Neurology of the Lower Limb

Question 1

What can you test

Answer 1

Spinal roots

• Dermatomes
• Myotomes (harder to test, muscles innervated by more than 1 root)

Peripheral nerves

• Cutaneous branches
• Motor branches

Question 2

Name the 6 main lower limb nerves

Answer 2

Superior, inferior gluteal (no cutaneous)

Femoral
Obturator
Sciatic
-Common fibular (superficial and deep)
-Tibial (plantar)

Question 3

Describe the regions covered by the lower limb dermatomes and where you can test each root

How would you test each dermatome

Answer 3

L1, inguinal region
L2, upper ant thigh
L3, lower ant thigh and knee
L4, medial leg, big toe
L5, lateral leg, 3rd toe
S1, little toe
S2, post thigh, popliteal fossa
S3, gluteal region
S4, anal canal 

Pin prick

Question 4

Where is the cutaneous innervation of the subcostal (T12), ilioinguinal (L1), genitofemoral (L1-2)

Answer 4

Subcostal, lateral of inguinal region
Genitofemoral, medial of inguinal region, ant scrotum, labia major
Ilioinguinal, groin area

Question 5

Where is the cutaneous innervation of the lateral femoral (L2-3)

Answer 5

Lateral thigh

Question 6

Where is the cutaneous innervation of the anterior and intermediate cutaneous nerve from the femoral (L2-3)

Answer 6

Anterior, medial thigh

Anterior medial leg

Question 7

Where is the cutaneous innervation of the lateral sural from the common fibular (L4-5)

Answer 7

Lateral upper leg

Question 8

Where is the cutaneous innervation of the superficial fibular (L5-S1)

Answer 8

Dorsal side of foot minus 1st webbing

Question 9

Where is the cutaneous innervation of the clonal nerves

Answer 9

Gluteal region

Question 10

Where is the cutaneous innervation of the posterior femoral cutaneous (S2-3)

Answer 10

Posterior medial thigh and popliteal region

Question 11

Where is the cutaneous innervation of the obturator (L2-3)

Answer 11

Medial posterior lower and upper thigh

V small space, generally not tested

Question 12

Where is the cutaneous innervation of the saphenous (L4), branch of the femoral

Answer 12

Medial strip of posterior thigh and medial side of foot

Question 13

Where is the cutaneous innervation of the calcaneal branch of the tibial (S2-3)

Answer 13

Back and plantar surface of heel

Question 14

Where is the cutaneous innervation of the sural nerve (S1)

Answer 14

Lateral side of foot and lateral posterior of leg

Question 15

What are the lower limb myotomes for
hip flexion
hip extension

Answer 15

Flexion
L2-3

Extension
L5-S1

Question 16

What are the lower limb myotomes for
Knee extension
Knee flexion

Answer 16

Extension
L3-4

Flexion
L5-S1

Question 17

What are the lower limb myotomes for
Ankle extension
Ankle flexion

Answer 17

Extension
L4-5

Flexion
S1-2

Question 18

What are the lower limb myotomes for
Foot inversion
Foot eversion
Foor intrinsics

Answer 18

Inversion
L4-5

Eversion
L5-S1

Intrinsics
S2-3

Question 19

What are the roots of the nerves of the lumbar plexus

• subcostal
• iliohypogastric
• ilioinguinal
• genitofemoral
• lateral thigh cutaneous
• femoral
• obturator
• lumbosacral

Answer 19

Subcostal T12
Iliohypogastric L1
Ilioinguinal L1
Genitofemoral L1-2 (pierces psoas major)
Lateral thigh cutaneous L2-3
Femoral L2-4
Obturator L2-4
Lumbosacral L4-5 (joints with upper sacral => sciatic)

Question 20

Describe the

• Location
• how damage to the nerve can occur
• cutaneous innervation of the femoral nerve (L2-4)

Answer 20

Passes between groove between psoas and illiacus

Damage here v rare
-surgical traum to branches

Cutaneous

• L2-3, anterior, medial cutaneous of upper thigh
• L4, medial leg and foot (saphenous)

Question 21

Describe the

• Location
• how damage to the nerve can occur
• cutaneous innervation of the obturator nerve (L2-4)

Answer 21

Passes medial to psoas major => obturator foramen

Damage here v rare
-Can’t adduct hip

Cutaneous
-L2-4, medial thigh, v small areas, hard to test

Question 22

Describe referred pain that can be found in the knee and hip region and why

Answer 22

Hip and knee share femoral and obturator innervation

Pain referred from hips <=> knees as a result

Question 23

Describe the

• location
• how damage to the nerve can occur
• cutaneous innervation of the lateral femoral cutaneous nerve (L2-3)

Answer 23

Passes near ASIS under inguinal canal, lateral to hip

Sigmoid colon tumors can compress nerve/tight jeans => myalgia paresthesia

Cutaneous
-L2-3, lateral thigh

Question 24

Describe the nerve found in the anterior division of the sacral plexus

Answer 24

Tibial, L4-S3 (joints sciatic)

Question 25

Describe the 3 nerves found in the posterior division of the sacral plexus

Answer 25

Common fibular L4-S2 (not S3, not plantar) Sup gluteal L4-S1 Inf gluteal L5-S2

Question 26

Describe the 5 nerves found in the direction divisions of the sacral plexus

Answer 26

``` Pudendal S2-4 (perineum) Perforating cutaneous S2-3 Post cutaneous of thigh S1-3 Perineal S3-4 (levator ani) Piriformis S1-2 ```

Question 27

What muscles are innervated by the superior gluteal nerve (L4-S1)

Answer 27

Gluteus medius Gluteis minimus Tensor fascia lata Hip joint

Question 28

What muscles are innervated by the inferior gluteal nerve (L5-S2)

Answer 28

Gluteus maximus

Question 29

What cutaneous nerves come off the posterior cutaneous nerves of the thigh

Answer 29

Superior cluneal Middle cluneal Inferior cluneal Posterior femoral cutaneous (often damaged by compression)

Question 30

Describe the route of the sciatic nerve (L4-S3)

Answer 30

Emerges from infrapiriformis space Splits behind biceps femoris => tibial and common fibular But emergence highly variable

Question 31

What is sciatica | How can you test for it

Answer 31

Bending over stretches roots => shooting pains | Test by stretching, if affected => pain

Question 32

What cutaneous nerves come off the tibial nerve (L4-S3) | How is it damaged

Answer 32

Cutaneous - Medial plantar - Lateral plantar - Calcaneal Hard to damage in isolation Compressed by med retinaculum

Question 33

What cutaneous nerves come off the common fibular (L4-S2)

Answer 33

Cutaneous (superficial) - Lateral leg - Dorsal foot minus 1st webbing Cutaneous (deep) -1st webbing Most commonly damaged