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.

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.

Stereotactic radiofrequency thermocoagulation for giant hypothalamic hamartoma

OBJECTIVE

The authors undertook this study to validate the feasibility and safety of stereotactic radiofrequency thermocoagulation (SRT) for the surgical treatment of giant hypothalamic hamartoma (HH).

METHODS

Of the 109 patients who underwent SRT for hypothalamic hamartoma (HH) at the authors' institution between 1997 and 2013, 16 patients (9 female, 7 male) had giant HHs (maximum diameter ≥ 30 mm). The clinical records of these 16 patients were retrospectively reviewed.

RESULTS

The patients' age at first SRT ranged from 1 to 22 years (median 5 years). The maximum diameter of their HHs was 30–80 mm (mean 38.5 mm). Eleven HHs had bilateral attachments to the hypothalamus. All patients had gelastic seizures (GS), and 12 had types of seizures other than GS. Some of these patients also had mental retardation (n = 10, 62.5%), behavioral disorders (n = 8, 50.0%), and precocious puberty (n = 11, 68.8%). A total of 22 SRT procedures were performed; 5 patients underwent repeat SRT procedures. There was no mortality or permanent morbidity. After 17 of the 22 procedures, the patients experienced transient complications, including high fever (n = 7), hyperphagia (n = 3), hyponatremia (n = 6), disturbance of consciousness (n = 1), cyst enlargement (n = 1), and epidural hematoma (n = 1). Thirteen patients (81.3%) achieved freedom from GS after the final SRT procedure during a follow-up period ranging from 6 to 60 months (mean 23 months). Twelve patients had nongelastic seizures in addition to GS, and 7 (58.3%) of these 12 patients experienced freedom from their nongelastic seizures.

CONCLUSIONS

SRT provided minimal invasiveness and excellent seizure outcomes even in patients with giant HHs. Repeat SRT is safe for residual GS. SRT is a feasible single surgical strategy for HH regardless of the tumor's size or shape.

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.

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.

Surgical versus medical treatment for children with epileptic encephalopathy in infancy and early childhood: Results of an international multicenter cohort study in Far-East Asia (the FACE study)

OBJECTIVE

To compare the seizure and developmental outcomes in infants and young children with epileptic encephalopathy who have undergone surgical and medical treatments.

METHODS

An international, multicenter, observational cohort study was undertaken. A total of 317 children aged <6 years, who had frequent disabling seizures despite intensive medical treatments, were registered. Among the enrolled children, 250 were treated medically (medical group), 31 underwent resective surgery (resective group), and 36 underwent palliative surgery [callosotomy (n=30) or vagal nerve stimulation (n=6); palliative group] on admission. Seizure and developmental outcomes were obtained for 230 children during the 3-year follow-up period. Cox proportional hazard model was used to adjust for clinical backgrounds among treatment groups when comparing the seizure-free survival rates.

RESULTS

At the 3-year follow-up, seizure-free survival was 15.7%, 32.1%, and 52.4% in the medical, palliative, and resective groups, respectively. The adjusted hazard ratios for seizure recurrence in the resective and palliative groups versus the medical group were 0.43 (95% CI, 0.21-0.87, P=0.019) and 0.82 (95% CI, 0.46-1.46, P=0.50), respectively; the former was statistically significant. Regarding the developmental outcome, the mean DQs in the resective group increased significantly compared to those in the medical group during the follow-up (P<0.01). As for subgroup analysis, better seizure and development outcomes were demonstrated in the resective group compared to the medical group in children with nonsyndromic epilepsies (those to which no known epilepsy syndromes were applicable).

SIGNIFICANCE

These results suggest that surgical treatments, particularly resective surgeries, are associated with better seizure and developmental outcomes compared with successive medical treatment. The present observations may facilitate the identification of infants and young children with epileptic encephalopathy who could benefit from surgery.

MRI-guided stereotactic radiofrequency thermocoagulation for 100 hypothalamic hamartomas

OBJECT

The aim of this study was to elucidate the invasiveness, effectiveness, and feasibility of MRI-guided stereotactic radiofrequency thermocoagulation (SRT) for hypothalamic hamartoma (HH).

METHODS

The authors examined the clinical records of 100 consecutive patients (66 male and 34 female) with intractable gelastic seizures (GS) caused by HH, who underwent SRT as a sole surgical treatment between 1997 and 2013.

The median duration of follow-up was 3 years (range 1–17 years). Seventy cases involved pediatric patients. Ninety percent of patients also had other types of seizures (non-GS). The maximum diameter of the HHs ranged from 5 to 80 mm (median 15 mm), and 15 of the tumors were giant HHs with a diameter of 30 mm or more. Comorbidities included precocious puberty (33.0%), behavioral disorder (49.0%), and mental retardation (50.0%).

RESULTS

A total of 140 SRT procedures were performed. There was no adaptive restriction for the giant or the subtype of HH, regardless of any prior history of surgical treatment or comorbidities. Patients in this case series exhibited delayed precocious puberty (9.0%), pituitary dysfunction (2.0%), and weight gain (7.0%), besides the transient hypothalamic symptoms after SRT. Freedom from GS was achieved in 86.0% of patients, freedom from other types of seizures in 78.9%, and freedom from all seizures in 71.0%. Repeat surgeries were not effective for non-GS. Seizure freedom led to disappearance of behavioral disorders and to intellectual improvement.

CONCLUSIONS

The present SRT procedure is a minimally invasive and highly effective surgical procedure without adaptive limitations. SRT involves only a single surgical procedure appropriate for all forms of epileptogenic HH and should be considered in patients with an early history of GS.

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.

Somatic Mutations in the MTOR gene cause focal cortical dysplasia type IIb

OBJECTIVE

Focal cortical dysplasia (FCD) type IIb is a cortical malformation characterized by cortical architectural abnormalities, dysmorphic neurons, and balloon cells. It has been suggested that FCDs are caused by somatic mutations in cells in the developing brain. Here, we explore the possible involvement of somatic mutations in FCD type IIb.

METHODS

We collected a total of 24 blood-brain paired samples with FCD, including 13 individuals with FCD type IIb, 5 with type IIa, and 6 with type I. We performed whole-exome sequencing using paired samples from 9 of the FCD type IIb subjects. Somatic MTOR mutations were identified and further investigated using all 24 paired samples by deep sequencing of the entire gene's coding region. Somatic MTOR mutations were confirmed by droplet digital polymerase chain reaction. The effect of MTOR mutations on mammalian target of rapamycin (mTOR) kinase signaling was evaluated by immunohistochemistry and Western blotting analyses of brain samples and by in vitro transfection experiments.

RESULTS

We identified four lesion-specific somatic MTOR mutations in 6 of 13 (46%) individuals with FCD type IIb showing mutant allele rates of 1.11% to 9.31%. Functional analyses showed that phosphorylation of ribosomal protein S6 in FCD type IIb brain tissues with MTOR mutations was clearly elevated, compared to control samples. Transfection of any of the four MTOR mutants into HEK293T cells led to elevated phosphorylation of 4EBP, the direct target of mTOR kinase.

INTERPRETATION

We found low-prevalence somatic mutations in MTOR in FCD type IIb, indicating that activating somatic mutations in MTOR cause FCD type IIb.

Characteristic expression of p57/Kip2 in balloon cells in focal cortical dysplasia

Balloon cells are a pathognomonic cellular feature of various cortical malformations, including focal cortical dysplasia type IIb (FCD IIb), cortical tubers of tuberous sclerosis (TSC) and hemimegalencephaly (HME). In the present study, we investigated the immunohistochemical expression of p57/Kip2, a member of the Cip/Kip family of cyclin-dependent kinase inhibitory proteins, in balloon cells in surgical specimens taken from 26, 17 and six patients with FCD IIb, TSC and HME, respectively. Characteristic dot-like reactivity with a faint, intense, reticular and process-like pattern was confined to the proximal portion of the cytoplasmic processes of the cells. Immunoelectron microscopy revealed the p57/Kip2 reactivity on intermediate filaments in the proximal portion of the processes. The immunohistochemical profile appeared similar to that of CD34; however, a double immunofluorescence study demonstrated that no cells showed reactivity for both p57/Kip2 and CD34. The frequencies of the p57/Kip2-positive cells in FCD IIb and HME were significantly higher than those in TSC, suggesting that the balloon cells may be heterogeneous. These findings suggest some functional significance of the protein on the cytoplasmic processes of balloon cells and appear consistent with the notion that the cells are abnormally differentiated progenitor cells.

No relation between afferent facilitation induced by digital nerve stimulation and the latency of cutaneomuscular reflexes and somatosensory evoked magnetic fields

Primary motor cortex (M1) excitability can be assessed using transcranial magnetic stimulation (TMS) and can be modulated by a conditioning electrical stimulus delivered to a peripheral nerve prior to TMS. This is known as afferent facilitation (AF). The aim of this study was to determine whether AF can be induced by digital nerve stimulation and to evaluate the relation between the interstimulus interval (ISI) required for AF and the latency of the E2 component of the cutaneomuscular reflex (CMR) and the prominent somatosensory evoked field (SEF) deflection that occurs approximately 70 ms after digital nerve stimulation (P60m). Stimulation of the digital nerve of the right index finger was followed, at various time intervals, by single-pulse TMS applied to the contralateral hemisphere. The ISI between digital nerve stimulation and TMS was 20, 30, 40, 50, 60, 70, 80, 100, 140, 180, 200, or 220 ms. Single-pulse TMS was performed alone as a control. SEFs were recorded following digital nerve stimulation of the index finger, and the equivalent current dipole of prominent deflections that occurred around 70 ms after the stimulation was calculated. CMRs were recorded following digital nerve stimulation during muscle contraction. Motor evoked potentials (MEPs) were facilitated at an ISI between 50 and 100 ms in 11 of 13 subjects, and the facilitated MEP amplitude was larger than the unconditioned MEP amplitude (p < 0.01). There was no significant correlation between the ISI at which AF was maximal and the latency of the P60m component of the SEF (r = −0.50, p = 0.12) or the E2 component of the CMR (r = −0.54, p = 0.88). These results indicate that the precise ISI required for AF cannot be predicted using SEF or CMR.

Altered activity of the primary visual area during gaze processing in individuals with high-functioning autistic spectrum disorder: a magnetoencephalography study

BACKGROUND

Individuals with autistic spectrum disorder (ASD) demonstrate an impaired ability to infer the mental states of others from their gaze. Thus, investigating the relationship between ASD and eye gaze processing is crucial for understanding the neural basis of social impairments seen in individuals with ASD. In addition, characteristics of ASD are observed in more comprehensive visual perception tasks. These visual characteristics of ASD have been well-explained in terms of the atypical relationship between high- and low-level gaze processing in ASD.

METHOD

We studied neural activity during gaze processing in individuals with ASD using magnetoencephalography, with a focus on the relationship between high- and low-level gaze processing both temporally and spatially. Minimum Current Estimate analysis was applied to perform source analysis of magnetic responses to gaze stimuli.

RESULTS

The source analysis showed that later activity in the primary visual area (V1) was affected by gaze direction only in the ASD group. Conversely, the right posterior superior temporal sulcus, which is a brain region that processes gaze as a social signal, in the typically developed group showed a tendency toward greater activation during direct compared with averted gaze processing.

CONCLUSION

These results suggest that later activity in V1 relating to gaze processing is altered or possibly enhanced in high-functioning individuals with ASD, which may underpin the social cognitive impairments in these individuals.

Effect of changes in stimulus site on activation of the posterior parietal cortex

A previous functional magnetic resonance imaging study elucidated the specific activity of the inferior parietal lobe (IPL) during a two-point discrimination task compared with that during an intensity discrimination task Akatsuka et al. (Neuroimage 40: 852-858, 2008). If the posterior parietal cortex (PPC), including IPL, is responsible for detecting changes in stimulus sites, PPC activity depends on the level of change at stimulus sites. The aim of this study was to clarify whether a particular site exists that could detect changes in stimulus sites using the oddball paradigm. Somatosensory-evoked magnetic fields were recorded in 10 right-handed subjects. Three oddball conditions were performed by all subjects, with the probability of deviant and standard stimuli being 20 and 80 %, respectively, under all three conditions. Deviant stimuli were always presented to the second digit of the hand and standard stimuli were presented to the first (small deviance: SD) and fifth digits (medium deviance: MD) of the hand and the first digit of the toe (large deviance: LD). Inter-stimulus intervals were set at 500 ms. A brain electrical source analysis showed that activities of areas 1 and 3b elicited by the deviant stimuli were not significantly different among the three conditions. In contrast, PPC activity was significantly greater for LD than for SD and MD. PPC activity tended to increase with greater deviance at stimulus sites, but activities of areas 1 and 3b did not differ. These findings suggest that PPC may have a functional role in automatic change detection systems with regard to deviance of stimulus sites.

Alternating zones selective to faces and written words in the human ventral occipitotemporal cortex

Recognition of faces and written words is associated with category-specific brain activation in the ventral occipitotemporal cortex (vOT). However, topological and functional relationships between face-selective and word-selective vOT regions remain unclear. In this study, we collected data from patients with intractable epilepsy who underwent high-density recording of surface field potentials in the vOT. "Faces" and "letterstrings" induced outstanding category-selective responses among the 24 visual categories tested, particularly in high-γ band powers. Strikingly, within-hemispheric analysis revealed alternation of face-selective and letterstring-selective zones within the vOT. Two distinct face-selective zones located anterior and posterior portions of the mid-fusiform sulcus whereas letterstring-selective zones alternated between and outside of these 2 face-selective zones. Further, a classification analysis indicated that activity patterns of these zones mostly represent dedicated categories. Functional connectivity analysis using Granger causality indicated asymmetrically directed causal influences from face-selective to letterstring-selective regions. These results challenge the prevailing view that different categories are represented in distinct contiguous regions in the vOT.

Clinical analysis of catastrophic epilepsy in infancy and early childhood: results of the Far-East Asia Catastrophic Epilepsy (FACE) study group

PURPOSE

We studied children younger than 6years old who developed catastrophic epilepsy and were registered in the FACE study group to clarify their clinical characteristics and prevalence of seizure as well as epilepsy types.

SUBJECTS

Subjects were prospectively recruited from children with epilepsy who satisfied the following criteria and underwent intensive examination between 2009 and 2012 in 14 collaborative centers: (1) younger than 6years old and (2) more than 10 seizures/month refractory to all available medical treatments including ACTH therapy, leading to significant psychosocial morbidity.

METHODS

We analyzed epilepsy onset age, predominant seizure type, etiology, neuropsychological findings, and syndromic classification according to the pre-determined registration format.

RESULTS

A total of 314 children were enrolled in this study. Epilepsy onset age in 239 cases (80%) was younger than 12months. The most frequent seizure type was epileptic spasms (ES), followed by generalized tonic seizures (GTS), which accounted for 42% and 20%, respectively. West syndrome (WS) was the most frequent epileptic syndrome and accounted for 37%, followed by unclassified epilepsy at 21%, neocortical epilepsy at 19%, Lennox-Gastaut syndrome at 12%, Dravet syndrome at 4%, Rasmussen syndrome at 2%, and others. The two most frequent causes of epilepsy were cortical dysplasia and chromosomal anomalies, as shown in 16% and 6%, respectively. However, the etiology of nearly one half of all patients remained unknown. Psychomotor development was already worse than a moderate degree in 62% of subjects at the first examination.

CONCLUSION

The highest proportion of catastrophic epilepsy was WS and its related syndromes featuring ES and GTS, followed by neocortical epilepsy, whose psychomotor development was significantly retarded at examinations.

Ictal SPECT in supplementary motor area seizures

OBJECTIVES

We used ictal single photon emission computed tomography (SPECT) to clarify the propagation pathways of epileptic discharges in patients with supplementary motor area (SMA) seizure.

METHODS

In four patients (four males, age range, 18-27 years) with SMA seizures, SPECT studies by radioisotope 99mTc-ECD were performed as a preoperative evaluation. Two of the patients remained seizure-free after complete resection of the focal cortical dysplasia on magnetic resonance (MR) images including epileptic foci. In the other two patients, MR images were normal, but subdural electrode monitoring allowed for verifying the ictal onset in the left SMA. After partial resection of the SMA including epileptic foci, these patients experienced a significant (>90%) reduction of seizure frequency. Regional cerebral blood flow (rCBF) measurements obtained under ictal and interictal conditions were compared on a voxel-by-voxel basis by means of the SPM99 paired t-test option (uncorrected p<0.001).

RESULTS

Significant increases in rCBF under ictal conditions were identified in the bilateral anterior cingulate cortex (ACC), the globus pallidus ipsilateral to epileptic foci and the contralateral cerebellar hemisphere. The right ACC included a cluster with a submaximum in the right primary sensorimotor area.

DISCUSSION

In patients with SMA seizures, the hyperperfusion areas of ictal SPECT did not localize within the SMA but spread to the adjacent cortex such as the ACC and sensorimotor cortex ipsilateral to epileptic foci. Additionally, the epileptic discharges propagated to the remote areas such as the globus pallidus and cerebellum. We caution that ictal SPECT localization in patients with SMA seizures is not always concordant to epileptic focus but reveals already spread seizure activities.

Neural activity in the posterior superior temporal region during eye contact perception correlates with autistic traits

The present study investigated the relationship between neural activity associated with gaze processing and autistic traits in typically developed subjects using magnetoencephalography. Autistic traits in 24 typically developed college students with normal intelligence were assessed using the Autism Spectrum Quotient (AQ). The Minimum Current Estimates method was applied to estimate the cortical sources of magnetic responses to gaze stimuli. These stimuli consisted of apparent motion of the eyes, displaying direct or averted gaze motion. Results revealed gaze-related brain activations in the 150-250 ms time window in the right posterior superior temporal sulcus (pSTS), and in the 150-450 ms time window in medial prefrontal regions. In addition, the mean amplitude in the 150-250 ms time window in the right pSTS region was modulated by gaze direction, and its activity in response to direct gaze stimuli correlated with AQ score. pSTS activation in response to direct gaze is thought to be related to higher-order social processes. Thus, these results suggest that brain activity linking eye contact and social signals is associated with autistic traits in a typical population.

Repeated practice of a Go/NoGo visuomotor task induces neuroplastic change in the human posterior parietal cortex: an MEG study

The posterior parietal cortex (PPC) is strongly related to task performance by evaluating sensory cues and visually guided movements. Sensorimotor processing is improved by task repetition as indicated by reduced response time. We investigated practice-induced changes in PPC visuomotor processing during a Go/NoGo task in humans using 306-channel magnetoencephalography. Eleven healthy adult males were instructed to extend the right index finger when presented with the Go stimulus (a red circle), but not to react to the NoGo stimulus (a green circle or a red square). Magnetic fields over the visual, posterior parietal, and sensorimotor cortices were measured before and after 3 days of task practice. The first peak of the visual-evoked field (VEF) occurred at approximately 80 ms after presentation of either the Go or NoGo stimulus, while a PPC response, with latency to a peak of 175.8 ± 26.7 ms, occurred only after the Go stimulus. No significant change in the first peak of VEF was measured after 3 days of task practice, but there was a significant reduction in the latency to peak PPC activity (160.1 ± 27.6 ms) and in the time from peak PPC activity to electromyogram onset. In all participants, practice resulted in a significant reduction in reaction time. These results demonstrate that practicing a sensorimotor task induces neuroplastic changes in PPC that accelerate sensorimotor processing and reduce motor response times.

Neuromagnetic activation following active and passive finger movements

The detailed time courses of cortical activities and source localizations following passive finger movement were studied using whole-head magnetoencephalography (MEG). We recorded motor-related cortical magnetic fields following voluntary movement and somatosensory-evoked magnetic fields following passive movement (PM) in 13 volunteers. The most prominent movement-evoked magnetic field (MEF1) following active movement was obtained approximately 35.3 ± 8.4 msec after movement onset, and the equivalent current dipole (ECD) was estimated to be in the primary motor cortex (Brodmann area 4). Two peaks of MEG response associated with PM were recorded from 30 to 100 msec after movement onset. The earliest component (PM1) peaked at 36.2 ± 8.2 msec, and the second component (PM2) peaked at 86.1 ± 12.1 msec after movement onset. The peak latency and ECD localization of PM1, estimated to be in area 4, were the same as those of the most prominent MEF following active movement. ECDs of PM2 were estimated to be not only in area 4 but also in the supplementary motor area (SMA) and the posterior parietal cortex (PPC) over the hemisphere contralateral to the movement, and in the secondary somatosensory cortex (S2) of both hemispheres. The peak latency of each source activity was obtained at 54-109 msec in SMA, 64-114 msec in PPC, and 84-184 msec in the S2. Our results suggest that the magnetic waveforms at middle latency (50-100 msec) after PM are different from those after active movement and that these waveforms are generated by the activities of several cortical areas, that is, area 4 and SMA, PPC, and S2. In this study, the time courses of the activities in SMA, PPC, and S2 accompanying PM in humans were successfully recorded using MEG with a multiple dipole analysis system.

Oligodendroglioma (WHO grade I) in a young epilepsy patient: a specific entity lying within the spectrum of dysembryoplastic neuroepithelial tumor?

We studied a frontal lobe subcortical cystic tumor that had been resected from a 13-year-old girl with a 3-year history of intractable partial seizure. Currently, more than 13 years after surgery, the patient remains recurrence-free and has no neurological deficits. Histological examination showed that the tumor was non-infiltrating and paucicellular with a mucinous matrix, and consisted of fairly uniform small cells with round to oval nuclei. Within the mucinous matrix, the tumor cells were often arranged in pseudorosettes around small blood vessels. Mitotic activity and necrosis were absent, with a Ki-67 labeling index of <1%. Based on the immunohistochemical and ultrastructural findings, the constituent tumor cells were considered to be those of oligodendroglioma, including mini-gemistocytes and gliofibrillary oligodendrocytes. No neuronal elements were identified. Features of cortical dysplasia (FCD Type 1) were evident in the cortex covering the lesion. The surrounding white matter also contained a significant number of ectopic neurons. The entire pathological picture appeared to differ somewhat from that of ordinary oligodendroglioma (WHO grade II). Considering the clinical and pathological features, the present unusual oligodendroglioma appeared to represent a previously undescribed form of oligodendroglioma (WHO grade I) lying within the spectrum of dysembryoplastic neuroepithelial tumor (DNT; WHO grade I). Simultaneously, the present oligodendroglioma also raises the question of whether or not oligodendrocyte-like cells of DNTs truly show neurocytic differentiation.

Significance of horizontal propagation of synchronized activities in human epileptic neocortex investigated by optical imaging and immunohistological study

To characterize the physiological condition of human epileptic neocortex, we employed flavoprotein fluorescence imaging (FFI), an optical imaging method which detects intrinsic signals accompanying neural activation, and immunohistologically studied human cortical specimens. The experimented materials were cortical tissues surrounding various intracerebral lesions obtained from 5 patients with epilepsy (epileptic patients: EPs) and 5 without epilepsy (non-epileptic patients: NEPs). These tissues were immersed in oxygenated artificial cerebrospinal fluid immediately after removal in the operating room. Signal changes of FFI in the cortical layers subjected to electrical stimulation were observed under bicuculline methiodide perfusion. Immunohistological staining for parvalbumin (PV), calbindin, and calretinin were performed on the same specimens to evaluate expressions of calcium-binding protein positive cells. The FFI study showed the characteristic cortical propagation pattern of elicited activities horizontally along the cortical layers in EPs but not in NEPs. The propagated area with more than 0.5% signal changes was significantly larger in EPs than in NEPs (p=0.008). Only the expression of PV positive neurons was significantly lower in EPs than in NEPs (p=0.006). The propagated area on FFI and the decrease in PV positive neurons correlated significantly (R=-0.78, p=0.04). The present study visualized the unique horizontal propagation of signal changes on FFI and demonstrated a correlation of this propagation with immunohistological decreases in PV positive neurons in human epileptic cortex. Further investigations may elucidate the mechanism of hyper-excitability and hyper-synchronization in epileptic cortical tissue itself.

Suppressed expression of autophagosomal protein LC3 in cortical tubers of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is characterized by benign tumors and hamartomas, including cortical tubers. Hamartin and tuberin, encoded by the TSC 1 and 2 genes, respectively, constitute a functional complex that negatively regulates the mammalian target of rapamycin (mTOR) signaling pathway, eventually promoting the induction of autophagy. In the present study, we assessed the induction of autophagy in cortical tubers surgically removed from seven patients with TSC in comparison with five controls of cortical tissue taken from non-TSC patients with epilepsy. Immunoblotting demonstrated a marked reduction of LC3B-I and LC3B-II in tubers relative to the controls. In tubers, strong, diffuse and dot-like immunoreactivity (IR) for LC3B was observed in dysmorphic neurons and balloon cells, but LC3B-IR in other neurons with normal morphology was significantly weaker than that in neurons in the controls. Immunoelectron microscopy revealed diffuse distribution of LC3B-IR within the cytoplasm of balloon cells. The dot-like pattern may correspond to abnormal aggregation bodies involving LC3. In an autopsy patient with TSC, we observed that LC3B-IR in neurons located outside of the tubers was preserved. Thus, autophagy is suppressed in tubers presumably through the mTOR pathway, and possibly a pathological autophagy reaction occurs in the dysmorphic neurons and balloon cells.

Spatiotemporal dynamics of epileptiform propagations: imaging of human brain slices

Seizure activities often originate from a localized region of the cerebral cortex and spread across large areas of the brain. The properties of these spreading abnormal discharges may account for clinical phenotypes in epilepsy patients, although the manner of their propagation and the underlying mechanisms are not well understood. In the present study we performed flavoprotein fluorescence imaging of cortical brain slices surgically resected from patients with partial epilepsy caused by various symptomatic lesions. Elicited neural activities in the epileptogenic tissue spread horizontally over the cortex momentarily, but those in control tissue taken from patients with brain tumors who had no history of epilepsy demonstrated only localized responses. Characteristically, the epileptiform propagation comprised early and late phases. When the stimulus intensity was changed gradually, the early phase showed an all-or-none behavior, whereas the late phase showed a gradual increase in the response. Moreover, the two phases were propagated through different cortical layers, suggesting that they are derived from distinct neural circuits. Morphological investigation revealed the presence of hypertrophic neurons and loss of dendritic spines, which might participate in the aberrant activities observed by flavoprotein fluorescence imaging. These findings indicate that synchronized activities of the early phase may play a key role in spreading abnormal discharges in human cortical epilepsies.

Balloon cells in the dentate gyrus in hippocampal sclerosis associated with non-herpetic acute limbic encephalitis

The presence of balloon cells, a pathognomonic cellular feature of focal cortical dysplasia type IIB, in a background of hippocampal sclerosis is rare. Here we report the surgical pathologic features of the hippocampus resected from a 32-year-old woman with mesial temporal lobe epilepsy and a precipitating history of non-herpetic acute limbic encephalitis. Histologically, the resected specimen showed features of hippocampal sclerosis with granule cell dispersion. Characteristically, many balloon cells, immunoreactive for nestin, vimentin, glial fibrillary acidic protein (GFAP), GFAP-delta and CD34, were observed in the molecular and granule cell layers of the dentate gyrus. In the present case hippocampal sclerosis was an apparently acquired alteration, rather than a result of maldevelopment. The appearance of balloon cells raises questions regarding their origin and morphogenesis.