MSK Nerves of the lower limb Flashcards
Where is the lumbar plexus located?
In the lumbra region, within the psoas major and anterior to transverse process of lumbar vertebrae
What are the spinal nerves forming the lumbar plexus?
T12-L4
At each vertebral level paired spinal nerves leave the spinal chord via the intervertebral foramina. The nerves then divide into anterior and posterior - the lumbar plexus is the anterior fibres
List the major peripheral nerves of the lumbar plexus
Iliohypogastric nerve Ilioinguinal nerve Genitofemoral nerve Lateral cutaneous nerve of the thigh Obturator nerve Femoral nerve
I, I Get Leftovers On Fridays
What is lumbosacral plexopathy?
Rare disorder affecting either lumbar or sacral plexus
The symptoms cannot be localised to a single nerve - may be numbness, weakness, muscle wastage
Main cause is diabetic amyotrophy - high blood sugar levels damage the nerves
Tumors can cause compression of the plexus
Describe the Iliohypogastric nerve
Runs along posterior abdo wall to the iliac crest.
Nerve roots are L1 with some contribution of T12
Motor functions: internal oblique and transversus abdominis
Sensory functions: posterolateral gluteal skin
Describe the Ilioinguinal nerve
Roots: L1
Motor functions: (same as iliohypogastric) internal oblique and transversus abdominas
Sensory functions: skin of upper middle thigh and genitalia
Describe the Genitofemoral nerve
Roots: L1 L2
Motor functions: genital branch innervates a muscle in the testis
Sensory functions: Genital branch innervates skin of genitals and femoral branch innervates skin of upper anterior thigh
Describe the Lateral cutaneous nerve of thigh
Purely sensory function
Enters thigh at lateral inguinal ligament
Roots: L2 and L3
Sensory functions: anterior and lateral thigh down to knee
Describe the Obturator nerve
Roots: L2 3 4
Motor functions: medial adductors of thigh (adductor longus brevis magnus, gracilis, pectineus and obturator externus)
Sensory functions: skin of medial thigh
Describe the Femoral nerve
Largest branch of lumbar plexus
Roots: L2 3 4
Motor functions: hip flexers (iliacus, pectineus, sartorius) all quads
Sensory functions: anterior thigh (anterior cutaneous branches) and medial leg (saphenous nerve)
What is the anatomical course of the femoral nerve?
Descends from lumbar plexus in the abdo through the psoas major muscle
The nerve travels through the pelvis to midpoint of inguinal ligament, goes behind ligament into the thigh and splits into anterior and posterior division
Passes through femoral triangle and gives off articular branches to knee and hip joints.
The terminal branch is the saphenous nerve which passes through adductor canal into leg
What are the signs of damage to the saphenous nerve?
Pain paraesthesia or complete loss of sensation of medial side of lower leg
What is the anatomical course of the obturator nerve?
Runs through psoas major along the pelvic wall to obturator foramen. Enters the thigh through the obturator canal and splits into anterior and posterior divisions.
Anterior division descends between adductor longus and brevis. It then pierces fascia lata to become the cutaneous branch of obturator nerve.
Posterior division descends through obturator externus then anteriorly to adductor magnus
Where is the sacral plexus located?
Posterior pelvic wall, anterior to piriformis
What are the spinal nerves that make up the sacral plexus?
S1-4
Receives contributions from L4-5 which combine to form the lumbosacral trunk
Name the branches of the sacral plexus
Superior + inferior gluteal nerve Sciatic nerve Posterior femoral cutaneous nerve Pudendal nerve Nerve to piriformis, obturator externus and quadrator femoris
Some Irish Sailor Pokes Polly
What are the 2 main destinations for the nerves of the sacral plexus?
Leave the pelvis via the great sciatic foramen and enter the gluteal region
Remain in the pelvis and innervate structures there
Describe the superior gluteal nerve
Accompanied by superior gluteal artery and vein for musch of its course
Roots: L4 5 S1
Motor functions: glut med min, tensor fascia lata
No sensory
Describe the inferior gluteal nerve
Accompanied by inferior gluteal artery and vein for much of its course
Roots: L5 S 1 2
Motor functions: glut max
No sensory
Describe the posterior femoral cutaneous nerve
Roots: S1 2 3
No motor
Sensory: posterior thigh and leg and perineum
Describe the pudendal nerve
Roots: S 2 3 4
Motor functions: perineal muscles, sphincter
Sensory functions: penis and clit
What are the roots of the sciatic nerve?
L4 5 S1 2 3
What are the 2 terminal branches of the sciatic nerve?
Tibial branch
Common fibular branch
Describe the tibial branch of the sciatic nerve
Motor functions: innervates all posterior thigh muscles except short head of biceps femoris, all posterior leg and all foot
Sensory functions: posterolateral and lateral foot and sole
- medial calcaneal branches innervate heel skin
- medial plantar nerve innervates lateral 3 1/2 digits and associated sole area
- lateral plantar nerve innervates lateral 1 2/2 digits and associated palm area
