Repetitive Nerve Stimulation in Amyotrophic Lateral Sclerosis.
Background
Nowadays, it is widely known that decremental responses in low-frequency repetitive nerve stimulation (LF-RNS) are frequently observed in patients with amyotrophic lateral sclerosis (ALS). The pathological mechanism of this phenomenon remains unknown. This study aimed to illuminate the features of RNS in Chinese patients with ALS.


Methods
Clinical and electrophysiological data of 146 probable and definite ALS patients who underwent RNS were retrospectively enrolled and analyzed. LF-RNS (3 Hz) was performed in trapezius, deltoid, abductor digiti minimi (ADM), quadriceps femoris, and tibialis anterior. High-frequency RNS (HF-RNS, 10 Hz) was performed only in ADM. The two-sample t-test and Chi-squared test were used for statistical analysis.


Results
Decremental responses to LF-RNS (≥10%) in at least one muscle were detected in 83 (56.8%) of the cases and were most commonly seen in trapezius and deltoid. The incidence of decremental response was higher in patients with upper limb onset. Incremental responses to HF-RNS (≥60%) in ADM were observed in 6 (5.6%) of the cases. In 106 muscles with decremental response, 62 (57.4%) muscles had a continuous decremental pattern, more than a U-shape pattern (37 cases, 34.3%). Nineteen cases showed definite decrements in LF-RNS tests in trapezius, while no abnormalities were found in the electromyography and neurological examination of the sternocleidomastoid muscle, supplied by the accessory nerve as well.


Conclusions
Decremental responses in the RNS are commonly observed in ALS patients. The findings regarding the trapezius indicated that some ALS onsets could be initiated by a "dying back" process, with destruction of neuromuscular junctions (NMJs) before motor neurons. Incremental responses in the ADM implied damage of the NMJs involved both the post and presynaptic membranes.
['Sun|Xiao-Sun|XS|', 'Liu|Wen-Xiu|WX|', 'Chen|Zhao-Hui|ZH|', 'Ling|Li|L|', 'Yang|Fei|F|', 'Wang|Hong-Fen|HF|', 'Cui|Fang|F|', 'Huang|Xu-Sheng|XS|']
D000368:Aged D000690:Amyotrophic Lateral Sclerosis D004558:Electric Stimulation D004576:Electromyography D006801:Humans D008297:Male D008875:Middle Aged D009046:Motor Neurons D018482:Muscle, Skeletal D012189:Retrospective Studies D055815:Young Adult
Repetitive Nerve Stimulation Amyotrophic Lateral Sclerosis Decremental Response Dying Back