Lumbosacral plexus Flashcards
What is a rhizotomy?
Nerve roots can be selectively sectioned for relief of intractable pain or paralysis
What does a spinal nerve divide into?
Posterior and anterior rami
What is a mixed spinal nerve?
Posterior and anterior roots
What kind of nerve is the anterior root?
Motor - going out of the plexus
What kind of nerve is the posterior root?
Sensory - going in to the plexus
What is a spinal nerve?
Arises as rootlets from anterior (ventral) and posterior (dorsal) horns of spinal grey matter
Which spinal nerves form the lumbar plexus?
L1 to L4
Which spinal nerves form the sacral plexus?
L4-S4
What connects the lumbar and sacral plexuses?
Lumbosacral trunk
What is the lumbar plexus composed of?
L1 to L4 anterior rami
Contribution from subcostal nerve T12
Which spinal nerves innervate the femoral nerve?
L2-L4
Which spinal nerves innervate the obturator nerve?
L2-L4
Which spinal nerves innervate the lateral cutaneous nerve of the thigh?
L2-L3
Which spinal nerves innervate the genitofemoral nerve?
L1-L2
Which spinal nerves innervate the ilii-inguinal nerve?
L1
Which spinal nerves innervate the Clio-hypogatric nerve?
L1
Where is the genitofemoral nerve?
Anterior to psoas major
Where is the obturator nerve?
Medial to psoas major
Where are the femoral, lateral cutaneous, ilio-inguinal and ilio-hypogastric nerves?
Lateral to psoas major
What does the femoral nerve do?
Innervate anterior compartment of thigh - flexes hip and extends knee
What does the obturator nerve do?
Supplies medial (adductor) compartment of thigh - flexes hip and extends knee
What is the lumbosacral trunk composed of?
Union of descending branch of L4 and anterior ramus of L5
What is the sacral plexus formed from?
Anterior rami of S1 to S4 and lumbosacak trunk in posterolateral wall of lesser pelvis
How are terminal nerves formed?
Anterior rami of L4 to S3 has ventral and dorsal divisions that combine with similar divisions from other levels
Where do most branches of the sacral plexus leave the pelvis?
Greater sciatic foramen
What is the reference muscle for the sacral plexus?
Piriformis muscle in lower pelvic cavity
Which spinal nerves innervate the sciatic nerve?
L4 to S3
Which spinal nerves innervate the superior gluteal nerve?
L4 to S1
Which spinal nerves innervate. the inferior gluteal nerve?
L5 to S2
Which spinal nerves innervate the pudendal nerve?
S2 to S4
What does the sciatic nerve supply?
Posterior compartment of thigh and muscles of leg and foot
Where is the superior gluteal nerve located?
Passes through greater sciatic foramen above piriformis muscle
What does the superior gluteal nerve supply?
Gluteus medius and gluteus minimus
Where is the inferior gluteal nerve located?
Passes through greater sciatic foramen below piriformis
What does the inferior gluteal nerve supply?
Gluteus maximus
What does the pudendal nerve supply?
Perineum and external genitalia
What is the intervertebral foramen?
Opening between two vertebrae
Characteristics of injury to lumbosacral plexus
Pain/weakness/loss of sensation of lower limb
Symptoms of acute lumbosacral plexitis
Rapid onset of pain of thigh/hip
Symptoms of sciatica
Pain of back/hip/outside leg
What is sciatica?
Compression of spinal nerve root of sacral plexus due to degeneration of intervertebral disc or disc herniation
Why does a mother feel pain in her lower limbs during child birth?
Fetal head compresses nerves of sacral plexus
What is obturator nerve neurectomy?
Spasm of adductor muscles of thigh in spastic paraplegia can be relieved by dividing the obturator nerve
What is piriformis syndrome?
Spasms of piriformis muscle and compression of sciatic nerve causing pain/numbness/tingling along leg and foot
Sciatic nerve emerges inferior to piriformis
Why is piriformis syndrome common in sports players?
They use gluteal muscles frequently, resulting in atrophy
Where should you administer an intragluteal injection?
Superolateral quadrant or superior to the line expanding from the posterior superior iliac spine to the superior border of the greater trochanter
Why is it dangerous to posteriorly dislocate the hip?
May injure the sciatic nerve
leading to paralysis
What is foot drop caused by?
Injury to sciatic nerve
Which areas of the leg are supplied by the saphenous branch of the femoral nerve?
Medial side of leg, medial malleolus and hallux
What is a lumbosacral plexus block?
Anaesthesia to lumbar plexus, including anterolateral and medial thigh, knee and saphenous nerve below knee
Which parts of the leg does a sciatic nerve block numb?
Below knee except from area supplied by saphenous nerve
When will the superior gluteal nerve be injured?
Common after hip replacement
Symptoms of injury to superior gluteal nerve
Weakness of gluteus medius/minimus leading to gluteal gait
Weakness abduction in hip joint
Positive Trendelenburg sign
Why do you lean to one side when you injure your superior gluteal nerve?
- When standing on one foot, normally gluteus medius and minimus would contract to prevent pelvis tipping to unsupported side
- If standing foot gluteus medius and minimus are weak, the pelvis tilts downwards on unsupported side
- Individual tends to lean away from unsupported side to compensate for descend of pelvis - waddling
