Three-dimensional biomechanical model of benign paroxysmal positional vertigo.

A morphologically descriptive 3-canal mathematical model was developed to quantify the biomechanical origins of gravity-dependent semicircular canal responses under pathological conditions of canalithiasis and cupulolithiasis--conditions associated with the vestibular disorder benign paroxysmal positional vertigo (BPPV). The model describes the influence of displaced calcium carbonate debris (particles) located within the labyrinth on the time-dependent responses of the ampullary organs. The particles were modeled as spheres free to move in the canal lumen (canalithiasis) or adhered to a cupula (cupulolithiasis). The model predicts canal responses to the diagnostic Dix-Hallpike maneuver, and to a modified Epley canalith repositioning (CRP) treatment. Results for canalithiasis predict activation latencies and response magnitudes consistent with clinical observations during the Dix-Hallpike maneuver. The magnitude of the response evoked by the Dix-Hallpike test was primarily due to the total weight of the particles while the latency to peak response was due to the time required for the stone to move from the ampulla to the posterior apex of the canal. Results further illustrate the effectiveness of the Epley CRP in repositioning the particles and relieving the symptoms of the canalithiasis type of BPPV.