Movement disorders are defined as either a loss or poverty (akinesia)
or slowness (bradykinesia) of movement that is not associated with
weakness or an excess of abnormal involuntary movements. Based on
this, movement disorders are classified as either hypokinetic (Parkinsonism) or
hyperkinetic (tremor, dystonia, chorea, tics, myoclonus). Movement
disorders are generally caused by abnormalities in basal ganglia
and their connections. The basal ganglia are that group of gray
matter nuclei lying deep within the cerebral hemispheres (caudate,
putamen, and pallidum), the diencephalon (subthalamic nucleus),
and the mesencephalon (substantia nigra). The causes of many movement
disorders remain unknown, in others various causes have been identified
ranging from environmental toxins, genetic causes, medications,
metabolic disorders, structural lesions, neurodegenerative causes,
infectious, postinfectious causes, and autoimmune and psychogenic
causes. More recent genetic, biochemical, and functional imagine
advances have provided additional information about the pathophysiology
and etiology of some movement disorders. Many diseases have now
been localized to a specific gene (PD, dystonia, ataxia, paroxysmal
dyskinesia, etc); several inherited movement disorders are due to
expanded repeats of the trinucleotide cytosine-adenosine-quanosine
(CAG) such as Huntington disease, some spinocerebellar ataxias (SCAs),
and Dentatorubral and Pallidoluysian Atrophy (DRPLA).
Movement disorders must be seen, because description of them
by the parents or patient might be vague and will not lead to a
proper diagnosis. Children also manifest a variety of intriguing
physiologic and developmental abnormalities that await proper classification,
and only the experienced movement disorders observer can distinguish those
from movement disorders.
Many abnormal movement disorders are paroxysmal or at least intermittent;
they can be induced by sleep, emotional upset, movement, or other
triggering factors. The physician needs to ask what are triggering
factors and what makes the movement better and worse, if there is
fluctuation of symptoms during the day, and if there are any associated
features (ie, loss of consciousness or awareness). Many paroxysmal
movements in pediatric population are associated with epilepsy,
and this has to be to exclude by appropriate investigation (see Chapter 557). Movement disorders may be classified
- Hyperkinetic movement disorders
- Chorea and athetosis
- Tics and Tourette syndrome
- Hypokinetic movement disorders
- Chorea is a combination of fluid or jerky movement
affecting any part of the body; chorea can resemble a dance (from
Greek word), and movements are repetitive but not rhythmic or stereotyped.
Patients with chorea appear restless.
- Athetosis is a slow, writhing movement of the
limbs that may occur alone but is often associated with chorea (choreoathetosis).
- Ballismus is a high-amplitude, violent flinging
of a limb from the shoulder or pelvis and is considered to be an extreme
form of chorea.
Common causes of chorea are listed in Table
Table 566-1. Causes of Chorea
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