Endolymph flow in semicircular canals

Fluidmechanics of the semicircular canals

Semicircular canals are the primary sensor for angular motion. They are part of the vestibular organ which is located in the inner ear.

The semicircular canals are filled with a fluid called the endolymph. Angular movements of the head induce a flow of the endolymph. This flow deflects a flexible gelatinous structure (cupula). The deflection of the cupula triggers nerve signals resulting in the perception of angular motion.

By stiudying the fluiddyamics of the endolymph it can be shown that the deflection of the cupula is nearly proportional to the angular velocity. This proportionality is disturbed by a velocity error. The velocity error grows continuously during a movement with constant angular velocity until it has completely cancelled our perception of angular motion. The velocity error persists even after the angular motion has stopped. It decays only slowly.

We can observe this effect in a simple self-experiment: sit on an office chair, close your eyes and ask a colleague to spin you around several times at constant speed. The perception of angular motion will decrease over time (velocity error). After a sudden stop you will have the impression that you are spinning in the opposite direction (again due to the velocity error).

Top-shelf Vertigo (Benign Paroxysmal Positional Vertigo, BPPV)

Top-shelf vertigo (or BPPV) is a common disorder of the semicircular canals. It causes dizziness, nausea and imbalance. It is symptomatic for BPPV that it is triggered by a specific head movement. The vertigo typically starts a few seconds after the triggering head movement. The vertigo (spinning sensation in the same direction as the preceeding head movement) increases in strenght over 5-10s and then decays slowly (on the order of 10-20s).
It is conjectured that BPPV is caused by particles that are floating freely in the semicircular canals. It can be shown that these particles disturb the endolymph flow in a way that the cupula is deflected a second time after a head movement which is perceived as a vertigo attack.

Therefore, BPPV is related to sedimenting particles in a pipe, a classical problem of fluiddynamics which has been studied already several decades ago in different contexts. It is typical for biofluiddynamics problems that results from other fields of fluiddynamics can be applied successfully.

(click on the picture to animate!)

To improved our understanding of top-shelf vertigo we developed an analytical model which is based on the viscous axial flow of the endolymph and a coupled equation for the particle motion.
This analytical model provides us not only with a detailed understanding of the major mechanisms in top-shelf vertigo, it also yields a set of dimensionless numbers which are an invaluable tool for our further research.
Ongoing research projects attempt to study the mechanisms of top-shelf vertigo in much more detail. In a project supported by the Swiss national science foundation we develop a three-dimensional transient simulation of the endolymph flow in semicircular canals with large spherical particles of finite size.

In a second effort we develop an experiment for a semicircular canal with particles. This scaled-up model of a semicircular canal allows us to study several phenomena related to top-shelf vertigo, e.g., particle trajectories, under well-defined conditions.

Refereed Journal Articles and Conference Papers related to the Current Projects

• Obrist, D., Hegemann S.
  Fluid mechanics of benign paroxysmal
  positional vertigo (BPPV)
  5th Int. Symposium on Turbulence and Shear
  Flow Phenomena TSFP-5, 27-29 August 2007, Munich, 2007.
• Obrist D.
  Fluidmechanics of semicircular canals - revisited
  ZAMP, 2007.
• Obrist, D., Hegemann, S.
  Fluid-particle dynamics in canalithiasis
  J. R. Soc. Interface, 2008.

Abstracts & Posters (conferences without proceedings)

• Hegemann, S., Obrist, D.
  Fluidmechanics of canalithiasis and its clinical application
  24th Barany Society Meeting, 11-14 June 2006, Uppsala.
• Obrist, D., Hegemann, S.
  Endolymph flow in semicircular canals: a model for top-shelf vertigo
  IFD poster gallery, 2007.
• Hegemann, S., Obrist, D.
  Improved fluidmechanic modeling of canalithiasis
  30th ARO Mid-Winter Meeting, 10-15 February 2007, Denver.
• Hegemann, S., Bockisch, C., Obrist, D.
  Ein neues fluidmechanisches Modell für den gutartigen Lagerungsschwindel
  ORL Frühjahrsversammllung, 14.&15. June 2007, Bern.
• Häuselmann, S., Obrist, D., Rösgen, T., Hegemann, S.
  An experimental set-up for the study of BPPV
  SSBE Annual Meeting, 13.&14. September 2007, Neuchâtel.

Student Projects

• Villiger, S.
  Analyse der Zeitschrittrestriktion und Einbau in eines impliziten Zeitintegrationsverfahren in ein Rechenprogramm zur Simulation des Gleichgewichtsorgans im Innenohr
  Seminararbeit, SS 2006
• Insa Marin, R.
  BPPV in the horizontal semicircular canal
  Master's thesis, WS 2006/07
• Wüthrich, B.
  Numerical simulation of the endolymph flow in the vestibular organ
  Semester thesis, WS 2006/07
• Hora, D.
  Simulation of spherical particles in the endolymphatic flow in the semicircular canals
  Semester thesis, SS 2007
  
• Häuselmann, O.
  Experimental study of particle trajectories in a model of the inner ear labyrinth
  Bachelor thesis, SS 2007
• ... click here to find for your own student project!