Ocular torsion induced by Coriolis stimulation.

OBJECTIVE: The present study aimed to observe and analyze the ocular movements induced by Coriolis stimulation (eccentric pitch while rotating: PWR) that induces Coriolis forces on the vestibular apparatus of healthy human individuals. METHODS: A total of 31 healthy subjects participated in the study. Eccentric PWR was performed on 27 subjects, by pitching the participants' heads forward and backward at an angle of 30° each on an axis parallel and 7 cm below inter-aural axis, at a frequency of 0.5 Hz while on a chair rotating at a constant angular velocity of 97.2°/s on the earth-vertical axis. Ocular movements during stimulation were recorded using three-dimensional video-oculography. As a subsidiary analysis, 0.5 Hz head roll tilt was used as another stimulus that also induced torsional ocular movements. The forces induced on the vestibular apparatus, and phases of ocular torsion against the stimulus were calculated from the observed data. RESULTS: In the Coriolis stimulation during rightward yaw rotation, a rightward ocular torsion of 4.8° on average, was observed when the head pitched forward, and the direction of ocular torsion reversed when the head pitched backward. During leftward yaw rotation, these relationships were reversed with an average amplitude of 4.7° The phase of ocular torsion preceded that of Coriolis force by 0.2 s during rightward rotation and 0.14 s during leftward rotation. There were no significant differences in amplitude or phase between the directions of rotation. The phase lead of 0.5 Hz roll-tilt was significantly smaller than that of Coriolis stimulation (p < 0.01). CONCLUSION: Coriolis stimulation induced a specific pattern of ocular torsion, where its direction and phase suggested that the mechanism likely involved both the otolith and semicircular canals. Further studies may provide a clue to the magnitude of the otolith and semicircular canal contributions.

Sustained deviation of torsional eye position associated with transient semicircular canal stimulation.

BACKGROUND: Vestibular stimulation causes postural unsteadiness accompanied by a sensation of tilt. AIMS/OBJECTIVES: The mechanism of the sensation of tilt needs to be assessed by accurate calculation of the rotational axis of torsional eye position under various vestibular stimulations. MATERIAL AND METHODS: Twenty-two healthy subjects participated in the study. Thirteen subjects underwent bilateral vestibular stimulation by on-axis yaw rotation under various head positions, and eighteen subjects underwent unilateral vestibular stimulation by caloric irrigation under various head positions. Listing's Plane was plotted for the eye movement data obtained by three-dimensional video-oculography. RESULTS: The offset of Listing's Plane showed sustained deviation of torsional eye position that was more prominent in head positions that stimulated lateral semicircular canals more than vertical semicircular canals. There was a less prominent and directionally reversed offset in head positions that stimulated vertical canals more than lateral semicircular canals. CONCLUSION AND SIGNIFICANCE: The sustained torsional eye position was validated by accurate assessment using Listing's Plane. The mechanism behind the deviation may be due to a combination of multiple anatomical components within the vestibular apparatus, with potentially stronger influence from lateral semicircular canals.

Quantitative analysis and correlative evaluation of video-oculography, micro-computed tomography, and histopathology in Pendrin-null mice.

Patients with SLC26A4 mutations exhibit highly variable hearing loss and vestibular dysfunction. Although Slc26a4 mutant mice similarly exhibit vestibular deficits, including circling behavior, head tilting, and torticollis, the underlying pathogenesis of the vestibular symptoms remains unclear, hindering its effective management for patients with SLC26A4 mutations. In this study, we evaluated the equilibrium function using the inspection equipment, which can record eye movements against rotational, gravitational, and thermal stimulations. Moreover, we correlated the degree of functional impairment with the morphological alterations observed in Slc26a4Δ/Δ mice. The rotational stimulus and ice water caloric tests revealed considerable impairment of the semicircular canal, while the tilted gravitational stimulus test showed a severe functional decline of the otolithic system in Slc26a4Δ/Δ mice. Generally, the degree of impairment was more severe in circling Slc26a4Δ/Δ mice than in non-circling Slc26a4Δ/Δ mice. In non-circling Slc26a4Δ/Δ mice, the semicircular canal function was normal. Micro-computed tomography results showed enlargement of the vestibular aqueduct and bony semicircular canals but no correlative relationship between the severity of the caloric response and the size of bony labyrinths. Giant otoconia and a significant decrease in total otolith volume in the saccule and utricle were observed in Slc26a4Δ/Δ mice. However, the giant otoconia were not overly dislocated in the bony otolithic system and ectopic otoconia were absent in the semicircular canal. The number and morphology of the utricular hair cells in Slc26a4Δ/Δ mice were not significantly reduced compared to those in Slc26a4Δ/+ mice. Collectively, we can conclude that vestibular impairments are mainly associated with otoconia formation and morphology rather than hair cell degeneration. In addition, severe disturbances of semicircular canals cause circling behavior in Slc26a4Δ/Δ mice. Our comprehensive morphological and functional assessments apply to mouse models of other genetic diseases with vestibular impairment.

Cholesteatoma has an altered microbiota with a higher abundance of Staphylococcus species.

Objective: To compare the microbiota between cholesteatoma and chronic suppurative otitis media (COM) and to identify potential pathogens that explain the relevant phenotypes of cholesteatoma. Study Design: Prospective cohort study. Methods: Surgical specimens collected from 20 cholesteatomas and nine COMs were treated to dissolve biofilms and subjected to 16S ribosomal RNA (rRNA) gene sequencing and amplicon sequence variant-level analysis for microbiota profiling and quantitative comparison. Correlations between the relative abundance of potential pathogens and the volume of the primary resected cholesteatomas were examined. Results: Differences in bacterial composition (beta diversity) were observed between cholesteatomas and COM (p = .002), with a higher abundance of Staphylococcus in cholesteatomas than in COM (p = .005). Common genera in the external auditory canal (EAC) flora, such as Staphylococcus, Corynebacterium, and Cutibacterium, were predominant in both cholesteatoma and COM; Staphylococcus aureus and Pseudomonas aeruginosa were increased in both diseases compared with the EAC flora. Furthermore, coagulase-negative staphylococci (CoNS) were more abundant in cholesteatomas than in COM (p = 0.002). Linear discriminant analysis coupled with effect size measurements (LEfSe) identified four CoNS as potential biomarkers for cholesteatoma. The relative abundance of S. aureus, a potential pathogen, was positively correlated with cholesteatoma volume (r = .60, p = .02). Conclusion: The microbiota of cholesteatoma and COM originated from EAC flora, but the bacterial composition was largely altered. Our results suggested that S. aureus infection is involved in cholesteatoma progression. Level of Evidence: 3b.

Enhanced fallopian canal as a potential marker for temporal bone vasculitis.

OBJECTIVES: This study aimed to test the hypothesis that contrast-enhanced 3D MRI with gradient-echo sequences (CE-3D-GRE) can detect signs of vasculitis in the fallopian canal, which may cause otologic involvement, in four patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). METHODS: CE-3D-GRE acquired at 3.0 Tesla was performed on four patients diagnosed with granulomatosis with polyangiitis or eosinophilic granulomatosis with polyangiitis, at onset or relapse of the disease, and in remission. Clinical correlations between otologic symptoms and radiological findings were examined for each patient. Furthermore, signal intensity of the mastoid segment of the fallopian canal was compared between the ears with active disease (n = 3) and those in remission or without vasculitis (n = 3). RESULTS: Intense enhancement in the tympanic and mastoid segments of the fallopian canal was associated with development of external otitis, otitis media, and sensorineural hearing loss, and was unrelated to the presence of facial paresis. Maximal intensity projection images visualized the close relationship between the enhanced fallopian canal and middle ear inflammation. The findings were absent in remission. Signal intensity of the mastoid segment of the fallopian canal was higher in ears with active disease than in normal ears (P < .001) and decreased to normal levels during remission (P = .597). CONCLUSION: CE-3D-GRE can demonstrate vasculitis in the temporal bone, reflecting disease activity and the severity of otologic manifestations, including cochlear involvement, in AAV patients. Intense enhancement of the fallopian canal on CE-3D-GRE can be a potential marker for vasculitis of the temporal bone. LEVEL OF EVIDENCE: 5.