The nerves located on the bottom of the foot between the metatarsal heads (the bone of the toe closest to the foot) supply feeling, or sensation, to the toes. One of these nerves may become irritated by the ligament located above it, causing it to become thickened and painful. Generally this problem occurs most often between the third and fourth toes, but it can occur between the second and third toes as well. It is uncommon for a neuroma to be located between the first and second or fourth and fifth metatarsals. Rarely is there more than one neuroma in a foot.
Morton's neuroma is an inflammation caused by a buildup of fibrous tissue on the outer coating of nerves. This fibrous buildup is a reaction to the irritation resulting from nearby bones and ligaments rubbing against the nerves. Irritation can be caused by wearing shoes that are too tight, wearing shoes that place the foot in an awkward position, such as high heels, a foot that is mechanically unstable, repetitive trauma to the foot such as from sports activities like tennis, basketball, and running. Trauma to the foot caused by an injury such as a sprain or fracture. It is unusual for more than one Morton's neuroma to occur on one foot at the same time. It is rare for Morton's neuroma to occur on both feet at the same time.
Symptoms of interdigital neuroma typically manifest as a sharp, burning or tingling sensation in the forefoot. The pain radiates toward the lesser toes and is aggravated by shoe wear. The pain is relieved when the shoe is removed and the forefoot is massaged. Sometimes the symptoms involve specific toes.
The diagnosis of interdigital neuroma is usually made by physical examination and review of the patient's medical history.MRI ad High Definition Ultrasound examination may be useful to confirm the diagnoses however they may still not be 100% reliable. The commonest reason for this is de to natural substances present in between the metatarsal heads and between the fat pad and the intermetatarsal ligament. These natural substances i.e. bursa, fat, capsular thickening and even bony growths, can all be a factor in the impingement process and may need to be surgically cleared.
Non Surgical Treatment
The first line of treatment is to try modifying footwear. Often simply wearing broader fitting shoes can reduce pressure on the neuroma and so reduce pain. Orthotic inserts can also help as they can again help reduce pressure on certain parts of the foot. Padding and taping the toe area is another option. In some cases a steroid injection into the foot may be suggested. This can be done as a day case without the need for anaesthesia and helps reduce inflation of the nerve. It can halt the pain in round 70 % of cases. Sometimes a combination of alcohol and local anaesthesia may be injected as this helps reduce pain.
About one person in four will not require any surgery for Morton's neuroma and their symptoms can be controlled with footwear modification and steroid/local anaesthetic injections. Of those who choose to have surgery, about three out of four will have good results with relief of their symptoms. Recurrent or persisting (chronic) symptoms can occur after surgery. Sometimes, decompression of the nerve may have been incomplete or the nerve may just remain 'irritable'. In those who have had cutting out (resection) of the nerve (neurectomy), a recurrent or 'stump' neuroma may develop in any nerve tissue that was left behind. This can sometimes be more painful than the original condition.