Morton's Neuroma
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).
Cause
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.
Symptoms
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
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
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
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.
Complications
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.