The musculocutaneous nerve is part of a network of nerves called the brachial plexus. It serves the bicep muscles as well as the skin on the side of the forearm. The brachial plexus is a major arrangement of nerve fibers that runs from the spine, below the fifth cervical vertebrae in the neck, to the first thoracic vertebrae in the middle of the back. The musculocutaneous nerve continues through the neck and armpit area, to terminate in the arm.
A nerve is a fibrous bundle that transmits impulses and sensations from the spinal cord or brain to the muscles. Large nerves facilitate both motor and sensory functions, while small nerves accomplish either one or the other. The musculocutaneous nerve provides both sensory and motor function to the muscular groups it connects. In the lower arm, however, its function is merely sensory. As it approaches its end, this nerve becomes the lateral cutaneous nerve of the forearm.
Damage to the musculocutaneous nerve can be caused by compressing, stretching, or severing it. Minor damage can cause weakness in the bicep muscle and an inability to flex the arm. The patient may also feel some numbness in the elbow area. If this particular nerve is severed, it will not cause a great amount of damage. At worst, the patient will lose sensation to a small strip of skin and have difficulties bending and straightening the arm.
A nerve can become pinched, or compressed, when a patient with a skeletal or joint problem stretches the affected area. Another frequent location for compression is the point at which a nerve leaves the spinal cord, through the spinal column and vertebra. Depending on where it is pinched, and at what root, a patient with a pinched nerve can experience a variety of symptoms like numbness, tingling, and burning.
The cervical spine, located in the neck, is comprised of seven discs and seven vertebrae, called C1 through C7. Each nerve is rooted in the spinal cord at different discs. The nerve roots for the musculocutaneous nerve are located at C5, C6, and C7. A pinched nerve at C5 may cause difficulty flexing the bicep. At C6, a pinch may cause weakness in the arm and thumb, which can be accompanied by numbness. A pinch at C7, and the entire arm down to the middle finger may experience numbness.
The carpal tunnel is a space in the wrist where the tendons and median nerve run through to the fingers. Carpal Tunnel Syndrome is caused by nerve compression in the wrist area. It can be difficult for doctors to isolate where a nerve is being compressed, pinched, or otherwise irritated. The musculocutaneous nerve, for instance, can become caught at the elbow joint and some symptoms can be easily mistaken for Carpal Tunnel Syndrome.