Movement Disorders in Childhood

Movement Disorders

Movement disorders are a group of disorders where there is excessive movement or a paucity of voluntary movement ( Table 40.1 ). The problem is not primarily due to weakness or abnormality of tone (spasticity). This group of disorders is characterized by difficulty initiating movement, abnormal control of voluntary movement, abnormalities of posture, or the presence of unwanted involuntary movements. Primary movement disorders imply a dysfunction in the basal ganglia and its connections or dysfunction of the cerebellum and its connections.

Movements disorders in general can be divided into two main categories. There may be a paucity of normal voluntary movements ( hypokinetic ) or the presence of abnormal involuntary movements ( hyperkinetic ). The hyperkinetic movement disorders include dystonia, ataxia, tremor, chorea, athetosis, ballismus, tics, and myoclonus. In the hypokinetic disorders there is a paucity or decreased amplitude of normal voluntary movements (hypokinesia), slow voluntary movements or difficulty initiating voluntary movement (bradykinesia), or loss of movement (akinesia). One example of a hypokinetic movement disorder is parkinsonism (resting tremor, slow voluntary movements, rigidity).

Chief Complaint

The presenting symptom or chief complaint in a child with a movement disorder may be any of the following:

• Inability to sit still

• Gait abnormality

• Twitching

• “Weakness” or dropping things

• Shaking/trembling of the hands

• Unsteadiness

• Abnormal movements

The goal of the history and examination is to confirm the presence of the abnormal movement and correctly characterize it. Phenomenology is the study or observation of the abnormality. The clinical evaluation of movement disorders emphasizes the question “What type of abnormal movement is present?” or “What is the phenomenology?” rather than “Where is the lesion in the neurologic axis?” Phenomenology is determined by clinical examination, observation, and, when necessary, videotape review. Videotape review is especially useful when a paroxysmal movement is not witnessed during the clinic visit. Phenomenology links directly to potential differential diagnosis as well as choice of symptomatic therapy.

History

The clinical history in the child with a suspected movement disorder should include the course of the problem, whether acute or chronic. Specific information on whether the movements are paroxysmal (episodic) should be obtained. If the abnormal movements are paroxysmal, the history should indicate whether the abnormal movements are task specific (e.g., writer’s cramp, which is a task-specific focal dystonia) and whether there are specific triggers that provoke the abnormal movements. Initiation of sudden movement that triggers dystonia is the hallmark of paroxysmal kinesigenic dystonia or dyskinesia ( Table 40.2 ). Anticipation, emotional change, and stress can increase the frequency of tics. Excitement and emotional distress tend to bring out stereotypies. In general, abnormal movements do not awaken a child from sleep. Most movement disorders disappear in deep sleep except for ballismus and severe torsion dystonia. An abnormal movement that awakens a child from sleep should raise the suspicion for seizures.

The history should clarify the areas of the body affected, severity, and degree of functional impairment. Associated neurologic symptoms such as weakness, visual disturbance, seizures, and mental status changes imply a more widespread neurologic process than that primarily affecting the basal ganglia. Symptoms such as fever, rash, and pharyngitis suggest the presence of systemic illness.

The impact of the abnormal movement on the child’s day-to-day function as well as limitations of function should be documented.

A detailed academic, behavioral, and psychiatric history should be obtained as movement disorders are often accompanied by behavioral, emotional, cognitive, and psychiatric comorbidities.

The history should include medications that have been recently started or stopped as well as chronic medications.

The child’s birth and developmental history clarify whether the movement disorder occurred in a child who had no preceding neurologic conditions or in a child who had prior neurologic/developmental difficulty. The age of onset may provide a clue to the diagnosis ( Fig. 40.2 and Table 40.3 ).

Family history of similar symptoms or a variation of the same type of problem suggests a genetically inherited disorder.

Physical Examination

The general physical examination should determine the presence of systemic signs.

The comprehensive neurologic examination determines whether there are other neurologic abnormalities besides involuntary movements. The mental status examination should include observations about alertness, attention, behavior, mood, and emotions. Cranial nerve examination should specifically determine whether there is nystagmus, limitation of eye movements, or weakness of the face, tongue, and jaw muscles. In general, the motor exam portion of the neurologic examination tends to emphasize muscle tone, strength, and the muscle stretch reflexes (deep tendon reflexes). This portion of the motor exam is effective in identifying the presence of weakness, spasticity, or hypotonia. Some features of involuntary movements such as the inability to maintain a voluntary contraction may be detected during the general motor examination. The template of the motor examination that starts with muscle tone, then goes on to testing of strength, and ends with reflex testing is useful for localization but insufficient for characterization of abnormal movements. Although it is assumed that general observation of the patient occurs throughout the visit, this alone is often insufficient for accurate characterization of the movement disorder. Therefore, once the motor exam that assesses tone, strength, and reflexes is completed, an additional portion of time should be allocated specifically for the observation of the involuntary movements to categorize them (phenomenology).

Posture and abnormal movements should be observed while the patient is in the recumbent position, in the seated position, standing upright with arms by the side, and then standing with arms and fingers outstretched. The child’s ability to maintain a voluntary posture or voluntary muscle contraction should be assessed. This includes the ability to maintain grip while holding the examiner’s hands and the ability to maintain tongue protrusion. Observation of tasks such as picking up, grasping, playing with small toys, pouring water from glass to glass, and writing is useful in the characterization of involuntary movements affecting the upper extremities, trunk, and neck. Stance, gait, swivel, running, stooping, and recovering should be assessed. Observation of speech is important as abnormal movements of the tongue, palate, lower face, and jaw affect the quality of speech. Abnormal movements of the laryngeal muscles affect voice production and quality. Motor impersistence and parakinesia (described in the section on chorea) should be recognized and identified when present. Paroxysmal movements such as tics may be briefly suppressible during a voluntary motor task, only to emerge once the task is accomplished. Tics when mild may not be witnessed in the clinic. Paroxysmal kinesigenic dystonia is often provoked by getting up from the seated position or at the beginning of a short sprint (see Table 40.2 ). Paroxysmal movements that occur between periods of normalcy may not be witnessed during the examination. When a paroxysmal movement is not witnessed in the clinic, videotape review is often helpful.

The gait examination is an essential component of the neurologic examination in a child with a movement disorder. The various gait abnormalities linked to the different movement disorders are listed in Table 40.4 .

Dystonia

Dystonia is defined as a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both. Dystonia is often initiated or worsened by voluntary action and associated with overflow muscle activation.

Dystonia can affect any part of the body. Terms used to describe the distribution of dystonia include focal, segmental, multifocal, and generalized. Focal dystonia affects a single body part. Examples of focal dystonia include blepharospasm (involuntary spasms of the eyelids), torticollis (dystonia of the neck muscles), and writer’s cramp (dystonia of the hand). Dystonia that affects two contiguous body parts is referred to as segmental dystonia (e.g., neck and arm or face and arm). Dystonia of two noncontiguous body parts is referred to as multifocal dystonia. Dystonia on one side of the body (e.g., left leg and left arm) is described as hemidystonia. Dystonia of more than one limb with involvement of the trunk is termed generalized dystonia. Dystonia may affect the larynx in isolation as a focal dystonia or as part of a more generalized dystonia giving rise to a “strangled,” “whispery,” or “breathy” quality of voice production. The distribution of dystonia may be sometimes helpful in localization. For example, acute hemidystonia may be due to pathology in the contralateral basal ganglia. The documentation of the distribution of dystonia also helps in the clinical detection of progression of disease over time.

The clinical evaluation of a patient with dystonia should delineate the time course of symptoms (acute, subacute, or chronic), distribution, whether it is present all the time or paroxysmal (if paroxysmal, whether it is provoked by initiation of movement), whether there is a diurnal variation (worse toward the end of the day), presence of other symptoms, and family history of similar conditions.

The etiology or underlying causes of pediatric dystonia are quite heterogenous. It is helpful in the clinical setting to differentiate acute dystonia from subacute or chronic dystonia. Acute dystonia in general suggests that the dysfunction in the brain is acute and therefore should be evaluated urgently. Associated symptoms of fever or systemic symptoms suggest a primary central nervous system (CNS) infection or inflammation that requires urgent evaluation.

Subacute and chronic dystonia are usually due to more slowly progressive acquired conditions, genetic disorders, or heredodegenerative conditions.

Paroxysmal Dystonia

Paroxysmal dystonia in sleep should raise the suspicion of seizures and appropriate neurophysiologic evaluation may be needed to differentiate seizures from a movement disorder. Paroxysmal dystonic movements with alteration of consciousness should also raise the suspicion of seizures ( Table 40.6 ).

TABLE 40.6

Differential Diagnosis of Paroxysmal Dystonia

Paroxysmal kinesigenic dystonia Paroxysmal nonkinesigenic dystonia Sandifer syndrome Benign paroxysmal dystonia Seizures Alternating hemiplegia of childhood

Paroxysmal Kinesigenic Dyskinesia

Paroxysmal dystonia or choreoathetosis triggered by the initiation of movement suggests the diagnosis of paroxysmal kinesigenic dyskinesia (PKD) (see Table 40.2 ). PKD appears to be a heterogenous disorder in which initiation of movement triggers episodes of dystonia or choreoathetoid movements. The symptoms are often unilateral. Onset of symptoms is between ages 1 and 20 years. The episodes of dystonia are clinically distinct from seizures because consciousness is fully preserved, and the episodes are triggered by the initiation of movement. There is no associated pain with these episodes. The episodes last seconds to less than a minute. Some patients have additional neurologic disorders such as benign infantile epilepsy. Infantile convulsions followed by PKD in late childhood or adolescence is thought to be a variant form of PKD.

The diagnosis of PKD is confirmed by the absence of organic disease or structural abnormality on neuroimaging and the response to anticonvulsant medications such as carbamazepine, usually in low doses. This condition may be sporadic or familial. Familial PKD can be caused by variants in the proline-rich transmembrane protein 2 ( PRRT2 ). However, this gene is found in only a portion of individuals with PKD. Variants in KCNA1 are identified in some families with PKD. A diagnostic approach to paroxysmal dyskinesias is noted in Fig. 40.3 .

Sandifer Syndrome

Episodic arching or dystonic posture of the neck and back in an infant or child can be seen in the setting of reflux. These episodes are usually related to feeds.

Benign Paroxysmal Torticollis

This is thought to be a migraine variant. In this condition children have paroxysmal episodes of head and/or trunk tilt that can last for hours or days, usually without other symptoms. Onset can be as early as the first year of life. Usually these episodes gradually decrease with age and resolve or evolve into episodes of migraine as the child grows older. At initial presentation, a detailed clinical evaluation should be undertaken, with appropriate testing to rule out organic causes. Careful monitoring should occur to determine whether these symptoms evolve into those of migraine or change to suggest a chronic neurogenetic dystonia that would warrant further evaluation.

Alternating Hemiplegia of Childhood

Alternating hemiplegia of childhood (AHC) is a rare condition presenting in childhood with episodes of temporary paralysis, often affecting one side of the body (hemiplegia). The episodes usually occur before age 18 months and last from minutes to days. Although not primarily a movement disorder, individuals can also have episodic choreoathetosis or dystonia in addition to episodes of hemiplegia. The episodes of abnormal movements can occur during or separate from the episodes of paralysis. These episodes can occur with triggers of stress, cold, or extreme tiredness. Sometimes there is no recognizable trigger. Other potential symptoms include developmental delay, abnormal eye movements, and seizures. Most individuals have pathogenic variants in ATP1A3, and a smaller number have variants in ATP1A2 . There is a high rate of de novo (sporadic) events, so many patients do not have a family history of similar symptoms. When there is a family history, it tends to follow an autosomal dominant pattern. Several treatments have been used including flunarizine, benzodiazepines, topiramate, oral adenosine triphosphate (ATP), coenzyme Q, acetazolamide, aripiprazole, and dextromethorphan, with various rates of success in aborting attacks or decreasing their frequency.