James X. Tao

Incidence and Mechanisms of Cardiorespiratory Arrests in Epilepsy Monitoring Units (MORTEMUS): A Retrospective Study.

BACKGROUND Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in people with chronic refractory epilepsy. Very rarely, SUDEP occurs in epilepsy monitoring units, providing highly informative data for its still elusive pathophysiology. The MORTEMUS study expanded these data through comprehensive evaluation of cardiorespiratory arrests encountered in epilepsy monitoring units worldwide. METHODS Between Jan 1, 2008, and Dec 29, 2009, we did a systematic retrospective survey of epilepsy monitoring units located in Europe, Israel, Australia, and New Zealand, to retrieve data for all cardiorespiratory arrests recorded in these units and estimate their incidence. Epilepsy monitoring units from other regions were invited to report similar cases to further explore the mechanisms. An expert panel reviewed data, including video electroencephalogram (VEEG) and electrocardiogram material at the time of cardiorespiratory arrests whenever available. FINDINGS 147 (92%) of 160 units responded to the survey. 29 cardiorespiratory arrests, including 16 SUDEP (14 at night), nine near SUDEP, and four deaths from other causes, were reported. Cardiorespiratory data, available for ten cases of SUDEP, showed a consistent and previously unrecognised pattern whereby rapid breathing (18-50 breaths per min) developed after secondary generalised tonic-clonic seizure, followed within 3 min by transient or terminal cardiorespiratory dysfunction. Where transient, this dysfunction later recurred with terminal apnoea occurring within 11 min of the end of the seizure, followed by cardiac arrest. SUDEP incidence in adult epilepsy monitoring units was 5·1 (95% CI 2·6-9·2) per 1000 patient-years, with a risk of 1·2 (0·6-2·1) per 10,000 VEEG monitorings, probably aggravated by suboptimum supervision and possibly by antiepileptic drug withdrawal. INTERPRETATION SUDEP in epilepsy monitoring units primarily follows an early postictal, centrally mediated, severe alteration of respiratory and cardiac function induced by generalised tonic-clonic seizure, leading to immediate death or a short period of partly restored cardiorespiratory function followed by terminal apnoea then cardiac arrest. Improved supervision is warranted in epilepsy monitoring units, in particular during night time. FUNDING Commission of European Affairs of the International League Against Epilepsy.

Intracranial EEG substrates of scalp EEG interictal spikes.

Summary:  Purpose: To determine the area of cortical generators of scalp EEG interictal spikes, such as those in the temporal lobe epilepsy.

Localizing value of scalp EEG spikes : A simultaneous scalp and intracranial study

OBJECTIVE To determine the relationship between cortical origins of interictal and ictal EEG discharges in patients with temporal lobe epilepsy. METHODS Simultaneous cortical and scalp EEG recordings were obtained from six patients with temporal lobe epilepsy. Subdural electrode contacts active at seizure onset and when scalp ictal rhythms became evident were identified. Similarly, cortical substrates of scalp EEG spikes were identified at spike peak and at the initial rising phase of the potential. RESULTS Intracranial seizure onsets were commonly focal and involved only a few electrode contacts, as opposed to scalp ictal rhythms, which required synchronous activation of multiple electrode contacts. At the peak of scalp spikes, multiple electrode contacts were similarly active. However, at spike onset, cortical substrates were more discrete and commonly involved electrodes similar to that of seizure onsets. CONCLUSIONS Scalp EEG ictal rhythms and the peak of a scalp spike may poorly localize the epileptogenic focus because of propagation. Cortical source area at scalp spike onset is more discrete, however, and the seizure onset zone often lies within this area. SIGNIFICANCE Analysis of scalp spikes, such as source modeling, at their initial rising phase might provide useful localizing information about seizure origins in the same patient.

The impact of cerebral source area and synchrony on recording scalp electroencephalography ictal patterns.

Purpose: To determine the cerebral electroencephalography (EEG) substrates of scalp EEG seizure patterns, such as source area and synchrony, and in so doing assess the limitations of scalp seizure recording in the localization of seizure onset zones in patients with temporal lobe epilepsy.

SUDEP, suspected positional airway obstruction, and hypoventilation in postictal coma

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of mortality in patients with chronic uncontrolled epilepsy. Despite intense interest in SUDEP from the medical and scientific communities in recent years, its etiologies are still largely unresolved. A 35‐year‐old woman had SUDEP after having a generalized seizure in the prone position. The cause of her death was likely asphyxia from the convergence of postictal coma and suspected positional airway obstruction and hypoventilation, rather than the commonly suspected periictal cardiac arrhythmia or central apnea. SUDEP may share a similar etiology with sudden infant death syndrome (SIDS) and is likely preventable, at least in a proportion of cases.

The accuracy and reliability of 3D CT/MRI co-registration in planning epilepsy surgery.

OBJECTIVE To investigate the accuracy and reliability of 3D CT/MRI co-registration technique for the localization of implanted subdural electrodes in the routine epilepsy presurgical evaluation, in so doing assess its usefulness in planning the tailored resection of epileptic focus. METHODS Four external anatomic fiducial makers were used for co-registration of volumetric pre-implant brain MRI and post-implant head CT using Curry 5.0 software in 19 epilepsy presurgical candidates. The location of subdural electrodes derived from the co-registration was compared to that obtained by intra-operative digital photographs by using gyral/sulcal patterns and cortical vasculature as anatomic markers. RESULTS The mean localization error was 4.3+/-2.5 mm in all 19 patients. However, the mean localization error was 3.1+/- 1.3 mm in 13 patients with all four reliable fiducial markers; whereas the mean localization error was 6.8+/-2.4 mm in 6 patients with two or three reliable fiducial markers. CONCLUSION Visualization of subdural electrode positions on a patients cortex can be accurately performed in the routine clinical setting by 3D CT/MRI co-registration. However, the accuracy of co-registration is dependent upon having reliable surface fiducial markers. In practice, confirmation of location accuracy, such as with intra-operative digital photographs, is necessary for planning of tailored resective surgery. SIGNIFICANCE The combination of 3D CT/MRI co-registration and intra-operative digital photography techniques provides a practical and effective algorithm for the localization and validation of implanted subdural electrodes.

Association of prone position with sudden unexpected death in epilepsy

Editors’ Note: “Association of prone position with sudden unexpected death in epilepsy” raised several inquiries from our readers. Sethi suggests that since the pathogenesis of sudden unexpected death in epilepsy (SUDEP) is not yet elucidated, advising patients to sleep in the supine position, which risks aspiration, warrants careful consideration. Furthermore, based on their prior study, Lhatoo et al. believe that forced ictal version, rather than prone position, may be a SUDEP risk factor. Authors Tao et al. argue that supine sleeping can help prevent SUDEP and, although it could be associated with aspiration, babies seizing facedown risk suffocation. —Chafic Karam, MD, and Robert C. Griggs, MD

Interictal regional delta slowing is an EEG marker of epileptic network in temporal lobe epilepsy

Purpose:  Several studies have suggested that interictal regional delta slowing (IRDS) carries a lateralizing and localizing value similar to interictal spikes and is associated with favorable surgical outcomes in patients with temporal lobe epilepsy (TLE). However, whether IRDS reflects structural dysfunction or underlying epileptic activity remains controversial. The objective of this study is to determine the cortical electroencephalography (EEG) correlates of scalp‐recorded IRDS, in so doing, to further understand its clinical and biologic significances.

Tonic phase of a generalized convulsive seizure is an independent predictor of postictal generalized EEG suppression

To determine the incidence, duration, risk factors for, and clinical correlates of postictal generalized electroencephalography (EEG) suppression (PGES), and to further delineate the significance of PGES in the pathogenesis of sudden unexpected death in epilepsy (SUDEP).

Peripheral sounds rapidly activate visual cortex: evidence from electrocorticography

Neurophysiological studies with animals suggest that sounds modulate activity in primary visual cortex in the presence of concurrent visual stimulation. Noninvasive neuroimaging studies in humans have similarly shown that sounds modulate activity in visual areas even in the absence of visual stimuli or visual task demands. However, the spatial and temporal limitations of these noninvasive methods prevent the determination of how rapidly sounds activate early visual cortex and what information about the sounds is relayed there. Using spatially and temporally precise measures of local synaptic activity acquired from depth electrodes in humans, we demonstrate that peripherally presented sounds evoke activity in the anterior portion of the contralateral, but not ipsilateral, calcarine sulcus within 28 ms of sound onset. These results suggest that auditory stimuli rapidly evoke spatially specific activity in visual cortex even in the absence of concurrent visual stimulation or visual task demands. This rapid auditory-evoked activation of primary visual cortex is likely to be mediated by subcortical pathways or direct cortical projections from auditory to visual areas.