From sleep spindles of natural sleep to spike and wave discharges of typical absence seizures: is the hypothesis still valid?

The temporal coincidence of sleep spindles and spike-and-wave discharges (SWDs) in patients with idiopathic generalized epilepsies, together with the transformation of spindles into SWDs following intramuscular injection of the weak GABAA receptor (GABAAR) antagonist, penicillin, in an experimental model, brought about the view that SWDs may represent ‘perverted’ sleep spindles. Over the last 20 years, this hypothesis has received considerable support, in particular by in vitro studies of thalamic oscillations following pharmacological/genetic manipulations of GABAARs. However, from a critical appraisal of the evidence in absence epilepsy patients and well-established models of absence epilepsy it emerges that SWDs can occur as frequently during wakefulness as during sleep, with their preferential occurrence in either one of these behavioural states often being patient dependent. Moreover, whereas the EEG expression of both SWDs and sleep spindles requires the integrity of the entire cortico-thalamo-cortical network, SWDs initiates in cortex while sleep spindles in thalamus. Furthermore, the hypothesis of a reduction in GABAAR function across the entire cortico-thalamo-cortical network as the basis for the transformation of sleep spindles into SWDs is no longer tenable. In fact, while a decreased GABAAR function may be present in some cortical layers and in the reticular thalamic nucleus, both phasic and tonic GABAAR inhibitions of thalamo-cortical neurons are either unchanged or increased in this epileptic phenotype. In summary, these differences between SWDs and sleep spindles question the view that the EEG hallmark of absence seizures results from a transformation of this EEG oscillation of natural sleep

Safety and efficacy of vigabatrin and carbamazepine in newly diagnosed epilepsy: a multicentre randomised double-blind study.

BACKGROUND: Vigabatrin is a newly licensed drug for use in patients with epilepsy. We investigated whether this drug was comparable to standard first-line monotherapy in efficacy and incidence of adverse events. METHODS: We enrolled 459 patients with newly diagnosed, previously untreated partial epileptic seizures from 44 European centres and randomly assigned them carbamazepine 600 mg daily (n=230) or vigabatrin 2 g daily (n=229). After initial maintenance doses were reached, doses were adjusted downwards (in the case of adverse events) or upwards (in the case of seizures) by the clinician. The primary outcome was time to withdrawal because of lack of efficacy or adverse events. Secondary outcomes included efficacy (time to 6-month remission of seizures, time to first seizure after initial dose stabilisation), and adverse events (incidence and severity). Analysis was by intention to treat. FINDINGS: Time to withdrawal for lack of efficacy or adverse events did not differ between groups (p=0.318). Vigabatrin was better tolerated than carbamazepine with fewer withdrawals, but was more frequently associated with psychiatric symptoms (58 [25%] vs 34 [15%]) and weight gain (25 [11%] vs 12 [5%]). Carbamazepine was associated with rash (22 [10%] vs seven [3%]). All efficacy outcomes favoured carbamazepine and failed to show equivalence between the two drugs. No significant difference was found for time to achieve 6 months of remission from seizures (p=0.058), but the most powerful outcome, time to first seizure after the first 6 weeks from randomisation, showed carbamazepine to be significantly more effective than vigabatrin (p=0.0001). INTERPRETATION: Vigabatrin seems less effective but better tolerated than carbamazepine, which is the first-choice drug for the treatment of partial epilepsies. Vigabatrin cannot therefore be recommended as a first-line drug for monotherapy in this group of patients