Treatment of Symptomatic Perineural (Tarlov) Cysts  

Donlin M. Long M.D., PhD. 
Johns Hopkins Medicine, Baltimore, Maryland  

Perineural cysts are common findings on MRI done for other diagnostic purposes.  Most are located in the lumbar, low back, or sacral, tailbone, area.

Cysts are usually small, about the size of a bean, but can grow to enormous size.  The largest I have encountered filled the entire abdomen and the patient thought she might be pregnant.  These cysts are often multiple, particularly when they are located in the sacral (tailbone) area.  A few are large enough to extend into the abdomen and be mistaken for abdominal masses.

Symptomatic cysts usually cause pain.  The typical symptom is pain in the distribution of the nerve or nerves on which the cysts are found.  The cysts may also cause loss of neurological function such as weakness of muscles, loss of sensation on the skin, loss of reflexes, or even changes in bowel, bladder, or sexual function.  The cysts may slowly grow and often erode bone leaving large cavities as they expand. They can follow nerves into the abdomen and present as abdominal masses often mistaken for tumors or ovarian cysts. Diagnosis is made on MRI with almost complete certainty.
Treatment should follow only when it is reasonably certain that the cyst is the cause of symptoms and when these symptoms are serious enough to warrant treatment.  Simply finding a cyst doesn’t mean that it should be treated.  Most patients who have these cysts and have back pain are symptomatic because of some other back abnormality, not the cyst.  When symptoms are present, can be determined to be caused by the cyst, and are serious enough to warrant treatment, then several options are available. 

We have recently begun an investigation to learn if we can treat these cysts effectively using only needles inserted through the skin.  With this technique we identify the cyst with MRI and then use CT-fluoroscopy to place a needle within the cyst.  The exact needle placement is verified and then the contents of the cyst, which are clear spinal fluid, are removed.  The cyst is then filled with a tissue adhesive injected through the same needle.  The procedure takes 30-45 minutes.

During the past year, we have treated 28 patients. 12 of those 28 patients have now been followed for six months to one year. Eight of the 12 have achieved excellent control of pain rating their pain as 0 or 1 on a 10 point scale. Two patients achieved three months of relief and then had recurrence of pain. They are scheduled for re-aspiration. Two patients did not have any relief following an apparent successful aspiration. No patients have had a neurological complication, though one patient complains of some increased numbness in the perineum. One patient found the procedure too painful to continue and another patient who has achieved excellent long-term result had worsened pain for at least a few weeks.

We now placed two needles using the CT control, which increases the amount of adhesive we can inject. We think that this has reduced pain for patients during the procedure and certainly has improved our ability to completely fill the cysts.

The reason we have undertaken this as an approved study is that the data available in literature does not prove with certainty that this will be a useful technique.  However it is of low risk and does not influence subsequent surgical treatment in any way that we can determine. We will continue to study this problem but at this time the aspiration looks promising and has been successful at least the short term.

The standard treatment for the symptomatic Tarlov cyst is surgery.  This requires an operation to expose the region of the spine where the cyst is located.  The cyst is opened and the fluid drained and then the key is to prevent the fluid from returning.  The cyst may be packed with fat or tissue adhesive or both.  Sometimes it is possible to occlude the neck of the cyst with a suture thus preventing it from refilling.  The large abdominal cysts often require direct abdominal surgery.  These days this is done with an endoscope and we have been successful in obliterating the abdominal cysts in the small number of patients that have required this technique.

The key to deciding about treatment of these cysts is to be certain the cyst is the cause of the symptoms.  Before deciding on intervention the symptoms should be serious enough that their treatment is indicated.  The percutaneous technique avoids surgery, is safe, but is not proven at present.  We offer it to all suitable candidates.  Surgery is effective but rarely indicated.  My own experience over 40 years remains less than 50 patients.  Outcomes have been good but failures occur and the possibility of nerve injury during the attempted repair exists.  The risk of failure appears to be 1 or 2 in 100 and nerve injury has occurred in 1 of approximately 50 patients.

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This information was sent to us by Dr. Long during July, 2004.