Morton’s Neuroma

General Information

Description:

  • Perineurofibrosis of common digital nerve
  • Paroxysmal neuralgia affecting web spaces of toes, typically second and third
  • Different from Morton’s syndrome – metatarsalgia caused by short first metatarsal bone


Also called:

  • Morton’s neuroma
  • Interdigital neuroma
  • Intermetatarsal neuroma
  • Plantar neuroma
  • Plantar intermetatarsal neuroma


Organs involved:

  • Second and third common digital branches of medial plantar nerve are most frequent sites


Who is most affected:

  • More prevalent in women < 50 years old


Incidence/Prevalence:

  • Most common cause of foot neuralgia


Causes and Risk Factors

Causes:

  • Repeated trauma of metatarsal heads considered primary cause, often related to overly tight shoe or high heels
  • Lateral compression between metatarsal heads is an unproven theory of development of neuroma
  • Other possible causes
    • Flattening of the medial arch
    • Ischemic changes within interdigital nerve
    • Bunion formation


Pathogenesis:

  • Perineural fibromas
  • Third branch of plantar nerve thought to be more susceptible to trauma due to its larger diameter


Likely risk factors:

  • Runners or athletes experiencing repetitive pounding of feet
  • Tight or high-heeled shoes


Complications and Associated Conditions

Associated conditions:

  • Ganglion or synovial cyst
  • Occurs bilaterally in 15% patients


History and Physical

History:

Chief concern (CC):

  • Foot pain in 2nd or 3rd web space with radiation to toes(2)

History of present illness (HPI):

  • Ask about
    • Duration of symptoms
    • Location of pain
    • Any specific trauma, strain or overuse
    • What types of shoes are worn, any recent change
    • Any paresthesia or weakness – sometimes shooting pain or numbness in interspace distal to neuroma
    • Precipitating and relieving activities – relief obtained more by removing shoe than getting off foot


Physical:

Extremities:

  • Note sites of tenderness – forefoot, sole, between metatarsal heads 3 and 4 (or 2 and 3)
    • If sole of foot
      • Metatarsalgia – Freibergs’ disease in preteen or adolescent
      • Morton neuroma – between metatarsal heads 3 and 4 (or 2 and 3), pain on lateral compression, also tenderness at web space of toes
    • If dorsum of foot
      • Metatarsal stress fracture – localized dorsally over metatarsal shafts
      • Extensor tendonitis – pain precipitated by passive stretch and resistance against involved tendon
  • Web space compression test
    • Squeeze metatarsal heads together with 1 hand
    • Simultaneously compress involved web space with thumb and index finger of other hand
    • May induce severe pain
    • Mulder’s sign is production of painful and palpable click during web space compression