FES of long-term denervated muscle validated via 3T-MR

Functional Electrical Stimulation (FES) of patients with flaccid paraplegia and long-term denervated degenerated muscles (DDM) is a new research field with promising results. FES training has many positive clinical effects and despite wide scepticism in trainability of DDM - worldwide unique - meanwhile 8 DDM patients have achieved the goal of standing up with there own leg muscle power in Vienna. The EU-funded project RISE is currently developing a near market version of an FES equipment based on surface electrodes for home use, reviewing and adapting EU regulations and optimizing training protocols.The clinical approach has gathered mostly empirical results concerning the influence of electrode positions or stimulation parameters on training success. For assessment of training progress either integral quantities, like the torque, or secondary effects like increase in cross sectional muscle area (CSA via CT) are used, both of which provide no local information on the immediate effect of FES. A computer-simulation of FES of DDM combines a finite difference electrical model and a muscle-fibre model via a first and second order activation function to determine activated muscle regions. High-field MRI and especially T2-mapping can provide local information about actually activated regions shortly after FES, thus supplying both localised information of the immediate training-effects of FES and for validation and adaptation of current computer models. A validated computer model could predict training effects of different FES-parameters and thus help further optimise efficiency and increase safety of FES training. It is further potentially helpful for the design of electrode configurations, optimisation of stimulation parameters and interpretation of biomechanical and biopsy data. In addition, interleaved non-invasive proton and phosphorus MR spectroscopy at 3 Tesla, developed in a previous FWF-project, allows to follow-up long-term improvements in muscle metabolism after FES, and should improve our understanding of basic physiological and biochemical mechanisms of muscle growth of long-term denervated skeletal muscle. In summary, an innovative combination of techniques and methods should lead to evidence based therapy of patients with flaccid paraplegia and DDM, and help to improve their quality of life significantly.