Lumbar Plexus Flashcards
What is the lumbar plexus?
A network of nerve fibres that supplies the skin and musculature of the lower limb
Where is the lumbar plexus located?
Within the substance of the psoas major muscle, and the anterior of the transverse processes of the lumbar vertebrae
What is the lumbar plexus formed by?
The anterior rami (divisions) of the lumbar spinal nerves, L1, L2, L3 and L4
What does the lumbar plexus receive contributions from?
The thoracic spinal nerve 12
What happens at each vertebral level?
Paired spinal nerves leave the spinal cord via the intervertebral foramina of the vertebral column
What happens once spinal nerves have left the vertebral column?
Each nerve divides into anterior and posterior nerve fibres
How does the lumbar plexus begin?
As the anterior fibres of the spinal nerves L1-L4
What happens to the anterior rami of the L1-4 spinal roots?
They divide into several cords, which then combine together to form the six major peripheral nerves of the lumbar plexus
What happens to the six major peripheral nerves of the lumbar plexus?
They descend down the posterior abdominal wall to reach the lower limb, where they innervate their target structures
What are the 6 major peripheral nerves of the lumbar plexus?
Iliohypogastric nerve Ilioinguinal nerve Genitofemoral nerve Lateral cutaneous nerve of the thigh Obturator nerve Femoral nerve
Where does the iliohypogastic nerve run?
To the iliac crest, across the quadratus lumborum muscle of the posterior abdominal wall
Where does the iliohypogastric nerve perforate?
The transversus abdominis
What are the roots of the iliohypogastric nerve?
L1 (with contributions from T12)
What muscles does the iliohypogastric nerve innervate?
Internal oblique
Transversus abdominis
What is the sensory function of the iliohypogastric nerve?
Innervates posterolateral gluteal skin in the pubic region
What course does the ilioinguinal nerve follow?
The same as the iliohypogastric
Where does the ilioguinal nerve pass through?
After innervating the muscles of the anterior abdominal wall, it passes through the superficial inguinal ring
What is the root of the ilioguinal nerve?
L1
What muscles does the ilioinguinal nerve innervate?
Internal oblique
Transversus abdominis
What are the sensory functions of the ilioinguinal nerve?
Innervates the skin on the upper middle thigh
In males, it also supples the skin over the root of the penis and anterior scrotum
In females, it supplies the skin over the mons pubis and labium majus
What happens to the genitofemoral nerve after leaving the psoas major muscle?
It quickly divides into a genital branch, and a femoral branch
What are the roots of the genitofemoral nerve?
L1, L2
What muscles does the genitofemoral nerve innervate?
The genital branch innervates the cremasteric muscle
What are the sensory functions of the genitofemoral nerve?
The genital branch innervates the skin of the anterior scrotum (in males), or the skin over mons pubis and labium majus (in females).
The femoral branch innervates the skin on the upper anterior thigh
Where does the lateral cutaneous nerve of the thigh enter the thigh?
At the lateral aspect of the inguinal ligament
What are the roots of the lateral cutaneous nerve of the thigh?
L2, L3
What muscles are innervated by the lateral cutaneous nerve of the thigh?
None- it has a purely sensory function
What are the sensory functions of the lateral cutaneous nerve of the thigh
Innervates anterior and lateral thigh down to the level of the knee
What are the roots of the obturator nerve?
L2, L3, L4
What muscles does the obturator nerve innervate?
Obturator externus Pectineus Adductor longus Adductor brevis Adductor magnus Gracilis
What are the sensory functions of the obturator nerve?
Innervates the skin over the medial thigh
What are the roots of the femoral nerve?
L2, L3, L4
What muscles does the femoral nerve innervate?
Illiacus
Pectineus
Sartorius
All muscles of quadriceps femoris
What is the sensory function of the femoral nerve?
Innervates the skin on the anterior thigh and medial leg
What is a lumbosacral plexopathy?
A disorder affecting either the lumbar or sacral plexus of nerves
How common are lumbosacral plexopathies?
Rare
What causes a lumbosacral plexopathy?
Damage to the nerve bundles
When is a plexopathy suspected?
If the symptoms cannot be localised to a single nerve
What may a patient complain of when they have a plexopathy?
Neuropathic pains
Numbness
Weakness
Wasting of muscles
Give 3 causes of lumbosacral plexopathy
Diabetic amyotrophy
Idiopathic pleoxopathy
Tumours and other local invasions
What happens in diabetic amyotrophy?
High blood sugar levels damage the nerves
What is idiopathic plexopathy the lumbosacral equivalent of?
Parsonage-Turner syndrome (which affects the brachial plexus)
How can tumours and other local invasions can plexopathy?
Due to compression of the plexus
What does treatment of a plexopathy depend on?
What is causing the symptoms
How is a lumbosacral plexopathy treated when its caused by tumours and space occupying lesions?
They should be removed if possible
How is a lumbosacral plexopathy treated when it has a diabetic or idiopathic cause?
High-dose corticosteroids
