Micrognathia and Sleep Apnea

Key Takeaways

• Micrognathia refers to having a small lower jaw, which can result in an overbite, but in more severe cases, it can impact breathing.
• Micrognathia could be an underlying cause of obstructive sleep apnea (OSA) because it causes the tongue to sit back and block the upper airway.
• Babies and children with micrognathia could have problems eating or breathing, but in less severe cases, they may grow out of it naturally.

Micrognathia Definition

Micrognathia, one of the most common facial irregularities, occurs when the lower jaw grows too slowly. Around a third of people with micrognathia also have signs or symptoms of a genetic syndrome. A genetic syndrome is a group of medical conditions that occur together because of a mutation or change in a person’s DNA. 

In people with micrognathia, a small mouth often occurs alongside an underdeveloped jaw. Without room for the tongue to sit properly in the mouth, the tongue may slide into the back of the throat. The irregular position of the tongue can block the upper airway and lead to sleep-related breathing disorders. 

Micrognathia on Ultrasound

Oftentimes, micrognathia is first diagnosed in the womb via ultrasound if the physician can get a clear profile view of the fetus. An abnormally small mandible can usually be detected as early as 12 to 14 weeks of gestation. Further observation and genetic testing may be recommended. At the very least, a third trimester ultrasound will reevaluate the mandible.

Micrognathia in Newborns

Micrognathia can cause difficulties for babies born with the condition. For instance, the irregular position of the tongue makes it difficult for newborns to breathe and eat properly. Newborns with underdeveloped jaws may need to use a feeding tube or special nipples on their bottles, or they may require surgery.

Micrognathia in Children

Micrognathia affects older children as well, mostly from an appearance perspective. But it can also come with a greater risk of obstructive sleep apnea. Some children with micrognathia outgrow the condition as they get older and their jawbones lengthen. 

Micrognathia in Adults

By adulthood, some people born with micrognathia develop average-sized jaws. But those who still have underdeveloped jaws can have health problems related to the condition. Adults with micrognathia may have dental problems because the lower jaw doesn’t lengthen enough to provide space for the adult teeth, which become crowded or misaligned.

Micrognathia and Sleep Apnea

People born with micrognathia have shorter jawbones, creating a narrow airway and making it harder to breathe while sleeping. Along with limited space for the tongue to sit in the mouth, the narrow airway constricts airflow during the night, leading to an increased risk of developing obstructive sleep apnea.

Micrognathia and Sleep Apnea in Children

Sleep apnea in children is generally rare, affecting only 1% to 5%. But the presence of micrognathia greatly increases the risk for breathing disorders. Up to 88% of children with micrognathia show signs of obstructive sleep apnea, in which a blocked airway repeatedly pauses breathing while a person sleeps.

When a child with micrognathia rests on their back, their tongue is more likely to shift toward the back of the throat and block airflow. In severe cases, micrognathia may also cause breathing difficulty and require emergency care.

In addition, a smaller jaw size has been associated with neuromuscular conditions that lead to nerve damage and muscle weakness. This combination of micrognathia and weakened muscles in the mouth and throat make breathing more difficult. Lastly, children with micrognathia may overwork the upper airway muscles, causing the windpipe to collapse. 

Symptoms of OSA in children include:

• Snoring and noisy breathing
• Mouth breathing
• Bedwetting
• Restless sleep
• Sweating during sleep
• Gasping, coughing, or choking while asleep

Untreated OSA in children can lead to learning difficulties, behavioral problems, and slower growth rates. If your child has difficulty breathing at night, talk with your healthcare provider about the signs and symptoms of obstructive sleep apnea.

Micrognathia and Sleep Apnea in Adults

Obstructive sleep apnea occurs in 10% to 30% of adults. But adults with micrognathia have an increased risk of developing OSA because their shorter jaw length causes more breathing issues. Adults with OSA may snore loudly, have trouble falling asleep or staying asleep, and feel excessively tired during the day. 

Untreated OSA may lead to poor work performance, lower quality of life, and a higher risk of car accidents. And untreated OSA increases the risk of developing other health conditions, including:

• High blood pressure
• Stroke
• Type 2 diabetes
• Depression
• Congestive heart failure
• Cardiac arrhythmias

Causes of Micrognathia

Micrognathia can be a symptom of a genetic condition or caused by developmental problems in the womb that prevent the growth of the jawbone. Injuries to the facial joint and medical treatments like radiation and surgery can also lead to a small lower jaw.

Other potential causes for micrognathia can include musculoskeletal conditions affecting the bones and joints or connective tissue disorders that affect the skin, eyes, and blood vessels. In some cases, micrognathia has no known cause.

Micrognathia and Pierre Robin Syndrome

When micrognathia appears with a tongue at the back of the throat and a high arch at the top of the mouth, doctors may diagnose Pierre Robin syndrome. This syndrome usually develops before the ninth week of pregnancy. In Pierre Robin syndrome, the small jawbone makes the tongue move backwards, stopping the roof of the mouth from fusing and creating a cleft palate. 

The cause of Pierre Robin syndrome isn’t known, but it could be due to genetic disorders, lack of fluid around the baby, muscle issues, or problems with connective tissue. Sometimes, Pierre Robin syndrome happens by itself, but in other cases it’s part of a syndrome with additional birth disorders.

Some experts suggest that babies and children with Pierre Robin syndrome should be screened for sleep-related breathing disorders like obstructive sleep apnea. But as their facial bones grow longer during the first year, many babies with Pierre Robin syndrome experience fewer breathing difficulties.

Micrognathia and Teacher Collins Syndrome

Teacher Collins Syndrome is another genetic condition that affects facial development. In addition to a small jaw, it can also cause an abnormal eye shape, a missing outer ear, cleft palate, and other symptoms. The condition is diagnosed at (or before) birth, and may require surgical treatments depending on the severity. Treatment for hearing and vision loss may also be needed.

Micrognathia Diagnosis

Micrognathia is typically diagnosed through a prenatal ultrasound conducted during the second trimester, which is between the 13th and 28th week of pregnancy. But doctors may also notice the condition in infancy, since newborns with micrognathia often struggle to breathe and eat normally. 

Some babies with micrognathia have additional abnormalities associated with genetic syndromes and need genetic testing. Genetic testing identifies the exact differences in a child’s DNA, helping doctors diagnose specific genetic syndromes and provide more comprehensive medical care.

Micrognathia and Sleep Apnea Diagnosis

Diagnosis of obstructive sleep apnea for adults and children with micrognathia includes a sleep study or polysomnography. The sleep study is a test performed in a special laboratory or with a sleep test at home. Sleep specialists measure functions such as breathing rate, blood oxygen levels, and brain waves. 

A sleep study also records the number of times a person stops breathing during sleep. The specialist uses this number to determine the person’s apnea-hypopnea index (AHI). Adults with an AHI greater than five and children with an AHI greater than one typically have obstructive sleep apnea.

Micrognathia Treatment

Treating micrognathia can improve obstructive sleep apnea by lengthening the jawbone and giving the tongue more space to rest inside the mouth.

• Distraction osteogenesis: This procedure involves lengthening the lower jaw by placing a separator between two sections of the jawbone. New bone grows between the sections to make the lower jawbone longer, helping the jaw work better. 
• Maxillomandibular advancement (MMA): MMA surgery reshapes the upper and lower jaw to pull the jawbone forward. The advancement of the lower jawbone can provide some people with micrognathia permanent relief from OSA symptoms.
• Tongue-lip adhesion (TLA): While the TLA procedure doesn’t directly treat micrognathia, the operation prevents the tongue from blocking the upper airway. TLA surgery attaches the tongue to the lower lip or gums to prevent it from falling back into the mouth and throat.
• Nasopharyngeal airway (NPA): A nasopharyngeal airway or tracheotomy may work for children who have symptoms despite sleeping on their stomachs. During the NPA procedure, a small plastic tube separates the tongue and the back of the airway to improve breathing.

Micrognathia and Sleep Apnea Treatments

Although many sleep apnea treatments aim to keep the airway from becoming blocked, the treatments don’t directly correct micrognathia. The most effective method to treat obstructive sleep apnea with micrognathia is positive airway pressure (PAP) therapy. 

Continuous positive airway pressure (CPAP) and auto-titrating positive airway pressure (APAP) are the most common types. These devices deliver pressurized air through a tube and into a sleeping person’s nose or mouth through a mask. The flow of air through the mask keeps the airway from becoming blocked during the night.

Other treatment options for people with obstructive sleep apnea also help keep the upper airway from collapsing during sleep. Alternative treatments for obstructive sleep apnea include:

• Oral appliances
• Lifestyle changes like changing sleep positions
• Weight loss
• Surgery

If you have obstructive sleep apnea, speak to your healthcare provider about the treatment options best suited to your individual needs.

Frequently Asked Questions

Can micrognathia correct itself?

In babies who are born with micrognathia, it can resolve itself during periods of major jaw growth both in the toddler phase (up to around 18 months), and later on in puberty. 

How common is micrognathia?

Micrognathia is present in about 1 per 1,500 babies at birth. Causes are wide-ranging, however, with some conditions more serious than others. Some cases of micrognathia will resolve themselves as babies and children grow.

Is micrognathia genetic?

Micrognathia can be the result of a genetic condition, but not always. In some cases, even when genetic, it isn’t necessarily inherited from a parent or grandparent, but rather occurs because of a mutation in certain genes. Non-genetic causes could be environmental, or from exposure to toxins or trauma during pregnancy.

What’s the difference between micrognathia and retrognathia?

Both micrognathia and retrognathia are facial abnormalities having to do with the jaw (mandible), but they’re different. Micrognathia is when the jaw is too small, while retrognathia means the mandible is positioned further back than where it should be. Both conditions can impact airways and be a cause of OSA. Retrognathia can often be corrected by orthodontics.