This review of stereotypy is devoted to movements alone and not to stereotypic verbal responses to stimuli. The exact definition of stereotypy varies with different authors. Lohr and Wisniewski have described stereotypies as appearing to be "fragments of a normal action that are continually repeated without purposes . . . Some may simply be reiterated bizarre purposeless acts . . . " without conscious control, although consciousness is intact. "The movements are usually uniform, but at times incomplete forms of a given stereotypy may be observed" (Lohr and Wisniewski 1987). Jankovic defines stereotypy as an "involuntary or unvoluntary [unvoluntary defined as a physical response to an inner driving force such as restlessness or psychic pain] . . . coordinated, patterned, repetitive, rhythmic, purposeless but seemingly purposeful or ritualistic, movement, posture or utterance" (Jankovic 1994). Tan and colleagues, however, believe that stereotypies "can be suppressed voluntarily without a buildup of inner tension," thus distinguishing them from tics (Tan et al 1997). Another definition defines motor stereotypies as “involuntary, patterned, coordinated, repetitive, rhythmic, and nonreflexive features, (which) typically last for seconds to minutes, tend to occur in clusters, appear many times per day, and are associated with periods of stress, excitement, fatigue, or boredom” and are readily suppressible (Mahone et al 2004). Another definition was offered in 2012 in an attempt to distinguish stereotypies from tics and other repeated movement disorders (Edwards et al 2012): “a non–goal-directed movement pattern that is repeated continuously for a period of time in the same form and on multiple occasions, and which is typically distractible.” In farm animals, a consensus definition of stereotypy is a repetitive action, fixed in form and orientation, that serves no obvious function (Commission of the European Communities 1983).
Stereotypies can be classified into simple movements (such as rocking, tapping, hugging, and lip biting) and complex movements (which include ritualistic behaviors such as spitting into a hand and smearing it in a particular fashion, or running forward a set number of paces then running backwards, repeated raising and lowering of the arms, waving and flapping of the arms and hands, and finger wiggling) (Jankovic 1994; Mahone et al 2004). The most typical stereotypies include rocking, hugging, self-touching, patting, grunting, foot tapping, leg swinging, and hair pulling.
In normal development, children may rock back and forth, roll (or even bang) their heads. These behaviors have been reported to occur in approximately 20% of normal children (Kravitz and Boehm 1971; Sallustro and Atwell 1978) in isolation and, therefore, not evidence of pathology. They are generally part of sleep behavior, seen in sleep transitions and are considered “soothing” behaviors. They become less common with age. Certain patterned motor behaviors are considered normal in adults and include foot tapping, crossing and uncrossing the legs, and tapping fingers on a chair arm. Some stereotypic behaviors may be associated with obsessive compulsive symptoms; it may not be clear where normal ends and pathology begins (Niehaus et al 2000).
Stereotypies must be distinguished from mannerisms, tics, and other complex repetitive acts. A mannerism is an odd, idiosyncratic method of performing a task that is unique to an individual and serves no apparent function (ie, a person who cocks an arm in a peculiar way in order to drink from a cup; a ballplayer who performs ritualistic acts "for luck."). However, this use of the term "mannerism" is not universally agreed on, and Lohr and Wisniewski assert that inherent in a manneristic behavior is an obvious "unusual or grotesque" component that would signal to anyone in any culture the obvious abnormality of the behavior (Lohr and Wisniewski 1987).
Compulsions such as repetitive hand washing, touching, checking, hair pulling, spitting, as well as the more complex ritualistic behavior that also occurs in obsessive compulsive disorder form another category of stereotypic behavior. In these cases, the activity serves an inner psychic need that may be overwhelming. In Lesch-Nyhan syndrome, for example, children will ask to be restrained to keep themselves from painful self-mutilation. When these movements occur in response to a cognitive rather than a sensory intrusion, the movement is considered to be a manifestation of obsessive compulsive disorder (Vuong 2004).
The term “obsessive compulsive spectrum disorder” is now used to describe obsessive behaviors that result from sensory rather than cognitive intrusions (Vuong 2004). Nail biting, hair pulling, and tics are classified as obsessive compulsive spectrum disorder.
Simple tics are abrupt in onset, brief, simple movements. Complex tics such as repetitive head shaking, stooping, throwing oneself on the ground, and gesturing may be difficult to distinguish from the movements associated with obsessive compulsive disorder that so frequently accompanies Tourette syndrome. Occasionally, children with Tourette syndrome are misdiagnosed as suffering from autism as a result of these stereotypies (Jankovic 1994).
Akathisia is defined by the inability to keep still due to an inner need to move. Patients with akathisia tend to stand after being seated for more than a few seconds, march in place when standing, shift weight from 1 foot to the other, and sometimes rub their hands over their arms. Akathisia comes in an acute form induced by dopamine-blocking drugs, a tardive form, also induced by neuroleptics, and occurs in association with idiopathic Parkinson disease.
A perseveration is a repeated movement. It generally occurs immediately following a normal goal directed action, but may break down into a fragment of the original movement. The perseverated movement will stop, but will be replaced by an entirely new behavior, unrelated to the previous one and will not recur spontaneously, unlike a stereotypy, which recurs endlessly.
Although stereotypies vary from syndrome to syndrome, there is a great deal of overlap. They are common in the autistic, the mentally retarded, the severely psychotic, and the congenitally blind, but not in other populations. Although it is common to find stereotypy in all of these syndromes, it is much more likely to be associated with autism (Mandelbaum et al 2006). Autism is a specific behavioral syndrome, resulting from abnormal brain development. It is distinct from the more general term mental retardation, although most autistic children have IQ scores below 70 (Fenichel 1993). Stereotypy is a prominent feature of this syndrome. The most common stereotypies are facial grimacing, staring at flickering lights, waving objects in front of the eyes, producing repetitive sounds, arm flapping, rhythmic body rocking, repetitive touching, feeling and smelling objects, jumping, walking on toes, and unusual hand and body gesturing (Jankovic 1994). It has even been proposed that stereotypies are relatively specific indicators of autism in children with communication problems (Brasic 1999; Mandelbaum et al 2006). Stereotypic behaviors are associated with more bizarre and less integrated behavior in Down syndrome (Carter el al 2007).
Congenitally blind children display similar stereotypies to the mentally retarded and autistic, but with less self-injurious behavior. Eye poking is the most common movement, but body rocking, repetitive manipulation, finger sucking, head rocking, and other movements occur as well (Troster et al 1991).
"Punding," a peculiar stereotypy induced by amphetamine and cocaine use in adults, is a repetitive handling and intense fascination in handling common objects, such as moving a ball in one's hand, or repeated aimless self-injurious picking (Ellinwood et al 1973; Brust 1993). It may involve repetitive dismantling and rebuilding of an object. In children, amphetamine poisoning may induce head banging, finger biting, and violent purposeless movements (Espilin and Done 1968). This has been described as an uncommon but not rare problem in Parkinson disease patients treated with dopamine agonists (Miyasaki et al 2007). Two published cases have been ascribed to strokes: one in the putamen and the other in the brainstem (Maraganore et al 1991; Nguyen et al 2007).
Tardive stereotypies, those induced by chronic (greater than 3-month) exposure to neuroleptic drugs, occur in a high percentage of patients with tardive dyskinesia (Stacy et al 1993; Jankovic 1995; Mejia and Jankovic 2010). These stereotypies are most common in the orolingual-facial region, followed by the lower limbs, upper limbs, trunk, and pelvis. The orolingual-facial movements involve lip puckering as well as tongue writhing and protrusion. Vocalizations are humming and belching. Leg movements are tapping, crossing and swinging legs, and kicking. Arm movements are rubbing, picking, and thumb twiddling. These movements can be difficult to distinguish from the stereotypies in neuroleptic-exposed children with autism (Meiselas et al 1989).
The stereotypies in psychotic patients are not significantly different from those in other disorders; however, stereotypies tend to develop in the later stages of the disease (Morrens et al 2006). Distinguishing a psychosis-driven behavior (ie, pacing, rocking, or jumping) from akathisia can be impossible when the patient is uncommunicative. Stereotypies are an important component of catatonia, a syndrome most commonly seen in psychotic affective disorders and schizophrenia.
In the syndromes of autism and mental retardation, stereotypies are often associated with self-injurious behavior (Robertson 1992). Body rocking in particular has been associated with self-hitting (Rojahn 1986). Typical clinical syndromes include nail biting, finger biting, punching objects, hitting oneself, and head banging. However, self-injury may also be seen in Tourette syndrome, Lesch-Nyhan syndrome, neuroacanthocytosis, tuberous sclerosis, and in psychiatric patients. Some patients require special apparatuses or environments to reduce the injuries. Self-injuries due to psychosis tend to be the result of a few major traumas (ie, the result of an angry outburst, a suicide attempt, or deliberate self-mutilation). For example, a schizophrenic enucleated 1 eye after killing her baby because of command hallucinations. Persistent head banging, eye poking, hitting, and self-chewing at a low level that results in injury is uncommon even among severely psychotic patients.
Automatisms due to complex partial seizures should be easy to distinguish from stereotypies. Automatisms are sudden in onset, occur in a clouded sensorium, are time limited, do not reliably occur following periods of stress, may occur during sleep, may be followed by a postictal behavioral change, and occur randomly.
In a likely stretch of the term, one author posited that yawning was a form of genetically stereotyped behavior induced by certain emotional stimuli (Walusinsk 2010).