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Episodic movement disorders 

Episodic movement disorders

Ivan Donaldson

, C. David Marsden

, Susanne A. Schneider

, and Kailash P. Bhatia

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date: 26 May 2022

Episodic movement disorders are characterized by circumscribed attacks of disturbed movement without loss of consciousness, superimposed on a background state in which such abnormality is absent. Neurological examination between attacks is usually, although not necessarily, normal. In many cases the beginning and end of the movement disturbance is abrupt. Usually attacks are repetitive. Although there is no clear cut-off point, episodic movement disorders last seconds, minutes, hours, and occasionally days, rather than weeks or months. These disorders do not include 1) the usual fluctuation in baseline state of involuntary movements due to stress, posture, sleep, etc., 2) intermittent symptoms occurring due to the early stage of the disease, 3) periods of therapeutically induced improvement, 4) prolonged periods of illness interspersed with remissions, or 5) weakness or paralysis without involuntary movement. Episodic movement disorders may be conveniently classified according to the main type of abnormal movement. Diseases causing intermittent paralysis are not included. Some disorders, such as epilepsy, can produce more than one type of movement and are included in several categories. Most disorders can be focal, segmental, unilateral, or generalized and this may vary during or between attacks in the same patient. Others such as ‘drop attacks’ are, by their nature, always generalized. Disorders producing intermittent chorea may at times show dystonia and these are grouped together. Tonic attacks are distinguished by sustained rigidity. If movement occurs, it is present only at the start of the paroxysm as the body part assumes the position of tonic spasm. In some cases the distinction between dystonic and tonic episodes is difficult or artifical. Clonic and myoclonic attacks are characterized by brief jerks. Disorders causing asterixis and intermittent tremor are frequently associated with signs of diffuse neurological impairment, including diminished conscious level and systemic abnormality. Unsteady gait and other cerebellar features are prominent in the intermittent ataxias. In drop attacks there is sudden falling, without loss of consciousness. Patients with restlessness frequently experience discomfort, which is temporarily alleviated by movement. Those with idiopathic disorders are episodic in that they may show marked diurnal fluctuation and are usually worse or present only in bed.

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