Who are candidates for laser surgery?
Epilepsy affects 65 million people worldwide, and 1 of every 3 three individuals with epilepsy is resistant to medical seizure management. Pharmacoresistance means failure of an adequate trial of at least 2 well-tolerated antiepileptic medications to produce seizure freedom.1
When a person fails medical management, the next step in treatment is surgical evaluation, which aims to identify the seizure focus and assess whether its surgery is a treatment option. Of focal epilepsies, mesial temporal lobe epilepsy (MTLE) is the most common and is hence the most frequent epilepsy that is treated surgically. It accounts for 17% to 31% of all surgical procedures done for epilepsy.2 Therefore, we will use the treatment of MTLE in this discussion to compare open surgical craniotomy procedure versus Laser Interstitial Thermal Therapy (LITT) as treatment options for refractory epilepsy.
What’s wrong with our current approach to epilepsy surgery?
The most common surgical procedure and the current gold standard for treatment in pharmacoresistant MTLE is very invasive. The procedure involves a prolonged operation where a piece of bone is removed from the skull. After the bone is removed, about 4 to 6 cm of the anterior (front) part of the temporal lobe, along with the amygdala and hippocampus on the same side, are removed. In medical terms, the procedure is called open craniotomy with anterior temporal lobectomy, including amygdalohippocampectomy (ATLAH).
This process has been proven to be effective in randomized controlled trials that showed ATLAH surgery leads to greater seizure freedom and improved quality of life compared to medical management alone. However, people who undergo this procedure on their dominant hemisphere (one that is responsible for language and verbal memory) may sustain neurocognitive deficits, including memory and naming difficulties.3-4
Therefore, more selective, less invasive procedures have been studied to help decrease impairment and recovery time.
The Nuts and Bolts of Laser Surgery for Epilepsy
The use of LITT, also known as thermal ablation, is currently growing as an alternative to the more invasive open craniotomy. LITT uses laser technology to deliver a set amount of energy to a specific brain region, where laser energy transforms into thermal energy. Temperatures between 45 and 60 degrees Celsius lead to rapid, irreversible tissue damage. This process is how LITT achieves cell death in the brain region where seizures originate, thus achieving seizure control.
LITT is less invasive because it is performed through a small stab incision on the scalp and a very small hole in the skull. Then a small 1.65 mm diameter catheter is placed into the target area of the brain using a stereotactic system (a frame that provides stabilization and precise measurements) to ensure proper placement. Then the person is taken to the magnetic resonance imaging (MRI) machine for guided ablation (removal) of the target tissue.
For the treatment of MTLE, the amygdala and the hippocampus are the selected targets for ablation. The MRI machine is used during the ablation procedure to monitor the temperature in the brain and to help accurately treat deep brain structures without damaging adjacent critical structures.
At this time, there are two FDA approved commercialized systems in the U.S. used for LITT, the Visualase system and the NeuroBlate system.1
How effective is laser surgery for epilepsy?
Unlike ATLAH, LITT has not undergone any randomized control trials. Therefore, all the current data is taken from either small prospective single institution case series or retrospective reviews.
Current data show that more than half of the people treated with LITT achieve seizure freedom.
- A case series of 13 people5 reported 54% achieved freedom from disabling seizures and 30.8% became completely seizure free at 2 year follow up.
- A similar study6 reported seizure freedom rate of 80% at 1 year follow up after LITT treatment in 2015.
- A more recent review7 in 2016 found 53% of the people were seizure free at one year follow up.
ATLAH has a documented effectiveness of 60% to 80%.
These data show LITT is about as effective as ATLAH at obtaining seizure freedom in people with medically refractory MTLE.3-4 Moreover, LITT has been shown to have better neurocognitive outcomes compared to ATLAH, especially when the dominant language hemisphere is the one being treated.2 It has also been shown to reduce the length of hospital stay and overall recovery period compared to ATLAH surgery.
At this time, open surgery is still the gold standard for the treatment of medical refractory MTLE. However LITT appears to be a highly promising alternative.
- The current data show that the seizure freedom outcomes after LITT are comparable to those of ATLAH with reduced surgical time, hospital length of stay, and recovery time.
- The less invasive aspect of the LITT surgery makes it a great alternative to ATLAH for people at a high-risk for surgery or adverse to the idea of open cranial procedures.
Therefore, LITT is a viable option as an alternative to open surgery for the treatment of MTLE and, with continued work and research, its efficacy and indications for use in the treatment of refractory epilepsy will expand.
- Wicks RT. Neurosurgery: Laser Interstitial Thermal Therapy for Mesial Temporal Lobe Epilepsy. Williams & Wilkins Co; 12/2016;79 Suppl 1:S83.
- Attiah MA. Epilepsy research: Anterior temporal lobectomy compared with laser thermal hippocampectomy for mesial temporal epilepsy: A threshold analysis study. Elsevier; 09/2015;115:1.
- Engel JJ. JAMA : the journal of the American Medical Association: Early surgical therapy for drug-resistant temporal lobe epilepsy: a randomized trial. American Medical Association; 03/2012;307:922.
- Wiebe SS. The New England journal of medicine: A randomized, controlled trial of surgery for temporal-lobe epilepsy. Massachusetts Medical Society; 08/2001;345:311.
- Willie JT. Neurosurgery: Real-time magnetic resonance-guided stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy. Williams & Wilkins Co; 06/2014;74:569.
- Waseem HH. Epilepsy & behavior: Laser ablation therapy: An alternative treatment for medically resistant mesial temporal lobe epilepsy after age 50. Academic Press; 10/2015;51:152.
- Waseem HH. Journal of clinical neuroscience: MRI-guided laser interstitial thermal therapy for treatment of medically refractory non-lesional mesial temporal lobe epilepsy: Outcomes, complications, and current limitations: A review. Elsevier; 12/2016.