PAPER

Pyridostigmine in postpolio syndrome: no decline in fatigue and limited functional improvement

H L D Horemans¹, F Nollet¹, A Beelen¹, G Drost², D F Stegeman², M J Zwarts², J B J Bussmann³, M de Visser⁴ and G J Lankhorst¹

¹ Department of Rehabilitation Medicine, VU University Medical Centre, Amsterdam, Netherlands
² Department of Clinical Neurophysiology, University Medical Centre Nijmegen, Netherlands
³ Department of Rehabilitation Medicine, Erasmus MC, University Medical Centre Rotterdam, Netherlands
⁴ Department of Neurology, Academic Medical Centre, University of Amsterdam, Netherlands

Correspondence to:
Correspondence to:
Herwin Horemans
Department of Rehabilitation Medicine, VU University Medical Centre, PO Box 7057, 1007 MB Amsterdam, Netherlands; h.horemans{at}vumc.nl

Objectives: To investigate the effect of pyridostigmine on fatigue, physical performance, and muscle function in subjects with postpoliomyelitis syndrome.

Methods: 67 subjects with increased fatigue and new weakness in one quadriceps muscle showing neuromuscular transmission defects, were included in a randomised, double blind, placebo controlled trial of 60 mg pyridostigmine four times a day for 14 weeks. Primary outcome was fatigue (on the "energy" category of the Nottingham health profile). Secondary outcomes included two minute walking distance and quadriceps strength and jitter. Motor unit size of the quadriceps was studied as a potential effect modifier. The primary data analysis compared the changes from baseline in the outcomes in the last week of treatment between groups.

Results: 31 subjects treated with pyridostigmine and 31 subjects treated with placebo completed the trial. No significant effect of pyridostigmine was found on fatigue. The walking distance improved more in the pyridostigmine group than in the placebo group (by 7.2 m (6.0%); p<0.01). Subgroup analysis showed that a significant improvement in walking performance was only found in subjects with normal sized motor units. Quadriceps strength improved more in the pyridostigmine group than in the placebo group (by 6.7 Nm (7.2%); p = 0.15). No effect of pyridostigmine was found on jitter.

Conclusions: Pyridostigmine in the prescribed dose did not reduce fatigue in subjects with postpoliomyelitis syndrome. However, it may have a limited beneficial effect on physical performance, especially in subjects with neuromuscular transmission defects in normal sized motor units.

Keywords: postpoliomyelitis syndrome; randomised controlled trial; pyridostigmine; fatigue

Abbreviations: FSS, fatigue severity scale; MCD, mean consecutive latency difference; MF, median frequency; MVA, maximum voluntary activation; MVC, maximum voluntary contraction; NHP_E, "energy" category of the Nottingham health profile; S-SFEMG, single fibre electromyographic stimulation

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