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.   Pictures and videotaping of affected infants are helpful in delineating the dystonic movements. Periodic follow-up is often a prerequisite to making an accurate diagnosis.
The term infantile, in this case, refers to children <2 years of age. Of all dystonia cases, 45% are primary and 55% are secondary (35% related to specific syndromes; 20% other secondary causes). Syndromic types are mostly related to metabolic diseases.
Diagnosis involves recognising the abnormal movements as dystonic, and then categorising the type. Several conditions, although not actually dystonias in themselves, mimic dystonias (e.g., stereotypies), and these need to be considered in the differential diagnosis.
Several types of dystonia are more likely to develop the severe complication of status dystonicus (dystonic storm). This requires urgent therapy. In addition, it is important to correctly diagnose some of the conditions that mimic primary dystonia because they require specific urgent treatment.
Pitfalls in diagnosis include the fact that dopa-responsive dystonia (Segawa syndrome, dystonia-parkinsonism with diurnal fluctuation) is usually misdiagnosed as spastic diplegic or quadriplegic cerebral palsy, intractable epilepsy, or hereditary spastic paraplegia.   This diagnosis needs to be considered in any child with paroxysmal progressive hypertonia of unknown origin.
Department of Pediatrics and Neurology
University of Chicago
KS is an author of a reference cited in this monograph.
The author wishes to acknowledge the contribution of Muruvet Elkay, MD to this monograph. ME declares that she has no competing interests.
Neurobiology, Anatomy and Pediatrics
University of Rochester
Strong Memorial Hospital
JM is an author of a reference cited in this monograph.
Assistant Professor in Child Neurology and Developmental Pediatrics
1st Department of Pediatrics
Aristotle University of Thessaloniki
DZ declares that he has no competing interests.
Consultant Paediatric Neurologist
General Neurology & Complex Motor Disorders Service
Evelina Children’s Hospital
Guy’s & St Thomas’ NHS Foundation Trust
JPL declares that he has no competing interests.
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