A sense of paralysis that occurs between wakefulness and sleep, usually upon waking or sometimes at the onset of sleep. The person is conscious but cannot speak, move (cannot even open the eyes), and cannot breathe deeply. Atonia rarely lasts beyond 20 minutes, but when it first occurs, this experience can be terrifying, particularly if the patient also develops hallucinations.

lack of normal muscular tension or tonus

A condition evidenced by lack of muscle tone.