Stereotactic is a general term that refers to how a brain is positioned and mapped for any kind of intervention. It uses MRI with a 3-dimensional coordinate system to precisely locate small targets in the brain. Stereotactic procedures are used in traditional surgery (open resection), laser surgery, and radiosurgery.
Stereotactic Laser Ablation
CO2 laser devices have been used in traditional open surgery for many years. Most recently, new technology in laser surgery has allowed it to be used through very small openings in the skull.
Stereotactic laser ablation (SLA) is also known as magnetic resonance (MR) thermography-guided laser interstitial thermal therapy (LITT). It is a technique in which a small opening is made in the skull to allow a laser device to be inserted into the brain through a catheter. SLA uses using real-time MR thermography to coagulate tissue at 50–90°C (122-194°F) while allowing the surgeon to see the nearby structures that need to be protected. LITT has been found to be an effective treatment for lesions that are causing epilepsy.
Although the number of treated patients is still small, SLA use is becoming widespread around the United States as an alternative to traditional open resection. When SLA is not successful at controlling seizure, it can be followed by open resection. SLA is not used for cavernous angiomas that have recently hemorrhaged.
This manufacturer-created video demonstrates the use of LITT. Angioma Alliance does not endorse the use of any particular LITT system.
Stereotactic radiosurgery (SRS) is a non-invasive technique in which a focused beam of radiation, accurate to 1 to 2 mm, targets a lesion. Stereotactic radiosurgery is also known as gamma knife or Cyberknife, and it does not involve opening the skull.
This technology has been in use for many years but with a great deal of controversy. SRS does not remove the cavernous angioma. Instead, it damages the DNA of cavernous angioma cells which makes them unable to reproduce. This is a process that occurs over time, and it is believed that it requires up to 2 years to reduce the risk of hemorrhage from a lesion that has received SRS.
Gamma Knife and Cyberknife technology are explained in this video, which is not specific to cavernous angioma.
One controversy with the use of SRS is the risk of increased symptoms or disability, which may occur through edema after the procedure or through necrosis of surrounding brain tissue 6-9 months later. The use of smaller radiation doses has reduced the incidence of this.
Additionally, it is believed that SRS can cause the formation of additional lesions in those with the hereditary form of CCM illness.
Finally, because cavernous angiomas that have hemorrhaged generally re-hemorrhage less after 2 years of being hemorrhage-free, it’s difficult to determine whether the reduced hemorrhage rate two years after SRS is due to radiosurgery or whether it’s simply what would have happened with no intervention.
In the United States, SRS is reserved for lesions that are highly symptomatic and for which there are no other options. The Angioma Alliance Clinical Care Consensus Guidelines discuss recommended uses in more detail. In the UK and Europe, the technique is used more frequently. A long-term randomized study is beginning in the United Kingdom.
Tubular retractors are tools that are used during surgeries to remove cavernous angiomas in subcortical areas (deep-seated in the brain) and those in eloquent areas where control of a critical function is located. Tubular retractors allow for safer access to the lesion with a smaller surgical opening. They do this by distributing retraction pressure radially.
Recent comparative research at the University of Miami using BrainPath (NICO Corporation) and ViewSite Brain Access System (Vycor) indicates that either can be used safely and effectively. Surgery to remove a cavernous angioma using the BrainPath system can be seen in this video (warning, graphic content).