  myotonia (myo from greek; muscle, and tonus from latin; tension) is a symptom of a small handful of certain neuromuscular disorders characterized by delayed relaxation (prolonged contraction) of the skeletal muscles after voluntary contraction or electrical stimulation. myotonia is present in myotonia congenita, paramyotonia congenita and myotonic dystrophy. generally, repeated contraction of the muscle can alleviate the myotonia and relax the muscles thus improving the condition, however this is not the case in paramyotonia congenita. this phenomenon is known as "warm-up" and is not to be confused with warming up before exercise, though they may appear similar. individuals with the disorder may have trouble releasing their grip on objects or may have difficulty rising from a sitting position and a stiff, awkward gait. myotonia can affect all muscle groups; however, the pattern of affected muscles can vary depending on the specific disorder involved. people suffering from disorders involving myotonia can have a life-threatening reaction to certain anaesthetics; one of these conditions occurs when the patient is under anaesthetic and is termed "malignant hyperthermia". ==causes== myotonia may present in the following diseases with different causes related to the ion channels in the skeletal muscle fiber membrane (sarcolemma). ===myotonic muscular dystrophy=== two documented types, dm1 and dm2 exist. in myotonic dystrophy a nucleotide expansion of either of two genes, related to type of disease, results in failure of correct expression (splicing of the mrna) of the clc-1 ion channel, due to accumulation of rna in the cyotsol of the cell.{{cite journal|last=mankodi|first=a|author2=takahashi, mp |author3=jiang, h |author4=beck, cl |author5=bowers, wj |author6=moxley, rt |author7=cannon, sc |author8= thornton, ca |title=expanded cug repeats trigger aberrant splicing of clc-1 chloride channel pre-mrna and hyperexcitability of skeletal muscle in myotonic dystrophy.|journal=molecular cell|date=jul 2002|volume=10|issue=1|pages=35â44|pmid=12150905|doi=10.1016/s1097-
Myoneural_junction_and_neuromuscular_diseases Symptoms_and_signs:_Nervous_system Symptoms_and_signs:_musculoskeletal_system