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NERVE INJURIES OF THE LOWER EXTREMITY

NERVE INJURIES OF THE LOWER EXTREMITY. STACY RUDNICKI, MD ASSOCIATE PROFESSOR OF NEUROLOGY. Dermatomes of the Leg. Root Innervation of the Leg. Hip Flexion L 1, 2, 3 Knee Extension L 2, 3, 4 Foot Dorsiflexion L 4,5 Foot Plantar Flexion S1, 2 Knee Flexion L5, S1, S2 Hip Extension

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NERVE INJURIES OF THE LOWER EXTREMITY

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  1. NERVE INJURIES OF THE LOWER EXTREMITY STACY RUDNICKI, MD ASSOCIATE PROFESSOR OF NEUROLOGY

  2. Dermatomes of the Leg

  3. Root Innervation of the Leg • Hip Flexion • L 1, 2, 3 • Knee Extension • L 2, 3, 4 • Foot Dorsiflexion • L 4,5 • Foot Plantar Flexion • S1, 2 • Knee Flexion • L5, S1, S2 • Hip Extension • L5, S1, S2

  4. Clinical Principles • Detecting subtle weakness • Get up from squat • Quadriceps/Gluteus maximus • Stand on tip toes • Gastrocnemius/Soleus • Stand on heels • Tibialis Anterior

  5. Reflexes • Knee Jerks - evaluates • Quadriceps muscle • Femoral Nerve • Primarily L4 nerve root (also L2, L3) • Ankle Jerk - evaluates • Gastrocnemius muscle • Tibial Nerve • Primarily the S1 nerve root (also S2)

  6. CASE 1

  7. History • 20 yo college student involved in an MVA • She suffers multiple pelvic fractures • She complains of weakness and numbness of the right leg • She is aware that her right foot is “dropped” relative to the left, and that she must lift her foot up higher to clear her toes

  8. Exam • She has weakness of: • Foot dorsiflexion • Foot eversion • Toe extension • Strength is normal in: • Foot plantar flexion • Foot inversion • Toe flexion • There is just a hint of weakness in knee flexion

  9. SENSORY LOSS

  10. Localization FindingMuscleNerve Root Involved Ft Dorsiflex TIB ANT FIB L4,5 Grt toe ext EHL FIB L5 Toe ext EDL, EDB FIB L4,5 Foot eversion FIB L, B FIB L4,5 Knee flex Mult TIB/Fib L5S1S2 Spared Foot plant flex GASTROC, TIB S1,2 SOLEUS Toe flex FDL/FDB TIB L5,S1 Foot inv POST TIB TIB L4,5

  11. Localization FindingMuscleNerve Root Involved Ft Dorsiflex TIB ANT FIB L4,5 Grt toe ext EHL FIB L5 Toe ext EDL, EDB FIB L4,5 Foot eversion FIB L, B FIB L4,5 Knee flex Mult TIB/Fib L5S1S2 Spared Foot plant flex GASTROC, TIB S1,2 SOLEUS Toe flex FDL/FDB TIB L5,S1 Foot inv POST TIB TIB L4,5

  12. Common Fibular (Peroneal) Nerve Common Fib Short head BF Deep Fib Superficial Fib Fib Longus Tib Ant Fib Brevis EHL Fib Tertius EDB

  13. Differentiating b/w L5 radiculopathy and Fibular Neuropathy • Motor exam • Foot inversion - Posterior tibial muscle • Spared - Fibular neuropathy • Involved - L5 • Sensory exam

  14. Sensory loss in deep fibular, common fibular, and L5 disease

  15. Final Diagnosis Sciatic neuropathy with selective involvement of the fibular (peroneal) nerve fibers at the level of the pelvis Pearl: The fibular component of the sciatic nerve is more susceptible to traumatic injury than the tibial component - “false localization”

  16. CASE 2

  17. History • The patient is a 45 yo man who complains of burning pain in his right lateral thigh • He is otherwise healthy, though over the last 2 years, he has gained 30 pounds because he can’t find time to exercise

  18. Exam • He has normal strength in all muscles of his leg • Reflexes are normal

  19. SENSORY LOSS

  20. Localization Finding Muscle Nerve Root Sens loss - - Lat fem <<L2 cut

  21. Final diagnosis Lateral femoral cutaneous neuropathy (AKA: Meralgia Parasthetica) Pearls: This nerve does not come from the femoral nerve but rather the L-S plexus  There is no motor component  It is trapped as it crosses the pelvic brim, and wt loss or gain can precipitate sxs

  22. CASE 3

  23. History • A 27 yo man is shot at multiple sites in the thigh, popliteal fossa, and foot • He complains of burning pain in the foot and weakness of the foot

  24. Exam • He has weakness of: • Foot plantar flexion • Foot inversion • Toe flexion • Strength is normal in: • Knee flexion • Foot dorsiflexion • Foot eversion • His foot has a “cocked up” appearance and is everted compared to the other foot

  25. SENSORY LOSS

  26. Exam FindingMusclePNRoot Involved Ft plant flex GASTROC TIB S1, S2 Toe flex FDL, FDB TIB L5, S1, S2 Foot inv POST TIB TIB L4, L5 Sens loss ---- MP+LP (tib) <S1 Spared Ft dorsiflex TIB ANT FIB (per) L4,5 Foot ever FIB L, B, T FIB (Per) L5S1 Knee flex HS SHBF SCIATIC L5, S1, S2 (Tib and Fib)

  27. Exam FindingMusclePNRoot Involved Ft plant flex GASTROC TIB S1, S2 Toe flex FDL, FDB TIB L5, S1, S2 Foot inv POST TIB TIB L4, L5 Sens loss ---- MP+LP (tib) <S1 Spared Ft dorsiflex TIB ANT FIB (per) L4,5 Foot ever FIB L, B, T FIB (Per) L5S1 Knee flex HS SHBF SCIATIC L5, S1, S2 (Tib and Fib)

  28. Sciatic Nerve in Thigh/ Tibial Nerve in Leg Sciatic Nerve Semitendonous Biceps Long Hd Semi Membranous Biceps Short HD Add Magnus Tibial Nerve Common Fib Nv Gastroc, Med Popliteus Soleus Gastroc, lat Tibialis Post FDL FHL Med Plantar Lateral Plantar AH, FDB, FHB ADM, FDM, AH, Int

  29. Final Diagnosis Tibial neuropathy at the popliteal fossa Pearl: The appearance of the foot at rest may help distinguish b/w a fibular and a tibial neuropathy - unopposed action of spared muscles

  30. CASE 4

  31. History • An 81 yo man with diabetes mellitus complains of onset of deep aching pain in his right thigh that evolved over a few weeks • He is having trouble walking because his knee “gives out” • He complains of numbness on the top of his leg

  32. Exam • He has weakness of: • Hip flexion • Knee extension • He has normal strength of: • Hip adduction • Hip abduction • Foot dorsiflexion/plantar flexion • His knee jerk is absent, his ankle jerk is preserved

  33. SENSORY LOSS

  34. Localization FindingMusclePNRoot Hip flex IP/Rec Fem Fem L1,2,3 Knee Ext Quads Fem L2,3,4 Sens Loss --- Fem L2-4 Hip Add ADD L, B, M Obt L2,3,4 Add M Sciatic L5, S1 Hip Abd Gl Med/Min Sup Glut L5, S1, S2 Foot DF Tib ant Fib (Per) L4,5 Foot PF Gastroc/sol Tibial S1,S2

  35. Localization FindingMusclePNRoot Hip flex IP/Rec Fem Fem L1,2,3 Knee Ext Quads FemL2,3,4 Sens Loss --- Fem L2-4 Hip Add ADD L, B, M Obt L2,3,4 Add M Sciatic L5, S1 Hip Abd Gl Med/Min Sup Glut L5, S1, S2 Foot DF Tib ant Fib (Per) L4,5 Foot PF Gastroc/sol Tibial S1,S2

  36. Femoral nerve Iliopsoas Sartorius Pectinius Rectus Femoris Vastus Lat Vastus inter Vastus Med

  37. Distinguishing b/w a femoral neuropathy and L2 or L3 radiculopathy • Motor exam • Thigh adduction (obturator nerve) • Spared with a femoral neuropathy • Involved with L2,3 disease • Sensory exam • Loss extends below the knee (medial foreleg) with femoral neuropathy • Saphenous nerve

  38. Final Diagnosis Femoral Neuropathy Related to Diabetes Mellitus Pearl: The femoral nerve is also liable to injury during procedures involving the femoral artery or vein

  39. CASE 5

  40. History • A 27 yo body builder complains of a 4 week history of low back and leg pain • Pain travels down the back of the leg and into the sole of the • He is unaware of weakness and he continues to lift weights

  41. Exam • His routine strength exam is normal • He can stand on his heels with ease • He can stand on his tiptoes on the right but not on the left • His left ankle jerk is absent, right is normal • Sensory exam • Decreased sensation of the sole of the foot, lateral distal leg, and lateral dorsum of the foot

  42. Localization Finding Muscle PNRoot Stand toes GASTROC/SOL TIB S1,2 Abs AJ GASTROC/SOL TIB S1,2 Sens --- MP, LP, SU S1 Stand Heels TIB ANT FIB L4,5 Foot Inv POST TIB TIB L4,5

  43. Localization Finding Muscle PNRoot Stand toes GASTROC/SOL TIBS1,2 Abs AJ GASTROC/SOL TIBS1,2 Sens --- MP, LP, SU S1 Stand Heels TIB ANT FIB L4,5 Foot Inv POST TIB TIB L4,5

  44. Differentiating b/w radicular disease and focal tibial neuropathy • Back pain that radiates into the leg highly suggestive of radicular process • Tibial nerve also innervates the foot inverters yet these are spared • Spontaneous (ie not associated with penentrating trauma) tibial neuropathies would be very unusual

  45. Final diagnosis S1 radiculopathy related to a herniated disc Pearl:  The term sciatica is a misnomer - it is really a root based process, not one of the sciatic nerve  Particularly in large muscles, weakness may be subtle and hence easily missed

  46. Final Comments • Overall, nerves in the leg are less liable to chronic compression/entrapment compared to those in the arms • Most common entrapment in the leg is a fibular (peroneal) palsy at the fibular head • May get the common, superficial, or fibular (peroneal) nerve • Traumatic nerve injuries related to penetrating injury / bony trauma (hip / pelvic fxs) are seen

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