High-frequency pseudo-hypofunction of the superior semicircular canal dehiscence syndrome: a vHIT - oVEMP dissociation explained by hydrodynamic energy loss

Leonardo Manzari; Nicola Ferri; Marco Tramontano

doi:10.1007/s00405-026-10347-0

High-frequency pseudo-hypofunction of the superior semicircular canal dehiscence syndrome: a vHIT - oVEMP dissociation explained by hydrodynamic energy loss

Eur Arch Otorhinolaryngol. 2026 Jun 1. doi: 10.1007/s00405-026-10347-0. Online ahead of print.

Authors

Leonardo Manzari¹, Nicola Ferri², Marco Tramontano^{3

4}

Affiliations

¹ MSA ENT Academy Center, Cassino (FR), Italy.
² Translational Rehabilitation Sciences Group, Department of Biomedical and Neuromotor Sciences (DIBINEM), Alma Mater Studiorum University of Bologna, Bologna, 40138, Italy.
³ Translational Rehabilitation Sciences Group, Department of Biomedical and Neuromotor Sciences (DIBINEM), Alma Mater Studiorum University of Bologna, Bologna, 40138, Italy. marco.tramontano@unibo.it.
⁴ Unit of Occupational Medicine, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, 40138, Italy. marco.tramontano@unibo.it.

PMID: 42228120
DOI: 10.1007/s00405-026-10347-0

Abstract

Background: Superior semicircular canal dehiscence syndrome (SCDS) produces a wide spectrum of vestibular and auditory abnormalities due to the presence of a "third mobile window." While enhanced otolith-mediated responses are well recognized, the behavior of high-frequency semicircular canal function remains debated. Many patients show reduced superior canal vestibulo-oculomotor reflex (VOR) gains despite preserved or exaggerated utricular responses.

Objective: To investigate the relationship between dynamic semicircular canal responses assessed by video Head Impulse Test (vHIT) and otolith responses assessed by oVEMPs in people with superior semicircular canal dehiscence.

Methods: Fifty-three patients with SCDS underwent full vestibular testing including vHIT of all six semicircular canals, cervical and ocular vestibular-evoked myogenic potentials (cVEMPs, oVEMPs) to 500-Hz BCV, and high-frequency oVEMPs to 4,000-Hz stimuli.

Results: Superior semicircular canals showed the largest VOR gain reductions, with the left anterior (LA) canal most affected (mean gain 0.86 ± 0.18). Bilateral SCDS exhibited significantly lower gains than unilateral SCDS, with mean LA gain falling below the functional threshold (0.68 ± 0.14). In contrast, all patients demonstrated enhanced utricular responsiveness, including increased 500-Hz oVEMP amplitudes and consistent 4-kHz N10 responses.

Conclusion: Our findings confirm the presence of high-frequency oVEMP hyperresponsiveness, yet with a VOR pseudo-hypofunction due to a loss of high-frequency mechanical energy through the dehiscence, which diminishes the utricular vortex and cupular deformation. This frequency-dependent hydrodynamic dissociation provides a comprehensive mechanistic framework for interpreting vestibular test batteries in SCDS. Combined assessment with vHIT and high-frequency oVEMPs offers a powerful, physiologically grounded diagnostic approach.

Keywords: Semicircular canal dehiscence; Third window syndrome; Transient vestibular system; Vestibular hair cells; Video head impulse test; kHz vestibular evoked myogenic potentials.