Morton's neuroma is an enlarged nerve that usually occurs in the third interspace, which is between the third and fourth toes. To understand Morton's neuroma further, it may be helpful to look at the anatomy of the foot. Problems often develop in the third interspace because part of the lateral plantar nerve combines with part of the medial plantar nerve here. When the two nerves combine, they are typically larger in diameter than those going to the other toes. Also, the nerve lies in subcutaneous tissue, just above the fat pad of the foot, close to an artery and vein. Above the nerve is a structure called the deep transverse metatarsal ligament. This ligament is very strong, holds the metatarsal bones together, and creates the ceiling of the nerve compartment. With each step, the ground pushes up on the enlarged nerve and the deep transverse metatarsal ligament pushes down. This causes compression in a confined space.
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.
Symptoms associated with a neuroma include a dull burning sensation radiating towards the toes, a cramping feeling, or even a stinging, tingling sensation that can be described as being similar to an electric shock. It is often worse when wearing shoes with most people finding the pain disappears when removing their shoes.
To diagnose Morton's neuroma the podiatrist commonly palpates the area to elicit pain, squeezing the toes from the side. Next he or she may try to feel the neuroma by pressing a thumb into the third interspace. The podiatrist then tries to elicit Mulder's sign, by palpating the affected interspace with one hand and squeezing the entire foot at the same time with the other hand. In many cases of Morton's neuroma, this causes an audible click, known as Mulder's sign. An x-ray should be taken to ensure that there is not a fracture. X-rays also can be used to examine the joints and bone density, ruling out arthritis (particularly rheumatoid arthritis and osteoarthritis).
Non Surgical Treatment
Initial therapies are nonsurgical and can involve one or more of the following treatments Changes in footwear. Avoid high heels or tight shoes, and wear wider shoes with lower heels and a soft sole. This enables the bones to spread out and may reduce pressure on the nerve, giving it time to heal. Custom shoe inserts and pads also help relieve irritation by lifting and separating the bones, reducing the pressure on the nerve. One or more injections of a corticosteroid medication can reduce the swelling and inflammation of the nerve, bringing some relief. Massaging the affected area can provide some momentary relief. Several studies have shown that a combination of roomier, more comfortable shoes, nonsteroidal anti-inflammatory medication, custom foot orthoses and cortisone injections provide relief in over 80 percent of people with Morton?s Neuroma. If conservative treatment does not relieve your symptoms, your physician may discuss surgical treatment options with you.
Recently, an increasing number of procedures are being performed at specialist centers under radiological or ultrasound guidance. Recent studies have shown excellent results for the treatment of Morton's neuroma with ultrasound guided steroid injections, ultrasound guided sclerosing alcohol injections, ultrasound guided radiofrequency ablation and ultrasound guided cryo-ablation.