The nerves that supply the sensation to the lesser toes originate on the bottom of the foot. They travel between the long bones of the foot, metatarsals, and at the head of the metatarsal the nerve will divide into 2 nerves, one going to the adjacent 2 toes. In the area where the nerve is about to divide, a ligament crosses between and attached to the metatarsal heads and perpendicular to the nerve. This ligament is called the deep transverse intermetatarsal ligament. When there is an over use injury or injury to the nerve, the nerve can become swollen. This enlarged nerve then can become pinched between the metatarsal heads and compressed by the ligament crossing the nerve. This then causes pain and discomfort. Often patients that have a plantar plate tear of the toe joint are misdiagnosed as having a neuroma. A Morton’s neuroma is classically described and most often affects the nerve that supplies sensation to the 3rd and 4th toes that lies between the 3rd and 4th metatarsals. Yet, it can occur at the nerve between any of the toes.
Causes:
A neuroma is often caused by an overuse of the foot and toes from a repetitive motion. It can also be caused by blunt trauma to the forefoot or direct insult to the nerve. The continued and static compression of the nerve over time will cause more severe damage to the nerve and lessen the success of conservative treatments.
Symptoms:
When the nerve is compressed the signals and information the nerve needs to translate to the skin and back to the brain can be decreased. This will lead to patients describing numbness, burning, tingling or shooting pains in the 2 adjacent toes. There can be a feeling of walking on a pebble or a rock on the ball of the foot. Some patients can feel or hear a clicking as the nerve rubs over the bones during gait. Often the symptoms can be reproduced in a squatting position with only the ball of the foot and the toes on the ground and the toes flexed.
Diagnosis:
Clinical evaluation of the foot is the most important way to evaluate for a neuroma. Palpation of the foot between and just behind the metatarsal heads will elicit pain and often electric shooting into the toes. Squeezing of the forefoot from side to side can reproduce the symptoms as well. Plain x-rays can show if there is any bone involvement that many contribute to the damage to the nerve. Special neurosensory examinations (PSSD) may need to be performed in order to evaluate the extent of the nerve damage. Ultrasound examination and MRI can also shoe the enlarged nerve in severe cases.
Treatment:
In the early stages of a neuroma, conservative treatments are often successful. Removal of the deforming force and activity that caused the damage is important. In acute cases, a period of immobilization in a special shoe or boot may be needed. Physical therapy is a very effective treatment for neuromas that are in the early stages. In acute cases use of catabolic steroid injections (cortisone) can be very helpful in reducing the pain and symptoms and help to cure the neuroma. Custom molded orthotics with special padding is an important part of treatment and lessens the chance for the neuroma to return. In more severe and chronic cases that have failed conservative therapies there are 4 main more invasive treatments available including alcohol sclerosis, cryotherapy, nerve decompression and nerve excision. Each treatment has benefits and setbacks and treatment is customized to the patient’s needs.
Alcohol Sclerosis: A special alcohol solution can be injected over the nerve. This solution has an affinity only for nerve tissue. It will slowly over several injections, deaden the nerve. The loss of the nerve can then leave the patient symptom free.
Cryotherapy: This is the method of freezing of the nerve. A small incision is made over the area of the nerve. A wand from the device is then inserted into the wound and placed over the nerve. The devise is then set to a specific amount of time to freeze the nerve. This allows the nerve to no longer transmit a nerve signal and therefore there is less pain. Most patients respond well to the treatment which is office based and done under local anesthesia. In certain cases, the procedure does not fully treat the nerve pain on the first attempt and a second treatment may be necessary.
Nerve Decompression: The most recent advance in neuroma therapy is nerve decompression. It is thought that, in many cases, the nerve is pinched by the overlying ligament that connects the metatarsal heads together. A simple surgery allows the release of this ligament allowing for increased space for the nerve and relief of pain. This surgery leaves the nerve intact and allows continued sensation to the toes.
Nerve Excision: The most traditional treatment for neuroma pain has been a nerve excision. This procedure allows for removal of the nerve from the metatarsal head region and decreases pain. There is a risk of the remaining nerve regrowing or getting scarred but overall, with proper technique, the risk is minimal.
Picture showing initial incision over the 3rd innerspace between the 3rd and 4th toe. |
Picture showing the deeper incision down to the level of the ligament crossing over the nerve. The instrument on the bottom of the picture is going under the ligament and over the nerve. |
Picture showing the nerve and its branches into the toes. Notice the thickness of the nerves. They are normally much thinner. |
Picture showing the nerve after excision from the foot. Notice the thickness of the nerve. |
The Foot and Ankle Institute has performed a great deal of research and treatment advancements related to neuroma care. We prefer to avoid nerve excision and try to save this for severe cases and in cases where conservative care and simple procedures such as alcohol injection, cryotherapy and nerve decompression do not work.
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