BPPV is a mechanical disorder caused by the displacement of otolith debris into the semicircular canals. The treatment involves different repositioning maneuvers to bring the debris back into the utricle. This study aims to show how dynamic simulation models based on fluid dynamics and MRI, can help to visualize and understand the movement of the debris within the canals during head movement in 3D as a function of time. The user can define the rotation angle and plane at each step of the maneuver and then the model visualizes the canal and the otoconial movement in 3D. The simulation developed also allows alteration of various parameters like the rotational head acceleration, the duration of each step of the maneuver, the initial position of the otoconial debris in the canal, the size and the number of the particles and fluid dynamics of endolymph. The clod movement is visualized in such a way that it allows a better understanding of the impact and efficacy of various liberation maneuvers and why certain maneuvers might fail when not applied properly in the clinic. The model allows simulation of multi-canal BPPV. In this paper we demonstrate the power of the model applied on the maneuvers of Semont and Yacovino when executed in different ways. The model aims to provide a visual explanation for the need of specific maneuvers for each type of BPPV. The simulator presented here can be used to test the efficacy of existing maneuvers and help in the development of new maneuvers to treat different BPPV variants.

Benign paroxysmal positional vertigo (BPPV) is one of the commonest causes of vertigo. This mechanical inner ear disorder affects the posterior canal, most commonly followed by the horizontal canal.Several different maneuvers have been elaborated over 2 decades for the treatment of horizontal canal BPPV canalithiasis (hc-BPPV-ca) [1]. The most commonly used liberatory maneuvers include the roll maneuver [2], the Gufoni maneuver [3], forced prolonged position [4], and the Zuma maneuvers [5]. In canalithiasis, the free-floating otoconial debris move due to gravitational and, in some of the maneuvers, also inertial forces causing cupular deflection during head

Background and Objectives: Anterior canal BPPV is a rare BPPV variant. Various diagnostic and therapeutic maneuvers have been described for its management. The aim of this study was to use three-dimensional simulation models to visualize otoconial debris movement within the anterior canal during diagnostic tests and different liberatory maneuvers. This can help to optimize existing treatment maneuvers and help in the development of better management protocols.Methods: Based on reconstructed MRI images and fluid dynamics, a 3D dynamic simulation model (as a function of time) was developed and applied. Simulations of the supine head-hanging test for diagnosis of ac-BPPV were studied. Three repositioning maneuvers were simulated: 1) the Yacovino maneuver and its modifications, 2) the reverse Epley maneuver and 3) the short canal repositioning (CRP) maneuver.Results: The simulation showed that the supine head-hanging test is a good test for diagnosis of ac-BPPV affecting both labyrinths and demonstrated why there is no inversion of nystagmus on sitting up. The Yacovino maneuver was seen to be an effective treatment option for ac-BPPV without having to determine the side involved. However, simulations showed that the classical Yacovino maneuver carried a risk of canal switch to the posterior canal. To overcome this risk, a modified Yacovino maneuver is suggested. The reverse Epley maneuver was not an effective treatment. Short CRP is useful in ac-BPPV treatment; however, it requires determination of side of involvement.Conclusion: The 3D simulator of the movement of the otoconial debris presented here can be used to test the mechanism of action and the theoretical efficacy of existing diagnostic tests and maneuvers as well as to develop new treatment maneuvers to optimize BPPV treatment.

Background and ObjectivesThe aim of this study was to show with three-dimensional simulations how the diagnostic supine roll test (SRT) is affected by the initial position of the debris within the horizontal canal (hc) and study the nystagmus patterns on changing the sequence of testing and its impact on the diagnosis of the side of involvement in hc-BPPV.MethodsA 3D dynamic simulation model was developed and applied based on reconstructed MRI images and fluid dynamics. Each semicircular canal was linked to the respective extraocular muscles to visualize nystagmus generated on stimulation of the canal.ResultsThe simulations of hc-canalithiasis showed that the nystagmus pattern seen with the SRT is changed by the initial position of the otolith debris within the canal and the sequence of testing. The debris changes position during SRT so that sequential steps do not start at the initial position as previously assumed. The sequence of performing the SRT steps from the right or left side influences the nystagmus pattern generated: bilateral direction-changing, bilateral direction-fixed, and unilateral nystagmus can be seen in different test conditions. The SRT itself may even reposition the debris out of the canal.Conclusions and Clinical ImplicationsSimulations provide a dynamic tool to study the diagnostic SRT in hc-canalithiasis. Starting the SRT from right or left has a major impact on the test outcome (unlike the Dix-Hallpike maneuver). The findings provide a new interpretation for the results of the SRT. The simulations explain the phenomenon of direction-fixed nystagmus as a logical consequence of starting the SRT with the head turned toward the non-affected side in hc-canalithiasis with debris in the ampullary arm. They also show that unilateral nystagmus seen on SRT indicates canalithiasis of the non-ampullary arm of the side opposite to the side of nystagmus. The generation of bilateral direction-changing, bilateral direction-fixed, and unilateral nystagmus can be the cause of misdiagnoses in terms of the affected side and underlying mechanisms. Finally, a recommendation for a standardized protocol for the sequence of positional tests should be established to ensure uniform interpretation of test results.

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