Bone Cyst of the Spine
A bone cyst of the spine is a fluid-filled cavity that develops within a vertebra or, less commonly, within nearby spinal structures. Most spinal bone cysts are benign and slow-growing, and many are discovered incidentally during imaging performed for unrelated reasons. The most recognized types include simple (unicameral) bone cysts and aneurysmal bone cysts, the latter of which may behave more aggressively and require closer evaluation. Symptoms vary depending on the cyst’s size, location, and effect on nearby bones, nerves, or the spinal cord.
What is it?
A bone cyst is a fluid-filled cavity that forms within bone. In the spine, these cysts most commonly arise within the vertebral body or the posterior elements, which include the pedicles, laminae, and other structures located behind the spinal canal.
Most spinal bone cysts are benign, meaning they are not cancerous. However, their appearance on imaging can sometimes resemble other bone lesions, making careful evaluation important.
The two most common true bone cysts involving the spine are simple bone cysts and aneurysmal bone cysts.
Simple bone cysts, also known as unicameral bone cysts, are benign cavities filled with fluid. They are more common in children and young adults and only occasionally involve the spine.
Aneurysmal bone cysts are expansile lesions composed of blood-filled spaces separated by thin connective tissue walls. Although benign, they can grow rapidly, weaken surrounding bone, and occasionally compress nearby nerves or the spinal cord. On MRI, aneurysmal bone cysts often display characteristic fluid-fluid levels that help distinguish them from other lesions.
Several other cyst-like findings may also occur in or around the spine. These include:
• Facet joint synovial cysts, which arise from degenerative facet joints and may compress nearby nerves
• Tarlov (perineural) cysts, which develop along sacral nerve roots and are often incidental findings
• Degenerative cystic changes associated with spinal arthritis or disc disease
• Cystic changes associated with fractures, infection, or other benign and malignant bone lesions
Many spinal bone cysts cause no symptoms and are discovered incidentally during MRI or CT scans performed for unrelated concerns.
When symptoms occur, localized back or neck pain is the most common complaint. Larger cysts may weaken the vertebra, create spinal instability, or extend into the spinal canal and neural foramina where nerves travel. In these situations, patients may experience:
• Radiating arm or leg pain
• Numbness or tingling
• Weakness
• Gait or balance problems
• Reduced mobility
In rare cases, a weakened vertebra may fracture through the cyst, causing sudden severe pain.
MRI of the spine is the preferred imaging test because it provides detailed information about the cyst’s contents, surrounding bone marrow, nearby nerves, and the spinal cord. MRI can often identify characteristic features that help narrow the diagnosis.
CT imaging is especially valuable for evaluating the integrity of the vertebra, determining whether the lesion has weakened the bone, and assessing fracture risk.
X-rays may reveal an expansile or lytic lesion but are generally less sensitive than MRI or CT.
When imaging findings are atypical or uncertain, biopsy may be recommended to confirm the diagnosis and exclude other conditions.
Important to Know
Treatment depends on the type of cyst, its location, its effect on surrounding structures, and whether symptoms are present.
Small asymptomatic cysts are often monitored with periodic imaging to confirm stability.
When intervention is needed, treatment options may include:
• Image-guided aspiration or drainage
• Sclerotherapy to shrink the cyst
• Selective arterial embolization for vascular lesions such as aneurysmal bone cysts
• Surgical removal of the cyst
• Bone grafting to strengthen weakened vertebrae
• Spinal stabilization procedures when structural integrity is compromised
Aneurysmal bone cysts and other larger spinal lesions are often managed by specialists experienced in spine tumors and tumor-like conditions.
Because certain infections, tumors, and other bone abnormalities can mimic cysts on imaging, radiologists interpret imaging findings alongside the patient’s symptoms, examination findings, and medical history.
Follow-up imaging is sometimes recommended to monitor for growth, recurrence, or changes in appearance.
Red flag symptoms include progressive back or neck pain, sudden severe pain after even minor trauma, progressive weakness or numbness, gait or balance difficulty, loss of bowel or bladder control, fever or chills with back pain, or unexplained weight loss. These symptoms require prompt medical evaluation because they may indicate fracture, nerve compression, infection, or another serious underlying condition.