Furthermore, the mean F-wave amplitude (<i>r</i> = 0.454, <i>P</i> = 0.002) of the FDI was significantly correlated with the FDI/ADM CMAP amplitude ratio in ALS patients with affected hands but not of the ADM. Our findings suggested that the dysfunction of spinal motoneurons between the FDI and ADM was different in ALS, and spinal motoneuron dysfunction was associated with development of the split-hand phenomenon.
In older subjects, the CMAP amplitude decreased with age, but the decrement was increased only in ADM. At the baseline study the CMAP amplitude was similar in all three muscles in control and ALS patients.