Definiton and explanations
Tarlov Cysts - Sacral Perineural Cysts
Tarlov cysts, also known as perineural cysts, are cerebrospinal fluid (CSF) filled sacs located in spinal canal of S1 to S4 region of vertebrae and can be distinguished from other meningeal cysts by nerve-fiber filled walls. Tarlov cysts are defined as cysts formed within the nerve root sheath at dorsal root ganglion. The cause of formation for these cysts are not clear, and the current theories explaining this phenomenon have not been tested or challenged.
Tarlov cysts are relatively common when compared to other neurological cysts, but they are usually asymptomatic. These cysts are often incidentally detected via MRI or CT scans when patients are under examination for other medical reasons. Cysts with diameter of over 1.5 cm are more likely to be symptomatic, and surgical treatment should be considered if all symptom relieving options have been exhausted. No current treatment had promised to be effective due to the unclear pathogenesis and pathophysiology of Tarlov cysts. Current treatment options includes extraction of CSF, complete/partial removal of cysts, fibrin glue therapy, as well as others surgical methodologies.
Nabors and al classified Arachnoïd cysts according to three types:
* Type I : extra-dural, NO nerve roots or rootlets such as intra-sacral méningocèles, probably from congenital origin, that develop from the dural bag to which they are connected by a little collar. They are found at the very place where a dorsal nerve root comes out the dural bag. They are sometimes difficult to be precisely identified and can be “seen” as a type II cyst on pictures. These ones are often associated with some foramina hole enlargement, and with a scalloping of the vertebrae. It is very important to distinguish them from the sacral meningocelaes going to the pelvis area et very often associated with other congenital abnormalities ( teratomes, dermoïdes, lipomes, and other abnormalities( uro-genital and ano-rectal)
* Type II: Extra-dural with a nerve root inside (such as Tarlov or perineural cysts). There are very often not only one but multiple and mostly found in the sacrum area. There are of two kinds: Tarlov (perineural) cysts are after the posterior root ganglion, with nerve fibres inside or nerve tissue in the walls, they are not communicating with the perineural arachnoïdian space. They normally are very small in the upper rachidian part, but can be bigger (to 3cm) when located in the lower part of the sacrum. The second kind in this type is meningeal diverticulaes. They are located before the nerve root ganglion, with nerves fibres inside and are largely communicating with the subarachnoïdian space. 75�f all extra dural cysts (except for Tarlov cysts) are located in the thoracic area, 20�n the lumbar and sacral area, and 5�n the cervical area. Most of them are located behind or on the side of the dural bag. 50�an spread towards the foramina hole. They are large, communicating with subarachnoïdian spaces, and can be large enough to extend to 6 vertebrae levels. There is bone erosion in the foramina hole, or rachidian canal with enlargement for most of extra dural cysts.
* Type III: intra-dural, congenital or made because of traumas…and are rarely associated with other abnormalities. They are very rare. 75�re found in the dorsal area. Most of the congenital ones are located behind the spinal cord on the contrary of those happening because of a trauma…that mostly are located anterior to the spinal cord.
The walls of Tarlov cysts are thin and fibrous; they are prone to rupture if touched, making surgery difficult. The nerve fibers that are embedded in the walls of the cysts has the appearance and size of dental floss, and these nerve fibers are usually not arranged in any specific alignment. Histologic examination reveals the Tarlov cyst outer wall is composed of vascular connective tissue, and the inner wall is lined with flattened arachnoid. In addition, part of the lining containing nerve fibers also occasionally contains ganglion cells. The cysts can contain anywhere from a couple of milliliters of CSF to over 2.5 liters of CSF.
Tarlov cysts are located in the S1 and S4 region of the spinal cord. They usually form on the extradural components of sacrococcygeal nerve roots at the junction of dorsal root ganglion and posterior nerve roots and arise between the endoneurium and perineurium . Occasionally, these cysts are observed in the thoracic spine. However, these cysts most commonly arise at the S2 or S3 junction of the dorsal nerve root ganglion. The cysts are often multiple. The cysts may be found anterior to the sacral area and have been known to extend into the abdominal cavity. These cysts, though rare, can be found to grow large - over 3 - 4 cm. in size, often causing severe abdominal pain from compression on the cyst itself as well as adjoining nerves.
Difference between Tarlov Cysts and other Spinal Meningeal Cysts
The following table is compilation of some key differences between Tarlov Cysts, meningeal cysts, and arachnoid diverticula cysts - see picture. Although the definitions for each entity are still controversial, the following items are generally accepted.
Tarlov cysts are often asymptomatic; the cases of reported symptomatic Tarlov cysts ranges from 15�o 30�f the overall reported Tarlov Cyst Cases depending on the source of literature. Patients with symptomatic Tarlov cysts can be divided into 4 categories according to their experienced symptoms:
* Group 1 - Pain on tailbones that radiates to the legs with potential weakness
* Group 2 - Pain on bones, legs, groin area, sexual dysfunctions, and dysfunctional bladder
* Group 3 - Pain that radiate from the cyst site across hips to the lower abdomen
* Group 4 - No pain, just sexual dysfunction and dysfunctional bladder
Below are a list of commonly reported symptoms associated with Tarlov cysts:
Backpain, perineal pain, Sciatica, Cauda equina syndrome, dysuria, urinary incontinence, coccygodynia, sacral radiculopathy, radicular pain, headaches, retrograde ejaculation, paresthesia, hypesthesia, motor disorders in lower limbs and the genital, perineal, or lumbossacral areas, sacral or buttocks pain, vaginal or penile paraesthesia, sensory changes over buttocks, perineal area, and lower extremity Difficulty walking, Severe lower abdominal pain
There are several hypotheses proposed regarding the formation of Tarlov cysts, including:
inflammation within the nerve root cysts followed by inoculation of fluids, developmental or congenital origin, arachnoidal proliferation along and around the exiting sacral nerve root, and breakage of venous drainage in the perineuria and epineurium secondary to hemosiderin deposition after trauma. Tarlov himself theorized that the perineurial cysts form as a result of blockage of venous drainage in the perineurium and epineuriium secondary to hemosiderin deposition after local trauma. Another theory gaining increasing popularity over the past decade is one postulated by Fortuna et al.; it described perineurial cysts to be the results of congenital arachnoidal proliferation along the exiting sacral nerve roots. The cause of these cysts are still unknown and the proposed theories have not been tested or challenged.
Difference between Tarlov Cysts and other Spinal Meningeal Cysts
The following table is compilation of some key differences between Tarlov Cysts, meningeal cysts, and arachnoid diverticula cysts. Although the definitions for each entity are still controversial, the following items are generally accepted.
Potential communication with spinal subarachnoid space
Delayed filling in myelograms
Found distal to the junction of posterior nerve root and dorsal root ganglian in sacral region
Walls contain nerve fibers
Often multiple, extending around the circumference of nerve root
_______________Meningeal Diverticula & Arachnoid Diverticula________________________________
Communicates freely with spinal subarachnoid space
Rapid filling in myelograms
Found proximal to dorsal root ganglion throughout vertebral column
Walls lined by arachnoid mater with no signs of neural element
No pattern of formation in regards to multiplicity
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