Quantitative analysis of benign paroxysmal positional vertigo fatigue under canalithiasis conditions.
In our daily life, small flows in the semicircular canals (SCCs) of the inner ear displace a sensory structure called the cupula which mediates the transduction of head angular velocities to afferent signals. We consider a dysfunction of the SCCs known as canalithiasis. Under this condition, small debris particles disturb the flow in the SCCs and can cause benign paroxysmal positional vertigo (BPPV), arguably the most common form of vertigo in humans. The diagnosis of BPPV is mainly based on the analysis of typical eye movements (positional nystagmus) following provocative head maneuvers that are known to lead to vertigo in BPPV patients. These eye movements are triggered by the vestibulo-ocular reflex, and their velocity provides an indirect measurement of the cupula displacement. An attenuation of the vertigo and the nystagmus is often observed when the provocative maneuver is repeated. This attenuation is known as BPPV fatigue. It was not quantitatively described so far, and the mechanisms causing it remain unknown. We quantify fatigue by eye velocity measurements and propose a fluid dynamic interpretation of our results based on a computational model for the fluid-particle dynamics of a SCC with canalithiasis. Our model suggests that the particles may not go back to their initial position after a first head maneuver such that a second head maneuver leads to different particle trajectories causing smaller cupula displacements.
Institute of Fluid Dynamics, ETH Zurich, 8092 Zurich, Switzerland. Electronic address: boselli@ifd.mavt.ethz.ch.
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Boselli
Institute of Fluid Dynamics, ETH Zurich, 8092 Zurich, Switzerland. Electronic address: kleiser@ifd.mavt.ethz.ch.
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Kleiser
Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zurich, 8092 Zurich, Switzerland; Department of Neurology, University Hospital Zurich, 8092 Zurich, Switzerland; Department of Ophthalmology, University Hospital Zurich, 8092 Zurich, Switzerland. Electronic address: Chris.Bockisch@usz.ch.
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Bockisch
Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zurich, 8092 Zurich, Switzerland. Electronic address: Stefan.Hegemann@usz.ch.
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Hegemann
Institute of Fluid Dynamics, ETH Zurich, 8092 Zurich, Switzerland. Electronic address: obrist@ifd.mavt.ethz.ch.
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Obrist
D065635:Benign Paroxysmal Positional Vertigo; D003198:Computer Simulation; D005133:Eye Movements; D005221:Fatigue / Q000503:physiopathology; D006801:Humans; D008953:Models, Anatomic; D009759:Nystagmus, Pathologic / Q000503:physiopathology*; D012665:Semicircular Canals / Q000503:physiopathology*; D013997:Time Factors; D014717:Vertigo / Q000503:physiopathology*
BPPV; Canalithiasis; Endolymph flow; Force Coupling Method; Method of Fundamental Solutions; Nystagmus; Semicircular canals (SCCs)