A cavernous malformation, or cavernoma, is a cluster of abnormal blood vessels that occasionally bleeds and slowly grows. Many are found by accident on a scan and never need treatment; some can cause seizures while others, especially in the brainstem, can be a source of recurring or accumulating symptoms.
A cluster of leaky small blood vessels that grows slowly, mostly through repeated tiny bleeds that often go unnoticed.
A cavernous malformation (also called a cavernoma or cavernous angioma) is a cluster of abnormal, thin-walled blood vessels bunched together, often compared to a small berry or mulberry. Unlike the brain's normal arteries and veins, these channels lack a proper muscular wall, so instead of moving blood along under pressure, they tend to ooze. Most cavernomas leak tiny amounts of blood into their own tissue over and over across a lifetime, gradually building a rim of dark, iron-containing residue called hemosiderin around the lesion. It is this slow, largely silent accumulation, not one dramatic event, that is the hallmark of how these lesions grow and change.
Cavernomas can occur anywhere in the brain or spinal cord and are usually a lifelong, one-time finding (sporadic). In roughly one in five patients, though, they are familial: an inherited mutation in one of three known genes causes multiple cavernomas to form, sometimes dozens over a lifetime, and other family members may carry the same risk.
Because MRI is used so often now, for headaches, minor trauma, or a completely unrelated symptom, a growing share of cavernomas are discovered incidentally: an unexpected finding on a scan ordered for something else entirely. Finding one does not automatically mean anything needs to be done about it. Your neurosurgery team will weigh the lesion's location and whether its causing symptoms to recommend watchful waiting, microsurgical removal, or, for deep or higher-risk locations, minimally invasive laser ablation (LITT).
Cavernomas can form almost anywhere in the brain or spinal cord, and where one sits shapes a patient's experience more than almost any other factor. Select a brain region to see the typical symptoms associated with each location and the neurologic risk from bleeding.
The risk of symptomatic bleeding is low for most cavernomas. Once bleeding causes symptoms, treatment becomes a greater consideration.
Bleeding-risk statistics like these come from studies that count bleeds doctors were able to detect and diagnose. A tiny bleed in a crowded, sensitive area like the brainstem is far more likely to cause an obvious symptom, get imaged, and get counted than the same-sized bleed somewhere quieter, which might cause no symptoms at all and go unnoticed. The same issue applies to rebleeding: once a cavernoma has been diagnosed, patients are usually watched more closely with follow-up scans, so a second bleed is more likely to be caught than the first one was. None of this means the patterns on this page aren't real. Most researchers believe genuine differences in risk by location, and after a first bleed, do exist. But the exact numbers are harder to pin down than a single percentage suggests, which is part of why you may hear somewhat different figures from different providers. The broad pattern holds regardless: an unbled, incidentally found cavernoma is usually low risk, and one that has already caused a bleed, especially with symptoms, deserves closer attention.
Cavernomas that has never bled and are causing no symptoms carry a relatively lower annual hemorrhage risk, on the order of 0.5% per year across most locations. But once a cavernoma has bled once, the risk of a second bleed rises for the following year or two before gradually falling back toward its original baseline if no further bleeding occurs. Some of that apparent rise is likely inflated by closer monitoring after a diagnosis, which makes a second bleed more likely to be caught than the first one was, but most researchers believe a real, biological increase in risk exists too. This is why a prior hemorrhage, the resulting symptoms, and location, shape the recommendation for surgery.
About one in five patients has the inherited, familial form, caused by a mutation in one of three known genes (CCM1/KRIT1, CCM2, or CCM3/PDCD10). Patients with the familial form typically develop multiple cavernomas, sometimes dozens, that can continue to appear over a lifetime rather than a single fixed lesion. When a familial pattern is suspected, most often because of multiple lesions on imaging or a family history, your team will often coordinate genetic counseling and screening for at-risk relatives.
No single factor decides this alone. Explore the considerations that go into the recommendation below.
Watchful waiting, microsurgical resection, and laser ablation (LITT) each fit a different clinical picture.
Watchful Waiting
Microsurgical Resection
Laser Ablation (LITT)
Click an icon to highlight that option's column in the tables below.
| Watchful Waiting | Microsurgical Resection | Laser Ablation (LITT) | |
|---|---|---|---|
| What it is | No procedure; regular MRI follow-up and symptom monitoring | Open surgery through a small window in the skull to remove the entire cavernoma | A thin laser fiber, guided into the cavernoma through a tiny hole in the skull, heats and destroys it from within |
| Invasiveness | None | Open cranial surgery | Minimally invasive; a single probe track roughly the width of a pencil lead |
| Anesthesia | None | General | General |
| Typical hospital stay | None | 3–5 days | Usually one night |
| Watchful Waiting | Microsurgical Resection | Laser Ablation (LITT) | |
|---|---|---|---|
| Best for | Asymptomatic, incidentally found lesions, especially in the cerebral lobes; any lesion where the estimated surgical risk outweighs its natural bleeding risk | A lesion that has bled and caused symptoms, especially one that is superficial or reachable without crossing critical brain tissue; medication-resistant seizures traced to a lobar cavernoma | Deep or eloquent lesions, including selected brainstem and thalamic cavernomas, where a traditional surgical corridor would risk more collateral injury than a single thin probe track |
| Watchful Waiting | Microsurgical Resection | Laser Ablation (LITT) | |
|---|---|---|---|
| What to expect | Requires periodic MRI on an individualized schedule; no recovery time, but the lesion and its risk remain in place | Complete removal, including the hemosiderin rim when treating seizures, essentially eliminates future bleeding risk from that specific lesion; recovery is measured in weeks | Recovery from a laser procedure is typically a few days to a week or two |
Select each step to learn what happens and why. Toggle between microsurgical resection and laser ablation.
Evidence-based outcomes drawn from published microsurgical and laser series.
Every option carries some risk. Watchful waiting carries the ongoing, if usually low, risk of a future bleed from the lesion left in place. Microsurgical resection carries the general risks of any brain operation, including infection and bleeding, plus the possibility of a new or worsened neurological deficit that is temporary in most patients but can occasionally be permanent, with that risk rising for deeper and brainstem locations. Laser ablation avoids an open incision, but it is not risk-free either: roughly 1 in 7 patients experience a new neurological symptom immediately afterward, most of which resolve; and because the lesion is destroyed rather than removed, there have been rare reports of delayed swelling around the treated area in the weeks that follow. Your surgical team will walk through the specific risks that apply to your lesion's size, location, and your own health before any decision is made.
Brown Neurosurgery's Cerebrovascular Surgery and Endovascular Neurosurgery team evaluates every cavernous malformation individually, offering both open microsurgical and minimally invasive treatment.
