Morton's neuroma--pathogenesis and ultrastructure.

In an attempt to clarify the pathogenesis of Morton's neuroma, 106 documented cases were analyzed by multiple staining techniques and electron microscopy. The lesion was found to consist of a progressive fibrosis which enveloped and disrupted nerves and arteries. No evidence of a nerve proliferation nor of a specific inflammatory process was encountered. Based on these observations, it is concluded that repeated trauma in the connective tissue elements, including nerves and arteries in the interdigital clefts, lead to a reactive overgrowth of connective tissue (scarring) that disrupts the nerves and the arteries. Sclerosis of the arteries and the narrowing of their lumen contributes to ischemia and further nerve atrophy. The nerves and arteries caught in this reactive scar become more sensitive to pressure and cause characteristic pain.