Nerve lesions week 4 Flashcards
What are the 4 types of nerve lesions? Give examples. Discuss potential for regeneration for diff types of injuries and overall.
compression: median nerve at the carpal tunnel, when ext “fall asleep”. potential for recovery is the highest with this type of nerve lesion. if have intervertebral discs slip compressing a spinal nerve for a long time have less potential for recovery.
crush: patient falls or a heavy object falls on the limb
laceration: cut hand cutting a bagel. one of worst ways to injure a nerve
stretch: brachial plexus injuries after trauma. can occur during child birth when arm and head are separated. potential for recovery depends on how much the nerve has been stretched.
Key to reinnervation is maintaining integrity of the CT coverings around a nerve. Helps nerve get back to its target. Where you lesion a nerve matters. Once injure a nerve it’s branches distal to that degenerate
True or false: Depending on the location of a nerve lesion, not all of the sensory or motor innervation supplied by that nerve will be lost. Explain answer.
True. An ulnar nerve injury at the elbow will have more severe/different sx than an injury at the wrist. Location of the injury can give clues to which nerves might possibly be damaged.
When looking at nerve lesion cases, must look at motor innervation. Is strength limited to individual muscles or groups of muscles? If pts presents with muscle atrophy, is a sign that nerve lesion is most likely not acute.
Discuss the importance of looking at sensory innervation as it pertains to nerve lesions.
Must see if sensation is intact and if it is/is not intact in certain areas. Ascertain whether or not pattern follows a dermatomal or peripheral nerve pattern.
Dermatomal: area of skin innervated by one spinal nerve
peripheral nerve: area of skin composed of more than one dermatome
It is important to observe posturing of the affected limb at rest when assessing possible nerve lesions. Aternative positioning may be the result what 3 things?
- pain
- muscular weakness or paralysis
- prolonged period of immobilization
What clinical sign is observed when the wrist is unable to extend? What nerve is likely lesioned in this case?
Wrist drop is observed. Radial nerve is likely lesioned bc it innervates extensors of the hand (located in the posterior forearm)
What are ways in which the radial nerve can be lesioned? What motor and sensory deficits would be observed?
Saturday night palsy-wrist drop
Compression of radial nerve in radial groove of humerus
Fx at the mid shaft of the humerus
Using too tall crutches-would see sx in triceps as well bc compressing it at level of axilla where it first branches
motor deficits: wrist extension, finger extension, weakness with supination, weaknes with thumb abduction, grip weakness
sensory deficits: tinglling and numbness over posterior arm and forearm, tingling and numbness in dorsal surface of thumb, tingling and numbners in lateral dorsum of hand
With a nerve lesion to the long thoracic nerve, what sx may be observed and why?
In the case, a woman presented with deficits in scapular protraction, flexion of the arm, and abduction of the arm (with flexion being more limited than abduction). She did not have any sensory deficits. The long thoracic nerve innervates the serratus anterior which attaches to the entire medial borders of the scapulae and is repsonsible for protraction of the scapula. Along with the trapezius, it can also upwardly rotate the shoulder. In order to fully flex the arm overhead, the scapula must be in a protracted/abducted position and must upwardly rotate. The serratus also holds the scapulae agains the thoracic wall and a weak serratus anterior can result in winging of the scapula.
Note: If there is weakness of the trapezius, abduction is more limited. If there is weakness of the serratus, flexion is more limited. Both upwardly rotate the scapulae.
What is Tip-Takers/Waiter’s tip due to? What does it look like? Why is it observed?
due to lesion of upper trunk of brachial plexus- C5 and C6. observe limb positioned at the side, medial rotation of the arm, forearm extension at elbow. Note: Nothing is wrong with pts hand. Can make a fist, extend fingers,wrist. But, hand is not useful if you can use your shoulder. Shoulder puts hand in a functional position. Hand in this position bc proximal lesion
A patient comes into the ER after a motorcycle crash. The patient is alert and oriented and reports that he was thrown from his bike and landed on his right shoulder. At rest his limb is positioned limply against the side of his trunk with his elbow extended and his arm internally rotated, however his muscle bulk of both arms is symmetrical. Upon examination, he cannot abduct or externally rotate his shoulder. He is unable to actively flex his elbow or supinate his forearm. He lacks sensation over his deltoid, as well as his lateral forearm and hand. The biceps and brachioradialis reflexes are absent. What has been lesioned and how do you know?
Exam indicates pt has affected deltoid (axillary: C5 and C6), biceps/brachialis (musculocutaneous: C5-C7), supra/infraspinatus (suprascapular: C5 and C6), and supinator (radial nerve C5-T1; supinator primarily C5 and C6). Note that pt has many muscles affected which means many affected nerves-indication of more proximal injury. Also note that all of these nerves have the spinal nerves C5 and C6 in common and that pts sx follow a dermatomal vs a peripheral nerve pattern. Pt has sustained an upper brachial plexus injury to C5 and C6 (remember they form upper trunk). More proximal muscles are inervated by higher levels of spinal nerves (C5/C6) and distal muscles are innervated by C7/C8/T1. Upper brachial plexus injury can occur due to trauma, difficult child birth when head and shoulders are pulled apart (stretch lesion)
A lower brachial plexus injury would affect what nerves? A middle brachial plexus injury?
lower C8/T1
middle: C7. note that middle brachial plexus injuries are less common bc it is more protected
What are ways in which the brachial plexus can be injured?
compressed btwn anterior and posterior scalenes, compressed when have an extra rib, compressed by pectoralis minor
What motor and sensory deficits may be observed with compression of the median nerve in carpal tunnel syndrome? What sx and what physical exam sign may be observed with a more proximal median nerve lesion and why is it seen? How could you injure your median nerve more proximally?
In carpal tunnel syndrome:
motor deficits: weakness of thumb opposition, weakned thumb flexion, weakened thumb abduction, weakned flexion at 2nd and 3rd MCP
sensory: decreased sensation in 1-3rd fingers, some decreased sensation in 4th digit. Note: no palmar sensory loss bc palmar cutaneous branch of median nerve passes over the flexor retinaculum!
Notice motor deficits are in muscles of thenar eminence-innervated by recurrent branch of median nerve. On exam, can look for symmetry in thenar eminences.
Could lesion median nerve more proximally with fx of elbow, elbow dislocation
With a more proximal lesion of the median nerve, would observe weakness/paralyis of forearm pronation, wrist flexion, even more pronounced weakness in flexion of the thumb
With a more proximal median nerve injury, can observe Benediction sign. Is seen with weakness or inability to flex the first 3 fingers. Lateral half of flexor digitorum profundus, flexor digitorum superficalis, flexor pollis brevis, and flexor pollicis longus are all affected and cause sx. Can flex middle and ring fingers bc ulnar nerve is intact
What motor and sensory deficits may be observed with an ulnar nerve lesion in the hand? What physical exam sign may be observed with a chronic ulnar nerve lesion? How can the ulnar nerve be injured more proximally and what sx would be observed?
distal ulnar nerve lesion in hand:
motor deficits: weakness of finger abduction and adduction, weakness of thumb adduction, weakness of flexion of the 5th digit, weakness of opposition of the 5th digit, weakned flexion at the 4th and 5th MCP. note that no matter how proximal or distal and ulnar nerve lesion is, will have issues wit splaying the fingers bc ulnar nerve (deep branch) innervates PADS and DABS
sensory deficits: tingling and numbness in 4th and 5th digits, tingling and numbness on teh medial aspect of teh dorsum and palm of the hand.
Claw hand deformity is observed with chronic ulnar nerve lesion. Loss of lumbricals 3 and 4 result in extension of the MCP joint of the 4th and 5th fibers bc the extensor musculatur to those fingers is unopposed (flexor digitorum profundus, interosseus muscles also affected)
The ulnar nerve can be lesioned more proximally through compression in the medial epicondyle, flexor carpi ulnaris. Would observe weakened wrist flexion, weakned ulnar deviation (wrist adduction), loss of flexion at the DIP of the 4th and 5th digits (test: why not MCP and PIP?)
