Hypoglossal Nerve Stimulation (HGNS) Therapy

What is hypoglossal nerve stimulation (HGNS) therapy?

Hypoglossal nerve stimulation (HGNS) 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. It is an advanced treatment for obstructive sleep apnoea (OSA), which is a condition where the muscles at the back of one’s throat relax too much during sleep, causing the airway to collapse. This leads to pauses in breathing, snoring, and poor sleep quality.

HGNS is a small, implantable device that works from inside the body to keep the airway open   unlike traditional therapies like continuous positive airway pressure (CPAP) that require the wearing of a mask.

How does hypoglossal nerve stimulation (HGNS) therapy work?

The device stimulates the hypoglossal nerve, which controls the muscles of the tongue by moving the tongue and palate forward to prevent it from blocking the airway.

On the day of surgery, the device components are implanted under general anaesthesia. The pulse generator is placed under the patient’s skin in the chest area, the breathing sensor near the ribs, and the stimulation lead is connected to the hypoglossal nerve in the neck.

Patients undergoing HGNS therapy turn on a remote before they go to sleep, with the device being programmed to start stimulation later (about 30 to 45 minutes later) to allow time for patients to fall asleep before the stimulation begins. 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.

Who is suitable for hypoglossal nerve stimulation (HGNS) therapy?

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

• Have not responded well to or cannot tolerate other therapies such as CPAP therapy and dental appliances.
• Are not significantly overweight (Body Mass Index, or BMI, typically under 32).
• Have undergone a sleep study to confirm OSA with an apnoea-hypopnea index (AHI) of 15 to 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 drug-induced sleep endoscopy (DISE) procedure to determine. 

HGNS is not suitable for patients with:

• Severe neuromuscular disorders
• Allergies to device materials
• Untreated, severe cardiac conditions 

A thorough evaluation with your sleep specialist will determine if you are a good candidate.

What are the benefits of hypoglossal nerve stimulation (HGNS) therapy?

• HGNS addresses the discomfort and compliance issues associated with CPAP.
• HGNS is the only form of treatment which addresses poor muscle tone that results in upper airway collapse.
• The ADHERE registry, a multicentre prospective observational study following outcomes of upper airway stimulation therapy, reported:
  • 83% of patients have had their sleep apnoea successfully treated with Hypoglossal nerve stimulation therapy (defined as a ≥ 50% reduction in AHI (sleep apnoea severity index) and post-treatment AHI of ≤ 20/hour).
  • 94% of patients are satisfied with the outcome and can use it consistently every night, with an average of 5.7 hours of therapy use per night.
  • Therapy response is durable with long-term data showing excellent therapeutic success rates of 75% sustained over five years.

What are the potential side effects of hypoglossal nerve stimulation (HGNS) therapy?

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

• Side effects caused by surgery:
  o Mild swelling, bruising, or tenderness; hypertrophic scar or keloid around the incision sites
  o Tongue and lip weakness
  o Temporary pain or stiffness in the neck, chest, or shoulder region
  o Risk of infection at the implant site (rare)
  o Pneumothorax
  o Complications related to anaesthesia (not common)
  
  
• Side effects caused by device:
  o Discomfort or a tugging/pulling sensation in the tongue or throat during stimulation, which often resolves as the body adjusts to the device
  o Rare cases of nerve irritation or sensitivity around the implant site
  o 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 them. Making appropriate adjustments can often improve comfort and functionality.

What can you expect during hypoglossal nerve stimulation (HGNS) therapy?

The HGNS device is implanted during a minimally invasive outpatient surgery, typically lasting two to three hours. The surgery is performed under general anaesthesia to ensure patients are comfortable throughout the procedure.

The key steps of the procedure include:

1. Pulse generator placement: A small, battery-powered pulse generator (about the size of a pacemaker) is implanted beneath the skin and tissues in the patient’s upper chest.
2. Breathing sensor insertion: A sensor is placed near the respiratory muscles to monitor the patient’s breathing patterns. It detects when the patient inhales 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 the tongue muscles.

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

How do you prepare for hypoglossal nerve stimulation (HGNS) therapy?

Before surgery, the patient will undergo a sleep study to confirm the severity of their OSA. A drug-induced sleep endoscopy (DISE), which is a day surgery procedure, is required to evaluate the upper airway anatomy to ensure that HGNS is the right treatment.

What can you expect after hypoglossal nerve stimulation (HGNS) therapy?

Recovery and healing
Generally, this surgery is not painful. Patients may experience mild discomfort at the incision sites, which is usually managed with over-the-counter pain medication such as paracetamol. They 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 four to six weeks after surgery. Their doctor will usually review the wound seven to 10 days after surgery.

Device activation and programming
About a month after the surgery, the device will usually be activated during a follow-up visit if the patient’s wound and recovery is optimal. The doctor will fine-tune the settings to match the patient’s breathing patterns. A handheld remote control will be given to the patient, which allows them to turn on the device before bed and turn it off when they wake up.

Ongoing monitoring
After activation, the doctor will monitor the patient’s progress over several months to ensure the device is working optimally. A repeat sleep study is usually done to fine-tune the device setting to allow for an optimal and comfortable setting which is therapeutic. Regular follow-ups are usually scheduled annually to check the device and adjust the settings if needed.