Definition and Description

Tarlov cysts (hereafter referred to as TCs) are also known as perineural/perineurial, or sacral nerve root cysts. They are dilations of the nerve root sheaths and are abnormal sacs filled with cerebrospinal fluid (hereafter referred to as CSF) that can cause a progressively painful radiculopathy (nerve pain). They are located most prevalently at the S2, S3 level of the sacrum and less commonly at S1. The sacrum is a fused triangle-shaped bone comprised of the five sacral vertebrae forming the base of the spine. The five lumbar vertebrae are located just above the sacrum, and the four coccygeal vertebrae are just below the sacrum forming the coccyx or tailbone.

The TCs appear on MRI to be dilated or ballooned areas of the sheaths that cover nerve roots exiting from the sacral region of the spinal column. The cysts are created by the dilated sheaths of the nerve roots directly connected to the subarachnoid area of the spinal column, through which the cerebrospinal fluid flows. There are 3 layers or meninges (coverings) of the brain and spinal cord. They are the dura mater, literally meaning hard mother in Latin, which is the outermost , toughest, and most fibrous of the three layers. Next is the arachnoid layer, the middle layer where the spinal fluid flows, and the innermost layer, the pia mater. The space between the arachnoid and pia mater layer is called the subarachnoid space.

Many people have TCs visible on a MRI, but have experienced no relevant symptoms, and the cysts are perhaps identified, but are not acknowledged as significant by the radiologist reading the films or by the physician who ordered them. If the patient has no symptoms that might be suggestive of symptomatic TCs, and sometimes even if they do have symptoms, the patient might not be told about the finding on the MRI. It is not unusual, if the cyst has been present for a number of years to see evidence of erosion and remodeling of the sacral bone. When conditions cause these cysts to fill with spinal fluid and to expand in size, they begin to compress important surrounding nerve fibers, or the cysts may contain nerve fibers, resulting in a variety of symptoms including chronic pain.

Causes and Symptoms

There are a number of conditions that can create increased spinal fluid pressure, increasing the flow of cerebrospinal fluid into the cysts and causing them to expand in size and create symptoms. The cysts are then termed symptomatic Tarlov Cysts. Some incidents or conditions that might cause the asymptomatic cysts to become symptomatic are traumatic injury such as falls, automobile accidents (particularly rear end collisions), heavy lifting, childbirth, and epidurals. Trauma to the spinal cord, an increase in the CSF pressure, or a blockage of the CSF can result in cyst formation. Read "What happens in spinal cord injuries?" in Our Library. It is also hypothesized that the herpes simplex virus can cause the body chemistry to change and predispose the cerebrospinal fluid to fill the cysts and then symptoms begin to develop.

Symptoms of expanding/enlarging cysts occur due to compression of nerve roots that exit from the sacral area. Symptoms may include the following:

• Pain in lower back (particularly below the waist) and in buttocks, legs, and feet

• Weakness and/or cramping in legs and feet

• Parasthesias (abnormal sensations in legs and feet)

• Pain sitting or standing for even short periods of time

• Pain when sneezing or coughing

• Inability to empty the bladder or in extreme cases to urinate at all

• Bowel or bladder changes, including incontinence

• Swelling over the sacral area

• Soreness, a feeling of pressure and tenderness over the sacrum and coccyx (tailbone), extending across the hip and into the thigh

• Headaches (due to the changes in the CSF pressure)

• The feeling of sitting on a rock

• Pulling and burning sensation in coccyx (tailbone) area, especially when bending

• Sciatica

• Vaginal, rectal, and/or abdominal pain

The sciatic nerve is the longest nerve in the body and it originates at the S2, S3 level of the spinal column. It crosses the buttocks and extends down the leg into the foot. Sciatica is a syndrome that results in burning, tingling, numbness, stinging, electrical shock sensations in the lower back, buttocks, thigh, and pain down the leg and foot. Severe sciatica may also result in weakness of the leg and foot.

Most TCs don't cause symptoms and are not diagnosed. However, when symptoms develop that are suggestive of TCs, MRI will demonstrate their presence, and Myelogram or CT may demonstrate the CSF flow between the spinal subarachnoid area and the cyst, determining how rapidly the cyst is filling and whether or not the fluid is freely flowing in and/or out of the cyst.

Diagnosis and Treatment

Most Tarlov cysts are discovered on MRI, CT or Myelogram. It is sometimes confusing to make an accurate diagnosis as to the cause of the symptoms, if there are multiple diagnoses found, such as herniated discs, ruptured disc, DDD (degenerative disc disease). It is sometimes diagnostically conclusive that the cysts are the cause of symptoms, when pain is improved by aspirating the fluid from the cysts. Although using a needle to aspirate CSF from the cysts can temporarily relieve symptoms, eventually the cysts will refill and the symptoms will recur usually within hours. Similarly steroid injections may provide some short term pain relief. Pain may be also temporarily controlled by aspiration of the cysts and then injecting the cysts with fibrin glue (a substance produced from blood chemicals involved in the clotting mechanism). The aspiration of CSF and injection of fibrin glue procedure theoretically is designed to remove the CSF from the cyst, and to block the entrance or the neck of the cyst with the sealant glue, to prevent return of the flow of CSF into the cyst. Some patients have found immediate relief after the procedure, while others have reported a delayed benefit from the procedure when the nerve irritation has subsided. After the procedure, there are outcomes of both short term relief, as well as longer term relief reported.

Transcutaneous Electrical Nerve Stimulation (TENS) has been proven useful for some in pain management. TENS devices deliver electrical impulses through the skin to the cutaneous (surface) and afferent(deep) nerves to control pain. Unlike medications and topical ointments, TENS does not have any known side effects, other than skin irritation from the electrodes seen in some patients.

How does TENS control Pain?

There are two major theories as to how electrical stimulation relieves pain. According to the "gate control theory", pain and non-pain impulses are sent to the brain from the local nervous system. These pulses travel through the cutaneous nerves to the deeper afferent nerves and then to the spinal cord and brain. The gates prevent the brain from receiving too much information too quickly. Since the same nerve cannot carry a pain impulse and a non-pain impulse simultaneously, the stronger, non-pain impulse (from the TENS device) "controls the gate". According to the second theory, TENS stimulation encourages the body to produce natural painkillers called endorphins. These chemicals interact with receptors, blocking the perception of pain. This is similar to the way the drug Morphine works, but without the side effects associated with the pharmaceutical drug.

Using diet or dietary supplements to decrease the body's alkalinity may prevent perineural cysts from filling with more fluid. Pain medications plus medications used to treat chronic nerve related pain (such as antiseizure medications and antidepressants) may be helpful.

Lidoderm patches used for post herpetic neuralgia (PHN) may be applied locally over the sacral area to provide some temporary relief of discomfort sitting and assistance with pain management. In Europe, this same product is marketed under the name Neurodol.

When pain is intractable, despite a variety of interventions, or when other neurological symptoms become severe, and the sacrum is eroding and remodeling, surgery may be the only option. There are a small number of physician's in the world who have surgical expertise in the treatment for TCs, and the long-term outcome of surgery is not highly successful at this time. The usual surgical procedure consists of fenestration and imbrication of the cysts and then packing all the dead space around the cysts with fat, glue, and/or muscle. The body does not like dead spaces, and new cysts will possibly develop in the dead spaces around the old cysts, if not completely filled. Due to the potential risks for further nerve damage, there might be increased symptoms postoperatively, including more bowel and bladder problems.

Treatment Team

Neurosurgeons and interventional neuroradiologists may treat individuals with TCs, if they are knowledgeable about the symptomatology of the cysts and the extended ramifications of untreated cysts that are present with no other spinal pathology. It is important for any other spinal pathology to be ruled out as a possible cause of symptoms.

But, when cysts are visualized on MRI films and there is no other spinal pathology found to be the cause of the symptoms, it is important to refer the patient to someone who is familiar with the pathology and treatment of TCs. Pain management specialists are vital to the treatment of symptomatic Tarlov cysts; family practice physicians play a key role in management of symptoms.

A urologist might be consulted if the cysts are interfering with bladder function with such issues as urinary retention or residual resulting in increased frequency of UTI, and in some cases the necessity to self catheterize. The opposite urinary problem might occur and result in incontinence (inability to control leakage of urine).

Prognosis of Symptomatic Tarlov Cysts

Those who have progressive and prolonged symptoms run a risk of neurological damage, if the cysts continue to compress nerve structures. If the nerve damage is progressive and affects bladder and bowel function and other body systems, it is important to have a good GP (general practitioner) to coordinate referrals to specialists. Individuals who undergo neurosurgery to remove the cysts or those who have the cysts aspirated and injected with fibrin glue have varied results from no improvement to moderate improvement, but in some cases have worsened symptoms and more nerve damage from the procedures.

Collaboration of those very few members of the medical community who are willing to treat Tarlov cysts, as well as improved continuing medical education (CME) is essential to improve the short and long term prognosis of those diagnosed with Tarlov cysts.

The sharing of scientific data from procedures they have performed will aid in developing improved treatment outcomes and in educating the medical community about this devastating and life altering diagnosis. Promoting dedicated research to determine cause and treatment for an improved outcome and prognosis of Tarlov cysts is one of the primary goals of the Tarlov Cyst Disease Foundation.

Resources:

• American Chronic Pain Association

• Encyclopedia of Neurological Disorders

• National Institutes of Health (NIH)

• National Institute of Neurological Disorders and Strokes (NINDS)

• Sacral Nerve Root Cysts, Isadore M. Tarlov

• Personal experiences of those diagnosed with Tarlov cysts

• TENS user manual (EMPI)

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