A reasonably common foot complaint is general pain and tingling in and around the inner ankle and sometimes radiating from the heel, through the arch and towards the toes. The feet may appear swollen with painful symptoms such as burning or shooting pains, tingling (like electric shocks), or numb sensations in the lower legs. The discomfort follows the path of the Posterior Tibial Nerve which runs down the back of the leg around the inside ankle and along the sole of the foot. Pain may intensify with activity and is usually eased with rest. Painful episodes are usually rapid and depending on the severity, the ability to walk even short distances can be severely inhibited. If left untreated, the condition may progress to permanent nerve damage. Causes of nerve damage (neuropathy) vary and it is important to have a proper diagnosis to effect relief. The correct diagnosis of TTS is often based on physical examination with a simple Tinel’s test to identify Tarsal. Tinel's test (or sign) describes a tingling electric shock sensation in the foot when the affected nerve is tapped around the inner ankle bone (medial malleolus) with the fingers. With other causes an X-ray can rule out fractures, and= ultrasound for synovitis or ganglia and a MRI will determine space occupying lesions or other causes of nerve compression.
The tarsal tunnel describes a narrow space that lies on the inside of the ankle next to the ankle bones. The tunnel is covered with a thick ligament (flexor retinaculum) which protects and maintains the structures contained within the tunnel. These are arteries, veins, tendons, and nerves and pass from the back of the leg into the sole of the foot. When the posterior tibial nerve is compressed in the tunnel a neuropathy will result. Once through the tunnel a branch of the posterior tibial nerve supplies the back of the heel (calcaneal nerve), with the other two branches i.e. medial and lateral plantar nerves, supplying the bottom of the foot. Depending on the area of nerve entrapment, the entire foot maybe affected as varying branches of the tibial nerve can become involved and ankle pain is also present with high level entrapments. Inflammation or swelling causes an increase in pressure within the tunnel which compresses the nerve and causing the blood flow to decrease. Nerves respond with altered sensations like tingling and numbness. When small muscles lose nerve supply this can create a cramping feeling. Fluid retention around the ankles will also make the condition worse.
The exact cause of Tarsal Tunnel Syndrome is often difficult to discern and a number of factors are usually involved. Treatment and the potential outcome of the treatment will depend on the cause. Anything that creates pressure in the Tarsal Tunnel results in TTS. This includes benign tumors or cysts, bone spurs, inflammation of the tendon sheath, nerve ganglions, or swelling from a broken or sprained ankle. Varicose veins or fluid retention around the ankle can also cause compression of the nerve. Currently there is no confirmed epidemiology and hence it is difficult to estimate the incidence in the general public. Most authorities agree TTS is more likely to be diagnosed in women than men and tends to be found in active sporting types. Mobile flat feet may result in increased incidence and those with lower back problems may also have symptoms. Back problems with the L4, L5 and S1 regions are suspect and might suggest a "Double Crush" issue i.e. one "crush" (nerve pinch or entrapment) in the lower back, and the second in the tunnel area. An ankle sprain may increase inflammation and swelling in and near the tunnel. Some systemic diseases, such as rheumatoid disease, cause swelling in joints and that may compress on the nerve but more often than not TTS is idiopathic with no known cause.
Treatments typically include rest, ice, manipulation, strengthening of tibialis anterior, tibialis posterior, peroneus and short toe flexors, casting with a walker boot, corticosteroid and anesthetic injections, hot wax baths, wrapping, compression hose, and orthotics. Medications may include various anti-inflammatories and local anesthetic patches are also a treatment that helps some patients. If non-invasive treatment measures fail, surgery may be recommended to decompress the area. Many patients (50%) report good results, although some, experience no improvement or a worsening of symptoms.