Adrian D. Sandler
Parents often raise concerns about rhythmic and repetitive behaviors such as rocking, head banging, and thumb sucking. Learning theorists contend that rhythmic movements begin as normal behaviors that are reinforced over time. Some complex repetitive movements represent genetically coded, species-specific behavior. Observations of picking and grooming behaviors among primates suggest that hair twisting and pulling may originate from social behavior of our human ancestors.
The emergence of abnormal repetitive behaviors after severe brain injury and the frequent stereotypies in individuals with severe cognitive disabilities indicate that human cortical functions may inhibit “deeper” and more primitive repetitive behaviors.
The clinical significance of repetitive behaviors in children depends on the characteristics of the behavior (the kind of movements, their frequency, and timing), the context (the age of the child, when it occurs, what makes it worse), and the impact of the behavior on health and function.
A consideration of the function and meaning of the behavior helps us in classifying repetitive behaviors as habits, stereotypies, tics, or compulsions.
CLASSIFICATION OF REPETITIVE BEHAVIORS
Habits are assembled routines that link sensory inputs with motor outputs through procedural learning. Common habits, including rocking, head rolling, head banging, hair twirling, thumb sucking, nail biting, nose touching, teeth grinding, and joint popping, are not strongly associated with neurodevelopmental disorders or neurological disability.
Most habits serve a self-soothing function at times of stress or boredom. Children engage in these behaviors voluntarily but may learn to inhibit the behaviors. Some habits are most evident as children are settling for sleep or during sleep (sucking movements and teeth grinding), when cortical inhibition is diminishing. Among school-aged children, habits may be seen during times of concentration and focused effort. Habits may be associated with negative mood states, especially anxiety. Anxious children are more likely to engage in a variety of habits, but “nervous habits” do not necessarily imply the presence of an anxiety disorder.
When a child engages in a habit to the extent that it interferes with daily functioning, the term habit disorder is appropriate. Some habits may evolve into patterns of behavior that are sufficiently recognizable or unusual to warrant a specific diagnostic term, especially if the habits are causing harm to the child. Onychophagia (nail biting) can cause paronychia, bruxism (severe teeth grinding) can wear down the surfaces of teeth and cause temporomandibular joint pain, trichotillomania (hair pulling) can cause highly visible and stigmatizing alopecia, and pica (persistent craving for and ingestion of nonfood items) can cause nutritional problems and poisoning.
Stereotypies are repetitive, rhythmic movements that may resemble common habits (rocking, head banging) or appear bizarre and idiosyncratic (unusual hand movements). They include intrusive and potentially harmful behaviors, such as self-injurious behavior. They may involve specific objects and props, such as strings used for twirling and corners of furniture used for head banging.
Children with neurodevelopmental disorders and disabilities are much more likely to have stereotypies than are typically developing children. Indeed, engagement in repetitive behaviors is one of the cardinal diagnostic criteria for an autism spectrum disorder. Blind children may engage in repetitive movements that are sometimes referred to as blindisms. The term stereotypy implies the likelihood of underlying abnormality of brain function. When stereotypies interfere with activities of daily living or result in significant injury, the diagnosis of stereotypic movement disorder is appropriate. Stereotypies typically increase during unstructured times and periods of boredom, and they subside when the children are provided with appropriate structure and stimulation. For many children with autism, engaging in their particular stereotypies provides sensory inputs that appear to be deeply rewarding.
Tics can be described as brief, rapid, coordinated, isolated fragments of normal motor or vocal behaviors. They can be easily mimicked. They do not occur continuously and rhythmically (like thumb sucking) but as discrete movements interspersed with tic-free periods. Motor tics are typically brief clonic movements of eyes, face, neck, and shoulders, with eye blinking, facial grimacing, and head jerking the most common. Vocal or phonic tics include repetitive throat clearing, grunting, or barking.
Children as young as 6 years with tics describe premonitory sensory urges, a kind of pressure or “itch.” These distracting urges may interfere with concentration and contribute to attentional problems. Tics are not entirely involuntary and may be experienced as intentional surrender to almost irresistible sensory urges, usually accompanied by a fleeting and incomplete sense of relief.
Tics may be described in terms of location, number, frequency, and duration. They may also be characterized by their intensity, forcefulness, and complexity. Whereas tics are most commonly simple (brief and meaningless), they may be complex (longer and more elaborate).
Compulsions are complex, ritualistic, and purposeful behaviors. They are most often seen as part of obsessive-compulsive disorder (OCD), a behaviorally defined psychiatric disorder characterized by obsessional anxiety and compulsive behaviors. Compulsions may occur in individuals who do not fully meet criteria for OCD, and they are commonly present in children with tic disorders and anxiety disorders. Common compulsions include repetitive checking, elaborate bedtime rituals, counting, matching, and other perfectionistic preoccupations.
The child who engages in compulsive behaviors understands that the behavior is excessive, inappropriate, or “doesn’t really make sense,” but still he or she feels compelled to do so, sometimes “to stop bad things from happening.” Engaging in the behaviors is in this sense involuntary, associated with embarrassment and shame, but also with some relief from the anxious sense that “something is wrong.”
SPECIFIC DISORDERS AND CLINICAL SYNDROMES
Tourette syndrome is a developmental neuro-psychiatric disorder characterized by multiple motor and vocal tics (not necessarily concurrent), lasting a period of at least 1 year, in which the individual is never tic-free for more than 3 consecutive months. Onset is before age 18 years, in some cases as young as 2 or 3 years, with peak onset around 5 to 8 years. Although there is wide variability in symptoms and clinical course, there is a tendency for severity to peak around 9 to 11 years. Improvement or even resolution by mid to late adolescence is likely, with only 20% continuing to show moderate global impairment by age 20 years.2,3 For further discussion see Chapter 566.
TIC DISORDER SPECTRUM
Transient tic disorders include single or multiple motor and/or vocal tics, lasting at least 4 weeks up to 12 months. Most transient tics are simple rather than complex, and they do not usually cause great distress. A child with complex and distressing motor and vocal tics lasting a few months may be at risk for developing Tourette syndrome. Chronic tic disorders are single or multiple motor or vocal tics that last more than a year.
Trichotillomania is a mental health disorder and is considered among the spectrum of obsessive-compulsive disorders.5 It is characterized by pulling out one’s hair, resulting in noticeable hair loss and occasional trichobezoars (hair balls). The behavior is associated with tension immediately prior to or when attempting to resist and with gratification or relief immediately after pulling out the hair.
STEREOTYPIC MOVEMENT DISORDER/SELF-INJURIOUS BEHAVIOR
Stereotypies and self-injurious behavior (SIB) can cause severe distress to individuals and their caregivers, even resulting in institutional care or severe injury (eg, Lesch-Nyhan syndrome). Typically, individuals who engage in SIB display a specific pattern of behavior, including head banging, hand or wrist biting, skin picking, hitting themselves with their fists, or poking their eyes. Although most SIB does not cause significant injury, tissue destruction, infection, loss of vision, and life-threatening injury may occur.6
Sporadic pica is common in toddlers, but persistent pica suggests the presence of psychiatric disorder, nutritional deficiency, or a neurodevelopmental disorder (eg, autism and mental retardation). Toxicity from ingestion underscore the importance of close supervision and environmental safety precautions.
Rumination is habitual regurgitation of food, which is then reswallowed or chewed. This habit may begin when infants insert their hands into their mouths or as a result of gastroesophageal reflux (common in children with neurodevelop-mental disorders). Regurgitation and vomiting may be reinforced by attention from caregivers or other stimulation, leading to rumination (repetitive regurgitation). Rumination can be challenging to caregivers and may be associated with problems of oral and dental health.7
PREVALENCE OF COMMON HABITS
Rocking, head rolling, and head banging occur in 5% to 15% of young children, with typical onset around 6 to 9 months of age.8 Rocking and head rolling usually cease by 2 to 3 years, head banging by age 4. Head banging is 3 times more frequent in males than females. Thumb sucking occurs in 13% to 31% of North American children under 4 years of age, with an equal distribution between boys and girls.9Thumb sucking peaks between 18 and 21 months of age, and most children spontaneously drop the habit by 4 years. Persistent thumb sucking into adolescence occurs more frequently in girls and may indicate underlying insecurities or other psychological problems.
Approximately 50% of children have habitual nail biting at some time in childhood. Onset is as early as 3 to 4 years, with peak prevalence at 10 to 18 years.
The prevalence of bruxism is difficult to ascertain because it occurs mostly during sleep. Parents acknowledge this habit in 15% of children between the ages of 3 and 17 years. Trichotillomania may present before age 5 and recur or persist for many years.
EPIDEMIOLOGY OF TIC DISORDER SPECTRUM
Simple tics are very common in childhood: 5% to 13% of all children experience a transient tic during childhood.10 The childhood incidence of chronic tic disorder is around 1% to 2%, with a ratio of approximately 3:1 of boys to girls. In contrast, TS is much less common, around 5 to 10 per 10,000. Neither race nor socioeconomic status is strongly related to risk of tic disorders.
Epidemiologic studies support a joint etiology of Tourette syndrome (TS) and obsessive-compulsive disorder (OCD). More than 50% of children with TS have extensive obsessions and/or compulsions. Forty percent of children with TS and more than 20% of all children with tic disorders have OCD. Many children with TS have clinical depression or anxiety. Sleep disturbance13 and learning disabilities may be present in more than 20% of patients with TS.14,15 Psychiatric comorbidity in children with OCD is common, including tic disorders (18%), attention deficit hyperactivity disorder (ADHD), depression, and other anxiety disorders.
Children with TS are frequently diagnosed with ADHD, although comorbidity rates are controversial, ranging from 8% to 70%.17
PATHOPHYSIOLOGY AND GENETICS
The underlying cause of habit disorder, stereotypies, and self-injurious behavior (SIB) varies among individuals and may include both environmental and biological factors. A child may learn that he gets the attention he wants or avoids an activity that he dislikes by engaging in SIB. Another child may engage in SIB because it appears to increase sensory stimulation. A third child may begin head banging because of a previously undiagnosed painful medical condition (eg, gastroesophageal reflux, dental decay, or ear infection).
GENETICS OF TIC DISORDERS, TOURETTE SYNDROME, AND OBSESSIVE-COMPULSIVE DISORDER
The precise etiology of these conditions is not known. Twin studies show moderate heritability, but nongenetic factors influence phenotypic expression. Linkage studies have not identified a single strong candidate region, but several areas of interest on many chromosomes have been identified, including 11q23, 4q, 8p, 3q, 9q and 13q.20 Recent provocative evidence regarding a candidate gene SLITRK1mapping from 13q31 may provide clues about the biologic pathways that lead to Tourette syndrome.21 It is likely that genetic vulnerability, environmental stressors, and epigenetic influences cause increased dopamine hyper-sensitivity in the basal ganglia of the developing brain.
Patients with Tourette syndrome have higher levels of psychosocial stress, and antecedent stress can increase future tics and obsessive-compulsive disorder symptom severity.23
NEUROBIOLOGY OF TIC DISORDERS AND TOURETTE SYNDROME
Advances in understanding the neurobiology of Tourette syndrome using in vivo neuroim-aging and neurophysiology techniques implicate specific cortico-striato-thalamo-cortical circuits important for procedural learning, initiating, and inhibiting psychomotor activity and harm detection/avoidance.2 In the largest study of basal ganglia volume, involving 154 participants with TS and 130 healthy controls, caudate volume was significantly decreased in both children and adults with TS.25 Cortical disinhibition may be related to hypersensitivity of dopamine D2 striatal receptors.
PEDIATRIC AUTOIMMUNE NEUROPSYCHIATRIC DISORDERS ASSOCIATED WITH GROUP A STREPTOCOCCUS
Pediatric autoimmune neuropsychiatric disorders associated with group A streptococcus (PANDAS) is a controversial diagnosis based upon circumstantial evidence that suggests that antineuronal antibodies associated with streptococcal infection are affecting basal ganglion function. A case-controlled study of 144 children diagnosed with obsessive-compulsive disorder, Tourette syndrome, or tic disorder, indicated that cases had a higher likelihood of streptococcal infection in the 3 months before onset date than did controls.31 Multiple infections with group A streptococcus within a 12-month period was associated with an increased risk of Tourette syndrome with odds ration of 13.6 (95% confidence interval 1.93–51.0). But a more recent clinical study that found that only a small proportion of “PANDAS” exacerbations are temporally related to streptococcal infection.32 PANDAS may be episodic, and recurrences are common. Anti-DNAase B and other antistreptococcal antibody titers may be very high, and elevated antineuronal antibodies have been reported.33 However, a recent study did not confirm a relationship between antineuronal antibodies and clinical exacerbations.34
CLINICAL FEATURES AND DIFFERENTIAL DIAGNOSIS
Habits, stereotypies, tics, and compulsions are clinical diagnoses, and there are no specific tests. Video resources can be very helpful in developing the clinical skills needed to distinguish normal from abnormal or to clarify the nature of an observed repetitive behavior.35,36
The differential diagnosis includes allergic rhinitis, seizure disorder, movement disorders, and Sandifer syndrome (gastroesophageal reflux–associated lateral movements of head and neck). Children with allergies often have recurrent throat clearing and sniffing, but tics are more repetitive and less variable. Brief epileptic seizures are usually accompanied by mental status changes such as diminished responsiveness. Complex partial seizures of temporal lobe epilepsy are usually staring episodes lasting 1 to 2 minutes with little or no movement, followed by confusion or tiredness.
One common repetitive behavior that deserves special mention is masturbation and other related movements associated with genital stimulation in infants and children.37 Parents may be alarmed by their child’s repetitive pelvic movements, usually while lying prone, sitting on a firm surface, or straddling an object. Such movements may be intense and associated with mental status and autonomic changes, such as staring and sweating. A review of a home video is generally sufficient to clarify the nature of the repetitive behavior, and explanation and reassurance can be a relief to incredulous parents.
Evaluation of repetitive movements includes detailed medical and developmental history, child interview if possible, observation, and careful neurological examination. For sporadic behaviors that are not evident in the clinic, home video can be useful.
Clinical evaluation of common habit disorders should include an assessment of potential impact on the child’s health. Persistent thumb sucking beyond 4 years of age may cause orthodontic and speech problems. Severe bruxism can cause dental problems and temporomandibular joint pain. Pica can be associated with nutritional deficiencies and toxic ingestion. Referral to pediatric dentists, nutritionists, and behavioral specialists may be important in thorough evaluation.
Evaluation of stereotypies includes assessment of the context in which the behavior occurs and of the impact on the child (his or her emotional, social, and school experiences) and family. A useful framework is the functional behavioral assessment, including an analysis of antecedent circumstances, factors that increase or decrease the behavior, and caregiver responses to the behavior.38
Evaluation of self-injurious behavior should include an assessment of the risk of physical harm. Severe head banging may cause brain injury or eye injury, necessitating the use of protective headgear.
Evaluation of tics should also be comprehensive and holistic. It is important to ask the child and family about the time course of tics and compulsive behaviors, relationship to medication use, and possible exacerbating factors. Specific inquiry about recent or previous streptococcal exposures or infections should be made. The history should include screening questions regarding anxiety symptoms, obsessive-compulsive disorder, attention deficit hyperactivity disorder, learning problems and depression, and family history of tic disorders and associated conditions.
Physical and neurological examination is important to rule out other movement disorders. Children with Tourette syndrome usually have a normal examination other than tics. Many children effectively suppress tics during the clinic visit, and the absence of tics does not preclude a diagnosis of tic disorder.
There are no specific diagnostic tests for tics, compulsions, and stereotypies. Electroencephalographs and imaging studies are not routinely indicated. If there are clinical indications of pediatric autoimmune neuropsychiatric disorders associated with group A streptococcus (PANDAS), including sudden onset of symptoms and known exposure to streptococcus, most clinicians obtain streptococcal culture, antistreptolysin O titers, and anti-DNAase B, however, the efficacy of therapy for this disorder is controversial.
Common habits generally require no more than explanation and reassurance that the behavior is benign and self-limited. Parental efforts to dissuade a child from thumb sucking may cause anxiety or resentment and reinforce the behavior. A better approach is for parents to ignore the habit, while selectively giving praise during times when the child is not sucking. Head banging is still harder for parents to ignore. It may be helpful for the parent to pad the area that the child uses for this habit or to set limits whereby such behavior is permitted in one place only.
Some repetitive behaviors may be reinforced by parental attention, and ignoring such behaviors may lead to escalation and intensification of the behavior. Parents should be advised that such an increase in problem behavior is likely to be short lived. Some children may respond positively to parental behavior modification efforts but then substitute a new habit for the old discarded one.
Aversive treatments have been used for some habits, such as thumb sucking and nail biting (eg, bitter nail polish). It is generally helpful for the parent to make the child a partner in these treatment efforts so that they are not experienced as punitive. Concerns about complications may make other more invasive interventions necessary, such as dental appliances (plate with palatal bar) for thumb sucking or bite guard for bruxism.
Hypnotherapy is a treatment modality that may be well suited to pediatric habit disorders. Hypnotherapy has also been used successfully to treat children and adolescents with trichotillomania.40 Additional behavioral techniques include relaxation training and habit reversal procedures, such as teaching a child to engage in a hand grasp whenever they feel the urge to bite nails.
PICA AND RUMINATION
The same general principles of management apply to these habit disorders. Pica and rumination are often done during unstructured time and when the child is alone or unsupervised. A behavioral plan should be established that increases structured activities, significantly decreases unsupervised time, and provides redirection and rewards. Diaphragmatic breathing may be helpful to suppress rumination.
STEREOTYPIES AND SELF-INJURIOUS BEHAVIOR
Management of these conditions includes functional behavioral assessment and development of a behavioral intervention plan, sometimes requiring assistance from a psychologist with experience in developmental disabilities. In severe cases and those that do not respond to behavioral interventions alone, a trial of an atypical antipsychotic may be indicated, in consultation with a subspecialist experienced in pediatric psychopharmacology. Risperidone is approved for the treatment of aggression and severe behavior problems in children with autism, ages 5 through 16 years, and it has been very useful in decreasing stereotypies and SIB in children with autism and other developmental disabilities.41
TIC DISORDERS AND OBSESSIVE-COMPULSIVE DISORDER
Tics that are at least moderately severe and interfering with daily life should be treated. Education and demystification for the affected child, his or her family, and school personnel help to promote support and tolerance, reinforcing the message that the tics are involuntary. Some children may benefit from individual psychotherapy to improve self-esteem, social coping, school adjustment, and family stress.
Habit reversal psychotherapy involves increasing the individual’s awareness of the tics and establishing a competing response. Effectiveness in Tourette syndrome is not well established. Cognitive behavior therapy involving repeated exposures and response prevention (using cognitive techniques to change patterns of response) is of benefit in obsessive-compulsive disorder, sometimes enhancing medication response or allowing responders to discontinue medications.42
Pharmacotherapy is the cornerstone of treatment of tic disorders, but tics should not be treated too aggressively if they are not causing major functional impairment. The presence, scope, and severity of comorbid diagnoses (attention deficit hyperactivity disorder, obsessive-compulsive disorder, depression) should be assessed in planning pharmacotherapy.
Clonidine and guanfacine may be useful first-line medications in tic disorders and TS. Sedation is the major side effect, especially for clonidine.
In children who have attention deficit hyperactivity disorder (ADHD) and tics, the α-2 agonists are not likely to be effective in improving attentional problems. A trial of stimulant therapy may increase tics in one third, have no effect on tics in one third, and lead to improvement in tics in one third.45 The combination of methylphenidate and clonidine in children with Tourette syndrome and ADHD is generally more effective than either medication alone.
The selective serotonin reuptake inhibitors are of proven effectiveness in the treatment of OCD.42 In children with TS, OCD, and ADHD, who may be more impaired from their OCD and ADHD symptoms than from their tics, a combination of SSRI and stimulant may be helpful. In children with positive culture and/or serologic evidence of recent streptococcal infection and a clinical presentation consistent with PANDAS, a course of penicillin may be helpful.31
Neuroleptics such as haloperidol can be quite effective in treating severe tic disorders.2,46 Long-term use can cause tardive dyskinesia and other extrapyramidal side effects. Pimozide may have fewer extrapyramidal side effects but can cause QT prolongation. These medications may also cause sedation, personality change, and weight gain.
Atypical antipsychotics block dopamine and serotonin receptors. Risperidone, a potent D2 antagonist, has proven effectiveness in short-term clinical trials in children and adults with TS.47 Doses ranging from 1.0 to 3.5 mg/day were effective, and extrapyramidal side effects were rare. The most common adverse effects were weight gain, lipid abnormalities, and sedation.
PROGNOSIS AND OUTCOME
Habits generally resolve spontaneously during childhood, although nail biting and other oral habits are common in adults. Efforts to stop a habit or stereotypy through behavioral reinforcement may be successful, but the resolution of one habit may be followed by the emergence of another.
Children with tics and compulsions may work hard to suppress their symptoms. Social learning and behavioral reinforcement may modify expression of repetitive behaviors over time. Children may learn to mask their tics and compulsions in a way that makes them seem less unusual or intrusive. The frequency of tics tends to decrease during adolescence.
Severe stereotypic movement disorder and self-injurious behavior has the potential to cause neurological injury or cataract formation. Tourette syndrome and obsessive-compulsive disorder can be socially disabling and stigmatizing. Moreover, associated conditions, including attention deficit hyperactivity disorder, learning disabilities, and depression, may cause severe impairments. Medications used in the treatment of tic disorders, obsessive-compulsive disorder, and stereotypies may cause iatrogenic complications.