Fasciculations

Fasciculations - contractions of one or more motor units (an individual motor neuron and the group of muscle fibers it supplies) result in rapid, visible contractions of muscle bundles (fascicular twitches or fasciculations). Fasciculations appear on EMG as broad biphasic or multiphasic action potentials. Simultaneous or sequential contraction of multiple motor units produces a wave-like muscle contraction known as myokymia.

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Causes fascializations

1. Motor neuron diseases (ALS, progressive spinal amyotrophy, less commonly other diseases)
2. Benign fasciculations
3. Painful Muscle Fasciculation Syndrome
4. Damage or compression of a nerve root or peripheral nerve
5. Facial myokymia (multiple sclerosis, brain tumor, syringobulbia, less commonly other causes)
6. Neuromyotonia (Isaacs syndrome)
7. Facial hemispasm (some forms)
8. Postparalytic contracture of facial muscles
9. Iatrogenic fasciculations.

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Motor neuron diseases

Fasciculations are typical for motor neuron diseases (ALS, progressive spinal amyotrophies). However, the presence of fasciculations alone without signs of denervation is insufficient for the diagnosis of motor neuron disease. In amyotrophic lateral sclerosis, EMG reveals widespread dysfunction of the anterior horn cells, including in clinically intact muscles, and clinically there are also symptoms of upper motor neuron damage (pyramidal signs) and a progressive course of the disease. A characteristic picture of "asymmetric amyotrophy with hyperreflexia and a progressive course" is revealed.

Progressive spinal amyotrophies are caused by degeneration of the anterior horn cells and are manifested only by symptoms of lower motor neuron damage (neuronopathy), there are no signs of upper motor neuron damage. Amyotrophies are more symmetrical. Fasciculations are detected, but not always. The disease has a more favorable course and prognosis. EMG examination is of decisive importance in the diagnosis of motor neuron diseases.

Other motor neuron lesions (tumors of the brainstem and spinal cord, syringobulbia, OPCA, Machado-Joseph disease, late manifestations of poliomyelitis) may sometimes, among other manifestations, include fasciculations (usually more or less localized, for example, in the trapezius and sternocleidomastoid muscles, in the perioral musculature, in the muscles of the arms or legs).

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Benign fasciculations

Individual isolated fasciculations in the muscles of the lower leg or the orbicularis oculi muscle (sometimes they last for several days) are found in completely healthy people. Sometimes benign fasciculations become more generalized and can be observed for several months or even years. But reflexes do not change, there are no disturbances in sensitivity, the speed of excitation conduction along the nerve does not decrease, and there are no other abnormalities on the EMG except for fasciculations. Unlike ALS, benign fasciculations have a more constant localization, they are more rhythmic and, possibly, more frequent. Sometimes this syndrome is called "benign motor neuron disease."

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Painful Muscle Fasciculation Syndrome

Painful fasciculation syndrome is an unsettled term used to describe a rare syndrome of fasciculations, cramps, myalgias, and poor exercise tolerance due to degeneration of the distal axons of peripheral nerves (peripheral neuropathy). The term is sometimes used to refer to the previous syndrome when it is accompanied by frequent painful cramps.

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Damage or compression of a nerve root or peripheral nerve

These lesions may cause fasciculations, myokymia, or cramps in the muscles innervated by the root or nerve. These symptoms may persist after surgical treatment of compressive radiculopathy.

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Facial myokymia

Facial myokymia is a rare neurological symptom and is often the only finding in the neurological status. Facial myokymia has great diagnostic value, as it always indicates an organic lesion of the brainstem. Its onset is usually sudden, and the duration varies - from several hours (for example, in multiple sclerosis) to several months and even years. Voluntary mental activity, reflex automatisms, sleep and other exogenous and endogenous factors have little or no effect on the course of myokymia. It manifests itself as small wave-like (worm-like) contractions of muscles on one half of the face and most often develops against the background of multiple sclerosis or brainstem glioma. Less often, facial myokymia is observed in Guillain-Barré syndrome (can be bilateral), syringobulbia, facial nerve neuropathy, ALS and other diseases. EMG reveals spontaneous rhythmic activity in the form of single, double or group discharges with a relatively stable frequency.

Clinically, facial myokymia is usually easily distinguished from other facial hyperkinesis.

Differential diagnosis of facial myokymia is carried out with facial hemispasm, myorhythmia, Jacksonian epileptic seizure, benign fasciculations.

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Neuromyotonia

Neuromyotonia (Isaacs syndrome, syndrome of constant muscle fiber activity) occurs in both children and adults and is characterized by gradually increasing stiffness, muscle tension (stiffness) and small muscle contractions (myokymia and fasciculations). These symptoms begin in the distal parts of the limbs, gradually spreading proximally. They persist during sleep. Pain is rare, although discomfort in the muscles is quite typical. The hands and feet assume a position of constant flexion or extension of the fingers. The trunk also loses its natural plasticity and posture, the gait becomes tense (stiff) and constrained.

Causes: The syndrome is described as an idiopathic (autoimmune) disease (hereditary or sporadic), as well as in combination with peripheral neuropathy. In particular, Isaacs syndrome is sometimes observed in hereditary motor and sensory neuropathies, in CIDP, toxic neuropathies and neuropathies of unknown origin, in combination with malignant neoplasm without neuropathy, in combination with myasthenia.

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Facial hemispasm

Fasciculations and myokymia, along with myoclonus, constitute the main clinical core of facial hemispasm manifestations. Clinically, fasciculations are not always easily noticeable here, as they are covered by more massive muscle contractions.

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Postparalytic contracture of facial muscles

The same can be said about post-paralytic contracture of the facial muscles (“facial hemispasm syndrome after neuropathy of the VII nerve”), which can manifest itself not only as persistent contracture of the muscles of varying degrees of severity, but also as myoclonic local hyperkinesis, as well as fasciculations in the area of the affected branches of the facial nerve.

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Iatrogenic fasciculations

Iatrogenic fasciculations have been described with the use of penicillin and overdose of anticholinergics.

Fasciculations may occasionally appear in hyperthyroidism, which, in combination with muscle atrophy and weakness, may mimic amyotrophic lateral sclerosis.

Rattlesnake, scorpion, black widow spider and some stinging insect bites can cause cramps, myalgias and fasciculations.

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Symptoms fascializations

Normally, a relaxed muscle is not accompanied by bioelectrical activity. If fasciculations are the only symptom, i.e. are not accompanied by muscle atrophy and reflex changes, their clinical significance is small. In case of more severe motor neuron dysfunction, all muscle fibers that receive innervation from it suffer, which leads to muscle atrophy (denervation atrophy), decreased reflexes and is accompanied by fibrillation potentials, positive waves, fasciculations and changes in motor unit potentials.

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Treatment fascializations

Treatment involves dietary changes that involve increasing magnesium intake from foods such as nuts (especially almonds), bananas, and spinach. Medications containing magnesium may be recommended.

Prevention

Fasciculations can be a consequence of long-term stress, so preventing the occurrence of stressful situations is one of the main methods of prevention.

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