Meningeal cysts are fluid-filled sacs that develop within or alongside the membranes covering the brain and spinal cord. They form when cerebrospinal fluid collects in a pouch of meningeal tissue, sometimes through a small tear or weak spot in the dura, and they range from tiny incidental findings to large masses that press on nerves and cause real pain. Most are discovered by accident on imaging done for another reason, but when symptoms do appear, the picture can include back pain, nerve-related leg pain, bladder problems, and sexual dysfunction. Treatment depends heavily on size, location, and how much trouble a cyst is actually causing.
Types of Meningeal Cysts
Not all meningeal cysts are the same, and the distinctions matter for deciding how to treat them. A widely used classification divides spinal meningeal cysts into three categories based on where they sit relative to the dura and whether nerve tissue runs through them. Type I cysts are extradural, meaning they lie outside the dura, and they do not contain spinal nerve root fibers. Type II cysts are also extradural but do contain nerve root fibers running through or along the cyst wall. Type III cysts sit inside the dura itself.1PubMed. Updated assessment and current classification of spinal meningeal cysts
Tarlov cysts, also called perineural cysts, are the most commonly encountered subtype. They typically form in the sacral region at the base of the spine and are classified as Type II because nerve fibers are embedded in their walls. They were first described by neurosurgeon Isadore Max Tarlov in the mid-twentieth century.2PubMed. Isadore Max Tarlov (1905-1977) and the controversial Tarlov cyst: historical perspective Beyond the spine, arachnoid cysts can also develop inside the skull. Intracranial arachnoid cysts are fluid collections within the arachnoid membrane of the brain, and their symptoms depend on where they sit and whether they block the normal flow of cerebrospinal fluid.
What Causes Them
The short answer is that meningeal cysts usually form because of a structural weakness in the dura, the tough outer membrane surrounding the spinal cord and brain. Cerebrospinal fluid can herniate through a weak spot or small tear in the dura, gradually inflating a pouch of meningeal tissue into a cyst. That weakness can be something you are born with, or it can develop after trauma or surgery.3Spinal Cord. Spinal extradural meningeal cyst with spinal stenosis
One well-documented mechanism involves a ball-valve effect. A small dural tear allows fluid to flow into the cyst during moments of increased spinal pressure, like coughing or straining, but the opening closes or narrows before the fluid can drain back out. Over time, this one-way flow gradually expands the cyst. In at least one surgical case, a herniated segment of a dorsal nerve rootlet was found plugging the dural opening in exactly this way, acting as the valve.4PubMed. Intraspinal extradural meningeal cyst demonstrating ball-valve mechanism of formation
This ball-valve idea helps explain why some cysts keep growing even when the initial dural defect is small. It also explains why activities that raise pressure inside the spinal canal, such as heavy lifting, prolonged sitting, or Valsalva-type maneuvers, sometimes worsen symptoms.
Connective Tissue Disorders and Other Risk Factors
Certain inherited conditions that weaken connective tissue appear to make meningeal cysts more likely. Marfan syndrome is one of the better-known examples. The dural ectasia that commonly accompanies Marfan syndrome, a ballooning or thinning of the dural sac, can set the stage for cyst formation. Symptomatic sacral cysts in Marfan patients have been documented, sometimes presenting with urinary symptoms from cyst compression of pelvic nerves.5PubMed Central. Marfan syndrome and symptomatic sacral cyst: report of two cases
Ehlers-Danlos syndrome, another connective tissue disorder, has also been linked to multiple spinal meningeal cysts. In one reported case, a woman with Ehlers-Danlos was found to have a large pelvic mass that turned out to be multiple meningeal cysts on imaging.6Neurologia Medico-Chirurgica. Ehlers-Danlos Syndrome Associated with Multiple Spinal Meningeal Cysts —Case Report— Klippel-Trenaunay syndrome, a rarer congenital vascular disorder involving mesodermal abnormalities, may similarly predispose the dura to weakness and cyst development.7PubMed Central. Spinal extradural meningeal cyst in klippel-trenaunay syndrome
If you have a known connective tissue disorder and develop unexplained back pain, pelvic symptoms, or neurological changes in the legs, meningeal cysts are worth raising with your doctor. They are not the most common cause, but they belong on the list of possibilities.
Symptoms
Many meningeal cysts produce no symptoms at all. They show up on an MRI ordered for something else, and the radiologist mentions them as an incidental finding. The question of when a cyst becomes clinically relevant is one of the trickier judgment calls in spinal medicine.
When sacral or lumbar cysts do become symptomatic, the symptom profile tends to reflect compression of nearby nerve roots. A study of patients with midline sacral meningeal cysts found that all reported urinary symptoms, about nine in ten had back pain and radicular leg pain, roughly three-quarters experienced sexual dysfunction, and close to half had bowel symptoms.8PubMed Central. Midline sacral meningeal cysts: Neurophysiology abnormalities and their correlation with pelvic sensory and visceral symptoms Those numbers come from a group of patients who were specifically referred for investigation, so they represent people at the more symptomatic end of the spectrum.
Other red-flag symptoms that have been tied to Tarlov cyst compression include lower limb weakness, neurogenic claudication (leg pain or heaviness that worsens with walking), sensory changes across the buttocks and perineal area, and genital paraesthesia.9American Journal of Case Reports. A Hidden Condition: Multiple Tarlov Cysts Unveiled in a Young Woman Seeking Primary Care for Debilitating Low Back Pain The overlap with disc-related sciatica and other common spinal conditions is considerable, which is part of why these cysts are sometimes overlooked.
Intracranial arachnoid cysts have a different symptom profile that depends on their size and location. Small ones are typically silent. Large cysts in the middle cranial fossa can cause seizures or headaches. Cysts near the base of the brain or in the posterior fossa can block cerebrospinal fluid circulation and lead to hydrocephalus, a buildup of fluid pressure inside the skull.10Clinical Neurology and Neurosurgery. Intracranial arachnoid cysts: Current concepts and treatment alternatives
How They Are Diagnosed
MRI is the primary tool. Standard MRI sequences readily detect the fluid-filled sac and can show its size, location, and relationship to surrounding structures. For sacral cysts, specialized MRI sequences that produce very thin slices can help distinguish Type I cysts (without nerve fibers) from Type II cysts (with nerve fibers running through them), a distinction that influences surgical planning.11PubMed. Role of the constructive interference in steady-state sequence in the classification of sacral meningeal cysts Flow-sensitive MRI sequences have also been used to characterize how freely a cyst communicates with the surrounding subarachnoid space.12Radiology. Sacral meningeal cysts: evaluation with MR imaging
When surgery is being considered, identifying the exact location of the dural defect that feeds the cyst becomes critical. High-resolution MRI techniques with three-dimensional reconstruction have been used to pinpoint the leakage opening in all patients studied in one series, with cyst diameters ranging from about 2 to 11 centimeters.13PubMed Central. Accurate diagnosis and treatment of sacral meningeal cysts without spinal nerve root fibres CT myelography, where contrast dye is injected into the spinal fluid and then scanned, can confirm communication between a cyst and the subarachnoid space. Delayed scans are particularly useful because the contrast gradually seeps into the cyst and outlines its full extent.14European Society of Radiology. Computed tomography myelography: literature review and advantages of dual-energy spectral analysis Digital subtraction techniques and delayed CT can also help locate where the cyst first starts to fill, which tells the surgeon where to look for the dural defect.15PubMed Central. How to locate the dural defect in a spinal extradural meningeal cyst: a literature review
Conservative and Minimally Invasive Treatments
If a meningeal cyst is not causing symptoms, the standard approach is to leave it alone and monitor with periodic imaging. Even mildly symptomatic cysts are often managed conservatively first, especially if the symptoms are tolerable. Pain medications, physical therapy, and activity modification are typical starting points.
For perineural cysts causing pain, steroid therapy has shown some benefit. Oral corticosteroids and epidural steroid injections have been used to reduce inflammation around the cyst and relieve nerve compression symptoms without surgery.16Spine. Conservative Management of Perineural Cysts That said, conservative management does not shrink the cyst itself. In a small study tracking two patients managed conservatively, both showed symptom progression over time, and their cysts grew by about half a centimeter over four to five years.17PLoS ONE. Management of Symptomatic Sacral Perineural Cysts This gradual enlargement, likely driven by the ball-valve mechanism described earlier, is why watchful waiting sometimes transitions to more active treatment.
One step up from conservative care is percutaneous aspiration and injection. Under CT guidance, a needle is inserted into the cyst, fluid is drained, and a sealing agent such as fibrin glue is injected to collapse the cyst and prevent refilling. This has produced good results in individual cases, with marked cyst shrinkage and symptom resolution reported after fibrin glue injection.18PubMed Central. Symptomatic lumbar Tarlov cyst resolution after computed tomography-guided percutaneous trans-sacral fibrin glue intracystic injection However, the procedure carries a specific risk: if the communication between the cyst and the subarachnoid space is not sufficiently narrow, fibrin glue can migrate upward into the spinal canal. In one documented case, glue migrated from a sacral cyst all the way up to the lumbar spine and caused adhesive arachnoiditis, a painful inflammatory condition of the spinal membranes.19PubMed. Adhesive arachnoiditis after percutaneous fibrin glue treatment of a sacral meningeal cyst Confirming that the cyst’s connection to the spinal fluid space is narrow enough before injecting glue is an essential safety step.
Surgical Options and How They Compare
Surgery is reserved for cysts that cause significant or progressive neurological symptoms and that have not responded to less invasive measures. The specific surgical approach depends on whether the cyst is spinal or intracranial, its type, and its relationship to nerve tissue.
For spinal extradural cysts, the goal is to find and close the dural defect feeding the cyst. The surgeon exposes the cyst, identifies the communication point with the subarachnoid space, and sutures it shut. This approach has produced strong results in several case series. In one study of ten adults with thoracolumbar extradural meningeal cysts, the outcome was excellent or good in seven cases and fair in three, with no recurrences during follow-up. The researchers emphasized that finding and microscopically suturing the dural defect was the most important step.20PubMed Central. Surgical Treatment of Ten Adults with Spinal Extradural Meningeal Cysts in the Thoracolumbar Spine A separate series of sacral cysts used high-resolution MRI to locate the leakage point preoperatively, then ligated it through a small incision. Postoperative imaging showed complete cyst disappearance in all patients.13PubMed Central. Accurate diagnosis and treatment of sacral meningeal cysts without spinal nerve root fibres
For Tarlov cysts specifically, wrapping the reconstructed nerve sleeve in a synthetic dural graft after cyst excision has been tried to prevent recurrence. In a series of 24 patients treated this way, no cyst residue or recurrence was found at three months, and neurological function scores showed a statistically significant improvement.21Interdisciplinary Neurosurgery. Wrapping a man-made dura around reconstructed nerve sleeve avoid residue or recurrence of sacral Tarlov cysts
A meta-analysis comparing surgical and percutaneous approaches for symptomatic Tarlov cysts found that both achieved symptomatic improvement in about 84% of patients. But surgery came out ahead on durability: cyst recurrence was about 8% with surgery versus 20% with percutaneous techniques, and worsening of pre-existing symptoms was significantly less common in the surgical group. The trade-off was that surgery had a higher rate of procedure-related complications, though the long-term results favored it.22Journal of Neurosurgery: Spine. A systematic comparative outcome analysis of surgical versus percutaneous techniques in the management of symptomatic sacral perineural (Tarlov) cysts: A meta-analysis
For intracranial arachnoid cysts, the surgical toolbox includes cyst fenestration (creating an opening in the cyst wall so it drains into the normal fluid spaces), cyst removal, and cystoperitoneal shunting (placing a tube that drains cyst fluid into the abdominal cavity). A systematic review of elderly patients with intracranial arachnoid cysts found that fenestration was the most common procedure, used in about 60% of cases, while shunting was used in about 15%. The complication rates were similar across approaches, though shunting had the lowest rate, with only one patient developing a chronic subdural collection.23PubMed Central. The efficacy of cystoperitoneal shunting for the surgical management of intracranial arachnoid cysts in the elderly: A systematic review of the literature
Why These Cysts Get Missed or Misattributed
One of the frustrations for patients with symptomatic Tarlov cysts is that the diagnosis can take years. A big reason is anatomical overlap. The nerve roots compressed by a sacral cyst can produce symptoms that mimic a lumbar disc herniation. Compression of the S2 nerve root, for example, can cause pain patterns that look like an S1 or even L5 radiculopathy, the type that would normally point a clinician toward a disc problem higher up the spine.24Global Spine Journal. Are Tarlov Cysts Being Identified and Reported on Lumbar Spine MRI Scan in Patients with Sciatica When the lumbar MRI shows mild degenerative changes, as it does in many adults, the clinician may attribute the symptoms to the disc and never look further down at the sacrum.
There is also a reporting issue. Tarlov cysts are common enough on MRI that some radiologists note them as incidental findings without emphasizing their potential clinical significance. If the reading physician considers them universally harmless, the connection between the cyst and the patient’s symptoms may never be made. The neurophysiology data from sacral cyst patients shows that over 80% had abnormal nerve-conduction findings, suggesting the cysts were genuinely affecting nerve function and not just sitting there quietly.8PubMed Central. Midline sacral meningeal cysts: Neurophysiology abnormalities and their correlation with pelvic sensory and visceral symptoms For patients with pelvic pain, bladder symptoms, or sciatica that does not line up neatly with lumbar findings, asking whether any sacral cysts were noted on imaging is a reasonable step.
Meningeal Cysts During Pregnancy
Pregnancy introduces a unique set of considerations. The physiological changes of pregnancy, including increased abdominal pressure, greater blood volume, and hormonal shifts that loosen connective tissue, could theoretically influence cyst dynamics. Large presacral Tarlov cysts have been identified during pregnancy, and the concern is not just about symptoms but about delivery. A large cyst in the pelvis could potentially be at risk during vaginal delivery. In one reported case, the first known instance of large presacral Tarlov cysts diagnosed in pregnancy, a cesarean delivery was chosen to avoid the risks that vaginal delivery might have posed to the cyst or surrounding structures.25PubMed Central. Large presacral Tarlov cysts in pregnancy
This is a rare scenario, and no large studies exist to guide management. But if you have a known sacral cyst and become pregnant, it is worth mentioning to your obstetric team so imaging and delivery planning can account for it. The cyst itself is not dangerous to the pregnancy, but its location and size could influence decisions about the safest way to deliver.