Also known as channelopathies, this group of rare genetic conditions is characterised by intermittent (periodic) attacks of muscle weakness (paralysis).
The attacks can be the result of stress, excitement, physical activity, heat or cold. Sometimes, the muscle weakness is confined to a small group of muscles. In other cases, it is more generalised and the whole body is unable to move.
It is very rare for the heart or the breathing, speaking or swallowing muscles to be affected. Attacks can last from minutes to days, depending on the type of periodic paralysis. At the end of an attack, muscle strength returns. Some people experience slow, progressive muscle weakness over time.
About 900 people in the UK have a form of periodic paralysis.
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