Comparison of multiple point stimulation and incremental stimulation motor unit number estimation in follow-up study of patients with amyotrophic lateral sclerosis / 中华神经科杂志

ABSTRACT

Objective To compare two common techniques for motor unit number estimation (MUNE), multiple point stimulation(MPS) and incremental stimulation, and determine which is preferable in the follow-up study of patients with amyotrophic lateral sclerosis (ALS).Methods MPS or incremental stimulation MUNE was recorded respectively in 120 ALS patients at baseline and month 3, 6, 9 ,and 12 after study entry.The maximal baseline to negative peak compound muscle action potential (CMAP) amplitude was recorded.For multiple point stimulation, the stimuli sites included the skin of the wrist, 6 cm above the wrist, elbow and 6 cm above the elbow.Individual motor unit responses were obtained by moving thestimulating electrode and isolating threshold responses.Then, with finely graded stimulus intensity at one point, 3 steps in a CMAP were investigated.For incremental stimulation, stimulus intensity was slowlyincreased from subthreshold levels until a small, all-or-none response was evoked.The intensity was slowly increased until the response increased in a quantal fashion.This process was repeated for a total of 10 increments.Single motor unit potential were obtained by subtracting amplitudes of each response from that of the prior response.The values obtained from two methods were compared.Results The value of MUNE declined in the follow-up period.MUNE obtained from MPS was the same as that gained from incremental stimulation at the baseline and the 3rd, 9th, 12th month after study entry, while MUNE obtained in MPS was more than that obtained from incremental stimulation at the 6th month after study entry ( 88 ± 6 and 47 ± 5;t = 1.72, P = 0.04).Conclusions Both MPS and incremental stimulation are certain in the follow-up study of patients with amyotrophic lateral sclerosis.The value of MUNE obtained from two methods might be different in some period.