The effects of demyelination in chronic inflammatory demyelinating polyneuropathy (cidp) on neuromuscular properties, muscle quantity and quality
Gilmore KJ, Kimpinski K[1,2], Doherty TJ[1,2,4], Rice CL[1,3]
1. School of Kinesiology, The University of Western Ontario, London, ON, Canada
2. Department of Clinical Neurological Sciences, The University of Western Ontario, London, ON, Canada
3. Department of Anatomy & Cell Biology, The University of Western Ontario, London, ON, Canada
4. Department of Physical Medicine and Rehabilitation, The University of Western Ontario, London, ON, Canada
Introduction: CIDP is an acquired neuropathy of immunological origin. It is characterized by symmetrical weakness in proximal and distal muscles that progresses for greater than 2 months [1,2]. Little is known about the pathophysiology of this disease as it relates to motor impairment. We hypothesize that CIDP patients will have significantly less overall muscle mass with increased fat infiltration, and have reduced motor unit (MU) firing rates compared to healthy controls.
Methods: In 10 patients and 10 age and sex-matched controls, magnetic resonance imaging (MRI) was used to calculate tibialis anterior (TA) muscle volume. Quantitative anatomical measures were acquired using a T1 sequence and muscle quality was assessed by T2 relaxation times using a spin-echo sequence. In addition, MU firing rates were obtained in the TA at 25, 50, 75 and 100% maximal voluntary contraction (MVC) during non-fatiguing isometric contractions.
Results: As a relative percentage of total muscle volume, CIDP patients had significantly less contractile tissue (-28%) and more non-contractile tissue (+60%) than controls. Furthermore, T2 relaxation times were ~39% longer in duration in CIDP. MU firing rates at 25 and 50% MVC were higher in CIDP by ~25%, but rates at 75 and 100% MVC were lower by ~30 and 50% compared to controls.
Conclusion: These results support that disruptions to MU firing properties have negative consequences on muscle. Thus, the utilization of MRI for muscle analysis may provide a better understanding of the impact of neuronal changes in CIDP on muscular characteristics, and motor impairment.
Supported by NSERC
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