Nerve palsies in the limbs Flashcards
Define dermatome
Sensory area of skin supplied by a single spinal nerve Adjacent dermatomes overlap considerably
Look
STAND on S1
SLEEP on S2
SIT on S3
SHIT on S4
What is Hilton’s Law?
The nerves crossing a joint supply the muscles acting on it and the joint itself
- The nerve may supply 2 joints e.g hip and knee
- N.B that for this reason hip disease may give rise to knee pain
Which nerves supply the hip joint?
- Obturator nerve
- Femoral nerve
- Lateral femoral cutaneous nerve (purely sensory)
What is a myotome?
A group of muscles supplied by one segment of the spinal cord
Brachial plexus
- Supplies the upper limb - majority of nerve palsies occur in the upper limb
- Extends from the cervical spine to the axilla
- C5-T1 roots go on to create the upper, middle and lower trunks
Classic Brachial Plexus lesions that cause ‘porter’s tip’
- Downwards traction i.e a fall on side of neck results in stretch of the brachial plexus
- C5,6 damage (deltoid and shoulder muscles, brachialis and biceps)
- Occurs in childbirth when children are pulled through tight space
Result in classic position of the arm - ‘porter’s tip’
This tends to rapidly resolve in children as the roots are still in tact but not in adults.
What Brachial plexus lesions result in a ‘clawed’ hand (Klumpke’s paralysis)?
- Upward traction i.e breech delivery - feet first
- C8 or T1 damage (intrinsic muscles)
What type of injury might cause a damage to all nerve roots in the Brachial plexus?
- Motorcycle accident
- RTA
Look
In descriptive anatomy of the forearm, wrist and hand use…
- ‘radial’ and ‘ulnar’ rather than lateral and medial
- ‘volar’ or ‘palmar’ and ‘dorsal’ rather than anterior and posterior
When is the axillary nerve at risk of damage?
- A fracture of the humeral neck
- Shoulder dislocation
- Saturday night palsy - drunk, passed out and lying on a chair with pressure on part of arm all night
Which nerve supplies the ‘regimental badge area’?
Axillary nerve
Why do you want to know if there is reduced sensation in the regimental badge area prior to putting the bone back in place?
In order to know if the axillary nerve was damaged due to the injury itself or if the doctors caused it.
What can happen as a result of axillary nerve damage?
Deltoid muscle atrophy - whilst the nerve recovers, the muscle wastes. During this period of time the patient won’t be able to actively abduct their arm.
Chronic axillary nerve lesions result in permanent numbness to the lateral shoulder region, atrophy of the deltoid and teres minor muscles, and possibly chronic neuropathic pain.
What are the Radial nerve roots?
C5-T1
Which artery is the radial nerve closely associated with?
Profunda brachii artery
= a branch of the brachial artery
Which cord of the brachial plexus does the radial nerve come from?
Posterior cord
When is the radial nerve at risk of injury?
- Fracture of the humeral shaft
- Saturday night palsy - pressure on the posterior cord of the brachial plexus
- Exposure of proximal radius
With a Radial nerve injury what are the motor and sensory deficits?
Motor deficit - wrist drop
Sensory deficit - 1st web space dorsally
What do the symptoms of a Radial nerve injury depend on?
Depends on the site of the lesion…
- In axilla - loss of elbow extension, wrist extension and sensory changes in the forearm and hand
- In arm - loss of wrist extension and sensory loss
- Forearm - loss of finger extension
- Wrist - loss of sensation e.g handcuffs
What are the Median nerve roots?
C7-T1
The median nerve enters the forearm by passing between what?
The two heads of the pronator teres muscle
Where does the median nerve provide sensation to?
To the thumb, index finger, middle finger and half of the ring finger
When is the median nerve at risk of injury?
- Carpal tunnel syndrome
- Wrist lacerations
In a median nerve injury what are the sensory and motor deficits?
Sensory deficit - volar (palmar) aspect of the thumb
Motor deficit - thenar wasting (monkey hand), pointing finger - see images
Causes of Carpal Tunnel Syndrome
- Developmental
- Trauma - distal radius fracture
- Swellings - ganglion, fibroma, lipoma
- Inflammatory - Rheumatoid, gout, TB, Amyloid
- Metabolic - pregnancy, hypothyroidism
Symptoms of Carpal tunnel syndrome
- Nocturnal pain
- Paraesthesia in part or all of the median nerve distribution
- Wasting of the thenar muscles over time
What are the ulnar nerve roots?
C7-T1
When is the ulnar nerve at risk of injury?
- Fracture of the humeral condyles
- Wrist lacerations
What are the motor and sensory deficits of an ulnar nerve injury?
- Motor - claw hand, hypothenar wasting
- Sensory - little finger
How do doctors test for ulnar nerve injury?
Froment’s test
If the ulnar nerve is not working, the patient will cheat and use their flexor pollicis longus muscle (median nerve) instead of their adductor pollicis muscle (ulnar nerve) to hold onto the object.
What are the roots of the femoral nerve?
L2-4
The largest branch of the lumbar plexus
What muscle does the femoral nerve supply?
The quadriceps muscles in the thigh
Lateral femoral cutaneous nerve
- Roots L2-3
- Purely sensory to lateral aspect of the thigh
- Lies on surface of iliacus muscle
What does compression of the lateral femoral cutaneous nerve cause?
Meralgia paraesthetic
A tingling, numbness and burning pain in your outer thigh.
Sciatic nerve
- Roots - L4-S3
- Largest nerve in the body and is the main branch of the sacral plexus
- Exits the pelvis through the sciatic foramen below the piriformis muscle
- Runs deep to the gluteus maximus muscle
What does the sciatic nerve supply?
- The hamsting muscles in the thigh
- Part of the adductor magnus
- All lower leg and foot muscles via terminal branches
When is the sciatic nerve at risk of injury?
Posterior dislocation of the hip
Intramuscular injections
During surgery - division is devastating
Common fibular nerve
- Roots L4-S2
- Previously called lateral popliteal nerve, then common peroneal nerve
- Smaller and lateral branch of sciatic nerve
When is the common fibular (peroneal) nerve at risk of injury?
As it passes around the lateral aspect of the neck of the fibula, any damage such as a fracture etc could injure the nerve
Damage to this nerve causes foot drop or slapping gait
Deficits caused by injury to the Common Fibular (peroneal) Nerve?
- Foot drop
- Slapping gait - slapping sound made with each step
It is the most commonly injured nerve in the lower limb
Which artery is the ulnar nerve closely associated with in the arm?
Closely associated with the superior ulnar collateral artery (and ulnar artery and nerve are very closely interwoven at wrist)
