Significance of the electrophysiological border between hypothalamic hamartomas and the hypothalamus for the target of ablation surgery identified by intraoperative semimicrorecording

Intraoperative changes in large-scale thalamic circuitry following laser ablation of hypothalamic hamartomas

BACKGROUND AND OBJECTIVES

Gelastic seizures due to hypothalamic hamartomas (HH) are challenging to treat, in part due to an incomplete understanding of seizure propagation pathways. Although magnetic resonance imaging-guided laser interstitial thermal therapy (MRgLITT) is a promising intervention to disconnect HH from ictal propagation networks, the optimal site of ablation to achieve seizure freedom is not known. In this study, we investigated intraoperative post-ablation changes in resting-state functional connectivity to identify large-scale networks associated with successful disconnection of HH.

METHODS

Children who underwent MRgLITT for HH at two institutions were consecutively recruited and followed for a minimum of one year. Seizure freedom was defined as Engel score of 1A at the last available follow-up. Immediate pre- and post- ablation resting-state functional MRI scans were acquired while maintaining a constant depth of general anesthetic. Multivariable generalized linear models were used to identify intraoperative changes in large-scale connectivity associated with seizure outcomes.

RESULTS

Twelve patients underwent MRgLITT for HH, five of whom were seizure-free at their last follow-up. Intraprocedural changes in thalamocortical circuitry involving the anterior cingulate cortex were associated with seizure-freedom. Children who were seizure-free demonstrated an increase and decrease in connectivity to the pregenual and dorsal anterior cingulate cortices, respectively. In addition, children who became seizure-free demonstrated increased thalamic connectivity to the periaqueductal gray immediately following MRgLITT.

DISCUSSION

Successful disconnection of HH is associated with intraoperative, large-scale changes in thalamocortical connectivity. These changes provide novel insights into the large-scale basis of gelastic seizures and may represent intraoperative biomarkers of treatment success.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Hypothalamic Hamartoma: Surgical Approach and Treatment Outcomes

Hypothalamic hamartoma (HH) is a rare lesion consisting of normal neurons and neuroglia arranged in an abnormal pattern which usually causes gelastic seizures (GS). Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has been developed as a minimally invasive approach to treat HH and gradually become a first-line treatment. In total, this study enrolled 47 consecutive HH patients that underwent one round of ablation. Patients were followed for at least one year. Patients' medical records and surgical information were carefully reviewed, and univariate analyses were performed. Of the treated patients, 72.3% remained GS-free in this study, with an overall Engel class I rate of 68.1%. Long-term postoperative complications occurred in six patients. Factors associated with GS prognosis included Delalande classification (p = 0.033), HH volume (p = 0.01), and the ablation rate of the HH body (p = 0.035). The disconnection rate was 0.73 ± 0.14 in the Engel class Ia group as compared to 0.62 ± 0.13 in the Engel Ib-Engel IV group (p = 0.046). MRgLITT represents a safe and effective surgical procedure. Patients with larger or Delalande type IV HH may require multiple rounds of ablation. In addition to assessing the degree of disconnection, ablation volume should also be carefully considered for patients undergoing this procedure.

Minimally invasive procedures for hypothalamic hamartoma–related epilepsy: a systematic review and meta-analysis

OBJECTIVE

Hypothalamic hamartoma (HH) is a rare, nonmalignant, heterotopic developmental malformation that consists of a mixture of normal neurons and glial cells. Resection of HHs has been associated with high rates of mortality and morbidity. Therefore, minimally invasive ablation methods could be the best treatment option for HH. The most frequently used minimally invasive options for HH ablation are radiofrequency thermocoagulation (RFT), laser ablation (LA), and stereotactic radiosurgery.

METHODS

To investigate three minimally invasive procedures in the treatment of refractory seizures related to HH, the authors conducted a systematic search in March 2022 in the MEDLINE, Embase, Scopus, and Web of Science databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Seizure freedom was the primary outcome of interest. The authors defined seizure freedom as Engel class I or International League Against Epilepsy class 1 or 2 or as the reported term “seizure freedom.” The secondary outcome was long-term complications reported in studies. Both random- and fixed-effects models were used to calculate the pooled proportion of seizure freedom and complication rate with 95% confidence intervals. A modified version of the Joanna Briggs Institute (JBI) Critical Appraisal to assess the risk of bias was used.

RESULTS

The authors included 15 studies with 422 patients (RFT, n = 190; LA, n = 171; and Gamma Knife Radiosurgery [GKRS], n = 61). Generally, the mean incidences of overall seizure freedom after minimally invasive procedures were 77% (95% CI 0.74–0.81) and 68% (95% CI 0.57–0.79) using fixed- and random-effects models, respectively. The mean incidence of overall seizure freedom after RFT was 69% (95% CI 0.63–0.75), and the mean incidences of overall seizure freedom after LA and GKRS were 87% (95% CI 0.82–0.92) and 44% (95% CI 0.32–0.57), respectively. The total complication rate with minimally invasive procedures was 13% (95% CI 0.01–0.26). The complication rate in each treatment was as follows: 5% (95% CI 0.0–0.12) for RFT, 20% (95% CI 0.0–0.47) for LA, and 22% (95% CI 0–0.65) for GKRS. Meta-regression analysis showed an association between older age and higher complication rates in the LA group.

CONCLUSIONS

In this meta-analysis, LA showed superiority in seizure freedom over the other two methods. The complication rate associated with RFT was less than those in the other two methods; however, this difference was not statistically significant.

A Special Approach for Stereotactic Radiofrequency Thermocoagulation of Hypothalamic Hamartomas With Bilateral Attachments to the Hypothalamus: The Transthird Ventricular Approach to the Contralateral Attachment

BACKGROUND

Disconnection surgery for the treatment of epileptic hypothalamic hamartomas (HHs) is strategically difficult in cases with complex-shaped HHs, especially with bilateral hypothalamic attachments, despite its effectiveness.

OBJECTIVE

To evaluate the feasibility of a new approach for stereotactic radiofrequency thermocoagulation (SRT) using penetration of the third ventricle (SRT-TT) aiming to disconnect bilateral hypothalamic attachments in a single-staged, unilateral procedure.

METHODS

Ninety patients (median age at surgery, 5.0 years) who had HHs with bilateral hypothalamic attachments and were followed for at least 1 year after their last SRT were retrospectively reviewed.

RESULTS

Thirty-three patients underwent SRT-TT as initial surgery. Of the 58 patients after mid-2013 when SRT-TT was introduced, 33 underwent SRT-TT and 12 (20.7%) required reoperation (ReSRT), whereas 20 of 57 patients (35.1%) without SRT-TT underwent reoperation. Reoperation was required in significantly fewer patients after mid-2013 (n = 12 of 58, 20.7%) than before mid-2013 (n = 15 of 32, 46.9%) (P = .01). Final seizure freedoms were not different between before and after mid-2013 (gelastic seizure freedom, n = 30 [93.8%] vs n = 49 [84.5%] and other types of seizure freedom, n = 21 of 31 [67.7%] vs n = 32 of 38 [84.2%]). Persistent complications were less in SRT-TT than in ReSRT using the bilateral approach, but not significantly. However, hormonal replacement was required significantly more often in ReSRT using the bilateral approach (4 of 9, 44.4%) than in SRT-TT (3 of 32, 9.4%) (P = .01).

CONCLUSION

SRT-TT enabled disconnection of bilateral attachments of HHs in a single-staged procedure, which reduced the additional invasiveness of reoperation. Moreover, SRT-TT reduced damage to the contralateral hypothalamus, with fewer endocrinological complications than the bilateral approach.

Hypothalamic Hamartomas: Evolving Understanding and Management

Hypothalamic hamartomas (HH) are rare, basilar developmental lesions with widespread comorbidities often associated with refractory epilepsy and encephalopathy. Imaging advances allow for early, even prenatal, detection. Genetic studies suggest mutations in GLI3 and other patterning genes are involved in HH pathogenesis. About 50%-80% of children with HH have severe rage and aggression and a majority of patients exhibit externalizing disorders. Behavioral disruption and intellectual disability may predate epilepsy. Neuropsychological, sleep, and endocrine disorders are typical. The purpose of this article is to provide a summary of the current understanding of HH and to highlight opportunities for future research.