Micrognathia and Pierre Robin sequence
What is Micrognathia and Pierre Robin sequence?
Micrognathia is a smaller than normal jaw, often the lower jaw or chin. This may be part of a syndrome. A syndrome is a pattern of multiple anomalies or birth defects with a single cause. This single cause can be genetic or hereditary. The birth defects seen in a syndrome involve more than one body system, meaning, for example there may be a problem with the jaw, heart and the kidneys.
Pierre Robin (Pee-air; Ro-ban) sequence is also associated with micrognathia. Pierre Robin sequence is a birth defect that involves the jaw or chin being small and recessed. If Pierre Robin is isolated, meaning there are no other conditions or anomalies, it is referred to as a sequence. A sequence is defined as more than one defect that occurs as a result of a single presumed structural problem that starts a chain of events. This chain of events will result in changes in development of another organ or body part. Pierre Robin fits this definition of sequence if there are no other birth defects except those related to the small chin, tongue and cleft palate.
The chain of events that leads to this sequence is believed to begin between the seventh and eleventh week of pregnancy when the mandible (lower jawbone) fails to grow properly for unknown reasons. Doctors suspect several factors may prevent the jaw from growing, including:
Positional malformation (the chin is pressed against the chest of the baby).
Intrinsic hypoplasia (it is part of a syndrome which may be genetic/hereditary).
Neurologic or neuromuscular problems (low movement related to muscle or nerve involvement).
Connective tissue disorder (low movement related to connective tissue problems of the jaw).
The sequence of events due to the small lower jaw include the tongue being pressed up (against the palate or roof of the mouth). This pressure against the roof of the mouth does not allow the tongue to grow properly. The position of the tongue also prevents closure of the palate or roof of the mouth. These three characteristics may be seen with Pierre Robin sequence.
The most common problem (seen in 91.7 percent of Pierre Robin cases) is a small, receded jaw line. After birth the small jaw cannot hold the tongue in a forward position and the tongue is usually shorter than normal. The combination of the small jaw and short tongue allows the tongue to block the airway. The third problem is a U-shaped cleft palate or hole in the roof of the mouth. This combination of a small jaw, small tongue that tends to block the airway and hole in the roof of the mouth all contribute to severe respiratory distress (or difficulty with breathing) and feeding problems in the newborn.
By 6 to 18 months of age, the mandible (jawbone) usually will have grown enough to improve the airway issue, and by 5 to 6 years of age, these children have a more normal profile due to growth of the mandible or jaw. Pierre Robin occurs in about 1 per 8,500 live births. It occurs equally in males and females. We do not know the cause of Pierre Robin sequence but we do know it is not caused by anything the mother did or did not do during pregnancy.
Prenatal diagnosis of Pierre Robin sequence
With routine ultrasound, the receded chin may be seen on a profile view of the face. However, this diagnosis is often missed during an ultrasound. The mandible is known to grow significantly in the third trimester. If micrognathia is suspected, particular attention will be paid to the growth of the chin throughout the remainder of the pregnancy. Up to 60 percent of pregnancies in which micrognathia is seen also are complicated with a larger than normal volume of amniotic fluid. This is likely due to the fact that the baby is not able to swallow well. While babies are in the womb they will swallow the amniotic fluid that surrounds them, which helps keep the volume of fluid at a constant level. If a baby cannot swallow, the amount of fluid can increase. When a smaller chin is noted, because of the increased likelihood of other birth defects, your doctor will most likely refer you to a perinatologist. Perinatologists are obstetrician/gynecologists who are specially trained to manage high-risk pregnancies. A more detailed ultrasound will be done to look closely at all of the baby for other birth defects. Some doctors also may want to do an MRI (magnetic resonance imaging) at some time during the pregnancy to examine the palate of the baby.
How does Pierre Robin sequence affect my baby?
A baby who has been diagnosed before birth with micrognathia should be delivered at a tertiary care center because of possible difficulties with breathing. A neonatologist or a pediatric anesthesiologist should be available to assist in the resuscitation efforts in the delivery room. Often positioning and/or a nasal airway are enough to keep the baby's airway open, but a tube may need to be inserted to help the baby breathe. Putting in a tube for a baby with micrognathia can be difficult due to their anatomy. Even more rarely, a tracheostomy tube may need to be placed in the delivery room because the anatomy of the baby does not provide an adequate airway. A tracheostomy is a surgery that creates an airway through the front of the neck. If there are concerns about the airway, plans may be made for you to deliver your baby in a Children's
The two biggest issues for these babies are airway and feeding issues. The cleft palate, in combination with the small tongue, prevents them from forming an effective suction. They have a difficult time taking in enough calories to grow. Due to the above issues, breastfeeding is usually unsuccessful. Breast milk or formula can be placed in a bottle to be given to the baby. It is a matter of trial and error to find out which nipple, the size of the hole in the nipple and what position works best for your baby.
How does Pierre Robin sequence affect my pregnancy?
If your doctor suspects a problem with your baby, you likely will be referred to a perinatologist. These are doctors who handle high-risk pregnancies. The perinatologist will perform a targeted ultrasound to evaluate the remainder of your baby for any other problems. Special attention will be given to the heart and skeleton.
When micrognathia is suspected before the baby is born, it is recommended that chromosomes be evaluated. This is done through a genetic test called an amniocentesis. The doctor will discuss risks and benefits of this test with you before it is done. Because of an increased risk of heart disorders seen with micrognathia, a fetal echocardiogram (ultrasound of the baby's heart) may also be recommended. Echocardiogram is an ultrasound that looks at the heart's anatomy, blood flow and circulation. A pediatric cardiologist would perform this test before the baby is born and maybe again after birth to confirm what they suspect initially on prenatal views. There are no special considerations regarding how the baby is delivered. The major delivery issue is that it should occur at a hospital where neonatology or pediatric anesthesiology is available if the baby has trouble breathing.
How is Pierre Robin sequence treated?
The two major issues that require treatment initially are related to breathing and feeding. When and if the baby is crying, there usually is not a problem with the tongue. However, when the baby relaxes or goes to sleep, the tongue is more likely to fall back and block the airway. Positioning the baby for sleep may mean he or she needs to be prone or on their stomach when lying down. In this position, the tongue should fall forward because of gravity. Another way to keep the airway open is with a special device placed in the baby's mouth on top of the tongue to hold it in place and keep it from blocking the airway while the baby sleeps. The baby will need to be examined to decide how safe the baby will be when he or she eats and sleeps. The exam team may include an ear, nose and throat physician specialist, craniofacial/plastic surgeon and pulmonologist. The baby can be evaluated to see if one of three potential procedures may be needed:
Tracheostomy, if the first two procedures don't work.
Tongue-lip adhesion involves sewing the tongue to the lower lip to hold it out of the airway.
Lower jawbone growth can now be enhanced by using mandibular distraction. This is a surgical procedure in which a special appliance is inserted into the jawbone. The external portion of the appliance has a key-type mechanism that when turned, stretches the appliance and ultimately, the bone and soft tissue, and causes them to grow. This is a very simple, effective, less invasive and more successful way to treat micrognathia. It is now considered the best treatment for those infants that have a lot of airway issues and/or moderate to severe deformity of the jawbone. By using this device, no bone grafts are needed and the treatment can start at a younger age. With this more rapid growth of the jawbone, a tracheostomy may be avoided.
A tracheostomy is a surgical procedure that places a hollow tube into the windpipe to create an airway. The tube is placed in the lower middle portion of the neck. The baby will breath through this tube.
Feeding is the second major issue with these babies. When feeding, positioning the baby sitting and tipped slightly forward can help keep the tongue out of the way. However, it is sometimes very difficult to keep the tongue down to get the bottle nipple in the mouth. Sometimes, a gastrostomy tube (GTT) is needed to ensure that the baby gets enough food. The placement of this tube is done in surgery. The tube is placed directly into the stomach through a small hole made in the abdomen. Through the GTT we are able to provide the baby an adequate amount of formula or breast milk.
What about after surgery?
After a tracheostomy, these babies will have more secretions because of the surgery and the tube that is in the airway. Frequent suctioning may be needed. Oxygen can be provided through the new tracheotomy tube. The air should be humidified to keep the secretions loose. If the mucous is too thick it can form a plug that potentially may block the tube, which is life threatening. The tube is left in place for five to seven days to allow for healing of the surgical site. Then, the tube will be changed and can be switched to a metal tube with an inner cannula. This inner cannula can be removed and cleaned periodically, which helps keep the tube clear of secretions and maintain the airway. The surgical opening needs to be kept as clean and dry as possible to ensure that the site does not become infected. If the plan is for your baby to go home with a tracheostomy, the home care teaching will begin right away. You will also need to begin to prepare your home with the equipment necessary to care for your baby. Before your baby goes home, you will learn about all equipment, emergency procedures and daily care.
If a GTT is needed, the surgical site must be kept clean and dry to help healing and prevent infection. The gastrointestinal tract is given time to recover from surgery and then feedings will be started through the tube. You will be taught how to care for the tube and insertion site (also called a stoma) and how to feed the baby through this tube before he or she goes home.
If a distraction device is used, care of the site will be reviewed with you as well as signs and symptoms of complications and device malfunction. Again, the site needs to be kept clean and dry for healing and to prevent infection.
Will I be able to help care for my baby after surgery?
Yes. Please ask your baby's nurse about ways to interact with and care for your baby. If you had planned to breastfeed your baby, you can begin to pump breast milk while you are still in the hospital. A lactation consultant can assist in answering your questions. Your milk will be frozen and stored in the Neonatal Intensive Care Unit until your baby is ready for it. The NICU has breast pumps and private rooms available to you when you are visiting. You can bring in pictures, small toys, booties and blankets for your baby while he or she is in the NICU.
When can my baby go home?
Your baby will go home when he or she is able to keep his or her airway open and eat enough to grow and gain weight. It is very difficult to predict the length of stay for these babies because of the wide variation in the type of interventions that may be needed. Many of these babies will go home with a variety of equipment, including an apnea monitor. As the parent, part of the discharge planning involves teaching you all you need to know to care for your baby at home. If the baby needs surgery, he or she will need time to recover and learn to eat enough to grow. Expect a minimum of one to two weeks for those minimally affected and four to six weeks for those who require a gastrostomy tube and/or tracheostomy. The length of stay can also be affected by associated anomalies.
What is my baby's long-term prognosis?
The survival of a child born with Pierre Robin sequence that does not have other problems is good. The most likely cause of death for these children is related to a blocked airway and/or aspiration. The mandible usually has grown sufficiently by 6 to 18 months of age, whether distraction is used or not, so that the airway problem is not as critical of an issue. Distraction may be used to help the growth occur more quickly.
The other complications are related to surgery (cleft palate repair, mandibular distraction, gastrostomy or tracheostomy). The incidence of fatal complications related to surgery are extremely rare.
Babies with a tracheostomy have a higher mortality rate than others. Long-term tracheostomy in an infant carries a mortality rate of 20 percent.
Because Pierre Robin sequence is a cleft-related disorder, these children are much more prone to fluid buildup behind the eardrum, which can affect hearing. This fluid buildup can lead to ear infections. Therefore, these children need long-term follow-up with ear, nose and throat specialists and an audiologist. The audiologist specializes in testing the hearing of infants and children.
The cleft palate can cause problems with speech. Children with a cleft palate also need follow-up by a speech pathologist and may require speech therapy.
You will be referred to a geneticist. Pierre Robin sequence can be part of a more complex syndrome. If it is discovered that your baby has a syndrome, there is an increased risk of future children being affected. Some syndromes also need follow-up by other specialists, especially an opthalmologist for vision issues.
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