Effects of zonisamide as add-on therapy on sleep-wake cycle in focal epilepsy: a polysomnographic study.

Purpose: The purpose of this study was to evaluate the effects of zonisamide (ZNS) as adjunctive therapy on sleep-wake cycle and daytime somnolence in adult patients affected by focal epilepsy.

Methods: Thirteen patients affected by focal epilepsy were recruited to undergo a 24-hour ambulatory polysomnography, Multiple Sleep Latency Test (MSLT), and a subjective evaluation of nocturnal sleep by means of the Pittsburgh Sleep Quality Index (PSQI) and daytime somnolence by means of the Epworth Sleepiness Scale (ESS) before and after 3 months of treatment with ZNS as add-on therapy.

Results: Twelve patients completed the study. Zonisamide therapy reduced seizures by >50% in 8 out of 12 patients. Zonisamide did not induce any significant changes in nocturnal polysomnographic variables and in PSQI scores. In addition, mean sleep latency and ESS score were unmodified after treatment.

Conclusion: Zonisamide seems to be effective and safe in focal epilepsy. Both subjective and objective sleep parameters showed no detrimental effects on nocturnal sleep and daytime somnolence in patients with focal epilepsy using ZNS. Since some AEDs induce sleep impairment, which is known to trigger EEG abnormalities and seizures and to worsen quality of life, our findings suggest a positive profile of ZNS.