Ectopic impulse generation in peripheral nerve hyperexcitability syndromes and amyotrophic lateral sclerosis

Publication date: Available online 10 February 2018
Source:Clinical Neurophysiology
Author(s): Yu-ichi Noto, Neil G. Simon, Alexis Selby, Nidhi Garg, Kazumoto Shibuya, Nortina Shahrizaila, William Huynh, José M. Matamala, Thanuja Dharmadasa, Susanna B. Park, Steve Vucic, Matthew C. Kiernan
ObjectiveTo elucidate differences in the distribution and firing frequency of fasciculations between peripheral nerve hyperexcitability syndromes and amyotrophic lateral sclerosis (ALS) and to explore the generator site of fasciculations.MethodsUltrasound of 14 preselected muscles was performed in patients with peripheral hyperexcitability and ALS. The distribution and firing frequency of fasciculations were calculated. Cortical excitability assessment was also done by threshold tracking transcranial magnetic stimulation.ResultsIn total, 518 muscles from 37 peripheral hyperexcitability patients and 756 muscles from 54 ALS patients were examined. Regarding the detection rate, 74% of muscles in ALS patients demonstrated fasciculations, compared with 34% of muscles in peripheral hyperexcitability patients (P <0.001). The number of unique repeating focal muscle fasciculation movements per muscle and firing frequency of individual fasciculations in ALS were both significantly higher than those in peripheral hyperexcitability (P <0.001). Furthermore, cortical silent period duration negatively correlated with the number and firing frequency of fasciculations in ALS (P <0.05). A similar relationship was not evident in peripheral hyperexcitability.ConclusionsALS patients exhibited a widespread distribution of fasciculations, whereas peripheral hyperexcitability patients had a lower limb-dominant pattern.SignificanceA significant proportion of fasciculations in ALS may be influenced by changes in central excitability.



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