This condition is characterized by stereotyped, repetitive movements involving large muscles, usually of the head and neck, which typically occur immediately prior to sleep onset and are sustained into light sleep. The most commonly recognized variant is head banging, which itself has several forms:

• the head and torso may be banged down against the pillow or mattress.
• a rocking action on the hands and knees.
• banging the front of the head into the headboard.

Less common movement forms include body rolling, leg banging, or leg rolling. Humming and chanting may accompany the movements and may be quite loud. Environmental stress and lack of environmental stimulation may be causative factors.