CEEG monitoring detected seizure activity in 19% of patients, and the seizures were almost always nonconvulsive. Coma, age <18 years, a history of epilepsy, and convulsive seizures prior to monitoring were risk factors for electrographic seizures. Comatose patients frequently required >24 hours of monitoring to detect the first electrographic seizure.

Summary The ability to focus on and understand one talker in a noisy social environment is a critical social-cognitive capacity, whose underlying neuronal mechanisms are unclear. We investigated the manner in which speech streams are represented in brain activity and the way that selective attention governs the brain’s representation of speech using a ‘Cocktail Party’ Paradigm, coupled with direct recordings from the cortical surface in surgical epilepsy patients. We find that brain activity dynamically tracks speech streams using both low frequency phase and high frequency amplitude fluctuations, and that optimal encoding likely combines the two. In and near low level auditory cortices, attention ‘modulates’ the representation by enhancing cortical tracking of attended speech streams, but ignored speech remains represented. In higher order regions, the representation appears to become more ‘selective,’ in that there is no detectable tracking of ignored speech. This selectivity itself seems to sharpen as a sentence unfolds.

The location and trajectory of seizure activity is of great importance, yet our ability to map such activity remains primitive. Recently, the development of multi-electrode arrays for use in humans has provided new levels of temporal and spatial resolution for recording seizures. Here, we show that there is a sharp delineation between areas showing intense, hypersynchronous firing indicative of recruitment to the seizure, and adjacent territories where there is only low-level, unstructured firing. Thus, there is a core territory of recruited neurons and a surrounding 'ictal penumbra'. The defining feature of the 'ictal penumbra' is the contrast between the large amplitude EEG signals and the low-level firing there. Our human recordings bear striking similarities with animal studies of an inhibitory restraint, indicating that they can be readily understood in terms of this mechanism. These findings have important implications for how we localize seizure activity and map its spread.

Summary:Background: New continuous infusion antiepileptic drugs (cIV-AEDs) offer alternatives to pentobarbital for the treatment of refractory status epilepticus (RSE). However, no prospective randomized studies have evaluated the treatment of RSE. This systematic review compares the efficacy of midazolam (MDL), propofol (PRO), and pentobarbital (PTB) for terminating seizures and improving outcome in RSE patients.Methods: We performed a literature search of studies describing the use of MDL, PRO, or PTB for the treatment of RSE published between January 1970 and September 2001, by using MEDLINE, OVID, and manually searched bibliographies. We included peer-reviewed studies of adult patients with SE refractory to at least two standard AEDs. Main outcome measures were the frequency of immediate treatment failure (clinical or electrographic seizures occurring 1 to 6 h after starting cIV-AED therapy) and mortality according to choice of agent and titration goal (cIV-AED titration to "seizure suppression" versus "EEG background suppression").Results: Twenty-eight studies describing a total of 193 patients fulfilled our selection criteria: MDL (n ‫ס‬ 54), PRO (n ‫ס‬ 33), and PTB (n ‫ס‬ 106). Forty-eight percent of patients died, and mortality was not significantly associated with the choice of agent or titration goal. PTB was usually titrated to EEG background suppression by using intermittent EEG monitoring, whereas MDL and PRO were more often titrated to seizure suppression with continuous EEG monitoring. Compared with treatment with MDL or PRO, PTB treatment was associated with a lower frequency of short-term treatment failure (8 vs. 23%; p < 0.01), breakthrough seizures (12 vs. 42%; p < 0.001), and changes to a different cIV-AED (3 vs. 21%; p < 0.001), and a higher frequency of hypotension (systolic blood pressure <100 mm Hg; 77 vs. 34%; p < 0.001). Compared with seizure suppression (n ‫ס‬ 59), titration of treatment to EEG background suppression (n ‫ס‬ 87) was associated with a lower frequency of breakthrough seizures (4 vs. 53%; p < 0.001) and a higher frequency of hypotension (76 vs. 29%; p < 0.001).Conclusions: Despite the inherent limitations of a systematic review, our results suggest that treatment with PTB, or any cIV-AED infusion to attain EEG background suppression, may be more effective than other strategies for treating RSE. However, these interventions also were associated with an increased frequency of hypotension, and no effect on mortality was seen. A prospective randomized trial comparing different agents and titration goals for RSE with obligatory continuous EEG monitoring is needed.

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Seizures occurred in one third of patients with intracerebral hemorrhage (ICH) and over half were purely electrographic. Electrographic seizures were associated with expanding hemorrhages, and periodic discharges with cortical ICH and poor outcome. Further research is needed to determine if treating or preventing seizures or PEDs might lead to improved outcome after ICH.

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High frequency oscillations have been proposed as a clinically useful biomarker of seizure generating sites. We used a unique set of human microelectrode array recordings (four patients, 10 seizures), in which propagating seizure wavefronts could be readily identified, to investigate the basis of ictal high frequency activity at the cortical (subdural) surface. Sustained, repetitive transient increases in high gamma (80-150 Hz) amplitude, phase-locked to the low-frequency (1-25 Hz) ictal rhythm, correlated with strong multi-unit firing bursts synchronized across the core territory of the seizure. These repetitive high frequency oscillations were seen in recordings from subdural electrodes adjacent to the microelectrode array several seconds after seizure onset, following ictal wavefront passage. Conversely, microelectrode recordings demonstrating only low-level, heterogeneous neural firing correlated with a lack of high frequency oscillations in adjacent subdural recording sites, despite the presence of a strong low-frequency signature. Previously, we reported that this pattern indicates a failure of the seizure to invade the area, because of a feedforward inhibitory veto mechanism. Because multi-unit firing rate and high gamma amplitude are closely related, high frequency oscillations can be used as a surrogate marker to distinguish the core seizure territory from the surrounding penumbra. We developed an efficient measure to detect delayed-onset, sustained ictal high frequency oscillations based on cross-frequency coupling between high gamma amplitude and the low-frequency (1-25 Hz) ictal rhythm. When applied to the broader subdural recording, this measure consistently predicted the timing or failure of ictal invasion, and revealed a surprisingly small and slowly spreading seizure core surrounded by a far larger penumbral territory. Our findings thus establish an underlying neural mechanism for delayed-onset, sustained ictal high frequency oscillations, and provide a practical, efficient method for using them to identify the small ictal core regions. Our observations suggest that it may be possible to reduce substantially the extent of cortical resections in epilepsy surgery procedures without compromising seizure control.