Sensory modulation of fasciculation discharge frequency

Abstract

Introduction: Fasciculations are a marker for the diagnosis of amyotrophic lateral sclerosis (ALS) and reflect increased lower motor neuron (LMN) excitability. Methods: We investigated modulation of fasciculation frequency in the first dorsal interosseous (FDI) muscle of the right hand following peripheral sensory nerve electrical stimulation, and vibration over the muscle‐tendon region (50 and 100 Hz), in patients with ALS, spinal muscular atrophy, and benign fasciculation syndrome. FDI muscles of ALS patients were classified by the presence or absence of neurogenic changes on needle electromyography. Results: Both sensory nerve electrical stimulation and vibration significantly increased the frequency of fasciculations in neurogenic FDI muscles of ALS patients, but not in the remaining groups. Discussion: Our results favour increased excitability of LMNs when affected by the disease process in ALS. We found that some fasciculations originating in these neurons in ALS are susceptible to modulation by sensory input. Muscle Nerve 59:688–693, 2019

Sensory Involvement in Amyotrophic Lateral Sclerosis

“…Thus, the recognition and characterization of sensory signs and symptoms are of clear importance in the knowledge of the etiopathogenic and clinical features of ALS. There are common links between sensory afferents and the motor aspects of the disease, since fasciculations, a characteristic and main feature in ALS, can be modulated by sensory nerve stimulation [ 53 ]. This peculiarity reinforces the fact that sensory pathways play a role in the clinical manifestations of the disease, and therefore should not be considered an isolated compartment, aside from the pathophysiological mechanisms occurring in motor pathways ( Figure 1 ).…”

Characteristics of Sensory Neuron Dysfunction in Amyotrophic Lateral Sclerosis (ALS): Potential for ALS Therapy

“…Most ALS cases are sporadic ALS, and most patients with ALS show intracytoplasmic aggregation of ALS-inducing factors such as SOD1 and TAR DNA-binding protein 43 (TDP-43) in motor neurons, which is increasingly considered a feature of ALS [2,[11][12][13][14][15]. The clinical phenotype of ALS includes both upper motor neurons (UMNs) and lower motor neurons (LMNs), but non-motor areas are increasingly found to be involved, leading to non-motor symptoms that include autonomic dysregulation, cognitive impairment, sensory impairment, and frontotemporal dementia (FTD) [15][16][17][18][19][20][21][22]. Clinical and preclinical studies have reported abnormalities in sensory neurons, and further research in this regard is ongoing.…”