Localized Interdigital Neuritis / Morton Neuroma

Definition

• Non-neoplastic, degenerative process, usually affecting plantar and digital nerves characterized by axon and myelin loss accompanied by fibrosis

Alternate/Historical Names

• Morton’s Toe
• Morton’s metatarsalgia
• Plantar neuroma
• Morton’s node

Diagnostic Criteria

• Painful lesion of the foot, nearly always of the third metatarsal interspace
  • May rarely involve digital nerves
• Marked fibrosis of perivascular, epineurial, and perineurial tissue
  • Hyalinization and thrombosis of arterial vessels is common
• Depletion of axons within the peripheral nerve
• Elastic fibers increased at the periphery of the lesion
• Primarily affects women (80%)

Jason Karamchandani MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting : 11/13/10

Differential Diagnosis

• Neurofibroma
• Traumatic Neuroma

Neurofibroma	Localized Interdigial Neuritis (Morton Neuroma)
Can occur anywhwere	Occurs in plantar and palmar digital nerves
Proliferative lesion	Degenerative lesion
Contains bundles of collagen	Epineurial and perivascular fibrosis

Traumatic Neuroma	Localized Interdigial Neuritis (Morton Neuroma)
Can occur anywhwere	Occurs in plantar and palmar digital nerves
History of trauma or surgery	No history of prior trauma or surgery
Disorganized, microfascicular architecture	Nerve is intact
Haphazardly arranged axons	Axons decreased in number

Clinical

• Attributed to chronic, repetitive nerve trauma and ischemia
  • Frequently appears to be caused by poorly fitting shoes
• Approximately 90% of patients present with severe paroxysmal pain of the third and fourth toes
• Pain has typically been present for weeks to years
• Usually exacerbated by exercise, and relieved by rest

Lists

Tumors of Peripheral Nerves

• Granular cell tumor
• Inflammatory pseudotumor
• Localized interdigital neuroma (Morton neuroma)
• Neural fibrolipoma
• Neurofibroma
• Neuromuscular choristoma
• Neurothekeoma
• Nerve cyst
• Nerve sheath myxoma
• Malignant peripheral nerve sheath tumor
• Pacinian neuroma
• Perineurioma
• Schwannoma
• Solitary circumscribed (palisaded encapsulated} neuroma
• Traumatic neuroma
  

Bibliography

• Scheithauer BW, Woodruff JM, Erlandson RA. Tumors of the Peripheral Nervous System, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 24, 1999.
• Weiss, S.W., J.R. Goldblum, and F.M. Enzinger, Enzinger and Weiss' soft tissue tumors. 5th ed 2008, Philadelphia, PA: Mosby Elsevier
• Sternberg, S.S., S.E. Mills, and D. Carter, Sternberg's diagnostic surgical pathology. 4th ed 2004, Philadelphia: Lippincott Williams & Wilkins
• Giannini S, Bacchini P, Ceccarelli F, Vannini F. Interdigital neuroma: clinical examination and histopathologic results in 63 cases treated with excision. Foot Ankle Int. 2004 Feb;25(2):79-84.