MCF resection of VS, rates of HP were higher for patients with excellent preoperative hearing. Postoperatively, +HP patients reported improved hearing-related PANQOL scores compared to -HP patients.

The Effect of Tumor Size on Likelihood of Hearing Preservation After Retrosigmoid Vestibular Schwannoma Resection

OBJECTIVES

1) Describe the effect of tumor size on the likelihood of hearing preservation after retrosigmoid approach for resection of vestibular schwannoma (VS).2) Describe the effect of preoperative hearing status on the likelihood of hearing preservation.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Adult (18 years or older) patients underwent retrosigmoid VS resection and postoperative audiometry between 2008 and 2018 and had a preoperative word recognition score (WRS) of at least 50%. Patients with a history of neurofibromatosis 2, radiation, or previous resection were excluded.

INTERVENTIONS

All patients underwent retrosigmoid VS resection with attempted hearing preservation.

MAIN OUTCOME MEASURES

WRS of at least 50%.

RESULTS

Data from 153 patients were analyzed. Mean age was 50.8 (±11.3) years and mean tumor size 14 (±6) mm. Hearing was preserved and lost in 64 (41.8%) and 89 (58.2%) patients, respectively. Hearing preservation rates were higher for intrameatal tumors than for tumors with extrameatal extension (57.6% versus 29.4%, p = 0.0005). On univariate and multivariate regression analysis, tumor size (per mm increase) was a negative predictor of hearing preservation (odds ratio [OR] 0.893, p = 0.0002 and 0.841, p = 0.0005, respectively). Preoperative American Academy of Otolaryngology-Head & Neck Surgery Hearing Class was also predictive of hearing preservation (p = 0.0044). Class A hearing (compared with class B hearing) was the strongest positive risk factor for hearing preservation (OR 3.149, p = 0.0048 and 1.236, p = 0.0005, respectively).

CONCLUSION

Small tumor size and preoperative class A hearing are positive predictors of hearing preservation in patients undergoing the retrosigmoid approach for VS resection.

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.

Fundal Fluid Cap Is Associated With Hearing Preservation in the Radiosurgical Treatment of Vestibular Schwannoma

OBJECTIVE

To evaluate the relationship between fundal fluid and hearing outcomes after treatment of vestibular schwannoma (VS) with Gamma Knife radiosurgery (GKRS).

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary neurotology referral center.

PATIENTS

Patients treated with GKRS for vestibular schwannoma between March 2007 and March 2017 were considered for this study. Exclusion criteria included pretreatment pure-tone average (PTA) >90 dB, neurofibromatosis type II, history of previous surgical resection, and follow-up less than 1 year.

MAIN OUTCOME MEASURE(S)

Hearing function was assessed both by preservation of serviceable hearing and by preservation of baseline hearing (≤20 dB change in PTA) after GKRS. Hearing preservation comparisons were made between groups of patients with and without a fundal fluid cap.

RESULTS

Patients with a fundal cap had significantly higher rates of baseline hearing preservation (≤20 dB change in PTA) according to Kaplan-Meier survival analysis of all 106 patients (p = 0.006). By the 3rd year posttreatment, 70.9% of patients with a fundal cap had maintained a ≤20 dB change in PTA, while only 43.6% of patients without a fundal fluid cap achieved this outcome (p = 0.004).

CONCLUSIONS

Fundal fluid present on pretreatment magnetic resonance imaging is predictive of improved baseline hearing preservation rates in patients undergoing GKRS for vestibular schwannoma when considering all patients with PTA ≤90 dB. Fundal fluid cap presence may serve as a favorable prognostic indicator to help set hearing expectations and guide patient selection efforts.

Relationship of a "Fundal Fluid Cap" and Vestibular Schwannoma Volume: Analysis of Preoperative Radiographic Findings and Outcomes

OBJECTIVE

To evaluate the relationship between radiographic fundal fluid cap in the lateral internal auditory canal, preoperative clinical characteristics, and postoperative outcomes in patients with vestibular schwannoma who underwent microsurgical excision.

STUDY DESIGN

Retrospective chart review.

SETTING

Academic tertiary referral center.

PATIENTS

Thirty-six consecutive patients (mean age 49.4 yr [range 29-74]) who underwent microsurgical vestibular schwannoma excision.

INTERVENTIONS

Microsurgical excision.

MAIN OUTCOME MEASURES

Linear fundal fluid size and tumor size calculated using volumetric analysis were measured on preoperative magnetic resonance imaging, and correlated to hearing status and postoperative facial nerve function.

RESULTS

Mean fundal fluid size was 2.18 mm (range 0-7.32). Mean tumor volume was 5.58 cm (range, 0.210-40.3 cm). Short- and long-term postoperative House-Brackmann scores were 2.4 and 1.4, respectively. Fundal fluid size was associated with tumor volume (rs = 0.488, p = 0.003) but not preoperative hearing status (p = 0.333). The presence of fundal fluid and larger tumor volumes were statistically associated with poorer short-term and long-term postoperative facial nerve function (p < 0.05).

CONCLUSIONS

Radiographic fundal fluid size is correlated to tumor volume.