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Lookup NU author(s): Dr Stuart MaitlandORCiD, Matt Birkbeck, Dr Ian Schofield, Dr LAWRENCE BEST, Dr James Scott, Professor Andrew BlamireORCiD, Professor Roger Whittaker
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025 The Author(s). Muscle & Nerve published by Wiley Periodicals LLC.Introduction/Aims: Surviving motor units in neurogenic diseases demonstrate collateral reinnervation. Scanning electromyography (EMG) reveals normal motor unit corridor length, but with “silent regions,” suggesting that reinnervation does not result in increased motor unit size but may increase motor unit complexity. Motor unit magnetic resonance imaging (MUMRI) pairs MR imaging with electrical nerve stimulation to visualize individual motor units. This study aimed to assess the motor unit dimensions and complexity in patients with previous poliomyelitis compared to healthy controls. Methods: Patients with a history of polio were recruited from the British Polio Fellowship, compared to a retrospective cohort of healthy controls. They underwent medical history and examination of lower limb power, fatigue assessment (fatigue severity score, FSS), and a 3 T MUMRI scan of the less-affected lower limb. The cross-sectional area, maximum, and minimum Feret diameter of the motor unit territories in tibialis anterior were calculated. Motor unit complexity was computed using the Hausdorff box-counting method. Results: Of 12 polio survivors, n = 8 (6 female) were suitable for analysis and were compared to 19 controls. The mean motor unit maximum Feret diameter was 10.3 ± 3.1 mm compared to 8.4 ± 5.2 mm in controls (p = 0.34). The mean shape complexity was 0.59 ± 0.12 compared to 0.45 ± 0.2 in controls (p = 0.03). Discussion: Polio survivors demonstrate motor units with normal dimensions but increased shape complexity, indicating nonuniform collateral reinnervation largely limited to existing territories. The size and shape of motor units could help in understanding the physiological processes behind reinnervation, both in polio and other neurogenic diseases such as amyotrophic lateral sclerosis.
Author(s): Maitland S, Birkbeck M, Schofield I, Best L, Scott J, Blamire A, Whittaker RG
Publication type: Article
Publication status: Published
Journal: Muscle and Nerve
Year: 2025
Pages: epub ahead of print
Online publication date: 14/12/2025
Acceptance date: 04/12/2025
Date deposited: 05/01/2026
ISSN (print): 0148-639X
ISSN (electronic): 1097-4598
Publisher: John Wiley and Sons Inc
URL: https://doi.org/10.1002/mus.70107
DOI: 10.1002/mus.70107
Data Access Statement: The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions
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