Morton’s neuroma (also known as Morton’s metatarsalgia, plantar or interdigital neuroma) is a perineural fibrosis and nerve degeneration of an intermetatarsal plantar nerve that causes pain in the ball of the foot in the area between the 3rd and 4th metatarsals (third webspace) usually.
The condition may affect one or both feet. Morton’s neuroma is characterized by the pain and numbness in the ball of the foot (metatarsalgia). Commonly interdigital neuroma is found between the 3rd and 4th toes in so-called third webspace, although it may also occur between the second and third metatarsals (second webspace) and, rarely, between the first and second (first webspace) or fourth and fifth (fourth webspace) metatarsals (long bones of the foot).
Causes and risk factors
Neuroma is an abnormal growth arising from the nerve tissue.
However, Morton’s neuroma in not a true tumor rather perineural fibrosis and nerve degeneration (thickening) due to excessive pressure over the nerve.
Morton’s neuroma commonly affects middle-aged women, probably because of the high-heeled shoes they wear. Uncomfortable bad fitting shoes also contribute to Runners may also have foot pain due to the increased pressure on the foot. People with abnormal bones of the foot (foot deformities) such as hammertoes, flat feet, etc.
The first symptom of interdigital neuroma is usually a tingling sensation in the ball of the foot. However, Morton’s neuroma is characterized by the pain that occur after a short-time tension. The pain may be shooting and affect the halves of 2 toes or feel like if the person is walking on blades or twisted bit of sock or has a pebble or stone in his/her shoe. The other symptoms may include paresthesia (abnormal sensation: tingling, tickling, pricking of a person’s skin without any physical cause), burning and numbness. Usually the pain is episodic. Sometimes the episodes occur twice a week and then disappear for a year, although as the disease progresses the attacks become more frequent.
To detect interdigital neuromas the metatarsal squeeze test is used. The foot is grasped at the metatarsal heads and then squeezed to compress them together. This compression between the metatarsal heads may produce a painful click (a Mulder sign).
Nerve irritation may be demonstrated by Tinel’s sign. When a doctor tape lightly an irritated nerve affected person senses tingling of needles and pins in the foot.
When the pain is atypical or the surgery was not effective to verify Morton’s neuroma another method – diagnostic injection is performed. In the third web of the foot a local anesthetic for example lidocaine is injected. If after the injection the pain relieves the diagnosis is confirmed. This method is considered to be the gold standard in the diagnosis of Morton’s neurome, because helps to evaluate the diagnosis with the highest likelihood.
An ultrasound examination is helpful to identify Morton’s neuroma. MRI is not necessary, although this examination is the most sensitive method to detect the neuroma.
Related: Trench foot
To decide which treatment will be the most effective for the affected person. The intensity of the symptoms and history of the disease should be estimated.
The first line therapy includes:
- Resting and massaging of the foot;
- Wearing comfortable and broad-toed shoes;
- Using orthotic devices;
- Physical therapy to strengthen the muscles of the foot;
- Dietary restrictions and weight management;
- Administration of over-the-counter medications;
The best treatment is Morton’s neuroma is the administration a nerve block with the help of corticosteroids; these injections reduce inflammation and pain.
Alcohol sclerosing injections are used to alleviate the pain. Injections are performed every 7-10 days. Typically 7 injections are enough to get rid of the pain.
If conservative therapy is not effective after 9-12 months of treatment surgery should be considered. Decompression surgery helps relieve the pressure on the intermetatarseal nerve by cutting the ligaments of the foot.
Surgical removal (neurectomy) via dorsal or plantar approach of the nerve is performed if other treatments are unable to alleviate the pain.
Alternative surgery is cryogenic neuroablation – the destruction of the nerve by the low temperatures.