The sural nerve is a sensory nerve located in the lower leg and foot, playing a role in how the body perceives its surroundings. It transmits information about sensation from the skin to the brain. Understanding its location and function provides insight into certain conditions affecting the lower limb.
Its Journey Through the Leg
The sural nerve typically forms in the calf from the convergence of two smaller nerves: the medial sural cutaneous nerve, which branches from the tibial nerve, and the lateral sural cutaneous nerve, originating from the common fibular nerve. This union usually occurs in the distal third of the leg, though its exact formation point can vary among individuals. The sural nerve travels superficially, descending along the back of the calf. It often runs alongside the small saphenous vein.
The nerve passes posterior to the lateral malleolus, the bony prominence on the outside of the ankle. From there, it extends into the foot, terminating as the lateral dorsal cutaneous nerve. Its course through the posterior and lateral lower leg makes its location predictable, despite some variations.
What the Sural Nerve Does
The sural nerve is a purely sensory nerve, transmitting sensations rather than controlling muscle movement. It enables the detection of various stimuli, including touch, temperature, pain, and vibration. This sensory input also contributes to the body’s awareness of foot position, which is important for maintaining balance.
The sural nerve supplies sensation to the lower-lateral part of the calf, outer ankle, outer heel, and the lateral aspect of the foot, extending to the little toe. Any disruption to this nerve can therefore affect sensation in these distinct regions.
Common Concerns and Clinical Importance
Understanding the sural nerve’s location and function is valuable due to its susceptibility to injury and its role in medical procedures. The nerve can be affected by trauma, such as ankle sprains or fractures involving the fibula or calcaneus. Additionally, external compression from tight footwear, like ski boots, can cause irritation.
Sural nerve entrapment occurs when surrounding tissues thicken or scar, pressing on the nerve. This can result from injuries, surgery, or repetitive stress. Symptoms often include numbness, tingling, burning sensations, or pain in the areas the nerve supplies.
The sural nerve also has clinical utility in diagnostic and reconstructive medicine. Due to its superficial location and purely sensory nature, it is frequently used as a site for nerve biopsies, particularly when investigating peripheral neuropathies like vasculitis or amyloidosis. While generally well-tolerated, such biopsies can sometimes lead to persistent pain, infection, or sensory loss. Furthermore, its length and sensory function make it a common donor nerve for grafting procedures to repair damaged nerves. It can also be inadvertently damaged during certain surgeries, such as those involving the Achilles tendon, ankle, or during procedures to harvest the small saphenous vein due to their close proximity.