The headshake enhances oculomotor response to galvanic vestibular stimulation in healthy subjects.

OBJECTIVE: To investigate whether a headshake applied during galvanic vestibular stimulation (GVS) can enhance GVS-induced nystagmus in healthy subjects. METHODS: In nineteen healthy participants, we evaluated an average slow-phase velocity (aSPV) of nystagmus in a head-still and after the headshake conditions, with/out the bitemporal 2 mA GVS. The GVS was applied also with polarity congruent (supporting) or incongruent (suppressing) to any preexisting spontaneous nystagmus. RESULTS: The orientation of GVS-induced nystagmus depended on GVS polarity. In the head-still condition, the GVS-induced nystagmus in 14 subjects (74%) for congruent and in 12 subjects (63%) for incongruent GVS. During headshake, we recorded nystagmus in 16 subjects (84%) for congruent and 15 subjects (79%) for incongruent GVS. The aSPV of congruent GVS-induced nystagmus was higher (p = 0.0003) by 1.33 (SE 0.26) deg/s for headshake compared to head-still condition. The aSPV of incongruent GVS also induced higher nystagmus (p = 0.0014) by 1.24 (SE 0.28) deg/s for the headshake condition. CONCLUSION: Our study adds a new principle to the knowledge of the central processing of a GVS response in healthy subjects. The GVS-safety profile of current up to 2 mA was sufficient to elicit a significant GVS nystagmus response in a head-still position in 63% and after a headshake in 79%. Compared to the GVS head-still condition, a headshake enhanced the GVS-induced nystagmus more than twice. SIGNIFICANCE: The headshake helps to identify GVS-induced nystagmus, which can be weak or absent during the head-still condition.

Binocular video head impulse test: Normative data study.

Introduction: The video head impulse test (vHIT) evaluates the vestibulo-ocular reflex (VOR). It's usually recorded from only one eye. Newer vHIT devices allow a binocular quantification of the VOR. Purpose Aim: To investigate the advantages of simultaneously recorded binocular vHIT (bvHIT) to detect the differences between the VOR gains of the adducting and the abducting eye, to define the most precise VOR measure, and to assess gaze dys/conjugacy. We aimed to establish normative values for bvHIT adducting/abducting eye VOR gains and to introduce the VOR dysconjugacy ratio (vorDR) between adducting and abducting eyes for bvHIT. Methods: We enrolled 44 healthy adult participants in a cross-sectional, prospective study using a repeated-measures design to assess test-retest reliability. A binocular EyeSeeCam Sci 2 device was used to simultaneously record bvHIT from both eyes during impulsive head stimulation in the horizontal plane. Results: Pooled bvHIT retest gains of the adducting eye significantly exceeded those of the abducting eye (mean (SD): 1.08 (SD = 0.06), 0.95 (SD = 0.06), respectively). Both adduction and abduction gains showed similar variability, suggesting comparable precision and therefore equal suitability for VOR asymmetry assessment. The pooled vorDR here introduced to bvHIT was 1.13 (SD = 0.05). The test-retest repeatability coefficient was 0.06. Conclusion: Our study provides normative values reflecting the conjugacy of eye movement responses to horizontal bvHIT in healthy participants. The results were similar to a previous study using the gold-standard scleral search coil, which also reported greater VOR gains in the adducting than in the abducting eye. In analogy to the analysis of saccade conjugacy, we propose the use of a novel bvHIT dysconjugacy ratio to assess dys/conjugacy of VOR-induced eye movements. In addition, to accurately assess VOR asymmetry, and to avoid directional gain preponderance between adduction and abduction VOR-induced eye movements leading to monocular vHIT bias, we recommend using a binocular ductional VOR asymmetry index that compares the VOR gains of only the abduction or only the adduction movements of both eyes.

Head-shaking-induced nystagmus reflects dynamic vestibular compensation: A 2-year follow-up study.

Purpose: We aimed to assess the ability of a head-shaking test (HST) to reflect vestibular compensation in patients after unilateral peripheral vestibular loss and to provide missing evidence and new insights into the features of head-shaking-induced nystagmus (HSN) over a 2-year follow-up. Background: HSN may occur after a prolonged sinusoidal oscillation of the head. HSN is frequently observed in subjects with vestibular function asymmetry; it usually beats toward the functionally intact or "stronger" ear and can be followed by a reversal of its direction. Study design: A prospective observational case-control study. Settings: A tertiary academic referral center. Methods: A total of 38 patients after acute unilateral vestibular loss (22 patients with vestibular neuronitis and 16 patients after vestibular neurectomy) and 28 healthy controls were followed for four consecutive visits over a 2-year period. A complex vestibular assessment was performed on all participants, which included spontaneous nystagmus (SPN), the caloric test, the head-shaking test (HST), the video head impulse test (vHIT), the Timed Up and Go (TUG) test, and the Dizziness Handicap Inventory (DHI) questionnaire. We established the criteria for the poorly compensated group to assess different compensatory behaviors and results. Results: We found a time-related decrease in HSN (ρ < -0.84, p < 0.001) after unilateral vestibular loss. After 2 years of follow-up, HSN intensity in compensated patients reached the level of the control group; TUG and DHI also improved to normal; however, the caloric and vHIT tests remained abnormal throughout all follow-ups, indicating a chronic vestibular deficit. Besides, poorly compensated patients had a well-detectable HSN throughout all follow-ups; TUG remained abnormal, and DHI showed at least a moderate deficit. Conclusions: Our study showed that, after a unilateral peripheral vestibular loss, the intensity of HSN decreased exponentially over time, reflecting an improvement in dynamic ability and self-perceived deficit. HSN tended to decline to the value of the control group once vestibular compensation was satisfactory and sufficient for a patient's everyday life. In contrast, well-detectable HSN in poorly compensated patients with insufficient clinical recovery confirmed the potential of HSN to reflect and distinguish between adequate and insufficient dynamic compensation. HSN could serve as an objective indicator of stable unilateral vestibular loss.

The Relationship between Bone Conduction Hearing Threshold Shifts after Surgery for Chronic Otitis Media with Cholesteatoma According to STAM, EAONO/JOS, and SAMEO-ATO Classifications.

Background: This study focuses on the hearing threshold for bone conduction (BC) after middle-ear surgery. Methods: A total of 92 patients (120 ears) were treated for newly diagnosed chronic otitis media with cholesteatoma (2013−2018). BC was examined at frequencies of 0.5, 1, 2, and 4 kHz prior to and 1 year after surgery. STAM classification for cholesteatoma location, EAONO/JOS for stage, and surgery according to SAMEO-ATO classification were applied. The bone conduction threshold was compared for individual frequencies in patients with occurrence/absence of cholesteatoma in different locations. Results: For the occurrence of cholesteatoma in the attic (A), a statistically significant difference was found at 4 kHz (p < 0.001), in the supratubal recess (S1) at 4 kHz (p = 0.003), and for the mastoid (M) at 0.5 kHz (p = 0.024), at 1 kHz (p = 0.032), and at 2 kHz (p = 0.039). Conclusions: Cholesteatoma location can influence the post-operative hearing threshold for bone conduction.

Enhancement of subarachnoid space during magnetic resonance imaging of endolymphatic hydrops: a case report.

Enhancement of the subarachnoid space after intravenous administration of gadolinium contrast agent is not common. Enhancement usually occurs in pathological conditions that increase the permeability of the blood-cerebrospinal fluid barrier, most notably in meningitis. We herein describe possible subarachnoid enhancement in patients with no apparent effect on the meninges. These patients had clinical signs of Meniere's disease and underwent specific magnetic resonance imaging of the inner ear to possibly visualize endolymphatic hydrops. The endolymphatic space can be noninvasively imaged by intravenous administration of contrast agent, usually at a double dose, 4 hours before the scanning process. During this time, the contrast agent penetrates not only the perilymph but also the subarachnoid space, where the highest concentration occurs after 4 hours according to some studies.

Estimated Vestibulogram (EVEST) for Effective Vestibular Assessment.

BACKGROUND: The availability and development of methods testing the vestibuloocular reflex (VOR) brought a broader view into the lateral semicircular canal (L-SCC) function. However, the higher number of evaluated parameters makes more difficult the specialist's diagnose-making process. PURPOSE: To provide medical specialists, a new diagnostic-graphic tool, Estimated Vestibulogram- EVEST, enabling a quick and easy-to-read visualization and comparison of the VOR test results within the L-SCC. METHODS: The development of EVEST involved 148 participants, including 49 healthy volunteers (28 female and 21 male) and 99 (58 female and 41 male) patients affected by different degrees of peripheral vestibular deficit. The corresponding L-SCC VOR test results, from patients meeting the diagnostic criteria, were used to create the EVEST. RESULTS: Based on the test results, we depicted and calculated the EVEST vestibular function asymmetry (VFA) in all the groups. To assess a feasibility of EVEST to describe a vestibular function deficit, we calculated sensitivity and specificity of VFA using a receiver operating characteristic curve (ROC) and compared it to single tests. In all the tests, we determined the cutoff value as the point with the highest sensitivity and specificity. For discrimination of any vestibular deficit, the VFA with cutoff 6.5% was more sensitive (91%) and specific (98%) than single tests. Results showed that EVEST is a beneficial graphic tool for quick multifrequency comparison and diagnosis of different types of the peripheral vestibular loss. CONCLUSIONS: EVEST can help to easily evaluate various types of peripheral vestibular lesion.