Potential causes of sleep disturbance in patients with epilepsy can be divided into three groups:
- effects of epilepsy on sleep
- effects of medication on sleep
- the presence of another sleep disorder
In addition to relieving daytime sleepiness, identifying and treating coexisting sleep disorders may also improve seizure control or allow the physician to increase a patient’s medication regimen to improve seizure control.
The physician who is faced with a patient with epilepsy who has sleep difficulty should begin by categorizing the complaint as either excessive daytime sleepiness, insomnia, or unusual events at night.
A detailed history should include information regarding the clinical course, the degree of impact on the patient, the sleep-wake pattern, the report from the bed partner, dietary and activity changes, medications (including over-the-counter agents), and medical conditions.
Prevalence of sleepiness
Using the Epworth Sleepiness Scale, a widely used, validated subjective measure of daytime sleepiness, Malow and colleagues reported that 28% of 158 adult epilepsy patients surveyed had an elevated score (higher than 10 points). Specifically, 44% of subjects reported a moderate or high tendency to fall asleep while watching television and 41% while sitting or reading.32
Daytime sleepiness in the epilepsy patient has a variety of causes, including:
- antiepileptic drugs (AEDs)
- insufficient sleep
- inadequate sleep hygiene
- obstructive sleep apnea
- upper airway resistance syndrome
- restless legs syndrome
- periodic limb movements in sleep disorder
- idiopathic hypersomnia
Patients with epilepsy and physicians often believe that AEDs are the cause of sleepiness. An Italian multicenter survey of 509 patients taking AEDs reported that somnolence was the most common complaint, experienced by 51 patients (10%).33However, 48 of these 51 patients were taking phenobarbital or primidone, usually in combination with at least one other AED.
It is important to consider other causes before attributing sleepiness to AEDs alone. Unrecognized nocturnal seizures, frequent sleep disruption caused by interictal epileptic discharges, and arousals from sleep are other important causes of sleepiness in the epilepsy patient, and treatment with increased doses of AEDs may improve sleepiness. Video-EEG polysomnography may be useful in evaluating such patients.34
Symptoms of drowsiness in a patient taking AEDs may also result from a coexisting sleep disorder. In a study of predictors of sleepiness in epilepsy patients, symptoms of obstructive sleep apnea or restless legs syndrome were more significant predictors of elevated scores on the Epworth Sleepiness Scale than the number or type of AEDs, seizure frequency, epilepsy syndrome, or the presence of sleep-related seizures.32
Although subjective sleepiness is a common side effect of AEDs, a wide variety of sleep disorders also occur in patients with epilepsy, including obstructive sleep apnea, restless legs syndrome, periodic limb movements in sleep, narcolepsy, andidiopathic hypersomnia. Treating these sleep disorders may improve not only daytime sleepiness and quality of life, but also seizure control. A dose-limiting effect of AEDs is sedation, but with the improvement of a coexisting sleep disorder, the physician may be able to control the seizure disorder with increased medication dosage.
In addition, seizure control may improve even without increasing AED doses. Several case series of coexisting sleep apnea and epilepsy have described improvement in seizure frequency with treatment of sleep apnea.60–63 The mechanisms whereby treatment of a sleep disorder improves a seizure disorder are unknown. Resolution of chronic sleep deprivation, improvement in cerebral hypoxemia, and reduction in arousals from sleep have been postulated.
In patients with coexisting restless legs syndrome or periodic limb movements of sleep, choosing an AED that treats the coexisting sleep disorder may be useful. Such choices include gabapentin and clonazepam. Clonazepam is also useful in treating REM sleep behavior disorder in association with seizures.
When epilepsy coexists with a sleep disorder known to cause excessive daytime sleepiness (e.g., narcolepsy) or when AEDs are the suspected cause of daytime sleepiness, removing sedating AEDs from a patient’s regimen may be helpful. Such agents include barbiturates and benzodiazepines. Some newer AEDs may be less likely to cause sedation than older AEDs. In one double-blind comparison study, carbamazepine and lamotrigine were equally effective in controlling seizures, but sleepiness was significantly less common in patients taking lamotrigine.64
Another approach is to prescribe AEDs that tend to produce insomnia to patients troubled by daytime sleepiness. Although felbamate use has been limited by its adverse hematologic and hepatic effects, it is potentially useful for patients with extreme daytime sleepiness. In one study, 9 of 10 epilepsy patients with hypersomnolence treated with felbamate had a marked and sustained improvement in daytime wakefulness and alertness.65
Other measures for reducing daytime sleepiness in the epilepsy patient include simplifying the AED regimen to avoid polytherapy, prescribing AEDs so that the largest dose is given at night, and using extended-release preparations.