Laser ablation is a type of surgery that uses light and heat to destroy (ablate) a small part of the brain that causes seizures.
First, a very thin catheter less than 2 mm in diameter is inserted into the brain through a small hole in the skull. Then, heat generated from the laser damages the DNA in the seizure-causing brain cells, leading to their death.
Laser ablation do not require craniotomy. Side effects of craniotomy, such as recurring headaches and risk of bone reabsorption, are avoided with laser ablation. If the lesion is deep in the brain, laser ablation also avoids extensive damage to normal brain tissue in the surgeon’s path. With laser ablation, patients often have a shorter hospital stay.
Through the years, laser ablation was not used frequently for several reasons. Sometimes the energy source is unreliable. If the laser probe is too hot, surrounding brain matter can be damaged. If the laser probe is not hot enough, the surgeon might need to ablate the area over and over again. Sometimes the size or volume of the lesion is too big, requiring the surgeon to make multiple passes to ablate the area.
MRI-guided laser ablation
In 2010, the U.S. Food and Drug Administration approved the Visualase Thermal Therapy System. This laser ablation system uses magnetic resonance imaging to monitor the surgery in real time. During the procedure, the surgeon views images so that the heated area can be mapped. This can avoid damage to surrounding healthy brain cells and also gives the surgeon a good idea of how much of the lesion has been ablated.
Other laser ablation systems exist today, including Neuroblate.
Can any pediatric neurosurgeon perform laser ablation?
No. Some epilepsy surgery hospitals do not have laser ablation systems, and not all pediatric neurosurgeons are trained in this technique. It is still a relatively new procedure that may be a good treatment option for children with epilepsy due to certain diseases.
When can laser ablation be used?
Generally, laser ablation can be used when the lesion in the brain is 1) in the gray matter; 2) focal, 3) well-defined, and 4) correlates with seizures on the EEG.
The most common cause of epilepsy treated with laser ablation is hypothalamic hamartomas. It can also be used to treat epilepsy due to cortical dysplasias, cortical malformations, hippocampal sclerosis, and tuberous sclerosis.
Some surgeons are now using laser ablation to disconnect white matter fibers. Examples include corpus callosotomy or to remove residual connections after a failed hemispherotomy. Functional hemispherectomy, or disconnection one hemisphere, has also now been performed with laser ablation.
In children with multiple focal areas of epilepsy, such as tubers caused by tuberous sclerosis complex, laser ablation avoids multiple craniotomies to access the tubers.
How does the surgeon place the laser probes in the brain?
It is very important that the laser fibers are accurately and safely placed in the brain. Most surgeons use stereotaxis – a three-dimensional, computer-based coordinate system that finds small targets in the brain. A special frame is placed on the head of the child and the surgeon uses the computer coordinates to identify the exact location of the lesion. The surgeon then inserts the laser probes manually through holes in the frame which represent the coordinates.
Some surgeons are now using robot-guided sterotaxis to accurately place the ablation catheter in the location of the lesion. The robot places the probes through guided computer coordinates.
Can laser ablation be used on large lesions?
Generally, no. Laser ablation can only be used on small lesions that are up to approximately two centimeters in size. However, larger lesions can sometimes be ablated if the surgeon makes several passes with the laser probe. Some surgeons now use multiple entry points and repetitive ablations for areas of brain with larger or multiple lesions, but large lesions are usually treated with traditional resection.
Is anesthesia required for laser ablation surgery?
Laser ablation for children is usually performed under general anesthesia.
Are there risks of laser ablation surgery?
Most children (78%) studied so far have not experienced any complications. According to the research literature, no children have died from the procedure. Severe complications that needed immediate attention happened to 3.4% of patients. Mild temporary complications were reported in 19% of patients. These included mostly temporary increase in seizures, difficulty with language and memory, and weakness. However, these mild complications usually resolved on their own. There was inaccurate catheter placement for only one patient, and software failure for one other.
Some research has shown that laser ablation for temporal lobe epilepsy can damage vision. This is because there is a structure close to the target that is important for vision. The structure is called the lateral geniculate nucleus, and it can be damaged by heat from the laser. Visual field cuts are the most common side effect in 5 – 29% of laser ablation surgeries in adults. These complications were not reported in the studies on children.
What are the chances of seizure control with laser ablation?
Because laser ablation is a relatively new surgical technique, the published research studies each have very few patients. One study reviewed all of the pediatric patients in the literature and summarized the findings of 179 children that were reported. They found that, overall, the rate of seizure freedom was 57.5%. For certain causes of epilepsy, this rate is lower compared to traditional surgery. However, the cognitive outcome is thought to be improved with laser ablation.
What other effects can laser surgery have on the child?
There is very little research which discusses the cognitive effects of laser surgery on children. One paper discusses temporary, non-disabling memory impairments after surgery in one child.
In adults, early research of laser ablation of the temporal lobe shows that laser ablation patients may experience fewer cognitive effects compared to those who have traditional anterior temporal lobectomy. Experts predict that laser ablation will cause less cognitive impairment because it is less invasive than resection. However, there are no studies comparing those cognitive outcomes.
What is the cost of laser ablation?
Some insurance companies do not cover laser ablation because they consider it to be experimental. Laser ablation can cost upwards of $40,000 per procedure.