Morton’s neuroma is an enlarged nerve that usually occurs in the third interspace, which is between the third and fourth toes. To understand Morton’s neuroma further, it may be helpful to look at the anatomy of the foot. Problems often develop in the third interspace because part of the lateral plantar nerve combines with part of the medial plantar nerve here. When the two nerves combine, they are typically larger in diameter than those going to the other toes. Also, the nerve lies in subcutaneous tissue, just above the fat pad of the foot, close to an artery and vein. Above the nerve is a structure called the deep transverse metatarsal ligament. This ligament is very strong, holds the metatarsal bones together, and 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. This causes compression in a confined space.
A Morton?s Neuroma are a result of complex biomechanical changes that occur in your feet. There are a number of theories as to the exact cause of the scarring and thickening, but it basically boils down to overload of the tissue structure. The body lays down scar tissue to try to protect the overloaded structure. Tight-fitting shoes may exacerbate a Morton?s Neuroma. Shoes such as high heels and shoes with tight toe boxes (eg womens fashion shoes and cowboy boots) are particularly damaging to the toes. These shoes have a sloping foot bed and a narrow toe box. The slope causes the front of the foot to bear your weight. The angle of the toe box then squeezes your toes together. Footwear is not the only cause of a Morton?s Neuroma. Injuries to the foot can also be a factor in developing the condition by changing your foot biomechanics. Poor foot arch control leading to flat feet or foot overpronation does make you biomechanically susceptible to a neuroma.
Symptoms include tingling in the space between the third and fourth toes, toe cramping, a sharp, shooting, or burning pain in the ball of the foot and sometimes toes, pain that increases when wearing shoes or pressing on the area, pain that gets worse over time. In rare cases, nerve pain occurs in the space between the second and third toes. This is not a common form of Morton neuroma, but treatment is similar.
The exact cause of Mortons neuroma can often vary between patients. An accurate diagnosis must be carefully made by the podiatrist through thorough history taking and direct questioning to ensure all possible causes are addressed. The podiatrist will also gather further information about the cause through a hands on assessment where they will try to reproduce your symptoms. A biomechanical and gait analysis will also be performed to assess whether poor foot alignment and function has contributed to your neuroma.
Non Surgical Treatment
Most non-operative treatment is usually successful, although it can take a while to figure out what combination of non-operative treatment works best for each individual patient. Non-operative treatment may include the use of comfort shoe wear. The use of a metatarsal pad to decrease the load through the involved area of the plantar forefoot. A period of activity modification to decrease or eliminate activities, which maybe exacerbating the patient?s symptoms. For example, avoiding long periods of standing or other activities that result in significant repetitive loading to the forefoot can be very helpful. Wearing high heels should be avoided. Local corticosteroid injections can help decrease inflammation associated with the nerve. However, this does not necessarily address the underlying loading forces that maybe causing the injury to the nerve in the first place. It has been proposed that an alcohol injection in and around the nerve will cause a controlled death to the nerve and subsequently eliminate symptoms from the nerve. In theory, this may be helpful. In practice, adequate prospective studies have not demonstrated the benefit of this procedure above and beyond the other standard non-operative treatments available. In addition there is the concern that the alcohol will cause excessive scarring and death of other important structures in the area.
The ultimate success of a Morton?s neuroma treated surgically is somewhat unclear. This is likely due to the idea that in most instances a ?Morton?s neuroma? is actually more than just an isolated nerve problem but rather consitutes a metatarsalgia where other structures (such a as the MTP joints) are also problematic, not just the nerve. Therefore, addressing the nerve as well as the other components of a metatarsalgia may offer a better chance of surgical success. However, like many conditions in foot and ankle, it is ideal if this condition can be managed without surgery.