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Sarcolemmal depolarization in sporadic inclusion body myositis assessed with muscle velocity recovery cycles |
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| Institution: | 1. Centre of Research in Myology, Sorbonne Université, INSERM, Association Institut de Myologie, UMRS 974, 75013 Paris, France;2. Department of Internal Medicine and Clinical Immunology, Pitié-Salpêtrière University Hospital, DHU I2B, AP-HP, INSERM, UMR 974, 75103 Paris, France;3. Department of Neuropathology, Charité – Universitätsmedizin Berlin, 10117 Berlin, Germany;1. Sydney Medical School, University of Sydney, Sydney, Australia;2. Royal Prince Alfred Hospital, Sydney, Australia;3. The George Institute for Global Health, University of New South Wales, Sydney, Australia;4. Ryde Hospital, Sydney, Australia;5. Royal North Shore Hospital, Sydney, Australia;1. Department of Rheumatology, Charité – Universitätsmedizin Berlin, Berlin, Germany;2. Department of Neuropathology, Charité – Universitätsmedizin Berlin, Charitéplatz 1 / Virchowweg 15 (int.) Berlin, Germany;3. Department of Radiology, Charité – Universitätsmedizin Berlin, Berlin, Germany;4. Private Practice of Rheumatology, Radebeul, Saxony, Germany |
| Abstract: | ObjectiveTo study patients with sporadic inclusion body myositis (sIBM) with muscle velocity recovery cycles (MVRC) to assess muscle membrane excitability, pathophysiological mechanisms and potential biomarkers of this disorder.MethodsMVRC were recorded from 20 individuals with sIBM from tibialis anterior (TA) and rectus femoris (RF) muscles. Excitability parameters were compared with MVRC data obtained from 22 normal controls >50 years.ResultsMuscle relative refractory period was prolonged in both TA (6.4 ms vs 4.4 ms, P < 0.001) and RF (7.1 ms vs 3.9 ms, P < 0.001) of sIBM affected muscle when compared to controls. Early supernormality was reduced in both TA (3.6% vs 8.8% P = 0.001) and in RF (mean 5.4% vs 13% P < 0.001). Late supernormality was only decreased significantly in sIBM affected TA (1.8% vs 3.6% P = 0.001) but not in RF. No consistent correlations between MVRC parameters and clinical markers of sIBM disease severity were found.ConclusionThe resting sarcolemmal muscle membrane potential of sIBM muscle is depolarized relative to that of normal controls, which may be related to intramuscular amyloid deposition in sIBM.SignificanceSarcolemmal depolarization may play a role in muscle dysfunction and weakness observed in sIBM patients. |
| Keywords: | Inclusion body myositis Muscle velocity recovery cycle Resting membrane potential Sarcolemma Depolarization DAP"} {"#name":"keyword" "$":{"id":"k0035"} "$$":[{"#name":"text" "_":"depolarizing after-potential EMG"} {"#name":"keyword" "$":{"id":"k0045"} "$$":[{"#name":"text" "_":"electromyography ENMC"} {"#name":"keyword" "$":{"id":"k0055"} "$$":[{"#name":"text" "_":"European Neuromuscular Congress ESN"} {"#name":"keyword" "$":{"id":"k0065"} "$$":[{"#name":"text" "_":"early supernormality IBMFRS"} {"#name":"keyword" "$":{"id":"k0075"} "$$":[{"#name":"text" "_":"IBM functional rating scale ISI"} {"#name":"keyword" "$":{"id":"k0085"} "$$":[{"#name":"text" "_":"inter-stimulus interval IWCI"} {"#name":"keyword" "$":{"id":"k0095"} "$$":[{"#name":"text" "_":"IBM weakness composite index LSN"} {"#name":"keyword" "$":{"id":"k0105"} "$$":[{"#name":"text" "_":"late supernormality MFAP"} {"#name":"keyword" "$":{"id":"k0115"} "$$":[{"#name":"text" "_":"multi-fiber action potential MRRP"} {"#name":"keyword" "$":{"id":"k0125"} "$$":[{"#name":"text" "_":"muscle relative refractory period MVRC"} {"#name":"keyword" "$":{"id":"k0135"} "$$":[{"#name":"text" "_":"muscle velocity recovery cycle RF"} {"#name":"keyword" "$":{"id":"k0145"} "$$":[{"#name":"text" "_":"rectus femoris sIBM"} {"#name":"keyword" "$":{"id":"k0155"} "$$":[{"#name":"text" "_":"sporadic inclusion body myopathy TA"} {"#name":"keyword" "$":{"id":"k0165"} "$$":[{"#name":"text" "_":"tibialis anterior 5XLSN"} {"#name":"keyword" "$":{"id":"k0175"} "$$":[{"#name":"text" "_":"additional late supernormality with 5 conditioning stimuli XLSN"} {"#name":"keyword" "$":{"id":"k0185"} "$$":[{"#name":"text" "_":"additional late supernormality with 2 conditioning stimuli |
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