Seizure onset patterns predict outcome after stereo-electroencephalography-guided laser amygdalohippocampotomy.

OBJECTIVE: Stereotactic laser amygdalohippocampotomy (SLAH) is an appealing option for patients with temporal lobe epilepsy, who often require intracranial monitoring to confirm mesial temporal seizure onset. However, given limited spatial sampling, it is possible that stereotactic electroencephalography (stereo-EEG) may miss seizure onset elsewhere. We hypothesized that stereo-EEG seizure onset patterns (SOPs) may differentiate between primary onset and secondary spread and predict postoperative seizure control. In this study, we characterized the 2-year outcomes of patients who underwent single-fiber SLAH after stereo-EEG and evaluated whether stereo-EEG SOPs predict postoperative seizure freedom. METHODS: This retrospective five-center study included patients with or without mesial temporal sclerosis (MTS) who underwent stereo-EEG followed by single-fiber SLAH between August 2014 and January 2022. Patients with causative hippocampal lesions apart from MTS or for whom the SLAH was considered palliative were excluded. An SOP catalogue was developed based on literature review. The dominant pattern for each patient was used for survival analysis. The primary outcome was 2-year Engel I classification or recurrent seizures before then, stratified by SOP category. RESULTS: Fifty-eight patients were included, with a mean follow-up duration of 39 ± 12 months after SLAH. Overall 1-, 2-, and 3-year Engel I seizure freedom probability was 54%, 36%, and 33%, respectively. Patients with SOPs, including low-voltage fast activity or low-frequency repetitive spiking, had a 46% 2-year seizure freedom probability, compared to 0% for patients with alpha or theta frequency repetitive spiking or theta or delta frequency rhythmic slowing (log-rank test, p = .00015). SIGNIFICANCE: Patients who underwent SLAH after stereo-EEG had a low probability of seizure freedom at 2 years, but SOPs successfully predicted seizure recurrence in a subset of patients. This study provides proof of concept that SOPs distinguish between hippocampal seizure onset and spread and supports using SOPs to improve selection of SLAH candidates.

Stereotactic laser ablation for hypothalamic and deep intraventricular lesions.

OBJECTIVE Laser ablation is a novel, minimally invasive procedure that utilizes MRI-guided thermal energy to treat epileptogenic and other brain lesions. In addition to treatment of mesial temporal lobe epilepsy, laser ablation is increasingly being used to target deep or inoperable lesions, including hypothalamic hamartoma (HH), subependymal giant cell astrocytoma (SEGA), and exophytic intrinsic hypothalamic/third ventricular tumors. The authors reviewed their early institutional experience with these patients to characterize clinical outcomes in patients undergoing this procedure. METHODS A retrospective cohort (n = 12) of patients undergoing laser ablation at a single institution was identified, and clinical and radiographic records were reviewed. RESULTS Laser ablation was successfully performed in all patients. No permanent neurological or endocrine complications occurred; 2 (17%) patients developed acute obstructive hydrocephalus or shunt malfunction following treatment. Laser ablation of HH resulted in seizure freedom (Engel Class I) in 67%, with the remaining patients having a clinically significant reduction in seizure frequency of greater than 90% compared with preoperative baseline (Engel Class IIB). Treatment of SEGAs resulted in durable clinical and radiographic tumor control in 2 of 3 cases, with one patient receiving adjuvant everolimus and the other receiving no additional therapy. Palliative ablation of hypothalamic/third ventricular tumors resulted in partial tumor control in 1 of 3 patients. CONCLUSIONS Early experience suggests that laser ablation is a generally safe, durable, and effective treatment for patients harboring HHs. It also appears effective for local control of SEGAs, especially in combination therapy with everolimus. Its use as a palliative treatment for intrinsic hypothalamic/deep intraventricular tumors was less successful and associated with a higher risk of serious complications. Additional experience and long-term follow-up will be beneficial in further characterizing the effectiveness and risk profile of laser ablation in treating these lesions in comparison with conventional resective surgery or stereotactic radiosurgery.

Impact of intracranial subclinical seizures on seizure outcomes after SLAH in patients with mesial temporal lobe epilepsy.

OBJECTIVE: To investigate the association between subclinical seizures detected on intracranial electroencephalographic (i-SCSs)recordings and mesial temporal sclerosis (MTS), as well as their impact on surgical outcomes of stereotactic laser amygdalohippocampotomy (SLAH). METHODS: A retrospective review was conducted on 27 patients with drug-resistant mesial temporal lobe epilepsy (MTLE) who underwent SLAH. The number of seizures detected on scalp EEG and iEEG was assessed. Patients were followed for a minimum of 3 years after SLAH. RESULTS: Of the 1715 seizures recorded from mesial temporal regions, 1640 were identified as i-SCSs. Patients with MTS were associated with favorable short- and long-term surgical outcomes. Patients with MTS had a higher number of i-SCSs compared to patients without MTS. The numbers of i-SCSs were higher in patients with Engel I-II outcomes, but no significant statistical difference was found. However, it was observed that patients with MTS who achieved Engel I-II classification had higher numbers of i-SCSs than patients without MTS (P < 0.05). CONCLUSION: Patients with MTS exhibited favorable short-term and long-term surgical outcome after SLAH. A higher number of i-SCSs was significantly associated with MTS in patients with MTLE. The number of i-SCSs tended to be higher in patients with Engel Ⅰ-Ⅱ surgical outcomes. SIGNIFICANCE: The association between i-SCSs, MTS, and surgical outcomes in MTLE patients undergoing SLAH has significant implications for understanding the underlying mechanisms and identifying potential therapeutic targets to enhance surgical outcomes.

Withdrawal of antiepileptic drugs after stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy.

OBJECTIVE: This retrospective study investigated the success rate of withdrawal of antiepileptic drugs (AEDs) following stereotactic laser amygdalohippocampotomy (SLAH) for mesial temporal lobe epilepsy (MTLE), and identified predictors of seizure recurrence. MATERIALS AND METHODS: We retrospectively assessed 65 patients who underwent SLAH for MTLE (59 lesional). Patients' demographics, disease characteristics and post-surgical outcomes were evaluated for their potential to predict seizure recurrence associated with withdrawal of AEDs. RESULTS: The mean period of observation post SLAH was 51 months (range 12-96 months) and the mean period to initial reduction of AEDs was 21 months (range 12-60 months). Reduction of AEDs was attempted in 37 patients (57 %) who were seizure free post SLAH and it was successful in approximately 2/3 of them. From the remainder 1/3 who relapsed, nearly all regained seizure control after reinstitution of their AEDs. The likelihood of relapse after reduction of AEDs was predicted only by pre-operative seizure frequency. At the end of the observation period, approximately 14 % of all SLAH patients were seizure free without AEDs and approximately 54 % remained seizure free on AEDs. Compared with preoperative status, the number of AEDs were reduced in 37 % of patients, unchanged in 51 % of them and increased in 12 % of them. CONCLUSIONS: Successful SLAH for MTLE allows for reduction of AEDs in a significant portion of patients and complete withdrawal of AEDs in a subset of them. Patients with higher pre-operative seizure frequency exhibit a greater chance of relapse post reduction of AEDs.

A neurosurgeon`s view: Laser interstitial thermal therapy of mesial temporal lobe structures.

Stereotactic laser ablation of mesial temporal structures is a promising new surgical intervention for patients with mesial temporal lobe epilepsy (MTLE). Since this procedure was first used to treat MTLE in 2010, the literature contains reports of 37 patients that underwent MR-guided stereotactic laser amygdalohippocampotomy (SLAH) using Laser Interstitial Thermal Therapy (LITT) with at least 1year of follow-up. This early body of data suggests that SLAH is a safe and effective treatment for MTLE in properly selected patients. Moreover, SLAH is substantially less invasive when compared with open surgical procedures including standard anterior temporal lobectomy and its more selective variants, results in immediate destruction of tissue in contrast to radiosurgical treatments for MTLE, and can more readily ablate larger volumes of tissue than is possible with techniques employing radiofrequency ablation. Finally, evidence is accruing that SLAH is associated with lower overall risk of neuropsychological deficits compared to open surgery. Thus, LITT constitutes a novel minimally invasive tool in the neurosurgeon's armamentarium for managing medically refractory seizures that may draw eligible patients to consider surgical interventions to manage their seizures.

A novel mesial temporal stereotactic coordinate system.

OBJECTIVE Stereotactic laser ablation and neurostimulator placement represent an evolution in staged surgical intervention for epilepsy. As this practice evolves, optimal targeting will require standardized outcome measures that compare electrode lead or laser source with postprocedural changes in seizure frequency. The authors propose and present a novel stereotactic coordinate system based on mesial temporal anatomical landmarks to facilitate the planning and delineation of outcomes based on extent of ablation or region of stimulation within mesial temporal structures. METHODS The body of the hippocampus contains a natural axis, approximated by the interface of cornu ammonis area 4 and the dentate gyrus. The uncal recess of the lateral ventricle acts as a landmark to characterize the anterior-posterior extent of this axis. Several volumetric rotations are quantified for alignment with the mesial temporal coordinate system. First, the brain volume is rotated to align with standard anterior commissure-posterior commissure (AC-PC) space. Then, it is rotated through the axial and sagittal angles that the hippocampal axis makes with the AC-PC line. RESULTS Using this coordinate system, customized MATLAB software was developed to allow for intuitive standardization of targeting and interpretation. The angle between the AC-PC line and the hippocampal axis was found to be approximately 20°-30° when viewed sagittally and approximately 5°-10° when viewed axially. Implanted electrodes can then be identified from CT in this space, and laser tip position and burn geometry can be calculated based on the intraoperative and postoperative MRI. CONCLUSIONS With the advent of stereotactic surgery for mesial temporal targets, a mesial temporal stereotactic system is introduced that may facilitate operative planning, improve surgical outcomes, and standardize outcome assessment.