The Un-Scratchable Itch
Many times I see patients that have been unsuccessfully treated for one or several conditions, and are coming for a second (sometimes 3rd or 4th!) opinion. I had an interesting case of a patient who had been treated for a very common type of heel pain (plantar fasciitis), but had minimal improvement. She had an array of typically very good treatments (stretching, shoe gear modification, oral medication, injections, physical therapy, etc.), but her symptoms persisted. She had pain in her heel and arch, and the pain was sometimes present in the morning or after periods of rest (typical of a plantar fasciitis), but also occurred at seemingly random times throughout the day. Sometimes walking/running would illicit no pain, sometimes it was unbearable. The pain was often burning in nature, sometimes sharp. After going through a thorough history, the patient also related an interesting tidbit… she had an annoying, persistent itch on the bottom of her foot, and had seen foot specialists and dermatologists and been treated with various creams but to no avail. The itch was present without any other dermatological signs or symptoms, and nothing seemed to relieve it.
Many patients will have very clearly identifiable symptoms and exacerbating factors which they can lucidly describe, and that correlate nicely with a specific condition. Sometimes, however, the patient has a difficult time describing the nature of their pain, and exactly what makes it worse (or what makes it feel better). While the patient above had obvious symptoms, they did not fit nicely into any diagnosis box. I see this difficulty many times when people are dealing with pathology involving nerves.
The above patient was examined, and sure enough a specific examination of an area known as the Tarsal Tunnel elicited a shooting, electrical type pain into her heel and arch, and also increased the “itchiness”. Is this case, the patient was not suffering from a plantar fasciitis, and had no dermatological reason for the itch, but was suffering from a condition known as tarsal tunnel syndrome.
Many people have heard of carpal tunnel syndrome. Tarsal tunnel syndrome (TTS) is a similar phenomenon that occurs in the foot. The tarsal tunnel refers to a specific anatomical area on the inside part of the foot and ankle. There is a specific ligament in the area (the laciniate ligament) that attaches from the medial malleolus of the tibia, to the heel bone (calcaneus). Thus a tunnel is formed with the ligament as the roof, and the bones as the floor of the tunnel. All the tendons, arteries, nerves and veins that travel to the bottom (plantar) foot pass through this tunnel. The main nerve passing through this area is known as the tibial nerve, which eventually branches to provide innervation to the bottom of the foot. For a variety of reasons, the tibial nerve can get compressed which will then cause pain to the bottom of the foot. This pain can present very differently for different patients, but most commonly will cause burning, or electrical type pain. Many times, it can also be associated with numbness, tingling, or hard to describe sensations which we refer to as paresthesias. In this particular case, the patient’s pain and “itching” sensation were both caused by a tarsal tunnel syndrome.
TTS can be a diagnosis of exclusion; where everything else is ruled out as a cause of pain. A focused exam needs to be performed over the tarsal tunnel, including percussing the area and looking for radiating pain or paresthesias to the heel, arch or toes (referred to as Tinel’s Sign) or, (less commonly) Valleix Sign, which is pain radiating up the leg. Physical exam and x-rays will often show a foot and ankle position which can increase pressure on the nerve (many times a patient will have a flat foot with excessive pronation which keeps the laciniate ligament taut, increasing pressure on the nerve). An MRI may be useful if there is a structure impinging on the nerve such as a ganglion cyst, accessory muscle belly, or inflammation of nearby tendons. Many times, an MRI is inconclusive, and a patient will be sent for a neurological exam known as an NCV/EMG to evaluate for nerve pathologies. This is often an important test, as it will also determine if there is nerve pathology from any were else in the lower extremity. Sometimes, compression of a nerve originating in the back can lead to similar foot pain and strange sensations.
Treatment for the condition can also vary based on the etiology. If it is simply a positional issue, proper shoe gear and custom orthotics and avoiding compression on the area simply will help. Many times, a topical or oral anti-inflammatory medication is needed. A doctor may need to use steroid injections as well. In cased when there is a mass in the tarsal tunnel, this will typically need to be removed surgically to provide relief. Sometimes, a surgical release of the ligament and any strictures around the nerve is necessary.
So, if you have pain or funny feelings, and are being treated for a foot condition with limited success, make sure you inquire about tarsal tunnel syndrome.