Bulging neck discs sometimes cause arm weakness.
Given the demands you place on your neck every day, its various parts -- your cervical spine and the soft tissues surrounding it -- are surprisingly durable. Repetitive flexing, extending, bending and twisting can eventually take their toll. And if you injure your neck, its normally resilient structures may begin to fail. When aging, overuse or injury alters the mechanical integrity of your cervical spine, any number of symptoms may develop. Depending on the structures are involved, you could experience weakness, stiffness or pain in your neck, or develop unusual sensations or weakness in either or both arms.
Nerves Control Function
The tasks required of your cervical spine -- supporting and moving your head and protecting your spinal cord -- are made possible by its segmented, compression-resistant structure. Your cervical spine has 7 stacked bony vertebrae, each of which is separated from its upper and lower neighbors by a tough cartilage disc. Your spinal cord, which runs through a canal in the spinal bones, is protected by bony archways projecting backward from each vertebra. At each level of your cervical spine, a nerve emerge from each side your spinal cord and courses outward to serve your shoulders, arms, hands and parts of your upper chest and back. These cervical nerves control the muscular and sensory functions of your upper extremities.
As it emerges from your spinal cord, a cervical nerve must pass through a small hole, or foramen, formed by indentations in the bony arches from adjacent vertebrae. Due to aging or injury, these holes may narrow and potentially crowd the exiting cervical nerves. Because the openings for your cervical nerves lie just behind the discs between your vertebrae, a backward-bulging disc could further compromise a cervical nerve as it passes through its foramen.
When a cervical nerve is pinched in this way, you may experience weakness, pain, numbness or other unusual sensations in your arm or hand. According to a 2010 review in "American Family Physician," 70 percent of people reporting such symptoms have arthritis, bulging discs or both in their cervical spine.
Although a bulging cervical disc can cause arm weakness, your doctor will consider other possibilities when evaluating the cause of your symptoms. Nerve entrapment syndromes -- such as carpal tunnel or cubital tunnel syndrome -- spinal cord compression due to bone spurs, tumors in or around the spine, or neurological disorders such as multiple sclerosis, can provoke symptoms similar to a bulging disc. A 2011 review in the "HSS Journal" demonstrated that many of these conditions can be ruled out during a thorough physical examination. Nevertheless, many doctors order imaging studies -- usually x-rays and an MRI -- to evaluate people who have arm weakness.
Forty to 90 percent of people with compressed cervical nerves improve without surgery, but recovery can take months. Antiinflammatory medications, painkillers, muscle relaxers, physical therapy and traction are all sometimes useful for those with cervical nerve compression. Epidural steroid injections -- injections of antiinflammatory medications into the area around the compressed nerve -- may also be recommended for some people.
In the "American Family Physician" review, Dr. Jason Eubanks -- an orthopedic surgeon at Case Western Reserve University School of Medicine -- notes that chiropractic manipulation has not been proven effective for cervical nerve compression. Furthermore, such treatment may worsen your symptoms and could cause spinal cord injury.
People who have profound arm weakness due to a compressed cervical nerve are usually referred to a surgeon for an immediate evaluation. Similarly, your doctor may send you to a surgeon if your arm weakness is mild but persists for more than 6 weeks despite therapy. Surgery is recommended to relieve pressure on a nerve that might sustain permanent damage if the pressure is not alleviated.