The terms “epilepsy” and “epileptic” are derived from the Greek word epilambanien, which means to seize or to attack. Although, in the Greek era of medicine, patients were thought to be seized by demons, our current understanding is that epileptic seizures are the clinical manifestations of excessive hypersynchronous central neuronal activity and that epilepsy is a chronic condition of recurrent unprovoked epileptic seizures.

The International League Against Epilepsy divides epileptic seizures into partial seizures and generalized seizures. Partial seizures are initiated in one location and potentially spread to other regions of the brain. Primary generalized seizures involve both hemispheres at the onset. Partial seizures may be classified as simple partial (retention of memory and consciousness), complex partial (impairment of memory or consciousness), or secondarily generalized. Primary generalized seizures begin diffusely across the brain and may comprise various types of behavior. Absence seizures are characterized by brief staring episodes. Atonic seizures result in sudden loss of postural tone, resulting in unprotected falls or head drops. Tonic seizures produce generalized increase in muscle tone during the clinical event. Clonic seizures are associated with repetitive jerking. Tonic-clonic seizures start with tonic activity that progresses to clonic activity; myoclonic seizures are single rapid jerks. A summary is given in Table 31-1.

The clinical diagnosis of epilepsy is made on the basis of recurrent unprovoked epileptic seizures. Individuals with epilepsy can have multiple types of seizures that subsequently are represented as a single form of epilepsy. Epilepsies can be divided into focal-onset epilepsies and primary generalized epilepsies (Table 31-2). Both types of epilepsies can have specific relationships to the sleep-wake cycle.

In 1881, Gower (3) studied the relationship of sleep-awake state to epilepsy, noting that 21% of patients had seizures solely during sleep. He noted other patients had seizures only during the awake state (42%), whereas a third group had seizures during both the awake and asleep states (37%). A later investigation, by Janz, revealed that some individuals have seizures primarily in the first 2 hours after awakening. Janz coined the term “awakening” epilepsies for these individuals and referred to seizures occurring without dependence on the sleep-awake state as diffuse epilepsies (4,5). Many patients with a primary generalized form of epilepsy, juvenile myoclonic epilepsy, have seizures soon after awakening. On the other hand, benign epilepsy of childhood with centrotemporal spikes and autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) are forms of focal-onset epilepsies that primarily occur during sleep.

Nocturnal seizures may be associated with some of the most bizarre and obscure nighttime behaviors. The differentiation of a sleep-related phenomenon, nocturnal seizures, or psychogenic events could be difficult because of the frequent overlap of clinical descriptions (Table 31-3). Many times patients may not follow the “classical” patterns of parasomnia or epilepsy, and some patients may have a parasomnia provoked by another sleep disturbance or seizures. Thus, the diagnosis of these behaviors may require intensive investigation and monitoring of these difficult patients. The dilemma, for the physician, is to determine which procedures will yield clues of the underlying etiology, without diverting attention to inaccurate or premature conclusions.

Epilepsy is one of the most common neurologic conditions. The prevalence of epilepsy in the general population is approximately 1% to 2%. Epilepsy most frequently begins in childhood and the later adult years (6). Middle-aged adults have the lowest incidence of epilepsy. Focal-onset epilepsy is the predominant form of epilepsy beginning in the adult years, but it has the greatest incidence in childhood and late adulthood. Primary generalized epilepsies most commonly begin during childhood or adolescence.

Patients with neurologic disorders, in general, appear to have a greater prevalence of sleep disturbance than do normal subjects. This increase in prevalence appears to extend to patients with epilepsy. Miller et al. (7) reported that more than two-thirds of patients with epilepsy seen at a university center have complaints regarding sleep.
Miller et al. found that 68% complained of feeling sleepy during the day and 39% complained of difficulty falling asleep or staying asleep. Nearly 42% felt that their sleep issues interfered with their daytime performance. Khatami et al. (8) surveyed 100 patients with epilepsy and found that 30% of patients with epilepsy had sleep complaints compared with 10% of their control population. He noted that patients with epilepsy had higher prevalence of sleep-maintenance insomnia symptoms (52% vs. 38%). Using the Epworth Sleepiness Scale (ESS), Malow and colleagues (9) reported that 28% of 158 adult epilepsy patients surveyed had an elevated score (>10 points), with 44% of subjects reporting a moderate or high tendency to fall asleep while watching television. However, Manni et al. (10) found that only 11% of patients with epilepsy and 10% of controls had an ESS score of >10 (10). Increase in complaints of excessive daytime sleepiness (EDS) is also seen in children with epilepsy. Using the Pediatric Daytime Sleepiness Scale, Maganti et al. (11) showed that children with epilepsy have a higher prevalence of EDS. This increase in sleep complaints in patients with epilepsy may be related to the disruption of the central nervous system (CNS) involved in the regulation of sleep and the abilities of these individuals to perceive sleep—wake-related symptoms. The combination of these factors raises the question of potential dysfunction in sleep physiology or the perception of the sleep and awake states.

Information regarding sleep physiology can be gleaned from review of polysomnography (PSG). Sleep architecture is frequently disrupted in patients with epilepsy. Touchon et al. (12) showed that patients with epilepsy have greater sleep fragmentation and “instability.” PSG investigation of individuals with epilepsy by Malow et al. (13) showed that nearly one-third of patients with medically refractory epilepsy had a respiratory disturbance index (RDI) of >5 and approximately 10% of the patients had periodic limb movement index (PLMI) of >20 events per hour. In our own cohort of 25 patients with intractable epilepsy, we found that 36% had an RDI of >10 and approximately 12% had a PLMI of >15 events per hour. These studies involve relatively small numbers of patients and include a high percentage of patients continuing to have seizures despite medications.

Obstructive sleep apnea (OSA) may also influence the prevalence of epilepsy. Seizures as a direct result of apnea are rare. In one patient, an apnea in sleep reportedly caused a seizure after severe oxygen desaturation and cardiac arrest (14). Yet, Sonka et al. (15) found in their cohort that 4% of patients with OSA had epilepsy. This prevalence exceeds that in the general population. Over three-fourths of these patients had seizures only during sleep, and most of the events were generalized seizures. Although this study may be skewed by variances in referral patterns, the elevated prevalence raises the interesting question of sleep apnea provoking seizures or unmasking an underlying potential for seizures.

Nocturnal events may be relatively common. More than 3% of adults and 10% to 30% of children have nocturnal events on a routine basis. The prevalence of parasomnias in patients with epilepsy is not well known. Khatami et al. (8) found in their survey that the prevalence of parasomnia symptoms in patients with epilepsy was no greater than that in their control group. These events can be divided into nocturnal seizures and nonepileptic events. Gower found 21% of the institutionalized epilepsy patients to have seizures strictly while asleep and 42% to have seizures strictly while awake (3). These results are similar to Janz’s and Billiards studies of patients with epilepsy one century later (4,5,16). Nonepileptic nocturnal events are more common. Approximately 30% of children have disorders of arousal, such as sleepwalking or sleep terror events, and the reported prevalence in adults ranges from 2% to 5% (17,18). The prevalence of rapid eye movement (REM) sleep-related parasomnias, such as REM sleep behavior disorder (RBD), is unknown but appears to increase with age (19).