What Is Morton's Neuroma? What Causes Morton's Neuroma?

Morton's neuroma, also called Morton's metatarsalgia, Morton's disease, Morton's neuralgia, Morton metatarsalgia, Morton nerve entrapment, plantar neuroma, or intermetatarsal neuroma is a benign (non-cancerous) growth of nerve tissue (neuroma) that develops in the foot, usually between the third and fourth toes (an intermetatarsal plantar nerve, most commonly of the third and fourth intermetatarsal spaces). It is a common, painful condition.

Put simply - Morton's neuroma is a swollen (inflamed) nerve in the ball of the foot, commonly between the base of the second and third toes.

Patients experience numbness and pain in the affected area, which is relieved by removing footwear and/or massaging the foot.

A neuroma is a tumor that arises in nerve cells - a benign growth of nerve tissue that can develop in various parts of the body. In Morton's neuroma the tissue around one of the nerves leading to the toes thickens, causing a sharp, burning pain in the ball of the foot. A sharp severe pain, often described as a red hot needle may come on suddenly while walking. There may also be numbness, burning and stinging in the toes.

Although it is labeled a neuroma, many say it is not a true tumor, but rather a perineural fibroma (fibrous tissue formation around nerve tissue).

Morton's neuroma may be the result of irritation, pressure or injury. In some cases its cause is unknown. In the majority of cases only one nerve is affected. Having both feet affected is extremely rare. A high percentage of patients with Morton's neuroma are women who wear high-heeled or narrow shoes.

Patients with Morton's neuroma may need to change their footwear, take painkillers or steroid injections, while others may require surgery to either remove the affected nerve or release the pressure on it.

According to Medilexicon's medical dictionary:

Morton neuroma is "a painful, tender focal mass lesion on one of the plantar interdigital nerves of the foot, most often that which is situated between the third and fourth metatarsal bones; attributed to either compression of the nerve between the heads of the adjacent metacarpal bones, or traction being placed on the nerve as it crosses the anterior edge of the deep transverse metatarsal ligament."

What are the signs and symptoms of Morton's neuroma?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

Outward signs of Morton's neuroma, such as a lump, are extremely rare.

Morton's neuroma signs and symptoms, which usually occur unexpectedly and tend to worsen over time, include:

• Pain on weight bearing (while walking) - a shooting pain affecting the contiguous halves of two toes, which may be felt after only a short time (of weight bearing). Sometimes there may be a dull pain rather than a sharp one. Most commonly, pain is felt between the third and fourth toes. Typically, a patient will suddenly experience pain while walking and will have to stop and remove their shoe.
• Burning
• Numbness
• Parasthesia - tingling, pricking, or numbness with no apparent long-term physical effect. Commonly known as pins-and-needles.
• A sensation that something is inside the ball of the foot.

Many patients describe the sensation as a burning pain in the ball of the foot that often radiates to the toes.

Initially, the pain may become much more apparent when the person wears tight, narrow or high-heeled shoes, or engages in activities which place pressure on the foot. Eventually, symptoms may be continuous and last for days, and even weeks.

MRI (magnetic resonance imaging) scans have revealed Morton's neuroma lesions in patients who had no symptoms at all.

Symptoms can become so disrupting that many affected individuals become anxious about walking, or even placing their foot on the ground.

What are the causes of Morton's neuroma?

Experts are not sure what exactly causes Morton's neuroma. It seems to develop as a result of irritation, pressure or injury to one of the digital nerves that lead to the toes, which triggers a body response, resulting in thickened nerve tissue (neuroma).

• Feet conditions/situations that can cause the bones to rub against a nerve include:
  
  
  • High-heeled shoes - especially those over 2 inches (5cm), or a pointed or tight toe box which squash the toes together. This is probably why the condition is much more common in females than in males.
  • High-arched foot - people whose feet have high arches are much more likely to suffer from Morton's neuroma than others.
  • Flat feet - the arch of the foot collapses. The entire sole of the foot comes into complete or near-complete contact with the ground.
  • A bunion - a localized painful swelling at the base of the big toe, which enlarges the joint.
  • Hammer toe - a deformity of the proximal interphalangeal joint of the second, third, or fourth toe causing it to be permanently bent.
• Some high-impact sporting activities - including running, karate, and court sports. Any sport that places undue pressure on the feet.
• Injuries - an injury or other type of trauma to the foot may lead to a neuroma.

Diagnosing Morton's neuroma

A GP (general practitioner, primary care physician) or a podiatrist (foot specialist doctor) will ask the patient to describe the pain as well as its intensity, when symptoms started, what types of shoes are worn, as well as some questions about their job, lifestyle and hobbies.

The doctor will then examine the foot and try to locate the affected nerve. This may involve attempting to reproduce symptoms by manipulating the foot.

In order to get a detailed image of the inside of the food, one of the following scans may be ordered:

• X-ray - this is a type of high-energy radiation. In low doses they are used to diagnose diseases and condition by making pictures of the inside of the body. In higher doses they are used to treat cancer. This procedure is non-invasive and painless.
• Ultrasound scan - high frequency sound waves are pointed at a specific part of the body, which in this case is the foot. The ultrasound waves bounce of tissues; their echoes are then converted into a picture, called a sonogram. This allows the doctor to get an inside view of the foot. This procedure is non-invasive and painless.
• MRI (magnetic resonance imagining) - a device that uses a magnetic field and radio waves to create detailed images of the body. Unlike CT scanning or general x-ray studies, no ionizing radiation is involved with an MRI. This procedure is non-invasive and painless.

The doctor will have to rule out other conditions which may have similar symptoms, including capsulitis, bursitis, or Freiberg's disease.

What are the treatment options for Morton's neuroma?

Treatment for Morton's neuroma may depend on several factors, including the severity of symptoms and how long they have been present. The earlier on the condition is diagnosed, the less likely surgery is required.

Doctors will usually recommend self-help measures first. These may include:

• Resting the foot
• Massaging the foot and affected toes
• Using an ice pack on the affected area (skin should not be directly exposed to ice, the ice should be in a container or wrapped in something)
• Changing footwear - wearing wide-toed shoes, or flat (non high-heeled) shoes
• Trying arch supports (orthotic devices). A type of padding that supports the arch of the foot, removing pressure from the nerve. The doctor may recommend a custom-made, individually designed shoe-insert, molded to fit the contours of the patient's foot. There are several OTC (over the counter, non-prescription) metatarsal pads or bars available which can be placed over the neuroma.
• Taking OTC (over-the-counter, non-prescription) painkilling medications
• Modifying activities - avoiding activities which put repetitive pressure on the neuroma until the condition improves.
• Bodyweight management - if the patient is obese the doctor may advise him/her to lose weight. A significant number of obese patients with foot problems, such as flat feet, who successfully lose weight experience considerable improvement of symptoms.

If symptoms are severe or persistent and self-help measures did not help, the doctor may recommend:

• Corticosteroid injections - a steroid medication that reduces inflammation and pain is injected into the area of the neuroma. Only a limited number of injections are advised, otherwise the risk of undesirable side effects increases, including hypertension (high blood pressure) and weight gain.
• Alcohol sclerosing injections - studies have shown that alcohol injections reduce the size of Morton's neuromas as well as alleviating pain. This is a fairly new therapy and may not be available everywhere. The doctor injects alcohol in the area of the neuroma to help sclerose (harden) the nerve and relieve pain. Injections are typically administered every 7 to 10 days. For maximum relief 4 to 7 injections are usually needed.
• Surgery - if other therapies have not worked it may be necessary to perform surgery. As surgery may result in permanent numbness in the affected toe, doctors ten to use this procedure as a last resort. However, in most cases surgery is extremely effective.
  
  The patient usually receives a local anesthetic.
  
  Surgery involves either removing the nerve, or removing the pressure on the nerve. Two surgical approaches are possible:
  
  
  • The dorsal approach - the surgeon makes an incision on the top of the foot, allowing the patient to walk soon after surgery, because the stitches are not on the weight-bearing side of the foot.
  • The plantar approach - the surgeon makes an incision on the sole of the foot. In most cases the patient will be in crutches for about three weeks. The resulting scar may make walking uncomfortable. However, with this approach the neuroma can be reached easily and resected without cutting any structures.