Abnormal movement disorders are classified as parkinsonism, dystonia, tremor, chorea, myoclonus, tics, stereotypies, and complex movement disorder. Dystonia is described as contraction of both agonist and antagonist muscles simultaneously, causing twisting and repetitive movements or abnormal postures.  The earlier the age of onset, the more generalised and severe the condition tends to be.
Dystonic movements are patterned and sustained. They repeatedly involve the same muscle groups. The urge to perform the dystonic movements is absent, and there is no relief after the dystonic movements are executed. Dystonia usually gets worse with fatigue and emotional stress and it gets better with sleep and relaxation.   Photographs and video footage of affected infants are helpful in delineating the dystonic movements. Periodic follow-up is often a prerequisite to making an accurate diagnosis.
Clinical characteristics (axis 1), which include age at onset, body distribution, temporal pattern, and associated features
Atiology (axis 2), which includes nervous system pathology and inheritance.
Information from the history and physical examination allows an initial classification and differential diagnosis to be made. The presence and absence of motor features and other signs and symptoms can narrow the differential diagnosis by indicating a particular dystonia syndrome and by directing the diagnostic evaluation towards groups of disorders associated with different clinical patterns, such as:
Isolated dystonia (dystonia alone or dystonia with tremor)
Combined dystonia (dystonia with other motor features)
Complex dystonia (dystonia with other symptoms).
The clinical evaluation may also indicate whether the condition is neurodegenerative or suggest an acquired or inherited aetiology.
Further investigations may be required including neuroimaging, evaluation for associated neurodevelopmental or systemic abnormalities, therapeutic trial of levodopa, or biochemical (including diagnostic lumbar puncture) and genetic tests.
Several pseudo-dystonias need to be considered in the differential diagnosis; these conditions involve dystonia-mimicking abnormal movements, but their aetiologies differ from those of dystonias.
The rapid identification of several conditions is important to prevent irreversible injury or death:
Drug-induced acquired dystonia
Pseudo-dystonia due to cervical instability
Multiple neurometabolic disorders, such as glutaric aciduria type I
Acute bilirubin encephalopathy.
Dopa-responsive dystonia (Segawa syndrome, dystonia-parkinsonism with diurnal fluctuation) needs to be considered in any infant or child with unknown diagnosis and normal MRI. It is usually misdiagnosed as spastic diplegic or quadriplegic cerebral palsy, intractable epilepsy, or hereditary spastic paraplegia.  
Shriners Hospital for Children, Chicago
Department of Pediatrics and Neurology
University of Chicago
KS is an author of a reference cited in this topic.
University of Chicago
NIH Medical Genetics & Genomics Residency
National Human Genome Research Institute
National Institutes of Health
SY is a member of the medical advisory board for the Alternating Hemiplegia of Childhood Foundation, a non-profit organisation.
The authors wish to acknowledge the contribution of Muruvet Elkay, MD to this topic.
Pediatrics (Neurology and Epilepsy)
Ann & Robert H. Lurie Children’s Hospital of Chicago
JB declares that she has no competing interests.
Neurobiology, Anatomy and Pediatrics
University of Rochester
Strong Memorial Hospital
JM is an author of a number of references cited in this topic.
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