The spinal cord is divided into four segments: cervical, thoracic, lumbar and sacral. Together, they make up a vital part of the body's central processing nervous system; injury to the spinal cord can be grave and sometimes fatal. The cervical part of the spinal cord lies in the neck. Injuries occurring at the second cervical vertebrae, known as C2, manifest through a particular constellation of symptoms and signs.
As stated by the University of Alabama at Birmingham Spinal Cord Injury Information Network, an injury in the upper cervical region of the spinal cord—vertebrae C1 through C3—will cause complete paralysis of breathing muscles. This occurs because all the nerve signals sent by the brain originate at a higher level. An injury at C2 will interrupt the nervous system's signals to the muscles responsible for breathing. The muscles paralyzed by such an injury include the diaphragm, the chest and abdominal muscles, and the neck muscles. If the injury is complete and the spinal cord is completely transected at this level, the patient will lose the ability to breathe spontaneously and will need a ventilator.
The Merck Manuals Online Medical Library notes that injury of the spinal cord at C2 will result in complete or partial paralysis of all four limbs and trunk muscles. The muscles comprising the anal and bladder sphincters are also paralyzed causing the patient to lose voluntary control over urination and defecation. If the spinal cord is severely injured, the patient could remain paralyzed for life. If the injury is partial, however, the patient may regain some movement, particularly of the trunk muscles.
The nerves responsible for delivering sensation also pass through the spinal cord. Each spinal cord segment gives sensory supply to an area of the skin called a dermatome. All sensations are relayed to the brain via the spinal cord in order to provide feeling.
According to the American Spinal Injury Association, C2 provides sensory supply to the area over the back of the head and the top part of the neck. Injury at the C2 level will cause the patient to be totally deprived of sensations below that level because of the interruption of the pain pathway and the nerve signals going to the brain.