Numerical simulation of the vestibular system: biomechanics applied to rehabilitation

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Effects of the fibers distribution in the human eardrum: A biomechanical study

Publication . Gentil, Fernanda; Parente, Marco; Martins, Pedro; Garbe, Carolina; Santos, Carla; Areias, Bruno; Branco, Carla; Paço, João; Jorge, Renato Natal

The eardrum separates the external ear from the middle ear and it is responsible to convert the acoustical energy into mechanical energy. It is divided by pars tensa and pars flaccida. The aim of this work is to analyze the susceptibility of the four quadrants of the pars tensa under negative pressure, to different lamina propria fibers distribution. The development of associated ear pathology, in particular the formation of retraction pockets, is also evaluated. To analyze these effects, a computational biomechanical model of the tympano-ossicular chain was constructed using computerized tomography images and based on the finite element method. Three fibers distributions in the eardrum middle layer were compared: case 1 (eardrum with a circular band of fibers surrounding all quadrants equally), case 2 (eardrum with a circular band of fibers that decreases in thickness in posterior quadrants), case 3 (eardrum without circular fibers in the posterior/superior quadrant). A static analysis was performed by applying approximately 3000Pa in the eardrum. The pars tensa of the eardrum was divided in four quadrants and the displacement of a central point of each quadrant analyzed. The largest displacements of the eardrum were obtained for the eardrum without circular fibers in the posterior/superior quadrant.

2016Journal article

Open access

A computational framework to simulate the endolymph flow due to vestibular rehabilitation maneuvers assessed from accelerometer data

Publication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Jorge, Renato Natal

Vertiginous symptoms are one of the most common symptoms in the world, therefore investing in new ways and therapies to avoid the sense of insecurity during the vertigo episodes is of great interest. The classical maneuvers used during vestibular rehabilitation consist in moving the head in specific ways, but it is not fully understood why those steps solve the problem. To better understand this mechanism, a three-dimensional computational model of the semicircular ducts of the inner ear was built using the finite element method, with the simulation of the fluid flow being obtained using particle methods. To simulate the exact movements performed during rehabilitation, data from an accelerometer were used as input for the boundary conditions in the model. It is shown that the developed model responds to the input data as expected, and the results successfully show the fluid flow of the endolymph behaving coherently as a function of accelerometer data. Numerical results at specific time steps are compared with the corresponding head movement, and both particle velocity and position follow the pattern that would be expected, confirming that the model is working as expected. The vestibular model built is an important starting point to simulate the classical maneuvers of the vestibular rehabilitation allowing to understand what happens in the endolymph during the rehabilitation process, which ultimately may be used to improve the maneuvers and the quality of life of patients suffering from vertigo.

2018Journal article

Open access

The free vibrations analysis of the cupula in the inner ear using a natural neighbor meshless method

Publication . Santos, Carla F.; Belinha, J.; Gentil, Fernanda; Parente, Marco; Jorge, Renato Natal

The cupula is a part of the inner ear semi-circular canals that plays an important role in the maintenance of the human balance. In order to understand the dynamic response of the cupula, first it is necessary to obtain its vibration frequencies. A two-dimensional and three-dimensional geometrical model of the cupula was built. Then, a free vibration analysis was performed using two distinct numerical techniques, the finite element method (FEM) and the natural neighbor radial point interpolation method (NNRPIM). Besides the fundamental analysis, other scenarios were studied, aiming to analyze the environment of the cupula (in healthy and pathologic scenarios). The results obtained with the geometrical models show that NNRPIM is capable to deliver results very close with the FEM. Additionally, the NNRPIM formulation possesses a high convergence and acceptable computational costs. This work presents for the first time a computational study on the free vibration analysis of the cupula and shows an alternative numerical technique to calculate with precision the natural frequency of the cupula. The outcomes of this work will allow the development of alternative therapies for cupulolithiasis, which causes severe dizziness.

2018Journal article

Open access