Béla Clemens

Effects of Generalized Interictal EEG Discharges on Sleep Stability: Assessment by Means of Cyclic Alternating Pattern

Summary: Generalized interictal EEG discharges are influenced by a biphasic (phase A and B) modality of arousal control during non‐rapid eye movement (REM) sleep termed cyclic alternating pattern (CAP). Each phase A and the following phase B compose a CAP cycle. The percentage ratio of total CAP time to total non‐REM sleep time is the CAP rate, a sleep parameter that measures the instability and fragmentation of sleep. Since CAP exerts a powerful influence on generalized interictal EEG discharges during sleep, the polysomnograms of seven epileptic patients affected by a clinically active form of primary generalized epilepsy were matched with those of seven healthy volunteers of the same age and sex to assess the influence of interictal discharges on sleep organization. No remarkable differences emerged when the traditional polysomnographic parameters were compared between the two groups. However, the epileptic patients showed significantly higher CAP rate values (52.7 vs. 34.6% p < 0.003), indicating a greater arousal instability in the sleep records of these subjects. Within the epileptic group, the CAP cycles that included at least one interictal paroxysm were significantly longer than those without EEG discharges (31.2 vs. 25.4 s; p < 0.007). The selective lengthening of CAP cycles is likely due to an exaggeration of the natural activating power of phase A when coupled with EEG paroxysms and an intensification of the inhibitory properties of the following phase B. The dynamic relationships and differences between spindles in animals, k‐complexes, and slow‐wave bursts in humans may have a functional linkage with epileptic phenomena during sleep.

Orgasmic aura—a report of seven cases

We report on seven patients who experienced an orgasmic aura at the start of their seizures. The patients (five women, two men) were aged 36-58. Three of seven patients described the exact nature of their auras only many years after their appearance, when the epilepsy diagnostic procedure became more intensive due to drug resistance. Moreover, one patient even refused any new therapeutical options due to the reportedly positive role of the orgasmic aura in her life. All of our patients had temporal lobe epilepsy. The clinical picture, EEG, MRI or SPECT findings suggested a right temporal epileptic focus in six patients, while in one patient the epileptogenic region was localised in the left temporal lobe. In the latter case, the left hemisphere was speech-dominant, while in the other cases no Wada tests were done. Our results confirm that orgasmic aura could be considered as an ictal lateralising sign to the right hemisphere, however, it has no 100% lateralising value.

Quantitative EEG effects of carbamazepine, oxcarbazepine, valproate, lamotrigine, and possible clinical relevance of the findings.

UNLABELLED Quantitative EEG (QEEG) effects of therapeutic doses of carbamazepine (CBZ), oxcarbazepine (OXC), valproate (VA) and lamotrigine (LA) monotherapy were investigated in patients with beginning epilepsy. Baseline waking EEG (EEG1) was recorded in the untreated state, the second EEG (EEG2) was done after 8 weeks of reaching the therapeutic dose. Left occipital data were used for analysis. QEEG target parameters were absolute band-power (delta: AD, theta: AT, alpha: AA, beta: AB), and alpha mean frequency (AMF). Group effects (untreated versus treated condition in the CBZ, VA, OXC, LA groups) were computed for each target parameter. One group with benign rolandic epilepsy remained untreated for clinical reasons and served to estimate the QEEG test-retest differences. In addition, the individual QEEG response to each drug was calculated as (EEG2-EEG1). RESULTS statistically significant (p<0.05) group differences indicated the QEEG domain systematically affected by the drugs. CBZ caused AT increase and AMF decrease. OXC caused AMF decrease. VA and LA did not decrease AMF (LA even increased it), but reduced broad-band power. Individual power and AMF changes showed considerable variability in each group. >0.5 Hz AMF decrease (that was reported to predict cognitive impairment in prior studies) occurred in 10/41 patients in the CBZ group but never in the OXC, VA, LA groups. The results may be utilized in planning further studies addressing the relationship between antiepileptic drugs and their CNS effects. In addition, the relationship of AED-related cognitive impairment and AMF changes was discussed.

Sleep studies in benign epilepsy of childhood with rolandic spikes. II. Analysis of discharge frequency and its relation to sleep dynamics

Summary: Polygraphic all‐night sleep recordings of 11 children with benign epilepsy of childhood with rolandic spikes (BERS) were investigated from the viewpoint of spike distribution. Spike/min ratios were calculated with regard to different sleep stages and waking, identical stages of the consecutive cycles, and stages 1–2 taking place on the descending versus the ascending slopes of sleep cycles. Maximum spike/min ratios were related to slow sleep stages, especially delta sleep, and in general to the first cycle. Stages 1–2 on the descending (DESC) slopes of consecutive cycles showed a decrease in spike density during the night, as opposed to the increasing rate of activation of the same stages on the ascending (ASC) slopes. Based on our results, we suggest that the actual drive of spiking as well as seizures in BERS is the functional overweight of sleep‐inducing mechanisms.

Interictal epileptic spiking during sleep and wakefulness in mesial temporal lobe epilepsy: A comparative study of scalp and foramen ovale electrodes

Summary:  Purpose: To assess distribution of temporal lobe spikes across different states of sleep and wakefulness in simultaneous scalp and foramen ovale (Fo) recordings.

Characteristic Distribution of Interictal Brain Electrical Activity in Idiopathic Generalized Epilepsy

Summary:  Purpose: To demonstrate the anatomic localization of the cortical sources of the interictal EEG activity in human idiopathic generalized epilepsy (IGE).

Sleep Studies in Benign Epilepsy of Childhood with Rolandic Spikes. I. Sleep Pathology

Summary: Polygraphic all‐night sleep records of 11 children with typical benign epilepsy of childhood with rolandic spikes (BERS) and those of eight nonepileptic controls were investigated with regard to sleep pathology. Basic properties of sleep organization and elec‐tromorphology were preserved in both groups. Seventeen quantitative sleep parameters were measured. Except for more waking in the BERS group, no sleep parameter showed significant differences between the BERS and the control group, but differences existed in comparison to normative values. We interpret our results as showing that in BERS epileptic neuronal malfunctioning does not affect sleep organization in a characteristic manner. The lack of detrimental interactions between epileptic neuronal behavior and pathological sleep alterations may be an additional cause of the benign course of BERS.

Valproate decreases EEG synchronization in a use-dependent manner in idiopathic generalized epilepsy

INTRODUCTION In order to explore the mechanism of action of valproate (VPA) in idiopathic generalized epilepsy (IGE), the effect of VPA on cortical EEG activity was investigated. HYPOTHESIS VPA decreases EEG synchronization in the delta and theta frequency bands in a use-dependent manner in IGE patients. METHODS First setting: EEG records of 17 untreated IGE patients (NAE group) were analyzed and compared to those of 15 healthy controls (NC group). Second setting: EEG recorded in the untreated condition (NAE) was compared to the EEG recorded in the treated condition (VPA) of the patient group. Technique and analysis: 2 min of eyes-closed, waking EEG background activity (without epileptiform potentials and artifacts) were analyzed. Absolute power (AP) and mean frequency (MF) were computed for 19 electrodes and four frequency bands (delta=1.5-3.5 Hz, theta=3.5-7.5 Hz, alpha=7.5-12.5 Hz, beta=12.5-25.0 Hz). Log-transformed data entered further analysis. Group differences were computed by means of parametric statistics including correction for multiple comparisons. The VPA-related changes (APvpa-APnae) were correlated with the degree of the baseline abnormality (APnae) and the daily dose/serum levels of VPA. MAIN RESULTS Statistically significant (p<0.05, corrected) changes in the first setting: diffuse delta, theta, alpha AP increase, mainly right hemispheric beta AP increase was found in the NAE group, as compared to the NC group. Second setting: VPA decreased delta and theta AP. Strong correlation was demonstrated between the degree of the initial AP abnormality and the VPA-related AP decrease. AP decrease did not correlate with the daily dose and the serum level of the drug. CONCLUSION The hypothesis that VPA decreased EEG synchronization in the delta and theta frequency bands in a use-dependent manner was supported. The findings contribute to the understanding of the action of VPA at the network level.

Pathological theta oscillations in idiopathic generalised epilepsy

OBJECTIVE To investigate spectral power, inter- and intra-hemispheric coherence in the interictal scalp electroencephalography (EEG) of 41 patients with idiopathic generalised epilepsy. METHODS Two minutes of eyes-closed waking interictal EEG activity was analysed. Fast Fourier transformation was performed. Raw and age-regressed, Z-transformed values were computed for 19 electrodes and 4 frequency bands: absolute power (AP, ZAP), percent power (RP, ZRP), band mean frequency (MF, ZMF), inter-hemispheric (CO, ZCO) and intra-hemispheric (IC, ZIC) coherence. Compressed values (scalp averages) were computed for each parameter and 4 frequency bands. Compressed data of the patients (GE group) and the healthy controls (C group) were compared. RESULTS ZAP across the entire 1.5-25.0 Hz range was greater in the GE than in the C group. Delta and theta ZRP was greater, alpha ZRP was less in GE than in C. ZMF and ZIC was about the same in the GE and C groups. The crucial, band-specific finding was significantly greater theta-ZCO in the GE group, in contrast to normal or decreased ZCO in the other bands. In addition, within-group correlation between ZAP of the frequency bands, correlation of ZAP and ZCO, correlation of ZIC and ZCO were different for the two groups. CONCLUSIONS The pattern of enhanced ZAP, ZRP, ZCO, together with normal ZIC and ZMF in the theta range was a peculiar, novel finding in GE. It was incompatible with any of the known patterns of altered power and coherence due to lesional or metabolic aetiology. This pattern presumably indicates the presence of a powerful, diffuse, hypersynchronous, hypercoherent theta oscillation at the thalamo-cortical level of the brain. The role of inter-hemispheric connections in maintaining this oscillation was suggested. The other findings suggest disturbed central regulation of EEG power and coherence in the interictal state.

Dopamine agonist treatment of self-induced pattern-sensitive epilepsy. a case report

Abusing his own pattern sensitivity, a mentally retarded boy displayed frequent self-induced seizures resistant to conventional anticonvulsive treatment. Bromocriptine and fenfluramine have been successful in terminating self-induced seizures by means of blocking the photosensitive triggering mechanism. Secondary to this effect, the pathological drive toward seizures diminished. The possible mechanism of action has been discussed briefly.