Epilepsy and Sleep Disorders

Throughout the ages, sleep has been considered akin to death; indeed, Homer referred to sleep as the ‘brother of death’. However, the advent of electroecephalography (EEG) has expelled this misconception and sleep is now recognised as consisting of active brain states during which many biological processes occur, such as synaptic plasticity and memory consolidation. Sleep can be broadly divided into rapid eye movement (REM) sleep and non-REM (NREM) sleep. These sleep states cycle over 90 minutes throughout the night. NREM can be subdivided into light (stages I/II) and deep (stages III/IV) sleep (see Figure 1). As sleep progresses, deep sleep periods become shorter and are absent towards the morning; conversely, REM sleep time increases. Since different conditions occur in different sleep stages/states, the timing of events during the night is important for diagnosis. Epilepsy and sleep have an important temporal association and can interact (i.e. lack of sleep can precipitate seizures and seizures can disrupt sleep). Moreover, nocturnal epileptic seizures can be misdiagnosed as sleep disorders and vice versa.