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.
Location of Signs and Symptoms
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.
Typically, the first symptom of a herniated cervical disc is pain on 1 side of the neck. Often, the person first notices the pain upon waking in the morning, with no history of an injury. (Ref. 2, p. 461) The person may also have pain in the shoulder blade on that side, as well as in the arm, hand and fingers. Some people describe the pain as sharp, shooting or burning while others may perceive it differently.
The pain generally makes it difficult for the person to move the neck freely, and it may feel worse after bending the neck backwards. Standing, sitting, sneezing and coughing may also worsen the pain.
Changes in Sensation
Because the herniated cervical disc compresses the nerve root below it, people typically experience unusual sensations called paresthesias along the route of the nerve. Depending on the particular nerve affected, the person may feel numbness or tingling in the shoulder, arm or fingers of the affected side. (Ref. 2, p. 461) In milder cases, however, there may be no sensory changes at all because the nerve still functions properly.
Muscle Weakness and Reflexes
A herniated disc can cause muscle weakness and diminished reflexes in the arm and fingers. If the C7 nerve is compressed, the person may have difficulty extending the forearm, and the triceps muscle reflex may be diminished. (Ref. 2, p. 461) Compression of the C6 can cause weakness when the person flexes the forearm and diminished reflexes in the biceps and brachioradialis muscles. The fingerjerk reflex is diminished and hand movements are affected when the C8 nerve is compressed. The least common situation, compression of the C5 nerve, causes weakness and diminished reflexes in the deltoid muscle.
Most people with a bulging cervical disc recover without the need for surgery. Rarely, however, some people's conditions worsen despite conservative treatment of rest, pain medication and physical rehabilitation. Immediate medical attention is needed if both arms or legs become severely weakened and the person loses control of their bowels and bladder.