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

Finding Muscle Nerve Root

Ft Dorsiflex TIB ANT PER (FIB) L4,5

Grt toe ext EHL PER (FIB) L5

Toe ext EDL, EDB PER (FIB) L4,5

Foot eversion PER L, B PER (FIB) L4,5

Foot plant flex GASTROC, TIB S1,2

SOLEUS

Toe flex FDL/FDB TIB L5,S1

Foot inv POST TIB TIB L4,5

Knee flex MULTTIB/PER L5S1S2

Common Fibular (Peroneal) Nerve

Common Fib

Deep Fib

Superficial Fib

Per Longus Tib Ant

Per Brevis EHL

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

Finding Muscle Nerve Root

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

Finding Muscle PN RootFt 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

Ft dorsiflex TIB ANT FIB (per) L4,5

Foot ever FIB L, B, T FIB (Per) L5S1

Knee flex MULT SCIATIC L5, S1, S2

(Tib and Fib)

Sciatic Nerve in Thigh/ Tibial Nerve in LegSciatic 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

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 Muscle PN Root

Hip flex IP/Iliacus 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

Femoral nerve

Psoas

Iliacus

Sartorius Pectinius

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 PN RootStand 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

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