Neuritis is simply pain resulting from an irritated nerve. The sural nerve is one of the five nerves that crosses the ankle and then provides sensation to the foot. The sural nerve travels down the back of the leg along the Achilles tendon and crosses over to the back of the fibula (outside or "lateral" ankle bone) before it curves down along the heel and proceeds out to the little toe. The sural nerve only provides sensation to a small area along the outside of the foot and the 4th and 5th toes.
The sural nerve can become irritated from shoes, such as a thick seam or strap that pushes on the Achilles tendon, outside of the heel or the foot. Because the nerve is right under the skin, this sort of pressure or mechanical irritation can cause sural neuritis. This can produce tingling, numbness or burning pain along the course of the nerve. Neuritis pain can also radiate or shoot along the nerve out to the fourth and fifth toes, or up the back of the leg. It can also cause pain along the outside of the heel bone.
A more concerning cause of sural neuritis is related to scarring. In some cases, the sural nerve can become "entrapped" or wrapped up in scar tissue that pulls on the nerve resulting in irritation of the nerve and pain. When the sural nerve is entrapped, it is often because of the healing that takes place after surgery. Some surgeries that have incisions close to the sural can lead to nerve entrapment.
The most common culprits of sural nerve entrapment are Achilles tendon lengthening surgery, Achilles tendon surgical repair after a torn tendon, ankle fracture surgery for a broken ankle, flatfoot surgery and fifth metatarsal fracture surgery.
Sometimes the neuritis can be improved with simple treatments like icing and anti-inflammatories. It is important however to make sure you stop the irritation to the nerve. Get rid of any shoes that might be irritating the nerve. Some ski boots and cycling shoes can do this. If the nerve is entrapped, injections or physical therapy may help mobilize and break up the scar tissue. Sometimes surgery is required to free any of the scar tissue from around the nerve, but surgery should always be a last resort.