Interdigital neuroma (Morton?s Neuroma) of the foot includes common, paroxysmal, neuralgia affecting the web spaces of the toes. It involves entrapment neuropathy (nerve compression) of the common digital nerve below and between the metatarsal heads, typically between the third and the fourth metatarsal heads. The pain is most commonly felt between the third and fourth toes but can also occur in the area between the second and third toes.
When a nerve is pinched between bones, the result is swelling of the nerve. It is this swelling which is referred to as a Neuroma. When the condition occurs in the foot, it is known as a Morton?s Neuroma. Morton?s Neuroma is technically not a tumor. Rather, it is a thickening of the tissue that surrounds the digital nerves leading to the toes. These nerves allow for physical sensation on the skin of the toes. The region of inflammation is found where the digital nerve passes under the ligament connecting the toe bones (metatarsals) in the forefoot. Morton?s Neuroma commonly develops between the third and fourth toes, generally as a result of ongoing irritation, trauma or excessive pressure. In some cases, the second and third toes are involved. Morton?s Neuroma is confined to one foot in most cases, though it can occur in both, particularly in athletes such as runners.
People with Morton's neuroma usually complain of pain that can start in the ball of the foot and shoot into the affected toes. However, some people just have toe pain. There may also be burning and tingling of the toes. The symptoms are usually felt up the sides of the space between two toes. For example, if the nerve between the third and fourth long bones (metatarsals) of the right foot is affected, the symptoms will usually be felt up the right-hand side of the fourth toe and up the left-hand side of the third toe. Some people describe the pain that they feel as being like walking on a stone or a marble. Symptoms can be made worse if you wear high-heeled shoes. The pain is relieved by taking your shoe off, resting your foot and massaging the area. You may also experience some numbness between the affected toes. Your affected toes may also appear to be spread apart, which doctors refer to as the 'V sign'. The symptoms can vary and may come and go over a number of years. For example, some people may experience two attacks of pain in a week and then nothing for a year. Others may have regular and persistent (chronic) pain.
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
Treaments may include wearing wider shoes to reduce the squeezing force on the foot. Adding a specially made padding to shoes to offload the pressure on the ball of the foot (called a metatarsal dome) Addressing the foot and lower limb biomechanics. This involves looking at foot stability and if needed prescribing an orthotic device to correct your foot position. Anesthetic & Cortisone injections. This is done when the above treatments are insufficient. The trauma is sometimes so great that conservative treatment cannot control the inflammation or cause of the pain. A series of injections are performed to control the inflammation or to temporarily settle the nerve. An ultrasound and cortisone injection can be prescribed by your podiatrist.
Patients are commonly offered surgery known as neurectomy, which involves removing the affected piece of nerve tissue. Postoperative scar tissue formation (known as stump neuroma) can occur in approximately 20%-30% of cases, causing a return of neuroma symptoms. Neurectomy can be performed using one of two general methods. Making the incision from the dorsal side (the top of the foot) is the more common method but requires cutting the deep transverse metatarsal ligament that connects the 3rd and 4th metatarsals in order to access the nerve beneath it. This results in exaggerated postoperative splaying of the 3rd and 4th digits (toes) due to the loss of the supporting ligamentous structure. This has aesthetic concerns for some patients and possible though unquantified long-term implications for foot structure and health. Alternatively, making the incision from the ventral side (the sole of the foot) allows more direct access to the affected nerve without cutting other structures. However, this approach requires a greater post-operative recovery time where the patient must avoid weight bearing on the affected foot because the ventral aspect of the foot is more highly enervated and impacted by pressure when standing. It also has an increased risk that scar tissue will form in a location that causes ongoing pain.
The best way to prevent a neuroma is by avoiding the things that cause them. Review your risk factors. If relatives have had similar problems, or if you know that you pronate or have any problem with the mechanics of your foot, talk with a podiatric physician about the correct types of shoes and/or orthoses for you. If you are not sure whether you have such a problem, the podiatric professional can analyze your foot, your stride and the wear pattern of your shoes, and give you an honest evaluation. Remember, though, that sometimes neuromas, like other conditions, can develop for no discernible reason. With this in mind, be good to your feet, and be aware of any changes or problems. Don?t wait to report them.