Cervical Disc Herniation
One type of weight-bearing joint in the human spine is the intervertebral disc. They are located between the vertebrae and consist of soft cartilage surrounded by a fibrous sheath called the annulus. In the center of all discs is a semi-gelatinous cartilage, oblong in shape, called the nucleus. The nucleus functions similarly to a ball bearing, acting as an axis for movement in all directions.
What Is It?
Although many patients are familiar with the concept of degenerative disc disease, meaning the loss of fluid and height of a disc as an age-related change, discs can also undergo a derangement of their internal architecture in the form of migration of the nucleus out of its normal position, usually backwards. If the nucleus migrates only to the point of mild pressure against the back of the disc annulus, the clinical result can manifest itself as neck pain only. This is because the discs have pain nerve endings that allow us to feel them and experience pain, just as one can experience pain from any other joint in the body. If, however, the nucleus extends far enough backwards to come into contact with one of the cervical nerve roots (that continue into the upper extremities), the additional symptom of nerve pain into the upper extremity occurs. The medical term for this is “radiculopathy”, and it can be associated with impairment of nerve function, such as numbness, tingling, and loss of strength. Disc herniations are further classified by location in the spinal canal (central, left or right). Herniations are further described by size, and whether the annulus remains intact (a disc protrusion), ruptured (extruded), or can consist of a free fragment of cartilage no longer in continuity with the disc space from which it arose (sequestrated). In the cervical spine, unlike the lumbar spine, within the canal is the spinal cord itself In the lumbar spine, the spinal cord typically ends at about the level of the first lumbar vertebra, meaning that most lumbar herniations affect the lumbar nerve roots emanating from it. With a cervical central disc herniation of sufficient size, therefore, pressure against the spinal cord can occur, as opposed to individual exiting nerve roots. This, in turn, can result in any combination of pain, numbness/tingling, and weakness affecting all four extremities, as well as symptoms of unsteadiness of gait and loss of dexterity in the hands, termed “myelopathy”.
The natural history (what happens even if untreated) of an acute cervical disc herniation is generally favorable in the majority will spontaneously shrink in size through healing. This process of healing, however, usually takes 2-3 months. A disc protrusion (intact annulus) is amenable to physical therapy, including neck traction and extension exercises (arching the neck) to apply a force that can in essence “push it back in”. If such exercises are effective, the disc protrusion is termed “reducible”, and the patient experiences relief of arm pain with extension movement While waiting to see if a herniation will heal, the patient has to avoid or minimize aggravating activities that typically include bending, twisting and lifting, limit sitting, and sit/lie with good cervical support and posture. Prescription medications may be necessary, and the symptoms can be lessened by spinal injections of a mixture of steroid and local anesthetic generally called “epidural steroid injections”, although injections will not make the herniation smaller.
If arm pain persists to a significant degree, despite appropriate time and treatment, then the patient can choose to undergo surgery. The exception would be the patient with intolerable pain or with neurologic deficits, especially weakness, which might prove irreversible. Patients with spinal cord compression who have significant neurologic symptoms, especially when progressive in nature, are very likely to require surgery. In such instances, surgery may be indicated more urgently.The standard of care, then, is to remove the disc from the front of the neck. Once removed in its entirety, the absence of a disc between the vertebrae necessitates its replacement with a structural bone graft, or alternatively, an artificial disc. We do not yet have sufficient long-term data to prove the superiority of artificial discs over fusion, and for this reason, few insurance companies will authorize them. The default choice, as a result, is fusion, termed “anterior cervical discectomy and fusion” or “ACDF”. Most surgeons accompany an ACDF with anterior plating to increase fusion rates and minimize the risk of graft fracture, dislodgement, subsidence and loss of normal cervical alignment. Most surgeons also use cadaver bone, called an allograft, over the patient’s own bone, termed autograft, given that fusion rates are essentially the same, and to avoid donor site problems. A one-level ACDF can be done in a couple hours as an outpatient procedure or as an overnight stay. Postoperatively, a neck collar is used to limit motion and facilitate fusion until the graft is healed. One level ACDF’s usually heal in 6 weeks, and two or more levels in about eight. Restrictions include limited neck motion, no lifting more than 10 lbs., and avoidance of car travel for 4 weeks. The success rate for relief of arm pain is 90% or greater.