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Modulation of fasciculation frequency in amyotrophic lateral sclerosis
  1. Mamede de Carvalho1,2,
  2. Antonia Turkman3,
  3. Susana Pinto1,
  4. Michael Swash1,4
  1. 1Translational Clinical Physiology Unit, Faculty of Medicine, Instituto de Medicina Molecular and Institute of Physiology, University of Lisbon, Lisbon, Portugal
  2. 2Department of Neurosciences, Hospital de Santa Maria, Lisbon, Portugal
  3. 3Faculty of Sciences, Centro de Estatística e Aplicaçōes, University of Lisbon, Lisbon, Portugal
  4. 4Departments of Neurology and Neuroscience, Royal London Hospital, Queen Mary University of London, London, UK
  1. Correspondence to: Professor Mamede de Carvalho, Department of Neurosciences, Hospital de Santa Maria, Av Professor Egas Moniz, Lisbon 1648-028, Portugal; mamedemg{at}mail.telepac.pt

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Fasciculations are a major clinical feature, present very early in the natural history of amyotrophic lateral sclerosis (ALS).1 They represent spontaneous discharges of motor units or portions of motor units, that can sometimes also be activated volitionally.2 There is no objective evidence that fasciculation potential (FP) discharges can be modulated by the patient or by the examiner. In this study we have addressed this issue in ALS, spinal muscular atrophy (SMA) and benign fasciculation syndrome (BFS).

Methods

We evaluated fasciculation firing frequency, using surface electromyographic (EMG) recordings from the first dorsal interosseous (DI) muscle in the hand at rest, and randomly after a period of maximal contraction, thus involving upper and lower motor neuron excitation, after radial sensory nerve stimulation and after supramaximal electrical stimulation of the ulnar nerve at the wrist, representing lower motor neuron excitation. We studied 75 patients with definite or probable ALS, excluding patients with polyneuropathy, diabetes or ulnar neuropathy (median age 61 years (range 27–75 years), median disease duration 12 months (range 3–24 months), 48 were men). One hand, in which first DI strength was 4 on the MRC (Medical Research Council) score 4 or 5, was studied in each patient. In each participant, FPs were recorded at rest in the first DI muscle. Six patients with SMA type 3 were studied (median age 45 years; range 28–60 years). …

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