Fasciculation

Spontaneous, irregular, and usually continual contractions of a muscle that is apparently at rest. Unlike the contractions of fibrillation, fasciculation is visible through the skin. Minor fasciculation, such as that which occurs in the eyelids, is common and is no cause for concern. However, persistent fasciculation with weakness in the affected muscle indicates damage to nerve cells in the spine that control the muscle or nerve fibres that connect the spinal nerves to the muscle; motor neuron disease is one such disorder.