Effect of Treatment of Sleep Apnea on Epilepsy

Several researchers have demonstrated the effect of treating OSA on seizure frequency in patients with epilepsy. In one of the earlier studies, Devinsky et al. (11) showed a clear reduction in seizure frequency in four out of five patients with refractory partial epilepsy and sleep apnea, following treatment of sleep apnea with continuous positive airway pressure (CPAP). Vaughn et al. (22) evaluated response to treatment of sleep apnea in 10 patients with seizures and sleep apnea. Eight patients received CPAP and two patients were treated with positional therapy. Three patients became seizure free, and the others also showed a significant reduction in seizure frequency with treatment of sleep apnea. Malow et al. (23) selected 13 adults and five children from a clinic population based on seizure frequency and risk for OSA. Six out of 13 adults and three out of five children with epilepsy met PSG criteria for OSA. Of these, three adults and one child were treated with CPAP and all four reported at least a 45% reduction in seizure frequency during CPAP treatment.

Choice of anticonvulsant medication must also be taken into account as central nervous system (CNS) suppressants can aggravate breathing difficulty in sleep in a pre-existing or latent OSA. Antiepileptic drugs can promote weight gain (24) or affect upper respiratory airway tone (25). Vagal nerve stimulation (VNS) therapy for refractory epilepsy can cause dyspnoea, which is a well-recognized side effect. However, it is also documented to have an effect on respiration during sleep (26-28). Marzec et al. (28) did a baseline PSG followed by another PSG three months after VNS placement in 16 epilepsy patients. An apnea-hypopnea index (AHI) > 5 was reported in 1/16 at baseline and in 5/16 at three months following VNS treatment initiation. One patient with esophageal pressure monitoring showed crescendos in esophageal pressure during VNS activation, supporting an obstructive pattern. A patient with CPAP trial showed resolution in respiratory events with CPAP. Thus, anticonvulsant and VNS therapies can potentially worsen underlying sleep apnea in patients with epilepsy.

In cases selected for epilepsy surgery, it may be beneficial to evaluate for OSA preoperatively. It has been seen that the perioperative complication rate is higher in patients with coexistent OSA (29). With appropriate and adequate treatment of coexistent OSA, patients may either become seizure free or have significantly reduced seizure frequency. Thus all candidates for epilepsy surgery or refractory seizures should have a formal sleep evaluation and an overnight PSG performed. Also, seizures and interictal epileptiform discharges are generally suppressed during REM sleep while OSA has greatest respiratory disturbance during REM sleep. So, if a patient has a persistent tendency to REM-related seizures, a sleep evaluation may be helpful.

Sleep Apnea

Sleep Apnea

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