Lumbar plexus

Question 1

Anterior or posterior rami

Answer 1

Anterior

Question 2

What are the spinal roots of the lumbar plexus

Answer 2

L1-4

Also receives contribution from T12

Question 3

What do the spinal roots divide into

Answer 3

Cords

Question 4

What do the cords combine to form and how many

Answer 4

6 branches (major peripheral nerves)

Question 5

What are the branches of the lumbar plexus

Answer 5

Iliohypogastric,
Ilioinguinal,
Genitofemoral,
Lateral cutaneous,
Femoral (covered in separate deck)
Obturator (covered in separate deck)

Question 6

Roots of iliohypogastric nerve

Answer 6

L1 with contributions from T12

Question 7

Course of iliohypogastric nerve

Answer 7

Runs to the iliac crest, across the quadratus lumborum muscle of the posterior abdominal wall
Then it perforates the transverse abdominis and divides into terminal branches

Question 8

Motor Innervation of iliohypogastric nerve

Answer 8

Internal oblique muscle

Transversus abdominis muscle

Question 9

Sensory Innervation of iliohypogastric nerve

Answer 9

Posterolateral gluteal skin of pubic region

Question 10

Roots of ilioinguinal nerve

Answer 10

L1

Question 11

Course of ilioinguinal nerve

Answer 11

Same as larger iliohypogastric nerve.

After Innervating musculature of anterior abdominal wall, it passes through superficial inguinal ring

Question 12

Motor Innervation of ilioinguinal nerve

Answer 12

Internal oblique

Transversus abdominis

Question 13

Sensory Innervation of ilioinguinal nerve

Answer 13

Skin on upper middle thigh
Skin over root of penis and anterior scrotum
Skin over mons pubis and labium majus

Question 14

Roots of genitofemoral nerve

Answer 14

L1-2

Question 15

Course of genitofemoral nerve

Answer 15

After leaving psoas major, it quickly divides into a genital branch and a femoral branch

Question 16

Motor Innervation of genitofemoral nerve

Answer 16

Genital branch innervates the cremasteric muscle

Question 17

Sensory Innervation of genitofemoral nerve

Answer 17

Genital branch - skin over anterior scrotum, mons pubis and labium majus
Femoral branch - skin over upper anterior thigh

Question 18

Roots of lateral cutaneous nerve of thigh

Answer 18

L2-3

Question 19

Where does the lateral cutaneous nerve of thigh enter the thigh

Answer 19

At lateral aspect of inguinal ligament

Question 20

Motor Innervation of lateral cutaneous nerve of thigh

Answer 20

None (it’s purely sensory)

Question 21

Sensory Innervation of lateral cutaneous nerve of thigh

Answer 21

Skin over anterior and lateral thigh down to level of knee

Question 22

What is lumbosacral plexopathy

Answer 22

Disorders of either lumbar or sacral plexus caused by damage to nerve bundles

Question 23

Main cause of lumbosacral plexopathy

Answer 23

Diabetic amyotrophy (lumbosacral radioplexus neurophagy) 
High blood glucose damages nerves

Question 24

Other causes of lumbosacral plexopathy

Answer 24

Idiopathic plexopathy (equivalent of personage-turner syndrome of brachial plexus) 
Tumours/local invasions - compress plexus

Question 25

When is a plexopathy suspected

Answer 25

If symptoms can’t be localised to a single nerve

Question 26

How does a patient present with lumbosacral plexopathy

Answer 26

Neuropathic pain,
Numbness,
Weakness and wasting of muscles

Question 27

Treatment for lumbosacral plexopathy

Answer 27

Depends on cause:
Tumours/space occupying lesions - removal
Diabetic/idiopathic - high dose of corticosteroids

Question 28

Where is the lumbar plexus located

Answer 28

In the lumbar region -
Within psoas major
Anterior to transverse processes of lumbar vertebrae