Abstract

BackgroundIn amyotrophic lateral sclerosis (ALS), the involvement of lower motor neuron is well defined by electromyography, whereas a reliable marker of upper motor neuron (UMN) damage still lacks. Aim of the study was to estimate the role of transcranial magnetic stimulation (TMS)-induced motor-evoked potentials (MEPs) as marker of subclinical UMN involvement.MethodsClinical evidence of UMN damage was prospectively compared to MEPs in 176 ALS patients diagnosed between 2011 and 2014, and classified according to existing diagnostic criteria. Finally, we evaluated the appearance of clinical UMN signs and the level of diagnostic certainty in ALS after 1 year of follow-up.ResultsAt presentation, abnormal MEPs were found in 80% of patients with clinical evidence of UMN damage and in 72% of patients without clinical involvement of UMN. Among these latter, 61% showed appearance of UMN clinical signs after 1 year. Approximately 70% of patients with clinical lower motor neuron (LMN) phenotype showed MEP abnormalities, while they were considered not classifiable ALS according to Airlie house or Awaji criteria. Furthermore, abnormal MEPs in absence of clinical UMN signs at baseline were found in 80% of spinal ALS that after 1-year developed UMN signs at limbs, compared to 50% of bulbar ALS.ConclusionsTMS is a reliable marker of subclinical UMN damage particularly among LMN phenotype and ensure an early ALS diagnosis in ~ 70% of such cases.

Highlights

  • Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by upper (UMN) and lower motor neurons (LMN) damage

  • We evaluated transcranial magnetic stimulation (TMS) findings among 40 cases clinically classified at baseline as suspected amyotrophic lateral sclerosis (ALS) according to El Escorial criteria (EEC), LMN phenotype

  • We evaluated the occurrence of motor-evoked potentials (MEPs) abnormalities stratifying patients according to the site of symptoms onset; we found that the proportion of patients presenting TMS abnormalities in at least one region in the absence of clinical upper motor neuron (UMN) signs at limbs was similar between spinal [72% (n = 28/39)] and bulbar-onset ALS [71% (n = 8/11)]

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Summary

Introduction

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by upper (UMN) and lower motor neurons (LMN) damage. In amyotrophic lateral sclerosis (ALS), the involvement of lower motor neuron is well defined by electromyography, whereas a reliable marker of upper motor neuron (UMN) damage still lacks. Aim of the study was to estimate the role of transcranial magnetic stimulation (TMS)-induced motor-evoked potentials (MEPs) as marker of subclinical UMN involvement. Results At presentation, abnormal MEPs were found in 80% of patients with clinical evidence of UMN damage and in 72% of patients without clinical involvement of UMN Among these latter, 61% showed appearance of UMN clinical signs after 1 year. 70% of patients with clinical lower motor neuron (LMN) phenotype showed MEP abnormalities, while they were considered not classifiable ALS according to Airlie house or Awaji criteria. Conclusions TMS is a reliable marker of subclinical UMN damage among LMN phenotype and ensure an early ALS diagnosis in ~ 70% of such cases

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