Symptoms

Due to the altered hyper-excitability of the muscle cell membrane, stimuli can elicit intense muscle contractions and a single stimulus causes prolonged muscle contraction.  

It means that muscles stiffen up when startled or excited, but cannot relax right away.

·         A unifying feature of myotonia

·         being mild to severe for different patients

·         affecting any skeletal muscle

·         being particularly noticeable during movement after a period of rest

Unique characteristics:

Myotonia congentia:

1.    Warm up phenomenon

        - Repeated movements temporarily alleviate the muscle stiffness

2.    Mild muscle weakness after the sustained tensing

3.    Muscle hypertrophy

       - People exercising in gym get big muscles, so do myotonia patients who frequently but involuntarily use muscles.

Contrasted with the dominant form (Thomsen’s disease), the recessive form (Becker-type myotonia) are much more common,

and have more severe symptoms and earlier on-set (generally at childhood, but Thomsen type may appear in adulthood).

Paramyotonia:

1.    Cold sensitive

       - Besides muscle exercises, low temperature triggers myotonic symptoms.

2.    Very early onset – neonatal to infancy

3.    Repeated movements worsen the condition

4.    flaccid weakness lasts for hours

5.    no hypertrophy

K⁺ aggravated myotonia

1.    K⁺ sensitive

       - K⁺ rich foods such as bananas trigger myotonia

2.    may associate with severe permanent symptoms

3.    sometimes effects come out about 20mins after exercises#

4.    no muscle weakness

5.    no hypertropy