VNS associated OSA is an underrecognized side effect of VNS therapy. Case reports demonstrate mild to severe OSA with incomplete resolution from standard therapies. Recently VNS associated OSA has shown improvement with VNS setting adjustment but the effect on seizure frequency is not fully understood.

D.C., a 28 y.o. woman with intractable epilepsy s/p VNS placement, was referred to sleep medicine with snoring and daytime sleepiness. The sleep study showed an unusual metronomic pattern of OSA occurring at 5 minute and 30 second intervals not resolving with CPAP. D.C's neurologist confirmed the timing correlated with the VNS duty cycle, consistent with VNS associated OSA.

An in-lab VNS titration sleep study was performed under the monitoring of a physician with training in both epilepsy and sleep medicine. The physician performed interval decreases in the VNS output current and observed clinical and polysomnography changes throughout the titration. 

After several reductions of the output current the apneas and hypopneas completely resolved and the sleep study normalized for the remainder of the night. Sleep symptoms also resolved after this study. Paradoxically there was improvement in seizure frequency despite reduced VNS settings. At baseline the patient had biweekly seizures, more frequently out of sleep, but three months following titration reported no additional seizures. 

VNS titration can treat VNS-induced OSA and decrease seizure frequency. Some authors postulate a risk of increased seizures with VNS setting reduction, while others believe that treatment of OSA may decrease seizure frequency. This case implies that a subset of patients may benefit from VNS reduction and concerns for worsening seizure frequency may be overstated. The exact nature and best practices of VNS settings reduction for VNS associated OSA remains unknown.