Brachial Plexus Flashcards
Injury to Roots
Injuries to individual roots are rare. A root can be cut by a gunshot or knife wound, but the root is more commonly avulsed (torn from the spinal cord) by rapid pulling or stretching due to traumatic injury. Since so many roots contribute to many muscles, it is hard to localize the motor effects of the lesion. Sensory loss (loss of a dermatome) may be more diagnostic. The C6 root provides sensation for the thumb.
Upper Trunk Injury
Upper trunk injury (Erb- Duchenne paralysis or Erb palsy) is caused by a birth injury during a breech delivery or a violent displacement of the head from the shoulder such as might occur from a fall from a motorcycle or horse. It results in a loss of abduction, flexion, and lateral rotation of the arm, producing a waiter’s tip hand, in which the arm tends to lie in medial rotation resulting from paralysis of lateral rotator muscles. It can also be associated with shoulder dystocia, a trauma which occurs when the infants shoulder gets caught on the mothers pubic bone during delivery.
Lower Trunk Injury
Lower trunk injury or Klumpke’s palsy may be caused by a difficult breech delivery in which the arm is forcefully abducted. Other causes are a cervical rib or abnormal spasm of the anterior and middle scalene muscles or traumatic forceful abduction of the arm due to a fall or accident. The injury causes a claw hand.
Long Thoracic Nerve Injury
Injury to the long thoracic nerve is caused by a stab wound or during radical masectomy. It results in paralysis of the serratus anterior muscle. This muscle rotates the scapula upward, abducts the scapula and elevates it above horizontal.
Loss of this muscle function results in inability to raise arm above horizontal plane and a winged scapula.
Posterior Cord Injury
Injury to the posterior cord can result in crutch palsy or saturday nite palsy (drunken fool passes out with arm draped over top of chair) Results in loss of extensors of arm, forearm, and hand–results in wrist drop.
Axillary Nerve Injury
Injury of the axillary nerve is caused by a fracture of the surgical neck of the humerus or inferior dislocation of the humerus. it results in weakness of lateral rotation and abduction of the arm.
Radial Nerve Injury
Injury to the radial nerve is caused by a fracture of the midshaft of the humerus.It results in loss of function in the extensors of the forearm, hand, metacarpals, and phalanges. it also results in loss of wrist extension, leading to wrist drop, and produces a weakness of abduction and adduction of the hand.
Musculocutaneous Injury
Injury to the musculocutaneous nerve results in weakness of supination (biceps) and flexion (biceps and brachialis) of forearm and loss of sensation on lateral side of forearm
Median Nerve Injury
Injury to the median nerve may be caused by a supracondylar fracture of the humerus or a compression in the carpal tunnel. It results in loss of pronation, opposition of the thumb, and flexion of the lateral 2 interphalangeal joints and impairment of the medial 2 interphalangeal joints. Waisting of the thenar eminence results in ape hand.–or Benedictine hand which is similar to claw hand but presents upon attempted flexion of the fingers.
Injury to Ulnar nerve
Injury to the ulnar nerve is caused by a fracture of the medial epcondyle and results in claw hand–ring and little fingers are hyperextended at MP joints and flexed at IP joints.It results in loss of abduction and adduction of the fingers and flexion at the MP joints because of loss of dorsal and palmar interossei and medial 2 lumbricals. Hypothenar eminence is wasted and adductor pollicis is lost.
True Claw
Is caused by damage to the lower roots which causes damage to the lower roots which causes damage to radial, median, and ulnar nerves. This messes up all lumbricals and interossei, causing inability to fully extend the digits.
Erb’s Palsy
loss of abduction, flexion, and lateral rotation of the arm,
