Morton’s neuroma is one cause of metatarsalgia (pain in the forefoot). It was described by Thomas Morton in 1876. It is due to inflammation of a nerve in the foot. This inflammation is caused by entrapment of the nerve under the metatarsal heads.
“Neuroma” means nerve tumour (tumour in this case means simply enlargement of the nerve and not malignancy).
The cause of the nerve enlargement is repeated injury. The nerve becomes trapped under the metatarsal heads when standing and walking. This most often occurs in shoes with high heels of thin, hard soles, but can occur in any walking or standing situation. It usually occurs between the third and fourth toes.
The symptoms of Morton’s neuroma are pain and numbness in a specific spot on the ball of the foot, sometimes radiating to the toes. At times the pain may be absent and at other times, severe enough to cause the individual to stop and take off the shoe. It may feel like a stone or marble under the foot, moving around and sometimes causing a sharp ‘snap’ to be felt. The examining physician can sometimes feel this by pressing on the foot. Testing with pin may reveal numbness in the toes.
Diagnosis may be difficult, especially at first. Several examinations may be necessary. The condition tends to get worse with time. With repeated injury, the nerve becomes larger and it is more easily injured.
Treatment is first to modify the shoes. A pad in the shoe and an extra-wide, soft shoe will help. A cortisone injection around the nerve may help reduce swelling and inflammation. This may also help localize the problem.
Surgery to remove the neuroma can be done when necessary. It is successful around 90% of the time. Since a nerve is removed there is numbness in the toes and in the ball of the foot afterwards. This is not usually a problem and becomes less so with time.
Persisting pain : Persisting pain may be due to irritation at the cut end of the nerve – a stump neuroma. This may require additional surgery for those who do not get relief.
Infection : Infection is another possible complication. The foot is prone to post-operative swelling and bleeding and this can lead to infection. An adequate period of rest and elevation after surgery is needed to prevent this complication.