Pierre Robin syndrome

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Pierre Robin Sequence

Pierre Robin Sequence (PRS), also known as Pierre Robin Syndrome or Pierre Robin Malformation, is a congenital condition of facial abnormalities in humans. As PRS is not caused by a single defect gene, it is not a genetic syndrome, but rather a chain of certain developmental malformations, one entailing the next.

PRS is characterized by an unusually small jaw (micrognathia), posterior displacement or retraction of the tongue (glossoptosis), and upper airway obstruction. Incomplete closure of the roof of the mouth (cleft palate), is present in the majority of patients, and is commonly U-shaped.

It is not known just how this abnormality occurs in infants, but one theory is that, at some time during the stage of the formation of the bones of the fetus, the tip of the jaw (mandible) becomes 'stuck' in the point where each of the collar bones (clavicle) meet (the sternum), effectively preventing the jaw bones from growing. It is thought that, at about 12 to 14 weeks gestation, when the fetus begins to move, the movement of the head causes the jaw to "pop out' of the collar bones. From this time on, the jaw of the fetus grows as it would normally, with the result that, when born, the jaw of the baby is much smaller (micrognathia) than it would have been with normal development, although it does continues to grow at a normal rate until the child reaches maturity.

PRS is often part of an underlying disorder or syndrome. The most common is Stickler Syndrome. Other disorders causing PRS, according to Dr. Robert J. Sphrintzen Ph.D. of the Center for Craniofacial Disorders Montefiore Medical Center are Velocardiofacial syndrome, Fetal Alcohol Syndrome and Treacher Collins Syndrome. For more disorders associated with PRS see Dr. Sphrintzen's article entitled The Implications of the Diagnosis of Robin Sequence.

The syndrome is generally diagnosed shortly after birth. It has an incidence ranging from 1 in 8500 to 1 in 30,000. The most important medical problems are difficulties in breathing and feeding. Affected infants very often need assistance with feeding, for example needing to stay in a lateral position, needing specially adapted teats or spoons to feed, and often needing nasogastric feeding or supplemental feeding for periods due to slow feeding. This is related to the difficulty in forming a vacuum in the oral cavity related to the cleft palate, as well as to breathing difficulty related to the posterior position of the tongue. Infants, when moderately to severely affected, may occasionally need nasopharyngeal cannulation or more rarely endotracheal intubation or tracheostomy to overcome upper respiratory obstruction.

In nasopharyngeal cannulation, the infant is fitted with a blunt-tipped length of surgical tubing, which is inserted into the nose and down the throat, ending just above the esophagus. Surgical threads fitted through holes in the outside end of the tube are attached to the cheek with a special skin-like adhesive material called 'stomahesive', which is also wrapped around the outside end of the tube (but not over the opening at the end) to keep the tube in place. This tube or cannula, which itself acts as an airway, primarily acts as a sort of "splint" which makes further airways on either side of the tube between the tongue and the throat wall, thus assisting the infant in breathing and preventing the tongue from falling back down into the throat, which would cause the infant to asphyxiate. Nasopharyngeal cannulation should be favoured over the other treatments mentioned in this article, as it is far less invasive, it allows the infant to feed without the further placement of a nasogastric tube, and the infant can be placed in the prone position without fear of asphyxiation. This treatment may be necessary for a period of up to six months or more, until the jaw has grown enough so that the tongue assumes a more normal position in the mouth and airway (at birth, the jaws of some infants are so underdeveloped that only the tip of the tongue can be seen when viewed in the throat).

The cleft palate is generally repaired between the ages of 6 1/2 months and 2 years by a plastic or maxillofacial surgeon. In many centres there is now a cleft lip and palate team comprising both of these specialties, as well as a coordinator, a speech and language therapist, an orthodontist, sometimes a psychologist or other mental health specialist, an audiologist, an otorhinolaryngologist (ENT surgeon) and nursing staff. The glossoptosis and micrognathism generally do not require surgery, as they improve to some extent unaided, though the mandibular arch remains significantly smaller than average. In some cases jaw distraction is needed to aid in breathing and feeding. Lip-tongue attachment is performed in some centres, though its efficacy has been recently questioned.

Children affected with PRS usually reach full development and size. However, it has been found internationally that the child is often slightly below average size, raising concerns of incomplete development due to chronic hypoxia related to upper airway obstruction as well as lack of nutrition due to early feeding difficulties.