Hypoglossal Nerve Stimulation (HGNS) for Obstructive Sleep Apnea

What is Hypoglossal Nerve Stimulation?

Hypoglossal Nerve Stimulation (HGNS) is an innovative, FDA-approved, surgical treatment for patients with moderate to severe obstructive sleep apnea (OSA). It is specifically designed for people who cannot tolerate or do not get consistent benefit from traditional treatments, most notably Continuous Positive Airway Pressure (CPAP) therapy.

While CPAP uses air pressure from a mask to push the airway open from the outside, HGNS works entirely inside the body. Think of it as a “pacemaker for your tongue.”

The Problem: Airway Collapse

In people with OSA, the muscles in the throat and the tongue relax too much during sleep. The tongue falls backward, completely or partially blocking the airway. This stops breathing, lowers oxygen levels, and forces the brain to wake up briefly to take a breath, preventing restful, restorative sleep.

The Solution: Targeted Stimulation

The goal of HGNS therapy is to keep the airway open during sleep. It achieves this by delivering mild, gentle electrical stimulation to the hypoglossal nerve—the specific nerve that controls the movement of your tongue. This stimulation causes the tongue muscle to contract slightly and move forward, pulling it out of the airway and allowing for smooth, unobstructed breathing throughout the night.

How Hypoglossal Nerve Stimulation Works

The general process of HGNS therapy involves three main stages:

1. The Components (Generic)

A generic HGNS system is made up of two primary elements:

The Implanted Stimulator: This is a small device, placed under the skin during surgery. It is a miniature computer and power source (like a cardiac pacemaker).
The Electrode: A tiny cuff, connected to the stimulator by a thin wire (lead). It is carefully wrapped around a branch of the hypoglossal nerve, near where it enters the tongue muscle.

2. The Surgical Procedure

Minimally Invasive: The implantation is a straightforward outpatient surgical procedure performed under general anesthesia. It typically takes 1.5 to 3 hours.
Incisions: The surgeon makes small incisions to place the components (most commonly, one under the chin to access the nerve and one in the upper chest or neck for the stimulator).
Recovery: Most patients can go home the same day as the surgery. Over-the-counter pain medication is usually sufficient for any postoperative discomfort. Full recovery typically takes a few weeks.

3. Therapy in Action

Healing Period: The device is not turned on immediately. You will have a healing period of about 4 weeks to allow the surgical sites to heal.
Activation and Titration: At a follow-up appointment, your sleep specialist will activate the device and begin to adjust (“titrate”) the stimulation settings. The goal is to find the lowest level of stimulation that effectively moves your tongue forward without waking you up.
Patient Control: Once the device is activated, you are in control. Every night before bed, you use a small, handheld remote to turn the therapy on. When you wake up in the morning, you turn it off. The system includes a programmable delay, which allows you to fall asleep comfortably before the stimulation begins.

Compare & Contrast: Inspire vs. Genio

While all HGNS devices share the same fundamental goal of moving the tongue forward, different brands have different designs, surgical procedures, and operational methods. The two most prominent HGNS systems are Inspire (by Inspire Medical Systems) and Genio (by Nyxoah).

Core Concept (Shared)

Mechanism: Both use an implanted electrode to stimulate the hypoglossal nerve, causing forward tongue movement and an open airway.
Patient Control: Both allow the patient to turn the therapy on and off daily using a handheld controller.

Compare and Contrast: System Architecture

The most significant differences lie in where components are implanted, how they sense breathing, and how they are powered.

Inspire Upper Airway Stimulation

The Inspire system is a closed-loop, synchronized system. This means it works in direct coordination with your body’s natural breathing.

System Components: A three-part, fully implanted system:
1. Stimulator (Pulse Generator): A small device containing the battery, placed in a “pocket” under the skin in the upper chest, similar to a cardiac pacemaker.
2. Breathing Sensor: A tiny sensor lead, connected to the stimulator. It is placed between your ribs to detect your chest’s natural expansion and contraction, sensing precisely when you are about to inhale.
3. Stimulation Lead: The wire connected to the stimulator that wraps around the hypoglossal nerve.
Operation: The system senses your natural breathing pattern. Only when it detects that you are inhaling does it deliver a pulse to the nerve, moving the tongue forward to coincide with your breath. This creates a natural, gentle open-airway sensation.
Power Source: The battery is sealed inside the implanted stimulator.

Genio Hypoglossal Nerve Stimulation

The Genio system is a leadless, asynchronized system, offering a different surgical approach and operational mode.

System Components: A two-part system:
1. Implanted Stimulator: A single, compact device that contains both the stimulator computer and the electrode, combining them into one unit. This entire component is placed through a single incision under the chin. There are no separate wires (leads).
2. Activation Chip: A small, external component that powers and controls the implant. It contains a battery and is attached to a disposable adhesive patch.
Operation: The system does not have a breathing sensor. It is “asynchronized.” Every night, you place the Activation Chip onto the adhesive patch on your chin. Once activated, the external chip provides power and instructions to the implant, which delivers a programmed pattern of stimulation throughout the night (for example, small, frequent pulses) rather than triggering only during inhalation.
Power Source: The main battery is outside the body, in the Activation Chip. The implant itself has no battery and is powered wirelessly by the external chip.

Compare and Contrast

Feature	Inspire	Genio
System Architecture	Closed-Loop / Synchronized	Asynchronized
Operation Mode	Stimulates only when inhaling, sensing your unique breathing rhythm.	Delivers continuous, programmed pulses; does not sense breathing.
Components	Fully Implanted (Internal): Stimulator, Breathing Sensor, Stimulation Lead	Dual-Component (Internal + External): Implanted Stimulator (leadless), External Activation Chip & Patch
Implantation Site(s)	Multilevel: Chest (stimulator & sensor), Neck (nerve)	Single-Site: Neck (under chin) for the leadless implant.
Number of Incisions	Typically Two: One under the chin, one in the chest. (Some require a third under the ribcage).	One: Single incision under the chin.
Battery Location	Internal: Rechargable battery inside the implanted chest device.	External: Disposable, rechargable battery in the Activation Chip worn on the chin.
Device Life & Replacement	The entire chest device must be surgically replaced when the battery dies (approx. 10+ years).	The implant has no battery, so no battery-replacement surgery is needed. The Activation Chip is external and rechargable.
Postoperative Lifestyle	Nothing to wear on the skin. You manage therapy with a small remote control.	You must wear an Activation Chip and adhesive patch on your chin every night.
MRI Safety	Full-body MRI (1.5 Tesla and 3 Tesla) conditional compatibility.	Full-body MRI conditional compatibility.

Conclusion: The Importance of Personal Consultation

Both Inspire and Genio offer robust, effective alternatives to CPAP for managing OSA. The choice between them depends on a variety of personal factors:

Your unique anatomy: A surgeon must evaluate the shape and movement of your airway during a Drug-Induced Sleep Endoscopy (DISE) to confirm that a nerve stimulator will be effective and determine which system may work best.
Your lifestyle and preferences: Do you prefer a fully internal system with a single device that needs no external equipment, or do you find the idea of an external component with a leadless implant more appealing?
Surgical considerations: Your overall health, specific anatomy, and comfort with a two-site vs. a one-site procedure.
Titration needs: Some patients respond better to a synchronized system (Inspire), while others do well with an asynchronized approach (Genio).

Our team at Pulmonary and Sleep Consultants has expertise in hypoglossal nerve stimulators and will guide you through a complete evaluation. We will help you weigh the pros and cons of each system and choose the optimal therapy to meet your clinical needs and personal preferences, ultimately helping you find the path to restful, healthy sleep.