Definition

Tarsal tunnel syndrome is a condition where the tibial nerve becomes strained or compressed as it passes through the tarsal tunnel. The tibial nerve innervates the muscles of the lower leg and foot. The tarsal tunnel, which the nerve passes through, is located in the ankle and is composed of the bones of the heel and ligaments that connect various structures of the foot.

Causes

Tarsal tunnel syndrome is caused by the compression of the tibial nerve as it passes through the tarsal tunnel. This compression can be caused by various conditions, either extrinsic (outside the structure of the tarsal tunnel) or intrinsic (within the structure). Extrinsic causes of tarsal tunnel syndrome can include shoes that are too small, trauma, deformities of the leg such as bowlegs or knock-knees, joint inflammation, surgical scars, foot swelling, diabetes, and more. Intrinsic causes can include inflammation of the tendons, calcification around the nerve, bony growths that press on the nerve, enlarged veins, and masses such as lipomas, ganglion cysts, and various tumors.

Risk factor

Risk factors for tarsal tunnel syndrome can include systemic diseases such as diabetes mellitus, hypothyroidism (low thyroid hormone levels), gout (joint inflammation due to high uric acid levels), and hyperlipidemia (high levels of fats in the blood). About 43% of all tarsal tunnel syndrome cases have a history of trauma before symptoms appear, such as ankle sprains.

Symptoms

Symptoms of tarsal tunnel syndrome can include:

• Sharp, stabbing pain that can radiate to the sole and calf. This pain may worsen with foot movement, especially when walking or standing, and improve with rest.
• Numbness or tingling.
• A burning sensation in the foot.
• Muscle weakness in the foot.

Diagnosis

Diagnosing tarsal tunnel syndrome heavily relies on the patient’s medical history and physical examination. The doctor may ask about conditions related to nerve problems in the feet, such as diabetes mellitus and hypothyroidism. They may also inquire about medications such as vasodilators, gout medications, anticonvulsants, antimalarials, headache medications, anti-nausea drugs, chemotherapy drugs, and vitamins. The doctor might also ask about exposure to HIV/AIDS, Lyme disease (a nerve-affecting illness caused by tick bites), and travel history for potential leprosy exposure.

Afterward, the doctor may perform several direct examinations. The foot can be moved to identify the position and distribution of the pain. The ankle might be warmer than the surrounding structures. In severe cases, muscle atrophy in the calf might be noted. The doctor can perform a test by gently tapping the ankle. Additionally, sensory tests can be conducted to compare the sensation in both feet and to detect any reduction in sensation in the affected foot.

Laboratory tests can also be performed, including urinalysis, fasting blood glucose, hemoglobin A1c (which binds to sugar), urea, creatinine, complete blood count, erythrocyte sedimentation rate, and vitamin B12 levels. If there are signs of autoimmune diseases like rheumatoid arthritis, a Rheumatoid Factor (RF) test may be conducted.

Imaging studies of the ankle, such as ultrasound, plain X-rays, or Magnetic Resonance Imaging (MRI), can help identify structures compressing the tibial nerve. Plain X-rays can detect structural abnormalities in the foot, fractures, bone masses, and bone spurs. Meanwhile, MRI can be used to detect tendon inflammation or masses such as tumors.

Electromyography (EMG) can also be performed to assess electrical conduction in the nerves and muscles, helping to pinpoint specific abnormalities in the tibial nerve.

Management

Treatment for tarsal tunnel syndrome depends on the cause, loss of function, and muscle atrophy, and can be managed with or without surgery. The goal of non-surgical therapy is to reduce pain, inflammation, and stress on the tissues. Pain relief medications, both general and nerve-specific, may be prescribed. Other treatments may include physical therapy to strengthen muscles and reduce pain by decreasing mechanical stress. Special shoes can also be used to correct foot deformities and relieve the tarsal tunnel. If tarsal tunnel syndrome is caused by a ganglion cyst, aspiration of the cyst with ultrasound guidance can be performed. If due to foot swelling, steroid injections can reduce inflammation in the ankle.

Surgery is recommended if non-surgical treatments fail to improve the condition, if it worsens, or if the cause of the nerve compression can be surgically removed. The surgery aims to release the tarsal tunnel. The success rate of surgery can range from 44-96%.

After treatment begins or surgery is performed, you may be advised to avoid activities that strain the ankle for 3 weeks to ensure optimal healing. However, early movement of the foot is essential to prevent the formation of permanent scar tissue, which can potentially cause tarsal tunnel syndrome. Physical therapy is crucial to maintain the strength and range of motion of the ankle and alleviate pain. Wearing comfortable shoes is also important to enhance recovery from tarsal tunnel syndrome.

Complications

If tarsal tunnel syndrome is left untreated, it can cause problems with the tibial nerve and its branches. Pain can persist continuously. In severe cases, muscle weakness and calf muscle atrophy can occur. Surgical complications can include poor wound healing, infection, and scar tissue formation. Tarsal tunnel release may not always adequately relieve pain and other symptoms. Additionally, surgical damage to the nerve can occur, significantly impairing foot function.

Prevention

Preventing tarsal tunnel syndrome is closely related to its causes. If preceded by systemic diseases such as diabetes mellitus, treatment adherence is crucial to prevent nerve issues. Wearing comfortable shoes is also essential to prevent tarsal tunnel syndrome. Ankle trauma is challenging to prevent, but if it occurs, early treatment to reduce inflammation is crucial to prevent tarsal tunnel syndrome.

When to see a doctor?

See a doctor immediately if you experience stabbing pain in the ankle, accompanied by a burning sensation, tingling, and numbness, radiating to the sole of the foot and calf. This pain is characteristic of nerve issues, with a specific pattern for the tibial nerve. The cause of these symptoms may not necessarily be tarsal tunnel syndrome, but similar conditions can endanger your foot.