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PubMed1991

Relationship between regulation of morphine-induced EEG effects and changes in naloxone sensitivity.

The present data indicate that pretreatment with i.c.v. injection of dynorphin, morphine and dynorphin/morphine resulted in quantitative and qualitative changes in EEG power spectra in rats given i.c.v. morphine 24 h later. Correlated changes in sensitivity to antagonism of these EEG effects by naloxone were also found. Rats were implanted with cortical EEG electrodes and i.c.v. and i.v. cannulas. I.c.v. injections of morphine (20 micrograms/rat) produced high-voltage, slow-wave EEG bursts (1-10 Hz) associated with behavioral stupor which lasted about 2 h. Injections of i.c.v. morphine in rats pretreated with i.c.v. dynorphin (20 micrograms/rat), morphine (20 micrograms/rat) or dynorphin/morphine 24 h earlier, produced quantitative increases in absolute EEG spectral power. Injections of i.c.v. morphine in rats pretreated with i.c.v. dynorphin/morphine 24 h earlier, also produced qualitatively different EEG power spectra with a predominant peak in the 4-6 Hz band, similar to the EEG power spectra seen after acute administration of kappa opioids. After 20 min of morphine-induced high voltage EEG bursts, i.v. naloxone was given in sequential doses (0.0025, 0.0125, 0.025, 0.050 mg/kg) every 3 min until the EEG bursts were suppressed for 20 min. Relatively low doses of naloxone suppressed morphine-induced EEG bursts in rats that received i.c.v. H2O/H2O pretreatment. Slightly higher, but significant, doses of naloxone suppressed morphine-induced EEG bursts in rats that received i.c.v. H2O/morphine or dynorphin/H2O pretreatment. Moreover, a 10-fold increase in naloxone dose was needed to suppress EEG bursts in rats that received dynorphin/morphine pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Extended BSI for continuous EEG monitoring in carotid endarterectomy.

OBJECTIVE: Carotid endarterectomy is a common procedure as a secondary prevention of stroke, and is often performed with selective shunting. Although various EEG parameters have been proposed to determine if the brain is at risk during carotid artery clamping, the common procedure is still the visual assessment of the EEG. Here, we propose an extension to the previously described brain symmetry index (BSI) [van Putten M, Peters J, Mulder S, de Haas J, Bruijninckx C, Tavy D. A brain symmetry index (BSI) for online EEG monitoring in carotid endarterectomy. Clin Neurophysiol 2004, 115(5), 1189-94.], as an additional quantitative criterion for shunt need in carotid endarterectomy. METHODS: An extension of the Brain Symmetry Index was implemented to capture both spatial (hemispheric) (sBSI) and temporal changes (tBSI) in the EEG. In this pilot study, the method is exemplified by simulation and by application to EEG records from 25 patients who underwent a carotid endarterectomy. RESULTS: Simulations show that hemispheric asymmetry is captured by changes in sBSI, only, while temporal symmetry changes, not due to changes in hemispheric asymmetry, are reflected by changes in tBSI. Combinations of changes induced changes in both parameters. This was confirmed by analysis 25 EEG records. Unilateral EEG changes during test-clamping are reflected by DeltasBSI>0.05, diffuse changes by DeltatBSI>0.02 and combinations by simultaneous changes in both features. CONCLUSIONS: In this pilot study, we present a doublet of quantitative EEG features, that in principle detects any change in the spectral characteristics of the EEG, decomposing the changes into a measure that captures spatial symmetry changes (sBSI), and a measure that quantifies diffuse temporal changes, that are not due to changes in spatial symmetry (tBSI). Both features are normalized with values ranging from [0-1], and can easily be implemented on-line to support the visual analysis of the EEG in the decision for selective shunting. SIGNIFICANCE: Quantitative real-time EEG analysis will assist in the EEG interpretation for selective shunting in carotid endarterectomy.

Brain↗
PubMed2006

Seizures and adverse events during routine scalp electroencephalography: a clinical and EEG analysis of 1000 records.

OBJECTIVE: To quantify the incidence of seizures and adverse events during standard electroencephalography (EEG). METHODS: A retrospective random sample of 1000 of a total of 3391 reports of standard scalp EEG recordings during 2002 at Kings College Hospital were studied, and adverse events during standard EEG were recorded. Photic induced seizures and epileptiform activity were compared with the resting, hyperventilation and sleep EEG. RESULTS: Adverse events occurred in 131 records (13.1%), including seizures in 60 records (45 electro-clinical and 15 non-epileptic seizures). The overall incidence of electro-clinical seizures was not statistically different during the resting EEG (2.8%), sleep EEG (2%), hyperventilation EEG (2.1%) and during photic stimulation EEG (1.4%). There was a higher frequency of electro-clinical seizures during hyperventilation and sleep in those with a diagnosis of idiopathic generalised epilepsy (31.5%) and during photic stimulation in photosensitive patients (31%). The incidence of electro-clinical seizures was significantly less during activation procedures in focal epilepsies (2.6%). Activation techniques made a unique diagnostic contribution when routine resting EEG was normal or equivocal in 11% of cases. CONCLUSIONS: Adverse events occurred in 13.1% of records, and most were minor. Sixty of the adverse events were seizures. Those generated during the EEG were brief and safety precautions operated successfully. In those without a prior diagnosis, the chance of seizures is the same during both resting and activation EEG. In those patients with generalised epilepsy or photosensitivity, activation procedures have a higher rate of seizure induction. SIGNIFICANCE: This study has implications for informed consent for EEG.

Adolescent↗
PubMed2005

The GABAA receptor agonist THIP alters the EEG in waking and sleep of mice.

THIP is a GABA(A) agonist with hypnotic properties consisting in reducing sleep latency and prolonging and consolidating sleep. THIP has been reported to increase EEG slow-wave activity (SWA; EEG power in the 0.75-4 Hz band) in non-REM (NREM) sleep in both rats and humans. We investigated the effects of THIP on sleep in C57BL/6 mice. EEG recordings were performed after 2, 4 and 6 mg/kg THIP and saline control. The results were compared with analyses of recordings obtained after 6 h of sleep deprivation (SD) in the same strain of mice. The two higher doses of THIP induced an abnormal EEG pattern both in waking and NREM sleep. The EEG was characterized by sporadic asymmetric high-voltage potentials recurring at a low-frequency (<1 Hz) on the background of a low-amplitude EEG pattern. In contrast, after SD the typical regular synchronous high amplitude delta waves predominated. THIP at 4 and 6 mg/kg led to a prominent enhancement of spectral power in the low-frequency range of the waking and sleep EEG which was much higher than the increase attained after 6 h SD. This effect was particularly prominent in the waking EEG. In NREM sleep the increase of spectral power after THIP reflected the frequency of recurrence of the high-voltage potentials, and was restricted to a narrower frequency band than after SD. The EEG changes after 2mg/kg differed little from saline control. Sleep latency was not affected by the two lower doses of THIP, and was prolonged after 6 mg/kg. REM sleep was suppressed after the two higher doses. In contrast to previous results reported in other species, THIP did not have a hypnotic action in mice. The changes induced by THIP in the waking and sleep EEG differed from those caused by enhanced physiological sleep pressure encountered after SD. Considering the abnormal EEG pattern and the similarity of the spectral changes in the sleep and waking EEG, THIP does not seem to exert a specific effect on mechanisms involved in sleep regulation.

Analysis of Variance↗
PubMed2004

Effects of epileptiform EEG discharges on cognitive function: is the concept of "transient cognitive impairment" still valid?

In this article we review the existing evidence on the cognitive impact of interictal epileptiform EEG discharges. Such cognitive impairment occurs exclusively in direct relation to episodes of epileptiform EEG discharges and must be distinguished from (post) ictal seizure effects and from the nonperiodic long-term "stable" interictal effects caused by the clinical syndrome or the underlying etiology. Especially in patients with short nonconvulsive seizures, characterized often by difficult-to-detect symptoms, the ictal or postictal effects may be overlooked and the resulting cognitive effects may be erroneously related to the epileptiform EEG discharges. The existing epidemiological data show that the prevalence of cognitive impairment during epileptiform EEG discharges is low. In one study 2.2% of the patients referred to a specialized epilepsy center for EEG recording showed a definite relationship between epileptiform EEG discharges and cognitive impairments ("transient cognitive impairment"). Several studies have sought to analyze to what extent cognitive impairment can be attributed to epileptiform EEG discharges among the other epilepsy factors (such as the effect of the clinical syndrome). These studies show that epileptiform EEG discharges have an additional and independent effect, but this effect is mild and limited to transient mechanistic cognitive processes (alertness, mental speed). This finding concurs with clinical studies that also reported only mild effects. In only exceptional cases are epileptiform EEG discharges the dominant factor explaining cognitive impairment. In addition, some studies have indicated that such mild effects may accumulate over time (when frequent epileptiform EEG discharges persist over years) and consequently result in effects on stable aspects of cognitive function such as educational achievement and intelligence. Hence, the clinical relevance is that early detection of cognitive effects of epileptiform EEG discharges and subsequent treatment may prevent a definite impact on cognitive and educational development. The disruptive effects of epileptiform EEG discharges on long-term potentiation, as established in animal experiments, may be one of the neurophysiological mechanisms underlying this accumulation. In conclusion the concept of "transient cognitive impairment" is still valid, but refinement of methodology has shown that a large proportion of presumed transient cognitive impairment can be attributed to subtle seizures, while interictal epileptic activity accounts for a much smaller part of the cognitive effects than previously thought. In particular cryptogenic partial epilepsies are associated with the risk of cognitive impairment. We hope that increased clinical awareness of this need for early detection will stimulate longitudinal and prospective research that eventually also will provide an answer to the questions of when and how epileptiform discharges that are not part of a seizure need to be treated.

Adult↗
PubMed1998

Ocular artifacts in children's EEG: selection is better than correction.

The electroencephalogram (EEG) during middle childhood may be highly distorted by the occurrence of eye and head movement artifacts. Between 5 and 12 years children display a great number of such artifacts. In the present study we studied different methods to assess EEG artifacts in children. Three artifact treatments were compared with the uncorrected EEG: one widely used method which corrected the EEG for electrooculogram (EOG) EEG transfer and two methods which selected artifact-free EEG segments. The most effective method should selectively reduce the spectral power in the lower frequency bands and at the frontal regions which are most susceptible to eye artifacts. The results demonstrated that the selection procedure, which combined two criteria for the selection of artifact-free EEG segments, was superior. The procedure that corrected the EEG for EOG-EEG transfer unselectively removed spectral power across the whole scalp and across all frequency bands. Furthermore, part of the maturational change in frontal Alpha power was filtered out by the correction procedure. It was concluded that for the background EEG in children, it is better to carefully select artifact-free EEG segments than to correct for EOG-EEG transfer.

Age Factors↗
PubMed2001

Prognostic value of EEG in neonatal bacterial meningitis.

The contribution of electroencephalogram (EEG) findings early in the course of neonatal bacterial meningitis to the prediction of severe adverse outcome was assessed in a retrospective cohort study. Infants had known outcomes to 1 year of age and an EEG performed during the first week of illness. EEGs were subclassified as follows: overall EEG description, background activity, presence of positive rolandic sharp waves, presence of seizure activity, and presence of focal abnormal activity. EEG patterns predictive of severe adverse outcome were identified by univariate and multivariate analyses. Of 101 infants admitted with bacterial meningitis, 37 had an EEG performed. Of the 37 infants, 21 had adverse outcomes; nine infants died, and 12 infants had moderate or severe disability. EEG background activity and overall EEG description were identified as predictors of adverse outcome; multivariate analysis indicated that the latter was a stronger predictor (sensitivity 88%, specificity 90%). Infants with normal or mildly abnormal EEGs had good outcomes whereas those with moderate to markedly abnormal EEGs died or survived with adverse outcome. The accuracy of predictions increased when EEGs were repeated. In a high-risk population of infants with bacterial meningitis, moderate-to-markedly abnormal EEG reliably predicts adverse outcome.

Brain Damage, Chronic↗
PubMed1998

[Emergency indications of EEG in the situation of a head injury in children and adults].

After initial loss of consciousness following brain injury, background EEG may show slowing and posterior slow waves are observed, consistent with the existence of commotio cerebri, particularly in children. However, discrepancies between cerebral electrogenesis and the clinical condition may also persist for several weeks. As EEG is correlated with the stage of posttraumatic coma, its reactivity to stimuli is of value. While important EEG impairment with paroxysmal abnormalities is frequent in children, the patients' outcome is poorly correlated with initial EEG record. In intensive care units, the use of continuous digitized EEG techniques has opened new avenues. Though in case of mild risks, EEG and clinical follow-up may be sufficient after brain injury, EEG recording is recommended when computerized tomography (CT-scan) is normal in case of severe risks. When consciousness impairment is unexplained by the importance of the brain injury, emergency CT-scan is recommended, searching for intracranial hematoma. If CT-scan proves to be normal EEG should then be recorded, searching for local injury. EEG may uncover non-convulsive status epilepticus, mainly in elderly patients. In case of early seizures, EEG recording should be done within the first 24 hours following brain injury. In the post-ictal period, EEG should be recorded in emergency in case of confusional state lasting more than 30 minutes, as potential non-convulsive status epilepticus should not be underestimated. EEG is not of good predictive value for posttraumatic epilepsy; however, the existence of paroxysmal, local abnormalities is a risk factor. Recording of abnormalities may be useful for the medico-legal expert.

Adult↗
PubMed2000

Acquiring simultaneous EEG and functional MRI.

OBJECTIVE: Electroencephalography (EEG) is a challenge to record simultaneously with functional MRI (fMRI), for it is prone to large artifacts induced by both the static and the time-variant fields of the MR scanner. However, truly concurrent EEG/fMRI recording has great potential for clinical and scientific neurological applications. We have devised a method for acquiring EEG simultaneously with fMRI that minimizes contamination of the EEG signals. METHODS: We recorded EEG differentially during fMRI using special twisted dual-lead electrodes in a bipolar montage, and a combination of analog pre-processing and digital post-processing of the EEG data. We implemented a functional scan protocol that typically yields artifact-free EEG over 87% of the MR scanning period. RESULTS: Our approach greatly reduced gradient, radio frequency, motion and ballistocardiographic artifact in the EEG, and allowed continuous monitoring of the EEG during functional scanning. To illustrate the quality of the EEG following post-processing, we demonstrated that EEG recorded during fMRI retains useful spectral information. CONCLUSIONS: Quality EEG may be recorded simultaneously with fMRI. With this union, activation maps could be made of any relevant changes in the EEG, such as inter-ictal spikes or spectral variations, or of evoked response potentials (ERPs).

Brain↗
PubMed2001

Melatonin is useful for recording sleep EEGs: a prospective audit of outcome.

The study aimed to determine if melatonin could reliably induce sleep in children undergoing sleep EEG without affecting the usefulness of the EEG itself. One hundred and sixty three children (112 males, 51 females; mean age 8 years, range 1 to 16 years) referred for sleep EEG were studied. The children were given 2 to 10 mg of melatonin, depending on age, just before EEG recording. Measurements included sleep-onset latency, adverse effects, and acceptability of the EEG. Usefulness and acceptability of melatonin-induced sleep EEG were compared with the standard technique of sleep EEG following sleep deprivation in 30 children (matched for sex and age). Sleep was obtained in 79% of the 163 children who received melatonin after an average of 33 minutes. Yield of epileptiform abnormalities demonstrated in the melatonin sleep EEG was similar to that reported in the literature for sleep-deprived EEGs. There was no significant adverse effect. When compared, a melatonin-induced sleep EEG was as useful as a sleep-deprived EEG. However, the children's behaviour on the day of the melatonin-induced sleep EEG recording was more acceptable to parents.

Antioxidants↗
PubMed2002

A preliminary evaluation of a new derived EEG index monitor in anesthetized patients.

BACKGROUND: An electroencephalogram (EEG) monitoring device, recently developed by Nicolet Biomedical, analyzes both high and low EEG frequencies. A processed derivative is obtained and displayed graphically and numerically on a monitor and may be used during anesthesia to indicate anesthetic "depth." However, radio-frequency interference from electrical equipment typically used in the operating room has the potential to interfere with the analysis of the high frequency components of the EEG. OBJECTIVE: The objective of this study was to determine the ability of the Nicolet EEG monitoring device to function satisfactorily and effectively in the operating arena when used for anesthetized patients. METHODS: A total of 40 patients undergoing surgery with general anesthesia were monitored using a prototype, processed EEG monitoring device. The device was used beginning prior to induction and continuing until emergence from anesthesia. RESULTS: Analysis was performed on 38 of the 40 patients. Brief interruption of the derived EEG Index occurred during use of the monopolar electrosurgical unit (ESU) as well as during stimulation of the facial nerve (used to monitor pharmacologic muscle relaxation). Derived EEG Index interruption was also noted during some movements of the patient's head or the EEG electrode wires. Changes in the derived EEG Index value accompanied changes in inhaled concentration of anesthetics and, in one patient, change in the derived EEG Index preceded patient movement that was not heralded by the typical cardiovascular indications of "light" anesthesia. CONCLUSIONS: The derived EEG Index monitoring system evaluated in this study functioned satisfactorily in the operating room setting in patients undergoing general anesthesia. Interference from ESU, facial nerve stimulation, and movement of the electrode wires caused brief interruptions of the derived EEG Index display and did not affect its utility in monitoring brain activity during anesthesia.

Adult↗
PubMed2003

Angelman syndrome: difficulties in EEG pattern recognition and possible misinterpretations.

PURPOSE: This study aimed to evaluate the sensitivity of the EEG in Angelman syndrome (AS), to verify the age at onset of suggestive EEGs and to study EEG patterns, analyzing variations and comparing our findings with nomenclature previously used. METHODS: Seventy EEG and 15 V-EEGs of 26 patients were analyzed. Suggestive EEG patterns of AS were classified in delta pattern (DP), theta pattern (TP), and posterior discharges (PDs). Generic terms were used to simplify the analysis. RESULTS: Suggestive EEGs were observed in 25 (96.2%) patients. DP occurred in 22 patients with four variants-hypsarrhythmic-like: irregular, high-amplitude, generalized delta activity (DA) with multifocal epileptiform discharges (EDs); slow variant: regular, high-amplitude, generalized DA with rare EDs; ill-defined slow spike-and-wave: regular, high-amplitude, generalized DA with superimposed EDs characterizing a slow wave, with notched appearance; triphasic-like: rhythmic, moderate-amplitude DA over anterior regions with superimposed EDs. TP was observed in eight patients, as generalized or over the posterior regions. PDs were seen in 19 patients as runs of sharp waves or runs of high-amplitude slow waves with superimposed EDs. TP was the only age-related pattern (younger than 8 years) and observed only in patients with deletion. In 15 patients who had an EEG before the clinical diagnosis, 60% had a suggestive tracing. CONCLUSIONS: Although some EEG descriptions are not very detailed, and every author describes findings in a slightly different manner, obviously a common denominator must exist. In this context, EEG seems to be a very sensitive method for the diagnosis of AS, offering an opportunity to corroborate this etiologic diagnosis. Conversely, we do not believe that these patterns may be accounted as specific, except for the delta pattern, which seems to be extremely unusual in other syndromes. Other EEG patterns observed in AS, such as theta activity and PDs, occur in a wide variety of disorders. Nonetheless, their importance for the EEG diagnosis of AS is supported by the fact that they are associated with other features and may be helpful in a proper clinical setting.

Adolescent↗
PubMed1977

Anterior shift of the dominant EEG rhytham during anesthesia in the Java monkey: correlation with anesthetic potency.

EEG amplitude dominance in awake man is posterior. During EEG monitoring in patients, the authors observed the abrupt appearance of anterior amplitude dominance during induction of anesthesia with halothane, enflurane, or thiopental. This EEG change is coincident with loss of eyelid reflex and loss of ability to respond to command. This EEG change was studied with several anesthetics in five Java monkeys to determine alveolar anesthetic concentration at which it occurred and to observe the effects of various stimuli on it. EEG recordings were obtained after equilibration at each level with increasing concentrations of halothane, enflurane or isoflurane in oxygen and each agent again in 30 per cent N2O, in separate experiments in the same animals. EEG amplitude dominance became anterior in each animal with each anesthetic and combination at concentrations less than MAC, which was also determined in the same experiments. At lower concentrations, stimulation at equilibrated anesthetic concentrations resulted in abrupt EEG return to posterior amplitude dominance. The end-tidal anesthetic concentration at which persistence of anterior EEG dominance was seen after stimulation was approximately 0.4 MAC for each anesthetic and combination tested. This is interpreted as support for physical solution-lipid solubility theories of anesthetic action. In addition, an EEG change common to various anesthetics may increase the clinical usefulness of EEG monitoring. It is speculated that this EEG change may signal loss of awareness. If so, observance of sustained anterior EEG amplitude dominance may provide assurance of obliteration of awareness during anesthesia.

Anesthetics↗
PubMed2001

Current practice in administration and clinical criteria of emergent EEG.

Policies of administration and availability of EEG offered during nonbusiness hours vary widely among EEG laboratories. The authors surveyed medical directors of accredited EEG laboratories (n = 84) to determine the ranges of availability and clinical indications for approval of continuously available emergent EEG (E-EEG). Of 46 respondents, 37 (80%) offered E-EEG. Two centers recently lost funding for E-EEG. Availability was not associated with the total number of EEGs performed annually. The mean estimated response time from request to expert interpretation was 3 +/- 4 hours (range, 1-24 hours). The five clinical indications for which most respondents approved E-EEGs were possible nonconvulsive status epilepticus (100%), treatment of status epilepticus (84%), cerebral death exam (81%), diagnosis of convulsive status epilepticus (79%), and diagnosis of coma or encephalopathy (70%). Respondents disagreed widely when asked which clinical situations merited E-EEG, with some approving all requests and others denying all except for nonconvulsive status epilepticus. The wide range of current practice suggests that research focused on outcomes of aggressive, EEG-aided patient evaluation and treatment are needed to define better the costs and benefits of a continuously available EEG service.

Brain Death↗
PubMed2004

Age-related effects in the EEG during propofol anaesthesia.

BACKGROUND: Age-related differences in the spectral composition of the EEG in induction and emergence times, and in drug consumption during propofol anaesthesia were investigated. METHODS: The EEGs of 60 female patients between 22 and 85 years of age were monitored continuously during standardized induction of anaesthesia with 2 mg of propofol kg(-1)60 s(-1). The EEGs were visually assessed in 20-s epochs according to a scale from A (awake) to F (very deep hypnosis). Visual EEG classifications, spectral parameters, and induction times were compared between different age groups. Additionally, data of 546 patients included in a multicentre study with 4630 patients (EEG monitor Narcotrend, MT MonitorTechnik, Bad Bramstedt, Germany) were analyzed with regard to age-dependent changes of propofol consumption using target-controlled infusion (TCI). RESULTS: During induction, patients older than 70 years reached significantly deeper EEG stages than younger patients, needed a longer time to reach the deepest EEG stage, and needed more time until a light EEG stage was regained. In patients aged 70 years and older, the total power, mainly in deep EEG stages, was significantly smaller due to a distinctly smaller absolute power of the delta frequency band. No single spectral parameter was able to reliably distinguish all EEG stages. During the steady state of anaesthesia, older patients needed less propofol for the maintenance of a defined stage of hypnosis than younger patients. CONCLUSION: Older patients differ from younger ones regarding the hypnotic effect of propofol and the spectral patterns in the EEG. For an efficient automatic assessment of the EEG during anaesthesia a multivariable approach accounting for age-effects is indispensable.

Adult↗
PubMedDate not supplied

EEG abnormalities in children with a first unprovoked seizure.

We examined EEG findings from an ongoing study of 347 children with a first unprovoked seizure. EEGs were available in 321 (93%), and 135 (42%) had an abnormal EEG. EEG abnormalities included focal spikes (n = 77), generalized spike and wave discharges (n = 28), slowing (n = 43), and nonspecific abnormalities (n = 7). Abnormal EEGs were more common in children with remote symptomatic seizures (60%) than in those with idiopathic seizures (38%) (p < 0.003), more common in partial seizures (56%) than in generalized seizures (35%) (p < 0.001), and more common in children age > 3 years (52%) than in younger children (12%) (p < 0.001). Records including both awake and sleep tracings were available in 148 (46%) cases. For 122 (38%) only awake tracings and for 51 (16%) only sleep tracings were available. Fifty-nine (40%) of the 148 patients with both an awake and asleep tracing had abnormal EEGs. Of 50 such EEGs with epileptiform abnormalities, 15 (30%) demonstrated the abnormality either only while awake (n = 8) or only while asleep (n = 7). Of 17 patients with EEG slowing, 8 showed slowing only in the awake tracing and 9 showed slowing in both the awake and asleep tracing. Children with even a single unprovoked seizure have a high incidence of EEG abnormalities. Obtaining a combined awake and sleep EEG significantly increases the yield of EEG abnormalities. In children with an idiopathic first seizure, EEG abnormalities are associated with an increased risk of seizure recurrence.

Adolescent↗
PubMed2004

Bilateral mesial temporal lobe epilepsy: comparison of scalp EEG and hippocampal MRI-T2 relaxometry.

OBJECTIVE: Bilateral hippocampal abnormality is frequent in mesial temporal lobe sclerosis and might affect outcome in epilepsy surgery. The objective of this study was to compare the lateralization of interictal and ictal scalp EEG with MRI T2 relaxometry. MATERIAL AND METHODS: Forty-nine consecutive patients with intractable mesial temporal lobe epilepsy (MTLE) were studied with scalp EEG/video monitoring and MRI T2 relaxometry. RESULTS: Bilateral prolongation of hippocampal T2 time was significantly associated with following bitemporal scalp EEG changes: (i) in ictal EEG left and right temporal EEG seizure onsets in different seizures, or, after regionalized EEG onset, evolution of an independent ictal EEG over the contralateral temporal lobe (left and right temporal asynchronous frequencies or lateralization switch; P = 0.002); (ii) in interictal EEG both left and right temporal interictal slowing (P = 0.007). Bitemporal T2 changes were not, however, associated with bitemporal interictal epileptiform discharges (IED). Lateralization of bilateral asymmetric or unilateral abnormal T2 findings were associated with initial regionalization of the ictal EEG in all but one patient (P < 0.005), with lateralization of IED in all patients (P < 0.005), and with scalp EEG slowing in 28 (82,4%) of 34 patients (P = 0.007). CONCLUSION: Our data suggest that EEG seizure propagation is more closely related to hippocampal T2 abnormalities than IED. Interictal and ictal scalp EEG, including the recognition of ictal propagation patterns, and MRI T2 relaxometry can help to identify patients with bitemporal damage in MTLE. Further studies are needed to estimate the impact of bilateral EEG and MRI abnormal findings on the surgical outcome.

Action Potentials↗
PubMed2006

EEG findings after a cerebral territorial infarct in patients who develop early- and late-onset seizures.

BACKGROUND: EEG findings are generally not considered to be very helpful for the diagnosis of poststroke seizures. PURPOSE: This retrospective study investigates the EEG characteristics in patients who develop seizures after a cerebral territorial infarct. PATIENTS AND METHODS: The study population consisted of 110 patients with seizures after a cerebral territorial infarct (12 with early- and 98 with late-onset seizures) and 275 without. All 110 patients had an interictal EEG after their first seizure. The EEG patterns after the stroke were compared between those available from 69 patients who developed seizures and those from 275 who did not. Also the EEG patterns after the seizure (n = 110) were compared to those in the poststroke group without subsequent seizures. RESULTS: Periodic lateralized epileptic discharges (PLEDs) on the EEG after stroke were only found in 5.8% of the patients with early- and late-onset seizures. They were absent in the stroke group without seizures. Frontal intermittent rhythmic delta activities (FIRDAs) were observed in 24.6% of the seizure group, compared to 1.1% in the control group. Diffuse slowing occurred also significantly more often in the former (21.7%) compared to the latter group (5.1%). Normal EEG findings were seen in 53.8% of the stroke patients without seizures, compared to 8.5% in those with seizures. The incidence of focal slowing was the same in both groups. Similar findings were observed when comparing the EEG patterns of the patients after the first poststroke seizure to those of the stroke group without subsequent seizures. In patients with early-onset seizures, PLEDs or FIRDAs were present in 25% each. FIRDAs and diffuse slowing were significantly more frequently observed on the poststroke EEGs of patients who developed late-onset seizures. CONCLUSIONS: FIRDAs, PLEDs and diffuse slowing are the most frequent EEG findings in patients with early-onset seizures. Patients with FIRDAs and diffuse slowing on the poststroke EEG have a high risk to develop late-onset seizures, while the chance is reduced in those with normal EEG findings.

Adolescent↗