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Tarlov Cysts Overview Louise A. Schmidt, D.O.

Tarlov Cysts Overview
Louise A. Schmidt, D.O.
Member, Tarlov Cyst Support Group

I. Function of Tarlov cysts
Tarlov cysts are cerebral-spinal fluid filled 'perineurial' cysts along the sacral and lower lumbar nerve roots. Spinal arachnoid cysts are similar cysts along the cervical, thoracic and upper lumbar spinal nerve roots. Currently "Tarlov cyst" is often used to describe either cyst.
Symptomatic cysts trap nerves, particularly the axons of sensory nerves. Any increase in pressure in or on the cysts will increase symptoms and nerve damage. This is NOT the same as sore muscles that just need to get into condition. Any exercise that increases symptoms, such as bicycling or flexion, must be avoided. Exercises that do not increase symptoms are to be encouraged.
The body maintains homeostasis: balance. Fast walking or/and pain raise heart rate, raise blood pressure, raise CSF pressure. When one is upright, that means that cysts can act like water balloons and increase in size, causing more pressure, more symptoms. Exercise plus pain means adding (or multiplying) size and pressure and symptoms.
Sitting applies compression pressure externally from below on everything in the abdomen: cysts, nerves, bowel, etc. While in a gravity dependent position (sitting or standing), cysts tend to not empty, so any pressure is transferred to whatever they are already pressing on. This is probably why full bowel or bladder or menses can cause symptoms to increase. Bending while sitting just adds more pressure from above, trapping cysts between two sources of pressure. Anterior cysts ( with pudendal nerve entrapment) may react more than posterior ones, but posterior cysts also respond (foot pain, leg numbness, muscle weakness, etc.).
If TC patients sit too long, (depending on the condition and location of their cysts) they can develop a lot of numbness, organ contracting/cramping, prolonged Valsalva reactions, and increased pain. I conclude that homeostasis is thrown off by the effect of the pressure of the cysts on the parasympathetic and sympathetic nerves that, among other things, help regulate homeostasis. Sometimes lying on ones side with legs stretched straight relieves the pressure and gradually the symptoms resolve.
II. Structure/Formation of Tarlov Cysts: Function-Based Description
Think of the arachnoid fibers as a spider web, complete with holes, surrounded by CSF which flows under (sub-arachnoid space) and through the spider webs (arachnoid layer, sub-dural space), which suspend the nerve fibers in the middle of the protective CSF . The dura is the tougher protective outer cover that keeps the CSF in. The pia and the arachnoid started from the same embryonic cells, even though the pia sticks to the nerves and the arachnoid sticks to the dura with structural pia-arachnoid trabeculae (crossbeams) extending between them.
Then along comes a spider having a bad day. Instead of making a structurally strong web with holes, it makes a bag/balloon that does not have holes, but like a cul-de-sac, one entrance, no flow-through. The CSF flows in. If a ball-valve exists, the fluid does not come back out. And the bag or balloon is not structurally sound, does not keep the nerve fibers as safe from being bumped as the spider web pattern does. Sometimes this spider has a really bad day and even includes passing nerve fibers (pia-arachnoid mishap in formation?) in the wall of the balloon.
I do not know yet what causes the "spider" to have a bad day while forming the arachnoid layer, probably before birth. But it may be that arachnoid villi, which normally allow the exiting of CSF from the central nervous system through the dura to the epidural space, is where the "bad day" sometimes happens. The CSF flows into the villi instead of through, forming the balloons. This would also explain how it manages to push itself outside the dura. One of the areas with a lot of CSF is the cisterna lumbar, which extends down to S2. The villi also must have a "valve" of some kind to regulate the normal exiting of CSF...

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