Pierre Robin syndrome is a developmental disorder characterized by micrognathia, glossoptosis and cleft palate. It may or may not be associated with other syndromes. Early diagnosis and management helps in preventing complications.
The most common manifestation of Robin sequence is micrognathia. The inferior dental arch will be retracted behind the superior arch by several millimeters. This abnormality in mandibular growth is seen in 91.7% of the patients with Robin sequence. About 70-80% of the patients also show glossoptosis. Some may also present with macroglossia or ankyloglossia. These abnormalities in jaw and tongue are more or less evident at birth. Deformation of the jaw and tongue may result in respiratory trouble in newborn. Neonates with this condition may have emergencies and need intubation or a nasopharyngeal airway. Airway obstruction leads to hypoxia, cerebral impairment and cor pulmonale. There is also an increased risk of obstructive sleep apnea. Cleft palate occurs in 14-90% of the patients and it is usually seen in U-shaped form. In some rare cases it may be present as a bifid structure. Children may have feeding difficulties as the tongue is abnormally placed.
Around 10-85% patients are known to have different systemic abnormalities. Otitis media is found in 80% of the patients, while 75% may present with other auricular disorders. Many have conductive hearing loss. Studies have shown structural defects in the ear including abnormal auricles and ossicles . One of the most common systemic defects is musculoskeletal anomalies. Abnormalities like syndactyly, dysplastic phalanges, polydactyly, and clinodactyly are seen in many.
About a third of patients may present with different types of dental and philtral defects and deformations. Difficulty and defects in speech are also common in patients with this sequence. Other defects of the central nervous system associated with Robin sequence include epilepsy, language delay, hydrocephalus and hypotonia. Visual deficiencies including hypermetropia, myopia, corneal sclerosis and astigmatism are common in patients. About 5-58% may also show cardiovascular anomalies like pulmonary stenosis, murmurs, atrial septal defects and pulmonary hypertension. Pierre Robin syndrome may also be associated with some genitourinary defects like hydrocele, hydronephrosis and undescended testes.
Pierre Robin sequence is usually diagnosed at birth. In some cases, it may be detected prenatal when micrognathia or retrognathia is observed on ultrasound. Presence of excess quantity of amniotic fluid is an indicator of increased risk of this condition. Position of the tongue higher up in oral cavity is also a diagnostic feature of Robin sequence. To rule out the possibility of other syndromes, bone radiographs and ophthalmologic evaluations may be helpful. Once diagnosed, genetic evaluation is recommended. The first step towards diagnosis is to work whether it is isolated or syndromic. Genetic evaluation would be helpful in differentiating Stickler syndrome, one of the most common systemic conditions associated with Robin sequence.
In most of the patients conservative management of the condition with close monitoring and regular follow up helps to improve the condition. Conservative management is more suitable for patients with isolated form of Robin sequence. If the child is breathing without assistance he/she can be discharged as mandible will grow and resolve on its own. Follow up might be needed for speech development, feeding assessment and to monitor the breathing capacity. A recent study report that about 86.5% of the patients had improvement in airway with observation and follow-up .
Most of the neonates may have breathing problem due to micrognathia and glossoptosis. Prone position provides immediate relief to airway distress in most of the children. To improve positioning of airway, oral airway replacement, laryngeal mask, palatal prostheses, nasopharyngeal stenting, and intubation may be opted for. Since neonates may have feeding difficulties in addition to respiratory distress, feeding should also be carried out in prone position. Very few children may require gavage feeding tubes. If obstruction is severe and increases in the first 4-8 weeks of life, it should be considered as an emergency and intubation is required.
Surgery is recommended if the carbon dioxide level is consistently more. Surgical methods used for improving breathing capacity include tracheotomy and distraction osteogenesis of mandible. Tracheotomy tube enables to avoid the obstruction and the tube can be removed once condition resolves. But, it is recommended only in those patients with severe form of airway obstruction. In distraction osteogenesis, a mechanical device is used to separate mandibles where new bone forms and extends the mandible . This method is recommended for those cases where mandibular catch-up growth is very slow and less . Cleft palate can be repaired once the respiratory trouble caused by airway narrowing is improved. Cleft palate surgery is usually conducted when the child is 10 to 18 months old.
In children with syndromic form of Robin sequence, nasopharyngeal airway, glossoplexy, and tracheostomy are used to improve breathing capacity. In this case, a multidisciplinary approach is required for better outcome. Since different syndromes are associated with Robin sequence, a more accurate diagnosis based on the genetic structure is important in deciding the treatment modality. Management and treatment should be based on the type of obstruction in the airways .
Prognosis of this condition is favorable, if the clinical signs and symptoms are treated early in the life, and this is particularly true in the case of isolated Robin sequence. Features of Robin sequence, glossoptosis and respiratory trouble, usually resolve on its own within first two years of life. Micrognathia can be corrected with surgery before nine months.
Neurological defects may also resolve within a period of time. But, there may be some persistent conditions like otitis, and speech difficulties which may require further follow-up and consultations. Prognosis of syndromic Robin sequence depends on the syndrome with which it is associated. Syndromic form of Robin sequence is more complex when compared to isolated form and mortality rate is reported to be around 30% .
The actual cause for Robin sequence is not known. The sequence may be inherited as an autosomal recessive trait. An X-linked variant of the gene, related to abnormalities of heart and club foot, is also thought to be involved in inheritance of this disorder. The genetic defect may restrict the growth of the mandible during uterine growth of the fetus. Some reports link a deletion in chromosome 2 with the developmental abnormalities in the palate. In some patients, a translocation defect is reported, but the loci of translocation is not known . The genetic defect supposedly affects development of lower jaw which leads to abnormal positioning of the tongue and incomplete closure of palate.
Pierre Robin syndrome may also occur as one of the features of other syndromes or defects. It may be subdivided into three types:
Stickler syndrome, velocardiofacial syndrome, Nager syndrome, Catel-Manzke syndrome and spondyloepithelial dysplasia also show features of Robin sequence. Certain neurologic conditions may lead to Robin sequence by restricting the movement and growth of mandible during gestation. In some cases, utero-mechanical constraint may cause the chin of the fetus to be compressed in such a way that it affects the closure of the palate.
The prevalence of this condition is about one in 8500 to 14,000 births and the incidence is equally common among males and females. But this may be different in the case of Robin sequence caused by X-linked variant. A prospective study conducted in Germany reports the incidence to be 12.4 in 100,000 births . The incidence is found to be increased among twins. This is attributed to crowding during uterine development which restricts the growth and movement of mandible.
About 40% of Robin sequence detected is isolated form, 25% is associated with other syndrome, while 35% is unique with a complex of many other congenital abnormalities . The chances of getting another child with isolated form of Robin sequence is 3-5%. Robin sequence is associated with velocardiofacial syndrome in 10% of the cases while it is seen as one of the features of Stickler syndrome in 10-30% of the cases.
Three theories have been put forward to explain the occurrence of Robin sequence. The mechanical theory is the most commonly accepted dogma and suggests the occurrence of mandibular hypoplasia during 7th and 11th week of gestation. Mandibular hypoplasia causes an upward and posterior displacement of the tongue which affects the closure of the palate. As the palatal shelves are closed incompletely, it results in cleft palate, one of the typical features of Robin sequence. Various external and internal factors concerning mandibular development may also cause or contribute to this disorder. Oligohydramnios for example, lack of fluid in the amnion, may affect the development of chin and positioning of the tongue resulting in abnormal structure of the palate. The neurological maturation theory suggests that developmental delay in neurological structures and defect in hypoglossal nerve conduction result in abnormal positioning of the tongue and palate structure. The rhombencepahalic deneurulation theory explains the developmental delay and disorder is caused by motor and regulatory organization of the rhombencepahlus.
Robin sequence is a congenital disorder and is difficult to prevent. Early diagnosis and treatment with a multidisciplinary approach is important in avoiding complications that arise due to the sequence.
Pierre Robin syndrome, presently known as Pierre Robin sequence or Robin sequence in short, is a developmental disorder characterized by a triad of features:
It is called a sequence as it refers to a series of disorders starting from a developmental abnormality. There is no clear consensus on the definition and classification of this condition with varied opinions expressed in different publications . This sequence may occur as an isolated condition or as a feature in a variety of other rare syndromes including Stickler syndrome. Children with a severe form of Robin sequence may present with breathing and feeding difficulties. In some cases Robin sequence may be seen as a unique form where in it occurs with unique anomalies . Robin sequence is rare in occurrence and is equally common among males and females.
Pierre Robin syndrome or Robin sequence is a condition characterized by three features – small lower jaw, large and backward-positioned tongue, and cleft palate. During the gestation period, the small lower jaw and large tongue prevents the palate from closing, leaving a U-shaped cleft leading to breathing difficulty. The actual cause of this condition is not yet known. A number of factors that causes crowding of the uterus and hinders jaw growth may lead to this syndrome. Certain neurological conditions and genetic defects also cause this syndrome. Pierre Robin syndrome is relatively rare and is equally common in both boys and girls. This syndrome is found to be more prevalent among twins, probably due to crowding in uterus during development. Robin sequence is also seen as a part of other syndromes including Stickler’s syndrome and Velocardiofacial syndrome.
The most common symptoms of this condition include small jaw, large and backwardly placed tongue and U-shaped palate. These features are very evident from birth and may or may not be diagnosed during ultrasound scan during gestation. Newborns may have mild to severe breathing difficulties, hearing problems and difficulty in swallowing. Eyes also may have some amount of malformations. Children who have severe respiratory difficulties require immediate attention. Intubation may be needed in some cases to improve breathing. In most, the catch up growth will resolve the structure of smaller jaw and positioning of tongue, thus improving breathing and feeding. If breathing does not improve within 4-8 weeks, other methods may be recommended. Surgery is suggested in some cases to correct the tongue and palate. Close monitoring and follow-up is important in controlling and treating the condition.
Overall, the outcome of the disorder is good unless it is associated with other syndromes and complications. Most of the children with this condition show improvement in feeding and breathing by the age of three.