Nerves supplying the lower limbs

Question 1

What types of structures in the LL are supplied by nerves?

Answer 1

muscle, joints & skin

Question 2

What may lesions in these nerves cause? (3)

Answer 2

• muscle atrophy
• loss of sensation
• loss of motor output (weakness)

Question 3

Describe a nerve plexus.

Answer 3

• intertwining network of nerves
• join after leaving the SC and re-disperse to form mixed nerves that supply the periphery

Question 4

What are the nerves of the lumbar plexus?

Answer 4

L1-L4

Question 5

What do the nerves of the lumbar plexus supply?

Answer 5

The anterior & medial thigh

Question 6

What are the nerves of the sacral plexus?

Answer 6

L4-S4

Question 7

Describe the location of the lumbar plexus.

Answer 7

Starts within the psoas major and emerges anterior to this muscle.

Question 8

Describe the location of the sacral plexus.

Answer 8

Anterior to the piriformis on the posteriolateral wall of pelvic cavity

Question 9

How does the sacral plexus receive L4 and L5 nerves?

Answer 9

Via the lumbosacral trunk

Question 10

How does the sacral plexus branch?

Answer 10

• passes through the greater sciatic foramen
• branches travel above & below the piriformis

Question 11

What are each of the three compartments of the thigh supplied by ?

Answer 11

anterior –> femoral nerve
medial –> obturator nerve
posterior –> sciatic nerve (mainly tibial nerve)

Question 12

What are each of the three compartments of the leg supplied by ?

Answer 12

anterior –> deep fibular nerve
lateral –> superficial fibular nerve
posterior –> tibial nerve

Question 13

The femoral nerve emerges from ______ vertebrae (_____ plexus).

Answer 13

Lumbar (L2-4); lumbar plexus

Question 14

What types of tissues are supplied by the femoral nerve?

Answer 14

muscle & cutaneous

Question 15

Describe the location & branching of the femoral nerve.

Answer 15

• arises from L2-L4
• travels lateral to the psoas major and under the inguinal ligament
• branches into multiple nerves after passing 3cm under inguinal ligament

Question 16

What is the muscular supply of the femoral nerve?

Answer 16

SPI on the Quads
S - Sartorius
P - Pectineus
I - Iliacus
Q - Quadriceps

Question 17

T/F: The iliopsoas gets its innervation from the femoral nerve.

Answer 17

False
- iliacus innervated by femoral nerve
- psoas major innervated by lumbar plexus

Question 18

Describe the cutaneous supply of the femoral nerve.

Answer 18

• supplies skin of anterior & medial thigh
• saphenous nerve (cutaneous branch) supplies medial leg

Question 19

As your pt walks in, they push their knee back before going into the toe-off phase of the gait cycle. Which nerve may be lacerated and why?

Answer 19

Femoral nerve (L2-L4)
- quadriceps innervated by femoral nerve and necessary for knee extension during gait cycle
- loss of innervation = weakness of quads

Question 20

What other symptoms may they be experiencing? What may this indicate?

Answer 20

• loss of cutaneous sensation in anterior/medial thigh and medial leg
• may indicate that pressure is damaging the nerve (ex. retroperitoneal haemorrhage or tumour)

Question 21

The obturator nerve emerges from ______ vertebrae (_____ plexus).

Answer 21

L2-4 (same as femoral nerve); lumbar plexus

Question 22

What types of tissues are supplied by the obturator nerve?

Answer 22

muscle & cuteneous

Question 23

Describe the location of the obturator nerve.

Answer 23

• emerges from L2-4
• travels medial to the psoas major & down through the obturator canal
• splits into anterior & posterior branches (surrounding adductor brevis)

Question 24

What is the muscular supply of the obturator nerve?

Answer 24

AGOx
A - adductors (3)
G - gracilis
Ox - obturator externus

Question 25

What is the cutaneous supply of the obturator nerve?

Answer 25

skin of medial thigh

Question 26

How can you tell if a patient has experienced trauma to their obturator nerve after giving birth?

Answer 26

Check their adductor strength - obturator nerve supplies adductor muscles

Question 27

The lateral cutaneous nerve of the thigh emerges from ______ vertebrae (_____ plexus).

Answer 27

L2-3; lumbar plexus

Question 28

Describe the location of the lateral cutaneous nerve of the thigh. What does it supply (in the name)?

Answer 28

- emerges from L2-3 - travels lateral to the psoas major and under the inguinal ligament (just medial to the ASIS) - supplies skin of lateral thigh

Question 29

If your pt is experiencing pain & paraesthesia (numbness/tingling) in the lateral thigh, what do you suppose may be causing this?

Answer 29

- compression of the lateral cutaneous nerve of the thigh - most likely against the ASIS and inguinal ligament

Question 30

The superior gluteal nerve emerges from ______ vertebrae (_____ plexus).

Answer 30

L4-S1; sacral plexus

Question 31

What types of tissues are supplied by the superior gluteal nerve?

Answer 31

muscle only

Question 32

Which muscles are supplied by the superior gluteal nerve?

Answer 32

- gluteus minimus - gluteus medius - tensor fasciae latae

Question 33

Describe the location of the superior gluteal nerve.

Answer 33

- emerges from L4-S1 spinal nerves - travels through the greater sciatic foramen and above piriformis towards the TFL

Question 34

Describe the sign that indicates a nerve lesion in the superior gluteal nerve.

Answer 34

Trendelenburg sign - weakness in glut. med/min means that abduction is compromised - pt unable to stabilize hip when transferring weight to affected side - "sound side sags" --> unaffected hip drops when shifting when shifting weight to affected side

Question 35

What is the gait adopted by a pt with a lesion in the sup. gluteal nerve?

Answer 35

- they lean over to the side of the lesion when transferring weight to that side - allows them to keep the hip bone aligned with the body (abductors doing no work)

Question 36

What else might this pt experience?

Answer 36

Weak medial rotation of hip

Question 37

The inferior gluteal nerve emerges from ______ vertebrae (_____ plexus).

Answer 37

L5-S2 (sup. gluteal +1); sacral plexus

Question 38

Describe the location of the inferior gluteal nerve. What does it innervate?

Answer 38

- emerges from L5-S2 - travels through greater sciatic foramen & below piriformis - innervates gluteus maximus

Question 39

Describe the gait that results from a lesion in the inferior gluteal nerve.

Answer 39

Gluteus maximus lurch - weak hip extension/lateral rotation - they lean back so that the posterior weight of the trunk pushes the pelvis forward into a posterior tilt (hip extension)

Question 40

The sciatic nerve is comprised of the _________ and ___________ nerves.

Answer 40

Tibial & common fibular (peroneal)

Question 41

Does the sciatic nerve always travel under the piriformis? Explain.

Answer 41

No - in some cases, the common fibular nerve may travel through or above the piriformis

Question 42

Where does the sciatic nerve typically divide into its two parts?

Answer 42

Right above the popliteal fossa.

Question 43

Which posterior thigh muscles are innervated by the sciatic nerve?

Answer 43

Tibial --> hamstrings (except for short head of BF) Common fibular --> short head of biceps femoris

Question 44

The tibial nerve emerges from ______ vertebrae (_____ plexus).

Answer 44

L4-S3; sacral plexus

Question 45

Describe the orientation of the tibial nerve down to the tarsal tunnel.

Answer 45

- branches off the sciatic nerve in lower 1/3 of posterior thigh - vertical course through popliteal fossa (superficial to popliteal artery & vein) - travels deep to soleus (between superficial & deep muscles of post. leg) - enters tarsal tunnel (Very)

Question 46

What happens after the tibial nerve exits the tarsal tunnel?

Answer 46

It divides into the medial & lateral plantar nerves

Question 47

What is the corresponding cutaneous supply of the tibial nerve?

Answer 47

- tibial nerve innervates skin of heel - medial & lateral plantar nerves innervate medial & lateral aspects of plantar foot

Question 48

Other than most of the hamstring muscles (excluding short head of BF), what muscles does the tibial nerve supply?

Answer 48

- all posterior leg muscles - all intrinsic foot muscles on plantar side (via medial & lateral plantar nerves)

Question 49

As your pt walks in, you notice they can't lift their heel (walking without push-off phase). What type of gait is this and what could be causing this?

Answer 49

Flat-foot gait - lesion in popliteal fossa (tibial nerve) - can't use posterior leg muscles ∆ can't do plantar flexion or toe flexion

Question 50

What other symptoms would confirm this hypothesis?

Answer 50

Loss of cutaneous sensation in the heel, as well as the medial & lateral aspects of the plantar foot.

Question 51

Describe the course of the common fibular nerve.

Answer 51

- emerges from L4-S2 (sacral plexus) - branches off the sciatic nerve in the lower 1/3 of post. thigh - leaves popliteal fossa laterally to hug the neck of the fibula, then divides into superficial & deep nerves

Question 52

Where does the deep fibular nerve reside? What does it thus supply down to the foot?

Answer 52

- follows along the interosseous membrane - innervates anterior leg muscles (extensors and tibialis anterior)

Question 53

What does the deep fibular nerve supply once it enters the foot region?

Answer 53

- extensor digitorum brevis - cutaneous between 1st & 2nd toes (yellow)

Question 54

Compression of the deep fibular nerve is referred to as ___________.

Answer 54

anterior compartment syndrome

Question 55

Describe the course of the common fibular nerve and what muscles it correspondingly supplies.

Answer 55

- parts from the deep fibular nerve at the neck of the fibula - innervates lateral leg muscles (fibularis longus & brevis)

Question 56

Describe the cutaneous supply of the superficial fibular nerve.

Answer 56

- starts about 2/3 down the leg - supplies skin of lower lateral leg & dorsum of foot (grey)

Question 57

What would a pt's gait look like if they had a lesion in the common fibular nerve?

Answer 57

Steppage gait - can't dorsiflex or extend toes - at swing phase, foot drops and they lift their knee higher to prevent tripping - foot slaps down in stance phase

Question 58

Why is a lesion in the sciatic nerve more detrimental?

Answer 58

- you lose innervation to all hamstring, leg and foot muscles - causes severe difficulty walking (can't flex knee or foot)

Question 59

Do you lose all cutaneous sensation in the thigh, leg & foot when the sciatic nerve has a lesion?

Answer 59

No, the medial compartment of the leg & foot are spared. - supplied by the saphenous nerve

Question 60

Which nerves are shown in the following image?

Answer 60

Nerve to obturator internus Nerve to quadratus femoris Posterior cutaneous nerve of thigh

Question 61

The nerve to obturator internus innervates...

Answer 61

Nerve to obturator internus Superior gemellus

Question 62

The nerve to quadratus femoris innervates...

Answer 62

Quadratus femoris Inferior gemellus

Question 63

What does the posterior cutaneous nerve of the thigh innervate?

Answer 63

Skin of back of thigh & popliteal region.