Micrognathia – Types, Causes and Treatment

What is Micrognathia?

Micrognathia is a condition where the jaw is undersized. It is also sometimes called “mandibular hypoplasia”. This condition is common during infancy. It however is usually self-correcting during growth with a gradual increase in the size of the mandible to normal size. Since the jaw size discrepancy will be pronounced during infancy, it can lead to abnormal alignment of teeth. When this is severe, it can even lead to disruption in the feeding patterns of the infant.

Micrognathia may resolve on its own as the child grows, particularly during puberty. While the condition is still present, however, micrognathia can cause complications that affect development. The infant may have difficulty feeding, their teeth may not grow properly, and they may have trouble breathing, leading to obstructive sleep apnea.

A surgical implication of micrognathia in both children and adults is that it can made intubation difficult. Anesthesia is induced through awake bronchoscopic intubation in the presence of micrognathia. Micrognathism, which is true hypoplasia of the mandible is different from retrognathism, which is a backwardly positioned mandible.

Epidemiology

Epidemiological data for isolated micrognathia (without other abnormalities) are uncertain. The available data generally discuss micrognathia associated with a particular syndrome. For example, micrognathia is often part of the Pierre-Robin sequence and is often accompanied by a cleft palate. The Pierre-Robin sequence is reported to occur in 1 in 8,500 live births.

Types of Micrognathia

There are two types of micrognathia:

True micrognathia

True micrognathia is when the jawbone is abnormally small.

Relative micrognathia

Relative micrognathia is when the jawbone appears small due to other factors, such as a large tongue or a small upper jaw.

Micrognathia Symptoms

Children with micrognathia often show the following signs and symptoms:

• Failure to thrive – inadequate growth during early childhood.
• Infant apnea – temporary cessation of breathing.
• Feeding difficulties – the inability to feed, problems with latching, and insufficient weight gain.
• Noisy breathing.
• Tongue-tie – the tongue is attached to the mandible near the chin.
• Sleep disturbances.
• Glossoptosis – retraction or downward positioned tongue.
• Breathing problems – can result in cyanosis, where the baby’s skin or mucous membrane turns blue due to lack of oxygen.

Causes of Micrognathia

Most children with micrognathia are born with it. Micrognathia may be caused by over 700 genetic mutations or inherited conditions that cause craniofacial abnormalities like small lower jaws, including:

• Achondrogenesis
• Cleft lip or palate
• Cri du chat syndrome
• Fetal alcohol syndrome
• Hallermann-Streiff syndrome
• Goldenhar syndrome
• Melnick Needles syndrome
• Marfan syndrome
• Nagar syndrome
• Pierre Robin sequence
• Progeria
• Russell-Silver syndrome
• Seckel syndrome
• Smith-Lemli-Opitz syndrome
• Treacher-Collins syndrome
• Trisomy 9
• Trisomy 13
• Trisomy 18
• XO syndrome

Many of the genetic conditions that cause micrognathia are rare. For example, Pierre Robin sequence affects 1 out of every 8,500 to 14,000 new-borns, while 1 in 16,000 babies has trisomy.

Complications

Micrognathia can result in breathing or feeding problems in babies. Most of the time, the condition corrects itself as children grow older. In some cases, however, it’s associated with underlying genetic conditions, such as cleft lip and palate, Pierre Robin syndrome and Treacher Collins syndrome.

How to Diagnosis Micrognathia?

Some micrognathia cases are diagnosed before the baby is born, during a mother’s routine ultrasound exams. Otherwise, the condition can usually be diagnosed on sight after birth, meaning your doctor may simply notice that your baby’s jaw looks smaller than normal. If your child has a small jaw, their doctor will perform a full physical examination, including looking inside their mouth.

Some tests may be needed in order to determine how serious the condition is. These tests may include:

• CT scan of the facial bones: A CT scan takes pictures in “slices” and puts them together to make a highly detailed 3D picture
• A sleep study: This can help identify the severity of any sleep and breathing problems.
• An airway endoscopy.
• A swallowing study.
• Blood tests: These allow the doctor to identify any genetic causes of the condition.

Your child may need to be evaluated by several specialists, including a craniofacial surgeon, an otolaryngology (ENT) surgeon, a genetic specialist, and a speech pathologist who is also a feeding specialist.

Treatment for Micrognathia

Sometimes an undersized jaw gets better by itself, so monitoring the child’s progress can be a form of treatment. If micrognathia corrects itself, it usually occurs when the child is between 6 and 18 months old. Other treatments can be surgical or non-surgical. They aim to keep the tongue from blocking the airway and otherwise ensure an adequate air supply.

Non-Surgical Treatments

The most common nonsurgical treatments for micrognathia include:

• Positional therapy. To help keep your baby’s airway open, your healthcare provider may recommend specific sleeping positions.
• Nasopharyngeal tube. This device is inserted into your child’s nostril and through their nasal passageway to keep the airway open.
• Positive airway pressure. A bilevel positive airway pressure (often known under the trade name BiPAP®) or CPAP device sends air through a tube and into a mask that fits over your child’s nose. This continuous air pressure keeps your child’s airway open.

A nasopharyngeal tube (NPT) positioned in the pharynx below the level of the obstructing tongue base.

Surgical Treatments

Three main surgical procedures are available for children with micrognathia:

Tongue-lip adhesion. This surgery attaches the tongue differently to the lower jaw so that it can’t obstruct breathing.

Mandibular distraction osteogenesis (MDO). A surgeon makes cuts in the lower jawbone on both sides. He inserts devices that spread the gaps apart, promoting bone growth in the space. This surgery carries some risks, such as infection and nerve damage, but it can improve the airway in a matter of weeks.

Tracheostomy. In this procedure, doctors make a hole in the neck and insert a tube into the windpipe to create an airway. Tracheostomies require careful tending and sometimes frequent suctioning. One reason for performing an MDO is that it may allow children with micrognathia to avoid having a tracheostomy.

Prevention of Micrognathia

It is typically is a congenital condition, there’s no method to prevent it. Additionally, there’s no way to escape most of the underlying conditions associated with it. However, there are some steps that can be taken to reduce the risk of developing the condition. These include:

• Avoiding exposure to harmful substances during pregnancy
• Getting regular prenatal care
• Following a healthy diet and exercise routine
• Avoiding smoking and alcohol consumption during pregnancy