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Obstructive Sleep Apnea and Epilepsy
by Erica Tennenhouse
Obstructive sleep apnea (OSA) is a common sleep disorder in which obstruction of the airway during sleep hinders breathing. Periods of obstructed breathing are followed by sudden attempts to breathe, resulting in frequent arousals and fragmented sleep. According to recent studies, up to one third of adults with refractory epilepsy also have OSA, defined by having five or more apnea events per hour of sleep (1).
A study published in Neurology found that out of 39 candidates for epilepsy surgery with no previously documented history of OSA, 50% of male patients and 19% of female patients had OSA. This was a much higher prevalence of OSA compared to a previous population-based study in adults without epilepsy in which only 24% of men and 9% of women were found to have OSA. Manni and colleagues also screened patients with epilepsy for OSA and found that the subjects who had OSA tended to be taking more antiepileptic drugs (AEDs), were more likely to be male, had seizure onset at a later age, and were older and heavier than the patients without the sleep disorder (4).
It has been proposed that certain epilepsy therapies promote OSA. Anticonvulsants, such as barbiturates and benzodiazepines cause smooth muscle relaxation, which can affect muscle tone in the upper airway, making it more collapsible. As well, weight gain, which is an adverse side effect of some AEDs such as valproate, gabapentin, carbamazepine, pregabalin, and vigabatrin, can promote OSA (2). Vagus nerve stimulators may affect the muscle tone of the upper airway, or the brainstem networks that are involved in regulation of respiration during sleep.
Several studies have also documented that improvement of seizure control occurs when OSA is treated, which suggests that OSA may facilitate seizures. OSA causes breathing to stop briefly multiple times in a night, sometimes leading to low oxygen in the brain (cerebral hypoxemia), which is associated with seizures. Some studies have suggested that nocturnal seizures are more common in the lighter stages of sleep; OSA causes fragmentation of sleep, which means there is a greater incidence of transitory stages of light sleep in which seizures occur in people with OSA. Finally, OSA causes sleep deprivation, which is known to be a seizure trigger for some patients.
Since the effects of OSA may cause seizures, it would be a good idea for physicians to question epilepsy patients, and family members familiar with their sleep patterns, for a history of sleep disturbance (3). Identification and treatment of OSA in people with epilepsy is a new therapeutic possibility for approximately 30% of refractory cases.
Sources
1. Malow B. A., et al. Obstructive sleep apnea is common in medically refractory epilepsy patients. Neurology 55(2000): 1002-1007.
2. Foldvary-Schaefer, Nancy and Madeleine Grigg-Damberger. Sleep and Epilepsy: What We Know, Don't Know, and Need to Know. Journal of Clinical Neurophysiology. 23(2006): 4-20.
3. Vaughn, B. V. Improvement of epileptic seizure control with treatment of obstructive sleep apnea. Seizure. 5(1996): 73-8.
4. Manni R, et al. Obstructive sleep apnea in a clinical series of adult epilepsy patients: frequency and features of the comorbidity. Epilepsia. 44(2003): 836-840.
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