What Are They?
Tarlov cysts are extensions of dura that contain cerebrospinal fluid - it's the neural equivalent of a ganglion from a synovial joint.
Tarlov cysts usually occur in the sacral area, can erode bone and are more common in women.
Not all produce problems but some slowly grow to compress and irritate the nerve root; produce neuropathic pain, radiculopathy and, in the more serious cases impair bladder, bowel and sexual function.
Often it is a wait-and-see approach and work around symptoms.
Medical treatment can produce transient relief with injections of steroids and, if necessary, microsurgery and CSF shunts.
I had a patient - female in her early 50s - come in whose main concern was aches and pains and burning feelings in her back, pelvis and hip.
The problem came gradually over the preceding 10 years and was slowly becoming less manageable. Her weight was stable and she was not taking any medications and was otherwise well. She was not limited in any of her daily activities but was bothered by her pain.
The pains were non-mechanical in that they were not provoked or eased consistently with positions, spinal movements or daily activities.
Physical examination showed nothing of note: normal spinal movement for her age and gender, no provocation of pain with movement and neurodynamic and neurological tests were normal.
One of the cornerstones of clinical reasoning is marrying subjective features with physical findings. Her history, behaviour of symptoms and physical testing all matched a non-mechanical, progressive problem and the MRI seemed confirmatory.
The pictures on the right show her MRI. You can see the cysts (white) - pictures 1 and 2.
Whilst in the lab and looking at lumbar nerve roots, we came across a Tarlov cyst and removed it to see what it was like.
It was like a soft fibrous balloon; easily compressible between the thumb and index finger, and it bounced back when the pressure was released.
This one had eroded part of the sacrum, probably because of continuous pressure and bone remodelling.
Picture 3 - cyst placed on the cadaver's back.
Picture 4 - hole in the sacrum eroded by the cyst.