Movement disorders are a fascinating, heterogeneous group of neurologic conditions characterized by either an excess of movement (hyperkinetic movement disorders), a paucity of movement (hypokinetic movement disorders), or impaired control of motor functions (eg, cerebellar ataxia). Worthy of emphasis is the fact that, as with all clinical syndromes in medicine, both a thorough history, including pertinent positive and negative findings, and a careful examination are fundamental in establishing the correct diagnosis. On examination, movement disorders are diagnosed by first visually identifying the type of movement based on its characteristics (eg, tremor); this is called the phenomenology of the movement. A differential can then be generated based on history and examination findings. Appropriate neuroimaging and laboratory studies may also be helpful in establishing a diagnosis.
Hyperkinetic movement disorders include tics, tremor, chorea, dystonia, myoclonus, and stereotypy, all of which can be manifestations of various clinical syndromes. Hypokinetic movement disorders are much less common in children; the archetypal hypokinetic movement disorder is parkinsonism, of which the most common etiology in adults is Parkinson disease. Spasticity, a velocity-dependent increase in muscle tone, is, strictly speaking, not a movement disorder, although it can be present in patients who also have movement disorders (eg, patients with cerebral palsy) and can impair gait and motor control. The word dyskinesia, which simply means “abnormal movement,” is in and of itself not specific, and standing alone, it is not a particularly useful descriptor when identifying involuntary movements. However, when placed in context, it can convey the constellation of symptoms seen in distinct clinical syndromes (as in the case of paroxysmal kinesigenic dyskinesia or levodopa-induced dyskinesia).
When taking a history of movement disorders, it can be very helpful to ask the patient (or, more frequently, the parents) about the onset of symptoms in this way: “When was the very first time in your life that you ever experienced any abnormal movements?”
This chapter will address pertinent clinical entities in order to equip the pediatrician with tools to classify and evaluate them. Of course, any movement disorder that is associated with rapid progression, significant functional impairment, or cognitive decline necessitates prompt referral to a child neurologist, ideally to a pediatric movement disorders specialist, or, if the situation warrants, to the emergency department. Tics and stereotypy may not require referral, should the practitioner be confident of these diagnoses; in most other cases of involuntary movements (tremor, chorea, dystonia, myoclonus, parkinsonism), referral is often warranted.
HYPERKINETIC MOVEMENT DISORDERS
Tics and Tourette Syndrome
Tics are sudden, brief, intermittent, recognizable, repetitive movements or vocalizations that are almost always suppressible for short periods and are usually associated with a preceding urge to perform the movement or vocalization. Patients often describe this premonitory urge phenomenon as an unpleasant, often difficult-to-describe sensation that builds and then is resolved by the action for a period of time, then builds again. It may feel similar to “an itch that needs to be scratched” or “the feeling that makes you want to sneeze.” This sensation can be either generalized (felt “all over” or in an ill-defined location) or can be localized to a particular body part. Grade school–age children or patients with cognitive impairments may not be able to identify the presence of a premonitory urge. Children with tics should not be encouraged to attempt to suppress them, as doing so can cause considerable discomfort.
Tics typically begin in children between the ages of 4 and 7, in a rostrocaudal fashion; that is, they most often begin in the face or neck, and may later involve movements of the limbs or trunk. Individual tics have very little variability between repetitions. Complex tics can evolve over time but are unlikely without preceding simple tics. Tics can be divided into motor tics and phonic or vocal tics (sounds). Common tics include excessive blinking, facial grimacing, shoulder shrugging, sniffing, or grunting. Prior to evaluation by a neurologist, it is not unusual for children to have been referred to other specialties for evaluation of symptoms such as repetitive sniffing or coughing that have been refractory to allergy medications. Profane gestures (copropraxia) or utterances (coprolalia) may also be present but occur in fewer than 10% of patients with persistent tics.
When at least 1 year has passed since the onset of the first tic and the patient has experienced at least 1 phonic tic and at least 2 motor tics, criteria have been met for the diagnosis of Tourette syndrome. Prior to reaching 1 year, a patient with tics meets criteria for provisional tic disorder (previously called transient tic disorder) and may eventually go on to meet criteria for Tourette syndrome. Should a patient have tics for at least 1 year that do not meet criteria for Tourette syndrome, he or she meets criteria for the diagnosis of persistent tic disorder (formerly chronic tic disorder).
The words “Tourette syndrome” can be disconcerting to parents, and the diagnosis must be delivered in a sensitive and compassionate way. It is important to stress that there is nothing more dangerous or frightening about a Tourette syndrome diagnosis compared to the other diagnoses. Rather, the utility of the Tourette syndrome diagnosis lies in the fact that the child now fits into a category in which the tics can be expected to persist and wax and wane and change over time.
Tourette syndrome is thought to have a prevalence between 0.3% and 1% of the pediatric population and is more common in males than females, at a ratio of 4 to 1. For many patients, symptoms are most bothersome around 10 to 12 years of age. It is important not to suggest with certainty to patients or their parents that these symptoms will decrease or resolve with time. Rather, it is more helpful to state that during the years following adolescence, in many patients, symptoms will decrease in severity, and in some patients, they may resolve or nearly resolve. However, some patients will continue to have similar symptoms into adulthood. Rarely, symptoms may worsen in adulthood.
Tourette syndrome is a hereditary neurologic condition, although the responsible gene or genes have not yet been identified in most cases. Neurobehavioral comorbidities, which often occur in patients with tics and in their family members, include obsessive-compulsive behaviors or obsessive-compulsive disorder (OCD), as well as attention-deficit/hyperactivity disorder (ADHD). ADHD is thought to occur in 40% to 70% of patients with Tourette syndrome and OCD is reported in 20% to 60% of cases. The patient’s medical history must be carefully explored for these symptoms, particularly in the case of obsessive-compulsive behaviors, as patients and parents may not have recognized them as such. Should these comorbidities impair a child’s function, treatment with serotonin-modulating medications for OCD and stimulants for ADHD is warranted, and combinations of these medications often are needed.
It is advisable to inform patients and their parents that many generally safe and well-tolerated treatments are available that can be very effective in the management of tics and often can enormously improve quality of life. Efficacious medical treatments include α2-agonists (clonidine, guanfacine), anticonvulsants (topiramate), dopamine receptor–blocking agents (eg, fluphenazine), and dopamine-depleting agents (tetrabenazine). There is evidence to suggest that in a patient with a single bothersome tic, who has the cognitive capacity and drive to participate in therapy, habit-reversal techniques (HRTs), such as cognitive-behavioral intervention for tics (CBIT), can be helpful. (Of note, these interventions are performed by practitioners trained in HRT and are distinct from cognitive-behavioral therapy, or CBT.) Botulinum toxin injections by a movement disorders specialist, when needed, can also be an effective intervention for tics. In refractory cases, deep brain stimulation of the globus pallidus internus may provide improved symptom control.
The need for treatment in tic disorders rests solely on the degree to which the patient (ie, not the parents or others) is bothered or impaired by the movements and vocalizations. Even very young children are typically able to state whether the movements bother them and whether they want them to go away. If that is the case, it is useful to discover which movements are bothersome and the ways in which they are, so as to tailor therapies appropriately. To this end, helpful questions to ask the patient include the following:
Do any of these movements or sounds cause pain or discomfort?
Do any of them interrupt tasks or get in your way?
Do any of them make you feel self-conscious or embarrass you?
An answer in the affirmative to any of these questions signifies that treatment is warranted. It is important to be clear with the patient and parents that the goal of treatment is not to make the movements resolve, but rather to improve them to a degree to which the above questions are all answered in the negative.
Dystonia is a type of involuntary movement characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both. Dystonic movements are typically patterned and twisting, may be associated with tremor, and can be initiated or worsened by voluntary action. The phenomenon of overflow may be seen, in which there is a close association of an unwanted movement with an intended movement or spread of the involuntary movement to surrounding or distant muscles. Mirror movement is another phenomenon sometimes seen associated with dystonia, in which voluntary movements of 1 limb (eg, hand movements while writing) may provoke involuntary movements in the opposite limb.
The most common category of dystonia seen is secondary dystonia that is symptomatic of some type of brain insult, often a perinatal hypoxic-ischemic injury. Dystonia can also occur as part of the constellation of symptoms seen in numerous genetic and neurometabolic disorders, or as the result of factors such as infection, trauma, or toxic exposure. The dystonia in these circumstances usually is generalized and is often not present in isolation; rather, it is part of a larger clinical picture in which other neurologic manifestations, such as intellectual disability, microcephaly, dysmorphic facial features, or spasticity, may also be present.
Less frequently, dystonia in children may be an isolated dystonia. Isolated dystonias are genetic dystonias with characteristic phenotypes, in which dystonia is the only sign of the disease or is associated with other specific findings (typically other involuntary movements). Most isolated dystonias presenting in childhood have onset of dystonia in 1 limb, which then generalizes.
Workup for dystonia should be directed by information from the history (including family history and birth history) and examination, and will nearly always include magnetic resonance imaging of the brain. All children with dystonia should undergo a trial of therapy with carbidopa-levodopa. Other oral medications that may be helpful for dystonia include clonazepam, trihexyphenidyl, and baclofen. Botulinum toxin injections are the treatment of choice for focal dystonia. Other treatment modalities include intrathecal baclofen pump implantation and pallidal deep brain stimulation.
Infants and young children with gastroesophageal reflux may demonstrate dystonic posturing of the neck or trunk, known as Sandifer syndrome. The postures typically are intermittent and may alternate direction, often (but not always) have a temporal relationship to feeds, and may be associated with other stigmata of reflux including irritability, crying, and regurgitation. Postures may include torticollis (lateral head rotation), laterocollis (lateral neck flexion), retrocollis (posterior-ward movement of the head), opisthotonos (back arching), and others. Symptoms improve with treatment of the underlying reflux.
Tremor is an involuntary, rhythmic oscillatory movement about a joint axis. Tremor can be described by the situations during which it occurs: it can occur at rest (rest tremor), while maintaining a posture against gravity while still (postural tremor), or with volitional movement (kinetic tremor), or can worsen as the target is approached (intention tremor). Postural and kinetic tremor often accompany one another, and together, they are called action tremor. Tremor can involve the limbs, trunk, head, voice, jaw, facial muscles, or tongue. Action tremor is far more common than rest tremor in children.
Tremor occurs less commonly in children than in adults but is still seen not infrequently in a pediatric movement disorders clinic. Tremor in children may be related to medications or may be due to conditions such as essential tremor, dystonic tremor, hyperthyroidism, as part of a cerebellar syndrome (eg, the spinocerebellar ataxias, ataxia-telangiectasia, ataxia with vitamin E deficiency), associated with other genetic/metabolic syndromes (eg, Wilson disease, neurodegeneration with brain iron accumulation), or in psychogenic movement disorder. Common medications associated with tremor include direct or indirect adrenergic agonists (ADHD medications, asthma medications), corticosteroids and other immunosuppressive agents, antiepileptic medications, antiarrhythmics (amiodarone), antidepressants, and lithium. Because not all children exposed to these medications have tremor, their symptoms may reflect an underlying tendency toward having tremor, and family history should be examined.
Essential tremor is characterized by postural and kinetic tremor, most often of the bilateral upper extremities, and has been estimated to affect approximately 5% of adults age 65 or older. The tremor classically improves with consumption of alcoholic beverages. Few objective prevalence data exist for the pediatric population, although a significant portion of adults with essential tremor recall onset in childhood or adolescence. As it is an autosomal dominant, highly penetrant condition, an accurate family history will assist in making the diagnosis. Onset of childhood essential tremor usually develops in the second decade, but can it present as early as the first few years of life. Essential tremor often responds to treatment with propranolol or primidone.
Thyroid function testing (thyroid-stimulating hormone and free thyroxine) is often appropriate for children who present with action tremor. In adolescents, it may be useful to check a serum ceruloplasmin for the less likely possibility of Wilson disease.
Dystonic tremor is tremor associated with dystonia. It tends to be more irregular than essential tremor and classically has a positional component; that is to say, it may worsen in some positions and improve in others.
Chorea, Athetosis, and Ballismus
Chorea is a random-appearing sequence of irregular, involuntary writhing or wiggling movements that flow from 1 part of the body to another. Findings on examination that support chorea include milkmaid’s grip (an irregular milking-like movement of the patient’s fingers when asked to squeeze the examiner’s fingers) and motor impersistence of the tongue (difficulty maintaining the tongue in a protruded position). Choreiform movements should be impossible to predict, in contrast to other repetitive, patterned involuntary movements such as tics or stereotypy. These movements can be subtle, but on close examination, it may appear that the affected child is never quite still. Diagnosis of chorea of unclear etiology should prompt referral to a child neurologist or pediatric movement disorders specialist without delay.
Small-amplitude, distal chorea is sometimes referred to as athetosis, and proximal combined with distal chorea is referred to as choreoathetosis. (In point of fact, it is likely more useful to call it chorea and to describe the affected body parts.) Ballismus is a proximal, large-amplitude choreiform movement that causes flinging of a limb or limbs.
Among the most common causes of chorea in children is Sydenham chorea, one of the major criteria for the diagnosis of acute rheumatic fever. Sydenham chorea represents one of very few circumstances in which a presumptive diagnosis of rheumatic fever can be made without strict adherence to the Jones criteria. Sydenham chorea usually affects children from 5 to 15 years of age and is associated with preceding symptomatic or subclinical infections weeks to months after a group A β-hemolytic streptococcal infection. Screening for other features of rheumatic fever, in particular carditis, is appropriate. The chorea may be accompanied by obsessive-compulsive behaviors or impulsivity.
Particularly in the newly symptomatic, typically developing child with no family history of involuntary movements, the index of suspicion for Sydenham chorea must be high. Laboratory evaluation should include testing for evidence of recent streptococcal infection such as elevated antistreptolysin O and anti-DNaseB titers, although as many as 25% of patients may be seronegative. Therefore, even in the absence of serologic evidence, should no other etiology be apparent, initiation of long-term treatment with penicillin is often appropriate. Treatment should include elimination of the underlying infection (typically with oral or intravenous penicillin) and prophylaxis to prevent recurrent rheumatic fever (with intramuscular or oral penicillin), typically for 5 years or until age 21 (or longer if there is evidence of other organ involvement).
Chorea usually resolves spontaneously over a period of several months to a year, and in some cases, it may recur. Should the chorea impair the child’s function, symptomatic treatments, such as scheduled oral clonazepam, may be helpful.
Other Chorea in Childhood
Other causes of chorea in the pediatric population include other autoimmune disorders (antiphospholipid syndrome, systemic lupus erythematosus, anti–N-methyl-D-aspartate [NMDA] receptor encephalitis), chorea related to hypoxic-ischemic or infectious insults to the basal ganglia, postpump chorea (following cardiopulmonary bypass), and heritable genetic disorders (as can be seen in association with pathogenic variants of NKX2-1, ADCY5, and MICU1 genes).
Patients with chorea may benefit from symptomatic management using benzodiazepines (eg, clonazepam), dopamine receptor–blocking medications (eg, fluphenazine), or dopamine-depleting medications (eg, tetrabenazine). Practitioners must remain mindful that dopamine receptor–blocking medications may cause tardive dyskinesia.
Myoclonus is a brief, jerk-like or shock-like contraction or relaxation of a muscle or muscle groups that results in a sudden movement. Myoclonus originates in the central nervous system; most simply, the point of origin can be divided into the cerebral cortex, the brain stem, or the spinal cord. Myoclonus may be physiologic, as in singultus (hiccups), hypnic jerks (myoclonus that may happen to you while starting to fall asleep in lecture), or benign neonatal sleep myoclonus (physiologic myoclonic jerks commonly seen in neonates). Less benign are the myoclonic epilepsies, which typically present in childhood, of which myoclonus is a prominent feature. Therefore, workup of myoclonus often includes electroencephalography (ideally performed at a tertiary-care pediatric institution) to determine whether it is epileptic or nonepileptic.
Children are more likely than adults to have cerebral malformations or genetic disorders that result in myoclonus. Examples of disorders in which myoclonus can present include lysosomal storage disorders (eg, neuronal ceroid lipofuscinosis, Niemann-Pick type C, Krabbe disease), mitochondrial disorders (eg, MELAS [mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes], MERFF [myoclonic epilepsy with ragged red fibers], Leigh syndrome), and disorders with prominent ataxia (eg, Friedreich ataxia, ataxia-telangiectasia, some autosomal dominant spinocerebellar ataxias, dentatorubral-pallidoluysian atrophy), as well as in the setting of metabolic derangement, drug exposure (eg, propofol), or central nervous system infection.
Opsoclonus-myoclonus-ataxia syndrome (OMA) is an autoimmune clinical entity principally affecting young children that can include any or all of the symptoms included in its name. Ataxia is the symptom most commonly seen; suspicion should be raised in an otherwise healthy patient who develops acute or subacute cerebellar ataxia that does not begin to resolve within days or appears to worsen over time, particularly if it is associated with opsoclonus (random-appearing eye movements) or myoclonus. Vigilance for this disorder is paramount, as it can occur as a paraneoplastic syndrome in the setting of neuroblastoma. Treatment of myoclonus often includes benzodiazepines and antiepileptic medications.
Stereotypies are repetitive, often continual, rhythmic movements that can be voluntarily suppressed. These movements often occur more when excited or nervous or while engrossed in tasks and stop with distraction or redirection. Most often, they are benign, often soothing or pleasant, and are more common in children with developmental differences, although they also occur in normally developing children. Typical stereotypies include limb movements (eg, flapping, twirling, marching) or trunk movements (eg, rocking). Interventions are usually not warranted for stereotypy, unless there is evidence of self-injury.
Useful questions to ask oneself in making the diagnosis of stereotypy include the following:
Are they sustained, rhythmic, continual movements? Many, although not all, stereotypies are rhythmic and continual. One thing they should be is predictable—while a child may have numerous different stereotypies, each should be relatively the same between 1 event and the next. The movements should be patterned; looking at them, one could predict the way the child will next move or continue to move (eg, making circular motions with the feet).
Does the child like them? Bright children as young as 4 or 5 years of age may be capable of answering this question if asked properly (eg, “Do these feel good, or do they feel bad?” or “Do you like these?”). If a young child clearly states that they are uncomfortable, then these may not represent stereotypies. Older children and adolescents may dislike the movements due to feeling self-conscious about performing them, but viscerally, they should still feel good to them.
Aside from stereotypies that cause self-injury, a phenomenon more common among children with significant cognitive impairments, stereotypies tend to be benign. The most common stereotypy among adults is leg stereotypy disorder, which most frequently manifests as benign, rhythmic, continual heel-tapping movements, which may be more frequent during periods of boredom or concentration. It may be helpful to point out to parents that stereotypies are most often harmless movements.
Infantile Gratification Phenomenon
Infantile gratification phenomenon, also called self-stimulatory behavior of infancy, is a very common type of stereotypy seen in typically developing infants and young children, most often girls, consisting of indirect stimulation of the genitalia. Movements typically include stereotyped posturing of the lower extremities (often leg-crossing) with pressure to the pelvic area, lasting from minutes to hours, and may be associated with rocking, grunting, diaphoresis, or facial flushing. These movements stop with distraction or redirection, as with other stereotypies. Although they are benign, they can be very alarming and odd-appearing to caregivers; parents can often be reassured by describing them as self-soothing behaviors, akin to thumb-sucking.
HYPOKINETIC MOVEMENT DISORDERS (PARKINSONISM)
Parkinsonism is a clinical syndrome characterized by various combinations of rest tremor, bradykinesia (slowness and reduced amplitude of movement), rigidity, and postural instability (loss of postural reflexes; ie, a tendency to lose one’s balance). Patients with parkinsonism typically exhibit a paucity of movement and may demonstrate a decreased blink rate, masked facies (hypomimia), or a sudden and unpredictable inability to initiate movement (freezing).
In children, parkinsonism is uncommon but can be postencephalitic parkinsonism, drug-induced parkinsonism, or parkinsonism associated with an underlying genetic/metabolic disorder (juvenile Huntington disease, rapid-onset dystonia-parkinsonism, and numerous others). A detailed history, including family history of involuntary movements, is essential. Evaluation for parkinsonism in the pediatric population may include neuroimaging and genetic testing such as whole-exome sequencing or Huntington disease trinucleotide repeat expansion polymerase chain reaction. Carbidopa-levodopa may be helpful in the treatment of parkinsonism.
OTHER INVOLUNTARY MOVEMENTS IN CHILDHOOD
Shuddering attacks are repeated bursts of axial shuddering without impaired awareness or consciousness that may occur occasionally or up to 100 times per day. Onset of each event is sudden, and it typically lasts 1 to 2 seconds.
Shuddering attacks are considered a benign movement disorder, with onset in infancy or early childhood, in the context of typical cognitive and motor development. Over time, the frequency and severity of the spells usually decrease and eventually resolve spontaneously.
Spasmus nutans (Latin, “nodding spasm”) is a condition defined by a clinical triad of torticollis (neck-twisting), head titubation (rhythmic bobbing), and rapid, asymmetric, low-amplitude nystagmus. The titubation may occur intermittently (hence, “spasm”), is small in amplitude, can be horizontal or vertical, and may be a compensatory mechanism for the nystagmus. Spasmus nutans is generally a benign, self-limited condition that resolves during childhood, although there may be some residual strabismus, amblyopia, and mild refractive errors. Of note, as optic nerve glioma can present similarly, referral for neuro-ophthalmologic and/or neurologic evaluation is appropriate.
Anti-NMDA Receptor Encephalitis
Anti-NMDA receptor encephalitis, an autoimmune neurologic disorder first described in 2005, is primarily a disorder of children, adolescents, and young adults and can often present with involuntary movements such as chorea, dystonia, and stereotypy. Involuntary movements in this syndrome are typically associated with other neurologic and psychiatric features, which can include encephalopathy, seizures, and psychosis, all of which typically present over a period of days to weeks. Involuntary movements of the mouth are a classic feature of this disorder and can be a clue to the diagnosis (see also Chapter 548).
Because there is evidence to suggest that prompt recognition and treatment of this disorder with immunomodulation may improve outcomes, mindfulness of this syndrome is crucial. Management of progressive symptoms often requires intensive care unit admission. Suspicion for this disorder should prompt swift evaluation, ideally in a tertiary-care emergency center. Evaluation should include serum and cerebrospinal fluid anti-NMDA receptor antibody titers. As in some (typically teen or adult) patients, anti-NMDA receptor encephalitis can occur in the setting of ovarian teratoma, and gonadal ultrasound is appropriate. In cases of severe dystonia or chorea, creatine kinase (CK) levels should be followed closely to prevent rhabdomyolysis and acute kidney injury.
Treatment for anti-NMDA receptor encephalitis includes symptomatic therapy to minimize involuntary movements and seizures. Immunomodulation with therapies such as intravenous methylprednisolone, intravenous immunoglobulin, plasmapheresis, rituximab, and cyclophosphamide used in an appropriate clinical management algorithm may improve symptoms and minimize relapses. Clinical improvement may take months, but ultimately, many patients return to a level of function close to their premorbid state, although residual neurocognitive deficits are common.
Psychogenic Movement Disorder
Psychogenic movement disorder (sometimes called functional movement disorder) is a clinical syndrome in which an affected patient generates abnormal movements that are perceived as involuntary by the patient but are the result of an underlying psychological etiology rather than an organic one. Most patients with this condition have conversion disorder, a type of somatoform disorder in which psychological stressors unconsciously produce neurologic complaints. The typical age of onset is in the preteen or teenage years, with a female predominance, and caution should be exercised in making this diagnosis in younger patients. Patients can present with any of a variety of types of abnormal movements, often more than 1, with tremor being most common. Psychogenic movement disorder often presents with an acute onset with rapid progression to maximum severity, and movements often occur in spells, with periods of normalcy between. Characteristic findings are typically seen on examination, including variability, distractibility, entrainment, and suggestibility.
This condition should be treated with a candid discussion of the diagnosis with the patient, followed by psychotherapy with an experienced provider, sometimes supplemented by occupational or physical therapy. Patients are often, but not always, able to make a full recovery.
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