Kainic acid-induced limbic seizures in cats: some reflections on sleep-epilepsy interactions

Sleep and EEG interictal epileptiform abnormalities in partial epilepsy

The relationship between sleep and EEG interictal epileptiform abnormalities (IEA) has been studied from different perspectives. One of the most followed orientations regards the investigation of the effects of IEA on sleep organization, while another approach considers the modulation of IEA caused by sleep. Only the latter approach, for its practical diagnostic implications, is covered by the present review. In particular, on the basis of the literature and of personal studies, we review some relevant aspects of the relationship between the different stages of the sleep and the EEG epileptic abnormalities in partial epilepsy. In addition, the modulation of IEA by fluctuations of the level of arousal and by sleep microstructure is reviewed. Finally, the information obtained on localization of epileptic foci from recordings during wakefulness and different sleep stages is discussed.

Nocturnal sleep and daytime somnolence in untreated patients with temporal lobe epilepsy: changes after treatment with controlled-release carbamazepine

PURPOSE

To define sleep disturbances in patients with temporal lobe epilepsy (TLE) and explore the association between carbamazepine (CBZ) therapy, sleep, and daytime somnolence.

METHODS

We recorded nocturnal polysomnography and measured subjective and objective daytime somnolence in a group of newly diagnosed TLE patients, who had no evidence of anatomic brain lesion on neuroimaging and had never been treated before. Recordings were performed at baseline, after the initial administration of 400 mg CBZ-controlled release (CR) and after 1 month of treatment (400 mg twice daily b.i.d.). The findings were compared with those of a group of young healthy volunteers, both at baseline and after the first administration of CBZ. The chronic effect of CBZ-CR treatment was evaluated only in TLE patients.

RESULTS

At baseline, nocturnal sleep patterns of TLE patients did not show marked alterations when the influence of seizures, cerebral lesions, and drugs had been ruled out. In both the TLE and the control groups, initiation of CBZ therapy provoked a reduction and a fragmentation of rapid eye movement (REM) sleep and an increase in the number of sleep stage shifts. In the TLE group, these effects were almost completely reversed after 1 month of treatment, and no significant difference was noted between baseline condition and long-term follow-up. With regard to daytime sleepiness, initial administration of the drug caused an increase in objective sleepiness only in the control group. Subjective sleepiness was higher in the control group than in the TLE group but was not modified by the drug.

CONCLUSIONS

We conclude that CBZ-CR has negative effects on REM sleep during initial administration but chronic treatment does not significantly modify nocturnal sleep or daytime somnolence.

[Sleep and intra-ictal epileptic electroencephalographic activities]

From this review it appears that the slow wave sleep (SWS) increases the mean density of electroencephalographic paroxysmal activities (PA) whatever the epileptic syndrome. This pattern is not marked according to a bell curve among the epileptic population: about half the patients exhibit few or no PA during SWS, 20% show an increase during waking and another 20% during SWS. Begnin epilepsy with centro-temporal spikes is associated with an important sleep PA increase. In partial epilepsy, stage 3 and 4 sleep should increase the PA transmission. In children, a large increase in PA during SWS defines the continuous spike-wave during sleep syndrome, which is also observed in the syndrome of acquired aphasia with epilepsy of Landau-Kleffner; both conditions raise the issue of the neuropsychological consequences of the sleep PA. The sleep effect on the various epileptic models is analysed, showing a mean increase in PA during SWS and during transition between sleep and waking. This evidence is in agreement with the fact that during light sleep thalamocortical loops are functioning with an oscillatory pattern which facilitates PA expression. More hypothetic is the effect of sleep on the discharge rate of epileptic focus and on the cortical diffusion of the epileptic discharges. Gaba certainly participates in the thalamic influence, but its role on PA by the cortical and brain stem inhibition is speculative. Noradrenaline and acetylcholine, implicated in waking, reduce PA activity. Interindividual variations suggest that each epileptic has his own pathological neuronal organisation in which cortex and thalamocortical connexions are variously sensitive to the neurotransmitters implicated in sleep and waking.

Effects of seizures, kindling, and carbamazepine on sleep organization in cats

We studied the relationships between epilepsy, sleep, and anticonvulsant drugs in kindled cats. No sleep alteration was present at midkindling. When the animals became fully kindled, a reduction in REM sleep percentage and the number of entries into REM sleep were observed compared to baseline. In addition, with further seizures, an increase in the percentage of wakefulness appeared, accompanied by a further reduction in the number of entries into REM sleep. It therefore seems that there is a progressive disruption of sleep, dependent on the increasing number of tonic-clonic generalized seizures. After a seizure-free interval, REM sleep and wakefulness returned to baseline values. A reduction in the percentage of stage II compared to baseline was found and remained as a long-term effect of the kindling process. Acute administration of carbamazepine (CBZ) reduced the REM sleep percentage. This effect, paralleled by a reduction in the number of entries into REM sleep, was evident both at baseline and when the animals were fully kindled. After a large number of seizures, however, CBZ administration did not cause a further reduction in the already low percentage of REM sleep. Results are discussed with reference to previous literature. We propose a hypothesis of competition between seizure and REM sleep in the elimination of epileptogenic and hypnogenic factors.

Sleep alterations after acute administration of carbamazepine in cats

Little is known about the effects of carbamazepine (CBZ) on sleep despite the relationship between sleep and epilepsy and the common clinical use of CBZ. As part of a larger study on sleep and interictal activity in kindled cats, we performed sleep recordings in 11 normal cats before and after acute administration of CBZ. Epidural screws (frontooccipital) and depth electrodes (amygdala and hippocampus) were implanted bilaterally for EEG recording. Supraorbital screws and neck intramuscular electrodes were inserted for EOG and EMG. Ten days after electrode implantation, recordings were made of animals for 2 consecutive nights to assess baseline sleep patterns. Before the third night, cats received a single oral dose of 100 mg CBZ. After washout, a second similar drug administration was given before the fourth night. Recordings were scored for wakefulness, stage I and II of NREM sleep, REM sleep, number of stage shifts, awakenings, and REM onsets. The administration of CBZ produced a significant decrease in duration and percentage of REM sleep (p less than 0.001) and an increase in stage I NREM (p less than 0.05). Total sleep time was increased (p less than 0.05); awakenings were shorter (p less than 0.01), and stage I episodes were longer (p less than 0.01).