Title: Significance of the spinal curvature in human transcutaneous spinal cord stimulation : a computer modeling study
Language: English
Authors: Müllner-Rieder, Markus 
Qualification level: Diploma
Advisor: Rattay, Frank 
Issue Date: 2015
Number of Pages: 86
Qualification level: Diploma
Spinal cord stimulation (SCS) has been shown to augment gait and reduce spasticity in individuals with spinal cord injury. There are 2 common methods of SCS: epidural SCS, which uses implanted electrodes, and transcutaneous spinal cord stimulation (tSCS), which uses surface electrodes. tSCS is able to stimulate the same neural structures as epidural SCS and was used in multiple studies. These studies used different body positions during stimulation, which showed varying effectiveness in the results. One reason could be the curvature of the spine. Vertebrae have a low conductivity compared to the surrounding tissue, therefore if they move they change the current flow through the spinal canal, which can change the effectiveness of the stimulation. In this thesis, I studied the effect of spinal curvature onto the effectiveness of tSCS using a computer model. A two-step approach was used. First, the potential distribution generated by the stimulation was calculated in the human torso using a volume conductor model. Then the potential is evaluated along nerve fiber trajectories and used as the input for a nerve fiber model. This mathematical model calculates the excitation threshold and the position where an action-potential would occur. This is done for 3 different positions: leaning forward, upright and leaning backward. As geometry, a model of a human torso was created with all anatomical aspects needed for a measurement of the biophysical and neuro-physiological processes in the proximity of the spinal cord. The results show that the current flow spreads up and down when leaning forward, but is more focused downward when being upright or leaning backward. The absolute potential in the cerebro-spinal fluid (CSF) is highest when leaning forward and lowest when leaning backward. This does not affect the excitation thresholds, which are overall higher when leaning forward. It is possible to partially compensate these high thresholds by moving the back electrodes cranial. Compared to other computational studies the results for the upright position are in the same range, therefore the model and the used parameters are adequate. The results suggest that the worst position is leaning forward and the best position is leaning backward, although there is only a small difference between leaning backward and being upright. The position greatly influences the effectiveness of tSCS and should always be taken into account when using it.
Keywords: spinal cord; simulation; stimulation
URI: https://resolver.obvsg.at/urn:nbn:at:at-ubtuw:1-88360
Library ID: AC12315483
Organisation: E101 - Institut für Analysis und Scientific Computing 
Publication Type: Thesis
Appears in Collections:Thesis

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