Stereotypies can be classified in a number of ways.
Etiology:
(1) secondary
(2) primary (absence of a secondary cause)
Expression:
(1) motor
(1a) common (head banging, rocking, finger drumming, etc)
(1b) complex arm and hand
(1c) head nodding
(2) vocalizations or phonic
(3) visual (atypical gazing at fingers or objects)
