Abstract
Introduction
Vagal Nerve Stimulators (VNS) are used in refractory epilepsy and depression. VNS are known to decrease airflow, oxygen saturation, and respiratory amplitude during sleep. We present a case of VNS induced OSA that was overlooked for 6 years.
Report of case(s)
A 63-year-old Caucasian female with refractory depression, hypothyroidism, and obesity presented with snoring and excessive daytime sleepiness (EDS). She had VNS implanted in a research trial for depression. She was on bupropion, duloxetine, lithium carbonate, lamotrigine, olanzapine, and levothyroxine. Polysomnography (PSG) showed moderate OSA with apnea-hypopnea index (AHI) of 25.8 and SpO2 nadir of 83%, and was titrated to bi-level positive airway pressure (PAP). She tried different masks and pressures but her leak and PAP intolerance persisted. There was no improvement in her EDS, and Armodafinil was prescribed for wake promotion. She struggled with bi-level PAP therapy for five years before being considered for hypoglossal nerve stimulator. But was turned down because of VNS presence. She was then recommended maxillomandibular advancement (MMA) but decided against it. She continued PAP therapy until a repeat PSG revealed mild to moderate OSA (AHI 10.9, RDI 17.8, and SpO2 nadir 79%), and it was noted that most of her respiratory events appeared in a regular fashion at 300-second intervals corresponding with the firing of VNS. PSG performed with VNS turned off showed no OSA (AHI 0.8 and SpO2 nadir 85%). PAP therapy was discontinued and subsequent nocturnal pulse oximetry showed normal oxygenation (ODI 15, RDI 17.8, SpO2 <88% for only 1.7 minutes). Her EDS resolved and VNS was eventually removed as per patient’s preference. She was started on a new medical therapy for depression. She continues to be asymptomatic.
Conclusion
Ascertainment bias led to delay in recognition of the cause of OSA as focus was on treatment only. Lowering the VNS frequency, increasing cycle time, turning it off during sleep or removal can improve respiratory events. The decision to do so depends on perceived benefit and harm of continuing VNS therapy. This case highlights the importance of re-evaluation of causes and treatment strategies when the standard of care is ineffective.
Support (if any):
High-dose spaced theta-burst TMS as a rapid-acting antidepressant in highly refractory depression
