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Laser Surgery – Changing Management and Outcomes of Hypothalamic Hamartomas/Update on Laser Surgery for Pediatric Epilepsy

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Angus A. Wilfong, MD

Hypothalamic hamartomas (HHs) are rare, congenital nonneoplastic lesions associated with early life-onset gelastic seizures with mirthless laughter that are refractory to medical therapy. Open or endoscopic surgical resection of HHs have been the traditional definitive treatment for gelastic epilepsy, but because lesions are deep in the brain and close to critically eloquent structures, surgery remains precarious, with variable success and high morbidity. Patients undergoing traditional surgery are at high risk of developing life-long disabilities that include neuroendocrine dysfunction, visual impairment, memory deficits and paralysis. Stereotactic radiosurgery using Gamma Knife is an alternative, noninvasive treatment, but radiation effects require months to show benefits. Thus, its use is limited in pediatric patients. More recently, MRI-guided laser interstitial thermal therapy (LITT) has emerged as a promising minimally invasive treatment for HH with much improved safety and better efficacy. The technology combines the instant effect of thermal ablation with stereotactic precision and guidance using real-time magnetic resonance thermography.

The first patient in the world who received LITT for epilepsy was under the care of this author, and the procedure was performed in August 2010.  The patient was 6 years old and had tuberous sclerosis complex (TSC) with seizures arising from a left frontal lobe cortical tuber. The tuber was safely destroyed with laser ablation, and the patient has remained seizure-free ever since. Subsequently, 29 additional children with various types of medically refractory focal epilepsy were offered this minimally invasive approach as part of a prospective clinical trial. Patients underwent stereotactic frame-based placement of an MR-compatible laser catheter (1.6 mm diameter) through a 3.2 mm twist drill hole. A laser surgery system (Visualase, Inc.) cleared by the U.S. Food and Drug Administration was utilized to ablate the epileptogenic focus, using real-time MR thermometry.

LITT is now offered in nearly all epilepsy centers across the United States and has recently entered Europe. Patients are considered candidates for this procedure if their epileptogenic focus or lesion is relatively small. Three-dimensional stereotactic surgical targeting is used to plan the laser trajectory from scalp to target using MRI sequences. Vascular imaging allows for safe passage of the laser catheter avoiding blood vessels along the way. Once planning is complete, the patient is anesthetized and, using either a stereotactic frame or a robot, the laser catheter(s) is placed (Figure 1). Depending upon the size and shape of the target, 1–4 lasers can be used in a single case. The patient is then placed into the MRI scanner and, using real-time thermal imaging, the laser is activated at low power to ensure targeting was precise. The power of the laser is then increased, and the ablation is monitored in real time until the target is destroyed. The laser is typically on for 1–4 minutes depending upon size of the target and power used. The drop off from complete tissue destruction to complete tissue preservation is approximately 1 mm. This allows for ablations to be performed safely in the immediate vicinity of critical brain structures (Figure 2). Following the procedure, the laser is removed, and a single suture is placed (Figure 3). Most patients go home the following morning.

Figure 1: Laser catheter placed into brain with 3D navigation to target.

Figure 2: Laser catheter placed into hypothalamic hamartoma with orange circle showing complete ablation.

Given the precision and safety of laser ablation, this was offered to an 8-year-old with medically refractory gelastic epilepsy associated with a hypothalamic hamartoma. In July 2012, he became the first HH patient to receive LITT. He became seizure-free with no complications, has been weaned off all antiseizure medication and is now living independently and attending university. A follow-up study of 14 HH children treated with LITT showed that 12 (86%) were seizure-free with mean follow-up of 12 months. There were no permanent surgical complications, neurologic deficits or neuroendocrine disturbances. One patient had a minor subarachnoid hemorrhage that was asymptomatic.

Figure 3: Immediately after the laser catheter is removed, a single suture is placed.

The clinical features associated with HH include gelastic seizures and a progressive epileptic encephalopathy characterized by the onset of additional seizure subtypes leading to cognitive regression. Targeted resection, destruction of the HH or disconnection of its attachments to the hypothalamus, is the mainstay of therapy. Open surgical approaches with or without endoscopic assistance achieve seizure freedom in about 50% of cases, depending on the approach and HH anatomy. Complications from open surgery for HH vary, but overall morbidity is high, with most patients experiencing at least transient neurological or cognitive deficits. For 26 patients that underwent a transcallosal approach, 15 (58%) had transient memory disturbances, with persistent impairment in 2 (8%) and permanent endocrine disturbances in 2 (8%). Other reported operative complications with craniotomies and endoscopic procedures for HH have included postoperative hemiplegia, visual field deficits, persistent diabetes insipidus and symptomatic thalamic infarcts.

LITT has become the accepted standard of care therapy for HH and for many other types of focal epilepsy, particularly with relatively small lesions. At Phoenix Children’s, approximately 50% of brain surgeries for epilepsy utilize LITT. The first case was performed here in early 2017, and now 148 cases have been completed. There have been no ablation-related complications. Overall seizure freedom is 64% with a minimum of 12-months’ follow-up. An advantage of LITT is that repeat ablations can easily be performed as a staged procedure if seizures persist or if new targets arise.


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