Tarlov cysts are fluid-filled sacs that typically form on the nerve roots of the spine, most commonly in the sacral region. They are often small and do not cause issues, frequently discovered incidentally during imaging for other conditions.
Understanding Tarlov Cysts
Tarlov cysts are dilations of the nerve root sheath, occurring within the perineural space and filled with cerebrospinal fluid (CSF). While they can appear anywhere along the spine, the sacral region (S1-S5) is their most frequent location. A distinguishing characteristic is the presence of nerve fibers within the cyst walls. Most individuals with Tarlov cysts remain asymptomatic, with only 5% to 8% experiencing symptoms.
Established Factors in Formation
Several factors contribute to Tarlov cyst formation. One significant theory involves a congenital predisposition, suggesting individuals may be born with a weakness or abnormality in the nerve root sheath. This inherent structural variation could make certain nerve sheaths more susceptible to dilation and fluid accumulation over time.
Trauma to the spine is another established factor implicated in cyst formation. Falls, accidents, or even strenuous activities like heavy lifting can lead to micro-hemorrhages or tears in the nerve root sheath. Such injuries can create a pathway for CSF to leak into the perineural space, initiating or enlarging a cyst.
Increased cerebrospinal fluid (CSF) pressure within the spinal canal is also considered a significant factor. Fluctuations in CSF pressure, which occur naturally with activities like coughing, sneezing, or lifting, can exert stress on the nerve root sheaths. This pressure can force CSF into the weakened perineural space, especially if a one-way valve mechanism is present, allowing fluid to enter but not easily exit. This continuous influx and restricted outflow contribute to the gradual expansion of the cyst.
Emerging Theories and Associations
Beyond the established factors, other theories and associations continue to emerge regarding Tarlov cyst formation. Inflammation around the nerve roots is one such theory, proposing that inflammatory processes within the spinal meninges could lead to fluid accumulation and cyst development. This suggests that an inflammatory response might compromise the integrity of the nerve root sheath, creating conditions favorable for cyst growth.
Degenerative changes in the spine, which occur naturally with aging, are also considered potential contributors. These changes might weaken nerve sheaths over time, making them more vulnerable to the effects of CSF pressure or minor trauma. The gradual wear and tear on spinal structures could predispose individuals to the formation of these cysts.
Emerging research also points to a broader genetic predisposition, extending beyond simple congenital weaknesses. Associations have been observed between Tarlov cysts and connective tissue disorders such as Marfan syndrome and Ehlers-Danlos syndrome. This suggests that underlying genetic factors affecting connective tissue integrity might play a role in the susceptibility to developing these cysts.
From Formation to Symptom Development
While many Tarlov cysts remain asymptomatic, those that do cause symptoms typically do so through enlargement and subsequent compression of adjacent nerve roots. As the cyst grows, often due to a one-way valve effect, it can physically press on the delicate nerve fibers within its walls or on neighboring spinal nerves.
This compression can manifest in various neurological deficits, including pain, numbness, tingling, or weakness in the areas supplied by the affected nerves. For cysts in the sacral region, symptoms might include lower back pain, sciatica-like pain radiating down the legs, or even bowel and bladder dysfunction. In severe cases, the sustained pressure from an enlarging cyst can lead to bone erosion of the surrounding sacral vertebrae.