EEG Tracings Research Articles

Trend figures assist with untrained emergency electroencephalogram interpretation.

Acute electroencephalogram (EEG) findings are important for diagnosing emergency patients with suspected neurological disorders, but they can be difficult for untrained medical staff to interpret. In this research, we will develop an emergency EEG trend figure that we hypothesize will be more easily understood by untrained staff compared with the raw original traces. For each of several EEG patterns (wakefulness, sleep, seizure activity, and encephalopathy), trend figures incorporating information on both amplitude and frequency were built. The accuracy of untrained reviewers' interpretation was compared with that of the raw EEG trace interpretation. The rate of correct answers was significantly higher in response to the EEG trend figures than to the raw traces showing wakefulness, sleep, and encephalopathy, but there was no difference when seizure activity patterns were viewed. The rates of misjudging normal or abnormal findings were significantly lower with the trend figures in the wakefulness pattern; in the other patterns, misjudgments were equally low for the trend figures and the raw traces. EEG trend figures improved the accuracy with which untrained medical staff interpreted emergency EEGs. Emergency EEG figures that can be understood intuitively with minimal training might improve the accuracy of emergency EEG interpretation. However, additional studies are required to confirm these results because there may be many types of clinical EEGs that are difficult to interpret.

Teaching Therapeutic Seizure Criteria to Psychiatrists

Following on from our previous work looking at the interrater reliability of assessing seizure adequacy for electroconvulsive therapy (ECT), we sought to examine whether a specific teaching module could improve the reliability of visual inspection of electroencephalography (EEG) recordings for specific features of seizure length, presence of polyspike, δ wave activity, and post-ictal suppression. Twelve medical practitioners at varying levels of training and ECT experience rated 15 EEG traces after minimal training and a further set of 15 EEG traces after a more detailed training. Results were analyzed to examine the interrater reliability of the EEG features and the overall assignment of traces as meeting "old" (1995) or "new" (2005) Royal College of Psychiatrists criteria for therapeutic seizures compared with the agreed ratings of 2 experienced ECT practitioners ("standard ratings"). There was evidence for a specific training effect for the "old" criteria with an improvement in the interrater reliability (generalized κ, 0.590 vs 0.813) associated with a significantly better estimation of seizure length as assessed by comparison of the root mean square difference from the standard ratings (mean, 7.83 vs 4.49; P < 0.003). The interrater reliability for the new criteria did not improve (generalized κ, 0.599 vs 0.581) but was already at quite a good standard. Examination of individual features did demonstrate improvement in the rating of δ activity (generalized κ, 0.564 vs 0.655) and post-ictal suppression (generalized κ, 0.553 vs 0.611) after the training. When these 2 criteria were grouped together (δ suppression), interrater reliability was shown to be significantly improved after the training (generalized κ, 0.568 vs 0.659). Although not statistically significant, the participants reported that the training improved their confidence in using both criteria for therapeutic seizures (old: 49% vs 67%; new: 27% vs 48%). The reliability of assessments of seizure length, presence of δ activity, and post-ictal suppression can be measurably improved with a specific teaching module. Using the δ suppression criteria together with the accurate estimation of seizure length on EEG may have greater clinical utility when it comes to instructing trainees in ECT administration, assessment of therapeutic seizures, and developing protocols for dose adjustment.

A low computational cost algorithm for REM sleep detection using single channel EEG.

The push towards low-power and wearable sleep systems requires using minimum number of recording channels to enhance battery life, keep processing load small and be more comfortable for the user. Since most sleep stages can be identified using EEG traces, enormous power savings could be achieved by using a single channel of EEG. However, detection of REM sleep from one channel EEG is challenging due to its electroencephalographic similarities with N1 and Wake stages. In this paper we investigate a novel feature in sleep EEG that demonstrates high discriminatory ability for detecting REM phases. We then use this feature, that is based on spectral edge frequency (SEF) in the 8–16 Hz frequency band, together with the absolute power and the relative power of the signal, to develop a simple REM detection algorithm. We evaluate the performance of this proposed algorithm with overnight single channel EEG recordings of 5 training and 15 independent test subjects. Our algorithm achieved sensitivity of 83%, specificity of 89% and selectivity of 61% on a test database consisting of 2221 REM epochs. It also achieved sensitivity and selectivity of 81 and 75% on PhysioNet Sleep-EDF database consisting of 8 subjects. These results demonstrate that SEF can be a useful feature for automatic detection of REM stages of sleep from a single channel EEG.Electronic supplementary materialThe online version of this article (doi:10.1007/s10439-014-1085-6) contains supplementary material, which is available to authorized users.

Circadian cycle-dependent EEG biomarkers of pathogenicity in adult mice following prenatal exposure to in utero inflammation

Intrauterine infection or inflammation in preterm neonates is a known risk for adverse neurological outcomes, including cognitive, motor and behavioral disabilities. Our previous data suggest that there is acute fetal brain inflammation in a mouse model of intrauterine exposure to lipopolysaccharides (LPS). We hypothesized that the in utero inflammation induced by LPS produces long-term electroencephalogram (EEG) biomarkers of neurodegeneration in the exposed mice that could be determined by using continuous quantitative video/EEG/electromyogram (EMG) analyses. A single LPS injection at E17 was performed in pregnant CD1 dams. Control dams were injected with same volumes of saline (LPS n=10, Control n=8). At postnatal age of P90–100, 24-h synchronous video/EEG/EMG recordings were done using a tethered recording system and implanted subdural electrodes. Behavioral state scoring was performed blind to treatment group, on each 10s EEG epoch using synchronous video, EMG and EEG trace signatures to generate individual hypnograms. Automated EEG power spectrums were analyzed for delta and theta-beta power ratios during wake vs. sleep cycles. Both control and LPS hypnograms showed an ultradian wake/sleep cycling. Since rodents are nocturnal animals, control mice showed the expected diurnal variation with significantly longer time spent in wake states during the dark cycle phase. In contrast, the LPS-treated mice lost this circadian rhythm. Sleep microstructure also showed significant alteration in the LPS mice specifically during the dark cycle, caused by significantly longer average non-rapid eye movement (NREM) cycle durations. No significance was found between treatment groups for the delta power data; however, significant activity-dependent changes in theta-beta power ratios seen in controls were absent in the LPS-exposed mice. In conclusion, exposure to in utero inflammation in CD1 mice resulted in significantly altered sleep architecture as adults that were circadian cycle and activity state dependent.

Quality parameters for a multimodal EEG/EMG/kinematic brain-computer interface (BCI) aiming to suppress neurological tremor in upper limbs.

Tremor is the most common movement disorder encountered during daily neurological practice. Tremor in the upper limbs causes functional disability and social inconvenience, impairing daily life activities. The response of tremor to pharmacotherapy is variable. Therefore, a combination of drugs is often required. Surgery is considered when the response to medications is not sufficient. However, about one third of patients are refractory to current treatments. New bioengineering therapies are emerging as possible alternatives. Our study was carried out in the framework of the European project "Tremor" (ICT-2007-224051). The main purpose of this challenging project was to develop and validate a new treatment for upper limb tremor based on the combination of functional electrical stimulation (FES; which has been shown to reduce upper limb tremor) with a brain-computer interface (BCI). A BCI-driven detection of voluntary movement is used to trigger FES in a closed-loop approach. Neurological tremor is detected using a matrix of EMG electrodes and inertial sensors embedded in a wearable textile. The identification of the intentionality of movement is a critical aspect to optimize this complex system. We propose a multimodal detection of the intentionality of movement by fusing signals from EEG, EMG and kinematic sensors (gyroscopes and accelerometry). Parameters of prediction of movement are extracted in order to provide global prediction plots and trigger FES properly. In particular, quality parameters (QPs) for the EEG signals, corticomuscular coherence and event-related desynchronization/synchronization (ERD/ERS) parameters are combined in an original algorithm which takes into account the refractoriness/responsiveness of tremor. A simulation study of the relationship between the threshold of ERD/ERS of artificial EEG traces and the QPs is also provided. Very interestingly, values of QPs were much greater than those obtained for the corticomuscular module alone.

Quality parameters for a multimodal EEG/EMG/kinematic brain-computer interface (BCI) aiming to suppress neurological tremor in upper limbs

Tremor is the most common movement disorder encountered during daily neurological practice. Tremor in the upper limbs causes functional disability and social inconvenience, impairing daily life activities. The response of tremor to pharmacotherapy is variable. Therefore, a combination of drugs is often required. Surgery is considered when the response to medications is not sufficient. However, about one third of patients are refractory to current treatments. New bioengineering therapies are emerging as possible alternatives. Our study was carried out in the framework of the European project “Tremor” (ICT-2007-224051). The main purpose of this challenging project was to develop and validate a new treatment for upper limb tremor based on the combination of functional electrical stimulation (FES; which has been shown to reduce upper limb tremor) with a brain-computer interface (BCI). A BCI-driven detection of voluntary movement is used to trigger FES in a closed-loop approach. Neurological tremor is detected using a matrix of EMG electrodes and inertial sensors embedded in a wearable textile. The identification of the intentionality of movement is a critical aspect to optimize this complex system. We propose a multimodal detection of the intentionality of movement by fusing signals from EEG, EMG and kinematic sensors (gyroscopes and accelerometry). Parameters of prediction of movement are extracted in order to provide global prediction plots and trigger FES properly. In particular, quality parameters (QPs) for the EEG signals, corticomuscular coherence and event-related desynchronization/synchronization (ERD/ERS) parameters are combined in an original algorithm which takes into account the refractoriness/responsiveness of tremor. A simulation study of the relationship between the threshold of ERD/ERS of artificial EEG traces and the QPs is also provided. Very interestingly, values of QPs were much greater than those obtained for the corticomuscular module alone.

Amplitude-integrated EEG and the newborn infant.

There is emerging recognition of the need for continuous long term electrographic monitoring of the encephalopathic neonate. While full-montage EEG with video remains the gold standard for monitoring, it is limited in application due to the complexity of lead application and specialized interpretation of results. Amplitude integrated EEG (aEEG) is derived from limited channels (usually C3-P3, C4-P4) and is filtered, rectified and time-compressed to serve as a bedside electrographic trend monitor. Its simple application and interpretation has resulted in increasing use in neonatal units across the world. Validation studies with full montage EEG have shown reliable results in interpretation of EEG background and electrographic seizures, especially when used with the simultaneously displayed raw EEG trace. Several aEEG monitors are commercially available and seizure algorithms are being developed for use on these monitors. These aEEG monitors, complement conventional EEG and offer a significant advance in the feasibility of long term electrographic monitoring of the encephalopathic neonate.

Hemodynamic changes during posterior epilepsies: An EEG-fNIRS study

Posterior epilepsies are mainly characterized clinically by visual symptoms. Functional near-infrared spectroscopy (fNIRS) is an emerging non-invasive imaging technique that has the potential to monitor hemodynamic changes during epileptic activity. Combined with electroencephalography (EEG), 9 patients with posterior epilepsies were recorded using EEG-fNIRS with large sampling (19 EEG electrodes and over 100 fNIRS channels). Spikes and seizures were carefully marked on EEG traces, and convolved with a standard hemodynamic response function for general linear model (GLM) analysis. GLM results for seizures (in 3 patients) and spikes (7 patients) were broadly sensitive to the epileptic focus in 7/9 patients, and specific in 5/9 patients with fNIRS deoxyhemoglobin responses lateralized to the correct lobe, and to plausible locations within the occipital or parietal lobes. This work provides evidence that EEG-fNIRS is a sensitive technique for monitoring posterior epileptic activity.

Decreases in Neuron Density in the Compact Zone of the Substantia Nigra Correlate with Low Peak-Wave Activity in WAG/Rij Rats

Studies in WAG/Rij rats, which have a genetic predisposition to absence epilepsy, addressed the age dynamics of convulsive activity on EEG traces in the frontal areas of the cortex and age-related changes in the cell composition of the compact zone of the substantia nigra over the age range 1–10 months. Rats aged 10 months showed significant decreases in the numbers of neurons and increases in the number of glial cells in the substantia nigra as compared with animals aged one month. During the period 5–9 months, the numbers of epileptic discharges and their durations increased by a large factor. Correlation analysis identified a positive relationship between the intensity of epileptic activity on the EEG and the number of neurons in the substantia nigra, i.e., animals with small numbers of neurons in the SN had less intense epileptic seizures and vice versa. It is suggested that the decrease in the number of neurons in the substantia nigra is an adaptive reaction directed to preventing the development of absence epilepsy.

Epilepsy-related brain networks in ring chromosome 20 syndrome: An EEG-fMRI study

To identify the brain networks that are involved in the different electroencephalography (EEG) abnormalities in patients with ring chromosome 20 [r(20)] syndrome. We hypothesize the existence of both distinctive and common brain circuits for the paroxysmal high voltage sharp waves (hSWs), the seizures, and the slow-wave 3-7Hz rhythm that characterize this condition. Thirteen patients with [r(20)] syndrome were studied by means of EEG simultaneously recorded with functional magnetic resonance imaging (EEG-fMRI). EEG traces were reviewed in order to detect the pathologic interictal (hSWs) and ictal activities; the 3-7Hz theta-delta power was derived using a fast Fourier transform. A group-level analysis was performed for each type of EEG abnormality separately using a fixed-effect model and a conjunction analysis. Finally, a second-level random-effect model was applied considering together the different EEG abnormalities, without distinction between hSW, seizures, or theta-delta rhythms. Subcontinuous theta-delta rhythm was recorded in seven patients, seizures in two, and hSWs in three patients. The main results are the following: (1) the slow-wave rhythm was related to blood oxygen level-dependent (BOLD) increases in the premotor, sensory-motor, and temporoparietal cortex, and to BOLD decrements involving the default mode (DMN) and the dorsal attention networks (DANs); (2) the ictal-related BOLD changes showed an early involvement of the prefrontal lobe; (3) increases in BOLD signal over the basal ganglia, either for interictal and ictal activities, were observed; (4) a common pattern of positive BOLD changes in the bilateral perisylvian regions was found across the different EEG abnormalities. The BOLD increment in the perisylvian network and the decrease of the DMN and DAN could be the expression of the [r(20)] syndrome-related cognitive and behavioral deficits. The observed BOLD patterns are similar to the ones detected in other epileptic encephalopathies, suggesting that different epileptic disorders characterized by neurobehavioral regression are associated with dysfunction in similar brain networks. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.

Positive effect of calcitonin on the seizures induced by pentylenetetrazole in rats

There are many difficulties involved with the treatment of epilepsy, and these problems have driven the search for new agents to control epileptic seizures. Calcitonin is a peptide hormone that has been well studied and shown to have a positive effect on neuropathic and chronic pain. The mechanism by which calcitonin affects these pain syndromes is thought to be similar to the effect of antiepileptic drugs, such as pregabalin, gabapentin and carbamazepine. In this study, we aim to investigate the effects of calcitonin on seizures induced by pentylenetetrazole (PTZ) in rats. The rats were divided into four groups. The first group was the control group, and the rats were given no medications. The second group was given saline+PTZ. The third group was given 50IU/kg calcitonin+PTZ, and the fourth group was given 100IU/kg calcitonin+PTZ. EEG traces, Racine's convulsion stages and the time of onset of the first myoclonic jerk were compared between the groups. Between the groups, there were significant differences in the Racine's convulsion stages, the onset of the 'first myoclonic jerk', and the rate of the spikes in the EEG traces. The differences were more pronounced in the 100IU/kg calcitonin-treated group (p<0.001). It has been stated that calcitonin relieves pain via regulating voltage-gated Ca(2+) and/or Na(+) channels. Calcitonin has a positive effect on convulsions in epileptic rats, possibly using the same mechanisms as is used in the treatment of neuropathic and chronic pain.

A Big-Data Approach to Automated EEG Labeling

A Big-Data Approach to Automated EEG Labeling

Évaluation du pronostic de l’encéphalopathie précoce du nouveau-né à terme avant l’avènement de l’hypothermie

Perinatal asphyxia complicated by hypoxic ischemic brain injury remains a source of neurological lesions. A major aim of neonatologists is to evaluate the severity of neonatal encephalopathy (NE) and to evaluate prognosis. The purpose of this study was to determine the contribution of brain MRI compared to electroencephalogram (EEG) and clinical data in assessing patients' prognosis. Thirty newborns from the pediatric resuscitation unit at Rouen university hospital were enrolled in a retrospective study between January 2006 and December 2008, prior to introduction of hypothermia treatment. All 30 newborns had at least two anamnestic criteria of perinatal asphyxia, one brain MRI in the first 5 days of life and another after 7 days of life as well as an early EEG in the first 2 days of life. Then, the infants were seen in consultation to assess neurodevelopment. This study showed a relation between NE stage and prognosis. During stage 1, prognosis was good, whereas stage 3 was associated with poor neurodevelopment outcome. Normal clinical examination before the 8th day of life was a good prognostic factor in this study. There was a relationship between severity of EEG after the 5th day of life and poor outcome. During stage 2, EEG patterns varied in severity, and brain MRI provided a better prognosis. Lesions of the basal ganglia and a decreased or absent signal of the posterior limb of the internal capsule were poor prognostic factors during brain MRI. These lesions were underestimated during standard MRI in the first days of life but were visible with diffusion sequences. Cognitive impairment affected 40% of surviving children, justifying extended pediatric follow-up. This study confirms the usefulness of brain MRI as a diagnostic tool in hypoxic ischemic encephalopathy in association with clinical data and EEG tracings.

Quality parameters for a multimodal EEG/EMG/kinematic brain-computer interface (BCI) aiming to suppress neurological tremor in upper limbs

Tremor is the most common movement disorder encountered during daily neurological practice. Tremor in the upper limbs causes functional disability and social inconvenience, impairing daily life activities. The response of tremor to pharmacotherapy is variable. Therefore, a combination of drugs is often required. Surgery is considered when the response to medications is not sufficient. However, about one third of patients are refractory to current treatments. New bioengineering therapies are emerging as possible alternatives. Our study was carried out in the framework of the European project “Tremor” (ICT-2007-224051). The main purpose of this challenging project was to develop and validate a new treatment for upper limb tremor based on the combination of functional electrical stimulation (FES; which has been shown to reduce upper limb tremor) with a brain-computer interface (BCI). A BCI-driven detection of voluntary movement is used to trigger FES in a closed-loop approach. Neurological tremor is detected using a matrix of EMG electrodes and inertial sensors embedded in a wearable textile. The identification of the intentionality of movement is a critical aspect to optimize this complex system. We propose a multimodal detection of the intentionality of movement by fusing signals from EEG, EMG and kinematic sensors (gyroscopes and accelerometry). Parameters of prediction of movement are extracted in order to provide global prediction plots and trigger FES properly. In particular, quality parameters (QPs) for the EEG signals, corticomuscular coherence and event-related desynchronization/synchronization (ERD/ERS) parameters are combined in an original algorithm which takes into account the refractoriness/responsiveness of tremor. A simulation study of the relationship between the threshold of ERD/ERS of artificial EEG traces and the QPs is also provided. Very interestingly, values of QPs were much greater than those obtained for the corticomuscular module alone.

Polisomnographic phenotype is linked with genetic findings in Prader–Willi syndrome

Prader-Willi syndrome (PWS) is a rare genetic disorder, usually sporadic, affecting 1/25,000 births, in which a critical region of chromosome 15 (15q11-q13) is affected. At birth, PWS infants exhibit characteristic facial features, small hands and feet, severe hypotonia with suckling and swallowing troubles, delay in psychomotor development and lethargy. After this initial phase, hyperphagia and absence of satiety (severe obesity and sleep apneas), growth hormone deficiency (short stature) and incomplete pubertal development are striking signs. Diagnosis is based on clinical criteria confirmed by genetic study, showing a deletion (DEL) or, less frequent and less severe, uniparental disomy (UPD). Eight newborn with dysmorphic features, weak reactivity to stimuli and hypotonia were evaluated. Genetic findings confirmed or excluded PWS diagnosis. Patients underwent a daily polysomnographic study (EEG, EOG, EMG, ECG, nasal airflow, respiratory movements and oxymetry); sleep and associated events were scored based on international rules for newborns (Anders et al., 1971). In 5 cases, CSF Hcrt-1 was measured. Genetic study confirmed PWS in 6 cases (DEL, n = 5 ; UPD, n = 1). Mean value of CSF Hcrt-1 in PWS-patients was 106.7 ± 16.9 pg/ml (>220 in non-PWS infants). EEG tracing was normal in 7 infants according to postconceptional age (one with slightly generalized slowing). The most relevant finding was a dramatic reduction of arousals and reactivity to stimuli, more severe in DEL-PWS, moderate in UPD-PWS and absent in non-PWS hypotonic infants (mean arousal index 4.1 /h, 5.4 /h and 14 /h; mean fragmentation index 4.1 /h, 18.3 /h and 21 /h). No significant respiratory events were recorded and other sleep parameters were similar to those seen in healthy neonates evaluated in our hospital. Sleep disturbances are already found in newborns, even before respiratory events appear. This data suggests that lack of reactivity to stimuli in newborns may be related to difficulty in regulation of sensory stimuli, leading to further symptoms of PWS (poor satiety recognition, decreased sensitivity to pain and sleep disorders). This generalized hypoarousal-state could be the primary mechanism underlying the sleep abnormalities in PWS patients. We thank Dr. J. Santamaría (H. Clinic, Barcelona, Spain) for his cooperation in typing and measurement of cerebrospinal fluid hypocretin-1 level.

Density Spectral Array for Seizure Identification in Critically Ill Children

We evaluated the validity and interrater reliability of encephalographer interpretation of color density spectral array EEG for seizure identification was evaluated in critically ill children and explored predictors of accurate seizure identification. Conventional EEG tracings from 21 consecutive critically ill children were scored for electrographic seizures. Four 2-hour long segments from each subject were converted to 8-channel color density spectral array displays, yielding 84 images. Eight encephalographers received color density spectral array training and circled elements thought to represent seizures. Images were reviewed in random order (Group A) or with information regarding seizure presence in the initial 30 minutes and with subject images in order (Group B). Sensitivity, specificity, and interrater reliability were calculated. Factors associated with color density spectral array seizure identification were assessed. Seizure prevalence was 43% on conventional EEG. Specificity was significantly higher for Group A than Group B (92.3% vs. 78.2%, P < 0.00). Sensitivity was not significantly different between Groups A and B (64.8% vs. 75%, P = 0.22). Interrater reliability was moderate in both groups. Ten percent of images were falsely classified as containing a seizure. Seizure duration ≥2 minutes predicted identification (P < 0.001). Color density spectral array may be a useful screening tool for seizure identification by encephalographers, but it does not identify all seizures and false positives occur.

In and ex utero maturation of premature infants electroencephalographic indices

ObjectivesTo assess the effect of extra uterine life on continuity and amplitude of premature infants’ cerebral activity at different gestational age as compared to soon after birth. MethodsStable infants less than 34weeks gestation were prospectively recruited and EEG was recorded bi-weekly. Interburst interval and different wavelength amplitudes were digitally measured during the most discontinuous and most continuous (periods with longest and shortest interburst intervals, respectively) parts of the tracings. Linear regression was used to assess conceptional age prediction of interburst interval and wavelength amplitudes. Significant regression results were compared to the group of babies recorded close to delivery (newborn group). Results144 EEG tracings from 59 infants were analyzed. Interburst intervals were significantly predicted by conceptional age in the newborn group only (p⩽0.002). Delta and theta amplitudes were significantly predicted by conceptional age in the newborn group and most of the other conceptional age groups (p<0.004). No significant differences were detected between the different groups. ConclusionsOur data reiterates the normal maturation of cerebral activity in the premature infant and support the concept of similar in and ex-utero maturation of cerebral activity in stable premature infants. SignificanceThe effect of ex-utero maturation on the brain of stable premature infant is not readily discernible when using specific neonatal EEG indices.

Consecutive transcranial magnetic stimulation twitches reduce flow limitation during sleep in apnoeic patients

What is the central question of this study? A transcranial magnetic stimulation (TMS)-induced twitch applied on isolated single breaths over the motor cortex somatotopic representation of the tongue briefly recruits submental muscles and improves airflow dynamics of flow-limited respiratory cycles without arousing sleep apnoea patients. However, the mechanical impact of the TMS-induced twitch applied during consecutive breathing cycles on airflow dynamics remains unknown. What is the main finding and what is its importance? Our results show that application of TMS with the stimulator output set at the sleep submental motor threshold intensity on consecutive respiratory cycles increases inspiratory flow and reduces the turbulent airflow component. These results indicate an improvement of airflow pattern after two single consecutive TMS-induced twitches without arousing sleep apnoea patients. Transcranial magnetic stimulation (TMS)-induced twitches applied on isolated breaths briefly recruit upper airway dilator muscles and improve airflow and inspiratory volume without arousing apnoeic patients from sleep, but the effects of applying such twitches consecutively on airflow dynamics is unknown. The objective of this study was to quantify the effects of five consecutive TMS-induced twitches applied on sleep-induced obstructive hypopnoeic breaths in 10 obstructive sleep apnoea patients. Submental muscle motor threshold (SUBMT) and motor-evoked potential were measured during wakefulness and sleep. The TMS-induced twitches were applied during stable non-rapid eye movement (NREM) sleep, at the beginning of inspiration of consecutive flow-limited respiratory cycles, with the stimulator output set at sleep SUBMT. Maximal inspiratory flow, inspiratory volume, inspiratory time, shifts of electroencephalogram frequency and pulse rate variability were assessed. During sleep, SUBMT increased (wakefulness, 25.3 ± 4.9%; NREM sleep, 27.0 ± 6.2%; P = 0.02). During each series of stimulations there was a rise in maximal inspiratory flow (from 306.7 ± 123.2 to 359.8 ± 154.1 ml s(-1); P = 0.0002) and in inspiratory volume (from 346.1 ± 128.1 to 414.9 ± 171.2 ml; P = 0.02) without differences in thoraco-abdominal efforts and inspiratory time. These responses were observed in the absence of arousals and ceased immediately after TMS interruption. Transcranial magnetic stimulation-induced cortical and/or autonomic arousal was observed in 30.2% of all series of stimulation. Consecutive twitch TMS of submental muscles may lead to arousals in a minority of patients but can be applied on consecutive respiratory cycles during sleep and can significantly improve maximal inspiratory flow and inspiratory volume of flow-limited cycles.

Four dimensional chaos and intermittency in a mesoscopic model of the electroencephalogram

The occurrence of so-called four dimensional chaos in dynamical systems represented by coupled, nonlinear, ordinary differential equations is rarely reported in the literature. In this paper, we present evidence that Liley's mesoscopic theory of the electroencephalogram (EEG), which has been used to describe brain activity in a variety of clinically relevant contexts, possesses a chaotic attractor with a Kaplan-Yorke dimension significantly larger than three. This accounts for simple, high order chaos for a physiologically admissible parameter set. Whilst the Lyapunov spectrum of the attractor has only one positive exponent, the contracting dimensions are such that the integer part of the Kaplan-Yorke dimension is three, thus giving rise to four dimensional chaos. A one-parameter bifurcation analysis with respect to the parameter corresponding to extracortical input is conducted, with results indicating that the origin of chaos is due to an inverse period doubling cascade. Hence, in the vicinity of the high order, strange attractor, the model is shown to display intermittent behavior, with random alternations between oscillatory and chaotic regimes. This phenomenon represents a possible dynamical justification of some of the typical features of clinically established EEG traces, which can arise in the case of burst suppression in anesthesia and epileptic encephalopathies in early infancy.

Blume's Atlas of Pediatric and Adult Electroencephalographyedited by BlumeWarren T., HollowayGiannina M., KaibaraMasakoand YoungG. Bryan, 704 pp., Lippincott Williams &amp; Wilkins, 2011, $293.04

edited by Warren T. Blume, Giannina M. Holloway, Masako Kaibara, and G. Bryan Young, 704 pp., Lippincott Williams & Wilkins, 2011, $293.04 Blume's Atlas of Pediatric and Adult Electroencephalography is a stellar addition to the armamentarium of EEG atlases currently available and stands out as a comprehensive, valuable teaching tool for the learner at any stage in his or her career. It would be an excellent addition to the references on the bookshelf of a neurology resident, clinical neurophysiology fellow, pediatric neurologist, experienced electroencephalographer, or EEG technologist. This new second addition complements and updates the highly acclaimed first edition published in 1995, which only covered adult EEG. This second edition covers both adult and pediatric EEG, greatly expands upon information provided in chapters from the first edition, includes numerous new EEG examples, and adds new chapters, including EEG in the intensive care unit, the role of EEG in some pediatric and adult problems, and aspects of recording technique (which is helpful for EEG technologists or those opening up an EEG laboratory). Other chapters that were previously included in the first edition and also included in this edition but expanded upon are introduction, artifacts, normal EEG, epileptiform phenomena, and nonepileptiform abnormalities. Indeed, the second edition is 128 pages longer than the first and also includes online access to the hardcover edition as an e-book and provides access to online resources via the publisher's Web site using a unique access code. The e-book allows one to have access to the entire atlas on a laptop or tablet computer at any time with the ability to search for key terms and highlight text. The online resources consist of 282 additional EEG tracings covering the topics of polarity, seizures, and spikes. These online EEGs are accompanied by a detailed explanation within accompanying figure legends, and the EEG tracing itself can be saved as a .jpg or .pdf file. This online access to additional EEGs allows the depiction of the same waveforms on different montages, shows the evolution of seizure discharges over sequential samples of EEG, and includes a large sampling of spike-like artifacts compared to true epileptiform spikes.