Another perspective on fasciculations: when is it not caused by the classic form of amyotrophic lateral sclerosis or progressive spinal atrophy?

Abstract

Fasciculations are visible, fine and fast, sometimes vermicular contractions of fine muscle fibers that occur spontaneously and intermittently. The aim of this article is to discuss the main causes for fasciculations and their pathophysiology in different sites of the central/peripheral injury and in particular to disprove that the presence of this finding in the neurological examination is indicative of amyotrophic lateral sclerosis. Undoubtedly, most fasciculations have a distal origin in the motor nerve both in normal subjects and in patients with motor neuron disease. Most of them spread to other dendritic spines often producing an antidromic impulse in the main axon. The clinical and neurophysiological diagnosis must be thorough. It may often take long to record fasciculations with electroneuromyography. In other cases, temporal monitoring is necessary before the diagnosis. The treatment, which may be adequate in some cases, is not always necessary.

Spontaneous mechanical and electrical activities of human calf musculature at rest assessed by repetitive single‐shot diffusion‐weighted MRI and simultaneous surface electromyography

“…On the other hand, action potentials of motor neurons are known as common stimulus for the excitation of larger muscle areas (motor units, comprising hundreds of myocytes in the calf muscles). Fasciculations are visible but unintentional contractions that occur spontaneously in healthy subjects or subjects affected by movement disorders, motor neuron diseases or system diseases . These fasciculations are caused by repetitive activation by motor units leading to electric potentials in sEMG with a peak‐to‐peak amplitude up to 500 µV .…”

Increased muscle echointensity correlates with clinical disability and muscle strength in chronic inflammatory demyelinating polyneuropathy

“…The origin and significance of fasciculations in CIDP are still uncertain as they also occur in radiculopathies and entrapment neuropathies, and even occur in healthy individuals. The actual site of origin may be distal in the axon or in the denervated muscle resulting from hypersensitivity and hyperexcitability [13,14]. In healthy individuals, fasciculations probably occur with much lower frequency than that found for the CIDP patients in the present study.…”

Citalopram-induced dyskinesia of the tongue: a video presentation

“…Among clinicians there is often a large interobserver disagreement in interpreting the clinical findings. Fasciculations are described as intermittent activation of some or all of the muscle fibres innervated by one or more motor units 3. Patients with fasciculations are commonly not aware of these muscle twitches.…”