Nerve Palsies in the Limbs Flashcards
What is a dermatome?
A sensory area of skin supplied by a single spinal nerve
Is there overlap between adjacent pre- and post-axial dermatomes?
No - limb buds grow out from the body wall in axial lines
Why are lower limb dermatomes distorted?
-Rotation, extension and borrowing of skin from the trunk
What is Hilton’s Law?
- “The nerves crossing a joint supply the muscles acting on it and the joint itself”
- “The motor nerve to a muscle tends to give a branch of supply to the joint that the muscle moves and another to the skin over the joint”
Which nerves supply the hip joint?
- Obturator
- Femoral
- Lateral femoral cutaneous nerve
What is a myotome?
A group of muscles supplied by one segment of the spinal cord
Give two common anatomical variations of the brachial plexus
- Pre-fixed plexus (C4-8)
- Post-fixed plexus (C6-T2)
Name the common brachial plexus lesions
- Downward traction
- C5 and 6 damage
- Arm “porter’s tips”
- Upward traction (breech delivery)
- T1 damage (intrinsic damage)
- Klumpke’s paralysis (clawed hand)
How can the axillary nerve be damaged and which deficits would be seen?
- As a complication of: fractured humeral neck, shoulder dislocation and saturday night palsy (pressure on posterior cord of brachial plexus)
- Deficits: loss of shoulder abduction and sensory loss over regimental badge area
What are the roots of the radial nerve and where does it travel?
- C5-T1
- Passes between brachioradialis and brachialis to enter the forearm
- Posterior interosseous branch passes between 2 planes of supinator
At which anatomical locations is the radial nerve most at risk?
- Spiral groove of humerus and lateral intermuscular septum
- Posterior interosseus branch at the radial neck
How can the radial nerve be damaged and which deficits would be seen?
- Fractures of humeral shaft, Saturday night palsy and exposure of the proximal radius
- Deficits: wrist drop (extensors) and sensory deficit in the dorsal 1st web space
What are the roots of the median nerve and where does it enter the forearm?
- C7-T1
- Between the two heads of pronator teres
At which anatomical locations is the median nerve most at risk?
Volar aspect of the wrist and the cubital fossa
What can cause damage to the median nerve and which deficits would be seen?
- Carpal tunnel syndrome, wrist lacerations, supracondylar fractures and Struther’s ligament
- Deficits: thenar wasting , pointing finger and sensory deficit to the volar aspect of the thumb
What are the roots of the ulnar nerve and where does it enter the forearm?
- C7-T1
- Passes between the two heads of flexor carpi ulnaris
Where is the ulnar nerve most at risk?
-Behind the medial epicondyle of the humerus, wrist and canal of Guyon
What can cause ulnar nerve damage and which deficits would be seen?
- Fractures of humeral condyles and wrist lacerations
- Deficits: claw hand, hypothenar and 1st dorsal interosseous wasting and sensory deficit to the little finger
Where does the lumbar plexus lie?
On the surface of quadratus lumborum and within the body of the psoas muscle
Which major nerves, that lie around the hip, do not exit the pelvis by the sciatic foramen?
- Genitofemoral
- Ilioinguinal
- Femoral
- Lateral femoral cutaneous
- Obturator
What are the roots of the femoral nerve and which plexus is it a part of?
- L2-4
- Lumbar plexus
Describe the route the femoral nerve takes
- Passes through the Psoas major muscle
- Exits pelvis under the inguinal ligament
- Lateral to femoral artery, vein and lymphatic channels in the femoral triangle
Which structures are supplied by the femoral nerve and where do its terminal branches lie?
- Quadriceps muscles in the anterior thigh
- Long fine sensory branch: saphenous nerve
What are the roots of the lateral femoral cutaneous nerve and where does it lie?
- L2-3
- On the surface of the iliacus muscle
- Usually exits pelvis under the lateral end of the inguinal ligament
What does the lateral cutaneous nerve carry?
Sensation to the lateral aspect of the thigh
What happens if the lateral femoral cutaneous nerve is compressed?
Meralgia paraesthetica
What are the roots of the sciatic nerve and which plexus is it a part of?
- L4-S3
- Sacral plexus
Where does the sciatic nerve run?
- Exits pelvis through sciatic foramen below piriformis muscle
- Runs deep to the gluteus maximus muscle
Which structures are supplied by the sciatic nerve?
- Hamstring muscles (posterior thigh)
- Adductor magnus
- All lower leg and foot muscles via terminal branches (tibial and common fibular nerves)
What can cause damage to the sciatic nerve?
- Posterior dislocation of the hip
- IM injections
- Surgery
What are the roots of the common fibular nerve and which nerve is it a branch of?
- L4-S2
- Sciatic nerve
Where is the common fibular nerve at risk and what deficits would be seen?
- As it passes around the lateral aspect of the neck of the fibula
- Deficits: foot drop and slapping gait
Which branches does the common fibular nerve give off?
- Superficial and deep fibular nerves
- Communicating branch to the sural nerve
