Biopsy

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Biopsy
Muscle and nerve :
Occasionally, doctors cannot determine the cause of the nerve damage or muscle weakness based on results of blood tests, imaging tests, EMG, or nerve conduction studies. In such cases, doctors typically refer the person to a specialist, who may remove a small sample of muscle tissue and sometimes a nerve to examine under a microscope (biopsy). The sample is removed from an area of the body where symptoms occur. The sample is stained to help doctors identify the pattern of muscle or nerve damage and to determine whether white blood cells (which indicate inflammation) are present.

Skin :
Often, the sensory nerve examination and EMG do not detect damage of the nerves that sense pain or that automatically regulate body processes (called autonomic nerves). Doctors may suspect such damage if people have less sensitivity to pain, have burning pain in their feet, feel dizzy or light-headed when they stand up, or sweat too much or too little. To check for this damage, doctors may use a small round cutter to remove a sample of skin (punch skin biopsy) and send it to a laboratory to be examined under a microscope. If the nerve endings in the skin sample have been destroyed, the cause may be a disorder (such as vasculitis) that affects small nerve fibers, including pain-sensing and autonomic nerves fibers