46: Entrapment Neuropathies - Drown Flashcards Preview

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Flashcards in 46: Entrapment Neuropathies - Drown Deck (19)

peripheral n. anatomy


review LE dermatomes


review LE dermatomes


seddon's classification

neurotmesis (nerve division)

axonotmesis (lesion in continuity)

neuropraxia (transient block)



describe neurotmesis

  • most devastating n injury
  • complete disruption of n as well as associated connectie tissue
  • budding neurites unable to bridge defect
  • requires surgical intervention


describe axonotmesis

  • axonal disruption
  • supportive connective tissue maintained
  • can be due to: prolonged compression, traction, ischemia, toxins
  • distal: wallerian degeneration/distal axon degradation
  • proximal: axon and n cell body convert from NT production to axonal regeneration
  • as distance from site of lesion to end organ increases, functional recovery diminishes


describe neuropraxia

  • disruption of myelin sheath
  • short lived paralysis develops
  • repair in days to months (full recovery)


sunderland's classification

1st degree: conduction deficit w/o axonal interruption (neuropraxia)

2nd degree: axon severed w/o breaching endoneurium (axonotmesis)

3rd degree: lesion in endoneurium, epineurieum and perineuriem remain intact

4th degree: only epineurium remains intact

5th degree: complete transection of n


entrapment neuropathy involving the tibial n

tarsal tunnel syndrome

- involves entrapment of tibial n or one of its terminal branches


anatomy of tarsal tunnel

  • fibro-osseous canal
  • posterior to medial malleolus


  • anterior: tibia
  • lateral: posterior process talus and calcaneus
  • medial: flexor retinaculum (lacinate ligament)


3 terminal branches of tibial n

medial plantar n

lateral plantar n

medial calcaneal n


s/s tarsal tunnel syndrome

  • cc diffuse plantar pain or medial ankle pain
  • pain aggravated by standing and relieved with rest
  • pain may radiate proximally to the calf


common causes tarsal tunnel syndrome

  • space occupying lesion (ganglion, lipoma, varicosities, neurilemoma)
  • exostosis or fracture fragments
  • hindfoot varus or valgus (decreases volume w/i tarsal tunnel --> increase pressure on tibial n)
  • talo-calcaneal coalition
  • accessory m w/i canal (accessory soleus or FDL)


tinel vs. villeix sign

tinel = pain radiating distal (shooting pain alon gthe course of MPN and LPN)

villeix = pain radiating proximal

ask "what do you feel"


diagnostic criteria tarsal tunnel syndrome


  1. history of neurtic symptoms
  2. positive tinel sign
  3. supporting NCV studies
  • If none of above criteria is met then diagnosis should be excluded
  • If one of above criteria is met then other diagnosis should be considered
  • If all three criteria is met and symptoms are reproducible then diagnosis is considered


indications for tarsal tunnel syndrome surgery

space occupying lesions or failed conservative treatment


entrapment of the common plantar digital n occupying the 3rd interspace

morton's neuroma


causitive factors morton's neuroma

  • Transverse metatarsal ligament
  • Narrower innerspace between 3rd and 4th metatarsals
  • Increased mobility between 3rd and 4th rays
  • Tethering of nerve beneath metatarsal heads during dorsiflexion when ambulating


s/s morton's neuroma

  • medial-lateral squeeze
  • focal tenderness to deep palpation
  • positive mulder's click
  • complaints of anesthesia to neighboring toes

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