Hui Ming Khoo

Detection of Epileptic Seizures Using Phase–Amplitude Coupling in Intracranial Electroencephalography

Seizure detection using intracranial electroencephalography (iEEG) contributes to improved treatment of patients with refractory epilepsy. For that purpose, a feature of iEEG to characterize the ictal state with high specificity and sensitivity is necessary. We evaluated the use of phase–amplitude coupling (PAC) of iEEG signals over a period of 24 h to detect the ictal and interictal states. PAC was estimated by using a synchronisation index (SI) for iEEG signals from seven patients with refractory temporal lobe epilepsy. iEEG signals of the ictal state was characterised by a strong PAC between the phase of β and the amplitude of high γ. Furthermore, using SI values, the ictal state was successfully detected with significantly higher accuracy than by using the amplitude of high γ alone. In conclusion, PAC accurately distinguished the ictal state from the interictal state.

Radiation-induced anaplastic ependymoma with a remarkable clinical response to temozolomide: a case report.

Abstract Radiation-induced gliomas are uncommon and therapeutic options are limited due to prior exposure to radiotherapy. Meanwhile, the chemotherapeutic response of anaplastic ependymoma, another rare entity in adults, is often disappointing. We report on the first recorded case of radiation-induced anaplastic ependymoma, in which an excellent clinical response to temozolomide was demonstrated.

The hemodynamic response to interictal epileptic discharges localizes the seizure-onset zone

Intracranial electroencephalography (EEG), performed presurgically in patients with drug‐resistant and difficult‐to‐localize focal epilepsy, samples only a small fraction of brain tissue and thus requires strong hypotheses regarding the possible localization of the epileptogenic zone. EEG/fMRI (functional magnetic resonance imaging), a noninvasive tool resulting in hemodynamic responses, could contribute to the generation of these hypotheses. This study assessed how these responses, despite their interictal origin, predict the seizure‐onset zone (SOZ).

A “Sling Swing Transposition” Technique With Pedicled Dural Flap for Microvascular Decompression in Hemifacial Spasm

BACKGROUND: The key to successful microvascular decompression of the neurovascular compression syndrome is maintaining the separation between the nerve and the offending vessel. OBJECTIVE: We describe a transposition technique in which a local pedicled dural flap, fashioned from the petrous posterior surface, is used to retract the offending vessel away from the root exit zone of the facial nerve in hemifacial spasm cases. METHODS: We conducted a retrospective review of microvascular decompression operations in which the offending vessel was transposed and then retained by a local pedicled dural flap made from the dura of the petrous posterior surface. RESULTS: This technique was used in 7 consecutive cases of the most recently operated series. Postoperatively, complete symptom relief was achieved in 100% of the patients without any significant surgical complications. CONCLUSION: To our knowledge, this is the first report in which an autologous anatomic structure in the cerebellopontine angle, such as petrous dura mater, is used in the microvascular decompression of the facial nerve. This is a simple yet robust method and can be considered an option for the treatment of hemifacial spasm caused by arterial compression. ABBREVIATIONS: AICA, anterior inferior cerebellar artery HFS, hemifacial spasm IAC, internal auditory canal MVD, microvascular decompression PICA, posterior inferior cerebellar artery RExZ, root exit zone VA, vertebral artery

Epileptic networks in action: Synchrony between distant hemodynamic responses

Structural and functional imaging studies in focal epilepsy often reveal distributed regions of abnormality. These are interpreted as representing the existence of epileptic networks, but the presence of actual neuronal interactions between these regions has not been demonstrated. We sought to determine whether the distributed hemodynamic responses often seen in functional magnetic resonance imaging (fMRI) studies of scalp interictal epileptic discharges (IEDs) actually correspond to synchronized neuronal activities when examining the intracerebral electroencephalogram (iEEG) at distant nodes of the network.

Robotic-Assisted and Image-Guided MRI-Compatible Stereoelectroencephalography

BACKGROUND Stereoelectroencephalography has been in regular use at the Montreal Neurological Institute since 1972. The technique has been in constant evolution to incorporate advances in materials, imaging, and robotics technology. MRI-compatible electrodes were introduced in 2007 and robotics in 2011. Here we report on the technique, safety, and advantages of our current method of stereoelectroencephalography implantation. METHODS We retrospectively reviewed all patients who underwent stereoelectroencephalography by the senior author. Technical, clinical, and radiological complications, and postimplantation outcomes were analyzed. Only patients implanted with MRI-compatible electrodes were included to review MRI abnormalities with electrodes in situ. RESULTS A total of 53 patients were implanted with 550 electrodes (average=10.4 per patient), for an average duration of 14.6 days. There was no mortality, infection, or new neurologic deficit. Two patients had a superficial screw plunge without clinical consequence. Four patients demonstrated asymptomatic MRI abnormalities (7.54% per patient, or 0.72% per electrode). MRI with electrodes in situ was used for neuronavigation in all 29 who underwent resection and yielded a histopathological diagnosis of focal cortical dysplasia in 15 MRI-negative patients. CONCLUSIONS The technique of stereoelectroencephalography described here was associated with no clinical morbidity although not without technical complications or radiologic (MRI) abnormalities. We should therefore remain vigilant in refining the technique and minimizing the number of electrodes required to answer a well-developed hypothesis regarding the epileptogenic zone. The use of MRI-compatible electrodes allowed neuronavigation using the images with the electrodes in situ, which was useful to tailor the eventual definitive resection and in localizing MRI-negative lesions.

Respiratory Function Under Intrathecal Baclofen Therapy in Patients With Spastic Tetraplegia.

Intrathecal baclofen (ITB) therapy is an effective treatment for patients with severe spasticity. However, the effect of ITB therapy on respiratory function has not been reported in detail. In this study we quantitatively analyzed the effects of ITB on the respiratory function of patients with spastic tetraplegia.

DeepIED: An epileptic discharge detector for EEG-fMRI based on deep learning

Presurgical evaluation that can precisely delineate the epileptogenic zone (EZ) is one important step for successful surgical resection treatment of refractory epilepsy patients. The noninvasive EEG-fMRI recording technique combined with general linear model (GLM) analysis is considered an important tool for estimating the EZ. However, the manual marking of interictal epileptic discharges (IEDs) needed in this analysis is challenging and time-consuming because the quality of the EEG recorded inside the scanner is greatly deteriorated compared to the usual EEG obtained outside the scanner. This is one of main impediments to the widespread use of EEG-fMRI in epilepsy. We propose a deep learning based semi-automatic IED detector that can find the candidate IEDs in the EEG recorded inside the scanner which resemble sample IEDs marked in the EEG recorded outside the scanner. The manual marking burden is greatly reduced as the expert need only edit candidate IEDs. The model is trained on data from 30 patients. Validation of IEDs detection accuracy on another 37 consecutive patients shows our method can improve the median sensitivity from 50.0% for the previously proposed template-based method to 84.2%, with false positive rate as 5 events/min. Reproducibility validation on 15 patients is applied to evaluate if our method can produce similar hemodynamic response maps compared with the manual marking ground truth results. We explore the concordance between the maximum hemodynamic response and the intracerebral EEG defined EZ and find that both methods produce similar percentage of concordance (76.9%, 10 out of 13 patients, electrode was absent in the maximum hemodynamic response in two patients). This tool will make EEG-fMRI analysis more practical for clinical usage.

Electrical stimulation of the parahippocampal gyrus for prediction of posthippocampectomy verbal memory decline

OBJECTIVE Epilepsy surgery is of known benefit for drug-resistant temporal lobe epilepsy (TLE); however, a certain number of patients suffer significant decline in verbal memory after hippocampectomy. To prevent this disabling complication, a reliable test for predicting postoperative memory decline is greatly desired. Therefore, the authors assessed the value of electrical stimulation of the parahippocampal gyrus (PHG) as a provocation test of verbal memory decline after hippocampectomy on the dominant side. METHODS Eleven right-handed, Japanese-speaking patients with medically intractable left TLE participated in the study. Before surgery, they underwent provocative testing via electrical stimulation of the left PHG during a verbal encoding task. Their pre- and posthippocampectomy memory function was evaluated according to the Wechsler Memory Scale-Revised (WMS-R) and/or Mini-Mental State Examination (MMSE) before and 6 months after surgery. The relationship between postsurgical memory decline and results of the provocative test was evaluated. RESULTS Left hippocampectomy was performed in 7 of the 11 patients. In 3 patients with a positive provocative recognition test, verbal memory function, as assessed by the WMS-R, decreased after hippocampectomy, whereas in 4 patients with a negative provocative recognition test, verbal memory function, as assessed by the WMS-R or MMSE, was preserved. CONCLUSIONS Results of the present study suggest that electrical stimulation of the PHG is a reliable provocative test to predict posthippocampectomy verbal memory decline.

Which is the Most Appropriate Disconnection Surgery for Refractory Epilepsy in Childhood

Children with unilobar or multilobar pathology issuing in refractory epilepsy are potential candidates for surgical treatment. Extensive surgery results in good seizure control, but it also increases the risk of neurological deficits as well as motor and mental problems. We reviewed the cases of 19 children with refractory epilepsy treated surgically at Osaka University Hospital. Four of the 19 patients underwent temporal disconnection, 2 underwent occipital lobectomy, 4 underwent temporoparietooccipital disconnection, 6 underwent functional hemispherotomy, and 3 underwent corpus callosotomy. A good surgical outcome, i.e., Engel’s class I or II, was achieved in 12 (63%) of the 19 patients. Excellent surgical outcomes and satisfactory motor and mental development were achieved in 4 patients who underwent temporoparietooccipital disconnection. The outcomes of functional hemispherectomy were also satisfactory. The outcomes of temporal disconnection and corpus callosotomy were poor in comparison to outcomes of the other procedures. We believe that better surgical outcomes would have been achieved with temporoparietooccipital disconnection in some cases treated by temporal disconnection or occipital resection. Adequate extensive surgical procedures should be considered for refractory childhood epilepsy arising from unilobar or multilobar pathology.