A Bickerstaffe1, J P van Dijk2, A Beelen3, M J Zwarts4, F Nollet5. 1. Department of Rehabilitation, Academic Medical Center (AMC), Postbus 22660, 1100 DD Amsterdam, The Netherlands. Electronic address: a.bickerstaffe@amc.uva.nl. 2. Radboud University Nijmegen Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Department of Neurology/Clinical Neurophysiology, Postbus 910, 6500 HB Nijmegen, The Netherlands; Epilepsy Centre Kempenhaeghe, Postbus 61, 5590 AB Heeze, The Netherlands. Electronic address: dijkh@kempenhaeghe.nl. 3. Department of Rehabilitation, Academic Medical Center (AMC), Postbus 22660, 1100 DD Amsterdam, The Netherlands. Electronic address: j.a.beelen@amc.nl. 4. Epilepsy Centre Kempenhaeghe, Postbus 61, 5590 AB Heeze, The Netherlands. Electronic address: ZwartsM@kempenhaeghe.nl. 5. Department of Rehabilitation, Academic Medical Center (AMC), Postbus 22660, 1100 DD Amsterdam, The Netherlands. Electronic address: f.nollet@amc.nl.
Abstract
OBJECTIVE: To investigate whether strength decline in post-polio syndrome (PPS) results from excessive distal axonal degeneration of enlarged motor units. METHODS: We assessed changes over 10 years in isometric quadriceps strength, mean motor unit action potential (MUAP) size, root mean squared (RMS) amplitude, and level of interference (LOI) in 47 patients with PPS and 12 healthy controls, using high density surface EMG. At baseline, all patients had symptomatic quadriceps dysfunction, evidenced by transmission defects on single-fibre EMG. RESULTS:MU size and strength declined significantly by 20% and 15%, respectively in patients with PPS. Those with the largest initial MU sizes exhibited the greatest losses of mean MU size (27%) and proportional decreases in quadriceps strength (23%). Initial strength, change in LOI and change in RMS amplitude together explained 35% of the variability in strength changes in patients. MU size of controls did not change, although they lost 29% strength. CONCLUSIONS:MU size and strength declined concomitantly in a homogeneous cohort of patients with PPS and quadriceps dysfunction. SIGNIFICANCE: This long term follow-up study provides evidence that size diminution of enlarged MUs combined with a reduced number of active MUs contributes to the gradual strength decline in PPS.
RCT Entities:
OBJECTIVE: To investigate whether strength decline in post-polio syndrome (PPS) results from excessive distal axonal degeneration of enlarged motor units. METHODS: We assessed changes over 10 years in isometric quadriceps strength, mean motor unit action potential (MUAP) size, root mean squared (RMS) amplitude, and level of interference (LOI) in 47 patients with PPS and 12 healthy controls, using high density surface EMG. At baseline, all patients had symptomatic quadriceps dysfunction, evidenced by transmission defects on single-fibre EMG. RESULTS: MU size and strength declined significantly by 20% and 15%, respectively in patients with PPS. Those with the largest initial MU sizes exhibited the greatest losses of mean MU size (27%) and proportional decreases in quadriceps strength (23%). Initial strength, change in LOI and change in RMS amplitude together explained 35% of the variability in strength changes in patients. MU size of controls did not change, although they lost 29% strength. CONCLUSIONS: MU size and strength declined concomitantly in a homogeneous cohort of patients with PPS and quadriceps dysfunction. SIGNIFICANCE: This long term follow-up study provides evidence that size diminution of enlarged MUs combined with a reduced number of active MUs contributes to the gradual strength decline in PPS.
Authors: Eric L Voorn; Fieke S Koopman; Merel A Brehm; Anita Beelen; Arnold de Haan; Karin H L Gerrits; Frans Nollet Journal: PLoS One Date: 2016-07-15 Impact factor: 3.240