Seneviratne U, Cook M, DʼSouza W. Epileptiform K-Complexes and Sleep Spindles: An Underreported Phenomenon in Genetic Generalized Epilepsy. J Clin Neurophysiol. 2016 Apr;33(2):156-61.
To study the frequency of epileptiform K-complexes and sleep spindles as well as clinical variables influencing those abnormalities.
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.
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.
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.
Cortical and sub-cortical excitability during spindles and K-complexes, putative attractors of epileptic activity Ioannides AA 1 , Liu L 1 1AAI Scientific Cultural Services Ltd, Lab for Human Brain Dynamics, Nicosia, Cyprus
Purpose: The ARMOR project (www.armor-project.eu) is developing a platform for home monitoring of epilepsy patients. During sleep stage II (SS2) the frequency of specific types of epileptic activity is high. It is believed that large graphoelements of SS2, spindles and K-complexes act as attractors of epileptic activity.
Method: We studied high quality whole night sleep MEG recordings of four normal subjects . The brain activity during K-complexes and spindles was compared with activity shortly during targeted baseline periods that included periods before (1-2 seconds) the graphoelements, quiet core periods of sleep stages , including SS2 and the awake state, with separate comparisons performed in the time and frequency domains.
Results: We showed widely distributed cortical foci of activity with hot spots during spindles around the central sulcus, parietal and prefrontal cortex, and during K-complexes the strongest hot spots in the anterior and motor cingulate. The statistical comparisons between periods of large K-complex and spindle activity with targeted baseline periods confirmed these findings with very high statistical significance (p< 0.0001) for each subject. However, the same comparisons showed distinct sub-cortical areas for each baseline period, suggesting significant changes in sub-cortical excitation in different sleep stages, even in the quiet periods, consistent with our earlier study .
Conclusion: Our results highlight the need to monitor epileptic activity during sleep with simultaneous characterization of sleep stages. This need will be satisfied by the output of the ARMOR project that has home monitoring capability, allowing such a characterization to be followed over extended periods and thus probe the evolution of epilepsy with unprecedented detail.
Acknowledgment: The work was partially funded by the European Commission under the Seventh Framework Program with grant ARMOR, agreement number 287720.
References:  Ioannides AA et al. (2009) MEG identifies dorsal medial brain activations during sleep, NeuroImage 44: 455-68.
Note polyspikes overlapping on the ascending limb of the surface negative wave of the K-complex.
Note polyspike-wave discharges admixed with the terminal part of a sleep spindle.
Note polyspike-wave discharges in the middle of a sleep spindle. This is best realized in the central electrodes