what causes morton neuroma?

1.

Elsevier ClinicalKey Derived Clinical Overview

• While the exact etiology of Morton neuroma is uncertain, most histologic studies show evidence of hyperplasia within the nerve. • The neuroma is further considered to be an entrapment neuropathy of the affected common digital plantar nerve (Fig. E1) between adjacent metatarsal heads or by the transverse metatarsal ligament. • The common plantar digital nerves are branches of the medial and lateral plantar nerve that course distally to supply the digits of the foot, passing just beneath the deep transverse intermetatarsal ligament. Within the third intermetatarsal space, a communicating branch of the medial plantar nerve often joins with a communicating branch of the lateral plantar nerve to supply the third and fourth digits. This anatomic variation results in a thicker nerve that is more prone to trauma between the constrictive metatarsal heads, a reason often cited to explain the prevalence of Morton neuroma specifically within the third interspace. • The deep transverse intermetatarsal ligament may also be implicated in the cause of a neuroma. If it is thickened or has aberrant bands, it may cause compression of the affected nerve. • Soft tissue masses such as a plantar lipoma may also cause compression of the nerve against the ligament, leading to the formation of a neuroma. • Histologic examination of resected Morton neuroma exhibits increased neural width, demyelination, intraneural fibrosis, and thickened endoneurial capillaries. FIG. E1On the plantar surface of the foot, the interdigital nerve is compressed below the transverse metatarsal ligament and not between the metatarsal heads (plantar view).From Hochberg MC:Rheumatology,ed 7, Philadelphia, 2019, Elsevier.

2.

Biundo, Joseph J., Canoso, Juan J. (2024). In Goldman-Cecil Medicine (pp. 1742). DOI: 10.1016/B978-0-323-93038-3.00242-2

Morton neuroma (Fig. 242-8) is a prominent cause of forefoot pain and paresthesia in individuals who wear shoes that are too narrow for the width of their metatarsal arches and high heels that drive the forefeet into those limited spaces. The compressed nerve, surrounded by reactive fibrous tissue, supplies the opposing halves of two contiguous toes, generally the third and the fourth. Multiple nerves may be involved.Typically, symptoms do not appear wearing sandals.

3.

Mak MS, Chowdhury R, Johnson R. Clinical Radiology. 2021;76(3):235.e15-235.e23. doi:10.1016/j.crad.2020.10.006.

Publish date: March 1, 2021.

Morton's neuroma is a commonly encountered cause of forefoot pain, which may limit weight-bearing activities and footwear choices. Although the aetiology and pathomechanism of this condition is controversial, the histological endpoint is well established as benign perineural fibrosis of a common plantar digital nerve, typically within the third intermetatarsal space. The diagnosis of Morton's neuroma is mainly based on characteristic symptoms and clinical findings, but may be confirmed by ultrasonography. Although ultrasound is a highly accurate diagnostic tool for Morton's neuroma, it is subject to interoperator variability due to differences in technique and level of experience. In this paper, the authors review the anatomy of the common plantar digital nerves and surrounding structures in the forefoot, which are deemed relevant to the understanding of Morton's neuroma, especially from a sonographic point of view. Several theories of the pathomechanism of Morton's neuroma are briefly discussed. The main purpose of this article is to illustrate the ultrasound techniques for evaluating Morton's neuroma and performing ultrasound-guided corticosteroid injections.