Morton's Neuroma

Morton neuroma refers to the enlargement of the nerve usually on the 3rd interspace – the nerve flanked by the third and fourth toes.

This area is particularly prone because this is where a section of the lateral plantar nerve touches a section of the nerve of the medial plantar. Combined, these two nerves are usually larger (diameter-wise) than the nerves leading to the rest of the toes.

The nerve is also on the subcutaneous tissue, on top of the foot’s fat pad near a vein and an artery. Right over the nerve is the deep transverse metatarsal ligament which clutches the metatarsal bones and builds the nerve compartment’s ceiling. As you walk, the ground shoves the inflamed nerve up, and the deep transverse metatarsal ligament shoves down, causing compression.

Signs and Symptoms

Patients suffering from Morton neuroma usually experience pain (usually localized) in the 3rd and 4th toe interspace. For some patients, the pain is sharp, and for others it is dull. The pain is usually made worse by shoes and by walking, and is alleviated when the foot is not supporting any weight.

Morton's Neuroma Causes and Risk Factors

There is still no consensus on why the nerve becomes enlarged to cause Morton neuroma.

Flat feet seem to be a contributing factor. The nerve of a flat foot tends to abnormally pull in the direction of the middle, causing irritation and in some cases, nerve enlargement. Women seem to be more prone to Morton neuroma, giving way to the theory that confining high-heeled shoes cause the condition. The heels and narrow toe boxes of women’s shoes tend to transfer much of the body weight to the front part of the foot and compress toes, possibly squeezing the nerve section on all sides.

Tests & Diagnosis

Morton neuroma is diagnosed by palpating the area and pressing the toes from one side to another in order to elicit pain. The doctor may also press into the foot’s affected interspace to stroke the neuroma. The doctor usually elicits Mulder's sign – an audible click when the doctor holds the patient's first three metatarsal heads with one hand and the last two metatarsal heads in the other and slightly pushes half of the foot up and half the foot down.

The doctor will likely request an x-ray to rule out fractures and arthritis. An MRI scan may also be requested to rule out tumors and determine the size of the neuroma. The MRI also helps the doctor decide if a Morton's neuroma surgery is necessary or not.

Neuroma Treatment Options

Pads and tapes help take the weight off the neuroma. Patients with flat feet are usually advised to use arch supports. A simple switch to shoes with bigger toe boxes plus low heels can already significantly alleviate pain.

Local anesthetic may also be injected to reduce pain and swelling. When the pain decreases after 14 days, the Morton’s neuroma is most likely small – custom orthotics are often enough to relieve it. If the condition does not improve, however, then Morton's neuroma surgery may be needed.

There are two types of surgical procedures for treating Morton neuroma – the dorsal and the plantar approach.

Dorsal Surgery

During a dorsal surgery, the doctor makes an incision on the upper part of the foot – not the part that bears the weight – so that the patient can walk shortly after surgery. The deep transverse metatarsal ligament is cut. A dorsal approach may cause forefoot instability, however.

Plantar Surgery

During a plantar surgery, on the hand, the doctor makes the incision on the sole, forcing the patient to be on crutches for around 21 days after surgery. The plantar approach may be inconvenient, but it does have one big advantage – the incision makes the neuroma accessible and easily resected.

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