A spinal cyst is a fluid-filled sac that forms near the spinal column or within the spinal canal. These growths are typically benign, but their seriousness varies considerably based on their location and effect on surrounding structures. Many people have spinal cysts and remain completely unaware of them, as they cause no symptoms and are found only incidentally during imaging. However, a cyst can become a serious medical concern if it enlarges and begins to press on the delicate nerves or the spinal cord itself, leading to neurological compression.
Understanding Spinal Cysts: Types and Origins
Synovial and ganglion cysts are often related to the degenerative changes of the spine, particularly in the lumbar (lower back) region. These cysts arise from the facet joints, the small stabilizing joints between the vertebrae, and are a response to joint instability or arthritis. As the joint capsule degenerates, fluid can leak out and form a sac.
Other types, such as arachnoid and perineural cysts, form near the nerve roots or the layers of tissue covering the spinal cord. Perineural cysts, also known as Tarlov cysts, are fluid-filled sacs that typically form around the nerve root sheath, most often in the sacral area at the base of the spine. Arachnoid cysts develop from the arachnoid membrane, one of the three meningeal layers surrounding the spinal cord, and are filled with cerebrospinal fluid. While some cysts are acquired due to trauma, infection, or inflammation, others are thought to be congenital defects that may enlarge over time.
Determining the Severity of a Spinal Cyst
The seriousness of a spinal cyst is determined almost entirely by its effect on the adjacent neural structures, a phenomenon known as “mass effect.” A cyst that is large but not impinging on any nerve roots may be considered non-serious, whereas a small cyst strategically positioned to compress the spinal cord requires immediate attention. Location is paramount, as a cyst in the narrow cervical (neck) or thoracic (mid-back) spine is more likely to cause cord compression than one in the wider lumbar area.
Symptoms that indicate a cyst is causing significant compression include radicular pain, which is pain that radiates along the path of a nerve, such as sciatica. Patients may also experience numbness, tingling, or motor weakness in the limbs corresponding to the compressed nerve. The presence of weakness or clumsiness suggests a more advanced stage of nerve involvement. A particularly serious development is the onset of cauda equina syndrome, characterized by symptoms like new-onset bowel or bladder dysfunction. This condition is a medical emergency and requires prompt intervention to prevent permanent neurological damage.
Diagnostic imaging, typically Magnetic Resonance Imaging (MRI), is used to assess the cyst’s exact size, its fluid content, and its proximity and relationship to the spinal cord and nerve roots. This imaging provides the necessary detail to distinguish between an incidental, asymptomatic finding and a symptomatic cyst that demands active treatment.
Management and Treatment Options
For cysts that are discovered incidentally or cause only minor discomfort, initial management often involves observation with regular monitoring. Conservative treatments like non-steroidal anti-inflammatory drugs (NSAIDs) or physical therapy may be used to manage pain and associated inflammation.
If symptoms are more persistent or severe, minimally invasive interventions may be considered. These procedures often include image-guided steroid injections to reduce inflammation around the nerve root. In some cases, a physician may attempt percutaneous cyst aspiration or drainage to remove the fluid from the sac. While aspiration can provide temporary relief of symptoms, cysts frequently reform or refill because the underlying cause, such as joint instability, remains unaddressed.
Surgical intervention is typically reserved for cases where the cyst causes intractable pain, significant neurological deficit, or signs of spinal cord compression. The most common surgical approach is decompression, which involves removing the cyst (resection) to relieve pressure on the nerve root or spinal cord. If the cyst is associated with significant spinal instability, the surgeon may also perform a spinal fusion to permanently join two or more vertebrae, which helps prevent the cyst from recurring.