Cervical spondylolisthesis is a spinal condition where a vertebra in the neck slips forward over the bone beneath it. This misalignment can be visualized as a stack of blocks where one has shifted out of position. The cervical spine, which consists of the first seven vertebrae in the spinal column, provides support for the head and allows for a wide range of motion. When a vertebra displaces, it can narrow the spinal canal, potentially affecting the spinal cord and surrounding nerves.
Causes and Risk Factors
The most common cause of cervical spondylolisthesis is the natural aging process. Over time, the intervertebral discs and facet joints, which connect the vertebrae and allow for movement, can degenerate. This process, similar to spinal osteoarthritis, weakens these components, leading to instability that allows a vertebra to slide forward, particularly in adults over 50.
Traumatic events can also lead to this condition. A direct injury to the neck from a fall or car accident can fracture a part of the vertebra called the pars interarticularis, causing it to slip. Repetitive stress, often seen in athletes, can also cause these fractures and lead to what is known as isthmic spondylolisthesis.
In some instances, the cause is congenital, where an individual is born with malformed or thinner vertebrae that are more prone to slipping. Other less frequent causes include instability from a previous spinal operation, or pathologic spondylolisthesis, which results from underlying conditions like bone diseases or tumors that weaken the vertebral structure. Key risk factors include a family history of the condition, participation in high-impact athletics, and the presence of other spinal conditions like scoliosis.
Symptoms and Grading
The experience of cervical spondylolisthesis varies, and some people remain entirely asymptomatic. When symptoms appear, they often include persistent neck pain, stiffness, and muscle spasms. This discomfort can radiate from the neck into the shoulders or down the arms, a condition known as radiculopathy. This radiating pain is often accompanied by sensations of numbness, tingling, or weakness in the arms and hands. Headaches originating from the neck are also a common complaint.
More significant vertebral slippage can lead to compression of the spinal cord, a condition called myelopathy. This can produce more severe symptoms, including difficulty with fine motor skills in the hands, problems with walking and balance, and changes in posture. In rare cases, individuals may experience a loss of bladder or bowel control, which signals significant nerve compression and requires immediate medical attention.
To classify the severity of the slip, clinicians use the Meyerding classification system, which grades the percentage of forward displacement based on imaging studies.
- Grade I: A slippage of 1% to 25%.
- Grade II: A slip of 26% to 50%.
- Grade III: A slip between 51% and 75%.
- Grade IV: A displacement of 76% to 100%.
- Grade V: Known as spondyloptosis, where the vertebra has completely slipped off the one below it.
Individuals with lower-grade slips (I and II) may have mild or no symptoms, while those with higher-grade slips (III and above) are more likely to experience significant pain and neurological symptoms.
Diagnosis Process
The diagnosis of cervical spondylolisthesis begins with a clinical evaluation. A physician will discuss the patient’s medical history and symptoms, including when they started and what activities make them worse. This is followed by a physical examination where the doctor assesses the neck’s range of motion, muscle weakness or spasm, and tests reflexes and sensation in the arms and hands to identify any neurological deficits.
Imaging tests are used to confirm the diagnosis and evaluate the extent of the condition. Standard X-rays of the cervical spine, taken from the side, help visualize the alignment of the vertebrae and confirm the degree of slippage. The doctor may order flexion-extension X-rays, taken while the patient bends their neck, to assess the spine’s stability.
For a more detailed view, a magnetic resonance imaging (MRI) scan is often recommended. An MRI provides clear images of soft tissues like the spinal cord, nerves, and intervertebral discs, allowing the doctor to see if they are being compressed. In some cases, a computed tomography (CT) scan may be used for a more detailed picture of the bones and any associated fractures.
Treatment Approaches
For most individuals with low-grade slips and mild symptoms, treatment begins with conservative, non-surgical methods to manage pain and improve function. Physical therapy is a key part of this, focusing on exercises to strengthen the neck and core muscles to help stabilize the spine. Therapists also guide patients on activity modification and proper posture to reduce stress on the neck.
Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) may be recommended to reduce pain and inflammation. For more persistent pain, a physician might suggest epidural steroid injections. In this procedure, medication is delivered directly into the space around the spinal nerves to decrease inflammation and alleviate radiating arm pain.
Surgical intervention is reserved for cases where conservative treatments fail, or when a high-grade slip causes significant spinal instability or progressive neurological symptoms. The goals of surgery are to decompress the nerves and stabilize the spine. Decompression surgery involves removing bone or disc material that is pressing on the spinal cord or nerve roots. Following decompression, a spinal fusion is performed to permanently stabilize the affected vertebrae. In a fusion, the surgeon joins two or more vertebrae with bone grafts and hardware, creating a single, solid bone to eliminate motion and prevent further slippage.