However, in PRS the small mandible keeps the tongue positioned higher in the mouth than normal, thereby interfering with the normal closure of the palate. This allows space for the sides of the palate to shift to the midline and close. Normally, between 9 to 11 weeks of gestation, the tongue moves down and away from the roof of the mouth. In addition, some studies demonstrate there may be genetic anomalies at chromosomes 2, 11 or 17. Certain neurological conditions, which lead to decreased jaw movement in utero, can also restrict jaw growth. It is believed that any external factor crowds the fetus and interferes with the growth of the lower jaw. Causes & Risk FactorsĪn exact cause of PRS is not known. Patients can be seen by Texas Children's experts in Plastic Surgery. The condition is called a sequence because it is believed the underdeveloped mandible begins a sequence of events, which leads to the abnormal displacement of the tongue and subsequent formation of a cleft palate. PRS may occur in isolation, but it is can be part of an underlying disorder or syndrome. There is a higher incidence in twins, which may be due to crowding in the uterus, restricting growth of the mandible (lower jaw). This condition occurs in approximately 1 in 8,500 to 14,000 births, and it’s equally common in males and females. glossoptosis (airway obstruction caused by backwards displacement of the tongue base).severe underdevelopment of the lower jaw (retrognathia).cleft palate (opening in the roof of the mouth).The three main features that characterize PRS are: Pierre-Robin Syndrome (PRS), also known as Pierre Robin sequence, is a congenital condition that affects the lower jaw and palate.
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