Nerves of the lower limb Flashcards
What are the dermatomes of the lower limb?
L1: inguinal region
L2: upper lateral thigh
L3: lower lateral thigh
L4: medial leg and medial great toe
L5: anterolateral leg and foot, dorsal toes 2-4
S1: lateral margin of the sole of the foot and heel
S2: leg and posterior thigh
S3-4: medial buttock, inter gluteal cleft and perineum
How is the deep tendon reflex of the patellar tendon tested and what is the nerve root?
Ask the patient to sit comfortably with their legs dangling on the edge of the couch.
Strike the patellar tendon (ligament) with a knee hammer.
If the reflex arc is intact a brisk extension of the knee joint will be seen.
Simultaneous contraction of the quadriceps should be palpated on the anterior surface of the thigh.
Repeat the test on the opposite side and compare the responses.
Femoral nerve L2-4.
Main nerve root is L4.
How is the deep tendon reflex of the ankle jerk tested and what is the nerve root?
Ask the patient to sit comfortably with their legs dangling on the edge of the couch.
Strike the calcaneal tendon (Achilles) with a knee hammer while holding the foot (slightly dorsiflexed) with the other hand.
If the reflex arc is intact, a plantar flexion of the ankle joint will occur.
Repeat the test on the opposite side and compare the responses.
S1-S2.
Main nerve root is S1.
What are the surface markings of the sciatic nerve?
Draw the course of the sciatic nerve in the buttock and thigh.
Palpate three bony landmarks- posterior superior iliac spine (PSIS), ischial tuberosity and greater trochanter.
The nerve leaves the greater sciatic notch and enters the gluteal region at the midpoint between the PSIS and the ischial tubersoity.
It forms a downward curve to pass into the thigh around the midpoint between the greater trochanter and the ischial tubersoity before reaching the popliteal fossa (behind the knee).
How would you test the motor component of the sciatic nerve?
Supplies the posterior compartment of the thigh: hamstring muscles (semitendinosus, semimembranosus, biceps femoris) and part of adductor magnus.
Test leg flexion at the knee (ask patient to bend their leg against resistance).
Ask the patient to lie prone on the couch with the legs flexed about 30 degrees.
Ask the patient to flex the knee further .
Apply firm pressure over the distal part of the leg to resist further flexion. With the other hand, palpate the back of the mid thigh for the contraction of the hamstrings.
Foot drop if damaged.
How would you test the motor component of the gluteal nerve?
Innervates the gluteus maximus muscle, responsible for extension of the hip joint
Ask the patient to lie prone with their knees flexed to 90 degrees (to relax the hamstrings)
Ask the patient to lift (extend) their thigh off the couch.
Apply pressure at the distal end of the posterior thigh to resist the extension. With the other hand, palpate the buttock for the contraction of the muscle.
Also innervates the gluteus medius and minimus muscles, responsible for hip abduction.
Ask the patient to lie on one side with both limbs fully extended.
Ask the patient to lift the uppermost limb upward away from the couch.
Apply downward pressure to resist the abduction of the thigh. With the other hand, palpate the gluteus medius for contraction.
How would you test the motor component of the femoral nerve?
Innervates the quadriceps femoris (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) muscles, responsible for extension of the knee joint.
Ask the patient to sit with their knees bent to 90 degrees (over the edge of the couch).
Ask the patient to extend their knee .
Apply firm pressure over the distal part of the leg to resist the extension. With the other hand, palpate the front of the mid-thigh for the contraction of the quadriceps.
How would you test the motor component of the obturator nerve?
Innervates the adductor group of muscles (adductor longus, adductor magnus, adductor brevis) and obturator externus, responsible for adduction of the hip joint.
Ask the patient to lie supine with both limbs fully extended.
Stand on one side of the patient with the test leg passively abducted to 45 degrees.
Ask the patient to adduct forcefully.
Apply force to resist the adduction of the thigh. With the other hand, palpate the medial aspect of the thigh for contraction of the adductors.
How would you test the motor component of the deep peroneal nerve?
Innervates tibialis anterior, extensor hallucis longus and extensor digitorum longus, responsible for dorsiflexion (extension) of the foot.
Ask the patient to sit or lie on the couch with their lower limb fully extended.
Ask the patientt to dorsiflex their foot.
Place the palmar surface of your hand across the dorsum of toes to resist the action.
The tendons of the muscles can be seen and felt.
How would you test the motor component of the superficial peroneal nerve?
Innervates peroneus longus and peroneus brevis muscles, responsible for foot eversion.
Ask the patient to turn the foot outward and plantar flex (eversion) while grasping the forefoot to opposie the movement.
