Effects of functional electrical stimulation in denervated thigh muscles of paraplegic patients mapped with T2 imaging.

Authors:Meyerspeer M1,2, Mandl T1,2, Reichel M2, Mayr W2, Hofer C3, Kern H3, Moser E1,2,4

Source:Magn Reson Mater Phy. 2008 May;21(3):219-26. Epub 2008 Apr 19.

Keywords: High-fieldMRI, T2 mapping, Human muscle, Denervated muscle,
Functional electrical stimulation, Paraplegia, FES

Abstract:

OBJECT: Functional electrical stimulation (FES) for paraplegic patients, with the long-term goal of ultimately restoring muscle function, is associated with several positive effects: improvement of blood circulation, skin condition, peripheral trophism and metabolism, prophylaxis against decubitus ulcer and better physical fitness. Since fibres of denervated muscles (lacking a supplying nerve) need to be activated directly, the fraction of elicited muscle tissue follows the geometric distribution of the electrical field, which can be simulated using electrophysiological computer models. Experimental validation of these results, however, has not yet been established. MATERIALS AND METHODS: We acquired T (2) parameter images using a multislice multi-spin-echo MR sequence before and immediately after FES in nine denervated paraplegic patients and three healthy subjects in order to visualise the geometric distribution of activation by electrically induced muscle stimulation in denervated versus innervated (healthy) thigh muscle. RESULTS AND CONCLUSION: After realigning and normalisation, maps of relative T (2) increase were calculated. The results demonstrate that the spatial distribution of short-term effects of FES of denervated muscle tissue of paraplegic patients who regularly perform FES can be visualised by T (2) parameter images. This may be used to refine models of the electrical field of FES in muscle and fibre activation in the future.

Affiliations:

1 MR Centre of Excellence, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria
2 Center for Biomedical Engineering and Physics, Medical University of Vienna, Vienna, Austria
3 Ludwig Boltzmann Institute of Electrostimulation and Physical Rehabilitation, Department of Physical Medicine,
Wilhelminenspital Vienna, Vienna, Austria
4 Department of Diagnostic Radiology, Medical University of Vienna, Vienna, Austria