Foot Pain

Sural Nerve Entrapment Explained

Sural Nerve Entrapment Explained

Before we can discuss what sural nerve entrapment is, you really should know what the sural nerve is and what it does.

The sural nerve is also referred to as the short saphenous nerve. It is the sensory nerve located in the lower leg. This nerve lies very close to the short saphenous vein, which is a major vein located in the calf.

The sural nerve can begin from just behind the knee to just below the ankle. This particular nerve is often used for nerve grafts and biopsies.

The sural nerve begins and the juncture of the lateral and medial sural cutaneous nerves. In most individuals, this typically occurs very low in the leg- even at or below the ankle in some cases.

On the other hand, in a few individuals, the sural nerve can begin as high as behind the knee. , in some individuals, the sural nerve is actually simply a continuation of the medial sural cutaneous nerve.

This nerve travels down an individual’s calf just below the surface of the skin, passing close to the Achilles tendon and then ending in the space between the heel and the bony bump on the outside of the ankle, known as the lateral malleolus.

It actually continues into the foot, reaching the little toe- but once it passes the ankle, it is given a different name- the lateral dorsal cutaneous nerve.

The sural nerve conveys sensory information regarding the lower calf and outer foot to the brain- damage to this nerve can result in extreme pain in the leg or foot.

However, if damage does occur, it can be treated by removing part of the nerve. Of course, removal of a portion of the nerve can result in numbness in the ankle and side of the foot- but the nearby nerves will grow in to compensate, which restores most of the feeling to the area.

Due to the fact that the sural nerve is just below the skin and it’s basically not important to essential bodily functioning, it is often used when a nerve biopsy is necessary.

To perform a biopsy, the surgeon will inject a local anesthetic and then, using the short saphenous vein to guide him/her, will locate the sural nerve and then remove a piece about an inch long.

The wound will then be stitched closed and then covered with gauze moistened with saline. The sample will then be placed under a microscope and examined for evidence of nerve disorders.

Additionally, this nerve is often chosen to be used in nerve grafts. This is where a piece of the nerve will be taken out and transplanted into an area where nerves have been damaged.

The donor piece will be spliced with the existing nerve to restore muscle functioning and sensation. This procedure is commonly used to restore the feeling in damaged limbs.

The sural nerve is being transplanted more often into the pelvic area after prostate surgery to restore any lost sexual functioning.

Sural Nerve Entrapment

Sural Nerve Neuropathy

Though the sural nerve is not necessarily essential to bodily functioning, it is still a nerve, and just like other bodily tissues, can experience disease and/or trauma.

The sural nerve is a peripheral nerve, meaning that it serves to communicate with the brain and spinal cord. Sural nerve damage is a subtype of peripheral neuropathy.

There are some important characteristics of sural nerve damage related to the functioning and the anatomy of the involved structures.

Types of Neurons and Related Anatomy

Nerve cells, also referred to as neurons are divided into three major categories:

  • Sensory
  • Motor
  • Interneurons

The sensory neurons pick up the sensory signals and then take them to the spinal cord and the brain. On the other hand, the motor neurons take commands from the spinal cord and the brain and carry them to the muscles or glands to tell them what to do.

However, no matter what their primary function, all neurons have the same specific structural components:

  • Cell body
  • Axon
  • Dendrites

The cell body holds the nucleus and is the center of the metabolism of the neuron. The axon is a very long fiber of nerve that carries the signals away from the cell body.

The dendrites are short projections that carry the signals that are coming into the cell. The axon is often covered by a myelin sheath.

Types of Peripheral Neuropathy

Basically a nerve is a corded bundle of axons. There are a few forms of neuropathy:

  • Mono-neuropathy
  • Poly neuropathy

Mono-neuropathy is basically a neurological disorder that is caused by a single nerve malfunctioning. However, when several of the nerves become dysfunctional at the same time, it is referred to as polyneuropathy.

Experts have agreed that widespread peripheral neuropathy, also referred to as polyneuropathy, very often involves the sural nerve in some way. However, true mono-neuropathy, or isolated sural neuropathy is a very rare condition.

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Causes of Sural Nerve Neuropathy

One study that was featured in “Muscle and Nerve” clinical journal claims that trauma is the most common reason for sural nerve neuropathy.

Possible causes of trauma include fracture of the ankle, sprained ankle, stripping of veins, surgery of the knee, running for long distances, laceration of the ankle, gunshot to the ankle and external compression.

Experts claim that compression could be due to tears of the calf muscle or overgrowth of the muscles.

Some other causes of sural nerve neuropathy include: blood vessel inflammation, also referred to as vasculitis; biopsy of the sural nerve; diabetes; and ganglion cysts.

Due to the fact that the sural nerve is so close to the surface of the skin, it makes it much more likely to become injured due to compressions on the skin and the fact that most injuries occur on the surface of the skin.

Signs and Symptoms of Sural Nerve Neuropathy

Nerve damage- and the signs and symptoms of that nerve damage- can actually occur anywhere on the sural nerve. Sural nerve neuropathy often means that the individual will experience pain and other abnormal sensations in the skin of the ankle and foot, including tingling and numbness.

In most cases, these feelings will be much worse in the evenings and at night- even to the point of causing disruptions in sleep.

Some of the other common symptoms of sural nerve neuropathy include shooting spasms, burning, hypersensitivity to the area, pain, numbness, and even weakness in the area surrounding the nerve.

An individual with sural nerve neuropathy may also experience a reduction in motor functioning.

Diagnosing Sural Nerve Neuropathy

There are several different diagnostic procedures used to diagnose peripheral neuropathy, including sural nerve neuropathy.

  • Neurological testing
  • General physical exam
  • Patient history- in detail
  • Blood testing
  • Nerve/skin biopsies
  • Imaging

However, you should be aware that isolated sural neuropathy is often much more challenging to diagnose than other forms of peripheral neuropathy and will also require additional testing including an electro-physiologic evaluation.

Treatment of Sural Nerve Neuropathy

Surgical release has been claimed to be the best possible treatment for sural nerve neuropathy that is due to compression or entrapment of the sural nerve.

Sural nerve neuropathy that is connected with problems with the ankle may also require some physiotherapy, reconstruction, or bracing.

Basically, just as with any other disorder, the key to managing sural nerve neuropathy is to control or even get rid of the causes by treating the underlying disease and addressing any behaviors that could be causing or contributing to further damage to the nerve.

Nerve Entrapment and Athletes

Very often, athletes will complain of having leg pain and problems. Typically, these conditions are due to entrapment of the sural nerve or even other peripheral nerves.

Of course, we all know that leg pain caused by exercise is a very common condition and has lots of different apparent causes.

In many cases, leg pain that is caused by exercising is due to many different reasons, and can be localized or can be a great distance from the pain site.

Once a physician has ruled out things such as musculoskeletal problems, vascular problems, and even compartment syndrome problems, the symptoms of nerve entrapment should come into play as a potential cause of the leg pain.

Non-neural Causes of Leg Pain

There are several different non-neural reasons an individual could experience leg pain. They are as follows:

Shin Splints

The term shin splints actually covers a variety of disorders that could be a result of leg pain caused by exercising. In the beginning, “shin splints” were thought to be a result of an injury to the tibialis posterior tendon. Other conditions involving overuse have also been wrongly called “shin splints,” such as:

  • Compartment syndrome
  • Tibial periostitis
  • Tibialis anterior strain
  • Tibial stress fracture

Due to the fact that the above conditions have totally different causes, the term “shin splints” is not a very useful term. Instead, the physician should seek to find and address the specific condition that is present.

Muscle Strain

You may not know this, but you can actually damage your muscles by overstretching them. The muscle that is most often injured due to overstretching is the tibialis anterior, in front of the shin.

Symptoms of a muscle strain are as follows: acute pain in the muscle where the tear is, swelling, and inflammation. Once the swelling has reduced, you should treat this condition by stretching and strengthening the muscle that is affected. However, make sure to stop when you’re experiencing pain.

Tendonopathy

Tendonopathy is a condition in which microtears in the tendon result in inflammation in the surrounding tissue. This is another “overuse” injury that is most often caused from excessive repetitive movements, mostly overstretching a muscle.

When it comes to the leg muscles, the one that is most often affected is the tibialis posterior, usually due to repeated hyperpronation.

Symptoms of Tendonopathy include swelling, pain, and a “crunchy” feeling, or palpable crepitus on the tendon during contraction of the muscle.

The pain will typically happen at the beginning and just following exercise. When beginning treatment, painful activities should be stopped and you should start taking anti-inflammatories.

Of course, you should be aware that you should not cease all activities and completely rest because tendons truly do heal much more effectively when they are given mild loading.

Once the pain and inflammation have reduced, the affected tendon should be strengthened and stretched.

Medial Tibial Stress Syndrome

One of the natural consequences of weight bearing is bone bending. Of course, the wider bones are much more resistant to bending than the narrower ones and therefore, that makes them much less likely to become injured.

Repetitively bending bones causes a long bone to widen its cross section by causing the cells to lay down new bone.

If the intensity of training increases during this process, the cells of the bone are not able to keep up with the growth and therefore the area will begin to experience inflammation.

This particular injury could also be made much worse by simultaneously and repetitively pulling the muscles of the periosteum.

With this injury, the area this is most likely to become affected is the lower half of the medial tibia, where the cross section of the bone is the most narrow.

Signs and symptoms of this condition include pain during weight bearing activities- especially running, as well as tenderness. In some cases, you may notice redness, warmth, and even swelling.

Treatment for this condition is full rest from painful activities, slowly and gradually returning to normal training. You should not be strengthening or stretching your muscles while experiencing symptoms.

Tibial Stress Fracture

A tibial stress fracture is an incomplete crack in the tibia when repetitively putting a load on the bone has decreased its ability to support the load.

This condition is much more likely to occur in specific sports such as with long-distance running. Once a tibial stress fracture has been diagnosed, an individual should completely rest for at least 15 days from weight bearing activities.

Though it is very uncommon, an individual who does not rest could experience spontaneous complete fractures. In most cases, a tibial stress fracture will heal in about four to eight weeks.

However, lesions on the front of the bone could actually take several months to heal and could end up requiring grafting or electrical stimulation. It is very common for a tibial stress fracture to reoccur.

Chronic Exertional Compartment Syndrome

Chronic exertional compartment syndrome is an overuse condition that is a result of tight fascia around the muscles, producing symptoms during training and up to around 15 minutes after training.

In most cases, this condition is characterized by a tightness in the rear lower leg, as well as feeling of pins and needles. The diagnosis can get a confirmation by using pressure testing after an individual exercises.

Often, the individuals describe the pain as a cramping feeling. There may also be some muscle tears present.

In some cases, a physician will recommend using elective fasciotomy in order to release the fascia and therefore reduce the pressure.

This condition should not be confused with acute compartment syndrome, as the latter is a medical emergency that can happen after being hit in the lower leg directly.

Popliteal Artery Entrapment Syndrome

This is an extremely uncommon condition that is found among young individuals involved in sports that have a signs and symptoms of restricted blood flow to their lower leg.

These indications are pain, paresthesia, and pallor. This condition is due to intensity of exercise and drops away very quickly upon cessation.

Upon a post-exercise examination, a physician will most likely find arterial bruits, which is sounds of local blood flow using a stethoscope, and diminished or even an absent pulse.

Compression could possibly happen at the start of the medial head of plantaris or gastrocnemius due to the artery taking the wrong course.

Surgically removing the structure causing the compression is usually suggested as an effective treatment.

Nerve Entrapment Syndromes

The term “peripheral nerve entrapment” refers to the mechanical irritation in which a specific peripheral nerve becomes injured in an anatomical location that is vulnerable.

Nerve entrapments cause a disturbance in the functioning of the nerve. Nerve entrapment could possibly occur at any site due to tissue damage, including tumors, hematomas, or fractures.

There are several sites which the peripheral nerves are in confined spaces and therefore at a much greater risk of becoming compressed.

Physicians treating these conditions must also think about other causes of nerve entrapment including hereditary, inflammatory, degenerative, metabolic, and vascular diseases because these can also cause local nerve damage.

Factors that can predispose an individual for developing nerve compression are repetitive actions that involve the extremity that is affected, RA, tenosynovitis, alcoholism, acromegaly, amyloidosis, mucopolysaccharidosis, diabetes, gout, deficiency in vitamin B, alteration in fluid balance, and even trauma.

In some cases, a nerve entrapment will seem very similar to compartment syndrome, Tendonopathy, and even arterial entrapment. Individuals experiencing this condition will often describe the pain as shooting and sharp.

The condition can involve any combination of nerves. The best way to diagnose a nerve entrapment condition is to obtain a detailed history and performing a detailed, focused exam.

The best time to test individuals for nerve entrapment is after they have exercised. The area should be carefully examined and if possible, palpate the nerve along its course to identify the site of the entrapment or injury.

Of course, spinal and central problems must be addressed first and physicians should consider using diagnostic nerve blocks.

Saphenous Nerve Entrapment

Anatomy of saphenous nerve

This is where the sensory branch of the femoral nerve goes down into the canal known as the adductor canal and then goes through the fascia over the Sartorius and then travels along the long saphenous vein.

The two main branches of the saphenous nerve are the infrapatellar, which is located near the knee and the descending which is located near the inner end of the tibia bone.

Damage or entrapment of this nerve can be involved in conditions or injuries such as direct trauma, bursitis, and even MCL injuries.

Additionally, damage can occur during surgery such as a hamstring graft to treat reconstruction of the ACL or even surgery to treat varicose veins.

Individuals experiencing saphenous nerve entrapment will most often have knee pain, especially after working out their quadriceps. The pain could also be present at night and could be a burning pain.

Treatment for saphenous nerve problems include injections of medications or even destruction and/or removal of the infrapatellar ranches of the nerve.

Sural Nerve Entrapment

This is a very rare cause of pain related to exercise, but still can occur. Compression due to various reasons such as mass lesions, ganglia, scar tissue, thrombophlebitis, and even surgical trauma can cause sural nerve entrapment/problems.

Symptoms of this condition are very similar, if not identical, to those related to Achilles Tendonopathy. The nerve will be irritated much higher up and is often accompanied by a very small muscle hernia. Additionally, another symptom of this condition is post-exercise numbness.

Physicians prefer to treat this condition conservatively, with surgery working best only when a specific point of sural nerve entrapment has been pointed out.

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