Purpose:  Epileptiform discharges (EDs) may be part of the internal arousing stimuli that affect the quality of sleep in patients with epilepsies. We studied the association between EDs and sleep phasic phenomena, and its relevance to seizure control in 19 patients with juvenile myoclonic epilepsy (JME).

Methods:  We analyzed the first cycle of non‐REM (rapid eye movement) sleep in 22 sleep‐deprived electroencephalography (EEG) studies and classified EDs within the cyclical alternating pattern (CAP) frame, grouping separately the EDs that occurred at the transition between phases (B to A and A to B).

Results:  Within CAP periods, 36.7% of EDs occurred in A phase, 26.7% in B phase, 31.5% at “B to A” transition, and 3% at “A to B” transition. Poor seizure control was strongly associated with increased EDs in phase B (p = 0.0016) and at the “B to A” transition (p = 0.002), but marginally with increased EDs in phase A (p = 0.03). Focal spikes were increased in phase B.

Discussion:  EDs are facilitated by increased vigilance (A phase), but they may also enhance CAP cycling by generating A phases when those that occur at the “B to A” transition are interpreted as successfully breaking through the state of reduced arousal (phase B) because of increased epileptic pressure. This promotes sleep instability and further fosters epileptic activity, and conceivably seizures. This hypothesis is also supported by the strong correlation between EDs during phase B (including “B” and “B to A”) and poor seizure control. The enhanced nonlocalizing focal spikes in phase B may reflect successful inhibition of generalized EDs.