During certain activities, particularly weight-bearing activities (e.g. walking or running) a compressive force, is sometimes placed on the interdigital nerves and surrounding soft tissue, between the metatarsal bones (this is often the case with tight fitting shoes or in patients with flat feet). If this force is repetitive enough and beyond what the nerve and soft tissue can withstand, swelling to the nerve and soft tissue may occur. This may result in pain, tenderness, pins and needles or numbness in the forefoot or toes. When this happens, the condition is known as a Morton's neuroma.
Although in many areas of medicine, it?s easy to pinpoint the exact source of a problem (the way a specific germ causes a certain illness with recognizable symptoms), neuromas are harder to categorize. While there isn?t really one exact cause, podiatric physicians tend to agree that a neuroma can occur in response to the irritation of a nerve by one or more factors. Abnormality in foot function or foot mechanics: In other words, a foot that doesn?t move the way science thinks it should. In general, this means a pronated foot (one with an excessive rolling motion when the patient is walking, running or doing any kind of activity), because it causes excessive strain on the nerve. If you are not certain whether or not this is a problem for you, ask your podiatric physician, who will be able to examine your feet, as well as the wear pattern on your shoe, and give you an answer. Foot mechanics, and problems with them, tend to run in families, so if you know that a relative has had foot pain similar to yours, be sure to mention it.
The most common symptom of Morton's neuroma is localized pain in the interspace between the third and fourth toes. It can be sharp or dull, and is worsened by wearing shoes and by walking. Pain usually is less severe when the foot is not bearing weight.
The clinical symptoms should quickly lead your doctor to suspect a neuroma. When examined, the doctor may feel a "click" which is known as Mulder's sign. There may be tenderness in the interspace. The metatarsal bones will also be examined both clinically (and often with an xray). Tenderness at one of the metatarsal bones can suggest an overstress reaction (pre-stress fracture or stress fracture) in the bone. An ultrasound scan can confirm the diagnosis and is a less expensive and at this time, at least as sensitive a test as an MRI. An x-ray does not show neuromas, but can be useful to "rule out" other causes of the pain.
Non Surgical Treatment
In most cases, initial treatment for this condition consists of padding and taping to disperse weight away from the neuroma. If the patient has flatfeet, an arch support is incorporated into footwear. The patient is instructed to wear shoes with wide toe boxes and avoid shoes with high heels. An injection of local anesthetic to relieve pain and a corticosteroid to reduce inflammation may be administered. The patient is advised to return in a week or 2 to monitor progress. If the pain has been relieved, the neuroma is probably small and caused by the structure of the patient's foot and the type of shoes the patient wears. It can be relieved by a custom-fitted orthotic that helps maintain the foot in a better position. Another type of therapy that may be used is alcohol sclerosing injections. In this treatment, the doctor injects a small amount of alcohol in the area of the neuroma area to help harden (sclerose) the nerve and relieve the pain. Injections are given every 7-10 days and, in many cases, 4-7 injections are needed for maximum relief. Please ask your physician for more information regarding this type of treatment.
Surgery to excise the neuroma is usually performed under general anaesthetic in a day surgery facility. After surgery you will have to keep your foot dry for two weeks. Generally neuroma surgery allows for early weight bearing and protection in some type of post op shoe gear. Some neuromas may reoccur, but this is rare. Most studies on patient satisfaction after neuroma surgery show approximately 90% reduction of pain and about 85% of all patients rated the overall satisfaction with the results as excellent or good.
Wearing shoes that fit properly and that have plenty of room in the toe area may help prevent Morton's neuroma.