Tarsal tunnel syndrome (TTS) is a nerve compression syndrome or nerve entrapment syndrome causing a painful foot condition in which the tibial nerve is entrapped as it travels through the tarsal tunnel. The tarsal tunnel is found along the inner leg behind the medial malleolus (bump on the inside of the ankle). The posterior tibial artery, tibial nerve, and tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles travel in a bundle through the tarsal tunnel. Inside the tunnel, the nerve splits into three segments. One nerve (calcaneal) continues to the heel, the other two (medial and lateral plantar nerves) continue on to the bottom of the foot. The tarsal tunnel is delineated by bone on the inside and the flexor retinaculum on the outside. People with TTS typically complain of numbness in the foot radiating to the big toe and the first three toes, pain, burning, electrical sensations, and tingling over the base of the foot and the heel. Depending on the area of entrapment, other areas can be affected. If the entrapment is high, the entire foot can be affected as varying branches of the tibial nerve can become involved. Ankle pain is also present in patients who have high level entrapments. Inflammation or swelling can occur within this tunnel for a number of reasons. The flexor retinaculum has a limited ability to stretch, so increased pressure will eventually cause compression on the nerve within the tunnel. As pressure increases on the nerves, the blood flow decreases. Nerves respond with altered sensations like tingling and numbness. Fluid collects in the foot when standing and walking and this makes the condition worse. As small muscles lose their nerve supply they can create a cramping feeling.
Symptoms Some of the symptoms are:
Pain and tingling in and around ankles and sometimes the toes Swelling of the feet and ankle area. Painful burning, tingling, or numb sensations in the lower legs. Pain worsens and spreads after standing for long periods; pain is worse with activity and is relieved by rest. Electric shock sensations Pain radiating up into the leg, behind the shin, and down into the arch, heel, and toes Hot and cold sensations in the feet A feeling as though the feet do not have enough padding Pain while operating automobiles Pain along the posterior tibial nerve path Burning sensation on the bottom of foot that radiates upward reaching the knee "Pins and needles"-type feeling and increased sensation on the feet A positive Tinel's sign Tinel's sign is a tingling electric shock sensation that occurs when you tap over an affected nerve. The sensation usually travels into the foot but can also travel up the inner leg as well.
Causes
It is difficult to determine the exact cause of tarsal tunnel syndrome. It is important to attempt to determine the source of the problem. Treatment and the potential outcome of the treatment may depend on the cause. Anything that creates pressure in the tarsal tunnel can cause TTS. This would include benign tumors or cysts, bone spurs, inflammation of the tendon sheath, nerve ganglions, or swelling from a broken or sprained ankle. Varicose veins (that may or may not be visible) can also cause compression of the nerve. TTS is more common in athletes and other active people. These people put more stress on the tarsal tunnel area. Flat feet may cause an increase in pressure in the tunnel region and this can cause nerve compression. Those with lower back problems may have symptoms. Back problems with the L4, L5 and S1 regions are suspect and might suggest a "Double Crush" issue: one "crush" (nerve pinch or entrapment) in the lower back, and the second in the tunnel area. In some cases, TTS can simply be idiopathic.
Rheumatoid Arthritis has also been associated with TTS. Neurofibromatosis can also cause TTS. This is a disease that results in the formation of pigmented, cutaneous neurofibromas. These masses, in a specific case, were shown to have the ability to invade the tarsal tunnel causing pressure, therefore resulting in TTS. Diabetes makes the peripheral nerve susceptible to nerve compression, as part of the double crush hypothesis. In contrast to carpal tunnel syndrome due to one tunnel at the wrist for the median nerve, there are four tunnels in the medial ankle for tarsal tunnels syndrome. If there is a positive Tinel sign when you tap over the inside of the ankle, such that tingling is felt into the foot, then there is an 80% chance that decompressing the tarsal tunnel will relieve the symptoms of pain and numbness in a diabetic with tarsal tunnel syndrome.
Risk factors Anything compromising the tunnel of the posterior tibial nerve proves significant in the risk of causing TTS. Neuropathy can occur in the lower limb through many modalities, some of which include obesity and inflammation around the joints. By association, this includes risk factors such as RA, compressed shoes, pregnancy, diabetes and thyroid diseases
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