Movements disorders are neurologic syndromes that involve impaired performance of voluntary movements, dysfunction of posture, the presence of abnormal involuntary movements, or the performance of normal-appearing movements at inappropriate or unintended times.^1,2 These movement abnormalities are not due to weakness or spasticity. Movement disorders are traditionally divided into hyperkinetic disorders and hypokinetic disorders. Hyperkinetic movement disorders are characterized by an excess of movement, whereas hypokinetic movement disorders are characterized by a paucity of movement. In childhood, hyperkinetic movement disorders are far more common than hypokinetic movement disorders. Hyperkinetic movement disorders include tics, stereotypies, chorea, athetosis, ballism, dystonia, myoclonus, and tremor. The primary hypokinetic movement disorder is parkinsonism, which is characterized by bradykinesia, tremor, rigidity, and postural instability. Parkinson’s disease, which is the most common hypokinetic movement disorder in adults, is exceedingly rare in children.

Movement disorders arise from abnormalities in the basal ganglia circuits. The basal ganglia are subcortical structures including the striatum (caudate, putamen, nucleus accumbens), the subthalamic nucleus, the globus pallidus (internal segment, external segment, ventral pallidum), and the substantia nigra (pars compacta, pars reticulata). Input to the basal ganglia come from the cerebral cortex and the thalamus. Most of the output of the basal ganglia is from the globus pallidus internal segment, ventral pallidum, and substantia nigra pars reticulata. The output is predominantly inhibitory to the brainstem and to the thalamic nuclei, which project back to the cerebral cortex. These complex circuits function to facilitate wanted patterns of movement and inhibit unwanted patterns of movement. In addition to motor control, the basal ganglia likely have a role in cognitive and emotional control.²

Of importance to the clinician, the basal ganglia and the cerebellum function together in their control of the corticospinal and extrapyramidal systems. Corticospinal syndromes are characterized by the loss of volitional movement with spasticity. In contrast, extrapyramidal syndromes are characterized by the presence of involuntary movements (Table 62–1).

Multiple schemes are used to classify movement disorders. They can be classified based on clinical features (e.g., age of onset, body distribution, phenomenology, response to treatment), etiologic criteria (primary vs. secondary), anatomic localization, neuropathologic findings, or genetic and molecular criteria.^3–7 Often, multiple classifications systems are used simultaneously. For example, dystonia can be classified by both clinical features and etiology.^8,9 Numerous challenges to the classification of movement disorders exist, including variable terminology, genetic heterogeneity, clinical heterogeneity, and genetic discovery.⁴ Over time, classification schemes continue to change as our understanding and ability to diagnose movement disorders advance.

The first step in the evaluation of a child with a movement disorder is to determine whether the movement in question is normal or abnormal. While this sounds simple, it can be challenging to distinguish between normal and abnormal movement patterns in the pediatric population because they change depending on the age of the child. For example, chorea in an infant may be normal, whereas the same chorea in a toddler is abnormal. The next step is to determine whether the movement is hyperkinetic or hypokinetic. Once this broad category is established, the specific type of movement disorder or combination of movement disorders must be ascertained. Evaluating the following components of the abnormal movement can help identify the specific type of movement disorder that is present: (1) phenomenology (duration, speed, amplitude, jerkiness, repeatability or stereotyped quality, number of different identifiable movements or postures), (2) time course (rhythmicity, intermittent vs. continuous, ongoing or sustained, presence of discrete movement fragments), (3) triggers (relationship to voluntary movement, posture, rest, and emotional state), (4) suppressibility or distractibility, and (5) distribution of affected body parts.⁶ In many children, particularly those with secondary movement disorders, multiple movement disorders may be present in the same child, making this process even more challenging. The correct classification of the movement disorder is crucial because it guides further diagnostic evaluation and treatment plans and influences prognosis.

Every child presenting with a movement disorder should undergo a complete history, including birth history, developmental history, and family history, as well as a general physical examination and a complete neurologic examination. Key components of the general examination include evaluation for dysmorphic facial features, abnormalities in head size or shape, heart murmurs, organomegaly, midline back defects, and limb/joint abnormalities, as well as a thorough skin examination for pigmentary abnormalities. A complete neurologic examination includes mental status testing, expressive and receptive speech evaluation, cranial nerve testing, motor examination (bulk, tone, strength, reflexes, abnormal movements), sensory examination, cerebellar examination, and gait examination. If the involuntary movement is not present during the visit, it is very helpful to have the family provide a video of the movement in question.

Tic Disorders

Tics are repeated, individually recognizable, intermittent movements or movement fragments that are almost always briefly suppressible. Tics are usually associated with an awareness of an urge to perform the movement.⁶ Key characteristics of tics include (1) waxing and waning pattern, (2) changing nature with admixture of new and old tics, (3) sense of a premonitory urge, and (4) ability to suppress the tic for variable amounts of time. Tics most commonly involve the face and upper body. Tics worsen during times of stress, anxiety, excitement, fatigue, or illness and tend to improve during focused concentration.

Tics can be divided into motor tics and phonic tics. They are further subdivided into simple or complex tics. Simple motor tics include eye blinking, facial grimacing, and shoulder shrugging. Simple phonic tics include sniffing and throat clearing. Complex motor tics include a sequential pattern of multiple tics or actions that may appear purposeful such as repetitive touching. Complex vocal tics include echolalia (repeating other’s words), palilalia (repeating one’s own words), and coprolalia (the uttering of obscenities).

The classification of tic disorders is detailed in the Diagnostic and Statistical Manual of Mental Disorders, 5th ed. (DSM-5), and is based on the types of tics that are present as well as on the duration of the tic disorder.¹⁰ A provisional tic disorder is diagnosed when tics have been present for less than 1 year. Persistent (chronic) motor or vocal tic disorder is diagnosed when either motor or vocal tics are present for more than 1 year. Tourette’s disorder is diagnosed when multiple motor and at least one vocal tic have been present for more than 1 year.

Prior studies have shown that transient tic disorders occur in about 20% of children, chronic tic disorders in about 1.6%, and Tourette’s syndrome in about 0.5% to 1%.^11–13 Tics are more common in boys than in girls with a 3–4:1 ratio.^11,14 Additionally, tics are commonly associated with comorbid conditions including attention deficit–hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), anxiety, mood disorders, sleep disorders, learning disabilities, and behavioral disorders. Screening for these conditions should occur during the evaluation of a child with tics.

If tics are not disruptive to the child’s day-to-day life, no treatment is needed. Often education of parents, children, and teachers is the only intervention needed. If tics are causing psychosocial problems or physical pain, behavioral therapy and/or pharmacotherapy can be considered (Table 62–2). The primary behavioral intervention for tics is habit-reversal therapy, for which efficacy and safety have been shown in randomized, blinded, controlled, trials.¹⁵ For pharmacologic management of tics, the first-line treatment is typically with nonneuroleptic medications. There is evidence for the efficacy of the alpha₂ agonists (clonidine and guanfacine)^12,16 and topiramate.^17,18 Second-line treatment of tics includes the dopamine-receptor antagonists such as the typical neuroleptics haloperidol, pimozide, and fluphenazine,^19,20 as well as atypical neuroleptics such as risperidone^21–23 and aripiprazole, among others.^24–26 While these medications are effective, side effects including the risk of tardive dyskinesia often limit their use.

Stereotypies

“Stereotypies” are defined as involuntary, patterned, repetitive, simple movements that can be voluntarily suppressed that often appear rhythmic and occur in the same fashion with each repetition.^6,27,28 They often involve a simple repetitive back-and-forth movement such as waving, flapping, or rocking. Stereotypies also can involve a more complex sequence of movements. A key feature of stereotypies is that they can be stopped with distraction. Stereotypies tend to occur during times of excitement, stress, when engrossed in activity, or bored, but they tend not to interfere with activities. The duration of stereotypies is variable, lasting from seconds to hours.

Primary stereotypies occur in typically developing children and are relatively common.²⁸ Secondary stereotypies occur in children with underlying neurodevelopmental disorders such as autism spectrum disorder and Rett’s syndrome.^29,30 Most of time, treatment of stereotypies is not necessary. Behavioral therapies have been used with some success in children with stereotypies.^31,32 In children with neurodevelopmental disabilities, risperidone and aripiprazole have been shown to reduce repetitive behaviors.^33,34

Chorea, Ballism, Athetosis

Chorea is an ongoing, random-appearing sequence of one or more discrete involuntary movements or movement fractions.^6,35 Chorea is present in many different diseases (Table 62–3).

A key features of chorea is that the movements are unpredictable in terms of their timing, location, direction, and duration. The movements may appear to flow from one body part to another. Chorea is continuous, occurring both at rest and with voluntary movement, but does tend to worsen with voluntary movement. When chorea is mild, it can appear that the child is fidgety. Children may attempt to hide their chorea by incorporating the abnormal movement into an apparently purposely movement. Additional signs of chorea include motor impersistence, which is the inability to maintain voluntary muscle contractions.

The following are some examination maneuvers to evaluate for motor impersistence in chorea: (1) “milkmaid’s grasp” (have the child grasp and squeeze the examiners fingers; the grip strength can be felt to vary); (2) “touchdown sign” (have the child raise his or her arms above the head and supinate the arms with the palms out; the child’s arms will tend to involuntarily pronate); and (3) “darting tongue” (when asked to hold tongue protruded, tongue retracts back into the mouth creating a “darting” appearance). Chorea is associated with disorders of the cerebral cortex, basal ganglia, cerebellum, and thalamus.⁶ Causes of chorea include post–streptococcal-associated chorea (Sydenham’s chorea), infections, autoimmune disorders, hyperthyroidism, toxic exposures, medications, and genetic and metabolic disorders.

The treatment of chorea depends on the underlying cause. Secondary chorea often improves after the underlying cause is treated. For symptomatic treatment of chorea, dopamine-blocking medications are the most effective class for reduction of chorea. The first-generation antipsychotics (typical neuroleptics) are most commonly used to treat chorea, although good evidence to support their use is lacking. Second-generation antipsychotics (atypical neuroleptics) are also used to treat chorea, including olanzapine, clozapine, quetiapine, and risperidone, with varying levels of evidence.^36–40 Tetrabenazine, a dopamine-depleting medication, has been shown to be effective for the treatment of chorea.⁴¹ Antiepileptic medications have also been used for the treatment of chorea, including carbamazepine,^42,43 valproate,^42,44 toprimate,^45,46 levetiracetam,^47–49 and gabapentin,^50,51 although evidence again is limited. Surgical interventions such as pallidotomy, thalamotomy, and deep brain stimulation can be considered in selected patients.

Ballism or ballismus is typically considered to be related to chorea. It is characterized by uncontrollable, severe, primarily proximal large-amplitude choreic movements.³⁵ Ballism is most often unilateral (hemiballism) and related to a lesion in the contralateral subthalamic nucleus.⁵²

Athetosis is a slow, continuous involuntary writhing movement that prevents maintenance of a stable posture.⁶ Athetosis differs from chorea in that it occurs in the same body part repeatedly and is slow, smooth, and continuous in contrast to the variable, jerky movement fragments of chorea. Similar to chorea, athetosis tends to worsen with voluntary movement. Athetosis tends to involve the distal extremities and can involve the face, neck, and trunk. Athetosis is most commonly seen in association with dystonia or chorea and may be considered part of the spectrum of dystonia or chorea.^53,54

Dystonia

“Dystonia” is defined as involuntary sustained or intermittent muscle contractions that cause twisting and repetitive movements, abnormal postures, or both.^7,35 The abnormal postures tend to occur in the same direction; are patterned, involving the same set of muscles; and are associated with overflow muscle activation⁸ (Fig. 62–1).

Overflow muscle activation occurs when there is an inability to prevent unwanted contraction of muscles antagonistic or adjacent to muscles involved in the voluntary movement.⁵⁵ Dystonia is triggered or exacerbated by voluntary movement and can fluctuate in severity depending on body position, specific task, emotional state, or level of consciousness.⁷ “Task specificity” refers to when dystonia only occurs during one specific type of activity. Examples of task specificity are writer’s cramp, where the dystonia is only present during writing, and when dystonia occurs while walking forward but not while walking backward. A unique feature of dystonia is the presence of a sensory trick. This occurs when a certain action by the child reduces the dystonia, such as touching the back of the hand allowing a dystonic hand to open more easily.

Dystonia is associated with injury to the basal ganglia, specifically the globus pallidus and putamen, although other brain areas including the cerebellum, brainstem, and cortex can be involved^6,56–58 (Fig. 62–2).

Primary dystonia occurs when dystonia is seen in isolation. Primary dystonia is most commonly due to genetic conditions. Secondary dystonia occurs in a child in whom there are neurologic or systemic disorders in addition to the dystonia. Causes of secondary dystonia are varied and include hypoxic-ischemic injury, central nervous system infections, autoimmune disorders, vascular diseases, cerebral malformations, and metabolic and neurodegenerative diseases (Table 62–4).

The treatment of dystonia is primarily symptomatic with the goal of improving function. Rehabilitation methods include physical therapy, occupational therapy, and speech therapy to prevent orthopedic complications and optimize development, as well as implementation of adaptive technology to assist with activities of daily living and enhance autonomy.⁵⁹ Numerous pharmacologic agents can be considered in the treatment of dystonia (Table 62–5). Children with dystonia of unknown etiology should be considered for a trial of L-dopa. In children with a specific type of dystonia called “dopa-responsive dystonia,” significant improvement or complete resolution of dystonia may be observed following treatment with L-dopa.^59–61 This trial is potentially both diagnostic and therapeutic. The response to L-dopa for other forms of dystonia is more variable.^62,63 Anticholinergic medications, primarily trihexyphenidyl, are generally considered to be most effective for the treatment of dystonia.^60,64,65 Baclofen is widely used for the treatment of spasticity, but evidence for its efficacy in dystonia is limited. It has been noted to reduce pain due to spasticity and provide additional benefit when used in combination with trihexyphenidyl.² If oral baclofen is beneficial but the dose is limited due to the development of side effects, intrathecal baclofen may be a treatment option.^66–68 Botulinum toxin injections are effective for focal and segmental dystonia.⁶⁹ Additional medications may be effective in the treatment of children with dystonia, including clonazepam, tizanidine, clonidine, dopamine antagonists, and dopamine depletors. Finally, deep brain stimulation (DBS) is effective in selected patients with severe childhood dystonia. Outcomes for children with primary dystonia, particularly DYT-1 dystonia, are better than those for secondary dystonia patients.^70–73