MR-guided stereotactic laser ablation of epileptogenic foci in children☆
Highlights
► MR-guided stereotactic laser ablation of seizure foci is minimally invasive. ► MRgLITT is particularly advantageous in deep-seated epileptogenic pathologies. ► The benefits are better morbidity rate, real-time visualization, and ablation control. ► It could be an alternative to conventional surgery for intractable pediatric epilepsy.
Introduction
Approximately one-third of epilepsy patients have seizures that are refractory to pharmaceutical therapy. Epilepsy surgery can potentially remove or destroy the primary epileptogenic focus. In patients with well-defined focal cortical lesions and correlated electrophysiological features, 75–80% undergoing open resection of the seizure focus can obtain effective seizure control [1]. Persistence of seizures has been found to be significantly correlated with the preoperative duration of epilepsy, nonlesional resective procedures, and incompleteness of lesional resections [2]. Stereotactic procedures for minimally invasive treatment of epilepsy may ablate seizure foci with less damage to normal surrounding tissue than resective surgery. Vladyka reported on stereotactic radiofrequency thermal ablation techniques in 1978 [3], and later, Parrent and Blume demonstrated the technique's potential [4]. Recently, Liscak et al. reported on a series of 51 mesial temporal lobe epilepsy (MTLE) patients who received thermal ablation of the amygdala hippocampus complex (AHC), which resulted in 78% of subjects reaching Engel Class I outcome [5].
Despite these studies, ablative therapies for localized seizure foci are not routine due to: 1) imprecise radiofrequency energy source, 2) lack of real-time feedback on the tissue coagulation, 3) mismatch between the volume of the epileptogenic target and RF ablative volume requiring multiple probe passes, and 4) potential for complications due to damage of critical surrounding structures.
Recently, the U.S. Food and Drug Administration (FDA) cleared the first MRI-guided laser interstitial thermal therapy (MRgLITT) system for ablation in neurosurgery, allowing for real-time thermal monitoring of the ablation process and feedback control over the laser energy delivery. We report Class IV evidence and short-term follow-up results from the first five cases of minimally invasive MRgLITT-based ablation of seizure foci.
Section snippets
Classification of evidence
This is a retrospective study providing Class IV evidence that MRgLITT can safely and effectively reduce seizures in pediatric epilepsy patients whose seizures failed to significantly improve from medical management with at least 2 antiepileptic drugs (AEDs).
Standard protocol approvals, registrations, and patient consents
Under IRB approval from Baylor College of Medicine in Houston, five patients were enrolled in a pilot study at Texas Children's Hospital to evaluate MRgLITT of focal lesions in patients with medically refractory epilepsy. Written informed
MRgLITT results
Applicator placement and thermal imaging were successfully accomplished in all cases. Fig. 2A shows pre-therapy T2 MRI of Patient 1 with a single applicator placed centrally in the lesion targeted for ablation. In Patient 1, thermal imaging was performed during a single 133-second ablation cycle, which included 43 s of low-power test doses and 90 s of an ablative laser dose. Fig. 2B shows representative thermal maps and damage estimates generated in Patient 1 during laser therapy. While images
Discussion
Although epilepsy surgery is associated with a high success rate in well-selected patients, more than 20 years have elapsed, on average, before patients are referred to an epilepsy center for surgical evaluation [9]. Furthermore, only a small fraction of the estimated number of eligible patients receives operations each year [10], indicating that surgery may be underutilized in epilepsy management. There is evidence that the success rate of additional pharmaceutical interventions drops to 3% or
Conclusions
While follow-up is limited, the results from the first five patients treated with stereotactic laser ablation for epilepsy have been encouraging. This report contains Class IV evidence of the safety and efficacy of MRgLITT treatment of focal intractable epilepsy in children. All subjects are without complication from their ablation procedure and remain seizure free at 2 to 13 months post procedure. Based on these early results we believe that there is significant potential for MRgLITT to offer a
Ethics and consent
All human studies have been approved by the appropriate ethics committee and have been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. Patients' parental guardians gave their informed consent prior to their inclusion in this study.
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Disclosure: Drs. Gowda and McNichols are employed by Visualase, Inc., which produces the technology used in this paper and have received grant support from the Epilepsy Research Foundation.