Key result
Sprouting motor units in motor neurone disease exhibit high EMG amplitudes but normal twitch tensions.
Observational (n=26)
Motor units enlarged by sprouting in motor neurone disease are less efficient contractile units than those of normal physiological size.
The contractile and electrical properties of motor units in the first dorsal interosseous muscle of the hand have been studied in 26 patients with ulnar neuropathies and motor neurone disease (amyotrophic lateral sclerosis). Among patients with unilateral pressure or entrapment ulnar neuropathies, there was a tendency for the twitch tensions for single motor units to be smaller, while the surface EMG amplitudes were generally larger in the affected hands. Very large EMG amplitudes but normal size twitch tensions were observed among the motor neurone disease patients, indicating that, in general, motor units enlarged by sprouting are less efficient contractile units than units of normal physiological size.
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Milner‐Brown et al. (1974) conducted an observational in Ulnar neuropathies and motor neurone disease (amyotrophic lateral sclerosis) (n=26). Ulnar neuropathies and motor neurone disease vs. Unaffected hands or normal physiological size units was evaluated on Contractile and electrical properties of motor units (twitch tensions and surface EMG amplitudes). Motor units enlarged by sprouting in motor neurone disease exhibited very large EMG amplitudes but normal size twitch tensions, indicating they are less efficient contractile units.
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