Epileptiform K-complexes and sleep spindles: An underreported phenomenon in genetic generalized epilepsy

Purpose: To study the frequency of epileptiform K-complexes and sleep spindles as well as clinical variables influencing those abnormalities. 

Methods: We prospectively performed 24-hour ambulatory EEGs in a cohort of patients with genetic generalized epilepsy diagnosed and classified according to the International League against Epilepsy criteria. Overlapping of epileptiform discharges with K-complexes and sleep spindles was defined as epileptiform K-complexes and epileptiform sleep spindles. The presence of epileptiform K-complexes and sleep spindles was tabulated for each patient, and frequencies were calculated. We performed multiple regression analysis to study the influence of clinical predictors on the occurrence of epileptiform K-complexes and sleep spindles. The predictor variables tested in the model were seizure-free duration, epilepsy duration, genetic generalized epilepsy syndrome, number of antiepileptic drugs, use of sodium valproate, and use of lamotrigine. 

Results: A total of 107 patients (37 males and 70 females) were studied. The mean age was 28.5 ± 10.7 years (range, 13-58). Juvenile absence epilepsy was the most common epilepsy syndrome in the cohort (31.8%), followed by generalized epilepsy with tonic-clonic seizures only (26.2%), juvenile myoclonic epilepsy (26.2%), and childhood absence epilepsy (14%). Epileptiform K-complexes and sleep spindles were seen in 65.4% and 10.3% of patients, respectively. None of the clinical variables had any significant impact on the occurrence of epileptiform K-complexes and sleep spindles in our multivariable analysis. Conclusions: Epileptiform K-complexes are common in the sleep EEGs of patients diagnosed with genetic generalized epilepsy. This underreported phenomenon highlights the important association of arousals and epileptiform discharges in genetic generalized epilepsy.