Eye movements; what a vestibular specialist needs to know

Re-Visiting Rotation Chair Tests keyote

Introduction

The vestibular analyzer varies in different vertebrates, both in terms of size and shape. The differences in shape are dictated by the specificity of the movement of the respective animal.

In this presentation, we will make a literature review and show our clinical experience in a patient with a totally obliterated lateral semicircular canal (changed shape) and still functioning vestibular perception.

Materials and methods.

A patient who, after a traffic accident, suffered a head injury with subsequent stenosis of the external auditory canal. The secondary iatrogenic cholesteatoma that developed led to vertigo attacks during pressure (fistula test). The patient was referred for surgical treatment - mastoidectomy. Intraoperatively after removal of the cholesteatoma, the lateral semicircular canal was totally obliterated.

Results.

Postoperatively, the patient had preserved vestibular function (hypofunction) during a rotatory test for the lateral semicircular canal and preserved (normal) function of the remaining semicircular canals.

Discussion.

The author of the presentation will present his theory about this phenomenon, illustrate the process of functioning of the receptor cells in the membranous ampulla of the lateral semicircular canal in a totally obliterated lateral semicircular canal and explain the hypofunction during the rotatory test of the lateral semicircular canal.

Diagnosis of vestibular migraine beyond the published diagnostic criteria

This session will explore essential differences in vestibular rehabilitation strategies tailored to the underlying etiology of bilateral vestibular hypofunction. Disorders such as CANVAS, Cogan’s syndrome, and ototoxicity present with distinct pathophysiological mechanisms that impact compensatory potential and require individualized rehabilitation protocols. Understanding these distinctions is crucial for optimizing clinical outcomes.

Vestibular Rehabilitation: Expectations and fulfillment

Description: This keynote revisits the question of a primary vestibular cortex in humans. Through a PET paradigm based on natural vestibular stimulation, consistent activation in medial Heschl’s gyrus has been demonstrated, challenging the longstanding belief that vestibular input is only processed in multimodal association areas. Limitations of fMRI in vestibular research will also be addressed, including magnetic field-induced vestibular stimulation and gradient noise, which may confound signal interpretation. Finally, a double dissociation study using the same PET methodology is presented, comparing cortical activation in individuals with bilateral vestibular loss and normal hearing versus those with profound hearing loss and preserved vestibular function. This classical neuroimaging approach strengthens the case for functional separation of auditory and vestibular processing.

Outcome Objectives:

After this session, participants will be able to:

1. Summarize PET-based evidence for vestibular-related activity in medial Heschl’s gyrus
2. Reflect on the overlap and distinction between auditory and vestibular cortical networks
3. Recognize the impact of scanner-related vestibular stimulation on fMRI interpretations
4. Understand the rationale behind double dissociation paradigms in sensory neuroscience
5. Consider methodological and conceptual implications for future vestibular research

Structure of the Session (30 min):

5 min: Introduction – the vestibular paradox and historical context

10 min: PET findings – natural stimulation and cortical response

10 min: fMRI limitations – field effects and interpretative constraints

5 min: Perspectives – dissociation data and future directions

Key References:

1. Devantier L, Hansen AK, Mølby-Henriksen JJ, Christensen CB, Pedersen M, Magnusson M, Ovesen T, Borghammer P. PET visualized stimulation of the vestibular organ is localized in Heschl’s gyrus. Hum Brain Mapp. 2020;41(1):185–193.
2. Devantier L, Hansen AK, Mølby-Henriksen JJ, Christensen CB, Lildal T, Pedersen M, Magnusson M, Borghammer P, Ovesen T. PET visualized stimulation of the vestibular organ in Menière’s disease. Front Neurol. 2020 Jan 28;12:00019.
3. Devantier L, Hansen AK, Mølby-Henriksen JJ, Pedersen M, Borghammer P, Ovesen T, Magnusson M. Cortical activity during an attack of Menière’s disease. Front Neurol. 2021 Jul 22;12:669390.
4. Horsager J, Knudsen K, Sommerauer M, et al. Mapping cholinergic synaptic loss in Parkinson’s disease: an 18F-FEOBV PET case–control study. Brain. 2022;145(5):1690–1704.
5. Devantier L et al. Dissociating auditory and vestibular cortical responses: a PET study using a double dissociation design.(unpublished, 2025)
6. Devantier L et al. Magnetic field-induced vestibular stimulation in fMRI: methodological implications for vestibular neuroimaging.(unpublished, 2025)

Background: The vestibular system has traditionally been considered unique among the senses for lacking a defined primary cortical area. Using PET imaging during natural vestibular stimulation, metabolic activity has been observed in medial Heschl’s gyrus. To disentangle auditory and vestibular contributions, a double dissociation design was applied: one group with bilateral vestibular loss and intact hearing, and another with profound hearing loss but preserved vestibular function. This allows for sensory-specific mapping of cortical activation. Additionally, methodological data from fMRI highlight how scanner-related vestibular stimulation may influence results. Reduced cholinergic activity in Heschl’s gyrus, as reported in Parkinson’s disease, may further support the clinical relevance of this area in balance processing.

Abstract

The otolith organs are essential components of the vestibular system, contributing to the perception of linear acceleration and head position. This round table will discuss otolith function from normal to various clinical disorders characterized by impaired otolith precision. The discussion includes basic insights into the neurophysiological mechanisms underlying otolith processing and the diagnostic procedures in detecting subtle dysfunctions. Different clinical presentations, including isolated otolith dysfunction, will be elaborated. Emerging strategies for otolith malfunction rehabilitation will be also discussed. Understanding otolith complexity and its impact on vestibular precision is crucial for diagnosis, targeted intervention, and improved management of vestibular disorders, ultimately enhancing patient quality of life.