Tarlov cyst
Encyclopedia
Tarlov cysts, also known as perineurial cysts, are cerebrospinal-fluid
-filled (CSF) sacs located in the spinal canal of the S1-to-S4 region, of the spinal cord
, and can be distinguished from other meningeal cysts by their nerve-fiber-filled walls. Tarlov cysts are defined as cysts formed within the nerve-root sheath at the dorsal root ganglion
. The etiology
of these cysts is not well understood; some current theories explaining this phenomenon have not yet been tested or challenged.
Tarlov cysts are relatively common when compared to other neurological cysts, but they are usually asymptomatic. These cysts are often detected incidentally during MRI
or CT
scans for other medical conditions. Cysts with diameters of over 1.5 cm (0.590551181102362 in) are more likely to be symptomatic; surgical treatment should be considered if all other symptom-relieving options have been exhausted. No current treatment so far has proven to be effective due to the unclear pathogenesis
and pathophysiology
of Tarlov cysts. Current treatment options include CSF aspiration, complete or partial removal, fibrin
-glue therapy, amongst other surgical treatment approaches.
Nabors et al. classify Arachnoïd cysts into three types:
difficult. The nerve fibers embedded in the walls of the cysts have the appearance and size of dental floss
; 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
tissue. 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 litres (5.3 US pt) of CSF.
. 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, extending around the circumference of the nerve, and can enlarge over time to compress neighboring nerve roots, to cause bone erosion. 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 (1.2–1.6 in) in size, often causing severe abdominal pain from compression on the cyst itself as well as adjoining nerves.
Back pain, perineal pain, Sciatica
, Cauda equina syndrome
, dysuria
, urinary incontinence
, coccygodynia
, sacral radiculopathy
, radicular pain
, headache
s, retrograde ejaculation
, paresthesia
, hypesthesia, motor disorders in lower limbs and the genital, perineal, or lumbosacral areas, sacral or buttocks pain, vaginal or penile paraesthesia, sensory changes over buttocks, perineal area, and lower extremity; difficulty walking; severe lower abdominal pain.
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 epineurium 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 is still unknown, and the proposed theories have not been tested or challenged.
being pushed into the cyst during systole
pulsation, but unable to get out during the diastole
phase, resulting in enlargement over time. However, this theory has yet to be tested. Although growth in the cysts occur, it is still unknown how often, or at what condition, these cyst form, or if any underlying condition is essential for the formation and enlargement of these cysts.
Many patients have been diagnosed for 20 years, showing a very thin sacrum bone "protecting" a large meningeal cyst. MRIs regularly made do not show any enlargement or any change. The "erosion" theory might be a simplification in regard of the life of a bony structure. Another view involves the shape of the bone, according to the fact that between the bone and the cyst strong and solid ligament
s exist, and that the walls of the cysts are very fragile compared to ligaments and bones, when looking "eroded" means a congenital cyst or that was formed before the person was about 25 years old. There are many people who have cysts and no remodelling of the bone: neuroradiologists tell that those are due to a cause which took place when older than 25 years.
Bone Development and Structure
Because bone is made up of minerals, mostly hydroxyapatite, and is hard, many people think that it is not living material. But a bone in a living animal consists of both living tissue and non-living substances. Within the "alive bone" are blood vessels, nerves, collagen
, and living cells including:
In addition, bone contains cells called osteocytes, which are mature osteoblasts that have ended their bone-forming careers. These cells engage in metabolic exchange with the blood that flows through the bones. The nonliving, but very important, substances in bone are the minerals and salts. Besides the metabolically active cellular portion of bone tissue, bone is also made up of a matrix (a bonding of multiple fibers and chemicals) of different materials, including primarily collagen fibers and crystalline salts. In particular, it is the collagen fibers and the calcium salts that help to strengthen bone. In fact, the collagen fibers of bone have great tensile strength (the strength to endure stretching forces), while the calcium salts, which are similar in physical properties to marble
, have great compressional strength (the strength to endure squeezing forces). These combined properties, plus the degree of bondage between the collagen fibers and the crystals, provide a bony structure that has both extreme tensile and compressional strength.
Thus, bones are constructed in exactly the same way that reinforced concrete is constructed. The steel of reinforced concrete provides the tensile strength, while the cement, sand, and rock provide the compressional strength. However, the compressional strength of bone is greater than that of even the best reinforced concrete, and the tensile strength approaches that of reinforced concrete. But, even with their great compressional and tensile strengths, neither bone nor concrete has a very high level of torsional strength (the strength to endure twisting). In fact, bone fractures often occur as a result of torsional forces that are exerted on an arm or a leg.
The Blood Theory
Many authors state that the blood, and breakdown products, acting as a foreign-body substance in the subarachnoid space, produce local adhesive arachnoiditis with no symptoms but can also create cystic degeneration. The subarachnoid space abhors all foreign body substances. Even the presence of injected air is considered to be a "foreign body." Blood is definitely considered a foreign body (particularly the breakdown products of blood). Repeated exposure to foreign-body substances in the subarachnoid space can initiate auto-immune amnestic reactions which may potentiate and magnify the ongoing inflammatory process.
Few clinicians appreciate that significant pathologic change can occur unaccompanied by clinical symptoms because of the body's remarkable ability to adjust to, and compensate for, slowly occurring insult. This is particularly true of nervous system which does not respond well to acute change or acute insult (i.e. sudden trauma, acute intracranial haemorrhage or acute rupture of an aneurysm
). The ability of the body to compensate is an important reason why most individual afflicted with adhesive arachnoiditis
have few in the way of clinical symptoms. This state is, however, a tenuous one, which can change dramatically with only minimal additional insult, mostly when the individual is also afflicted of meningeal (arachnoid or Tarlov cysts).
We also live in a medical era where frequent (inadvertent) lumbar
punctures are performed by ill-advised blind-technique in cases of attempted epidural steroid administration or epidural anaesthesia.
It is not unusual for patients to experience, as a complication of spinal tap, continued leakage of cerebrospinal fluid producing postural headache, light-headedness and inability to function due to these complaints. The commonly employed treatment for this is a "blood patch". Blood drawn from a vein is purposely injected into the supposed epidural space as a means of "patching" the leaking fluid.
Appropriate blood patches routinely introduce some blood into the subarachnoid space and inappropriate ones may introduce as much as 10-12cc of blood directly into the subarachnoid space. How much blood, introduced how often, is necessary to create adhesive arachnoiditis? This question has not yet been answered. We only know at this point in time, that blood, and its breakdown products, can serve to create adhesive arachnoiditis and the introduction of any foreign body substance (for any purpose) into the subarachnoid space is not a wonderful idea.
Not to forget to mention that arachnoïd cysts, meningeal cysts are very frequently induced by a dormant Arachnoïditis and that only that area of the spine, where the “cysts” are can be the cause for neuropathic pain and a limitation of functions syndrome.( Charles Burton-The Burton report
http://www.burtonreport.com/ , Dr Sarah Fox http://www.theaword.org/,Dr Aldrete - Arachnoïditis: The evidence revealed jan.2010, editorial Allil ISBN 978-607-7504-25-2)
, is considered the imaging study of choice in identifying Tarlov cysts. MRI provides better resolution of tissue density, absence of bone interference, multiplanar capabilities, and is noninvasive. Plain films may show bony erosion of the spinal canal or of the sacral foramina
On MRI pictures, the signal is the same as the CSF one.
If MRI made with a contrast medium:
(CT) scan is another examination method often used for the diagnosis of Tarlov cyst. Unenhanced CT scans may show sacral erosion, asymmetric epidural fat distribution, and cystic masses that are have the same density with CSF. CT Myelogram is minimally invasive, and could be employed when MRI cannot be performed on patient.
; these tools are very useful in spotting cysts at the region, but they cannot distinguish one major difference between Tarlov cysts and other cysts: the fact the walls contain nerve fibers. Therefore, the final diagnosis of a Tarlov cyst is not a radiological
but rather, a histopathological, diagnosis These cysts are sometimes also misdiagnosed as lumbar disc herniation or lumbar spinal stenosis, especially when they are pressing on the S-1 nerve root.
and pathophysiology of Tarlov cysts, there is no consensus on the optimal treatment of symptomatic sacral perineurial cysts. There are a few treatments available for alleviating the symptoms caused by these cysts, but their effectiveness is debatable. Therefore, operative criteria for regarding Tarlov cysts include: 1) MRI results indicating the existence of sacral perineural cyst; 2) the diameter of cyst is more than 1.5 cm or 0.6 inch; 3) neurological symptoms and signs attributed to sacral perineural cysts that are serious enough to warrant treatment; 4) no or little response to medical and physical therapy, and 5) no contraindications for the surgery. The two major treatment types are the extraction of cerebrospinal fluids from the cyst, and the complete/partial removal of cyst from an infected area. But because the cyst walls are lined with nerves, this may not be an option. The morbidity has been seen to be higher on patients that have bilateral cysts on the same spinal level. It had been reported that a positive filling defect and larger cyst size (>1.5 cm or 0.6 inch) is a good indicator for successful treatment outcome. Although fibrin
-glue therapy had been proven to be a promising therapy in the treatment of these cysts, there have been cases of the fibrin seeping back up into the spine, affecting other nerves. It is not recommended for use at present by the Health Department in some countries. Nevertheless, all types of surgical treatment pose common risks, including neurological deficits, infection and inflammation, spinal headache, urinary disturbances, and leakage of cerebrospinal fluids.
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
-filled (CSF) sacs located in the spinal canal of the S1-to-S4 region, of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
, and can be distinguished from other meningeal cysts by their nerve-fiber-filled walls. Tarlov cysts are defined as cysts formed within the nerve-root sheath at the dorsal root ganglion
Dorsal root ganglion
In anatomy and neuroscience, a dorsal root ganglion is a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves.-Unique unipolar structure:...
. The etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
of these cysts is not well understood; some current theories explaining this phenomenon have not yet been tested or challenged.
Tarlov cysts are relatively common when compared to other neurological cysts, but they are usually asymptomatic. These cysts are often detected incidentally during MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
or CT
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
scans for other medical conditions. Cysts with diameters of over 1.5 cm (0.590551181102362 in) are more likely to be symptomatic; surgical treatment should be considered if all other symptom-relieving options have been exhausted. No current treatment so far has proven to be effective due to the unclear pathogenesis
Pathogenesis
The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...
and pathophysiology
Pathophysiology
Pathophysiology is the study of the changes of normal mechanical, physical, and biochemical functions, either caused by a disease, or resulting from an abnormal syndrome...
of Tarlov cysts. Current treatment options include CSF aspiration, complete or partial removal, fibrin
Fibrin
Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....
-glue therapy, amongst other surgical treatment approaches.
Classification
Tarlov cysts are considered Type II lesions, being defined as extradural meningeal cysts with nerve fibers.Nabors et al. classify Arachnoïd cysts into three types:
- Type I : Extra-dural; no nerve roots or rootlets such as intra-sacral meningoceles; probably of congenital origin developing from the dural sac to which they are connected by a little collar. They are found at the pont of exit of a dorsal nerve root from the dural sac. They are sometimes difficult to identify and can be “seen” as a type II cyst on imaging. These cysts are often associated with foramina enlargement and scalloping of the vertebrae. It is very important to distinguish them from sacral meningoceles going to the pelvic area; they are often associated with other congenital abnormalities ( teratomes, dermoïdes, lipomes, and other abnormalities( uro-genital and ano-rectal))
- Type II: Extra-dural; nerve root present (such as Tarlov or perineural cysts). There are often not only one but multiple cysts, mostly found in the sacrum area. There are two types: Tarlov (perineural) cysts are located posteriorly to the root ganglion, with nerve fibres inside or nerve tissue in the walls; they are not communicating with the perineural arachnoid space. Type-II cysts are very small in the upper sacral area, but can be bigger (up to 3 centimetres or 1.2 in) if found located in the lower part of the sacrum.
The second variant of type-II cysts are called "meningeal diverticuli". They are located anteriorly to the nerve root ganglion, with nerves fibres inside and communicating with the subarachnoid space. 75% of all extra-dural cysts (except for Tarlov cysts) are located in the thoracic area, 20% in the lumbar and sacral area, and 5% in the cervical area. Most cysts are located posteriorly or laterally to the dural sac. Nearly 50% of cysts can extend towards the foramina. These are large in size, communicate with subarachnoid space, and can be large enough to extend across 6 vertebrae levels. There can be evidence of bone erosion in the foramina and dural canal.
- Type III: intra-dural; these are either congenital or caused by trauma; they are rarely associated with other abnormalities and rare in occurrence. About 75% can be found in the dorsal area. Most of the congenital type-III cysts can be found posteriorly to the spinal cord, as opposed to those caused by trauma which can be found anteriorly to the spinal cord.
Appearance
Walls of Tarlov cysts are thin and fibrous; they are prone to rupture if touched, making surgerySurgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
difficult. The nerve fibers embedded in the walls of the cysts have the appearance and size of dental floss
Dental floss
Dental floss is made of either a bundle of thin nylon filaments or a plastic ribbon used to remove food and dental plaque from teeth. The floss is gently inserted between the teeth and scraped along the teeth sides, especially close to the gums. Dental floss may be flavored or unflavored, and...
; these nerve fibers are usually not arranged in any specific alignment. Histologic
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
examination reveals the Tarlov-cyst outer wall is composed of vascular connective tissue, and the inner wall is lined with flattened arachnoid
Arachnoid mater
The arachnoid mater, literally from Latin "spider -like mother", is one of the three meninges, the membranes that cover the brain and spinal cord...
tissue. 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 litres (5.3 US pt) of CSF.
Location
Tarlov cysts are located in the S1 and S4 region of the spinal cordSpinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. They usually form on the extradural components of sacrococcygeal nerve roots at the junction of dorsal root ganglion
Dorsal root ganglion
In anatomy and neuroscience, a dorsal root ganglion is a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves.-Unique unipolar structure:...
and posterior nerve roots and arise between the endoneurium
Endoneurium
The endoneurium, also referred to as an endoneurial channel, sheath or tube, is a layer of delicate connective tissue made up of endoneurial cells that encloses the myelin sheath of a spinal cord nerve fiber. These are bundled up into groups called nerve fascicles, which have a protective sheath...
and perineurium
Perineurium
In the peripheral nervous system, nerve fibers are each wrapped in a protective sheath known as the endoneurium. These are bundled together into groups known as fascicles, each surrounded by a protective sheath known as the perineurium. Several fascicles may be in turn bundled together with a blood...
. 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, extending around the circumference of the nerve, and can enlarge over time to compress neighboring nerve roots, to cause bone erosion. The cysts may be found anterior to the sacral area and have been known to extend into the abdominal cavity
Abdominal cavity
The abdominal cavity is the body cavity of the human body that holds the bulk of the viscera. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the thoracic diaphragm , and its oblique floor is the pelvic inlet...
. These cysts, though rare, can be found to grow large - over 3–4 cm (1.2–1.6 in) 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. Although the definitions for each entity are still controversial, the following items are generally accepted.| Tarlov Cyst | Meningeal Diverticula & Arachnoid Diverticula |
|---|---|
| Potential communication with spinal subarachnoid space | Communicates freely with spinal subarachnoid space |
| Delayed filling in myelograms | Rapid filling in myelograms |
| Found distal to the junction of posterior nerve root and dorsal root ganglion in sacral region | Found proximal to dorsal root ganglion throughout vertebral column |
| Walls contain nerve fibers | Walls lined by arachnoid mater with no signs of neural element |
| Often multiple, extending around the circumference of nerve root | No pattern of formation in regards to multiplicity |
Symptoms
Tarlov cysts are often asymptomatic; the cases of reported symptomatic Tarlov cysts ranges from 15% to 30% of the overall reported Tarlov cyst case, depending on the source of literature. Nevertheless, these cysts are important clinical entities because of their tendency to increase in size over time, potentially causing complications and eroding the surrounding bone tissue. 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.
Common symptoms
Below are a list of commonly reported symptoms associated with Tarlov cysts:Back pain, perineal pain, Sciatica
Sciatica
Sciatica is a set of symptoms including pain that may be caused by general compression or irritation of one of five spinal nerve roots that give rise to each sciatic nerve, or by compression or irritation of the left or right or both sciatic nerves. The pain is felt in the lower back, buttock, or...
, Cauda equina syndrome
Cauda equina syndrome
Cauda equina syndrome ' is a serious neurologic condition in which there is acute loss of function of the lumbar plexus, neurologic elements of the spinal canal below the termination of the spinal cord.-Causes:...
, dysuria
Dysuria
In medicine, specifically urology, dysuria refers to painful urination.Difficult urination is also sometimes described as dysuria.It is one of a constellation of irritative bladder symptoms, which includes urinary frequency and haematuria....
, urinary incontinence
Urinary incontinence
Urinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...
, coccygodynia
Coccydynia
Coccydynia is a medical term meaning pain in the coccyx or tailbone area, usually brought on by sitting too abruptly.-Diagnosis:A number of different conditions can cause pain in the general area of the coccyx, but not all involve the coccyx and the muscles attached to it. The first task of...
, sacral radiculopathy
Radiculopathy
Radiculopathy is not a specific condition, but rather a description of a problem in which one or more nerves are affected and do not work properly . The emphasis is on the nerve root...
, radicular pain
Radicular pain
Radicular pain, or radiculitis, is pain "radiated" along the dermatome of a nerve due to inflammation or other irritation of the nerve root at its connection to the spinal column...
, headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
s, retrograde ejaculation
Retrograde ejaculation
In the human male reproductive system, retrograde ejaculation occurs when semen, which would normally be ejaculated via the urethra, is redirected to the urinary bladder. Normally, the sphincter of the bladder contracts before ejaculation forcing the semen to exit via the urethra, the path of least...
, paresthesia
Paresthesia
Paresthesia , spelled "paraesthesia" in British English, is a sensation of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. It is more generally known as the feeling of "pins and needles" or of a limb "falling asleep"...
, hypesthesia, motor disorders in lower limbs and the genital, perineal, or lumbosacral areas, sacral or buttocks pain, vaginal or penile paraesthesia, sensory changes over buttocks, perineal area, and lower extremity; difficulty walking; severe lower abdominal pain.
Formation
There are several hypotheses proposed regarding the formation of Tarlov cysts, including: inflammation within the nerve root cysts followed by inoculationInoculation
Inoculation is the placement of something that will grow or reproduce, and is most commonly used in respect of the introduction of a serum, vaccine, or antigenic substance into the body of a human or animal, especially to produce or boost immunity to a specific disease...
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
Epineurium
The epineurium is the outermost layer of connective tissue surrounding a peripheral nerve. It is made of dense irregular connective tissue and usually contains multiple nerve fascicles as well as blood vessels which supply the nerve...
secondary to hemosiderin
Hemosiderin
thumb|Hemosiderin image of a kidney viewed under a microscope. The brown areas represent hemosiderinHemosiderin or haemosiderin is an iron-storage complex. It is always found within cells and appears to be a complex of ferritin, denatured ferritin and other material...
deposition after trauma.
Tarlov himself theorized that the perineurial cysts form as a result of blockage of venous drainage in the perineurium and epineurium 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 is still unknown, and the proposed theories have not been tested or challenged.
Enlargement
Tarlov cysts are known to have the tendency to enlarge over time. The prominent theory that explains this phenomenon reasons the enlargement of the cysts is due to the cerebrospinal fluidCerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
being pushed into the cyst during systole
Systole (medicine)
Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
pulsation, but unable to get out during the diastole
Diastole
Diastole is the period of time when the heart fills with blood after systole . Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing...
phase, resulting in enlargement over time. However, this theory has yet to be tested. Although growth in the cysts occur, it is still unknown how often, or at what condition, these cyst form, or if any underlying condition is essential for the formation and enlargement of these cysts.
Many patients have been diagnosed for 20 years, showing a very thin sacrum bone "protecting" a large meningeal cyst. MRIs regularly made do not show any enlargement or any change. The "erosion" theory might be a simplification in regard of the life of a bony structure. Another view involves the shape of the bone, according to the fact that between the bone and the cyst strong and solid ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
s exist, and that the walls of the cysts are very fragile compared to ligaments and bones, when looking "eroded" means a congenital cyst or that was formed before the person was about 25 years old. There are many people who have cysts and no remodelling of the bone: neuroradiologists tell that those are due to a cause which took place when older than 25 years.
Bone Development and Structure
Because bone is made up of minerals, mostly hydroxyapatite, and is hard, many people think that it is not living material. But a bone in a living animal consists of both living tissue and non-living substances. Within the "alive bone" are blood vessels, nerves, collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
, and living cells including:
- • osteoblastOsteoblastOsteoblasts are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen...
s (cells that help form bone), and - • osteoclastOsteoclastAn osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption. Osteoclasts were discovered by Kolliker in 1873...
s (cells that help eat away old bone).
In addition, bone contains cells called osteocytes, which are mature osteoblasts that have ended their bone-forming careers. These cells engage in metabolic exchange with the blood that flows through the bones. The nonliving, but very important, substances in bone are the minerals and salts. Besides the metabolically active cellular portion of bone tissue, bone is also made up of a matrix (a bonding of multiple fibers and chemicals) of different materials, including primarily collagen fibers and crystalline salts. In particular, it is the collagen fibers and the calcium salts that help to strengthen bone. In fact, the collagen fibers of bone have great tensile strength (the strength to endure stretching forces), while the calcium salts, which are similar in physical properties to marble
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...
, have great compressional strength (the strength to endure squeezing forces). These combined properties, plus the degree of bondage between the collagen fibers and the crystals, provide a bony structure that has both extreme tensile and compressional strength.
Thus, bones are constructed in exactly the same way that reinforced concrete is constructed. The steel of reinforced concrete provides the tensile strength, while the cement, sand, and rock provide the compressional strength. However, the compressional strength of bone is greater than that of even the best reinforced concrete, and the tensile strength approaches that of reinforced concrete. But, even with their great compressional and tensile strengths, neither bone nor concrete has a very high level of torsional strength (the strength to endure twisting). In fact, bone fractures often occur as a result of torsional forces that are exerted on an arm or a leg.
The Blood Theory
Many authors state that the blood, and breakdown products, acting as a foreign-body substance in the subarachnoid space, produce local adhesive arachnoiditis with no symptoms but can also create cystic degeneration. The subarachnoid space abhors all foreign body substances. Even the presence of injected air is considered to be a "foreign body." Blood is definitely considered a foreign body (particularly the breakdown products of blood). Repeated exposure to foreign-body substances in the subarachnoid space can initiate auto-immune amnestic reactions which may potentiate and magnify the ongoing inflammatory process.
Few clinicians appreciate that significant pathologic change can occur unaccompanied by clinical symptoms because of the body's remarkable ability to adjust to, and compensate for, slowly occurring insult. This is particularly true of nervous system which does not respond well to acute change or acute insult (i.e. sudden trauma, acute intracranial haemorrhage or acute rupture of an aneurysm
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
). The ability of the body to compensate is an important reason why most individual afflicted with adhesive arachnoiditis
Arachnoiditis
Arachnoiditis is a neuropathic disease caused by the inflammation of the arachnoid, one of the membranes that surround and protect the nerves of the central nervous system, including the brain and spinal cord...
have few in the way of clinical symptoms. This state is, however, a tenuous one, which can change dramatically with only minimal additional insult, mostly when the individual is also afflicted of meningeal (arachnoid or Tarlov cysts).
We also live in a medical era where frequent (inadvertent) lumbar
Lumbar
In tetrapod anatomy, lumbar is an adjective that means of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum ...
punctures are performed by ill-advised blind-technique in cases of attempted epidural steroid administration or epidural anaesthesia.
It is not unusual for patients to experience, as a complication of spinal tap, continued leakage of cerebrospinal fluid producing postural headache, light-headedness and inability to function due to these complaints. The commonly employed treatment for this is a "blood patch". Blood drawn from a vein is purposely injected into the supposed epidural space as a means of "patching" the leaking fluid.
Appropriate blood patches routinely introduce some blood into the subarachnoid space and inappropriate ones may introduce as much as 10-12cc of blood directly into the subarachnoid space. How much blood, introduced how often, is necessary to create adhesive arachnoiditis? This question has not yet been answered. We only know at this point in time, that blood, and its breakdown products, can serve to create adhesive arachnoiditis and the introduction of any foreign body substance (for any purpose) into the subarachnoid space is not a wonderful idea.
Not to forget to mention that arachnoïd cysts, meningeal cysts are very frequently induced by a dormant Arachnoïditis and that only that area of the spine, where the “cysts” are can be the cause for neuropathic pain and a limitation of functions syndrome.( Charles Burton-The Burton report
http://www.burtonreport.com/ , Dr Sarah Fox http://www.theaword.org/,Dr Aldrete - Arachnoïditis: The evidence revealed jan.2010, editorial Allil ISBN 978-607-7504-25-2)
Diagnosis
Two most commonly used and effective examination method for Tarlov Cysts are MRI and CT. Both CT and MRI are good imaging procedures that allow the detection of extradural spinal masses such as Tarlov cysts. In fact, most of the cysts are asymptomatic and are found incidentally during CT or MRI examinations for other reasons.MRI
MRI, or Magnetic Resonance ImagingMagnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
, is considered the imaging study of choice in identifying Tarlov cysts. MRI provides better resolution of tissue density, absence of bone interference, multiplanar capabilities, and is noninvasive. Plain films may show bony erosion of the spinal canal or of the sacral foramina
On MRI pictures, the signal is the same as the CSF one.
If MRI made with a contrast medium:
- The signal in the cyst is the same as in the dural bag.
- The signal for cysts due to traumas…is a little stronger at the periphery or nerve root location
- The signal is more important for other causes: synovial cysts, dermoïdes or épidermoïdes cysts, teratomes
CT
A computed tomographyComputed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
(CT) scan is another examination method often used for the diagnosis of Tarlov cyst. Unenhanced CT scans may show sacral erosion, asymmetric epidural fat distribution, and cystic masses that are have the same density with CSF. CT Myelogram is minimally invasive, and could be employed when MRI cannot be performed on patient.
Misdiagnosis
The term "Tarlov cysts" (or "sacral perineurial cyst"), has often been misused for referring to other cystic lesions in the sacral region. Tarlov cysts are often detected through MRI or CT MyelographyMyelography
Myelography is a type of radiographic examination that uses a contrast medium to detect pathology of the spinal cord, including the location of a spinal cord injury, cysts, and tumors...
; these tools are very useful in spotting cysts at the region, but they cannot distinguish one major difference between Tarlov cysts and other cysts: the fact the walls contain nerve fibers. Therefore, the final diagnosis of a Tarlov cyst is not a radiological
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...
but rather, a histopathological, diagnosis These cysts are sometimes also misdiagnosed as lumbar disc herniation or lumbar spinal stenosis, especially when they are pressing on the S-1 nerve root.
Treatment
Because of the unclear pathogenesisPathogenesis
The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...
and pathophysiology of Tarlov cysts, there is no consensus on the optimal treatment of symptomatic sacral perineurial cysts. There are a few treatments available for alleviating the symptoms caused by these cysts, but their effectiveness is debatable. Therefore, operative criteria for regarding Tarlov cysts include: 1) MRI results indicating the existence of sacral perineural cyst; 2) the diameter of cyst is more than 1.5 cm or 0.6 inch; 3) neurological symptoms and signs attributed to sacral perineural cysts that are serious enough to warrant treatment; 4) no or little response to medical and physical therapy, and 5) no contraindications for the surgery. The two major treatment types are the extraction of cerebrospinal fluids from the cyst, and the complete/partial removal of cyst from an infected area. But because the cyst walls are lined with nerves, this may not be an option. The morbidity has been seen to be higher on patients that have bilateral cysts on the same spinal level. It had been reported that a positive filling defect and larger cyst size (>1.5 cm or 0.6 inch) is a good indicator for successful treatment outcome. Although fibrin
Fibrin
Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....
-glue therapy had been proven to be a promising therapy in the treatment of these cysts, there have been cases of the fibrin seeping back up into the spine, affecting other nerves. It is not recommended for use at present by the Health Department in some countries. Nevertheless, all types of surgical treatment pose common risks, including neurological deficits, infection and inflammation, spinal headache, urinary disturbances, and leakage of cerebrospinal fluids.