This technology has replaced the need for open craniotomy when destroying diseased brain tissue in epilepsy patients
Stereotactic laser ablation is a relatively new method of destroying epileptogenic lesions. Emory Epilepsy Center neurosurgeon Robert E. Gross, MD, PhD, was the first neurosurgeon in the nation to use it as a treatment for epilepsy in adults. Since then, Dr. Gross has performed upwards of 200 stereotactic laser ablations and says the minimally invasive technology has all but eliminated the need for open surgery on patients with epilepsy.
The following case study demonstrates the effectiveness of this surgical approach and the benefits of having a collaborative team of physicians specializing in all aspects of epilepsy care.
The patient, a 38-year-old male, had been experiencing tonic-clonic seizures for three years. Seizures would begin without warning and were characterized by loss of awareness, lip-smacking and grunts, progressing quickly to loss of awareness and whole-body convulsions. These seizures occurred once to twice a month, usually at night and sometimes in clusters. Three medications prescribed for him at a different institution failed to provide seizure freedom. The seizures were taking a toll on his personal life and affecting his job.
The patient sought a comprehensive evaluation at Emory’s Level-4 Epilepsy Center. Recognizing that a fourth anti-seizure medication was highly unlikely to achieve seizure freedom, the epilepsy team recommended a surgical evaluation.
The first step of the evaluation was to do a seizure-protocol magnetic resonance imaging (MRI) scan. This revealed scarring in the left temporal lobe that was characteristic of medialtemporal sclerosis, also referred to as hippocampal sclerosis. This finding correlated with the patient’s semiology (the signs and behavioral changes occurring with the seizure) consistent with seizure onset in the medial temporal lobe.
The next step was to correlate these anatomical findings with electroencephalography (EEG) patterns with long-term video EEG monitoring. Anti-seizure medications are reduced and the patient is monitored continuously for a week in the hospital. During the patient’s evaluation, 20 scalp EEG electrodes recorded four seizures in the left temporal lobe. The video confirmed the patient’s seizure semiology of lip-smacking, loss of awareness and behavioral arrest.
At Emory, about 75% of patients evaluated for epilepsy surgery undergo stereotactic electroencephalography (SEEG) monitoring. This invasive procedure requires making a number of small holes in the skull to insert depth electrodes that provide a detailed map of the seizure focus.
However, since this patient’s anatomical findings, seizure semiology and non-invasive video SEEG all pointed to medialtemporal sclerosis, the team believed stereo-EEG was not needed.
Additional tests in the evaluation phase included:
- An interictal 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) scan, indicating hypometabolism in the left medialtemporal lobe, another confirmation of the seizure onset location.
- Neurocognitive testing to further pinpoint the seizure onset zone and establish baseline cognitive function. Testing revealed decreased verbal memory abilities, implicating seizure activity in his dominant hemisphere.
- Functional MRI scans, which confirmed the patient’s left-hemisphere dominance.
When all results were available, the epilepsy team met to discuss the case and made a unified recommendation of laser ablation surgery.
Dr. Gross performed the surgery in Emory’s interventional MRI suite using stereotactic guidance to target and treat the seizure focus. The suite, which offers state-of-the-art technology not available elsewhere in the region, enhances laser ablation accuracy and safety.
- The integrated software platform calculates drill entry coordinates and defines the trajectory to the ablation site, ensuring submillimeter precision.
- The surgeon affixes a 10” x10” fiducial grid to the skull, which can provide further guidance for drilling when integrated with MRI technology.
- After making the burr hole, the surgeon guides the laser catheter through the opening to the ablation site. The software helps the surgeon make pitch and roll adjustments to ensure accuracy.
- During the thermal ablation, the MRI scanner takes an image every three seconds to calculate the time-and-temperature curve and provide a damage zone estimate. Safety checkpoints prevent unwanted tissue damage.
- The surgeon uses an MRI sequence MRI with contrast to confirm that the epileptogenic tissue has been completely ablated. If it hasn’t, the surgeon can retarget it with a second trajectory.
Recovery and Follow-Up
The patient recovered as expected from the more than 9-hour surgery. He experienced the not-uncommon side effect of double vision that lasted three months and has since resolved.
During his six-month follow-up appointment with Dr. Gross, the patient expressed deep appreciation for the care he received at Emory. He has had no seizures since the surgery and reports that his life is back on track.
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