From the Guidelines
A perineural cyst, also known as a Tarlov cyst, is a fluid-filled sac that forms on the covering of a nerve root near the spine, most commonly in the sacral region at the base of the spine. These cysts develop when cerebrospinal fluid becomes trapped within the nerve root sheath. According to the study published in the Journal of the American College of Radiology 1, Tarlov cysts are characterized by deep cystic masses communicating with sacral foramina. Most perineural cysts are small and cause no symptoms, but larger cysts can compress nearby nerves, resulting in pain, numbness, tingling, or weakness in the lower back, buttocks, legs, or perineal area. Some patients may experience bladder or bowel dysfunction in severe cases.
Key Characteristics of Perineural Cysts
- Fluid-filled sacs that form on the covering of a nerve root near the spine
- Most commonly found in the sacral region at the base of the spine
- Can be characterized by deep cystic masses communicating with sacral foramina on ultrasound, as noted in the study 1
- May cause symptoms such as pain, numbness, tingling, or weakness in the lower back, buttocks, legs, or perineal area due to compression of nearby nerves
Diagnosis and Treatment
- Diagnosis typically involves MRI imaging, which can clearly show these fluid-filled structures
- Treatment depends on symptom severity - asymptomatic cysts generally require no treatment, while symptomatic cysts might be managed with pain medications, physical therapy, or steroid injections
- In cases with significant neurological symptoms, surgical options include cyst drainage, removal, or fibrin glue injection to prevent refilling, although the exact cause of perineural cysts remains unclear, and may result from inflammation, trauma, or congenital factors affecting the nerve root sheaths.
From the Research
Definition of Perineural Cyst
- A perineural cyst, also known as a Tarlov cyst, is a cerebrospinal fluid-filled growth that develops at the intersection of a dorsal root ganglion and posterior nerve root 2.
- It is a lesion in the form of fluid-filled sacks, usually located within the nerve root sheath at the posterior root of a spinal nerve, whose wall is formed by endoneurium, peripheral nerve fibers, and ganglion cells, and areolar tissue 3.
- Perineural cysts are typically asymptomatic and incidental findings during routine spine imaging, but they can cause symptoms such as pain when they put pressure on the nerve and neighboring nerve roots 3.
Characteristics of Perineural Cysts
- The frequency of perineural cyst occurrence is estimated to be between 1.5-13.2%, with a significant majority occurring in women 3.
- Cyst development may be the result of ischemia, hemorrhage, inflammation, or trauma 3.
- Perineural cysts are usually asymptomatic, but in approximately 1/4 of cases, they can cause symptoms such as pain due to pressure on the nerve and neighboring nerve roots 3.
Treatment of Perineural Cysts
- Treatment options for symptomatic perineural cysts include conservative treatment (e.g., analgesics, rehabilitation, cyst puncture) or surgery (usually laminectomy) 3.
- Microsurgical cyst fenestration seems to be a safe and effective option for symptomatic relief in patients with perineural cysts 2.
- Other treatment options, such as epidural steroid injections, have also been reported to be effective in managing symptoms associated with perineural cysts 4, 5, 6.