Peripheral Vestibular System Disease in Vestibular Schwannomas: A Human Temporal Bone Study

Does Location of Intralabyrinthine Vestibular Schwannoma Determine Objective and Subjective Vestibular Function?

BACKGROUND AND OBJECTIVE

The incidence of intralabyrinthine schwannomas is increasing, and a growing attention is given to the detrimental effects on hearing function. On the contrary, the vestibular profile of intralabyrinthine vestibular schwannomas (VSs) is still not well understood. We aimed to investigate and report the observed relationships between the intralabyrinthine location of the schwannomas and objective and subjective vestibular profile of the patients.

METHODS

Retrospective cohort study of 20 consecutive individuals with sporadic intralabyrinthine schwannomas and grouped according to the intralabyrinthine location of the schwannomas. Vestibular testing consisted of the video head impulse test of all three semicircular canals, the caloric test, cervical and ocular vestibular evoked myogenic potentials, and the dizziness handicap inventory. A nonparametric unpaired t test was performed to compare groups, and Fisher's exact test was used for categorical data.

RESULTS

The median video head impulse test gains (lateral, anterior, posterior) were 0.40, 0.50, and 0.75 for intravestibular schwannomas and 0.93, 1.52, and 0.91 for intracochlear schwannomas ( p = 0.0001, p = 0.009, p = 0.33), respectively. Caloric unilateral weakness had a median of 100% for intravestibular schwannomas and 14% for intracochlear schwannomas ( p = 0.0001). The mean dizziness handicap inventory was 21 for intravestibular schwannomas and 1 for cochlear schwannomas ( p = 0.02). There were no significant differences in vestibular evoked myogenic potentials according to intralabyrinthine location.

CONCLUSION

By both objective and subjective measures, intralabyrinthine schwannomas with an intravestibular component has significantly worse vestibular function than schwannomas with purely cochlear involvement.

The significance of programed cell death-ligand 1 expression in vestibular schwannoma

BACKGROUND

The association between programed cell death-ligand 1 (PD-L1) and tumor-infiltrating lymphocytes (TILs) in vestibular schwannoma (VS) has been investigated in a few studies. These published studies report a difference in the PD-L1 positivity rate in malignant peripheral nerve sheath tumors. We examined PD-L1 expression and lymphocyte infiltration in patients with VS who had undergone surgical resection and investigated the association between PD-L1 expression and clinicopathological features.

METHODS

The expression of PD-L1, CD8, and Ki-67 in 40 VS tissue specimens was investigated using immunohistochemistry, and a clinical review of the patients was performed.

RESULTS

Of the 40 VS samples, 23 (57.5%) were positive for PD-L1 and 22 (55%) were positive for CD8. No significant differences in age, tumor size, pure-tone audiometry, speech discrimination, or Ki-67 expression were observed between patients in the PD-L1-positive and PD-L1-negative groups. A higher level of CD8-positive cell infiltration was observed in PD-L1-positive tumors than in PD-L1-negative tumors.

CONCLUSION

We demonstrated that PD-L1 was expressed in VS tissues. Although no correlation was identified between clinical characteristics and PD-L1 expression, the association between PD-L1 and CD8 was confirmed. Thus, additional research on targeting PD-L1 is necessary to improve immunotherapy for VS in the future.

[Vestibular schwannomas - baseline and progress diagnostics]

Vestibular (vestibulocochlear) schwannomas are rare, benign schwannomas of the cerebellopontine angle, the internal auditory canal, or the inner ear. They can occur with or without clinical symptoms. The most common symptoms are unilateral or side-differentiated hearing loss with or without tinnitus and balance disorders. Initial symptomatology is nonspecific in the basic functional diagnosis, raising the question of when a hearing or balance disorder should be thought of as a differential diagnosis of vestibular schwannoma and what diagnostic pathway is appropriate. This concerns not only the confirmation of the diagnosis and the recording of all dysfunctions of the involved cranial nerves in the initial basic diagnostics, but also the procedure in the course and follow-up diagnostics - especially in patients who are subject to an observation strategy. Today, imaging alone is no longer sufficient for differentiated and individualized patient counseling. Due to the increasing detection of smaller tumors on MRI and the growing proportion of nearly asymptomatic patients, a shift in thinking from pure imaging monitoring to a detailed analysis of auditory and vestibular function is timely. In this educational article, diagnostic pathways for a sufficient patient consultation will be compiled. Ultimately, functional examination techniques from follow-up and progression diagnostics will also be included.

Analysis of semicircular canal function as evaluated by video Head Impulse Test in patients with vestibular schwannoma

OBJECTIVE

The aim of the present study was to investigate the factors influencing semicircular canal function as evaluated by video Head Impulse Test (vHIT) in patients with vestibular schwannoma.

METHODS

Twenty-four patients with untreated vestibular schwannoma underwent vHIT examination. The correlations between semicircular canal function and factors including age, tumor size, disease duration and hearing loss were evaluated.

RESULTS

The functions of all three semicircular canals on the affected side evaluated by vHIT were significantly lower than those on the unaffected side. Although there were no significant correlations between semicircular canal function and age, tumor size or disease duration, a negative significant correlation between vestibulo-ocular reflex (VOR) gain as evaluated by vHIT and hearing loss was observed.

CONCLUSIONS

From the results of the relationship between hearing loss and VOR gain, the damage to the audio and vestibular systems in patients with VS may be correlated. As it has been suggested that tumor size was not a significant factor in the VOR gain evaluated by vHIT, multifactorial causes rather than the simple compression of the vestibular nerves alone may be related to the dysfunction of the semicircular canals in patients with vestibular schwannoma.

Brainstem hyperintensity in patients with vestibular schwannoma is associated with labyrinth signal on magnetic resonance imaging but not vestibulocochlear tests

OBJECTIVES

Focal hyperintensity in the dorsal brainstem (HDB) has been described in large cerebellopontine angle tumours and is thought to represent vestibular nuclei degeneration, but its functional significance has not been thoroughly investigated. Our aim was to analyse its relationship to imaging characteristics of the tumour and inner-ear structures and to vestibulocochlear functional tests.

METHODS

We retrospectively reviewed 54 patients with a histological diagnosis of vestibular schwannoma (VS). Magnetic resonance imaging tumour characteristics (size, cystic composition and distance from the cochlear aperture), signal intensity ratio of the cochlea and vestibule in fluid-attenuated inversion recovery (FLAIR) and fast imaging employing steady-state acquisition (FIESTA)/fast spin-echo imaging with variable flip angles (CUBE) and vestibulocochlear function tests (audiometry, auditory brainstem response (ABR) and video head impulse testing (vHIT)) were obtained. Statistical analyses were performed to evaluate their relation to focal HDB.

RESULTS

Focal HDB was found in 22% of VS. It was significantly associated with large (p < 0.001) and cystic (p = 0.004) tumours and also with tumours located further from the cochlear aperture (p = 0.039). The signal intensity ratio of the cochlea on FLAIR was higher in patients with HDB (p < 0.014), but this difference was not observed in FIESTA/CUBE (p = 0.981). Audiometry, ABR and vHIT results did not significantly differ in patients with HDB, but ABR results were worse in patients with higher cochlear signal intensity on FLAIR sequences (p = 0.026).

CONCLUSIONS

Focal HDB in patients with VS was associated with increased signal intensity ratio of the cochlea on FLAIR in patients with VS but not directly to the results of vestibulocochlear function tests.

Optimized preoperative determination of nerve of origin in patients with vestibular schwannoma

In vestibular schwannoma (VS) patients hearing outcome and surgery related risks can vary and depend on the nerve of origin. Preoperative origin differentiation between inferior or superior vestibular nerve may influence the decision on treatment, and the selection of optimal treatment and counselling modalities. A novel scoring system based on functional tests was designed to predict the nerve of origin for VS and was applied to a large number of consecutive patients. A prospective, double blind, cohort study including 93 patients with suspected unilateral VS was conducted at a tertiary referral centre. Preoperatively before tumor resection a functional test battery [video head-impulse test (vHIT) of all semicircular canals (SCC)], air-conducted cervical/ocular vestibular evoked myogenic potential tests (cVEMP, oVEMP), pure-tone audiometry, and speech discrimination was applied. Sensitivity and specificity of prediction of intraoperative finding by a preoperative score based on vHIT gain, cVEMP and oVEMP amplitudes and asymmetry ratios was calculated. For the prediction of inferior vestibular nerve origin, sensitivity was 73% and specificity was 80%. For the prediction of superior vestibular nerve origin, sensitivity was 60% and specificity was 90%. Based on the trade-off between sensitivity and specificity, optimized cut-off values of - 0.32 for cVEMP and - 0.11 for oVEMP asymmetry ratios and vHIT gain thresholds of 0.77 (anterior SCC), 0.84 (lateral SCC) and 0.80 (posterior SCC) were identified by receiver operator characteristic curves. The scoring system based on preoperative functional tests improves prediction of nerve of origin and can be applied in clinical routine.

Comparison of test results from two separate video head impulse test systems in a cohort of patients diagnosed with a unilateral vestibular schwannoma

PURPOSE

Video head impulse testing (vHIT) is a relatively new technology enabling evaluation of vestibular function. The aim of this study was to compare the test results from two separate vHIT systems in a group of patients diagnosed with a unilateral vestibular schwannoma (VS) with regards to sensitivity, specificity and inter-examiner differences.

METHODS

Forty-two patients were examined with two separate vHIT systems: EyeSeeCam^® (system A) and ICS Impulse^® (system B), by one of two examiners. All six semicircular canals (SCCs) were tested under standardized conditions, and strict criteria were set up for post-test interpretation.

RESULTS

With the majority of test parameters, the two test systems were in agreement. Vestibular deficits were found in 40.5% (system A) to 45% (system B) of patients with a VS on the tested side; corresponding to a positive predictive value (PPV) of 86.4% (system B) to 94.4% (system A). The specificity was 97.6% for system A and 92.9% for system B. An overall agreement between the two vHIT systems measured as kappa was computed to be 0.61. There were no significant inter-examiner differences. When testing the vertical SCCs, a tendency of too high mean gain values was seen with system A but not with system B.

CONCLUSION

In patients with unilateral VS, vHIT is a test with moderate sensitivity and high specificity in regard to identification of a vestibular deficit. There were no significant differences in test results between the two vHIT systems.

Vestibular Migraine Following Radiosurgery for Vestibular Schwannoma

Vestibular schwannoma (VS) is associated with dizziness and vertigo during all stages of treatment. This report describes a patient who presented with a one-year history of intermittent motion sickness, dizziness, headache, imbalance, and nausea. MRI showed a right-side VS in the cerebellopontine angle and internal auditory canal. The patient elected to undergo Gamma Knife radiosurgery for treatment. Within two to three months, she continued to experience recurring dizziness, vertigo, neck stiffness, and head pressure. She was referred for neurotology evaluation, which led to a diagnosis of vestibular migraine (VM). Her vestibular reflexes were intact. Subsequently, she was treated with diet modification and low-dose venlafaxine. She reported dramatically improved dizziness and vertigo symptoms at six-month follow-up. VM is a very common cause of dizziness that should always be included in the differential diagnosis, even in VS patients.

Audiovestibular Loss of Function Correlates in Vestibular Schwannomas

OBJECTIVES

The aim of the present study was to investigate the relationships between tumor size, hearing, and vestibular outcomes in patients with vestibular schwannomas (VSs).

MATERIALS AND METHODS

Adult patients (n=124) with unilateral extrameatal VS prior to surgery were included in the study. This was a retrospective cohort study of preoperative audiovestibular investigations including audiometry, discrimination test, caloric test, cervical vestibular evoked myogenic potential (c-VEMP), and ocular vestibular evoked myogenic potential (o-VEMP).

RESULTS

The difference between lesioned and non-lesioned ear was significant for all audiovestibular outcomes. The mean caloric deficit was 74%. No tumor sided o-VEMPs were elicited. Caloric deficit correlated with hearing loss measured with pure tone average and discrimination score. c-VEMP deficit was significantly associated with severe hearing loss and larger tumors.

CONCLUSION

The presence of VS leads to a significant deterioration of audiovestibular function in all objective measures. Caloric test and o-VEMPS are sensitive though unspecific measures of VSs. Increasing tumor size is not directly associated with hearing loss and only somewhat to vestibular deficit. However, audiovestibular findings are correlated.