Introduction

Hypoglossal nerve stimulation (HNS) is a novel therapy for obstructive sleep apnea (OSA) that has demonstrated efficacy in adults [ ]; this device has been proposed as a potentially effective therapy in pediatric patients with Down Syndrome (DS) due to their hypotonia and relative macroglossia. A recent clinical trial of twenty pediatric patients with DS confirmed HNS safety and efficacy in a research population [ ].

Here we describe a pediatric patient with DS and OSA who was successfully implanted with HNS outside of a clinical trial and was assessed using a wrist-based home sleep apnea test (HSAT) device [ ]. This case report meets exemption criteria for the Vanderbilt University Institutional Review Board.

Case presentation

A 13-year-old male with a history of DS, limited verbal output, and history of ventricular septal defect repair presented to the pediatric otolaryngology clinic with severe refractory OSA after prior adenotonsillectomy, lingual tonsillectomy, and supraglottoplasty. He was unable to tolerate continuous positive airway pressure (CPAP) therapy despite extensive trials. Daytime symptoms included excessive daytime sleepiness, attention difficulties, and irritability. He slept upright during the night to minimize airway obstruction.

His body-mass index was 24.02 (92nd percentile, overweight category). Preoperative polysomnography (PSG) demonstrated an apnea-hypopnea index (AHI) of 44.9 events/h with a central apnea index (CAI) of 29.9 events/h. Preoperative drug-induced sleep endoscopy revealed substantial tongue base collapse without circumferential collapse of the soft palate. The patient underwent HNS (Inspire II; Inspire Medical Systems, Inc.) implantation using a three-incision approach without complication. He was discharged on postoperative day 1, tolerating an oral diet with pain control achieved using acetaminophen and ibuprofen.

HNS therapy was activated in the clinic one month after surgery. His caregivers observed significant improvements in snoring, daytime sleepiness, behavioral problems, and supine sleeping. PSG was attempted at two months postoperatively, but the patient was agitated by the lab environment and displayed poor sleep efficiency (54%) without rapid eye movement (REM) sleep. His AHI during this study at 1.6 V was 18.8 events/h, with a CAI of 3.6 and a minimum oxygen saturation of 89%.

A wrist-based HSAT (WatchPAT; Itamar Medical Ltd.) was obtained eight months after surgery to minimize sensory disruptions. He achieved an improved sleep efficiency of 65.6% with 13.2% of sleep spent in REM. His total AHI was 12.2 events/h with a minimum oxygen saturation of 90% using HNS at 1.9 V. The snoring sensor was dislodged during the HSAT, preventing differentiation of obstructive and central apneas. At his last postoperative visit, the patient was using therapy an average of 10.5 hours/night at 2.0 V. The family reported excellent HNS tolerance with improvements in daytime wakefulness and behavior.

Discussion

This case report documents successful implantation of an HNS system in a pediatric patient with DS and OSA with assessment of therapy efficacy using HSAT. Several unique observations can be made from our experience. First, HNS implantation in a pediatric patient outside of a clinical trial was effective in reducing OSA burden and has been well tolerated since placement. Second, this patient experienced a substantial OSA burden reduction with HNS despite an elevated preoperative CAI. Obstructive events during sleep cause elevations in CO _2, creating a temporary cessation of respiratory drive due to ventilatory control instability that may result in central apnea events. Thus, a reduction of obstructive disease may reduce CO ₂ perturbations with additional improvement central apnea indices, as observed in our patient [ ].

Lastly, we successfully assessed HNS efficacy with a wrist-based HSAT system utilizing peripheral arterial tomography. HNS response is usually measured using laboratory-based PSG, but our patient had poor sleep efficiency and a complete lack of REM sleep due to sensitivity to the laboratory environment. The wrist-based HSAT device is clinically validated with an 89% correlation to PSG [ ], and was well-tolerated by our patient. His sleep efficiency was improved from the in-lab PSG, and REM sleep was obtained. HSAT represents an alternative to in-lab PSG for HNS assessment in patients with DS who are more sensitive to laboratory environments.

Conclusion

This report highlights the clinical efficacy of HNS therapy in a patient with DS and OSA, which was confirmed with a home sleep apnea test. Further studies will help develop and refine best practices for this procedure and subsequent assessment.

Author contributions

Kay, Hannah G Kay, BA: conceptualization/design, investigation, formal analysis, writing (drafting, editing), final approval of the version to be published.

David T Kent, David T Kent, MD: conceptualization/design, methodology, investigation, data curation, formal analysis, editing manuscript, final approval of the version to be published.

James D Phillips, MD: conceptualization/design, methodology, investigation, data curation, formal analysis, editing manuscript, final approval of the version to be published.