Congenital Myopathies

Diagnosis

In addition to clues provided by a patient's personal and family history, doctors will perform thorough physical and neurologic evaluations to rule out other diseases that can affect muscle function, such as muscular dystrophies and neurological disorders.

Doctors at Mayo have access to many specialized tests to better understand the myopathy, and, if possible, to identify the underlying genetic mutation.

These tests include:

• Blood tests to measure potassium levels.
• An electromyogram (EMG, electromyography) to record the electrical activity of the muscles. This involves inserting a thin-needle electrode into the muscle.
• A nerve conduction study (NCS, electroneurograph) to measure electrical nerve impulses. This involves taping two electrodes to the skin and sending a small shock between them.
• An exercise test to observe muscle response to exertion.
• A "provocative" test where a patient is exposed to suspected "triggers," such as carbohydrates, potassium, or cold.
• A thyroid-stimulating hormone (THS) test to rule out endocrine-related myopathies.
• An electrocardiogram (ECG) to observe the electrical activity that generates the heartbeat.
• A biopsy (muscle tissue sample) to observe nerve and muscle cell appearance and their behavior in response to different stimuli.
• Genetic testing (with a blood sample) to verify a particular mutation.