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 –L5, S1, S2

Clinical Principles Detecting subtle weakness –Get up from squat Quadriceps –Stand on tip toes Gastrocnemius/Soleus –Stand on heels Tibialis Anterior

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)

CASE 1

History 20 yo college student involved in an MVA She suffers multiple pelvic fractures She complains of weakness and numbness of the right leg

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

SENSORY LOSS

Localization FindingMuscleNerveRoot Ft DorsiflexTIB ANTPER (FIB)L4,5 Grt toe extEHLPER (FIB)L5 Toe ext EDL, EDBPER (FIB)L4,5 Foot eversionPER L, BPER (FIB)L4,5 Foot plant flexGASTROC,TIBS1,2 SOLEUS Toe flexFDL/FDBTIBL5,S1 Foot invPOST TIBTIBL4,5 Knee flexMULTTIB/PERL5S1S2

Common Fibular (Peroneal) Nerve Common Fib Deep Fib Superficial Fib Per LongusTib Ant Per BrevisEHL Per Tertius EDB

SENSORY LOSS IN A DEEP PERONEAL (FIBULAR) NEUROPATHY

Final Diagnosis Sciatic neuropathy with selective involvement of the fibular (peroneal) nerve fibers at the level of the pelvis

CASE 2

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

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

SENSORY LOSS

Localization FindingMuscleNerveRoot Sens loss - - Lat fem <<L2 cut

Final diagnosis Lateral femoral cutaneous neuropathy (AKA: Meralgia Parasthetica)

CASE 3

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

Exam He has weakness of: –Foot plantar flexion –Foot inversion –Toe flexion Strength is normal in: –Knee flexion –Foot dorsiflexion –Foot eversion

SENSORY LOSS

Exam FindingMusclePNRoot Ft plant flexGASTROCTIBS1, S2 Toe flexFDL, FDBTIBL5, S1, S2 Foot invPOST TIBTIBL4, L5 Sens loss----MP+LP Ft dorsiflexTIB ANTFIB (per)L4,5 Foot everFIB L, B, TFIB (Per)L5S1 Knee flexMULTSCIATICL5, S1, S2 (Tib and Fib)

Sciatic Nerve in Thigh/ Tibial Nerve in Leg Sciatic Nerve SemitendonousBiceps Long Hd Semi MembranousBiceps Short HD Add Magnus Tibial NerveCommon Fib Nv Gastroc, Med Popliteus Soleus Gastroc, lat Tibialis Post FDL FHL Med PlantarLateral Plantar AH, FDB, FHB ADM, FDM, AH, Int

Final Diagnosis Tibial neuropathy at the popliteal fossa

CASE 4

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

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

SENSORY LOSS

Localization Finding MusclePNRoot Hip flex IP/IliacusFem L1,2,3 Knee Ext QuadsFemL2,3,4 Sens Loss ---FemL2-4 Hip Add ADD L, B, MObtL2,3,4 Add MSciaticL5, S1 Hip Abd Gl Med/MinSup GlutL5, S1, S2 Foot DF Tib antFib (Per)L4,5 Foot PF Gastroc/solTibial S1,S2

Femoral nerve Psoas Iliacus SartoriusPectinius Rectus Femoris Vastus Lat Vastus inter Vastus Med

Final Diagnosis Femoral Neuropathy Related to Diabetes Mellitus

CASE 5

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

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

Localization Finding Muscle PNRoot Stand toes GASTROC/SOL TIBS1,2 Abs AJ GASTROC/SOL TIBS1,2 Sens --- MP, LP, SUS1 Stand Heels TIB ANT FIBL4,5 Foot Inv POST TIB TIB L4,5

Final diagnosis S1 radiculopathy related to a herniated disc (“Sciatica”)

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 Femoral neuropathy - –Nerve adjacent to artery –Spontaneous