Choroidal fissure cysts are, in the vast majority of cases, not dangerous. They are almost always discovered by accident during brain imaging ordered for an unrelated reason, and most people who have one will never experience a single symptom from it. That said, the word “cyst” on a brain MRI report understandably causes alarm, and a small number of these cysts do behave in ways that need medical attention. Understanding what separates the harmless majority from the rare exceptions is worth the time.
What a Choroidal Fissure Cyst Is
The choroidal fissure is a natural cleft in the brain’s temporal lobe, a groove where certain membranes fold inward during fetal development. A choroidal fissure cyst is a small fluid-filled sac that forms along this groove, typically containing fluid that looks identical to cerebrospinal fluid on imaging. These cysts can originate from neuroglial, neuroepithelial, or arachnoid tissue, all of which are normal components of the brain’s lining and support structures.1Anatomy & Cell Biology. Choroidal fissure and choroidal fissure cysts: a comprehensive review They are not tumors, they are not cancerous, and they do not transform into anything malignant. Focal atrophy in the temporal lobe can sometimes cause the choroidal fissure itself to widen, which on a scan can mimic the appearance of a cyst even when no true cyst is present.
One of the earliest imaging studies to characterize these lesions identified 26 patients with medial temporal lobe cysts arising in or near the choroidal fissure, and in every case the cyst appeared to be an incidental finding that did not correlate with the symptoms that prompted the scan in the first place.2American Journal of Roentgenology (AJR). MR imaging of CSF-like choroidal fissure and parenchymal cysts of the brain That pattern has held up over decades of subsequent research.
How They Are Usually Found
Most choroidal fissure cysts are discovered when someone gets an MRI or CT scan for headaches, dizziness, head injury, or another neurological complaint. The scan reveals the cyst, but the cyst turns out to have nothing to do with the problem that brought the person in. Doctors sometimes describe these as “incidentalomas,” findings that show up uninvited and cause more anxiety than clinical trouble. In one imaging study of 340 individuals that included both psychiatric patients and healthy controls, only a single choroidal fissure cyst was found, and it was in the control group, someone with no neurological or psychiatric symptoms at all.1Anatomy & Cell Biology. Choroidal fissure and choroidal fissure cysts: a comprehensive review
These cysts are genuinely rare. The total number of reported cases in the medical literature is small enough that individual case reports still get published. A review of published cases found only about 20 documented in the entire literature, which speaks to how uncommon they are even among findings that neurologists encounter.3Journal of Epilepsy Research. The Dilemma of Choroidal Fissure Cyst and Seizure That rarity is actually part of the problem when it comes to research: with so few cases, it has been difficult to run large studies or draw firm statistical conclusions about long-term behavior.
Do They Change Over Time?
One of the first questions people ask after learning they have a brain cyst is whether it will grow. For choroidal fissure cysts, the answer is usually no, but the picture is a little more nuanced than a flat reassurance. A study that tracked these cysts over time in 35 patients found that roughly two-thirds stayed the same size, about a third actually shrank, and only around 6% grew larger.4PubMed. Dynamic nature of choroid fissure cysts That means the odds strongly favor stability or even spontaneous reduction.
The exception worth noting is in young children. Among patients under five years old in that same study, the cysts were more dynamic in both directions: some grew and some shrank, with changes occurring in about three-quarters of cases rather than the one-third seen in older patients.4PubMed. Dynamic nature of choroid fissure cysts This does not necessarily mean the cysts are more dangerous in children, but it does mean pediatric neurologists tend to watch them more closely with repeat imaging.
When Problems Can Arise
Although the default behavior of these cysts is to sit quietly and cause no trouble, a small subset can produce real symptoms. A literature review found that the complications to watch for include increased intracranial pressure, seizures, focal neurological deficits, and in rare cases hydrocephalus, a buildup of fluid in the brain’s ventricles.5PubMed. Neuroendoscopic treatment of a rapidly enlarging choroidal fissure cyst: a case report and literature review These complications are linked to progressive enlargement of the cyst, which is itself uncommon.
One documented scenario involves bleeding inside the cyst. In one case, a 22-year-old woman presented with headaches and was found to have a left-sided choroidal fissure cyst. Over the next 20 months, follow-up imaging showed the cyst gradually growing, and she eventually arrived at the emergency department with severe headache caused by intracystic hemorrhage.6PubMed Central. Growing Hemorrhagic Choroidal Fissure Cyst Cases like this are published precisely because they are exceptional. But they illustrate why doctors do not simply dismiss the cyst forever after a single scan; periodic monitoring catches the rare cyst that misbehaves.
The Seizure Connection
Seizures are the symptom most commonly discussed alongside choroidal fissure cysts, and the relationship is genuinely debated among neurologists. Among the roughly 20 reported cases in one literature review, seizures were the main presenting symptom in about 65% of them, and the cysts were more often found on the right side of the brain.3Journal of Epilepsy Research. The Dilemma of Choroidal Fissure Cyst and Seizure That sounds like a strong association, but there is a selection bias at play: people with seizures are far more likely to get brain imaging than people without symptoms, so cysts in seizure patients are more likely to be found and reported. It does not mean the cysts caused the seizures.
The mechanism that could explain a link involves the cyst’s location. The choroidal fissure sits right next to the hippocampus, a brain structure deeply involved in seizure generation. When a cyst grows large enough to press on the hippocampus, it could plausibly irritate the surrounding tissue and trigger abnormal electrical activity. MRI in some reported cases has shown the hippocampus visibly compressed by the cyst.7PubMed Central. Temporal choroidal fissure cyst: a rare cause of temporal lobe epilepsy8Clinical Neurology and Neurosurgery. Choroidal fissure cyst in the temporal horn associated with complex partial seizure
Recent evidence has tilted toward accepting that at least some of these cysts genuinely trigger epilepsy rather than just sitting near it. In one case of drug-resistant epilepsy, detailed brain recordings confirmed that the seizure focus was adjacent to the cyst, specifically in the hippocampal head and body. After the cyst was surgically removed, the patient became seizure-free. The tissue removed showed no hippocampal sclerosis or other structural abnormality that could explain the seizures independently, which suggests the cyst itself was the culprit.9PubMed Central. Case Report: Seizure freedom after resection of a temporal choroidal fissure cyst in drug-resistant epilepsy Still, this remains an area where the evidence is thin. A handful of compelling case reports is not the same as a definitive large study, and researchers have acknowledged that the relationship between choroidal fissure cysts and seizures is genuinely controversial.7PubMed Central. Temporal choroidal fissure cyst: a rare cause of temporal lobe epilepsy
How Doctors Distinguish Them From Something Worse
The reason a choroidal fissure cyst can cause outsized worry is that, on a quick glance at a brain scan, a fluid-filled space in the temporal lobe could represent several different things, some of them serious. The early MRI literature flagged this explicitly: the imaging characteristics of these benign cysts need to be recognized so they are not confused with cystic tumors, areas of stroke, or parasitic infections.2American Journal of Roentgenology (AJR). MR imaging of CSF-like choroidal fissure and parenchymal cysts of the brain
The key features that point toward a benign choroidal fissure cyst are its location (squarely in the choroidal fissure), its signal characteristics on MRI (matching cerebrospinal fluid), and its behavior on advanced imaging sequences. One important tool is diffusion-weighted imaging, which measures how freely water molecules move. Benign choroidal fissure cysts and arachnoid cysts do not restrict water diffusion, while entities that can mimic them, like epidermoid cysts or brain abscesses, do restrict diffusion. That difference is diagnostic and reliably separates the benign cyst from things that need urgent treatment.10Journal of Contemporary Medicine. ADC Mapping in the Differential Diagnosis of Choroid Fissure Cysts and Arachnoid Cysts: A ROC Analysis-Based Study
If your radiologist has already identified the finding as a choroidal fissure cyst based on these criteria, the diagnostic heavy lifting is done. The anxiety most patients feel comes from reading the report before their doctor has walked them through what it means, and the clinical significance of the finding is almost always much less alarming than the language of a radiology report implies.
Monitoring and Treatment
The standard approach for an asymptomatic choroidal fissure cyst is regular follow-up imaging and nothing else. Surgery is reserved for people who develop symptoms that clearly relate to the cyst and interfere with daily life.1Anatomy & Cell Biology. Choroidal fissure and choroidal fissure cysts: a comprehensive review Among the reported cases reviewed in the literature where treatment was specified, all were managed conservatively, meaning no surgery was performed.3Journal of Epilepsy Research. The Dilemma of Choroidal Fissure Cyst and Seizure
When surgery is needed, the goal is to create a permanent opening between the cyst and the surrounding fluid spaces so the cyst can drain and stay decompressed. This is easier to describe than to accomplish. In one case involving a large cyst, doctors performed endoscopic fenestration, essentially punching a window in the cyst wall, but the opening closed on its own afterward. A drainage catheter was then placed, which became infected and had to be replaced with a more permanent shunting system.11PubMed. Surgical treatment of a patient with a giant choroidal fissure cyst: a case report This is not the norm, but it underscores that even when surgery is warranted, the procedure can be tricky and may require multiple interventions.
One practical frustration is that no one has established clear guidelines for how often follow-up scans should happen or at what point monitoring can safely stop. Researchers have acknowledged this gap directly: the recommended frequency of surveillance imaging and the appropriate point at which to discontinue follow-up remain unknown.12Journal of Epilepsy Research. The Dilemma of Choroidal Fissure Cyst and Seizure In practice, many neurologists will order a repeat MRI six to twelve months after the initial finding and then space out the interval if the cyst remains stable, eventually stopping routine imaging if there has been no change over several years. But this is a judgment call, not a protocol.
What to Do If You Have Been Told You Have One
If a choroidal fissure cyst shows up on your MRI, the most useful thing you can do is have a conversation with your neurologist or neurosurgeon about whether the cyst plausibly explains whatever symptom prompted the scan. In most cases, it will not. The cyst was there before your symptoms started and will likely still be there, unchanged, years from now.
Situations that do warrant closer attention include new or worsening seizures, progressive headaches, or any new neurological symptom in someone already known to have one of these cysts. If repeat imaging shows the cyst is growing, that shifts the conversation toward more active management. But even growth does not automatically mean surgery; the decision depends on whether the growth is causing symptoms or putting pressure on surrounding structures.
The emotional burden of knowing about a brain cyst is real and worth acknowledging. Radiologists sometimes include a line in their reports along the lines of “likely benign choroidal fissure cyst, recommend clinical correlation,” which is accurate but not exactly soothing to the person reading it at midnight on a patient portal. If the imaging characteristics match what is described above, and your doctor is not alarmed, the cyst is overwhelmingly likely to be a harmless anatomical variant that would never have been noticed a few decades ago, before MRI made it possible to see every small pocket of fluid in the brain.
Choroidal Fissure Cysts in Psychiatric Patients
An occasionally raised question is whether these cysts have any connection to psychiatric illness. Brain cysts of various types are found at slightly higher rates in post-mortem studies of patients with chronic psychiatric conditions, but that general observation has not extended to choroidal fissure cysts specifically. When researchers looked at brain scans of psychiatric patients alongside healthy controls, choroidal fissure cysts were vanishingly rare in both groups, with no meaningful pattern suggesting a link. The single case report of a choroidal fissure cyst in a patient with schizophrenia was notable partly because such a co-occurrence had never been published before, and the cyst was regarded as coincidental rather than contributory. If you have both a psychiatric condition and a choroidal fissure cyst, there is no established reason to think one caused or influenced the other.