Incomplete hippocampal inversion in patients with mutations in genes involved in sonic hedgehog signaling.

Sonic hedgehog (Shh) signaling pathways are known to play an important role in the morphological development of the hippocampus in vivo, but their actual roles in humans have not been clarified. Hypothalamic hamartoma (HH) is known to be associated with germline or somatic gene mutations of Shh signaling. We hypothesized that patients with HH and mutations of Shh-related genes also show hippocampal maldevelopment and an abnormal hippocampal infolding angle (HIA). We analyzed 45 patients (age: 1-37 years) with HH who underwent stereotactic radiofrequency thermocoagulation and found Shh-related gene mutations in 20 patients. In addition, 44 pediatric patients without HH (age: 2-25 years) who underwent magnetic resonance imaging (MRI) examinations under the same conditions during the same period were included in this study as a control group. HIA evaluated on MRI was compared between patients with gene mutations and the control group. The median HIA at the cerebral peduncle slice in patients with the gene mutation was 74.36° on the left and 76.11° on the right, and these values were significantly smaller than the corresponding values in the control group (80.46° and 80.56°, respectively, p < 0.01). Thus, mutations of Shh-related genes were correlated to incomplete hippocampal inversion. The HIA, particularly at the cerebral peduncle slice, is a potential indicator of abnormalities of the Shh-signaling pathway.

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.

Long-term seizure outcomes in patients with hypothalamic hamartoma treated by stereotactic radiofrequency thermocoagulation.

OBJECTIVE: To investigate long-term seizure outcomes in patients with hypothalamic hamartoma (HH) following stereotactic radiofrequency thermocoagulation (SRT). METHODS: A total of 131 patients with HH who underwent SRT and were followed for at least three years after the last SRT were enrolled. Seizure outcomes were evaluated for gelastic seizures (GS) and other types of seizures (nGS) separately using the International League Against Epilepsy classification. Classes 1 and 2 were considered seizure-free. Kaplan-Meier survival analyses were used to estimate the proportion remaining seizure-free after the first and last SRTs. Risk factors relating to outcomes were analyzed by log-rank tests and a multivariate Cox proportional hazards model. RESULTS: Reoperation was performed in 34 patients (26.2%). Median total follow-up was 61 (range, 36-202) months. Seizure freedom was obtained in 116 patients (88.6%) for GS and 85 of 108 patients (78.7%) for nGS at the last follow-up. Mean GS-free survival times improved from after the first (64.1 [95%CI 57.3-70.9] months) to after the last SRT (80.2 [95%CI 75.7-84.8] months). About 90% of GS recurrences after the first SRT were found within 6 months, though a few patients recurred more than 2 years after the first SRT. On the other hand, mean nGS-free survival times after the first and last SRTs were not different between after the first SRT (84.4 [95%CI 73.0-90.7] months) and after the last SRT (83.1 [95%CI 74.1-92.0] months). There was no factor related to GS outcomes, but the significant factor for nGS-free survival after the last SRT was multiple previous treatments (p=0.01, hazard ratio=15.65, 95%CI 1.79-137.16). SIGNIFICANCE: The last SRT was almost equivalent to achieving complete disconnection of HHs from the hypothalamus according to our strategy. Considering the epileptogenic network, GS outcomes depend on complete disconnection, whereas nGS outcomes are not affected by surgical factors but independency of secondary epileptogenesis.

Location of emotional corticobulbar tract in the internal capsule.

Emotional facial paresis (EFP) is a rare neurological symptom with intact volitional facial movement. The exact location of emotional corticobulbar tract remains unclear. EFP was frequently recognized following the surgery of stereotactic radiofrequency thermocoagulation for hypothalamic hamartoma in 84.5% of 58 patients. To examine our hypothesis that EFP might be caused by stereotactic trajectories passing through an area including the internal capsule (IC), topographical locations of trajectories were analyzed and compared between the EFP-positive group (n = 41) and the EFP-negative group (n = 8). In the EFP-positive group, multiple (2 to 5) trajectories focused within the genu of the IC in 31 (75.6%) cases, whereas a single trajectory passed through the genu in 8 (19.5%) cases. In the EFP-negative group, 6 (75.0%) of 8 patients had a single trajectory and only one patient had two trajectories passing through the genu of the IC. The ratio between multiple trajectories and a single trajectory relevant to the genu differed significantly between two groups (p < 0.01). The multiple trajectories focusing in the genu have high risks of EFP, whereas a single trajectory seemed to incidentally cause EFP. The results proved our hypothesis and provided a high probability that the emotional corticobulbar tract passes through the genu rather than anterior or posterior limbs of the IC. The location of the emotional corticobulbar tract is in the genu of the IC.

Proteomic profile differentiating between mesial temporal lobe epilepsy with and without hippocampal sclerosis.

Hippocampal sclerosis (HS) is the most common neuropathological condition in adults with drug-resistant epilepsy and represents a critical feature in mesial temporal lobe epilepsy (MTLE) syndrome. Although epileptogenic brain tissue is associated with glutamate excitotoxicity leading to oxidative stress, the proteins that are targets of oxidative damage remain to be determined. In the present study we designed comprehensive analyses of changes in protein expression level and protein oxidation status in the hippocampus or neocortex to highlight proteins associated with excitotoxicity by comparing MTLE patients with relatively mild excitotoxicity (MTLE patients without HS, MTLE-non-HS) and those with severe excitotoxicity (MTLE patients with HS, MTLE-HS). We performed 2-dimensional fluorescence difference gel electrophoresis, 2D-oxyblot analysis, and mass spectrometric amino acid sequencing. We identified 16 proteins at 18 spots in which the protein expression levels differed between sclerotic and non-sclerotic hippocampi. In the sclerotic hippocampus, the expression levels of several synaptic proteins were decreased, and those of some glia-associated proteins increased. We confirmed histologically that all MTLE-HS cases examined exhibited severe neuronal cell loss and remarkable astrocytic gliosis in the hippocampi. In all MTLE-non-HS cases examined, neurons were spared and gliosis was unremarkable. Therefore, we consider that decreased synaptic proteins are a manifestation of loss of neuronal cell bodies and dendrites, whereas increased glia-associated proteins are a manifestation of proliferation and hypertrophy of astrocytes. These are considered to be the result of hippocampal sclerosis. In contrast, the expression level of d-3-phosphoglycerate dehydrogenase (PHGDH), an l-serine synthetic enzyme expressed exclusively by astrocytes, was decreased, and that of stathmin 1, a neurite extension-related protein expressed by neurons, was increased in the sclerotic hippocampus. These findings cannot be explained solely as the result of hippocampal sclerosis. Rather, these changes can be involved in the continuation of seizure disorders in MTLE-HS. In addition, the protein carbonylation detection, an indicator of protein oxidation caused by excitotoxicity of multiple seizures and/or status epilepticus, revealed that the carbonyl level of collapsin response mediator protein 2 (CRMP2) increased significantly in the sclerotic hippocampus. In conclusion, protein identification following profiling of protein expression levels and detection of oxidative proteins indicated potential pathognomonic protein changes. The decreased expression of PHGDH, increased expression of stathmin 1, and carbonylation of CRMP2 differentiate between MTLE with and without HS. Therefore, further investigations of PHGDH, stathmin 1 and CRMP2 are promising to study more detailed effects of excitotoxicity on epileptogenic hippocampal tissue.

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

OBJECTIVE: Ablation surgery has become the first line of treatment for hypothalamic hamartomas (HHs). For effective treatment, optimum targeting of ablation is mandatory. The present study aimed to evaluate the correspondence between the electrophysiological features of HHs and morphological targeting by semimicrorecording during stereotactic radiofrequency thermocoagulation (SRT). METHODS: Eighty HH patients who underwent SRT were involved. Semimicrorecording was performed on the first trajectory. The distance from the center of the target at the morphological border (TMB) determined by magnetic resonance imaging, differences in discharge patterns, and area potentials (APs) were measured. RESULTS: The electrophysiological border (EB) between the HH and hypothalamus was detected by semimicrorecording in 73 (91.3%), AP increase (API) in the HH was detected in 31 (38.8%), and spike discharges (SDs) of the HH were detected in 56 patients (70.0%). Semimicrorecording showed significantly different APs among structures passing through the trajectory, except between API and SDs. The median distances from the center of the TMB to the EB, API, SDs, and AP decline were -3.50, -2.49, -1.38, and +2.00 mm, respectively. SIGNIFICANCE: The electrophysiological features of HHs were shown by semimicrorecording during SRT. The EB corresponded to the morphological border. The electrophysiologically active area of HHs was located near the border. Ablation surgery should focus on disconnection at the border between the HH and the hypothalamus to maximize its effectiveness, as well as to reduce complications.

Repeat stereotactic radiofrequency thermocoagulation in patients with hypothalamic hamartoma and seizure recurrence.

OBJECTIVE: To evaluate the feasibility of repeat stereotactic radiofrequency thermocoagulation (re-SRT) for patients with hypothalamic hamartoma (HH) and to clarify clinical and surgical factors for seizure outcomes. METHODS: Hypothalamic hamartoma patients with gelastic seizures (GSs) who underwent SRT were retrospectively reviewed. Seizure outcomes were evaluated separately for GS and other types of seizures (non-GS). Surgical complications were compared between re-SRT and first SRT. Clinical and surgical factors related to both seizure recurrences after first SRT and final seizure outcomes were analyzed. RESULTS: Participants comprised 150 patients (92 males; median age at surgery, 8 years; range, 1.7-50 years). Of those, 122 (81.3%) had non-GS. Forty-three patients (28.7%) underwent re-SRT. Freedom from GS was achieved by first SRT in 103 patients (68.7%), second SRT in 30/40 (67.5%), third SRT in 3/10 (30.0%), and fourth SRT in 2/3 (66.7%). Finally, 135 patients (90.0%) became GS-free. Ninety patients (73.8%) achieved non-GS freedom, with first SRT in all except one case. Transient complications were more frequent with first SRT (118/150, 78.7%) than re-SRT (35/56, 62.5%), whereas persistent complications were more frequent with re-SRT (7/56, 12.5%) than with first SRT (3/150, 2.0%). Multivariate analyses revealed only younger age at surgery (≤1 year) as related to GS recurrence after first SRT, with no variables affecting final GS outcomes. Meanwhile, seizure type (tonic seizure), intellectual disability, and genetic syndromes were significant factors for both non-GS recurrence and final outcomes. Multiple previous treatments were significantly related to final non-GS outcomes as well. Size and subtype of HH and surgical factors were unrelated to seizure outcomes. SIGNIFICANCE: Repeat stereotactic radiofrequency thermocoagulation provides potential opportunities to achieve freedom from recurrent GS, albeit with increased risks of persistent complications. Non-GS and intellectual disability could offer early surgical indications, and repeated ineffective treatments should be avoided.

Surgical strategy for focal cortical dysplasia based on the analysis of the spike onset and peak zones on magnetoencephalography.

OBJECTIVE: The aim of this study was to elucidate the surgical strategy for focal cortical dysplasia (FCD) based on the interictal analysis on magnetoencephalography (MEG). For this purpose, the correlation between the spike onset zone (Sp-OZ) and the spike peak zone (Sp-PZ) on MEG was evaluated to clarify the differences in the Sp-OZ and its correlation with Sp-PZ in FCD subtypes to develop an appropriate surgical strategy. METHODS: Forty-one FCD patients (n = 17 type I, n = 13 type IIa, and n = 11 type IIb) were included. The Sp-OZ was identified by the summation of gradient magnetic-field topography (GMFT) magnitudes at interictal MEG spike onset, and Sp-PZ was defined as the distribution of the equivalent current dipole (ECD) at spike peak. Correlations between Sp-OZ and Sp-PZ distributions were evaluated and compared with clinical factors and seizure outcomes retrospectively. RESULTS: Good seizure outcomes (Engel class I) were obtained significantly more often in patients with FCD type IIb (10/11, 90.9%) than those with type IIa (4/13, 30.8%; p = 0.003) and type I (6/17, 35.3%; p = 0.004). The Sp-OZ was significantly smaller (1 or 2 gyri) in type IIb (10, 90.9%) than in type IIa (4, 30.8%; p = 0.003) or type I (9, 53.0%; p = 0.036). Concordant correlations between the Sp-OZ and Sp-PZ were significantly more frequent in type IIb (7, 63.6%) than in type IIa (1, 7.7%; p = 0.015) or type I (1, 5.8%; p = 0.004). Complete resection of the Sp-OZ achieved significantly better seizure outcomes (Engel class I: 9/10, 90%) than incomplete resection (11/31, 35.5%) (p = 0.003). In contrast, complete resection of the Sp-PZ showed no significant difference in good seizure outcomes (9/13, 69.2%) compared with incomplete resection (11/28, 39.3%). CONCLUSIONS: The Sp-OZ detected by MEG using GMFT and its correlation with Sp-PZ were related to FCD subtypes. A discordant distribution between Sp-OZ and Sp-PZ in type I and IIa FCD indicated an extensive epileptogenic zone and a complex epileptic network. Type IIb showed a restricted epileptogenic zone with the smaller Sp-OZ and concordance between Sp-OZ and Sp-PZ. Complete resection of the Sp-OZ provided significantly better seizure outcomes than incomplete resection. Complete resection of the Sp-PZ was not related to seizure outcomes. There was a definite difference in the epileptogenic zone among FCD subtypes; hence, an individual surgical strategy taking into account the correlation between the Sp-OZ and Sp-PZ should be considered.

Pathogenic variants of DYNC2H1, KIAA0556, and PTPN11 associated with hypothalamic hamartoma.

OBJECTIVE: Intensive genetic analysis was performed to reveal comprehensive molecular insights into hypothalamic hamartoma (HH). METHODS: Thirty-eight individuals with HH were investigated by whole exome sequencing, target capture-based deep sequencing, or single nucleotide polymorphism (SNP) array using DNA extracted from blood leukocytes or HH samples. RESULTS: We identified a germline variant of KIAA0556, which encodes a ciliary protein, and 2 somatic variants of PTPN11, which forms part of the RAS/mitogen-activated protein kinase (MAPK) pathway, as well as variants in known genes associated with HH. An SNP array identified (among 3 patients) one germline copy-neutral loss of heterozygosity (cnLOH) at 6p22.3-p21.31 and 2 somatic cnLOH; one at 11q12.2-q25 that included DYNC2H1, which encodes a ciliary motor protein, and the other at 17p13.3-p11.2. A germline heterozygous variant and an identical somatic variant of DYNC2H1 arising from cnLOH at 11q12.2-q25 were confirmed in one patient (whose HH tissue, therefore, contains biallelic variants of DYNC2H1). Furthermore, a combination of a germline and a somatic DYNC2H1 variant was detected in another patient. CONCLUSIONS: Overall, our cohort identified germline/somatic alterations in 34% (13/38) of patients with HH. Disruption of the Shh signaling pathway associated with cilia or the RAS/MAPK pathway may lead to the development of HH.

Asymmetric gelastic seizure as a lateralizing sign in patients with hypothalamic hamartoma.

Gelastic seizure (GS) is a cardinal symptom of hypothalamic hamartoma (HH), which is intractable but surgically remediable. Although facial asymmetry with GS has not been extensively discussed, asymmetric GS has been frequently recognized in our large series. We hypothesized that asymmetric GS represents a lateralizing sign caused by the epileptic propagation from the attachment of the HH. To examine this hypothesis, the positive predictive value (PPV) and diagnostic odds ratio (DOR) of asymmetric GS were validated to predict the side of HH attachment. In 103 cases registered to the present analysis, asymmetric GS was recognized in 71 patients and symmetric GS in 32. Asymmetric GS with a lopsided grimace was exclusively observed on the side contralateral to unilateral HH in 39 patients and to the dominant attachment of 23 HHs with bilateral attachment (true positive, n = 62). In contrast, asymmetric GS was exhibited independently on both sides in 4 patients with bilaterally attached HH and on the side ipsilateral to the dominant attachment in the other 4. Symmetric HH attachments were identified in 1 patient (false negative, n = 9). Asymmetric GS was a reliable lateralizing sign with high DOR (6.08) and PPV (78%) to predict the side of epileptic propagation. Furthermore, the present study demonstrated the probability of seizure propagation from bilateral attachment, and this evidence provides a new rationale to the surgical strategy of bilateral disconnection for HH with bilateral attachment.

Variability and Reliability of Paired-Pulse Depression and Cortical Oscillation Induced by Median Nerve Stimulation.

Paired-pulse depression (PPD) has been widely used to investigate the functional profiles of somatosensory cortical inhibition. However, PPD induced by somatosensory stimulation is variable, and the reasons for between- and within-subject PPD variability remains unclear. Therefore, the purpose of this study was to clarify the factors influencing PPD variability induced by somatosensory stimulation. The study participants were 19 healthy volunteers. First, we investigated the relationship between the PPD ratio of each component (N20m, P35m, and P60m) of the somatosensory magnetic field, and the alpha, beta, and gamma band changes in power [event-related desynchronization (ERD) and event-related synchronization (ERS)] induced by median nerve stimulation. Second, because brain-derived neurotrophic factor (BDNF) gene polymorphisms reportedly influence the PPD ratio, we assessed whether BDNF genotype influences PPD ratio variability. Finally, we evaluated the test-retest reliability of PPD and the alpha, beta, and gamma ERD/ERS induced by somatosensory stimulation. Significant positive correlations were observed between the P60m_PPD ratio and beta power change, and the P60m_PPD ratio was significantly smaller for the beta ERD group than for the beta ERS group. P35m_PPD was found to be robust and highly reproducible; however, P60m_PPD reproducibility was poor. In addition, the ICC values for alpha, beta, and gamma ERD/ERS were 0.680, 0.760, and 0.552 respectively. These results suggest that the variability of PPD for the P60m deflection may be influenced by the ERD/ERS magnitude, which is induced by median nerve stimulation.

Outcome of vagus nerve stimulation for drug-resistant epilepsy: the first three years of a prospective Japanese registry.

Vagus nerve stimulation (VNS) is an established option of adjunctive treatment for patients with drug-resistant epilepsy, however, evidence for long-term efficacy is still limited. Studies on clinical outcomes of VNS in Asia are also limited. We report the overall outcome of a national, prospective registry that included all patients implanted in Japan. The registry included patients of all ages with all seizure types who underwent VNS implantation for drug-resistant epilepsy in the first three years after approval of VNS in 2010. The registry excluded patients who were expected to benefit from resective surgery. Efficacy analysis was assessed based on the change in frequency of all seizure types and the rate of responders. Changes in cognitive, behavioural and social status, quality of life (QOL), antiepileptic drug (AED) use, and overall AED burden were analysed as other efficacy indices. A total of 385 patients were initially registered. Efficacy analyses included data from 362 patients. Age range at the time of VNS implantation was 12 months to 72 years; 21.5% of patients were under 12 years of age and 49.7% had prior epilepsy surgery. Follow-up rate was >90%, even at 36 months. Seizure control improved over time with median seizure reduction of 25.0%, 40.9%, 53.3%, 60.0%, and 66.2%, and responder rates of 38.9%, 46.8%, 55.8%, 57.7%, and 58.8% at three, six, 12, 24, and 36 months of VNS therapy, respectively. There were no substantial changes in other indices throughout the three years of the study, except for self/family-accessed QOL which improved over time. No new safety issues were identified. Although this was not a controlled comparative study, this prospective national registry of Japanese patients with drug-resistant epilepsy, with >90% follow-up rate, indicates long-term efficacy of VNS therapy which increased over time, over a period of up to three years. The limits of such trials, in terms of AED modifications and during follow-up and difficulties in seizure counting are also discussed.

Predictors of cognitive function in patients with hypothalamic hamartoma following stereotactic radiofrequency thermocoagulation surgery.

OBJECTIVE: To determine the predictors of cognitive function in patients with drug-resistant gelastic seizures (GS) related to hypothalamic hamartoma (HH) before and after stereotactic radiofrequency thermocoagulation surgery (SRT). METHODS: We studied 88 patients with HH who underwent SRT between October 1997 and December 2014. Patients received neuropsychological tests preoperatively and postoperatively. Based on the preoperative measures, patients were categorized as "high-functioning" (full-scale intelligence quotient [FSIQ] ≥70; n = 48) and "low-functioning" group (FSIQ <70; n = 40). Univariate and multivariate linear regression analyses determined the clinical, electroencephalography (EEG), and imaging factors associated with preoperative cognitive function as well as postoperative cognitive change. RESULTS: Eighty-seven patients (98.8%) were followed postoperatively for an average of 3.3 years, and 75 (85.2%) of them achieved GS remission at the last hospital visit. Neuropsychological performance was significantly improved after surgery in both groups. Multivariate linear regression analysis showed that a smaller HH size (p = 0.002) and a smaller number of antiepileptic drugs (p < 0.001) were preoperatively associated with better neuropsychological performance. Multivariate linear regression analysis showed that better postoperative improvement in cognition was associated with a shorter duration of epilepsy (p = 0.03). SIGNIFICANCE: Cognitive impairment related to epileptic encephalopathy may improve following SRT in substantial proportions of HH patients. Reduced improvement in postoperative cognitive function in patients with longer duration of epilepsy warrants further studies to determine if earlier SRT provides a greater chance of postoperative cognitive improvement in patients with HH.

Analysis of ictal magnetoencephalography using gradient magnetic-field topography (GMFT) in patients with neocortical epilepsy.

OBJECTIVE: We aimed to validate the usefulness of gradient magnetic-field topography (GMFT) for analysis of ictal magnetoencephalography (MEG) in patients with neocortical epilepsy. METHODS: We identified 13 patients presenting with an ictal event during preoperative MEG. We applied equivalent current dipole (ECD) estimation and GMFT to detect and localize the ictal MEG onset, and compared these methods with the ictal onset zone (IOZ) derived from chronic intracranial electroencephalography. The surgical resection areas and outcomes were also evaluated. RESULTS: GMFT detected and localized the ictal MEG onset in all patients, whereas ECD estimation showed localized ECDs in only 2. The delineation of GMFT was concordant with the IOZ at the gyral-unit level in 10 of 12 patients (83.3%). The detectability and precision of delineation of ictal MEG activity by GMFT were significantly superior to those of ECD (p<0.05 and p<0.01, respectively). Complete resection of the IOZ in the concordant group provided seizure freedom in 3 patients, whereas seizures remained in 9 patients who had incomplete resections. CONCLUSIONS: Because of its higher spatial resolution, GMFT of ictal MEG is superior to conventional ECD estimation in patients with neocortical epilepsy. SIGNIFICANCE: Ictal MEG study is a useful tool to estimate the seizure onset in patients with neocortical epilepsy.

Ca2+ -permeable AMPA receptors associated with epileptogenesis of hypothalamic hamartoma.

Hypothalamic hamartoma (HH), composed of neurons and glia without apparent cytologic abnormalities, is a rare developmental malformation in humans. Patients with HH often have characteristic medically refractory gelastic seizures, and intrinsic epileptogenesis within the lesions has been speculated. Herein we provide evidence to suggest that in HH neurons, Ca2+ permeability through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors is aberrantly elevated. In needle biopsy specimens of HH tissue, field potential recordings demonstrated spontaneous epileptiform activities similar to those observed in other etiologically distinct epileptogenic tissues. In HH, however, these activities were clearly abolished by application of Joro Spider Toxin (JSTX), a specific inhibitor of the Ca2+ -permeable AMPA receptor. Consistent with these physiologic findings, the neuronal nuclei showed disappearance of adenosine deaminase acting on RNA 2 (ADAR2) immunoreactivity. Furthermore, examination of glutamate receptor 2 (GluA2) messenger RNA (mRNA) revealed that editing efficiency at the glutamine/arginine site was significantly low. These results suggest that neurons in HH may bear Ca2+ -permeable AMPA receptors due to dislocation of ADAR2.

Spatiotemporal Accuracy of Gradient Magnetic-Field Topography (GMFT) Confirmed by Simultaneous Magnetoencephalography and Intracranial Electroencephalography Recordings in Patients with Intractable Epilepsy.

Gradient magnetic-field topography (GMFT) is one method for analyzing magnetoencephalography (MEG) and representing the spatiotemporal dynamics of activity on the brain surface. In contrast to spatial filters, GMFT does not include a process reconstructing sources by mixing sensor signals with adequate weighting. Consequently, noisy sensors have localized and limited effects on the results, and GMFT can handle MEG recordings with low signal-to-noise ratio. This property is derived from the principle of the planar-type gradiometer, which obtains maximum gradient magnetic-field signals just above the electrical current source. We assumed that this characteristic allows GMFT to represent even faint changes in brain activities that cannot be achieved with conventional equivalent current dipole analysis or spatial filters. GMFT is thus hypothesized to represent brain surface activities from onset to propagation of epileptic discharges. This study aimed to validate the spatiotemporal accuracy of GMFT by analyzing epileptic activities using simultaneous MEG and intracranial electroencephalography (iEEG) recordings. Participants in this study comprised 12 patients with intractable epilepsy. Epileptic spikes simultaneously detected on both MEG and iEEG were analyzed by GMFT and voltage topography (VT), respectively. Discrepancies in spatial distribution between GMFT and VT were evaluated for each epileptic spike. On the lateral cortices, areas of GMFT activity onset were almost concordant with VT activities arising at the gyral unit level (concordance rate, 66.7-100%). Median time lag between GMFT and VT at onset in each patient was 11.0-42.0 ms. On the temporal base, VT represented basal activities, whereas GMFT failed but instead represented propagated activities of the lateral temporal cortices. Activities limited to within the basal temporal or deep brain region were not reflected on GMFT. In conclusion, GMFT appears to accurately represent brain activities of the lateral cortices at the gyral unit level. The slight time lag between GMFT and VT is likely attributable to differences in the detection principles underlying MEG and iEEG. GMFT has great potential for investigating the spatiotemporal dynamics of lateral brain surface activities.

Effect of muscle contraction strength on gating of somatosensory magnetic fields.

Afferent somatosensory information is modulated before the afferent input arrives at the primary somatosensory cortex during voluntary movement. The aim of the present study was to clarify the effect of muscular contraction strength on somatosensory evoked fields (SEFs) during voluntary movement. In addition, we examined the differences in gating between innervated and non-innervated muscle during contraction. We investigated the changes in gating effect by muscular contraction strength and innervated and non-innervated muscles in human using 306-channel magnetoencephalography. SEFs were recorded following the right median nerve stimulation in a resting condition and during isometric muscular contractions from 10 % electromyographic activity (EMG), 20 and 30 % EMG of the right extensor indicis muscle and abductor pollicis brevis muscle. Our results showed that the equivalent current dipole (ECD) strength for P35m decreased with increasing strength of muscular contraction of the right abductor pollicis brevis muscle. However, changes were observed only at 30 % EMG contraction level of the right extensor indicis muscle, which was not innervated by the median nerve. There were no significant changes in the peak latencies and ECD locations of each component in all conditions. The ECD strength did not differ significantly for N20m and P60m regardless of the strength of muscular contraction and innervation. Therefore, we suggest that the gating of SEF waveforms following peripheral nerve stimulation was affected by the strength of muscular contraction and innervation of the contracting muscle.

Inhibitory effect of intensity and interstimulus interval of conditioning stimuli on somatosensory evoked magnetic fields.

Magnetoencephalography (MEG) recordings were performed to investigate the inhibitory effects of conditioning stimuli with various types of interstimulus intervals (ISIs) or intensities on somatosensory evoked magnetic fields (SEFs) using a 306-ch whole-head MEG system. Twenty-three healthy volunteers participated in this study. Electrical stimuli were applied to the right median nerve at the wrist. Six pulse trains with ISIs of 500 ms were presented in Experiment 1. A paired-pulse paradigm with three kinds of conditioning stimulus (CON) intensities, 500 ms before the test stimulus (TS), was applied in Experiment 2. Finally, three CONs 500 or 1000 ms before TS were presented in Experiment 3. Three main SEF deflections (N20m, P35m, and P60m) were observed, and the source activities of P35m and P60m significantly decreased after the 2nd pulse of a six pulse trains. These source activities also significantly decreased with increasing intensity of CON. In addition, these attenuations of source activities were affected by CON-CON or CON-TS intervals. These results indicated that the source activities were modulated by the intensity and ISIs of CONs. Furthermore, P35m after the stimulation were very sensitive to CONs; however, the attenuation of P60m after the stimulation lasted for a longer period than that of P35m. Our findings suggest that the conditioning stimulation had inhibitory effects on subsequent evoked cortical responses for more than 500 ms. Our results also provide important clues about the nature of short-latency somatosensory responses in human studies.

Epileptic network of hypothalamic hamartoma: An EEG-fMRI study.

OBJECTIVE: To investigate the brain networks involved in epileptogenesis/encephalopathy associated with hypothalamic hamartoma (HH) by EEG with functional MRI (EEG-fMRI), and evaluate its efficacy in locating the HH interface in comparison with subtraction ictal SPECT coregistered to MRI (SISCOM). METHODS: Eight HH patients underwent EEG-fMRI. All had gelastic seizures (GS) and 7 developed other seizure types. Using a general linear model, spike-related activation/deactivation was analyzed individually by applying a hemodynamic response function before, at, and after spike onset (time-shift model=-8-+4s). Group analysis was also performed. The sensitivity of EEG-fMRI in identifying the HH interface was compared with SISCOM in HH patients having unilateral hypothalamic attachment. RESULTS: EEG-fMRI revealed activation and/or deactivation in subcortical structures and neocortices in all patients. 6/8 patients showed activation in or around the hypothalamus with the HH interface with time-shift model before spike onset. Group analysis showed common activation in the ipsilateral hypothalamus, brainstem tegmentum, and contralateral cerebellum. Deactivation occurred in the default mode network (DMN) and bilateral hippocampi. Among 5 patients with unilateral hypothalamic attachment, activation in or around the ipsilateral hypothalamus was seen in 3 using EEG-fMRI, whereas hyperperfusion was seen in 1 by SISCOM. SIGNIFICANCE: Group analysis of this preliminary study may suggest that the commonly activated subcortical network is related to generation of GS and that frequent spikes lead to deactivation of the DMN and hippocampi, and eventually to a form of epileptic encephalopathy. Inter-individual variance in neocortex activation explains various seizure types among patients. EEG-fMRI enhances sensitivity in detecting the HH interface compared with SISCOM.

Somatic mutations in GLI3 and OFD1 involved in sonic hedgehog signaling cause hypothalamic hamartoma.

OBJECTIVE: Hypothalamic hamartoma (HH) is a congenital anomalous brain tumor. Although most HHs are found without any other systemic features, HH is observed in syndromic disorders such as Pallister-Hall syndrome (PHS) and oral-facial-digital syndrome (OFD). Here, we explore the possible involvement of somatic mutations in HH. METHODS: We analyzed paired blood and hamartoma samples from 18 individuals, including three with digital anomalies, by whole-exome sequencing. Detected somatic mutations were validated by Sanger sequencing and deep sequencing of target amplicons. The effect of GLI3 mutations on its transcriptional properties was evaluated by luciferase assays using reporters containing eight copies of the GLI-binding site and a mutated control sequence disrupting GLI binding. RESULTS: We found hamartoma-specific somatic truncation mutations in GLI3 and OFD1, known regulators of sonic hedgehog (Shh) signaling, in two and three individuals, respectively. Deep sequencing of amplicons covering the mutations showed mutant allele rates of 7-54%. Somatic mutations in OFD1 at Xp22 were found only in male individuals. Potential pathogenic somatic mutations in UBR5 and ZNF263 were also identified in each individual. Germline nonsense mutations in GLI3 and OFD1 were identified in each individual with PHS and OFD type I in our series, respectively. The truncated GLI3 showed stronger repressor activity than the wild-type protein. We did not detect somatic mutations in the remaining 9 individuals. INTERPRETATION: Our data indicate that a spectrum of human disorders can be caused by lesion-specific somatic mutations, and suggest that impaired Shh signaling is one of the pathomechanisms of HH.