Dr. Friedman, Chief, Division of Movement Disorders, Department of Neurology, at the Warren Alpert Medical School of Brown University and Stanley Aronson Chair in Neurodegenerative Disorders at Butler Hospital received fees from Acorda Pharmaceuticals and Concert Pharmaceuticals for consulting work.)
Dr. Fekete of New York Medical College received consultation fees from Acadia, Acorda, Adamas, Amneal/Impax, Kyowa Kirin, Lundbeck, Neurocrine, and Teva.)
Stereotypic behaviors are seen in a number of neurologic and psychiatric conditions, as well as in normal people. They are common in autism; Tourette syndrome; retardation; psychotic disorders, including N-methyl-d-aspartate receptor antibody (NMDAR) encephalitis; and neuroleptic-induced tardive syndromes and may be present in some degenerative 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 authors review these behaviors and put 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 and 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.
• Stereotypies may occur in neurdegenerative dementing illnesses.
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), and may occur in catatonia as well (Serra-Mestres et al 2020).
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 primates 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). However, laboratory scientists have pointed out that pacing behavior may be pathologic in some species but not others (Poirier and Bateson 2017). 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 manifests as restless movements in the legs, described as “leg stereotypy disorder” (Jankovic 2016) or leg stereotypy syndrome (Lotia et al 2018), 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. In 92 subjects consisting of patients with restless legs syndrome, Parkinson disease, Tourette syndrome, and tardive dyskinesia and their companions of similar age, Lotia and colleagues reported leg stereotypy syndrome in 7% of individuals in the general population group and 17% in the movement disorder group (Lotia et al 2018). The movements involved predominantly one leg, and all had a family history of a similar disorder.
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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