Consider the possible effects of injury to the upper and lower trunks of the brachial plexus.?

Answer 1

Upper Trunk injury:-
Causes:
Undue separation of head from shoulder dude to a birth injury, fall on the shoulder or during anaesthasia.
Effects:
Erb's paralysis; which involves paralysis of the biceps, deltoid, brachialis, brachioradialis, supinator, supra and infraspinatus muscles. This causes the arm to hang by the side in a position known as 'Policeman's tip hand'. Abduction at shoulder, flexion and supination at elbow are lost.

Lower Trunk injury:-
Causes:
Undue abduction of arm.
Effects:
Klumpke's paralysis; which involves paralysis of intrinsic muscles of the hand and ulnar flexors of the wrist and fingers. This causes the hand to resemble a claw, that is, there is hyperextension at the metacarpo-phalangeal joint and flexion at the interphalangeal joints. Sensation is lost over a narrow zone along the ulnar border of the forearm and Horner's syndrome (ptosis, miosis, loss of ciliospinal reflex) is observed.

Hope this helps.
Cheers!

Answer 2

The brachial plexus is a network of nerves that conducts signals from the spine to the shoulder, arm, and hand. Brachial plexus injuries are caused by damage to those nerves. Symptoms may include a limp or paralyzed arm, lack of muscle control in the arm, hand, or wrist, and lack of feeling or sensation in the arm or hand. Although injuries can occur at any time, many brachial plexus injuries happen during birth: the baby's shoulders may become impacted during the birth process causing the brachial plexus nerves to stretch or tear. There are four types of brachial plexus injuries: avulsion, the most severe type, in which the nerve is torn from the spine; rupture, in which the nerve is torn but not at the spinal attachment; neuroma, in which the nerve has tried to heal itself but scar tissue has grown around the injury, putting pressure on the injured nerve and preventing the nerve from conducting signals to the muscles; and neuropraxia or stretch, in which the nerve has been damaged but not torn. Neuropraxia is the most common type of brachial plexus injury.
It is very difficult to differentiate between lower and upper trunk injuries.