Magneto-optical Imaging Using Polarization Modulation Method

A magneto-optical (MO) microscope that uses the polarization modulation method has been developed for quantitative MO imaging. In this technique, images of MO rotation and ellipticity are reconstructed from three images for different polarization states; i.e., linear, right-circular, and left-circular polarization states. The three polarization states are generated either by rotating a quarter-wave plate or by changing the voltage applied to a liquid crystal modulator (LCM). Measurements are performed using a patterned thin film of Bi,Ga-substituted yttrium iron garnet prepared on a glass substrate. The values of MO rotation and ellipticity obtained from the images for several wavelengths between 450 and 650 nm are found to agree quantitatively with those obtained by an MO spectrometer. Hysteresis loops at any point of the image can be displayed by simply placing a pointer at the position. A real-time MO imaging with a rate of 1 frame/s is also achieved by using the LCM and a high-speed charge-coupled device camera

Effect of vagus nerve stimulation against generalized seizure and status epilepticus recurrence

ObjectiveVagus nerve stimulation (VNS) is a palliative surgery for drug-resistant epilepsy. The two objectives of this study were to (1) determine the seizure type most responsive to VNS and (2) investigate the preventive effect on status epilepticus (SE) recurrence.MethodsWe retrospectively reviewed 136 patients with drug-resistant epilepsy who underwent VNS implantation. We examined seizure outcomes at 6, 12, and 24 months following implantation of VNS as well as at the last visit to the Juntendo Epilepsy Center. Univariate analysis and multivariate logistic regression models were used to estimate the prognostic factors.Results125 patients were followed up for at least 1 year after VNS implantation. The percentage of patients with at least a 50% reduction in seizure frequency compared with prior to VNS implantation increased over time at 6, 12, and 24 months after VNS implantation: 28, 41, and 52%, respectively. Regarding overall seizure outcomes, 70 (56%) patients responded to VNS. Of the 40 patients with a history of SE prior to VNS implantation, 27 (67%) showed no recurrence of SE. The duration of epilepsy, history of SE prior to VNS implantation and seizure type were correlated with seizure outcomes after VNS implantation in univariate analysis (p = 0.05, p < 0.01, and p = 0.03, respectively). In multivariate logistic regression analysis, generalized seizure was associated with VNS response [odds ratio (OR): 4.18, 95% CI: 1.13–15.5, p = 0.03]. A history of SE prior to VNS implantation was associated with VNS non-responders [(OR): 0.221, 95% CI: 0.097–0.503, p < 0.01]. The duration of epilepsy, focal to bilateral tonic–clonic seizure and epileptic spasms were not significantly associated with VNS responders (p = 0.07, p = 0.71, and p = 0.11, respectively).ConclusionFollowing 125 patients with drug-resistant epilepsy for an average of 69 months, 56% showed at least 50% reduction in seizure frequency after VNS implantation. This study suggests that generalized seizure is the most responsive to VNS, and that VNS may reduce the risk of recurrence of SE. VNS was shown to be effective against generalized seizure and also may potentially influence the risk of further events of SE, two marker of disease treatment that can lead to improved quality of life

Neuronavigation assisted decompression of trigeminal neuralgia caused by cerebellopontine angle osteoma

Trigeminal neuralgia (TN) is usually caused by vascular compression of the trigeminal nerve root entry zone, but can be caused by other factors such as tumors, vascular disorders, and demyelination in multiple sclerosis. We present a rare case with a huge osteoma located on the cerebellopontine angle (CPA) and causing TN. A 48-year-old woman presented with TN caused by a huge left CPA bone tumor. Surgery was performed by the lateral suboccipital approach under neuronavigation system guidance and regional decompression of the trigeminal nerve root entry zone was achieved. Intraoperative, neuro-navigation system was very useful for identification of the trigeminal nerve entry zone because normal anatomy had been obscured by the huge osteoma. Her pain disappeared completely immediately after surgery. The histological diagnosis was osteoma. TN is an expectative symptom of CPA tumors. Osteomas should be considered in patients with CPA tumors

Statistical Features in High-Frequency Bands of Interictal iEEG Work Efficiently in Identifying the Seizure Onset Zone in Patients with Focal Epilepsy

The design of a computer-aided system for identifying the seizure onset zone (SOZ) from interictal and ictal electroencephalograms (EEGs) is desired by epileptologists. This study aims to introduce the statistical features of high-frequency components (HFCs) in interictal intracranial electroencephalograms (iEEGs) to identify the possible seizure onset zone (SOZ) channels. It is known that the activity of HFCs in interictal iEEGs, including ripple and fast ripple bands, is associated with epileptic seizures. This paper proposes to decompose multi-channel interictal iEEG signals into a number of subbands. For every 20 s segment, twelve features are computed from each subband. A mutual information (MI)-based method with grid search was applied to select the most prominent bands and features. A gradient-boosting decision tree-based algorithm called LightGBM was used to score each segment of the channels and these were averaged together to achieve a final score for each channel. The possible SOZ channels were localized based on the higher value channels. The experimental results with eleven epilepsy patients were tested to observe the efficiency of the proposed design compared to the state-of-the-art methods

Analysis of Epileptic Discharges from Implanted Subdural Electrodes in Patients with Sturge-Weber Syndrome

<div><p>Objective</p><p>Almost two-thirds of patients with Sturge-Weber syndrome (SWS) have epilepsy, and half of them require surgery for it. However, it is well known that scalp electroencephalography (EEG) does not demonstrate unequivocal epileptic discharges in patients with SWS. Therefore, we analyzed interictal and ictal discharges from intracranial subdural EEG recordings in patients treated surgically for SWS to elucidate epileptogenicity in this disorder.</p><p>Methods</p><p>Five intractable epileptic patients with SWS who were implanted with subdural electrodes for presurgical evaluation were enrolled in this study. We examined the following seizure parameters: seizure onset zone (SOZ), propagation speed of seizure discharges, and seizure duration by visual inspection. Additionally, power spectrogram analysis on some frequency bands at SOZ was performed from 60 s before the visually detected seizure onset using the EEG Complex Demodulation Method (CDM).</p><p>Results</p><p>We obtained 21 seizures from five patients for evaluation, and all seizures initiated from the cortex under the leptomeningeal angioma. Most of the patients presented with motionless staring and respiratory distress as seizure symptoms. The average seizure propagation speed and duration were 3.1 ± 3.6 cm/min and 19.4 ± 33.6 min, respectively. Significant power spectrogram changes at the SOZ were detected at 10–30 Hz from 15 s before seizure onset, and at 30–80 Hz from 5 s before seizure onset.</p><p>Significance</p><p>In patients with SWS, seizures initiate from the cortex under the leptomeningeal angioma, and seizure propagation is slow and persists for a longer period. CDM indicated beta to low gamma-ranged seizure discharges starting from shortly before the visually detected seizure onset. Our ECoG findings indicate that ischemia is a principal mechanism underlying ictogenesis and epileptogenesis in SWS.</p></div