The sural nerve is a peripheral nerve located in the lower leg and foot. It plays a role in transmitting sensory information, helping the brain communicate with the rest of the body. Positioned just beneath the skin’s surface, particularly in the back of the calf, it is a part of the peripheral nervous system. This nerve is significant for understanding various conditions affecting sensation in the leg and foot.
Anatomy and Path
The sural nerve forms from the convergence of two smaller sensory nerves: the medial sural cutaneous nerve, a branch of the tibial nerve, and the lateral sural cutaneous nerve, which originates from the common fibular (peroneal) nerve. This union typically occurs in the distal third of the leg, though its exact formation point can vary. After its formation, the sural nerve descends along the back of the leg, often running alongside the small saphenous vein.
The nerve then passes behind the lateral malleolus, the bony prominence on the outside of the ankle. From there, it extends into the foot, branching out to supply various areas. Its superficial course makes it susceptible to injury.
Sensory Role
The sural nerve is primarily a sensory nerve. Its main function is to provide sensation to specific regions of the lower leg, ankle, and foot. These sensations include touch, temperature, pain, and vibration.
The areas it innervates include the posterolateral aspect of the distal third of the leg, the lateral heel, and the lateral side of the ankle and foot. It also supplies sensation to the lateral border of the foot, extending towards the fifth toe.
Common Issues
One common problem is sural nerve entrapment, which occurs when surrounding tissues thicken and press on the nerve. This can be caused by scar tissue, tight fibrous arches, or external compression. Symptoms often include chronic pain, numbness, tingling, or a burning sensation in the posterior leg, ankle, and foot.
Neuropathy, such as that caused by long-term diabetes, can also affect the sural nerve, leading to altered sensation and pain. Direct trauma is another frequent cause of injury, including ankle sprains, fractures of bones like the calcaneus, or direct impact. Surgical procedures in the ankle region, such as Achilles tendon repair, can inadvertently damage the nerve due to its superficial location.
Inflammation of the nerve, known as sural neuritis, results in a burning sensation and tenderness along the side of the ankle and foot. Repetitive ankle sprains can stretch and irritate the nerve, contributing to this inflammation. Symptoms like burning, numbness, tingling, or sharp pain can be persistent and impact daily activities.
Identifying and Treating Problems
Diagnosing sural nerve issues begins with a physical examination and symptom review. Healthcare providers may perform specific tests, such as Tinel’s test, which involves tapping over the nerve to elicit tingling or an electrical sensation.
Nerve conduction studies are often used to assess the nerve’s function, measuring how quickly electrical signals travel along it. Imaging techniques like high-resolution ultrasound and magnetic resonance imaging (MRI) neurography can visualize the nerve and identify abnormalities such as thickening, displacement, or compression.
Conservative measures are often the first approach, including rest, applying ice, anti-inflammatory medications, and physical therapy. Orthotics or changes in footwear can also help reduce pressure on the nerve. For persistent pain, nerve blocks or steroid injections may be administered to reduce inflammation and discomfort. In cases where conservative treatments are insufficient or nerve compression is severe, surgical decompression may be considered to release the entrapped nerve or remove scar tissue. Consulting with a medical professional is important for proper diagnosis and a tailored treatment plan.