Decremental responses in patients with motor neuron disease.
Objective
Involvement of the neuromuscular junction (NMJ) in amyotrophic lateral sclerosis (ALS) has been reported and is increasingly recognized as an important pathophysiological aspect. The relationship between decrement and clinical measures for possible application as a biomarker has not been comprehensively explored.


Methods
We performed routine repetitive nerve stimulation (RNS) of three nerves on patients with ALS. We captured measures of muscle strength, grip strength, fatigability, and calculated slow vital capacity (SVC) rates of change assessing for associations.


Results
In 42 subjects, 210 muscles were studied. Negative correlation was found between the percentage of decrement and compound muscle action potential (CMAP) amplitude. Approximately half of the patients with hand weakness did not have decrement. There was no significant correlation between decrement and handgrip fatigue, SVC < 80% predicted, or more rapid worsening of SVC over time.


Conclusions
Abnormal decremental responses are well described in ALS. We report that the degree of decremental response does not correlate with the degree of weakness. Abnormal decrement is only rarely present in nerve-muscle pairs with normal motor power. Our findings did not support a correlation between abnormal decrement and clinical measures suggesting that RNS may not be useful as a biomarker to monitor ALS progression.
['Alanazy|Mohammed H|MH|0000-0001-5177-8283', 'Hegedus|Janka|J|', 'White|Chris|C|', 'Korngut|Lawrence|L|']
D000200:Action Potentials D000368:Aged D000690:Amyotrophic Lateral Sclerosis D018450:Disease Progression D004558:Electric Stimulation D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D053580:Muscle Strength D018908:Muscle Weakness D009133:Muscular Atrophy D009469:Neuromuscular Junction D015203:Reproducibility of Results
motor neuron disease neuromuscular junction amyotrophic lateral sclerosis repetitive nerve stimulation progressive muscular atrophy