By: Mohammad Hassan Bagheri, Dr. Fatemeh Jafari, MD, and Dr. Milad Shafizadeh
Photo Credit: The Defeating Epilepsy Foundation
Mohammad Hassan Bagheri is an MD Candidate at the Tehran University of Medical Sciences. Dr. Fatemeh Jafari is an Assistant Professor of Radiation Oncology at the Tehran University of Medical Sciences. Dr. Milad Shafizadeh is an Assistant Professor of Neurosurgery at the Tehran University of Medical Sciences. The Defeating Epilepsy Foundation thanks Mohammad, Dr. Jafari, and Dr. Shafizadeh for their research and dedication to help improve treatments and the quality of life for patients.
Introduction
If you or a loved one has been diagnosed with a brain tumor, you may have heard the term stereotactic radiosurgery, or SRS. Despite the word “surgery,” SRS does not involve a surgical incision or opening the skull. Instead, it uses precisely focused radiation to treat a specific area of the brain.
SRS is used to treat certain brain tumors and other abnormalities. In selected situations, it can also be used for epilepsy that has not responded adequately to medication.
What is stereotactic radiosurgery?
SRS is a highly precise form of radiation therapy. Radiation beams are aimed at a specific target from different directions. The treatment is planned so that the radiation dose is concentrated as much as possible within the target while limiting exposure to nearby healthy tissue.
Before treatment, doctors use detailed imaging, usually MRI or CT, to determine the location and shape of the area being treated. The radiation team then uses these images to create an individualized treatment plan.
Unlike traditional brain surgery, SRS does not require an incision or a craniotomy, which means the skull does not need to be opened. Depending on the treatment system and the patient’s needs, a specialized head frame or custom mask may be used to keep the head in the correct position. Some patients may also receive medication to help them relax or, in selected situations, anesthesia.
SRS may be delivered in a single treatment or over several sessions. The number of treatments depends on the size, location, and type of abnormality being treated.
What conditions can SRS treat?
SRS is used for several conditions affecting the brain.
One of its common uses is the treatment of brain metastases, which are cancers that have spread to the brain from another part of the body. It can also be used for certain benign tumors, including meningiomas and vestibular schwannomas, sometimes called acoustic neuromas. Selected pituitary tumors may also be treated with SRS.
Another use is the treatment of certain vascular abnormalities, including arteriovenous malformations (AVMs).
SRS has also been studied as a treatment for selected forms of drug-resistant epilepsy. This is a much more specialized use of radiosurgery and is generally considered only when there is a well-defined target that can be treated safely. Hypothalamic hamartoma is one example.
How does SRS treat a brain tumor?
Radiation does not usually make a tumor disappear immediately. Instead, it damages the DNA of the targeted cells and interferes with their ability to survive and reproduce. The effects of treatment can therefore develop gradually.
Depending on the type of tumor and the reason for treatment, the goal may be to stop the tumor from growing, reduce its size over time, or control it while limiting symptoms.
Because there is no surgical incision, many patients can go home the same day after SRS. Recovery is generally shorter than after open brain surgery, although the experience varies from person to person and depends on the condition being treated.
Can SRS be used to treat epilepsy?
For some people with drug-resistant epilepsy, SRS may be an option when seizures arise from a small, well-defined area of the brain that can be safely targeted.
One example is hypothalamic hamartoma (HH). These are rare, noncancerous lesions in the hypothalamic region that can cause difficult-to-control seizures. SRS has been used to treat selected patients with HH, particularly when other approaches may be difficult or carry substantial risks.
The effect of SRS on seizures is usually delayed. Unlike a procedure that immediately removes or ablates abnormal tissue, radiation produces its effects gradually, so seizures may continue for some time after treatment.
A 2025 systematic review and meta-analysis of seven studies involving 152 people with hypothalamic hamartoma found that about 77% experienced improvement in seizures, while about 48% became seizure-free after SRS. However, the studies differed in their treatment methods and patient characteristics, and the researchers reported substantial variation in the seizure-free results. These numbers therefore should not be interpreted as a guarantee of what will happen for an individual patient.
SRS is not the right treatment for everyone with epilepsy or every person with a hypothalamic hamartoma. Other approaches, including laser ablation and radiofrequency thermocoagulation, may be considered depending on the location and characteristics of the lesion. The choice should be made by a team experienced in treating epilepsy and hypothalamic hamartoma.
How is SRS different from open brain surgery?
The most obvious difference is that SRS does not require a traditional surgical incision or opening of the skull.
This can mean a shorter recovery and less disruption to daily activities for appropriately selected patients. It can also be useful when a lesion is located in a part of the brain where open surgery would be difficult or risky.
But SRS is not automatically safer or better than surgery. Some tumors are better treated with surgical removal, particularly when a tumor is large, is causing significant pressure on the brain, or when tissue is needed to establish a diagnosis.
The choice between SRS, open surgery, conventional radiation therapy, medication, or observation depends on the individual patient, the condition being treated, and the goals of treatment.
What are the possible side effects?
SRS is generally well tolerated, but side effects can occur.
Some people experience fatigue, headache, nausea, or temporary swelling around the treated area. The symptoms depend partly on where the treatment is delivered.
A less common but important delayed complication is radiation necrosis. This occurs when tissue in or near the treated area becomes damaged after radiation. It can develop months or even years after treatment and may cause headaches, seizures, or other neurological symptoms.
The risk of symptomatic radiation necrosis is not the same for everyone. It depends on factors such as the size and location of the treated area, the radiation dose, the treatment schedule, and whether that part of the brain has received radiation before.
Because the risk varies between patients and treatment settings, there is no single percentage that accurately represents the risk for everyone undergoing SRS.
If radiation necrosis develops, treatment depends on its severity and the symptoms it causes. Some patients may be treated with corticosteroids or other medications, while more serious cases may require additional treatment.
What should I expect after SRS?
Because SRS does not involve opening the skull, recovery is generally different from recovery after open brain surgery. Many patients are able to return home on the day of treatment.
You may still experience fatigue, headache, or other temporary symptoms. Your doctor will usually schedule follow-up visits and imaging to monitor the treated area.
A treated tumor or other abnormality may remain visible on an MRI even when treatment has been successful. Changes on follow-up scans therefore need to be interpreted by your medical team rather than viewed in isolation.
Contact your healthcare team if you develop new or worsening neurological symptoms, persistent headaches, seizures, weakness, problems with speech or vision, or other symptoms that concern you.
What should I remember?
Stereotactic radiosurgery is a highly precise form of radiation therapy that can treat certain brain tumors and other abnormalities without the need for traditional brain surgery.
For epilepsy, SRS is a specialized treatment option rather than a routine therapy. It may be considered for selected people with drug-resistant epilepsy, including some patients with hypothalamic hamartoma. Current evidence suggests that SRS can reduce seizures in appropriately selected patients, but the treatment effect is delayed and seizure freedom is not guaranteed.
If your doctor has recommended SRS, ask why it is being considered, what other treatment options are available, how long it may take to see the treatment effect, and what side effects or long-term risks apply to your particular situation.
