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Perineural cysts (Tarlov-cysts)

Perineural cysts are relatively common and were first described in 1938 by Tarlov. They are usually localized near the ganglion at the junction of the dorsal nerve root and typically occur in the sacrum, at the level of S2 and S3. They are usually multiple and characterized in that they contain nerve root fibers, which makes them different from the extradural cysts (eg, synovial cysts). The cause of the cysts is unclear. Probably genetic factors play a role, whereby the strength of the dura is weakened at these crossing points and thus a balloon-like bulge as a result of the cerebrospinal fluid pressure can develop. Therefore these are also known as diverticulum. The need for treatment of perineural cysts is controversial. The cysts are often found as an incidental finding in the diagnosis of degenerative spinal disorders. They can vary in size, shape and location . In principle, the perineural cysts can occur in all three spinal regions, ie cervical spine , thoracic spine, lumbar spine and the sacrum. These can be found in the sacrum most often. This may be consistent with the hydrostatic pressure in the cerebrospinal fluid, which is highest at the sacrum. Restrictions in the circulation of the cerebrospinal fluid into the root bags may also play a role. So valve mechanisms may facilitate the influx , but complicate the efflux . The cysts may vary greatly in size. It often occurs due to chronic pressure effect on vertebral and nerve channels to a thinning of the bony structures . If the cysts are located in the spinal canal , then you can also exert pressure on adjacent nerve roots . This also radicular complaints may arise. This means the leg radiating pain according to a nerve root , but it can also be numbness and in very rare cases, paralysis. Thus, the symptoms of perineural cysts can mimic even a herniated disc . However, often the symptoms occur slowly progressive, ie slowly , while the herniated disc rather acute, ie suddenly becomes symptomatic. Even if this is rare, as the pressure slowly rises, and can be done by the time an adjustment to compensation also limits can be exceeded and the cysts are symptomatic.
The medical treatment is therefore considered to clarify whether other causes may be responsible for certain symptoms or whether it is the cyst.

The indication for surgery
exists only in the cases where the radicular complaints match with the root sheath cysts. In these rare cases, the treatment is surgical resection. That means ablation of the cyst (consisting of arachnoid alone or arachnoid and dura). The dura can be gathered by folding after the ablation, either directly or closed with large cysts. Sometimes a resection of the cyst wall is not possible as not only the nerve fibers running along the bottom of the cyst, but in a fan-shaped spread throughout the cyst wall. In such cases, only remains the bony decompression (relief) of the cyst. Other hand, valve mechanisms in the cyst can be removed and the circulation of the cerebrospinal fluid can be improved. This prevents that the cyst develops again.