(L7/8: Brachial Plexus Injuries and Peripheral Nerve Lesions) Flashcards
How does the level of the level of the lesion affect the number of muscles effected?
The level of the lesion just means whether it is proximal or distal. The level indicates the extent of the motor and/or sensory deficits and the appearance of the limb. All muscles downstream of the lesion that have not already been innervated will be affected.
In a high lesion more muscles are affected/paralysed.
In a low lesion, fewer muscles are affected but this does not necessarily correlate to a better outcome.
Which muscles does the radial nerve innervate?
All posterior forearm muscles i.e. the extensors of the wrists, fingers and thumb and adductor pollicis longus through the posterior interosseous nerve. It also supplies the skin over parts of the posterior arm, forearm, ASB and dorsolateral hand.
Which muscles does the median nerve innervate?
Supplies the anterior forearm muscles - palmar is Longus, PT, FCR, FDS, Lateral half of FDP, FPL, PQ. In the hand it supplies the thenar eminence and the lateral lumbricals. It also supplies the digits 2 and 3.
Which muscles does the ulnar nerve innervate?
Supplies the medial half of FDP, FCU and most muscles in the hand:
- Adductor pollicis
- The dorsal and palmar interossei
- The medial lumbricals
- The hypothenar eminence muscles (ADM, EDM and ODM).
It also supplies the skin over the medial half of the hand on the dorsum and palm.
What is the effect of high and low radial nerve injury?
A high lesion:
- Loss of innervation to the posterior forearm muscles and so a loss of extension leading to wrist drop
- The individual is unable to extend the wrists, fingers and thumb
- Sensory loss over lateral dorsum
A low lesion (at the level of the wrist): this would mean that there is a loss of sensory deficit over the back fo the hand but no motor problems.
Injury is most common in the humeral shaft - a mid humeral shaft lesion would have weakened elbow extension as, as the nerve comes down, it would have already started sending innervation to triceps.
What is the effect of high and low median nerve injury?
A Low lesion: This leads to thenar eminence wasting - Simian hand. Median nerve is compressed in the carpal tunnel syndrome (an example of a low lesion). This can be treated with an incision through the flexor retinaculum so the median nerve is no longer compressed. Fine movements of the 2nd and 3rd digits are impaired due to loss of the lumbricals. We also see sensory loss.
A high lesion: Leads to bishops hand. The anterior forearm muscles are not being supplied. The medial half of FDP are working so there is still some flexion in the medial 2 digits. The remaining 3 digits cannot be flexed due to loss of FDP, FDS, and FPL and FPB. Bishop’s hand occurs when we try to make a fist.
What is the effect of high and low ulnar nerve injury?
High and low lesions of the ulnar nerve both cause a deformity called claw hand. The claw refers to the combination of flexion at the IPJs of the 4th and 5th digits and hyperextension at the MCPs.
Low: Causes a more severe deformation. There is a loss of function in the lateral FDP and FCU. The median nerve however is still intact. The lumbricals and interossei cannot extend these joints and so cannot pull the IPJs into significant flexion. The median nerve and FDP is still functioning. The claw looks worse. Digits 1 and 2 are normal - FDP and the lumbricals are functional. We get hyperextension at the MCP joint just like in the high lesion. There is unopposed pull of ED, pulling the joint into hyperextension. The fingers of the 4th and 5th are more flexed as FDP to these fingers are still functional. If the ulnar nerve is injured at the wrist, FDP has already sent tendons. It is able to flex the joint. The lumbricals and interossei cannot help to flex and oppose ED.
High: A higher injury looks worse as there is a reduced ability to flex the medial digits due to loss of FDP. ED is unopposed by FDP to flex MCP joint, lumbricals and interossei cannot flex. ED pulls it into hyperextension.
What are the differences between Bishop’s hand and Claw hand?
Bishop’s hand appears when the patient try’s to make a fist because they cannot flex the second and third digits. We do not see hyperextension at the MCPJs and there is thenar wasting.
In claw hand, where high or low ulnar nerve injury, the patient cannot extend 4th and 5th digits due to the loss of interossei/lumbricals. There is hyperextension at the MCPJs. we also see atrophy of the interossei.
What is Erb’s palsy?
Upper brachial plexus injury
What is Klumpke’s palsy?
Lower brachial plexus injury
