Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Frank Berenpas (Donders series 452)

20 November 2020

Promotor: prof. dr. A. Geurts
Co-promotors: dr. V. Weerdesteyn, dr. N. van Alfen

Active neuroprosthesis for people with drop foot after stroke: Gait, muscle and motor nerve

Drop foot is a common walking impairment in people after stroke. A drop foot is caused by muscle weakness of the foot elevators and/or spasticity of the ankle plantarflexors. Usually this drop foot is treated with an ankle-foot orthosis. However, ankle-foot orthosis may be unpleasant to wear and are therefore often rejected by the patient. With functional electrical stimulation (FES) of the common peroneal nerve the foot elevators can be activated and as such FES can serve as a method to prevent foot drop in people with stroke.The aim of this thesis was to investigate the long-term effects of implantable FES of the common peroneal nerve on gait, muscle and motor nerve in people with drop foot after stroke. We found that although participants preferred use of the implantable system over their ankle-foot orthosis the metabolic energy cost of walking was not reduced with implantable FES use. However, we did find improvements in gait quality with implantable FES, as knee stability, ankle push-off and propulsion were improved compared to walking with ankle-foot orthosis. These advantages of FES on gait quality could particularly benefit balance and gait in situations were adaptation of the gait pattern is needed. Indeed, it was shown that people with stroke had a greater capacity to avoid suddenly dropped obstacles or make continuous stepping adjustments when they walked with implantable FES compared to walking with ankle-foot orthosis. Long-term stimulation of the common peroneal nerve did lead to improvements in muscle architecture of the stimulated muscles but no improvements were found in functioning of the lower or upper motor neurons.