Hypoglossal Nerve Stimulation for Obstructive Sleep Apnea: Indications and Landmarks
For patients with OSA with an AHI of 15-65/h and a body mass index <32 kg/m2 who cannot adhere to CPAP, hypoglossal nerve stimulation (HNS) therapy is indicated as an alternative treatment option. 1
Primary Indications for HNS
HNS is indicated for patients who meet the following criteria:
- Moderate to severe obstructive sleep apnea (AHI 15-65 events/hour)
- BMI less than 32 kg/m2
- CPAP intolerance or failure
- No complete concentric palatal collapse 2
The Veterans Administration and Department of Defense clinical practice guidelines specifically recommend evaluation for HNS therapy in patients with an AHI of 15-65/h and BMI <32 kg/m2 who cannot adhere to PAP therapy (weak recommendation) 1. This recommendation is supported by evidence from clinical trials showing significant improvement in AHI from baseline in properly selected patients 2.
Patient Selection Factors
Proper patient selection is critical for successful outcomes with HNS:
Favorable anatomical factors:
- Absence of complete concentric palatal collapse
- BMI ≤32 kg/m2
- AHI ≤50 events/hour
CPAP failure defined as:
- Inability to use CPAP
- Intolerance to CPAP therapy
- Inadequate response to CPAP
Studies have shown that responders to HNS therapy had both a BMI ≤32 and AHI ≤50 and did not have complete concentric palatal collapse 2.
Major Anatomical Landmarks for HNS Placement
The surgical procedure for HNS involves three primary components:
Hypoglossal nerve electrode placement:
- Submandibular incision to identify the hypoglossal nerve
- Careful dissection to isolate the main trunk of the hypoglossal nerve
- Selective placement on branches that control tongue protrusion
Pulse generator placement:
- Right infraclavicular region
- Subcutaneous pocket creation
- Secured to underlying fascia
Respiratory sensing lead placement:
- Between internal and external intercostal muscles
- Typically at the right 4th or 5th intercostal space
- Positioned to detect respiratory effort
Efficacy and Outcomes
When properly selected, patients with HNS show:
- Significant reduction in AHI from baseline (38.9 ± 9.8 to 10.0 ± 11.0 at 6 months) 2
- Improvements in daytime sleepiness (ESS scores)
- Enhanced quality of life measures
- Superior adherence compared to CPAP therapy 3
Contraindications and Limitations
HNS is not recommended as a first-line treatment for OSA patients in general (conditional recommendation against) 1. The European Respiratory Society guidelines suggest HNS only for symptomatic OSA patients who have failed or not tolerated CPAP treatment 1.
Additional contraindications include:
- Central sleep apnea
- Pregnancy or intent to become pregnant
- Inability to operate the device
- Anatomical abnormalities preventing effective nerve stimulation
- Active implantable devices that might experience interference
Special Populations
Recent research suggests HNS may be effective in select patients with neuromuscular disorders 4 and cerebral palsy 5, showing improvements in AHI and oxygen saturation, though these applications require further study and are not part of standard indications.
Follow-up and Monitoring
After HNS implantation:
- Sleep study for titration of stimulation parameters
- Regular follow-up to ensure proper device function
- Monitoring for potential complications such as lead dislodgement
- Assessment of treatment efficacy with repeat sleep studies
HNS represents an important alternative for appropriately selected OSA patients who cannot tolerate CPAP therapy, with demonstrated efficacy in reducing sleep apnea severity and improving quality of life.