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.

A meshless boundary method for Stokes flows with particles: application to canalithiasis.

We propose to couple the method of fundamental solutions (MFS) to the force coupling method (FCM). The resulting method is an efficient, easy to program, meshless method for flows at low Reynolds numbers with finite-size particles. In such an approach, the flow domain is extended across the solid particle phase, and the flow is approximated by a superposition of singular Stokeslets positioned outside the flow domain and finite-size multipoles collocated with the particle. To improve the efficiency of the coupling, we propose new MFS quadratures for the computation of the volume integrals required for the FCM. These are exact and do not require the expensive evaluation of Stokeslets. The proposed method has been developed in the context of investigations of the fluid dynamics of canalithiasis, that is, a pathological condition of the semicircular canals of the inner ear. Numerical examples are presented to illustrate the applicability of the method.