June 2, 2019 By ashwin
Multiple Subpial Transections (MST)
Multiple subpial resections are an alternate type of surgery that is used if seizures begin in a region of the brain that cannot be removed safely. This would include areas in the brain that control speech or movement.
This surgical procedure involves the neurosurgeon opening the skull and making a series of fine shallow cuts (transections) into the brain’s gray matter just below the pia mater. The pia is a delicate membrane that surrounds the surface of the brain. The cuts (transections) work by interrupting fibers that are thought to be involved in the spread of electrical seizure activity.
Sometimes MST are done in combination with a surgical resection when a part of the seizure focus is in a critical region (speech or movement) of the brain and a complete resection of the seizure focus is not possible.
Laser Interstitial Thermal Therapy (LITT)
Laser interstitial thermal therapy is sometimes called laser ablation surgery. During the surgery, a MRI (magnetic resonance imaging) is used to precisely map out the exact area of the brain to operate on. Laser is then delivered with pinpoint accuracy to this area to eliminate the seizure focus. All of this is done without needing to open the skull, making it a minimally invasive procedure.
This minimally invasive surgery can be effective for drug resistant focal epilepsy due to small lesions. This treatment has been used most commonly in people with temporal lobe epilepsy from mesial temporal sclerosis (scar tissue in the temporal lobe). People most appropriate for this type of surgery include
- People who have a clearly defined area of brain where seizures begin
- People who would benefit from a less invasive approach to epilepsy surgery
The advantages of this therapy compared to invasive epilepsy surgery include
- Shorter procedure
- No craniotomy (opening skull to access brain) required
- Shorter hospital stay
- Possibly, a reduction in complications and side effects
Early data on laser ablation surgery shows more than half of people treated with LITT achieve freedom from seizures.This type of surgery continues to be carefully studied. A multicenter clinical trial is ongoing to assess the safety and effectiveness of this procedure in individuals with mesial temporal sclerosis.
Anatomical or Functional Hemispherectomy and Hemispherectomy
These types of epilepsy surgery are almost exclusively performed in children with seizures coming from a large area on one side of the brain (hemisphere). The procedures involve separating the area of seizure onset from the rest of the brain. This typically is reserved for children with very large areas of seizure onset.
- Anatomic hemispherectomy involves removing the frontal, parietal, temporal, and occipital lobes on one side of the brain. Deeper brain structures (basal ganglia and thalamus) are left in place. This type of hemisphere surgery has higher risk and is usually considered for people with hemimegalencephaly (a rare condition where one side of the brain is abnormally larger than the other).
- Functional hemispherectomy involves removing a smaller area of the affected hemisphere and disconnecting the remaining brain tissue. This surgery involves less risk but is only helpful in a select group of people.
- Hemispherotomy is different than hemispherectomy as less brain tissue is removed to decrease the risk of complications from surgery. In this type of surgery, the surgeon is makes a hole or several holes in the hemisphere instead of removing large sections of the brain.
The results of these surgical procedures are very good. Generally over 80% of people have markedly improved seizure control and many are able to be free of seizures. The outlook for seizure control may be lower if a person has a progressive disorder, such as Rasmussen’s syndrome.
Corpus callosotomy is usually reserved for people with severe generalized epilepsy (meaning seizures involve both sides of the brain) who are subject to drop attacks (atonic seizures) and falls. The procedure involves splitting the main connection pathway between the two cerebral hemispheres (sides of the brain).
Individuals being considered for this operation usually have
- Frequent tonic, atonic, atypical absence, or tonic-clonic seizures
- Developmental delay
- Disabling seizure-related falls
Stereotactic radiosurgery uses many precisely focused radiation beams to treat the area of the brain where seizures begin (seizure focus). There are several different types of stereotactic radiosurgery. They are considered minimally invasive as the surgeon does not have to open the skull for the procedure. Stereotactic radiosurgery uses 3-D imaging to target high doses of radiation to the seizure focus with minimal impact on the surrounding healthy tissue.