Anatomy lab muscles

Question

The lateral cord of the right brachial plexus of a right handed 35 yr old male is completely severed.

Discuss the clinical presentation of the patient in terms of muscle function of the right upper extremity. Be specific about what muscles might be affected and to what extent. If you wish to add the sensory deficits expected as well, that is fine.

Answer 1

The brachial plexus is a complex connection of nerves, but what is satisfying about these is that each area corresponds with a certain end nerve, or muscle it acts on. The lateral cord is in the latter half of the brachial plexus and sits superiorly. It is primarily derived from C5 and C6, with some C7 function. If you google a dermatomal/myotomal distribution, you will see what it supplies.

Ultimately, the person will basically lose the entirity of the function of their lateral pectoral and musculocutaneous nerves. The lack of the musculocutaneous nerve means that this mans biceps muscles will be non functional. This includes the coracobrachialis, biceps brachii, and some of the brachialis; he also will lose some sensation on his lateral forearm.

The loss of the lateral pec nerve means that the pectoralis major will loss its motor function.

He will lose some function of the median nerve (lateral side) which will mean he will have some issues in his rest, but might be able to make up for the loss of function. Notably, he will likely lose motor function of the flexor carpi radialis.

In summary, this man will like lose his biceps and pec major functions, AKA two of the favorite bodybuilding muscles! (and very functional)