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Updated: Jun 19, 2026
In Vivo Electrophysiological Measurement of Compound Muscle Action Potential from the Forelimbs in Mouse Models of Motor Neuron Degeneration
Published on: June 15, 2018
Enhanced spinal motoneuron excitability as a marker of motor neuron dysfunction in primary lateral sclerosis
Miguel Oliveira Santos1, Mamede de Carvalho1
1Department of Neurosciences and Mental Health, ULS Santa Maria, Lisbon, Portugal; Institute of Physiology, MUHCRI and Centro de Estudos Egas Moniz, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.
Objective:
To investigate F-wave parameters as markers of spinal motoneuron excitability in patients with primary lateral sclerosis (PLS).
Methods:
We prospectively evaluated F-waves and M-waves from the abductor pollicis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) muscles. The study included three groups: 27 patients with PLS, 36 with amyotrophic lateral sclerosis with normal right-hand function (ALS-NH), and 30 healthy controls (HC). Recorded parameters included M-wave amplitude, F-wave frequency, latencies, amplitude, and the F/M-waves amplitude ratio. Upper motor neuron (UMN) clinical scores were also assessed. Statistical analysis was performed using One-way ANOVA or Kruskal-Wallis tests for group comparisons, and Spearman's rank test for correlations.
Results:
PLS had a significantly higher UMN score than ALS-NH (p < 0.001). F-wave amplitudes were significantly higher in PLS compared to both ALS-NM and HC across all muscles (APB, p = 0.01 and p = 0.03; FDI, p = 0.002 and p < 0.001; ADM, p = 0.03 and p < 0.001, respectively). F/M-waves amplitude ratio was also significantly higher in PLS vs. ALS-NH/HC (APB, p = 0.01 and p = 0.03; FDI, p < 0.001 and p < 0.001; ADM, p = 0.03 and p = 0.001, respectively). No significant differences were found between ALS-NM and HC for these parameters (p > 0.05). M-wave amplitudes and other F-wave parameters remained comparable across all groups (p > 0.05). No correlation was found between F-wave amplitude and UMN scores in PLS patients (p > 0.05).
Conclusions:
Patients with PLS exhibit significantly increased F-wave amplitudes and F/M amplitudes ratios compared to ALS-NH and HC.
Significance:
Increased F-waves size serves as a neurophysiological marker of enhanced spinal motoneuron excitability in PLS.
