Table 1.

Involuntary muscle contractions considered to be myoclonic in nature

Tic	Repeated, individually recognizable, intermittent movements or movement fragments that are almost often suppressible and are usually associated with awareness of an urge to perform the movement (as such they are difficult to diagnose in the veterinary patient)
Startle	An unconscious defensive response to a sudden or threatening stimulus (eg, a noxious or auditory stimulus)
Hemifacial Spasm	Spontaneous, unilateral, irregular twitching of the muscles on one side of the face in the absence of facial nerve deficits