Vagus nerve stimulation, sleep apnea, and CPAP titration

Epilepsy and obstructive sleep apnea (OSA) are two relatively common disorders known to coexist and potentially exacerbate each other. Vagus nerve stimulation (VNS) is a currently used, adjunctive treatment for partial epilepsy and is generally well tolerated with few associated side effects. Some of the more common side effects include hoarseness of voice, laryngeal irritation and cough, especially after VNS current increases and the first few weeks of treatment. VNS therapy also affects respiration during sleep and has been shown to worsen preexisting obstructive sleep apnea/hypopnea syndrome (OSAHS) by increasing the number of apneas and hypopneas. Consistent sleep related decreases in airflow and effort coinciding with VNS activation have been documented, with apneas and hypopneas found to be more frequent during VNS activation than during nonactivation. VNS may also interfere with effective CPAP titration. The purpose of this case study was to examine the effects of VNS cycling on CPAP titration for OSA in a patient with medically intractable epilepsy. We found that adequate CPAP titration could not be achieved in the presence of the patient's standard VNS on/off cycling mode. However, when the patient was restudied with his VNS device turned off, a nasal CPAP pressure of 13 cm H2O resulted in effective treatment of his severe OSAHS. We suggest that polysomnography before VNS implantation should be considered in order to identify patients with OSA.