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Single motor unit H‐reflex in motor neuron disorders
Author(s) -
Soliven Betty,
Maselli Ricardo A.
Publication year - 1992
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880150604
Subject(s) - motor unit , motor neuron , reflex , neuroscience , latency (audio) , electrophysiology , anterior horn cell , electromyography , medicine , psychology , spinal cord , amyotrophic lateral sclerosis , computer science , disease , telecommunications
The latency fluctuation of single motor unit potentials (MUP H ) in the H‐reflex is greater than the latency fluctuation of MUPs in the direct (MUP M ) and recurrent (MUP F ) responses. This has been attributed to the variability in the impulse generation at the site of nerve stimulation, and to the variation in the synaptic delay at the anterior horn cell. We studied the latency fluctuation of single motor unit H‐reflex in patients with motor neuron disorders (MND) in comparison with normal subjects. The mean jitter of the H‐reflex was 264.3 ± 17.8 μs (mean ± SEM) in 30 MUP H recorded from 10 patients with ALS, 302.7 ± 25.2 μs in 16 MUP H from 6 patients with chronic motor neuron diseases, as compared with 137.4 ± 7.3 µs in 34 MUP H recorded from 10 normal subjects. This difference, which persisted even after the correction for the latency variation of MUP M , cannot be explained on the basis of an enhanced reciprocal inhibition. Thus, the increased latency fluctuation of the single motor unit H‐reflex in patients with MND may reflect changes in the motoneuron pool excitability that may be secondary to altered intrinsic electrophysiological properties of motoneurons, or to an abnormal temporal and spatial summation of synaptic inputs on motoneurons.