Definition from Practical Pain - generalized disk displacement more than 50% (Note spelling and Tina's comments) xray findings (ref 7) Gel-filled discs cushion the spaces between the cervical vertebrae, the bones that protect the spinal cord in the neck area. If the disc is damaged, it can bulge or herniate into the spinal canal and compress the nerve closest to the defect. The disc may bulge because of an injury or, more commonly, because of natural aging processes that dehydrate the disc and damage the vertebrae.
The cervical nerves sends electrical impulses to the neck, shoulders, arms, hands and fingers. The signs and symptoms of a bulging disc in the neck depend on which of the cervical nerves is affected.
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Most cases of cervical disc herniation can be diagnosed in the doctor's office, although sometimes magnetic resonance imaging -- MRI -- is needed, according to Dr. Mark Greenberg, author of "The Neurology Handbook, 7th ed." (Ref. 2, p. 461) In 69 percent of cases, the seventh cervical nerve -- C7 -- is compressed, affecting the triceps muscle at the back of the upper arm, the forearm, the second and third fingers, and all of the fingertips.
Dr. Greenberg notes that 19 percent of herniated cervical discs compress C6, the sixth cervical nerve, affecting the biceps muscle, the forearm, and the thumb. In 10 percent of the cases, compression of the C8 nerve affects the hand, and in 2 percent of cases, pressure on C5 affects the deltoid muscle of the arm, as well as the shoulder.