Defining abnormal slow EEG activity in acute ischaemic stroke: Delta/alpha ratio as an optimal QEEG index

OBJECTIVE

Quantitative electroencephalographic (QEEG) indices sensitive to abnormal slow (relative to faster) activity power seem uniquely informative for clinical management of ischaemic stroke (IS), including around acute reperfusion therapies. However these have not been compared between IS and control samples. The primary objective was to identify the QEEG slowing index and threshold value which can most accurately discriminate between IS patients and controls.

METHODS

The samples comprised 28 controls (mean age: 70.4; range: 56-84) and 18 patients (mean age: 69.3; range: 51-86). Seven indices were analysed: relative bandpower (delta, theta, alpha, beta), delta/alpha power ratio (DAR), (delta+theta)/(alpha+beta) ratio (DTABR) and QSLOWING. The accuracies of each index for classifying participants (IS or control) were analysed using receiver operating characteristic (ROC) techniques.

RESULTS

All indices differed significantly between the samples (p<.001). DAR alone exhibited optimal classifier accuracy, with a threshold of 3.7 demonstrating 100% sensitivity and 100% specificity for discriminating between radiologically-confirmed, acute IS or control. DTABR and relative delta were the next most accurate classifiers.

CONCLUSIONS

DAR of 3.7 demonstrated maximal accuracy for classifying all 46 participants as acute IS or control.

SIGNIFICANCE

DAR assessment may inform clinical management of IS and perhaps other neurocritical patients.

Brain dynamics during the sleep onset transition: An EEG source localization study

EEG source localization is an essential tool to reveal the cortical sources underlying brain oscillatory activity. We applied LORETA, a technique of EEG source localization, to identify the principal brain areas involved in the process of falling asleep (sleep onset, SO). We localized the contributing brain areas of activity in the classical frequency bands and tracked their temporal evolution (in 2-min intervals from 2 min prior to SO up to 10 min after SO) during a baseline night and subsequent recovery sleep after total sleep deprivation of 40 h.

Delta activity (0.5–5 Hz) gradually increased both in baseline and recovery sleep, starting in frontal areas and finally involving the entire cortex. This increase was steeper in the recovery condition. The evolution of sigma activity (12–16 Hz) resembled an inverted U-shape in both conditions and the activity was most salient in the parietal cortex. In recovery, sigma activity reached its maximum faster than in baseline, but attained lower levels. Theta activity (5–8 Hz) increased with time in large parts of the occipital lobe (baseline and recovery) and in recovery involved additionally frontal areas. Changes in alpha activity (8–12 Hz) at sleep onset involved large areas of the cortex, whereas activity in the beta range (16–24 Hz) was restricted to small cortical areas. The dynamics in recovery could be considered as a “fast-forward version” of the one in baseline.

Our results confirm that the process of falling asleep is neither spatially nor temporally a uniform process and that different brain areas might be falling asleep at a different speed potentially reflecting use dependent aspects of sleep regulation.

•

LORETA is a valuable tool to reveal cortical sources of brain activity at sleep onset.

•

Spectral bands had location dependent dynamics; brain areas fell asleep asynchronously

•

BA 11 was the most relevant brain region associated with delta activity.

•

Spindle dynamics resembled an inverted U-shape.

•

During recovery from sleep deprivation capacity for spindle generation was reduced.

The effect of Neuroligin-2 absence on sleep architecture and electroencephalographic activity in mice

Sleep disorders are comorbid with most psychiatric disorders, but the link between these is not well understood. Neuroligin-2 (NLGN2) is a cell adhesion molecule that plays roles in synapse formation and neurotransmission. Moreover, NLGN2 has been associated with psychiatric disorders, but its implication in sleep remains underexplored. In the present study, the effect of Nlgn2 knockout (Nlgn2^−/−) on sleep architecture and electroencephalographic (EEG) activity in mice has been investigated. The EEG and electromyogram (EMG) were recorded in Nlgn2^−/− mice and littermates for 24 h from which three vigilance states (i.e., wakefulness, rapid eye movement [REM] sleep, non-REM [NREM] sleep) were visually identified. Spectral analysis of the EEG was performed for the three states. Nlgn2^−/− mice showed more wakefulness and less NREM and REM sleep compared to wild-type (Nlgn2^+/+) mice, especially during the dark period. This was accompanied by changes in the number and duration of individual episodes of wakefulness and sleep, indexing changes in state consolidation, as well as widespread changes in EEG spectral activity in all states. Abnormal ‘hypersynchronized’ EEG events have also been observed predominantly in Nlgn2^−/− mice. These events were mainly observed during wakefulness and REM sleep. In addition, Nlgn2^−/− mice showed alterations in the daily time course of NREM sleep delta (1–4 Hz) activity, pointing to modifications in the dynamics of sleep homeostasis. These data suggest that NLGN2 participates in the regulation of sleep duration as well as EEG activity during wakefulness and sleep.

The delta between postoperative seizure freedom and persistence: Automatically detected focal slow waves after epilepsy surgery

OBJECTIVE

In this study, we use a novel automated method for localization and quantitative comparison of magnetoencephalographic (MEG) delta activity in patients with and without recurrent seizures after epilepsy surgery as well as healthy controls.

METHODS

We identified the generators of delta activity by source location in frequency domain between 1 and 4 Hz in spontaneous MEG data. Comparison with healthy control subjects by z-transform emphasized relative changes of activation in patients. The individual results were compared to spike localizations and statistical group analysis was performed. Additionally, MEG results were compared to 1-4 Hz activity in invasive EEG (iEEG) in two patients, in whom this data was available.

RESULTS

Patients with recurrent seizures exhibited significantly increased focal MEG delta activity both in comparison to healthy controls and seizure free patients. This slow activity showed a correlation to interictal epileptic activity and was not explained by consequences of the resection alone. In two patients with iEEG, iEEG analysis was concordant with the MEG findings.

SIGNIFICANCE

The quantity of delta activity could be used as a diagnostic marker for recurrent seizures. The close relation to epileptic spike localizations and the resection volume of patients with successful second surgery imply involvement in seizure recurrence. This initial evidence suggests a potential application in the planning of second epilepsy surgery.

Spectral Analysis of Polysomnography in Narcolepsy

OBJECTIVE

This study was conducted to identify differences between people with narcolepsy and the normal control of delta and theta activity using electroencephalogram (EEG) spectrum analysis of nocturnal polysomnography (PSG).

METHODS

Seven narcolepsy patients and seven age-sex matched normal controls underwent PSG and multiple sleep latency tests. Participants' non-rapid eye movement (NREM) sleep EEGs in PSG was analyzed using a Fast Fourier Transform technique.

RESULTS

While NREM delta activity of people with narcolepsy declined during the first three periods of NREM, there was no change during the 4th period of NREM. The increase in NREM theta activity also lasted until the 3rd period of NREM but did not occur during the 4th period of NREM. In comparing sleep parameters, REM sleep latency in the narcolepsy group was significantly shorter than in controls.

CONCLUSION

These results suggest that people with narcolepsy are likely to have a delta and theta activity-related sleep disturbance mechanism in NREM sleep.

Early-phase EEG power spectrum analysis may differentiate acute encephalopathy with biphasic seizures and late reduced diffusion from prolonged febrile seizures

BACKGROUND

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is clinically characterized by biphasic seizures associated with mild to severe neurological sequelae and is the most common subtype of acute encephalopathy in Japan, accounting for around 30 % of cases. The present study retrospectively analyzed the utility of electroencephalography (EEG) in determining the optimal method of diagnosing AESD at the early stage.

METHODS

This study explores early power value differences to differentiate acute encephalopathy from prolonged febrile seizure (FS). The subjects were patients aged six months to four years who had received intensive care for febrile status epilepticus and had a continuous EEG record up to 24 h after seizure onset. Power spectrum analysis of consecutive, 30-minute recordings at two-hour intervals were conducted, and the power values (alpha, beta, delta, theta waves) were compared between AESD group and FS group.

RESULTS

Eight patients with AESD and 69 patients with FS were identified retrospectively. The emergence of delta waves in the frontal region was significantly higher in the AESD group at six to ten hours after onset. The emergence of beta waves across all the regions was lower in the AESD group from six hours after seizure onset.

CONCLUSIONS

Frequency analysis of EEG in the early period after febrile status epilepticus onset demonstrated a significant difference between the AESD and FS groups. Delta wave power values in the frontal region at six to ten hours after onset might be useful for the early differentiation of AESD from FS.

Ultrasound-Guided Second Trimester Fetal Electroencephalography in Two Pregnant Volunteers: A Technical Note

BACKGROUND AND PURPOSE

Data from electroencephalography (EEG) in preterm infants and neonates suggest that electroencephalographic abnormalities are likely present during antepartum period or fetal stage. We describe our initial effort to record fetal EEG with emphasis on technical aspects since such technique has not been developed as a viable and reproducible method.

METHODS

The fetal heads were located in two pregnant volunteers (29 years old and 26 years old) with 28 weeks of gestation by ultrasound imaging. Four surface electrodes were placed on maternal abdominal surface approximately 5 cm anterior to the lateral aspect of fetal head as confirmed by acoustic shadowing of the electrodes on ultrasound. A second set of recordings were performed in first volunteer with four electrodes placed on the maternal abdominal surface in front of the uterus distant to fetal head.

RESULTS

The analysis in the first volunteer demonstrated that the activity consisted of mixture of theta (4-7 Hz) and delta (1-4 Hz) waves which formed approximately 70% and 30% of the background rhythm. The analysis in the second volunteer demonstrated that the activity consisted of mixture of theta and delta, which formed approximately 30% and 70% of the background rhythm. There was superimposed beta (13-30 Hz) and infrequently gamma (30-100 Hz) activity. Maternal electrocardiographic QRS complex and respiratory artifacts were seen in some leads. During second recording, the electrodes distant to fetal head recorded predominantly delta with lesser proportion of theta waves.

CONCLUSIONS

We report our initial experience in acquisition of fetal EEG. The findings reported here will help to guide further research into developing methodologies for the performance of fetal EEG.

Trihexyphenidyl increases delta activity in non-rapid eye movement sleep without impairing cognitive function in rodent models

Both human and rodent studies suggest the link between non-rapid eye movement (NREM) sleep and cognition. Recent study indicated that selective activation of cholinergic neurons in basal forebrain inhibits electroencephalogram (EEG) delta power and shortens NREM sleep. In the current study, we aimed to test the pharmacological effect of trihexyphenidyl (THP), a selective muscarinic M1 receptor antagonist, on EEG power spectra and sleep with or without the selective activation of basal forebrain cholinergic neurons. THP (1, 2, and 3 mg/kg) was administrated intraperitoneally in natural sleep phase. Basal forebrain cholinergic neurons expressing modified G protein-coupled muscarinic receptors (hM3Dq) were activated by intraperitoneal injection of clozapine-N-oxide in ChAT-IRES-Cre mice. EEG and electromyogram (EMG) signals were recorded in freely moving mice to analyze EEG power spectrum and sleep hypnogram. Y-maze and novel object recognition tests were used for testing cognition. THP 1 mg/kg significantly increased EEG delta power and facilitated NREM sleep in wildtype mice, while THP 3 mg/kg was required in ChAT-IRES-Cre mice treated with clozapine-N-oxide. THP with dosage up to 8 mg/kg did not induce cognitive impairments in wildtype mice. EEG delta power of NREM sleep is often used as an indicator of sleep depth or sleep quality, which tightly link with sleep-dependent cognition. Taken together, the data collected from rodents hinted that, THP could possibly be used as the NREM sleep facilitator in humans.