Clinical Manifestation of Dystonia in Children
Dystonia refers to a syndrome of involuntary sustained or spasmodic muscle contractions involving co-contraction of the agonist and the antagonist. The movements are usually slow and sustained, and they often occur in a repetitive and patterned manner; however, they can be unpredictable and fluctuate.
The frequent abnormal posturing and twisting can be painful, and the functional impact of dystonia can vary from barely noticeable to severely disabling. Consequently, dystonias can have a profound effect on the personal, vocational, and emotional life of a patient and can impact his/her ability to live independently.
- Regardless of the cause, dystonic contractions can have a chronic course and can lead to severe persistent pain and disability. Because each type of dystonia is treated in a different manner, the distinction between the various types is therapeutically important.
Dystonias can be classified according to the following characteristics:
- Age of onset
- Anatomic distribution
Classification by age of onset
With regard to patient age, dystonias can be classified as follows:
- Infantile dystonia – Begins before age 2 years
- Childhood dystonia – Begins at age 2-12 years
- Juvenile dystonia – Begins at age 13-20 years
- Adult dystonia – Begins after age 20 years
- Primary (idiopathic) dystonia
- Primary, or idiopathic, dystonias can present in a sporadic, autosomal dominant, autosomal recessive, or X-linked recessive manner. Heritable childhood-onset dystonia is particularly common among Ashkenazi Jewish people.
- Currently, at least 12 types of dystonia can be distinguished on a genetic basi. Identification of more dystonia genes may lead to better understanding and treatment of these largely nondegenerative disorders.
This may result from a wide variety of neurologic diseases or inherited metabolic defects, including the following:
- Huntington disease
- Hallervorden-Spatz disease
- Wilson disease (hepatolenticular degeneration)
- Leigh disease
- Lipid storage disease
- Central nervous system infections
- Cerebral or cerebellar tumors
- Drug intoxication – Dopamine antagonists, neuroleptics, metoclopramide, and haloperidol, among others
- Structural or hypoxic injury to the basal ganglia brainstem structures
On the basis of its clinical distribution, dystonia is classified as follows:
- Focal dystonia – Involves a single body part
- Segmental dystonia – Affects 2 or more contiguous regions of the body; examples of segmental dystonias of the head and neck include craniocervical dystonia, blepharospasm, oromandibular dystonia, and laryngeal dystonia
- Multifocal dystonia – Consists of abnormalities in noncontiguous body parts
- Generalized dystonia – Involves segmental crural dystonia and at least 1 other body part; dystonia musculorum deformans (or torsion dystonia), a generalized form of the disease, involves the trunk and limbs.
- Hemidystonia – Also called unilateral dystonia; usually associated with abnormalities in the contralateral basal ganglia
- Cervical dystonia, or torticollis, is the most common focal dystonia. Local limb dystonias often begin as action or task-specific dystonias, such as writer’s cramp dystonia or musician’s dystonia (repetitive wrist or finger movements). In 20-30% of patients, focal dystonias become segmental or multifocal.
- Pseudodystonia encompasses a group of movement disorders that may express dystonialike movements as one of the clinical features of a syndrome. Sandifer syndrome, stiff-man syndrome, and Isaacs syndrome may fall into this category.
Common Types of Dystonias
- Cervical dystonia, or torticollis, is the most common focal dystonia. It has an insidious onset in people aged 30-50 years, although it can begin earlier. Cervical dystonia commonly affects women.
- Intermittent spasms of the neck muscles or abnormal head movements occur because of contractions of the sternocleidomastoid, trapezius, and posterior cervical muscles. This effect results in a patterned, repetitive, and spasmodic movement that causes the head to twist (rotational torticollis), extend (retrocollis), flex (anterocollis), or tilt toward the shoulder (laterocollis). The patient may display more than 1 of these head movements simultaneously.
- Patients may report psychiatric symptoms associated with depression or anxiety. These may be due to the chronic course of the illness rather than to real psychopathology.
Upper limb dystonia
- Upper limb dystonia causes cramping and posturing of the elbows, hands, and fingers that lead to the inability to perform certain occupational tasks. The literature describes at least 55 occupations in which individuals are affected by this condition. Men and women are affected with equal frequency. Onset is in persons aged 10-50 years.
- A common upper limb dystonia is known as writer’s cramp, occupational cramp, or graphospasm. This task-specific dystonia, manifesting as hyperextension or hyperflexion of the wrist and fingers, may be triggered by repetitive activities such as writing and attempting to play the piano or other musical instruments. After cessation of the task, the spasm disappears. Although torticollis, tremor, and pain are accompanying symptoms, the spasm itself usually limits further activities.
- The results of general physical and neuromusculoskeletal examinations are usually unremarkable. Some clinicians inadvertently label these conditions as occupational neuroses.
Lower limb dystonia
- This may occur in stroke or dystonia-parkinsonism syndrome and lead to painful positioning of the leg, impaired gait, and altered bone development.
- A study by Martino et al indicated that lower limb dystonia is an uncommon condition in adulthood. Evaluating 579 patients with adult-onset primary dystonia, the investigators found 11 patients (8 women, 3 men) with lower limb dystonia, with the condition existing either alone (4 patients) or as part of a segmental/multifocal dystonia (7 patients). In 63.6% of the patients, the dystonia spread to the lower limb from another site, while in the remaining patients, the condition originated in the lower limb. The authors noted that 64% of the patients required treatment.
Oromandibular and lingual dystonia
- Oromandibular, facial, and lingual dystonias are grouped together because of their possible coexistence. Cranial dystonia, commonly known as Meige syndrome, is the most common craniocervical dystonia. Women are more commonly affected, and onset is in the sixth decade of life.
Dystonia musculorum deformans (torsion dystonia)
- Dystonia musculorum deformans, or torsion dystonia, is the term used to describe a generalized form of dystonia that involves the trunk and limbs. There are at least 2 types, and onset may begin in childhood or adolescence, infrequently occurring as abnormal movement of a limb after an activity. The movements progress in severity and frequency until they become a continuous spasm, resulting in contortion of the body.
- At first, rest relieves the spasms, but as the disease progresses, the level of activity and positioning have no effect. The shoulder, trunk, and pelvic muscles undergo spasmodic twisting, as do the limbs. The hands are seldom involved. The orofacial muscles also may be affected, leading to dysarthria and dysphagia.
- The pathology of dystonia musculorum deformans has yet to be described. In some cases, genetics appear to play a role. Autosomal dominant and recessive patterns of inheritance have been reported. A rare, sex-linked form associated with parkinsonism has been described in the Philippines.
Tardive dyskinesia (tardive dystonia)
- This is a common complication of long-term antipsychotic drug treatment due to dopamine receptor antagonism. The precise mechanism is unknown, but the risk appears to increase with advancing age. When medication is withdrawn relatively early in a patient’s treatment, the dyskinesia may reverse, whereas after 6 months of exposure, the movement disorder may persist indefinitely. The clinical features of tardive dyskinesia include abnormal choreoathetoid movements, especially involving, in adults, the face and mouth (ie, blepharospasm, torticollis, oromandibular dystonia), and in children, the limbs.
- Impaired basal ganglia outflow is thought to play a role in the genesis of some dystonias. Lesions in the putamen have been linked to hemidystonia. Bilateral putaminal involvement may be responsible for generalized dystonia.
- Torticollis and hand dystonia are thought to result from involvement of the head of the caudate nucleus and thalamus, respectively. Disease of the thalamus and subthalamus, as well as derangement of hypothalamic function, also has been suspected.
- Because the basal ganglia play a role in maintaining normal head posture, the basal ganglia and the vestibulo-ocular reflex pathway have been implicated in the development of cervical dystonia. Disturbances of neurotransmitter systems also have been described in dystonias. Abnormalities in blink reflex recovery suggest involvement of the brainstem. Cervical and upper limb traumas have been implicated as well.
- A study by McClelland et al indicated that there are significant differences in the rate and pattern of pallidal firing according to the etiology and phenotype of dystonia. For example, the median firing frequency of the internal globus pallidus was higher in patients with primary dystonia than in those with secondary static dystonia and was higher in patients with progressive dystonia secondary to neuronal brain iron accumulation than in the other two groups.
- Drug-induced supersensitivity of striatal dopamine receptors and abnormality of gamma-aminobutyric acid (GABA)–ergic neurons are proposed mechanisms for some drug-induced dystonias. Although supersensitivity is an inevitable accompaniment of long-term antipsychotic drug treatment, tardive dyskinesia does not always occur.
- Abnormalities of serotonin, dopamine, and norepinephrine in specific cerebral structures also have been associated with dystonia musculorum deformans. In a literature review of human and animal studies, Smit et al pointed out that reduced levels of the serotonin metabolite 5-hydroxyindolacetic acid have been found in association with dystonia. The investigators also identified 89 cases, reported in 49 papers, that demonstrated a relationship between dystonia and drugs that impact the serotonergic system. .
History, Physical Examination, and Diagnostic Studies
- In dystonia, as in all neuromuscular disorders, history taking and physical examination are necessary. Family history is important; as many as 44% of patients have a family history of similar or other movement disorders.
- Dystonia may be a clinical manifestation of many treatable neurologic conditions; therefore, a thorough screening should be performed to exclude Wilson disease (ie, hepatolenticular degeneration), hypoxic brain injury, traumatic brain injury, Huntington disease, Leigh disease, lipid storage disease, and Parkinson disease.
- A number of medications can induce acute dystonic movements, and a careful investigation of the patient’s medication list must be performed to rule out iatrogenic causes. Common drugs that can induce movement disorders and dystonias include, but are not limited to, the following:
- Dopamine antagonists
- Valproic acid
- Dopamine agonists
- Monoamine oxidase inhibitors (MAOIs)
- Adrenergic agents
- Beta agonists
- Tricyclic antidepressants
- Oral contraceptives
- Various laboratory studies should be considered in the evaluation of dystonia. Blood chemistries, liver functions, ceruloplasmin levels, and blood copper levels may be appropriate.
- Magnetic resonance imaging (MRI) and computed tomography (CT) scanning of the brain are especially important in the pediatric population and may identify hypoxic, hemorrhagic, or tumorous lesions. Slit-lamp eye examination for Kayser-Fleischer rings and 24-hour urine copper analysis also may be useful.
- Genetic screening for DYT gene abnormalities and genetic counseling are important for patients who have had an onset of primary dystonia before age 30 years or for persons who have an affected relative.