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To evaluate pre- and post-operative semicircular canal function in patients with vestibular schwannoma (VS) by the video Head Impulse Test (vHIT). Nineteen patients with VS who underwent surgery were enrolled in this study. The gain in vestibulo-ocular reflex (VOR) and the degree of scatter in catch-up saccades were examined pre- and post-operatively for the semicircular canals in VS patients. Ten of 19 cases (52.6 %) with VS were defined as demonstrating both superior vestibular nerve (SVN) and inferior vestibular nerve (IVN) impairment from the results of pre-operative vHIT. Hearing level and subjective vestibular symptoms showed significant correlations with pre-operative semicircular canal function. Compared to pre-operative vHIT results, VOR gains within 1 month after surgery were significantly reduced in all three canals; however, significant differences had disappeared in the anterior and posterior semicircular canals at 6 months after surgery. Cases of unknown origin had a significantly greater reduction in posterior semicircular canal function after surgery compared with those with disease of IVN origin. As vHIT could evaluate pre-operative vestibular nerve impairment, post-operative VOR gain reduction and the degree of vestibular compensation, semicircular canal function evaluated by vHIT provides a good deal of useful information regarding VS patients undergoing surgery compared to caloric testing, and vHIT should be performed pre- and post-operatively for patients with VS. [ABSTRACT FROM AUTHOR]

• In unoperated vestibular schwannoma, ipsilesional canals show decreased vestibulo-ocular reflex (VOR) gain and increased saccade amplitude and frequency. • One week after unilateral vestibular deafferentation lesioned canal gains drop by 0.22–0.35 and first saccade frequency and amplitudes increase by 37% and 2.9°. • The video head-impulse test excitation/dis-facilitation VOR asymmetry is less for the intact posterior canal than for the other canals. To examine the vestibulo-ocular reflex (VOR) and compensatory-saccades before and after complete unilateral vestibular deafferentation (UVD). Forty patients were studied before and after surgery for vestibular or facial schwannoma using the video head-impulse test (vHIT) and multivariable regression. Prior to UVD (median(IQR), 14(58.4) days), the average VOR-gain towards the lesioned -ear was lower than in normal for all semicircular canals (lateral, anterior, posterior: 0.69, 0.72, 0.49). One-week after UVD (5(3.0) days) VOR gains were further reduced (0.22, 0.37, 0.27), however, within one-year after UVD (171(125.0) days) the lesioned- ear VOR gains had slightly increased (+0.08, +0.11, +0.03), maximally for the anterior-canal. After UVD, the VOR gain asymmetry (gain towards minus away from intact-ear) was lower for the intact posterior-canal plane (0.56, 0.56, 0.22). For the lesioned canals, the frequency and amplitude of the first compensatory-saccade increased from 61–93% and 1.9–3.6° pre-surgery, to 98–99% and to 3.1–5.9° one-week post-surgery and remained unchanged over one-year; second saccade frequency and amplitude decreased over the same timespan. After UVD the high-acceleration VOR for the intact posterior-canal plane is more symmetrical than the other canals. First compensatory-saccades adapt within one week and subsequently change only marginally. Saccade compensation from surgical UVD is near complete by one-week. [ABSTRACT FROM AUTHOR]

• Cervical and ocular vestibular evoked myogenic potentials (cVEMPs, oVEMPs) in almost all cases of vestibular involvement can help both in diagnosis and in prognosis. • More research is needed to understand the applications of both c- and oVEMPs, especially the latter. • A significant percentage of published data have neglected one or more vital VEMP parameters. Cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs respectively) are now used by an increasing number of laboratories to evaluate otolith inner ear function and their pathways through the central nervous system. However, the literature is incomplete or unclear as to what information both c- and oVEMPs can add beyond what a good clinical examination can provide, and what other paramedical tests can provide also, and the present review aims to clarify what is known so far. The following review will describe what is known with regards to both c- and oVEMPs and their use. MEDLINE (accessed by PubMed, years 1994–2018) was searched with the following string: ("vestibular evoked myogenic potentials" [all fields]). Only articles published in English were evaluated. Both c- and oVEMPs are useful not only for confirming the presence of superior semicircular canal dehiscence (SSCD), but also for confirming the presence of acoustic neuromas when MRI is not available, bilateral vestibulopathies, inferior vestibular neuritis and vestibular dysfunction in inherited neuropathies. Further work is required, especially with respect to oVEMPs. The usefulness of both c- and oVEMPs goes beyond the confirmation of SSCDs, and is useful in many clinical cases. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The function of the semicircular canal receptors and the pathway of the vestibulo-ocular-reflex (VOR) can be diagnosed with the clinical head impulse test (cHIT). Recently, the video head impulse test (vHIT) has been introduced but so far there is little clinical experience with the vHIT in patients with peripheral vestibular disorders. The aim of the study was to investigate the horizontal VOR (hVOR) by means of vHIT in peripheral vestibular disorders. Methods: Using the vHIT, we examined the hVOR in a group of 117 patients and a control group of 20 healthy subjects. The group of patients included vestibular neuritis (VN) (n =52), vestibular schwannoma (VS) (n =31), Ménière''s disease (MD) (n =22) and bilateral vestibulopathy (BV) (n =12). Results: Normal hVOR gain was at 0.96±0.08, while abnormal hVOR gain was at 0.44±0.20 (79.1% of all cases). An abnormal vHIT was found in VN (94.2%), VS (61.3%), MD (54.5%) and BV (91.7%). Three conditions of refixation saccades occurred frequently in cases with abnormal hVOR: isolated covert saccades (13.7%), isolated overt saccades (34.3%) and the combination of overt and covert saccades (52.0%). Conclusions: The vHIT detects abnormal hVOR changes in the combination of gain assessment and refixation saccades. Since isolated covert saccades in hVOR changes can only be seen with vHIT, peripheral vestibular disorders are likely to be diagnosed incorrectly with the cHIT to a certain amount. [Copyright &y& Elsevier]

Purpose/objective(s): Diffusion-weighted (DW) imaging detects cellular changes. Loss of tumor cells post radiosurgery results in alteration in the Cellular density and thus changes in apparent diffusion coefficients (ADCs). Low ADC values represent a higher tumor cellularity, a higher tumor-grade and may even be a marker for a higher tumor activity. Purpose of the study is to investigate the clinical usefulness of ADC values for evaluating VSs and to assess the correlation of DW imaging measurements with radiosurgical effects on the tumors.Materials/methods: The authors conducted a retrospective evaluation involving 36 patients harboring solid (28 pts.) or cystic vestibular schwannomas (8 pts.) who underwent single fraction Linac based SRS. The patients underwent serial MR imaging, including DW imaging, before SRS and at 6mo. intervals thereupon following the procedure. The ADCs were calculated from echo-planar DW images, and mean ADC values were compared at each follow-up. To minimize the effect of diffusion anisotropy, an average of the values obtained for the 3 diffusion directions was calculated to provide the trace of the diffusion tensor. Data were analyzed using a t-test to compare the mean ADC values obtained before & after SRS.Results: The mean follow-up period in this study was 32.5 months (range 16 -56 months). Imaging studies demonstrated a reduction in tumor volume in 22 patients (61.3%) and tumor growth arrest in 11 patients (33%). There was tumor enlargement at 18, 36, and 42 months in the remaining 3 patients (8.3%). The mean ADC value before SRS for all solid VSs was 1.2 ± 0.17 × 10-3 mm2/second, which significantly increased 6 months after SRS and continued to increase with time (P = 0.0076). The mean ADC value for treated solid tumors as of the last mean follow-up of 36 months (range 18-60 months) was 1.92 ± 0.26 × 10-3 mm2/second (range 1.60-2.7 × 10-3 mm2/second), which was significantly higher than that before SRS (P = 0.0001). Tumor volumes were positively related to ADC values (P = 0.03). The mean ADC value before SRS for all cystic VSs was 2.09 ± 0.24 × 10-3 mm2/second (range 1.80-2.58 × 10-3 mm2/second). The mean ADC value for treated cystic tumors as of the last mean follow-up of 38 months (range 18-48 months) was 1.9 ± 0.42 × 10-3 mm2/second. In 3 patients harboring solid VSs, the tumor enlarged after SRS but the ADC values were higher than those before SRS.Conclusion: ADC changes precede the real change in tumor size detected on routine follow-up MR images. ADC values of solid tumors significantly increased, even before a change in tumor volume was evident and should be incorporated in VS routine MR imaging post SRS.Author Disclosure: V. Shankar: None. V. Sai Shreya: None. R. Kumar: None. C. Haritha: None. A.K. Karthikayan: None. R. Adhityan: None. P. Bhavya: None. H. Vyas: None. A. Bhange: None. [ABSTRACT FROM AUTHOR]

Abstract: The vestibulo-ocular reflex (VOR) was studied to examine the utility of off-vertical axis rotation (OVAR) in the diagnosis of acoustic neurinoma. Subjects were sinusoidally rotated with eyes open in complete darkness at frequencies of 0.4 and 0.8Hz with a maximum angular velocity of 60°/s at either earth-vertical axis rotation (EVAR) or OVAR. Thirteen patients with acoustic neurinomas were investigated. Results showed that VOR gain during OVAR at 0.8Hz and in a 30° nose-up position in patients with internal auditory canal tumors was significantly less than the gain measured during EVAR. The VOR gain measured from all patients (including those with tumors extending to the cerebellopontine angle) was not significantly different when the patients were subjected to EVAR and OVAR. These observations were possibly due to superior vestibular nerve dysfunction. We concluded that certain stimulating parameters—patient''s nose tilted up 30°; sinusoidal OVAR at 0.8Hz and 60°/s maximum angular head velocity—were useful for evaluating vestibular function in patients suffering from an acoustic neurinoma located within the internal auditory canal. [Copyright &y& Elsevier]