The sural nerve, also known as the short saphenous nerve, is a sensory nerve in the lower leg of humans. It lies close to the short saphenous vein, a major vein in the calf, and may begin anywhere from behind the knee to just below the ankle. The nerve is often used for biopsies and grafts.
This nerve usually begins where the medial sural cutaneous nerve and the lateral sural cutaneous nerve, two nerves in the lower leg, come together. For most individuals, this occurs quite low on the leg, even at or below the ankle. For a few, however, the nerve may begin as high as the back of the knee. In some people, the sural nerve is simply a continuation of the medial sural cutaneous nerve.
The nerve travels down the calf not far under the surface of the skin. It passes near the Achilles tendon and ends in the space between the heel bone and the lateral malleolus, the bony bump on the outside of the ankle. The nerve continues on into the foot, eventually reaching the little toe, but from the ankle on is considered to be a separate anatomical part called the lateral dorsal cutaneous nerve.
The body uses this nerve to convey sensory information about the lower calf and outer foot to the brain. Damage to the nerve can cause severe pain in the leg or foot. This can be treated by removing part of the nerve, which usually results in an area of numbness around the ankle and side of the foot. Nearby nerves will often grow to compensate, restoring most of the feeling to the damaged area.
Due to its proximity to the skin, the redundancy of nerves in the surrounding tissue, and its relative unimportance to essential body functions, the sural nerve is a popular candidate for removal as part of a biopsy. To perform a nerve biopsy, the surgeon first injects a local anesthetic. Using the short saphenous vein as a guide, the sural nerve is located. A small piece, usually about an inch (2.5 cm) long, is removed with a quick, sharp cut. The wound is stitched shut and covered with saline-moistened gauze. The sample is then examined using a microscope to look for evidence of disorders including amyloidosis, sarcoidosis, leprosy, and demyelination.
For similar reasons, the sural nerve is also often used as the donor nerve in nerve grafts. In a nerve graft, a piece of healthy nerve is transplanted to an area where nerve damage has occurred. It is spliced with the existing nerves in order to restore muscle function or sensation. The procedure is commonly performed to restore feeling to damaged limbs. Increasingly, the sural nerve may be transplanted to the pelvic area in an attempt to restore lost sexual function after prostate cancer surgery.