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
