History And Definitions

In an attempt to distinguish the class of motor disturbances resulting from lesions of the basal ganglia, Kinnier Wilson coined the term extrapyramidal in his famous 1912 articled describing hepatolenticular degeneration, now known as Wilson's disease. This term was widely adopted thereafter and continues to be used today. The extrapyramidal system refers to the basal ganglia with their anatomical connections, and extrapyramidal disorders are hypokinetic and hyperkinetic states that ensue from lesions in these anatomical sites. Unfortunately, these terminologies are not absolutely accurate, and extrapyramidal is more a functional concept than a purely anatomical one. There are many other motor pathways that are anatomically extrapyramidal and yet not necessarily related to the basal ganglia, including cerebellar, reticulospinal, vestibulospinal, and rubrospinal pathways. Furthermore, most outflow from the basal ganglia goes to the cerebral cortex via the thalamus, and eventually influences the pyramidal system. In fact, a lesion of the pyramidal system that results in paralysis will eliminate the abnormal movements that originate from a basal gangliar disturbance. Another problem with the term extrapyramidal is the different ways it is used, creating ambiguity and possible misunderstanding. Although Wilson conceived of the term to refer to all types of hypokinetic and hyperkinetic disorders, psychiatrists today usually use the term extrapyramidal side effects to represent only drug-induced parkinsonism.

At present, the term movement disorder largely replaces the older term extrapyramidal disease because it is more descriptive and accurate. Almost all movement disorders stem from disturbances in the basal ganglia or their connections, but there are important exceptions. Myoclonus is one major example of a movement disorder of brain stem, cortical, or spinal cord origin, and conditions like painful legs/moving toes and the so-called jumpy stump syndrome emerge from injuries to the peripheral nervous system.

Movement disorders are clinically characterized by hypokinesia or hyperkinesia, and sometimes both. Hypokinesia technically means decreased amplitude of movement, but it is used also to represent bradykinesia (decreased speed of movement) and akinesia (absence of movement). The important element in hypokinesias is paucity of movement in the absence of weakness or paralysis. Hypokinesia is the hallmark of parkinsonism, a term that broadens hypokinesia when it is associated with tremor, rigidity, or balance problems. Hyperkinesia means excessive movement and generally refers to a wide variety of abnormal involuntary movements or dyskinesias. Hyperkinetic voluntary movements, which are common in attention deficit disorders and some psychiatric disorders like mania, are not generally considered as hyperkinesias in this context. The listing of the various hypokinesias and hyperkinesias along with definitions of each are presentedin IabJe...16-1 .

TABLE 16-1 -- LIST OF MOVEMENT DISORDERS

HYPOKINESIA (Parkinsonism)

Poverty of movement in speed or amplitude, synonomous with akinesia and bradykinesia

Pure parkinsonism

Akinesia or rest tremor associated with rigidity and/or postural reflex deficits

Parkinsonism-plus

Parkinsonism ocourring in association with other signs, such as vertical gaze paresis, hypotension and dysautonomia, apraxias

HYPERKINESIAS

Involuntary movements that occur spontaneously or during activity, synonomous with dyskinesias

Akathitic movements

Stereotypic movements (usually legs) that occur in response to internal restless feelings

Athetosis

Twisting cortorsion, a form of dystonia, usually associated with birth injury or cerebrovascular accidents

Ballism

Violent chorea, involving large muscle groups

Chorea

Involuntary rapid and irregular movements

Dystonia

Twisting, sustained posture

Hemifacial spasm

Unilateral facial contractions

Hyperekplexia

Enhanced and pathological startle response

Myoclonus

Shocklike jerks, focal or generalized

Stereotypy

Repetitive movement, simple or complex

Tics

Stereotypy that typically involves face, neck and vocal apparatus more than other body parts

Tremor

To-and-fro oscillation around a joint

Important characteristics used to describe and classify hyperkinesias include regularity, velocity and duration, and anatomical distribution. In terms of regularity, tremors are generally rhythmical to-and-fro movements, and likewise, tics and stereotypies are repetitive movements that are highly predictable in quality, although intermittent in frequency. In contrast, chorea is best characterized by rapid movements flowing irregularly from one body part to another without a predictable pattern. In terms of velocity and duration, rapid movements include myoclonus, chorea, ballism, clonic tics, and some tremors. Slow movements are dystonic or athetotic, showing a sustained contraction of muscles, often with a twisting component. Finally, several hyperkinesias have a propensity to involve certain body regions, for example akathitic movements almost always affect the legs, and tics tend to be most prominent in the face, eyes, and neck. Dystonic movements occur in all body regions but are particularly common in the neck muscles (torticollis).

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