This article includes discussion of stereotypies, complex repetitive movements, autism, psychosis, intellectual disability, normal development, tics, Rett syndrome, fronto-temporal dementias, and tardive dyskinesia. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Stereotypic behaviors are seen in a number of neurologic and psychiatric conditions, as well as in normal people. They are common in autism, retardation, and psychoses and are present in some dementing disorders. Some are medication induced. Head-banging and rocking behaviors are seen in normal children who outgrow them. They are on a continuum with obsessive compulsive spectrum disorders, the umbrella term now used for tics, hair pulling, and a variety of other repetitive, purposeless behaviors. In this article, the author reviews these behaviors and puts them into the context of the various disorders in which they occur. Stereotypies help define some of the autistic disorders. Treatment is discussed only briefly because evidence to support any interventions is scant.
• Stereotypies are common behaviors present in humans as well as animals, which may or may not reflect pathology.
• Stereotypies may represent a transient phenomenon in children, but may be associated with a variety of severe neurologic disorders, including specific biochemical disorders such as Rett syndrome and Lesch Nyhan disease, but also in the whole spectrum of autistic disorders and pervasive developmental disorders.
• Stereotypic disorders may require intervention, especially when harmful, but often do not. Treatment is highly individualized, involving medications or behavioral interventions and often unsuccessful.
Historical note and terminology
There have been numerous definitions given for the term “stereotypy.” Generally, it has been considered to mean a purposeless, fixed form of expression or response that may interfere with normal behavior. Stereotypies have long been recognized as a possible sign of behavioral pathology. Its occurrence in intellectual disability, autism, and schizophrenia has been well established. Perhaps less well known is its occurrence in normal children in the form of head banging, head rolling, and body rocking (Sallustro and Atwell 1978; Muthugovindan and Singer 2009).
Authors writing at the turn of the century described stereotypy as a central problem in schizophrenia. "The tendency to stereotype produces the inclination to cling to one idea to which the patient then returns again and again," stated Bleuler about schizophrenia (Bleuler 1950). This tendency causes, "derailment of . . . associational activity" leading to fixed answers to various questions as well as fixed patterns of motor activities (Bleuler 1950). Motor stereotypy is still encountered in schizophrenia, more obviously late in the course (Morrens et al 2006), but early as well (Compton et al 2015).
Art depicting the insane and depraved with bizarre facial expressions, abnormal postures, and peculiar gestures consistent with stereotypy predate modern medicine (Lees 1988).
Caged animals that develop stereotyped pacing have undoubtedly been observed since time immemorial. Pacing occurs in imprisoned humans as well. Experiments on monkeys in the 1950s revealed that certain stereotyped behaviors, due to social and sensory deprivation in particular, led to permanent stereotypies that could not be altered if the deficit occurred during critical periods in brain development (Ridley and Baker 1982). Stereotypies in commercially raised animals have raised concerns about the increasingly efficient but less humane conditions of modern animal husbandry (Dantzer 1986). Human studies in autistic children reported that stereotypy interfered with learning (Koegel and Covert 1972) and implied that controlling stereotypic behavior was a necessary precondition for learning. Thus, understanding stereotypy became more important for developing rational therapies.
It must be noted that stereotypies may also occur during development of congenitally blind (Troster et al 1991) or deaf children (Bachara and Phelan 1980; Singer 2009; Bonnet et al 2010; Sanger et al 2010) who are otherwise normal. Certain movements that give an appearance of restlessness may be part of an individual's repertoire of movements, also referred to as mannerisms or habits, and are seen in otherwise normal individuals. One of the more common stereotypies is manifested as restless movements in the legs, described as “leg stereotypy disorder” (Jankovic 2016), which is defined as a repetitive, continuous movement present almost exclusively in the legs while the patient is seated. In contrast to restless legs syndrome, which usually occurs at night, there is no diurnal variation in leg stereotypy disorder, and many individuals affected by this condition may not be aware that they have the repetitive movement until it is pointed out to them. Frequently familial, the epidemiology, pathophysiology, or treatment of leg stereotypy disorder have not been studied.
A large body of work has been performed on experimental animals to understand the brain physiology of stereotypies. A variety of methods have evolved to induce and then treat stereotyped behavior in experimental animals in order to understand both the normal and abnormal brain (Fontenot et al 2009). Unfortunately, animal behavior can be interpreted in so many different ways that interpretation of a movement is often impossible. Is a movement a stereotyped motor response, a tic, a dyskinesia, akathisia, or a result of a psychic disorder? One interesting question addressed in a rodent study asked whether exercise alone, on a rotating wheel, would prevent the appearance of stereotypies in deer mice. It did not, indicating that this simple exercise, in isolation, did not overcome the effects of behavioral deprivation (Pawlowicz et al 2010).
The concept of a "tardive stereotypy" (Stacy et al 1993; Jankovic 1995; Mejia and Jankovic 2010; Pena et al 2011) was introduced to describe a neuroleptic drug-induced condition that had previously been classified as a complex set of superimposed tardive movement disorders centering about dystonia but also including dyskinesias (choreoathetosis) and pseudoakathisia.
Until the 1990s, the concept of stereotypic behaviors, both as a part of a pathologic mental syndrome and as a movement disorder, fell outside the usual purview of neurology and within the disciplines of psychiatry, developmental medicine, and psychology. As the border between neurology and psychiatry continues to blur, stereotypy has become a subject of concern for neurologists, psychiatrists, and pediatricians (Lohr and Wisniewski 1987; Jankovic 1994; Baizabal-Carvallo and Jankovic 2016). With the recognition of dopamine agonist-induced compulsive behaviors in Parkinson disease, such as gambling, hypersexuality, “punding,” and, to a lesser extent, in restless legs syndrome, the underlying mechanisms of “forced” behaviors have attracted increasing scientific attention.
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