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It is sometimes referred to as an inter-metatarsal neuroma, where inter-metatarsal describes its location (in the ball of the foot between the metatarsal bones, extending from the toes to mid-foot). Neuromas may also occur in other locations in the foot. The thickening or enlargement of the nerve that defines a neuroma is the result of nerve compression and irritation. This compression creates a swelling, eventually leading to permanent nerve damage as a serious consequence of Morton’s neuroma.
What is Morton’s neuroma?
Morton's neuroma is an enlarged nerve that usually occurs in the third inter-space. This inter-space is between the third and fourth toe. Problems often develop in this area because a part of the lateral plantar nerve combines with a part of the medial plantar nerve here. When the two nerves combine, they are typically larger in diameter than nerves going to the other toes. Moreover, the nerve lies in subcutaneous tissue, just above the fat pad of the foot, close to arteries and veins. Above the nerve, there is a structure called the deep transverse metatarsal ligament. This ligament is very strong, holding the metatarsal bones together. This ligament also 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, which causes compression in a confined space. The reason the nerve enlarges has not been determined yet. Flat feet can cause the nerve to be pulled toward the middle more than normal. This could lead to irritation and possibly enlargement of the nerve. The syndrome is more common in women than men, possibly because women wear confining shoes more often.
High heels cause more weight to be transferred to the front of the foot, and tight toe boxes create lateral compression. Because of this, more force is being applied in the area and the nerve compartment is squeezed from all sides. Under such conditions, even a minimal enlargement in the nerve can elicit pain as one of the symptoms.
Signs and symptoms of Morton’s neuroma
The most common symptom of Morton's neuroma is a localized pain in the inter-space between the third and fourth toe. The pain could be sharp or dull, and is worsened by wearing shoes and by walking. However, the pain is usually less severe when the foot is not bearing weight. Patient diagnosed with Morton’s neuroma will probably have one or more of these symptoms where the nerve damage occurs. These symptoms are tingling, burning, or numbness, pain, and a feeling that something is inside the ball of the foot, or that there is a rise in the shoe or a sock is bunched up. The progression of a Morton’s neuroma often follows the same pattern. The symptoms begin gradually, and at first they occur only occasionally, when wearing narrow-toed shoes or performing certain aggravating activities. Symptoms may be suppressed temporarily by massaging the foot or by avoiding aggravating shoes or activities. Over time the symptoms progressively worsen and may persist for several days or weeks even when you avoid walking. The symptoms become more intense as the neuroma enlarges and the temporary changes in nerve become permanent.