The Journal of Physiological Sciences

, Volume 67, Issue 5, pp 569–576 | Cite as

Physiology of the fasciculation potentials in amyotrophic lateral sclerosis: which motor units fasciculate?

  • Mamede de CarvalhoEmail author
  • Michael Swash
Original Paper


We set out to study whether in amyotrophic lateral sclerosis (ALS) fasciculation potentials (FPs) arise from the most excitable motor units (MUs). We studied 70 patients with ALS and 18 subjects with benign fasciculation syndrome (BFS). Of the 56 eligible ALS patients, 31 had signs of reinnervation in the right first dorsal interosseous muscle selected for study, and 25 did not. Two needle electrodes were placed in different MUs in each studied muscle. We defined the most excitable MU as that first activated by minimal voluntary contraction. In muscles without reinnervation, the recording site with most frequent FPs had a higher probability of showing the first recruited MU (p < 0.001). No significant difference was found in other patients or in BFS subjects. In very early affected muscles, fasciculating MUs are the most likely to be recruited volitionally. This probably represents hyperexcitability at lower motor neuronal level.


Amyotrophic lateral sclerosis Benign fasciculations Fasciculation potentials Hyperexcitability Motor units Origin of fasciculation potentials 


1st DI

First dorsal interosseous


Amyotrophic lateral sclerosis


Benign fasciculation syndrome




Fasciculation potential


Interquartile range


Motor unit


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


This work was partially supported by OneWebDuals project (JPND-PS/0001/2013), an EU Joint Programme—Neurodegenerative Disease Research (JPND) project.

Ethical statement

All procedures performed were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© The Physiological Society of Japan and Springer Japan 2016

Authors and Affiliations

  1. 1.Instituto de Medicina Molecular and Institute of Physiology, Faculty of MedicineUniversity of LisbonLisbonPortugal
  2. 2.Department of NeurosciencesHospital de Santa Maria-CHLNLisbonPortugal
  3. 3.Departments of Neurology and Neuroscience, Barts and the London School of MedicineQueen Mary University of LondonLondonUK

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