Fasciculations
Fasciculations are spontaneous, involuntary contractions of individual motor units that produce visible, brief muscle twitches beneath the skin or mucosal surface. They may occur in healthy individuals, particularly after exercise, caffeine use, fatigue, or stress, but can also be associated with disorders affecting the lower motor neurons, peripheral nerves, or muscles.
Fasciculations are most commonly observed in the limbs, eyelids, and tongue. When numerous fasciculations occur within the tongue, they may create a rippling appearance often described as a “bag of worms.” Although fasciculations can be a sign of neurologic disease, their presence alone does not establish a diagnosis and must be interpreted in the context of the patient’s symptoms, examination findings, and other diagnostic studies.
The distinction between benign fasciculations and those associated with neurologic disease often depends on accompanying findings such as muscle weakness, atrophy, changes in reflexes, or abnormalities on electromyography (EMG).
Tongue Fasciculations
This individual was treated decades ago in another country with radiation therapy for nasopharyngeal cancer. Radiation techniques, dose planning, and targeting accuracy may have been different from current standards, although the specifics of his treatment are unknown.
The tongue fasciculations demonstrated here are not the result of a degenerative motor neuron disease such as amyotrophic lateral sclerosis (ALS). Instead, they are believed to represent delayed radiation-induced injury to the hypoglossal nerve (cranial nerve XII), which supplies motor function to the tongue.
Potential mechanisms of injury include direct radiation damage to the nerve, radiation-induced fibrosis causing compression or tethering of the nerve, and damage to the small blood vessels that supply the nerve. Such radiation-related cranial neuropathies may emerge many years after treatment and can produce weakness, atrophy, and fasciculations of the tongue, such as are seen in this video.
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