How Hypoglossal Nerve Stimulation Works for Sleep Apnea

Hypoglossal nerve stimulation treats obstructive sleep apnea by sending a mild signal to the nerve that controls the tongue. The signal makes the genioglossus muscle push the tongue forward, so it does not fall back and block the airway during sleep. It works only while it is turned on, which is why nightly use matters.

The genioglossus: the muscle that keeps your airway open

The genioglossus is one of the main muscles of the tongue. It runs from the inside of the chin into the tongue. When it tightens, it pulls the tongue forward and away from the back of the throat.

The hypoglossal nerve carries the signals that move this muscle and most other tongue muscles. Some of its branches push the tongue forward. Others pull it back. Implants aim at the branches that push it forward.

Why the tongue falls back during sleep

When you are awake, your brain keeps the genioglossus a little tight, and it works a bit harder each time you breathe in. This helps hold the airway open.

• Sleep turns the signal down — the brain sends less drive to the airway muscles, most of all during dream (REM) sleep.
• Breathing in pulls inward — each breath creates suction in the throat. A relaxed airway can be sucked closed.
• Lying on your back — gravity lets the tongue slide toward the throat.
• A narrow airway — extra tissue, jaw shape or large tonsils leave less room.

Classic sleep studies showed that the airway closed when genioglossus activity fell during sleep, and opened again when the muscle became active as the person briefly woke.^[1] That brief wake-up restarts breathing, then you drift back to sleep, the muscle relaxes, and the cycle repeats. You may not remember waking, but the broken sleep can leave you tired the next day. For more on the condition itself, see what is obstructive sleep apnea.

How stimulation keeps the airway open

An implant gives the muscle back the signal that sleep takes away. A surgeon places a small lead on the hypoglossal nerve, connected to a generator or a power source. At night, mild pulses make the tongue move forward. The devices deliver the signal in different ways:

• Breathing-synced (Inspire) — a sensor lead between the ribs senses each breath, and the pulse comes as you breathe in, when the airway is most likely to close. It stimulates one side of the nerve.
• Set pattern on both sides (Genio) — stimulates the nerve on both sides on a set pattern rather than timing each pulse to your breath. It is powered by a part worn under the chin.
• Set pattern, closer to the start of the nerve (aura6000) — stimulates the nerve higher up, using several contacts on the nerve instead of a breathing sensor.^[5]

Stimulating one side of the nerve can still move the whole tongue forward, because the two halves of the tongue move together. Stimulating both sides is another way to get a strong, even push. Researchers are still learning whether one approach suits some people better than the other.

To compare the devices and who qualifies for each, see sleep apnea implants compared.

Who nerve stimulation may suit

Nerve stimulation fixes one problem: a tongue and airway that relax too much during sleep. It tends to fit people whose sleep apnea comes mainly from that.

• May suit — adults with moderate to severe obstructive sleep apnea who could not use CPAP, whose airway closes mainly from front to back, and whose weight is within the device's limit.
• May not suit — people with central sleep apnea, where the brain does not send the signal to breathe, or people whose airway closes in a ring at the soft palate. Stimulating the tongue does not fix those problems.

A sleep endoscopy, where a surgeon watches your airway during sedated sleep, can show how your airway closes. Your sleep doctor and surgeon decide together whether an implant makes sense.

What stimulation feels like

• A tingle and a push — most people feel a tingling and the tongue moving forward with each pulse.
• It starts after you fall asleep — the device can wait before it starts, so you can fall asleep first. You can pause it if you wake at night.
• Getting used to it — it can feel strange at first. Settings start low and are raised slowly.
• Possible side effects — tongue soreness, discomfort from the pulses, or soreness where the device was placed. Serious problems from the procedure were uncommon in the main study.^[2]

Turning it on and adjusting it (titration)

• Healing first — the device stays off for a few weeks after surgery while you heal.
• Activation visit — your care team turns it on and sets a safe, comfortable range.
• Slow increases at home — you raise the strength step by step within that range over several weeks.
• A sleep study to fine-tune — a sleep study with the device on helps find the setting that keeps your airway open.
• Ongoing check-ins — settings may change if symptoms return or your weight changes.

The Inspire therapy guide covers the surgery and recovery in more detail.

How well does it work?

• 12 months (Inspire) — in the main study of adults who had trouble with CPAP, the median apnea-hypopnea index (AHI) fell from about 30 to about 9 events an hour.^[2]
• When it is turned off, apnea returns — in the same study, people whose device was switched off had their apnea come back.^[2]
• 5 years (Inspire) — among people who had a sleep study at 5 years, about 75% still met the study's goal for fewer breathing pauses.^[3]
• Both sides (Genio) — about 64% of people met the study goal at 12 months.^[4]

People in the main study also reported less daytime sleepiness and better quality of life.^[2] The studies picked people carefully, so results in everyday care can differ. Your own follow-up sleep study is the real test. Learn how to read the results in sleep study results and AHI explained.

When to see a sleep specialist

• You cannot use CPAP — and want to know if nerve stimulation could fit you.
• You have an implant and still snore or feel tired — the settings may need a check or a new sleep study.
• The pulses are uncomfortable — settings can often be changed.
• Your weight or health has changed a lot — your treatment may need to change too.

Sleep apnea care in Cedar Park

Dr. Minal Patel is board-certified in pediatrics and sleep medicine. Our practice offers in-lab and home sleep studies, CPAP and BiPAP therapy, and Inspire evaluation. We do not perform surgery. We are accepting new patients. Office hours are Monday through Friday, 8:30 to 5:00. We accept Medicaid and CHIP for sleep patients. We do not take walk-ins.