Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.226447
Source of Support: None, Conflict of Interest: None
Keywords: Children, hyperkinetic, hypokinetic, pediatric movement disorders, review
Pediatric movement disorders are similar to adults in terms of definitions. They are different from the movement disorders occurring in adults in some ways. Hyperkinetic disorders are more common in children than hypokinetic disorders. The children also have a higher frequency of paroxysmal disorders. The commonest cause of chronic motor disorder is static encephalopathy. Hereditary metabolic disorders are also frequent causes of movement disorders in this population. The neonatal brain has a blood brain barrier which is not mature. The impaired autoregulation and the high metabolic requirements makes this age group vulnerable. Lesche Nyhan syndrome with hyperuricemia in the early age causes self-mutilation, cognitive abnormalities, dystonia and choreoathetosis. It, however, does not cause any neurologic abnormalities in adult brain. [Table 1] summarizes the characteristics of the common movement disorders in childhood while [Table 2] characterizes the etiology of various movement disorders. Drug-induced movement disorders are summarized in [Table 3].
Hyperkinetic movement disorders, also known as dyskinesias, are repetitive involuntary movements, which are manifestations of common movement disorders in children like tics, chorea, dystonia, myoclonus, stereotypies, and tremor. Childhood movement disorders are very common in day-to-day practice in pediatric and pediatric neurology clinics. Hyperkinetic movement disorders occur more commonly in children than in adults. These movements are analyzed according to their speed (slow or rapid) and volition (involuntary or voluntary). The movements may be assessed on repetition (stereotypical or non-stereotypical), on rhythmicity (rhythmic or non-rhythmic), on predictability (predictable or non-predictable), and on the purpose of the movement (purposeful, non-purposeful or semi-purposeful). They are further evaluated on the involvement of muscle groups (distal or proximal, manifesting in the upper or lower limbs, or the face).
They can also be classified as jerky or non-jerky movements. Jerky movements are chorea, ballismus, tics and myoclonus; and, the non-jerky movement are tremors, dystonia and athetosis
Tremor is an involuntary, rhythmic and sinusoidal alternating movement of one or more body parts. It affects a limb, or any body part, plus the head, chin and soft palate.
Tremors can be classified in various ways. A resting tremor is when the affected body part is at rest and not moving, and the effect of gravity is eliminated. It usually disappears during voluntary actions. Some provoking measures such as eye closure or distraction can enhance or bring about the resting tremor. The tremor can be observed in the arm when the individual is walking ('dependent tremor'), and by keeping the hand rested and by counting backwards. The resting tremor in PD might be seen in a single digit. A rest tremor reduces or stops with voluntary movement. It has a frequency of 4 to 5 Hz. The rest tremor is a characteristic feature of Parkinson's disease which is exceptionally uncommon in children. Action tremor occurs during voluntary movement. Postural tremor is seen when the limb is static but held against gravity, such as when the arms are held outstretched in front, or held in a wing beating position. Postural tremor has a frequency of 6 to 12 Hz. Intention tremor, characterized by worsening of tremor on approaching a target is seen in cerebellar disorders. Intention tremor has a slower frequency of 2 to 4 Hz. Dystonic tremors are associated with dystonia; when prominent features of dystonia are present along with tremors, the condition is then classified as “dystonic tremor.”
The causes of tremors include hereditary disorders (essential tremor), metabolic causes (hyperthyroidism, electrolyte abnormalities), degenerative diseases (Wilson's disease), focal lesions (rubral tremor), medications (e.g., valproic acid), and psychogenic tremor., Children with cerebral palsy can have mixed tremors with action and dystonic features.
The therapy for tremors is based primarily on the etiology. Children with essential tremor often do not require treatment since their disability is minimal. The usual options are topiramate and beta blockers.
The word 'chorea' in Greek means 'dance'. Choreic movements occur with a certain grace rather than as sudden, jerky movements. They are involuntary, random and quick movements, most often occurring in the proximal extremities, neck, trunk, and facial muscles, and have a flowing quality. These movements are abrupt, unpredictable, nonrepetitive, nonrhythmic, resulting in a continuous random flow of muscle contractions, and have a variable frequency and intensity. A choreiform movement can merge into a purposeful movement, giving it a dance-like appearance.
Chorea is the second-fastest movement disorder (the fastest being myoclonus), with a duration of 200 to 400 milliseconds. Some patients with chorea [for example, in Huntington's disease (HD)], exhibit brief, fast (<100 msec) muscle jerks that are myoclonic; and/or, longer (>50 msec) co-contracting muscle spasms that are dystonic. Motor impersistence is often seen as a fluctuating strength of the grip (known as the 'milkmaid's grip'), and the hung-up reflexes (sustained contractions and choreic movements of the leg after the knee-jerk reflex). The 'pronator sign' is seen as hyperpronation of the hands with the palms facing outward, when the arms are held over the head. 'Jack-in-the-box' tongue (or the chameleon tongue, a condition where the patient is unable to maintain the tongue in a protruded state, and the tongue moves in and out) may also occur. The tone is severely decreased, enough to render 2% of children bedridden (known as chorea paralytica). It may be exacerbated by voluntary action, stress, and emotions.
The most common causes of chorea in childhood are cerebral palsy, drug-induced chorea (drugs administered to treat human immunodeficiency virus disease, levodopa, phenytoin, carbamazepine and lithium), systemic lupus erythematosus, anti-phospholipid antibody syndrome, and Sydenham's chorea. Choreiform movements in cerebral palsy begin commonly in the third to fifth year of life and may progress during the adolescence period. Huntington's disease in childhood usually presents with cognitive and behavioral changes, myoclonus, dystonia, and parkinsonian features rather than chorea, Choreiform cerebral palsy can mimic benign hereditary chorea, an autosomal dominant disorder that may begin in infancy or early childhood.
Ballism (meaning 'jumping about') is a violent, involuntary, flinging movement of the proximal muscles of the extremities. It has been considered as a severe form of chorea, with a varied etiology and often involving subcortical structures such as the subthalamic nucleus.
The causes of ballismus may be genetic, as in Huntington's chorea, spinocerebellar ataxia, GLUT-1 deficiency, paroxysmal kinesiogenic choreoathetosis, neuroacanthocytosis, ataxia telangiectasia, or Lesch-Nyhan syndrome; metabolic, as in hyperthyroidism, hyponatremia, hypernatremia, hepatic/renal failure or mercury poisoning; and, structural, as in stroke, brain tumors, extrapontine myelinolysis, or post-shunt chorea.
Sydenham's chorea is treated with penicillin prophylaxis up to the age of 21 years to prevent a recurrence, even if the patients lack the signs and symptoms of rheumatic fever. Valproic acid is the first drug of choice. Carbamazepine can also be effective. Dopamine-receptor blocking drugs such as tetrabenazine and antipsychotics are indicated only if other medications fail.,
A tic is a sudden, jerky, involuntary, repetitive, rapid, random, purposeless, highly stereotyped movement. Tics can be differentiated from myoclonus and chorea by the rising discomfort or urge that is relieved by actual movement. The characteristic features include predictability of both the nature of the movement and its onset. It can be triggered by suggestion, demonstration, stress, or excitement, and is suppressed briefly at will. Suppression of the tics in the school is usually followed by a growing inner tension in the child, often resulting in a rebound release of a flurry of tricks. Tics are possibly the most common primary movement disorders in childhood. 5% and 24% of school children have a single transient tic that may last from several weeks to a few months and then disappears spontaneously. Less commonly, the tic persists and becomes associated with other types of tics, either motor or vocal tics, occasionally resulting in Tourette syndrome.
The Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) diagnostic criteria for Tourette syndrome include both motor and one or more vocal tics, not occurring simultaneously, manifesting multiple times a day, almost every day or intermittently throughout a period of more than one year, with their onset before the age of 18 years, and without a direct physiologic effect of a substance or a general medical condition. Motor tics last about 100 milliseconds and affect the face, head, and neck most commonly. They can be suppressed for a short time by voluntary effort, while the patient experiences a progressive feeling of uneasiness. Tics may be increased by excitement, boredom, stress, and fatigue. Tics can be classified as simple motor tics (a single short stereotyped movement or movement fragment, like eye blinking or nose wrinkling), complex motor tics (a more complex or sequential movement involving multiple muscle groups, like touching things or echopraxia), or phonic tics (simple, brief phonations or vocalizations, like sniffing, producing sounds, or verbalization). Tics are often less prominent or even absent in the clinical examination room. A motor tic starts with an abrupt onset, followed by a subsequent movement or posture, which might be slow or prolonged rather than jerky. This type of tic is classified as a dystonic tic. Its supressibility and stereotyped nature are the clinical clues to classifying such movements as a tic.
Most tics are idiopathic; tics are not associated with cerebral palsy. Family studies suggest that chronic motor tics, Tourette syndrome, and obsessive-compulsive disorders are phenotypes of the same major gene that is inherited in an autosomal dominant fashion with sex-influenced expression. Girls are more likely to have the obsessive-compulsive disorder, and boys are more likely to have Tourette syndrome.
Education and reassurance of the parents is important. Treatment of tics is needed only when they cause any functional impairment. Clonidine is considered as the first-line medication. Other drugs that can be used are olanzapine, risperidone and metoclopramide. One important issue is the treatment of tics that are appearing or worsening concomitantly with attention deficit hyperactivity disorder (ADHD). Prior recommendations were to avoid methylphenidate in these children. However, in a multicenter, randomized, double-blind clinical trial, 136 children with ADHD and a chronic tic disorder were randomly administered clonidine alone, methylphenidate alone, a combined treatment, or a placebo for 16 weeks. Compared to the placebo, the actual therapy was effective; the severity of tic improved in all the treatment groups, mainly with combined treatment. Clonidine was more helpful than methylphenidate but was associated with sedation. The current strategy in the treatment of Tourette syndrome is behavior modification therapy.
Myoclonic movements are sudden, brief, shock-like involuntary movements, which are usually positive (caused by muscle contraction), but can sometimes be negative (due to brief loss or inhibition of muscular tone, as in asterixis, which is caused by hepatic encephalopathy or uremic encephalopathy.
Myoclonus can be described and classified in several ways. The distribution of myoclonus can be focal, multifocal, segmental or generalized. Etiologically, myoclonus can be subdivided into physiological myoclonus (for example, hypnic jerks), essential myoclonus (idiopathic or hereditary), epileptic myoclonus, or symptomatic myoclonus in cases where the myoclonus is secondary to an underlying disorder. Physiologically, myoclonus is subdivided into cortical, subcortical, spinal and peripheral types. In addition, careful assessment of the specific moments of occurrence for myoclonus is important. Myoclonus can occur spontaneously (at rest), but is also often present—and usually worsened—during movement (action myoclonus), or can be provoked by external tactile or acoustic stimuli (reflex myoclonus).
Myoclonus may originate in the spinal cord (spinal myoclonus), brain stem (brain stem myoclonus), or cerebral cortex (cortical myoclonus). Much less frequently, myoclonus may begin in the peripheral nervous system. Cortical myoclonus may occur spontaneously, with an action, or with somatosensory stimulation. Post-anoxic myoclonus is usually cortical in origin and is usually action induced, without the presence of a sensory stimuli. Action myoclonus occurs during an intentional movement. It is the most disabling variety of myoclonus. Brain stem myoclonus, for example, an exaggerated startle response, is usually generalized and is often triggered by an auditory stimuli. Spinal myoclonus may be segmental, multisegmental, or generalized. Palatal myoclonus is a regular, rhythmic unilateral or bilateral contraction of the soft palate. The contractions occur at 2 to 3 Hz and may persist during sleep. Due to the rhythmicity, it seems more appropriate to call this as palatal tremor. Palatal myoclonus may extend to other muscles, including the ones of the face, tongue, throat, and diaphragm. There are two forms of palatal myoclonus: essential and symptomatic. The essential form is self-limited and mainly occurs in children, in whom a click—synchronous with the myoclonic contraction—can be perceived on auscultation and sometimes even at a distance. Familial cases have been reported. The symptomatic form results from lesions of the brain stem or cerebellum. These cases are usually associated with hypertrophy of the inferior olive.
Although in adults, myoclonus is sometimes a relatively benign sign associated with reversible acquired metabolic dysfunction, in children, it is often more concerning. However, benign forms of myoclonus do occur in children as well. Myoclonus in children can be caused by disease processes that destroy or irritate gray matter, including tumors, metabolic disease, neurodegenerative disease, and acute infectious processes such as encephalitis., It is frequently associated with seizures, delirium or dementia, and other signs of neuronal dysfunction. Epilepsia partialis continua manifests as a unilateral rhythmic myoclonus and is associated with contralateral cortical injury including infection, tumor, and Rasmussen's encephalitis.,
Athetosis is a slow, continuous, involuntary writhing movement that prevents maintenance of a stable posture. Athetosis involves continuous smooth movements that appear random and are not composed of recognizable sub-movements or movement fragments. The meaning of the term “athetosis” in the Greek language is “without position or place,” reflecting the inability of the patient to maintain a stable posture.
In contrast to chorea, athetosis repeatedly affects the same regions of the body. Athetosis may worsen with attempting movements or while maintaining a certain posture, as is seen in dystonia and chorea, but it can also occur at rest. It typically involves the distal extremities (hands or feet) more than the proximal ones, and it can also involve the face, neck, and trunk. Athetosis is distinguished from dystonia by the lack of sustained postures, although it is frequently associated with dystonia, so that establishing the distinction between the two conditions can be difficult in clinical practice. It differs from chorea by the lack of identifiable movement fragments. Although athetotic movements are typically slower and less jerky than the movements in chorea, this is not always the case and the distinction is made more by the nature of the movements rather than by their speed or rhythmicity. Athetosis is distinguished from tremor and stereotypies by the lack of rhythmicity and repeatability, and from myoclonus by the smooth, sinuous, flowing quality to the movements in contrast to the rapid shock-like movements seen in the latter condition.
In children, athetosis rarely occurs in isolation but is much more commonly associated with chorea and dystonia. The combination of chorea and athetosis is called “choreoathetosis”, but choreoathetosis is most often caused by the dyskinetic form of cerebral palsy in which dystonia is a frequently associated movement disorder. Choreoathetosis is also associated with kernicterus and other causes of basal ganglia injury. Most often, athetosis is secondary to lesions in the basal ganglia, and may occur due to cerebral palsy, ischemia, or trauma. It can occur as an isolated movement disorder and is often associated with a normal intellect. Athetoid cerebral palsy begins before the age of 5 years and in 90% of the affected cases, is absent during sleep, and is increased by stress. In one series of 100 patients with athetoid cerebral palsy, other movements, such as chorea or ballism, developed in 45 patients during the later childhood.
Stereotypies are stereotyped, intermittent, rhythmic, repetitive, purposeless movements involving the head and upper body. The key feature of stereotypies is that the movements look the same each time they occur, and remain the same over time. Some examples include hand flapping and rocking. Stereotypies can involve more complex movements including posturing and grimacing. Stereotypies start before the age of three years, and for many children, resolve by early childhood. Some children continue to have stereotypies later in childhood that may continue even into adulthood.
The movement is often but not always rhythmic and may involve fingers, wrists, or more proximal portions of the upper extremity. The lower extremity is typically not involved. Stereotypies can be unilateral or bilateral but are more commonly bilateral. There is probably no premonitory urge, and the movements tend to occur when the child is stressed, excited, distracted or engrossed. Stereotypies can be stopped by distraction or initiation of another activity. They do not usually interfere with the ability to perform tasks, although they can occur during excited play and briefly interrupt the ongoing activity. The stereotypy involves a single movement performed repeatedly, rather than a set of different recognizable movements. Although stereotypies have a clear beginning and ending with intervening periods of more normal movement, the duration of the stereotypy is variable and can continue for many minutes at a time if the child is not distracted by another activity.
Stereotypies do not necessarily hold the child's attention, so that they will often occur while the child is engrossed in another activity. Stereotypies often accompany developmental syndromes including autism spectrum disorders. However, it is important to reassure parents that these movements can occur in the absence of any other neurological findings, and they appear to be common in healthy children throughout the preschool years. Therefore, the presence of stereotypies by themselves does not predict any neurological diagnosis, and their value in predicting the neurological outcome or in narrowing the differential diagnosis in developmental disorders is minimal.
Dystonia is a syndrome of sustained muscle contractions, frequently causing twisting and repetitive movements or abnormal postures. It is slower than myoclonus, and is not random in distribution like chorea. It is rarely rhythmical like tremor, and is not preceded by a premonitory urge like tics.
The new definition of dystonia is that it is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive movements, postures, or both. Dystonic movements are typically patterned, twisting, and may be tremulous. Dystonia is often initiated or worsened by voluntary action and is associated with overflow muscle activation.
Dystonia is characterized by simultaneous contractions of agonist and antagonist muscles. Dystonic movements may be spontaneous or may be triggered or exacerbated by voluntary attempts at carrying out a movement or sustaining a posture, and may be increased by stress, pain, fatigue, and startle. Dystonia typically diminishes or disappears with distraction and sleep. A highly characteristic feature of dystonia is the presence of “sensory tricks” or “geste antagoniste” (proprioceptive or tactile) that ameliorate the dystonic movement, although this may not be seen in all types of dystonias., Dystonia has been associated with injury to the basal ganglia, in particular, the putamen and globus pallidus. In many cases, however, no basal ganglia injury can be identified and recent evidence from both human disease and animal models suggests that lesions in other brain areas including the cerebellum, brain stem, or sensory cortex  can be the cause of dystonia. Corticospinal injury can produce fixed postures similar to that seen in patients with dystonia that may be due to a combination of active contraction and weakness of opposing muscles. It may occur only with a single specific task. An example of this is the 'writer's cramp' where dystonia is only present while writing and does not occur with other activities. An additional example is a musician's dystonia where dystonia is only present while the musicians play their particular instrument.
The International Consensus Committee, consisting of experts, proposed a new classification to help clinicians diagnose and manage these disorders. The classification is based on two axes. Axis I involves clinical features which includes 4 major headings. These include: a. the 'age at onset': The dystonias are divided here into those occurring in infancy (birth to 2 years), childhood (3–12 years), adolescence (13–20 years), early adulthood (21–40 years), and late adulthood (40 years and older); b: 'Body distribution': These include focal (one isolated body region), segmental (two or more contiguous regions), multifocal (two or more noncontiguous regions), hemidystonic (half the body), and generalized (trunk plus two other sites) involvement; c: 'Temporal pattern': This is based on the course of the disease, whether static or progressive. It also dependent on short-term variations, such as, if the dystonia is persistent, action specific, diurnal, or paroxysmal; and, d: 'Associated features': This is based on whether dystonia is an isolated symptom, is associated with tremors or is occurring in combination with other neurological or systemic features.
Axis II consists of etiology which is further analyzed based upon the following subheadings: a. 'Nervous system pathology': This includes degenerative or structural (that is focal static) lesions; and, b: 'Heritability': This is based on whether the dystonia is inherited (that may be sex linked or autosomal, dominant or recessive, or mitochondrial), acquired (that may be associated with brain injury, drugs/toxins, vascular lesions, or a neoplastic pathology), or is either idiopathic, sporadic or familial.
Currently, dyskinetic cerebral palsy is probably the most common cause of dystonia in children, with injury to the basal ganglia, thalamus, brainstem, and cerebellum occurring due to hypoxic-ischemic injury in the prenatal, perinatal, or infantile period. Other causes include encephalitis, vascular diseases, autoimmune disorders, cerebral malformations, metabolic diseases, and neurodegenerative diseases. Primary dystonia in children is mostly genetic. In children, dystonia is frequently accompanied by bradykinesia, perhaps due to a common etiology. Recently, monogenic defects have been identified in dystonia that occurs without any structural lesions. Rarely, dystonia can be life threatening when it becomes extreme in its manifestations. This is called status dystonicus. The severe dystonia can cause muscle breakdown that may lead to kidney failure.
Some other inherited conditions causing movement disorders in children include glutaric aciduria type 1, which usually begins at the age of 5-10 months. The usual clinical presentation includes acute encephalopathy followed by dystonia, motor impairment, and macrocephaly. The computed tomography (CT)/magnetic resonance imaging (MRI) shows a frontotemporal brain atrophy and the laboratory investigations include assessment of organic acids in urine as well as an enzymatic assay.
Glucose transporter 1 (GLUT 1) deficiency syndrome is seen in infancy. The clinical manifestations include seizures, a developmental delay, and a complex movement disorder. Abnormal electroencephalographic (EEG) findings improve after the ingestion of food. The cerebrospinal fluid (CSF) examination shows a low glucose concentration.
Lesch Nyhan syndrome occurs at the age of 3-18 months. Clinical features include self-mutilation, facial grimacing, involuntary writhing, and repetitive movements of the arms. Non-neurological manifestations include kidney stones and hyperuricemia.
Pantothenate kinase-associated neurodegeneration (PKAN) is commonly seen in Indian Aggarwal families. The age of onset is the first decade. Clinical features include delayed motor and language milestones, later leading to the development of choreoathetosis, dystonia, dysarthria, dysphasia, spasticity, retinopathy. MRI reveals the classical 'eye of the tiger' sign.
Leigh's disease begins at birth or during the first year. Its clinical features include diffuse encephalopathy, dysphagia, dystonia, myoclonus, hypotonia, and central respiratory insufficiency. MRI shows periventricular leukomalacia as well as hyperintense T2 signals in the basal ganglia and thalami. High serum/CSF lactate can be detected.
Wilson's disease begins in the 1st and 2nd decade. The clinical features include dysarthria, gait disturbances, risus sardonicus smile, dystonia, rigidity, tremor, and dysphagia. MRI reveals a high signal in the basal ganglia, dentate nuclei and cerebellum on T2 weighted imaging. Kaiser Fleischer ring can be seen on slit lamp examination, and a low serum ceruloplasmin level is detected. Early diagnosis helps in the prevention of irreversible neurologic complications. [Table 4] summarizes the clinical phenotype of the hyperkinetic movement disorders and their anatomical correlation and [Table 5] illustrates its treatment options.
Hypokinetic disorders in children
Hypokinetic disorders are uncommon in children. They are well described and studied in adults. Parkinsonism is most described entity in this group in children.
Parkinsonism in children
All the key motor features (bradykinesia, rigidity, rest tremor and postural instability) of idiopathic Parkinson disease can be present in children also.
Pure Parkinsonism is seen less often in children, and most patients have other movement disorders, commonly dystonia (dystonia-parkinsonism) but also chorea and myoclonus. [Table 6] illustrates the various etiological factors responsible for manifestations of parkinsonism in children.,,,,,,,,,,,
Other causes of genetic parkinsonism in children:
Lysosomal storage disorders
Disorders of brain metal ion accumulation
Suggested work up: Serum manganese level and MRI brain.
Suggested work up: Slit lamp examination for detection of Kaiser Fleischer ring and sun-flower cataract, serum copper and ceruloplasmin assessment, 24 hour urinary copper estimation, MRI brain (giant panda sign).
Other hereditary/degenerative causes
B. METABOLIC CAUSES OF PARKINSONISM
C. STRUCTURAL CAUSES
D. INFECTIOUS/PARAINFECTIOUS DISORDERS,
E. DRUGS/TOXINS, 
F. DISORDERS THAT MIMIC PARKINSONISM
Diagnosis of hypokinetic disorders in children
The diagnosis of hypokinetic disorders in children is mainly based on a detailed clinical history, including the family history, and neurological examination. Attempt should be made to identify the other associated hyperkinetic features, which help in narrowing the differential diagnosis. In case hereditary and genetic parkinsonism disorders are suspected, the testing required is mentioned in [Table 6]. For detection of metabolic causes, serum biochemistry for the suspected molecule is advised. MRI of the brain helps in exclusion of structural pathology. MRI brain is also helpful in diagnosing brain metal ion accumulation.
In addition to the above mentioned tests, a detail history related to the drug or toxin exposure is also important, as timely interventions can reverse the disease process completely in a majority of these cases.
Treatment of parkinsonism in children
In every pediatric patient with parkinsonian features, a trial of levodopa is recommended., Among the classical motor features, bradykinesia is the primary symptom that is usually responsive to treatment in childhood parkinsonism. The treatment is started with a single dose of levodopa 1mg/kg in the morning, and the occurrence of side effects such nausea and postural hypotension are assessed. If this dose is well-tolerated for 3 to 4 days, then it can be increased to three times per day for gaining an adequate therapeutic response. The dosage can be increased up to a maximum of 10 to 15 mg/kg/day divided into three doses. The medication dosage must be adjusted subsequently as the child grows, to obtain an optimal response.
In pediatric parkinsonism, long-term treatment with levodopa will eventually lead to dyskinesias and freezing episodes that can limit its use. To avoid this, some authors use dopamine sparing strategies, which involve the early use of dopamine agonists or of dopamine breakdown inhibitors. However, data for this approach is lacking in children.
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Conflicts of interest
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]