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Movement disorders involve either too much or too little movement. One of the most common and important is Parkinson's disease where there is a mixture of too little (bradykinesia) and too much movement (tremor and drug induced dyskinesia); this is the subject for a future Bare Essentials article and will not be considered here.
Hyperkinetic movement disorders are clinically heterogeneous but there are some common themes in their diagnosis and management.
The first step in diagnosis is to describe the movement, so you need the relevant vocabulary (table 1), which will significantly narrow the differential diagnosis. Often this is straightforward but sometimes the movements do not fall neatly into a single descriptive category and combined terms are used (eg, myoclonus–dystonia).View this table:
Abnormal movements can be part of a more widespread neurological disorder. They then provide an important clue to the underlying diagnosis (eg, Huntington's disease, anti-N-methyl-d-aspartate (anti-NMDA) receptor encephalitis). Or they may be a complication of a previously diagnosed condition (eg, tremor in multiple sclerosis).
Almost all movement disorders can be caused or exacerbated by drugs; has the patient taken any relevant drugs now or in the past?
Many movement disorders are genetic. Is there a family history? Draw a family tree.
Movement disorders can be ‘functional’. But be careful, this diagnosis can be very difficult.
There are a number of rare and at times extraordinary hyperkinetic movement disorders, usually identified by pattern recognition. If you know the pattern you will recognise it.
A range of treatments is available for hyperkinetic movements, often providing useful relief of symptoms if not a cure.
Some conditions, although rare, are important not to miss because they respond very dramatically to treatment—notably dopa responsive dystonia and Wilson's disease.
Movement disorders taken together are common in …
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