What is the benefit of hypoglossal nerve stimulation (HNS) therapy in treating obstructive sleep apnea (OSA) when retropalatal obstruction is a common site of upper airway collapse?

Benefits of Hypoglossal Nerve Stimulation Therapy for Obstructive Sleep Apnea with Retropalatal Obstruction

Hypoglossal nerve stimulation (HNS) therapy provides significant benefits for patients with moderate-to-severe obstructive sleep apnea (OSA) who cannot tolerate CPAP, even when retropalatal obstruction is present, as long as there is no complete concentric collapse at the soft palate level. 1

Patient Selection Criteria for HNS Therapy

• HNS is recommended for patients with moderate-to-severe OSA (AHI 15-65 events/hour) who have failed or cannot tolerate CPAP therapy 1
• BMI requirements vary by guideline but generally should be <40 kg/m² according to American guidelines and <32 kg/m² according to VA/DoD guidelines 1
• Drug-induced sleep endoscopy (DISE) is essential to confirm appropriate anatomical candidacy, specifically the absence of complete concentric collapse at the soft palate level 1
• Despite retropalatal obstruction being common, HNS can still be effective as long as there is not complete concentric collapse at this level 1, 2

Mechanism of Action and Benefits

• HNS works via direct neurostimulation of the hypoglossal nerve in synchrony with respiration, causing tongue stiffening and protrusion to open the airway 3
• This mechanism helps overcome retropalatal obstruction by:
  • Increasing tension in the palatoglossal muscles, which indirectly improves retropalatal airway patency 2
  • Creating greater negative pressure tolerance in the upper airway 4
  • Providing multilevel airway improvement despite primarily targeting the retroglossal space 2

Clinical Outcomes

• HNS therapy significantly reduces the apnea-hypopnea index (AHI) from baseline values, with studies showing reductions from approximately 35 to 8.5 events per hour 5
• Oxygen nadir levels trend upward following HNS implementation 5
• Subjective daytime sleepiness improves significantly as measured by Epworth Sleepiness Scale scores 5, 2
• Patient adherence to HNS therapy is superior to CPAP, with average usage of 7-8 hours per night 5, 2

Treatment Algorithm for OSA

• CPAP remains the first-line therapy for OSA according to the American Thoracic Society and European Respiratory Society 1, 6
• For CPAP-intolerant patients with moderate-to-severe OSA:
  • HNS should be considered if BMI <40 kg/m² and AHI 15-65/hour, and appropriate anatomical features are confirmed by DISE 1
  • Mandibular advancement devices are more appropriate for mild-to-moderate OSA but less effective for severe OSA 1
  • Multilevel surgery should be considered a salvage procedure with less predictable results 1

Implementation Considerations

• The implantation center holds primary responsibility among the interdisciplinary sleep team and serves as the primary contact for patients with problems 4
• HNS can be safely used in patients with cardiac implantable electronic devices (CIEDs) when implanted on the opposite side and with appropriate programming 7
• Three HNS systems are available (in Germany), with differences in technical details but similar underlying principles 4
• Unilateral HNS with respiratory sensing requires sleep endoscopy for indication, while continuous HNS without respiratory sensing does not 4

Potential Pitfalls

• Older European guidelines (2011) did not recommend neurostimulation due to limited evidence at that time, but more recent evidence supports its use 1
• Patient selection criteria must be strictly followed, especially regarding the absence of complete concentric collapse at the soft palate level, as this is a contraindication for HNS 1
• While retropalatal obstruction is common, complete concentric collapse at this level would make a patient ineligible for HNS therapy 1, 2