Spinal hemangiomas are common, benign vascular lesions that originate within the bones of the spine, known as the vertebrae. They are composed of an overgrowth of blood vessels and bone tissue, and they are often found incidentally during imaging performed for unrelated conditions. While the vast majority of these lesions remain stable and asymptomatic, their growth rate is highly variable and depends significantly on the specific type of hemangioma. Understanding the classification and nature of the lesion is necessary to determine its potential for growth and the risk of causing symptoms.
Classification of Spinal Hemangiomas
Spinal hemangiomas are broadly divided into types based on their location and characteristics. The most common type is the typical vertebral hemangioma, which is confined to the bone and is estimated to occur in about ten percent of the population. These lesions are generally slow-growing and are composed of thin-walled vessels interspersed with a high content of fat within the vertebral body.
Atypical or aggressive hemangiomas represent a much smaller fraction, accounting for approximately one percent of all spinal hemangiomas. These types are characterized by less fatty tissue and a higher vascular component, which makes them more active and prone to expansion. Aggressive lesions can extend outside the bone, involving the posterior elements of the vertebra or creating a soft tissue mass that encroaches on the spinal canal. This extra-osseous extension is the primary mechanism by which an aggressive hemangioma causes neurological symptoms.
Growth Patterns and Variability
The typical vertebral hemangioma is generally a quiescent lesion, meaning its growth is extremely slow or has completely stopped. Studies tracking these common lesions over several years indicate a very low average growth rate, often less than three millimeters over a ten-year period. For many individuals, growth ceases entirely once they reach skeletal maturity, and the lesion is considered stable.
In contrast, the aggressive subtype exhibits a noticeably faster growth pattern, which is usually defined by its expansion outside the vertebral body. This expansion over months to a year can cause the lesion to impinge on surrounding structures, leading to neurological issues. The growth is driven by the proliferation of abnormal blood vessels, which can cause bone destruction and soft tissue mass formation. Any rapid, documented expansion leading to symptoms marks a significant change in the lesion’s behavior.
Factors Influencing Symptomatic Progression
A previously stable hemangioma can become symptomatic or accelerate its growth due to internal and external factors. Hormonal influences are a significant internal factor, as these lesions are more common in females and are known to be stimulated by increased levels of hormones like estrogen and progesterone. This explains why an existing hemangioma may accelerate its growth or become symptomatic during pregnancy, where hormonal and hemodynamic changes are substantial.
Physical trauma or increased mechanical stress can also play a role in progression, particularly in the lower back where axial loading is high. While trauma does not cause the hemangioma, it can lead to micro-hemorrhages or localized inflammation within the lesion, causing it to expand and become painful. Symptomatic progression often means expansion that results in nerve compression or pathological fracture. A lesion with a low-fat and high-vascular content is inherently more prone to active progression and symptomatic behavior.
Monitoring and Treatment Approaches
Monitoring for stability and progression is primarily conducted using Magnetic Resonance Imaging (MRI), which is highly effective for assessing the lesion’s size and its relationship to the spinal cord and nerves. For asymptomatic hemangiomas identified incidentally, physicians typically recommend a conservative approach with periodic imaging follow-up to confirm stability. Changes in lesion size, the development of significant pain, or the onset of neurological deficits are the primary triggers for intervention.
Several treatment modalities exist for symptomatic or aggressive lesions, often used in combination. Percutaneous vertebroplasty, which involves injecting bone cement into the vertebral body, is a common option for stabilizing the bone and alleviating pain in lesions confined to the vertebra. Radiation therapy can be used to shrink the vascular component of the hemangioma and is often employed for painful lesions or those causing mild compression. For aggressive hemangiomas causing severe spinal cord compression or neurological deficit, surgical resection is typically required to remove the mass and decompress the neural structures.