The document describes a finite element model of a vagus nerve stimulator. The model was built using COMSOL CAD software to simulate the electric potential generated by a helical cathode and anode placed around a modeled vagus nerve. The model allows over a dozen parameters to be varied and solves faster than models built with third party CAD software. Slice plots and contour plots show the electric potential distribution within the nerve fascicles during stimulation.

1. Vagus Nerve Stimulation
Finite Element Model
Kris Carlson
Arle Lab Med Device Consulting Group
BIDMC/Harvard Medical School
November 2015

2. The Vagus Nerve
• Stimulator is implanted near the larynx for seizure control
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3. Finite Element Model Features
– Geometry built with COMSOL CAD, not 3rd party
CAD program
• Meshes and solves faster than with 3rd party CAD
• Can do longer time dependent studies
• Can do broader parameter sweeps
– Over a dozen parameterized variables are easily
changed
– Thin layers and contact impedance solved
programmatically
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4. Finite Element Model
Vagus nerve embedded in ambient medium
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Finite element analysis
software: COMSOL Multiphysics

5. Finite Element Model
Closeup of helical cathode (top) and anode (bottom)
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6. Finite Element Model
Mesh with mesh quality legend
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7. Finite Element Model
Mesh – View into center of nerve
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8. Finite Element Model
Electric potential – mid-cathode – 2.25 mA
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9. Finite Element Model
Multislice plot of electric potential
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10. Finite Element Model
Contour plot of electric potential on fascicles
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11. Finite Element Model
Electric potential on recurrent laryngeal fascicle
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12. Finite Element Model
Slice plots of electric potential in fascicles at cathode and anode
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13. Finite Element Model
Electric potential in fascicles between cathode and anode
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14. Finite Element Model
Slice plots of electric potential in fascicles at cathode
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15. Finite Element Model
Electric potential along axon in superficial epineurium (left) and
recurrent laryngeal fascicle (right)
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