Hypoglossal Nerve Stimulation (HGNS) Therapy

Hypoglossal Nerve Stimulation (HGNS) is an advanced treatment for Obstructive Sleep Apnea (OSA), which comprises a surgically implanted device that sends signals to the nerve of the tongue (hypoglossal nerve), to prevent the tongue and palate from blocking the upper airway during sleep. OSA is a condition where the muscles at the back of your throat relax too much during sleep, causing your airway to collapse. This leads to pauses in breathing, snoring, and poor sleep quality. Unlike traditional therapies like Continuous Positive Airway Pressure (CPAP) that require wearing a mask, HGNS is a small, implantable device that works from inside your body to keep your airway open.

This therapy can be considered for patients with moderate to severe OSA - in particular, patients who have struggled with other treatments such as CPAP therapy, dental appliances, or others. This therapy comprises a surgically implanted device that monitors breathing patterns and provides electrical stimulation/signals to the tongue nerve. This tongue nerve stimulation moves the tongue forward and keeps the airway open.

To learn more about HGNS therapy, watch: Hypoglossal Nerve Stimulation (HGNS) for Sleep Apnea - Things to know

How does HGNS Therapy work?

The device stimulates the hypoglossal nerve, which controls the muscles of your tongue, moving your tongue and palate forward to prevent it from blocking your airway. Patients undergoing HGNS Therapy turn on a remote before they go to sleep, with the device being programmed to start stimulation later (about 30 - 45 mins later) to allow time for patients to fall asleep before starting the stimulation. The device can also be paused and restarted if the patient needs to wake up in the middle of the night. HGNS works automatically, adjusting to the patient’s breathing patterns, allowing for uninterrupted, restful sleep without external equipment like masks or hoses.

Example of remote control for HGNS Therapy: Allows patients to turn on the device when going to bed, or pause and start therapy when they go to the toilet

Real-World Success Data

HGNS has been shown to be a highly effective treatment for moderate to severe OSA. Clinical trials and ongoing studies¹ reveal significant benefits, including:

• Sustained Reduction in Apnoea Episodes: Studies show that patients undergoing HGNS show significant reduction in apnoea episodes, sustained even up to five years after surgery
• Improved Sleep Quality: Most patients report noticeable improvements in sleep quality and less daytime tiredness, leading to more energy, better focus, and an overall better quality of life.
• Long-Term Effectiveness: Patients who use HGNS for several years continue to experience significant improvements in their condition.

In patient satisfaction surveys², over 85% of users are happy with the results and would recommend the treatment to others. This therapy has been particularly beneficial for individuals who cannot tolerate CPAP therapy.

Undergoing the Surgery

1. Undergoing the Surgery Pre-surgical Evaluation: Before surgery, you’ll undergo a sleep study to confirm the severity of your OSA. You will also need a drug-induced sleep endoscopy (DISE) which is a day surgery procedure to evaluate your upper airway anatomy to ensure that HGNS is the right treatment for you. 
2. Surgical Procedure: On the day of surgery, under general anaesthesia, the device components are implanted. The pulse generator is placed under your skin in the chest area, the breathing sensor near your ribs, and the stimulation lead is connected to the hypoglossal nerve in your neck.
3. Recovery and Healing: Generally, this surgery is not painful. You may experience mild discomfort at the incision sites, which is usually managed with over-the-counter pain medication such as paracetamol. You will be advised to avoid large movements or any strenuous exercises on the side of the implant (usually the right arm, right chest) for about 4-6 weeks after surgery. Your doctor will usually review your wound 7-10 days after surgery. 
4. Device Activation and Programming: About a month after the surgery, the device will usually be activated during a follow-up visit if your wound and recovery is optimal. Your doctor will fine-tune the settings to match your breathing patterns. You’ll receive a handheld remote control that allows you to turn the device on before bed and off when you wake up. 
5. Ongoing Monitoring: After activation, your doctor will monitor your progress over several months to ensure the device is working optimally. A repeat sleep study is usually done to fine-tune your device setting to allow for an optimal, comfortable setting which is therapeutic. Regular follow-ups are usually scheduled annually to check the device and adjust the settings if needed.

How is the HGNS Device Implemented?

The HGNS device is implanted during a minimally invasive outpatient surgery, typically lasting 2 to 3 hours. The surgery is performed under general anaesthesia to ensure patients are comfortable throughout the procedure. Here are the key steps of the procedure:

1. Pulse Generator Placement: A small, battery-powered pulse generator (about the size of a pacemaker), is implanted beneath the skin and tissues in your upper chest.
2. Breathing Sensor Insertion: A sensor is placed near your respiratory muscles to monitor your breathing patterns. It detects when you inhale and signals the pulse generator when stimulation is needed.
3. Stimulation Lead Connection: A thin wire, or lead, is tunnelled under the skin and connected to the hypoglossal nerve. When activated, the device sends gentle electrical impulses to this nerve, which controls your tongue muscles.

After surgery, patients are typically discharged the same day or after a short hospital stay, depending on your doctor’s recommendation.

Pulse Generator Placement

Possible Side Effects of Surgery and the Device

While HGNS is considered safe with overall risks less than 1% based on published data, there are some potential risks and side effects associated with the surgery and the device itself.

• Surgical Side Effects:
  • Mild swelling, bruising, or tenderness, hypertrophic scar or keloid around the incision sites
  • Tongue and lip weakness 
  • Temporary pain or stiffness in the neck, chest, or shoulder region
  • Risk of infection at the implant site(rare)
  • Pneumothorax
  • Complications related to anaesthesia (not common) 
• Device Side Effects:
  • Discomfort or a tugging/pulling sensation in the tongue or throat during stimulation, which often resolves as your body adjusts to the device
  • Rare cases of nerve irritation or sensitivity around the implant site
  • Device malfunction, though uncommon, may require reprogramming or adjustment

Your healthcare team will go through the side effects and complications of this surgery in more detail and guide you through it. Making appropriate adjustments can often improve your comfort and functionality.

Who is a Candidate for HGNS?

HGNS Implant therapy is generally recommended for adults with moderate to severe OSA who:

• Have not responded well to or cannot tolerate CPAP therapy.
• Are not significantly overweight (Body Mass Index, or BMI, typically under 32).
• Have undergone a sleep study to confirm OSA with apnoea hypopnea index of 15–65 and with no central apnoea.
• Have appropriate anatomy for the procedure (the airway can be effectively treated by moving the tongue forward). This will require a DISE procedure to determine.

HGNS is not suitable for patients with severe neuromuscular disorders, allergies to device materials, or those with untreated, severe cardiac conditions. A thorough evaluation with your sleep specialist will determine if you are a good candidate.

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By understanding HGNS and its benefits, risks, and the procedure, you can make an informed decision. Speak with your doctor if you think HGNS could be the right solution to help you regain restful sleep and improve your quality of life.

‌The Department of Otorhinolaryngology – Head & Neck Surgery at Sengkang General Hospital provides a wide range of specialist services focusing on a wide range of ear, nose, throat, sleep apnoea, and head and neck cancer conditions.

The Sleep Medicine Unit at Sengkang General Hospital is a multidisciplinary sleep team helmed by Ear, Nose and Throat (ENT) surgeons, respiratory physicians, orthodontists, psychiatrists, psychologists and sleep technologists specialising in the diagnosis and management of a wide range of sleep disorders like obstructive sleep apnoea, snoring, insomnia, obesity hypoventilation syndrome, circadian rhythm sleep disorders, narcolepsy, parasomnias, and other sleep related movement disorders.

For appointments, contact us at 6930 6000 or email us at appointments@skh.com.sg.

¹ Strollo, P. J., Soose, R. J., Maurer, J. T., de Vries, N., Cornelius, J., Froymovich, O., Hanson, R. D., Padhya, T. A., Steward, D. L., Gillespie, M. B., Woodson, B. T., Van de Heyning, P. H., Goetting, M. G., Vanderveken, O. M., Feldman, N., Knaack, L., Strohl, K. P., & STAR Trial Group. (2014). Upper-airway stimulation for obstructive sleep apnea. The New England Journal of Medicine, 370(2), 139–149. https://doi.org/10.1056/NEJMoa1308659
² Thaler, E., Schwab, R., Maurer, J., Soose, R., Larsen, C., Stevens, S., Stevens, D., Boon, M., Huntley, C., Doghramji, K., Waters, T., Kominsky, A., Steffen, A., Kezirian, E., Benedikt Hofauer, Sommer, U., Withrow, K., Strohl, K., & Heiser, C. (2019). Results of the ADHERE upper airway stimulation registry and predictors of therapy efficacy. The Laryngoscope, 130(5), 1333–1338. https://doi.org/10.1002/lary.28286