Sural Neuritis

(Also: Sural Neuralgia)

Summary

Sural neuritis (a.k.a. sural neuralgia) is pain that occurs due to irritation or injury of the sural nerve. The pain is typically described as a burning sensation located on the outside of the foot and ankle. It may occur following surgery of the foot and ankle or after a direct injury to the nerve itself. In many cases, the condition will resolve on its own with time. Non-surgical treatment includes aggressive massage for nerve desensitization, oral medications to reduce irritation, and avoidance of direct pressure on the nerve. On rare occasions, surgery may be indicated to release scar tissue that has developed around the nerve or to excise the damaged nerve is symptoms are severe.

Clinical Presentations

The sural nerve runs down the back of the leg, behind the outside edge (lateral) of the ankle, and along the outside of the foot. The nerve provides sensation to the lateral foot and ankle as well as the 4th and 5th toes. Neuritis may develop as a result of injury, irritation, or inflammation along the nerve. Sural neuritis leads to pain on the outside of the foot and ankle that is commonly described as burning in nature. The involved area is often hypersensitive to touch and there may be altered sensation, such as numbness, along the remaining course of the nerve. Symptoms of sural neuritis can be aggravated by direct pressure on the nerve, commonly due to footwear. An ankle sprain, is a common cause of sural neuritis, as it results in a stretching injury of the nerve. This type of sural neuritis commonly resolves on its own with time and/or non-surgical treatment. Although uncommon, the sural nerve may also be injured during standard surgical approaches, as the course of the nerve around the foot and ankle is variable. For instance, retractors used to aid in exposure during surgery may inadvertently stretch the nerve, or excessive scarring may develop around the nerve after surgery. Swelling after an injury or surgery may also simply be enough to disturb the function of the nerve, and symptoms of neuritis can develop.

Physical Examination

Physical examination is the key to diagnosis. Tapping over the nerve (known as the Tinel) creates an “electrical” sensation that is most exaggerated at the location of nerve injury. There may also be localized swelling and tenderness on the outside of the foot and ankle, along the course of the nerve.

Imaging Studies

Plain x-rays are rarely helpful in the diagnosis of sural neuritis. The nerve is a soft tissue structure and does not show up on x-rays. MRI is also unlikely to be helpful, as the sural nerve is too small to visualize. Nonetheless, these imaging studies may provide some information regarding previous surgery or other injuries to the area that may be related to the current symptoms.

Treatment

Treatment of sural neuritis is aimed at addressing the underlying cause of nerve injury – whether it is an ankle sprain or scar tissue.

Non-operative Treatment

Most cases of sural neuritis will either resolve over time or can be treated successfully with non-operative measures. There are a variety of non-operative treatments for sural neuritis:

Desensitization. Direct massage over the irritated nerve is designed to both desensitize the nerve and break up any scar tissue around the nerve. Although desensitization is initially uncomfortable, it will typically improve over time.
Medication. Medications like Gabapentin (Neurontin) or Pregabalin (Lyrica) may help to stabilize the irritated nerve.
Corticosteroid injection. A localized corticosteroid injection may help to break up the scar tissue around the nerve and improve pain/inflammation.
Comfort shoe wear. Choosing the right footwear may avoid direct pressure over the damaged nerve area. Applying padding over the involved area may also reduce irritation and improve symptoms.

Operative Treatment

If there is nerve pain that does not respond to non-surgical treatment, extensive scarring of the nerve or irritation from hardware implanted during a surgical procedure, surgery may be indicated. Surgical treatment for sural neuritis usually involves either:

Releasing the nerve. Surgery to release (free up) the nerve from surrounding scar tissue and/or surgery to remove any irritating structures (ex. retained hardware) may be helpful. However, scar tissue has a tendency to recur. As such, nerve wrapping with collagen may be useful in preventing the recurrent formation of scar tissue.
Nerve resection. If the sural nerve is too damaged from previous scarring or symptoms are severe, it is often best to remove the nerve. Since the sural nerve only provides sensation to the outside of the foot and ankle, resection of the nerve results in numbness along the course of the nerve without the loss of any motor function.

Potential Complications

Although unlikely, one of the potential concerns of sural neuritis is complex regional pain syndrome which can be a debilitating condition.

Previously edited by Lance Silverman, MD

Edited on November 9, 2018

mf/ 11.6.19