Myotonia

What it means

An involuntary and painless delay in the relaxation of skeletal muscle following contraction or electrical stimulation.

Patients often describe myotonia as stiffness that is worse at the onset of activity and that improves with repeated muscle contractions. Myotonia tends to worsen in cold weather. Myotonia can be elicited by voluntary muscle contraction of by muscle percussion (e.g., by tapping the thenar eminence). During physical examination, myotonia may be elicited by asking the patient to make a tight fist and then quickly open the hand. Myotonia is caused by an abnormality in the muscle membrane, i.e., of the ion channels that control the contraction of muscle fibers.

Rare diseases that can present with this18

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions, and Orphanet separately records 2 diseases where this sign is specifically absent. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Delayed relaxation of muscle fibers after contraction · Delayed relaxation of muscle fibres after contraction