Morton's neuroma is an enlarged nerve but there is no tumour formation in morton's neuroma. Dr Morton first described this condition in 1876 and since then it has being called Morton's metatarsalgia or interdigital neuroma.
It usually occurs in between the third and fourth toes. Problems often develop in this area because part of the lateral plantar nerve combines with part of the medial plantar nerve in this particular area of the foot. When the two nerves combine, they become larger in diameter. Above the nerve is a structure called the deep transverse metatarsal ligament. This ligament 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 repetitive and chronic compression, stress and irritation of the plantar nerve in a confined space and.
The other anatomical factor is due narrow spaces between the metatarsal second and third, and the third and fourth. This means that the nerves that run between these metatarsals are more likely to be compressed and irritated.
The reason the nerve enlarges has not been determined. Flatfeet can cause the nerve to be pulled toward the middle (medially) more than normal, which can cause irritation and possibly enlargement of the nerve. The syndrome is more common in women than men, possibly because women wear confining shoes more often. High heels cause more weight to be transferred to the front of the foot and tight toe boxes create lateral compression. As a result, there is more force being applied in the area and the nerve compartment is squeezed on all sides. Under such conditions, even a minimal enlargement in the nerve can elicit pain.
Specialised consultation and care for neuroma at Temple Clinic in Ealing, West London