First described in 1876 by Dr. William J. Morton, a Viennese physician, Morton's neuroma is a very painful condition felt at the front of the foot, often extending to the toes. Generally, the word "neuroma" refers to any swelling of a nerve. A Morton's neuroma is excessive tissue formation around sensory nerves at the base of the second and third, or third and fourth toes. Fibrous tissue forms due to nerve irritation from ligaments exerting pressure, causing swelling, inflammation, pain, and numbness in part of a toe or toes. These ligaments compress the nerve, and the body's natural reaction to the compression is to form excess tissue. However, the excess tissue results in more irritation and compression to the nerve, making the condition and pain worse.
Pain from Morton's neuroma is primarily located on the bottom of the ball of the foot. The pain is made worse by walking, especially while wearing shoes with a narrow forefoot. It is caused by a swelling of a small nerve that supplies feeling to the third and fourth toe. It can feel like a numbness combined with radiation or a stinging sensation in the two toes. At times patients will describe feeling like their sock is wadded up under the bottom of the toes. Often the pain is easier to describe than to tell exactly where it is coming from. Sometimes patients describe sitting down, removing their shoe and rubbing the forefoot to get the pain to go away.
Diagnosis is made by first taking a careful history and physical exam. The injured nerve does not show up well on either MRI or CT scans. X-rays generally appear normal, but often there is swelling that can be seen around the nerve on ultrasound imaging. Diagnosis is confirmed by the podiatrist pushing on the area where the nerve is swollen and then squeezing the forefoot from side to side. The nerve will make a "click" that both the patient and doctor can feel.
A custom molded orthotic made by your podiatrist, and therefore covered by most medical insurance, can be outfitted with a slight metatarsal raise just behind the ball of the foot. This well-placed raise spreads out the bones on both sides of the nerve, thereby shielding it from pressure. Because the neuroma is simply a collection of scar tissue within the nerve, it may go away in about a year if the orthotic is worn 90% of the time. The scar tissue within the nerve remodels and gets smaller when there is no further pressure on it.
A cortisone shot can be tremendously effective once the proper orthotics are in place. The cortisone works by decreasing the size of the nerve so that it doesn't get pinched by the adjacent bones. Ideally, the area is anesthetized and ultrasound imaging is used to directly visualize the injection of a small amount of cortisone into the nerve. Sometimes a cortisone shot is also effective as a stand-alone treatment.
Rarely, when the nerve does not respond to conservative treatment or when the patient just wants to get it over with, the nerve is treated with surgical excision. Patients have reported a loss of sensation about 20 percent of the time following excision of the nerve. The nerve grows back following excision about 10 percent of the time. The anesthesiologist is usually present for the procedure.
Posted by Mark A. Kuzel, DPM, FACFAS on September 5, 2010