Stereotypic movements are common in children with neurodevelopmental syndromes, such as autistic spectrum disorder (ASD), cognitive deficiency, and sensory deprivation, as well as in typically developing children. The movements are variable (body rocking, hand flapping, finger wiggling, and head nodding) but typified by a fixed, repetitive pattern. On the basis of the presence or absence of other developmental problems, they are subclassified into primary (physiological) and secondary (associated with neurological or sensory impairment) categories. Attempts to identify specific characteristics of movements that would assist in differentiating primary from secondary causes have been unsuccessful. Motor stereotypies should not be confused with other common paroxysmal disorders such as tics, obsessive–compulsive behaviors, and epileptic automatisms. Although a psychogenic basis has been proposed, there is increasing support for an underlying neurobiological mechanism. Evidence for the use of medications to suppress motor stereotypies in the nonautistic population is lacking, whereas behavioral therapy may be of benefit.
The definition of a motor stereotypy is quite broad: ‘involuntary, coordinated, patterned, repetitive, rhythmic, and purposeless but seemingly purposeful movement’ . Other supplementing criteria have included nonreflexive rhythmic movements, which last for seconds to minutes, occur in clusters, and appear many times per day; associated with periods of stress, excitement, fatigue, or boredom; briefly affected by an ongoing excited activity but do not interfere with the ability to perform tasks; and readily suppressible by distraction or initiation of another action . On the basis of DSM-IV criteria, the repetitive, nonfunctional behaviors must be present for at least 4 weeks and markedly interfere with normal activities or possibly cause self-injury. Finally, we believe that motor stereotypies should be distinguished from other ritualistic and inflexible behaviors that often occur in children with ASD, for example, circumscribed interests and routines, preoccupation with certain objects, unusual sensory responses, and social communication difficulties .
Clinical features of physiological stereotypies
Motor stereotypies usually begin in the first several years of life, most commonly before 3 years of age. The movements are paroxysmal, last for seconds to minutes, appear multiple times a day, and have a fixed pattern. Each child has his or her own distinct repertoire, such as flapping or waving, which is repeated in the same manner each time. Some children have accompanying movements such as extension of the head, mouth stretching, and eyelid closure. Others may pace while performing the repetitious movement. It is not uncommon to see an evolution of movements or more than one stereotypy in the same child. Stereotypies typically occur when the child is engrossed in stimulating activities, excited, stimulated, stressed, or fatigued. During the event, other activities may cease, though there is no loss of awareness. A classical finding is that movements abruptly cease when the child is cued or distracted, though they may immediately return to performing the activity. The child usually does not have a premonitory urge to perform the activity, though occasionally may report pleasurable feeling. Unlike tics, there is no build up of ‘inner tension’ while attempting to suppress. Phonations may occur during the movement. In contrast to repetitive movements defined as rhythmic behaviors of sleep, the stereotypies being discussed are usually not present during sleep. They can be distressing for parents but usually are not of concern for the patient, whose daily activities are rarely affected.
The precise prevalence rate of primary motor stereotypies is unknown, estimates varying widely depending on the study location and types of movements that were included (see Table 1) [4–9,10•,11••,12••]. Several reports have suggested a higher rate of motor stereotypies in boys as compared with girls, about a 3: 2 ratio [9,10•,12••]. Comorbid issues of tics, attention deficit hyperactivity disorder (ADHD), and obsessive–compulsive behaviors are common [12••]. The outcome of stereotypies in typically developing children has been controversial. Some investigators believe that the movements start in infancy, escalate during the third year of life, and then decline after 4 years of age, but others have noted that children continue to experience these movements even beyond adolescence [13,14].
Differentiating stereotypies from other disorders
Stereotypies should be distinguished from other movement disorders, tics, and epileptic automatisms.
Mannerisms are gestures or sets of movements that are unique to the individual and generally attached to a normal activity.
Complex tics are characterized by a cluster of simple tics or a more coordinated sequence of intermittent movements (hop, jump, and knee bend). Complex tics have several overlapping features with motor stereotypies; both are periodic in nature, patterned and exacerbated by stress, anxiety and fatigue. In contrast, there are a number of features that distinguishes the two disorders: stereotypies have an earlier age of onset (<3 years) than do tics (mean onset 6–7 years); they are more constant and fixed in their pattern as compared with the more variable action of tics; they involve arms, hands, or the entire body rather than eye blinks, facial grimaces, head twists, or shoulder shrugs; they are more rhythmic, with flapping and waving, than are tics that tend to be rapid and random; stereotypies are not associated with premonitory urges or desires to reduce an inner tension; although both may occur during periods of excitement or stress, stereotypic movements occur when the child is engrossed in an activity (e.g. computer game, arcade game); and stereotypies can be stopped by distraction, although rarely does the child make a conscious effort to control, whereas tics are usually briefly suppressible.
Compulsions are repetitive behaviors or rituals (e.g. hand washing) that are performed to relieve anxiety caused by obsessive thoughts or intrinsic rules. Tics and compulsive behaviors can be seen in conjunction with stereotypies in some children.
Paroxysmal dyskinesias are usually chorea or dystonia that may be precipitated by voluntary movements (kinesigenic) or exertion.
Automatisms involve repetitive movements of eyelids, mouth, tongue, or arms in the setting of a focal onset seizure, with or without loss of consciousness. Direct visualization on video electroencephalogram (EEG) is helpful in establishing a diagnosis.
The basic pathophysiologic mechanism of motor stereotypies is unknown. Hypotheses range from psychological concerns to neurobiological abnormalities. Proponents of a psychogenic mechanism tend to suggest a form of self-stimulation, an attempt to use up excess attention capacity or to reduce external distractions, an obsessive–compulsive or general anxiety disorder, or impulse dyscontrol [15–17]. A neurological basis for stereotypies is supported by its association with disorders of the central nervous system, such as autism and mental retardation, its onset after brain insults, and its pharmacological induction in animal models and in humans. The precise neuroanatomical localization for motor stereotypies is unknown, though investigators have suggested abnormalities located within cortico-striatal-thalamo-cortical pathways [18–23]. An abnormality of dopamine neurotransmission has also been implicated. Neurodiagnostic evaluations including routine EEG and MRI scans in typically developing children with stereotypies are unremarkable. On the basis of a positive family history of motor stereotypies in 25% of first-degree relatives of typically developing children, Mendelian inheritance has been suggested [12••]. Genetic studies are awaited in this population.
Classification of stereotypies
Repetitive motor stereotypic behaviors are common in children with autism, mental retardation, sensory deprivation, as well as typically developing children. A favored classification subdivides by cause into primary and secondary categories, dependent on the existence of other behavioral or neurological findings (Table 2). Although some investigators have suggested that a particular movement or its duration may be more indicative of a secondary type, others have emphasized that there is considerable overlap between the two subdivisions.
Stereotypic forms that are observed especially in the primary category, children with normal development, can be categorized into three groups: common (e.g. body rocking, foot tapping, hair twisting, and finger drumming, etc.); head nodding; and complex motor movements (e.g. repeated raising and lowering of the arms, hand waving and flapping, finger wiggling, etc.).
Movements in this category have frequently been labeled habits. Numerous behaviors are included including thumb sucking, nail biting/chewing, rocking, hair twirling, finger and foot tapping, and others. The total prevalence rate of stereotypies in children is estimated to be 22–72% [4,7,11••]. The most common movements are: in infancy and early childhood, thumb sucking and body rocking; in preschool children (3–5 years), thumb sucking and making faces; and in school age children (6–10 years), hair twisting, biting nails and chewing . Some children may initially start with thumb and hand sucking evolve to body rocking and head banging, and later nail biting, finger and foot tapping . More than half of the children (58.5%) indulged in the movements at least once a week. Stereotypic behaviors are also reported in the adult population. Body rocking is a common phenomenon in college students with a postulated incidence rate ranging from 3 to 25% . Students exhibiting common stereotypies frequently had comorbid diagnoses of affective or non-obsessive–compulsive anxiety disorders [5,8]. In healthy adults, common behaviors include touching one's face, playing with hair, pens or jewellery, leg shaking, finger tapping, head scratching, and others .
Repetitive head nodding, consisting of either a side-to-side ‘no’ movement; an up-and-down ‘yes’ movement; or a shoulder-to-shoulder movement, can be a primary stereotypy in normal children. The frequency tends to be of 1–2/s, movements can be stopped voluntarily, and may be associated with up-gaze eye deviations or activity in the hands or feet. This group may have an earlier age of onset than children with complex motor stereotypies. In a small cohort, coexisting findings included hypotonia (5/8), delayed motor and language development (4/8), and ataxia (2/8) . In a study following eight children with typical development and head nodding, three stopped entirely, suggesting the outcome may differ in this category as compared with controls [12••].
Pathophysiological mechanisms have ranged from a congenital brainstem–cerebellar abnormality to perpetuation of a ‘normal’ motor programme. The differential diagnosis in this group includes Sandifer's syndrome, spasmus nutans, bobble-head doll syndrome (cyst, tumor or dilatation of third ventricle), congenital nystagmus, oculomotor apraxia, and jactatio capitis nocturna.
Complex motor (hand and arm) stereotypies
Movements in this category include hand shaking, posturing, flapping or waving, opening and closing of the hands, finger writhing, arm flapping, and flexion and extension of the wrists. Additional movement patterns may occur in conjunction (e.g. body rocking, leg shaking or kicking, facial grimacing, mouth opening, neck extension, and involuntary noises), but the hand/arm movements are dominant. The precise prevalence of complex stereotypies in normal healthy children is unknown. On the basis of a small study using parent/teacher interviews, it has been estimated to be about 5% in children between the ages of 3–6 years . Further community-based studies, however, are required to confirm this prediction.
Two chart review/telephone follow-up studies have evaluated typical children with complex motor stereotypies and found similar results [9,12••]. In the larger study, involving 100 children (62 boys, 38 girls) with complex motor stereotypies, onset of movements occurred on or before age 2 years in 81%, and in all by 37 months. Movements lasted for less than 10 s in 37%, 11–60 s in 27%, and more than a minute in 37%. Complex stereotypies occurred more than once a day in about 80%. Triggers included excitement/happy (86%), being focused/engrossed (34%), anxiety/stress (27%), and tired/fatigued (21%); more than one trigger was commonly identified. If distracted, in all but one case the movement ceased. In participants 7 years of age and older, that is, beyond the expected age for symptom appearance, 30% had ADHD and 18% had tics. Obsessive–compulsive behaviors were also common in this population. Consistent with a prior report , an extended longitudinal follow-up confirmed that most motor stereotypies were persistent, that is, only 3% stopped, 28% were better, 61% remained stable, and 11% worsened [12••]. Hence, suggestions to parents that complex motor stereotypies are brief and transient appear to be erroneous.
As complex motor stereotypies can occur in typically developing children as well as those who are developmentally delayed or with autism, studies have attempted to compare and contrast movements in these groups. Most studies suggest that there is considerable overlap among movements in each of these groups [27–29,30•]. In contrast, investigators have shown that children diagnosed with either an ASD or cognitive difficulty exhibit higher rates of stereotypic behaviors than age-matched control groups [31,32]. Further, differences in the frequency and intensity of movements between children with developmental disabilities and typically developing children may widen with increasing age [11••]. Secondary stereotypies are often associated with self-injurious behaviors in children with autism and mental retardation .
As motor stereotypies usually do not cause psychosocial or physical problems in the nonautistic population, specific therapy may not be required. To date, the authors are unaware of any formal studies investigating the benefit of pharmacological agents for suppression of primary stereotypies. Although isolated case reports have suggested a role for clonazepam, naltrexone , haloperidol or clonidine , we have not found most of these agents to be beneficial. In a small number of nonautistic children, the combination of two behavior modifying techniques, habit reversal and differential reinforcement of other behaviors, was beneficial in reducing motor stereotypies . In the autistic or retarded population, many with associated self-injurious behaviors, the response of stereotypic movements to medications is generally inconsistent.
Motor stereotypies in the typically developing child are relatively common and can be divided into three subgroups. The complex group has movements that mimic those seen in autistic or mentally retarded children. Stereotypies tend to persist and the role of pharmacotherapy has not been established. The underlying cause and pathophysiology of these movements requires further investigation. Preliminary investigations suggest Mendelian inheritance and involvement of frontal–subcortical circuits.
References and recommended reading
Papers of particular interest, published within the annual period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Additional references related to this topic can also be found in the Current World Literature section in this issue (pp. 000–000).
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