Electrophysiological properties and seizure networks in hypothalamic hamartoma

Advances in epileptic network findings of hypothalamic hamartomas

Hypothalamic hamartomas (HHs) are congenital developmental malformations located in the hypothalamus. They are associated with a characteristic clinical manifestation known as gelastic seizures (GS). However, the traditional understanding of HHs has been limited, resulting in insufficient treatment options and high recurrence rates of seizures after surgery. This is consistent with the network hypothesis of focal epilepsy that the epileptogenic zone is not only limited to HH but may also involve the distant cerebral cortex external to the HH mass. The epilepsy network theory, on the other hand, provides a new perspective. In this study, we aim to explore HH-related epilepsy as a network disease, challenging the conventional notion of being a focal lesional disease. We analyze various aspects of HHs, including genes and signaling pathways, local circuits, the whole-brain level, phenotypical expression in terms of seizure semiology, and comorbidities. By examining HHs through the lens of network theory, we can enhance our understanding of the condition and potentially identify novel approaches for more effective management and treatment of epilepsy associated with HHs.

Kindling in humans: Does secondary epileptogenesis occur?

The relevance of secondary epileptogenesis for human epilepsy remains a controversial subject decades after it was first described in animal models. Whether or not a previously normal brain region can become independently epileptogenic through a kindling-like process has not, and cannot, be definitely proven in humans. Rather than reliance on direct experimental evidence, attempts to answering this question must depend on observational data. In this review, observations based largely upon contemporary surgical series will advance the case for secondary epileptogenesis in humans. As will be argued, hypothalamic hamartoma-related epilepsy provides the strongest case for this process; all the stages of secondary epileptogenesis can be observed. Hippocampal sclerosis (HS) is another pathology where the question of secondary epileptogenesis frequently arises, and observations from bitemporal and dual pathology series are explored. The verdict here is far more difficult to reach, in large part because of the scarcity of longitudinal cohorts; moreover, recent experimental data have challenged the claim that HS is acquired consequent to recurrent seizures. Synaptic plasticity more than seizure-induced neuronal injury is the likely mechanism of secondary epileptogenesis. Postoperative running-down phenomenon provides the best evidence that a kindling-like process occurs in some patients, evidenced by its reversal. Finally, a network perspective of secondary epileptogenesis is considered, as well as the possible role for subcortical surgical interventions.

Advances in hypothalamic hamartoma research over the past 30 years (1992-2021): a bibliometric analysis

Background

Hypothalamic hamartoma (HH) is a rare intracranial disease whose manifestations include gelastic seizures and precocious puberty. The diagnosis and treatment of HH have changed substantially over the past three decades as medical care has improved. Bibliometrics can reveal the evolution and development of a scientific field.

Methods

Documents on HH were retrieved from the Web of Science Core Collection (WoSCC) database on September 8, 2022. The search terms were as follows: "hypothalamic hamartoma" or "hamartoma of the hypothalamus" or "hypothalamic hamartomas." The types of documents were restricted to articles, case reports, and reviews. VOSviewer, CiteSpace, and the R package "bibliometrix" were used for a bibliometric analysis.

Results

A total of 667 independent documents on HH were obtained from the WoSCC database. The most common types of documents were articles (n = 498, 75%) and reviews (n = 103, 15%). The number of annual publications fluctuated but showed an upward trend overall, and the annual growth rate was 6.85%. The cumulative publication data indicated that the most influential journals in the HH field include Epilepsia, Epileptic Disorders, Child's Nervous System, Neurosurgery, and the Journal of Neurosurgery. Kerrigan JF, Ng YT, Rekate HL, Regis J, and Kameyama S were among the most prominent authors in the field of HH, with numerous publications and citations. American research institutions, especially the Barrow Neurological Institute, occupied a pivotal position in HH research. Other countries and institutions were catching up and producing considerable research results. Research on HH has steadily switched its emphasis from Pallister-Hall syndrome (PHS) and precocious puberty to epilepsy and new diagnostic and therapeutic techniques, including Gamma Knife, laser ablation, and interstitial thermal therapy.

Conclusion

HH remains a special neurological disease with significant research prospects. The development of novel technologies, including MRI-guided laser-induced thermal therapy (MRg-LiTT) and stereotactic radiofrequency thermocoagulation (RF-TC), has enabled the efficient treatment of gelastic seizures in HH while minimizing the risks associated with craniotomies. Through bibliometric analysis, this study points out the direction for future HH research.

A clinical evaluation of gelastic and dacrystic seizures: a multicenter study

BACKGROUND

Gelastic seizures are extremely rare, short-lasting, unprovoked, and uncontrollable laughing attacks. We conducted this retrospective evaluation to determine whether these symptoms, manifesting in different forms, such as cheerful laughter, laughing, smiling, and sobbing had any value in terms of etiology or localization.

METHODS

A total of 31 patients who exhibited bouts of laughing or crying and who were under follow-up between 2000 and 2019 at tertiary epilepsy centers were included in the study. Laughing seizures were divided into three groups in terms of semiology (i.e., laughter with mirth, laughter without mirth, and smile). Dacrystic seizures were accompanied by some gelastic seizures and were divided into two groups in terms of semiology (i.e., weeping loudly [motor and voice-sobbing] and crying).

RESULTS

Of the 27 patients with laughing seizures, 12 had seizures that manifested with smiling, 7 had seizures that manifested with laughing and mirth, and 8 had seizures that manifested with laughter without mirth. Dacrystic-gelastic seizures were observed in four patients, among whom 2 patients had crying and laughter without mirth and 2 patients had weeping loudly and laughter without mirth episodes.

CONCLUSION

Gelastic and dacrystic seizures often suggest hypothalamic hamartomas, in the literature. This rare ictal behavior can originate from different cortical locations and lesions of a different nature. However, we found that gelastic seizures with smiling were a more homogenous group with regard to location in the temporal lobe, which we aimed to show by evaluating the patients included in this study.

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.

Hypothalamic hamartoma associated with polymicrogyria and periventricular nodular heterotopia in children: report of three cases and discussion of the origin of the seizures

PURPOSE

Hypothalamic hamartomas (HH) are malformations responsible for drug-resistant epilepsy. HH are usually isolated or part of a genetic syndrome, such as Pallister-Hall. Exceptionally they can be associated with other brain malformations such as polymicrogyria (PMG) and periventricular nodular heterotopia (PNH). We discuss the origin of the seizures associated with this combination of malformations, through electrophysiological studies, and review the literature on this rarely reported syndrome.

METHODS

We retrospectively reviewed the patients with HH who had surgery between 1998 and 2020 and selected those with associated focal PMG and PNH, detected on MRIs. All patients had comprehensive clinical evaluation and surface video-EEG and one underwent stereoelectroencephalography (SEEG).

RESULTS

Three male patients out of 182 were identified with a mean age at surgery of 7.5 years. MRI showed unilateral focal PMG (fronto-insulo-parietal, fronto-insulo-parieto-opercular, and fronto-insular, respectively) and multiple PNH homolateral to the main HH implantation side. In two patients, there were strong clinical and scalp EEG arguments for seizure onset within the HH. In the third, due to abnormalities on scalp video-EEG in the same area as PMG and the lack of gelastic seizures, SEEG was indicated and demonstrated seizure onset within the hamartoma. With a mean follow-up of 6 years, two patients were seizure-free.

CONCLUSION

Our results show that HH is the trigger of epilepsy, which confirms the high epileptogenic potential of this malformation. In patients such as ours, as in those with isolated HH, we recommend to begin by operating the HH independently of seizure semiology or electrophysiological abnormalities.

18F-FDG-PET glucose hypometabolism pattern in patients with epileptogenic hypothalamic hamartoma

Epileptogenic hypothalamic hamartoma is characterized by intractable gelastic seizures. A systematic analysis of the overall brain metabolic pattern in patients with hypothalamic hamartoma (HH) could facilitate the understanding of the epileptic brain network and the associated brain damage effects of HH. In this study, we retrospectively evaluated 27 patients with epileptogenic HH (8 female patients; age, 2-33 years) by using ¹⁸F-fluorodeoxyglucose-positron emission tomography. The correlations among tomography result, seizure type, sex, and structural magnetic resonance imaging were assessed. Whole metabolic patterns and voxel-based morphometry findings were assessed by group analysis with healthy controls. Assessment of the whole metabolic pattern in patients with HH revealed several regional metabolic reductions in the cerebrum and an overall metabolic reduction in the cerebellum. In addition, areas showing hypometabolism in the neocortex were more widely distributed ipsilaterally than contralaterally to the HH. Reductions in glucose metabolism and gray matter volume in the neocortex were predominant ipsilateral to the HH. In conclusion, the glucose hypometabolism pattern in patients with epileptogenic HH involved the neocortex, subcortical regions, and cerebellum. The characteristics of glucose hypometabolism differed across seizure type and sex. Reductions in glucose metabolism and structural changes may be based on different mechanisms, but both are likely to occur ipsilateral to the HH in the neocortex. We hypothesized that the dentato-rubro-thalamic tract and cerebro-ponto-cerebellar tract, which are responsible for intercommunication between the cerebral cortex, subcortical regions, and cerebellar regions, may be involved in a pathway related to seizure propagation, particularly gelastic seizures, in patients with HH.

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.

Analysis of signal components < 500 Hz in brain organoids coupled to microelectrode arrays: A reliable test-bed for preclinical seizure liability assessment of drugs and screening of antiepileptic drugs

Brain organoids with three-dimensional structure and tissue-like function are highly demanded for brain disease research and drug evaluation. However, to our knowledge, methods for measuring and analyzing brain organoid function have not been developed yet. This study focused on the frequency components of an obtained waveform below 500 Hz using planner microelectrode array (MEA) and evaluated the response to the convulsants pentylenetetrazol (PTZ) and strychnine as well as the antiepileptic drugs (AEDs) perampanel and phenytoin. Sudden and persistent seizure-like firing was observed with PTZ administration, displaying a concentration-dependent periodic activity with the frequency component enhanced even in one oscillation characteristic. On the other hand, in the administration of AEDs, the frequency of oscillation decreased in a concentration-dependent manner and the intensity of the frequency component in one oscillation also decreased. Interestingly, at low doses of phenytoin, a group of synchronized bursts was formed, which was different from the response to the perampanel. Frequency components contained information on cerebral organoid function, and MEA was proven useful in predicting the seizure liability of drugs and evaluating the effect of AEDs with a different mechanism of action. In addition, frequency component analysis of brain organoids using MEA is an important analysis method to perform in vitro to in vivo extrapolation in the future, which will help explore the function of the organoid itself, study human brain developments, and treat various brain diseases.

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Frequency analysis <500 Hz was performed in brain organoids coupled to planner microelectrode arrays (MEA).

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Concentration-dependent changes in frequency components were detected in responses to convulsants and antiepileptic drugs (AEDs).

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Analysis of signal components <500 Hz in brain organoids is a useful method for preclinical seizure liability assessment of drugs and screening of antiepileptic drugs.