Stereotactic Radiosurgery
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Stereotactic radiosurgery is a non-invasive operation that is commonly used to treat an array of diagnoses, including brain tumors, pituitary tumors and arteriovenous malformations but also less life threatening conditions like trigeminal neuralgia and essential tremor.
How Does It Work?
Stereotactic radiosurgery uses highly focused radiation to treat a very precise target in the brain. Unlike traditional forms of radiotherapy, stereotactic radiosurgery is capable of precisely delivering high-focal radiation to the targeted area without causing damage to the surrounding tissue. The radiation is also delivered in a single session which significantly reduces the risk of causing unwanted damage.
Stereotactic radiosurgery does not require the use of any incisions. A detailed MRI of the area will be used to precisely plot where the high focal radiation will be delivered. There are several different machines that can be used to deliver the radiation to the area. The Novalis system is the most advanced option and is capable of precisely shaping the radiation beam to perfectly fit the shape of the targeted area.
Trigeminal Neuralgia
Similar to other treatments for trigeminal neuralgia, stereotactic radiosurgery provides pain relief by precisely damaging the trigeminal nerve to prevent the transmission of pain. For trigeminal neuralgia, the focused radiation is targeted at the region where the trigeminal nerve exits the brain. The procedure is painless and we offer this procedure without the need for a frame (as is required for Gamma Knife).
The non-invasive nature of the procedure means that there is no down time required once the procedure is complete. Patients can walk out of the clinic and continue on with their normal daily lives immediately. It can take two to six days to experience the benefits of the procedure. Stereotactic radiosurgery has a 70-80% success rate and is capable of providing long-lasting results. In some cases, pain may recur in up to 30% of cases. In these cases, the procedure can be repeated.
Brain Metastases
Stereotactic radiosurgery is often the first line treatment for patients with brain metastases. Several clinical trials demonstrate the efficacy of stereotactic radiosurgery for brain metastases, providing control of these tumors without surgery in up to 90% of cases. Stereotactic radiosurgery can be used to treat up to 10 brain metastases simultaneously. By avoiding whole brain radiation, the long term complications of cognitive difficult can be avoided. However, in some cases, whole brain radiation may still be required, especially when there are more than 10 metastases or evidence of leptomeningeal disease (tumor in the spinal fluid). The risks of radiosurgery are relatively small, with a 5% risk of radiation injury, which can usually be managed with a brief course of steroids. In rare cases, surgery may be required. Recently, when surgery is required, we use a minimally invasive technique called Laser Interstitial Therapy to treat the tumor through a 4 mm incision. Dr Pouratian is a leading surgeon in this area, teaching other surgeons around the country on how to use this approach.
Similar to other treatments for trigeminal neuralgia, stereotactic radiosurgery provides pain relief by precisely damaging the trigeminal nerve to prevent the transmission of pain. For trigeminal neuralgia, the focused radiation is targeted at the region where the trigeminal nerve exits the brain. The procedure is painless and we offer this procedure without the need for a frame (as is required for Gamma Knife).
Pituitary Tumors
Pituitary tumors are the most common type of brain tumor. In many cases, they are discovered incidentally and nothing needs to be done. If and when you are diagnosed with a pituitary tumor, the first step is to determine if the tumor produces hormones, as this can impact management.
Treatment options for non-functioning tumors (i.e., those that do not produce hormones) include observation and possible surgery. For tumors that are incompletely resected, there is a 50% chance of tumor recurrence within 10 years. Even for patients with complete tumor resections, the chance of recurrence can approach 10% over 10 years. Stereotactic radiosurgery can be used in the setting of a incompletely resected tumor or at the time of recurrence, providing a 90-95% chance of tumor control over a 10 year period.
When patients have a functioning pituitary tumors, treatment options are directed not only at controlling tumor growth but also hormone production. For prolactionomas, first line therapy is medical therapies. Endocrinologists manage these conditions. For other functioning tumors (growth hortomone secreting (acromegaly), ACTH secreting (Cushing’s disease), and others), surgery is often first line. When the tumor cannot be completely resected or if there is still evidence of hormone production, stereotactic radiosurgery can be used. Like with non-functioning tumors, stereotactic radiosurgery can control tumor growth in 90-95% of cases. Hormone production however does not respond as well, and depends on the tumor type, varying from ~30% in prolactinomas to 60-80% in GH- and ACTH-secreting tumors. It can take 1-2 years to see a change in hormone production after stereotactic radiosurgery.
The primary risks of stereotactic radiosurgery for pituitary tumors is the risk to the optic nerves and the normal pituitary gland. When done properly, the risk to the optic nerves should be <1%. It is critical to be treated by an experienced physician like Dr Pouratian to ensure success. Loss of pituitary function can be common after pituitary stereotactic radiosurgery, in up to 30-40% of cases (most often affecting thyroid hormone). While no one wants to lose normal function, if followed regularly by an endocrinologist, these hormones can be replaced with minimal impact on normal day-to-day life.
Meningiomas
Meningiomas are also very common brain tumors, that actually reside on the surface of the brain. Surgery can provide a definitive cure. Depending on age, location, and size, radiosurgery can also be an alternative treatment options. Control rates are nearly 90%, but require regular follow-up. Risks are minimal, but depend on the location of a particular tumor.
Cerebral Arteriovenous Malformations
Cerebral arteriovenous malformations (AVMs) are usually a congential abnormality of blood vessels in the brain. AVMs can actually occur in other locations in the body as well, like the lung. These are usually isolated lesions, but can sometimes be part of a syndrome, like VHL. AVMs can be discovered incidentally (by luck without symptoms), or due to symptoms related to bleeding or seizure. Treatment is aimed at reducing the risk of symptoms or catastrophic bleeding. Like other diagnoses, treatment depends on age, location, size, and associated symptoms. Surgical resection, if possible, should always be considered first, as this can be curative. When stereotactic radiosurgery is used in small AVMs (less than 2-3cm), success rates are nearly 80-90%. When AVMs are large, various advanced strategies are employed, including treatment over several days or over several months. Dr Pouratian is one of the only surgeons in the country using these advanced techniques to treat some of the most complex AVMS. Whether small or large, AVMs take a long time to respond to radiation and require long term follow-up. Risks include the risk of radiation toxicity, which can result in brain swelling in 5-8% of patients. This is usually most effectively managed with steroids for a brief period of time.
Essential Tremor
Essential tremor is the most common cause of tremor. Treatment is initiated when the tremor interferes with activities of daily living. First line medical therapies include propranolol and primidone. While second like medical therapies exist, when tremor is severe and disabling, surgical therapies can and should be considered. Options include deep brain stimulation, MRI-guided focused ultrasound, and radiosurgical thalamotomy. When treated with stereotactic radiosurgery, patients can only be treated on one side of the brain (due to unique risks of swallowing and walking difficulties when treating both sides of the brain). An average 50% improvement of tremor is seen in up to 90% of patients by targeting the focused radiation at a region of the brain called the thalamus. It can take about 6 months to respond to stereotactic radiosurgery. While an attractive option, the doses used for radiosurgical thalamotomy are nearly 10x that used for brain tumors and while we know where to target the radiation (and Dr Pouratian has developed new methods with advanced imaging to better target the thalamus), there is no means for testing the target. Therefore, there may be increased risk of complications compared to more invasive procedures, like deep brain stimulation surgery.
