Nerve Palsies in the Limbs Flashcards by Lucy McLean

What is a dermatome?

A sensory area of skin supplied by a single spinal nerve

Adjacent dermatomes overlap considerably

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What are axial lines?

Result of embryological development of limb buds growing out from body wall (anterior and posterior)

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Is there any overlap between adjacent pre- and post-axial dermatomes?

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STAND on?

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SLEEP on?

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SIT on?

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SHIT on?

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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)

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Which nerves supply the hip joint (3)?

Obturator nerve (predominantly)
Femoral nerve
Lateral femoral cutaneous nerve

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What is a myotome?

Group of muscles supplied by one segment of spinal cord

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What is the brachial plexus?

Large network of nerves supplying the upper limb, extending from the cervical spine to the axilla

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What is the brachial plexus divided into?

Roots -> trunks -> divisions -> cords -> branches

SAVED AS BRACHIAL NERVES

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What is porter’s tip?

Erb-Duchenne paralysis

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Brachial plexus lesions - what damage is caused by downward traction e.g. fall on side of neck?

C5, 6 damage (deltoid & shoulder muscles, brachialis & biceps)
Porter’s tip

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Brachial plexus lesions - what damage is caused by upward traction e.g. breech delivery?

T1 damage (intrinsic muscles)

* Hand “clawed” (Klumpke’s paralysis)

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Brachial plexus lesions - what damage is caused by upward traction e.g. breech delivery?

T1 damage (intrinsic muscles)

* Hand “clawed” (Klumpke’s paralysis)

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What anatomical terms should be used to describe the forearm?

•Use “RADIAL” and “ULNAR”
(rather than lateral and medial)
•Use “VOLAR” or “PALMAR” and “DORSAL”
(rather than anterior and posterior)

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How might the axillary nerve be damaged?

•Fracture of humeral neck
•Shoulder dislocation
•Saturday night palsy
(branch of brachial plexus)

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What does motor deficit of the axillary nerve cause?

Loss of shoulder abduction - deltoid

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What does sensory deficit of the axillary nerve cause?

Loss of sensation in badge area

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What are the roots of the radial nerve?

C5-8, T1

SAME AS BRACHIAL PLEXUS

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What artery is the radial nerve associated with?

Profunda brachii

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How does the radial nerve enter the forearm?

By passing between the brachioradialis and brachialis

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In which areas is the radial nerve at risk of damage?

Spiral groove of humerus

* Lat. intermuscular septum

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How might the radial nerve become damaged?

* Humeral shaft fracture * Saturday night palsy * Exposure of proximal radius

What does motor deficit of the radial nerve cause?

Wrist drop

What does sensory deficit of the radial nerve cause?

1st web space dorsally

What are the roots of the median nerve?

C7-8, T1

Which artery is the median nerve closely associated with?

Brachial artery

How does the median nerve enter the forearm?

By passing between the two heads of the pronator teres

In which areas is the median nerve at risk of damage?

Volar aspect wrist (& cubital fossa)

How might the median nerve become damaged?

* Complication of carpal tunnel syndrome | * Wrist lacerations

What does motor deficit of the median nerve cause?

* Thenar wasting (monkey hand) | * Pointing finger

What does sensory deficit of the median nerve cause?

Sensory loss in the volar aspect of the thumb

What are the roots of the ulnar nerve?

C7-8, T1

What artery is the ulnar nerve associated with?

Superior ulnar collateral artery

How does the ulnar nerve enter the forearm

By passing between two heads of flexor carpi ulnaris

Where is the ulnar nerve at risk?

Behind medial epicondyle of humerus

What might cause damage to the ulnar nerve?

Fracture of humeral condyles

What does motor deficit of the ulnar nerve cause?

* Claw hand | * Hypothenar and 1st dorsal interosseous wasting

What does sensory deficit of the ulnar nerve cause?

Little finger

Where is the lumbar plexus?

Les in surface of quadrates lumborum and within body of psaos muscle

Where do most of the major nerves around the hip exit the pelvis?

The sciatic foramen

Which nerves 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?

L2-4

What is the largest branch of the lumbar plexus?

Femoral nerve

What is the route of the femoral nerve?

* Passes through psoas muscle * Exits pelvis under inguinal ligament, lateral to femoral artery, vein and lymphatic channels in femoral triangle - VAN with Vein next to “V” of legs

What does the femoral nerve supply?

Quadriceps muscles in thigh (anterior)

How does the femoral nerve terminate?

Terminates in long fine sensory branch (Saphenous Nerve - accompanies femoral artery in subsartorial canal of thigh, and long saphenous vein in lower leg and in front of medial malleolus at ankle to supply great toe)

What are the roots of the lateral femoral cutaneous nerve?

L2-3

Where is the lateral femoral cutaneous nerve?

Lies on the surface of iliac muscle

Where does the lateral femoral cutaneous nerve exit the pelvis?

Usually exits pelvis under lateral end of inguinal ligament, but variable

What is the function of the LFCN?

Purely sensory to lateral aspect of thigh

What does compression of the LFCN cause?

Meralgia paraesthetica

What are the roots of the sciatic nerve?

L4-S3

Describe the sciatic nerve

* Largest nerve in body * Main branch of sacral plexus * Broad and flat with accompanying artery

Where does the sciatic nerve exit the pelvis?

Sciatic foramen (below piriformis muscle)

Where does the sciatic nerve run?

Deep to the gluteus maximus muscle

What does the sciatic nerve supply?

* Supplies hamstring muscles in thigh (posterior) * Part of adductor magnus * All lower leg and foot muscles via terminal branches (tibial and common fibular nerves) - height of division variable (really 2 nerves)

What may cause damage to the sciatic nerve?

* Posterior dislocation of hip * Intra-muscular injections * During surgery - division devastating

What are the roots of the common fibular nerve?

L4-S2 | previously called lateral popliteal nerve, then common peroneal nerve

From what nerve does the common fibular nerve arise?

Sciatic - smaller and lateral branch

What is the route of the common fibular nerve?

Passes around lateral aspect of neck of fibula

What is the effect of deficit of the common fibular nerve?

Foot drop and slapping gait - most commonly injured nerve in lower limb

Describe the common fibular nerve

* Communicating branch to sural nerve | * Divides into superficial and deep fibular nerves