Pierre Robin Sequence: A Common Presentation Tulika Shinghal, DMD; and Ted L. Tewfik, MD, FRCSC ierre Robin Sequence (PRS), a well-recognized Oligohydramnios can be a possible Ppresentation, is the association of the first contributing factor. Decreased amniotic fluid branchial arch malformation. It presents with the causes reduced support for the fetal head with classic triad of micrognathia, glossoptosis and u- resultant downward flexion of the chin. Other shaped cleft palate. In 1923, a French physician, causes of intrauterine constriction include Pierre Robin introduced the term “glossoptosis” in multiple births, uterine abnormalities or association with micrognathia which resulted in abnormal zygotic implantation sites. grave upper airway obstruction in newborn infants. Numerous syndromes are associated with He subsequently reported an association with cleft intrinsic hypoplasia palate in 1934. This constellation of findings was 2. The neurological maturation theory is termed a syndrome until 1976 when Cohen intro - suggeste©d by electromyography of thteitongnue duced the word anomalad, defined as “a malforma - muscutlature, pharyngeal pillairbs aund palate. gh str d, tion together with its subsequent derived structural ri The inability of tDhe dievelopinnlgofaetus to py l dow o cia can e changes.” The term PRS is currentlCy used. It reflects enegarge in msaenrdsibular exaelrcuise prevents the m ed u son the developmental cascade of these anomalies wimth toonrgiuse from drepsceernding. The spontaneous Co Auth y fo micrognathia being the primary anomraly that ttehedn . correccotipon with age supports this theory e o hibi ingle causes the other two to ocacurl. e pro t a s3. The dysregulation theory or the motor r S d us prin fo rise and and regulatory organization of the t utho view No Una lay, Epidemiology disp rhombocephalus is related to a major problem of ontogenesis The prevalence is estimated to be one in every 8,500 Chromosomal anomalies are often associated live births. It is equally common in males and with PRS. It is classically associated with several females. Nearly half of the patients have an under - Mendelian syndromes. Non-syndromic PRS may lying syndrome diagnosis. Developmental delays be etiologically related to dysregulation of both are more prevalent in these syndromic patients. SOX9 and KCNJ2. Etiology and pathogenesis Clinical presentation Three pathophysiological theories exist to explain Micrognathia is obvious on the initial examina - the occurrence of micrognathia: tion of the majority (91.7%) of these infants. It is 1. The mechanical theory is the most widely characterized by the retraction of the mandible by accepted. It has been postulated that the 10 mm to 12 mm with respect to the maxilla. The in utero constraint of mandibular growth mandible has a small body, an obtuse genial angle results in failure of the tongue to descend. and the condyle is posteriorly located. The jaw This prevents fusion of the palatal shelves index is defined as the alveolar overjet multiplied resulting in a cleft palate. by the maxillary arch divided by the mandibular The Canadian Journal of CME / September 2008 49 Pierre Robin Sequence Figure 1. Patient with Pierre Robin Sequence (PRS) demonstrating the small mandible (frontal view). arch. This index helps to objectify mandibular Figure 2. Patient with PRS demonstrating the small mandible and growth. The growth of the mandible usually receding chin (lateral view). catches up during the first year—the child attains a normal profile by approximately age five to six to suck. Poor bolus propagation is another aggra - years. vating factor. Glossoptosis is another presenting abnormali - Failure to thrive (FTT) is common. Feeding ty which is seen in approximately 70% to 85% of difficulties, hypoxemia, respiratory distress with the children. Macroglossia and ankyloglossia are increased work of breathing, augmented caloric relatively rare findings, which are reported in needs and prematurity are amongst the various 10% to 15% of the cases. Palatal clefting can be contributing factors. In addition, associated u-shaped or v-shaped and can include the soft pathologies such as gastroesophageal reflux and palate only or both the soft and hard palates. The recurrent respiratory infections further exacer - incidence varies from 14% to 91%. Occasionally, bate the FTT. it may present as a bifid or double uvula or as an The speech of the patients with cleft palate is occult submucosal cleft. characterized by an abnormal nasal air emission due Respiratory problems at birth are often part of to velopharyngeal insufficiency (VPI). VPI decreas - the sequence. Airway obstruction is most evident es oral volume and leads to disarticulations. in the supine position, especially during sleep. The most common otic anomaly is otitis media, Obstructive sleep apnea may also occur. The which occurs in 80% of the cases followed by resultant hypoxia and hypercapnia can lead to auricular anomalies. Conductive hearing loss is right heart failure. PRS is associated with laryn - found in approximately 60% of the patients with gomalacia in 10% of cases. external auditory canal atresia in only 5% of the Feeding difficulties in these patients are char - cases. Anomalies of the ossicles as well as defects acterized by low oral intake, feeding time usual - of the inner ear, such as large vestibular aqueduct ly of > 30 minutes, fatigue, coughing, gagging and aplasia of the lateral semicircular canals, can and vomiting during feeds. Upper airway also be found. Dental and philtral anomalies are obstruction leads to these problems by causing found in a third of the cases. incoordination of sucking and swallowing. In Ocular anomalies have been reported in a addition, the cleft palate inhibits the creation of third of the cases, including esotropia and con - sufficient negative intraoral pressure necessary genital glaucoma. CV findings such as benign 50 The Canadian Journal of CME / September 2008 Pierre Robin Sequence U-shaped cleft palate V-shaped cleft palate Figure 3. Inverted u-shaped and v-shaped cleft palate seen in patients with PRS. murmurs, pulmonary stenosis, patent foramen and cleft palate. In cases of polyhydramnios, it is ovale and ventricular septal defect have been recommended to further examine the facial profile documented. Musculoskeletal defects are the and palate. Cardiac evaluation and karyotyping are most frequent systemic manifestations which can also suggested. Prenatal telomeric screening is affect the upper and lower limbs as well as the another test that is recommended. vertebral column. Some examples include syn - dactyly, hyperextensible joints, club feet, coxa Prognosis varus or valgus, flexure contractures, scoliosis and sacral agenesis. Genitourinary conditions such as After birth, there is a potential for rapid undescended testes are also associated with PRS. mandibular “catch-up” growth usually within the Central nervous system defects are observed first year. However, this growth depends on the in 50% of the cases. Mental retardation has been underlying cause of the underdevelopment. seen in these children. A significant proportion Despite initial feeding difficulties, most patients of PRS children suffer from a coexisting syn - are able to tolerate an oral diet without airway dis - drome, most frequently the Stickler and velocar - tress by three-years-of-age. Successful decannula - diofacial (Shprintzen) syndrome. tion for those who underwent tracheostomy is also achieved by this age. Prenatal diagnosis Improved coordination of the velopharyngeal muscles results in a decrease in airway obstruc - Prenatal ultrasonography can be used in the tion. The speech prognosis of PRS in non-syn - early identification of this sequence. The main sono - dromic patients appears to be similar to those graphic findings are micrognathia, polyhydramnios with concomitant syndromes. In general, death from PRS is thought to be the result of the poorly controlled combined effects Dr. Shinghal is a Medical Student, Université de Montréal, Montreal, of obstructive apnea and failure to thrive. Quebec. However, PRS is etiologically heterogeneous and the prognosis depends on the cause. Diagnostic subgroups based on associated syn - Dr. Tewfik is a Professor of Otolaryngology, McGill University, dromes help in evaluating the severity of the con - Montreal, Quebec. dition. Isolated PRS patients usually have a bet - ter prognosis. The Canadian Journal of CME / September 2008 51 Pierre Robin Sequence Conservative treatment FISH (fluorescent in-situ hybridization) tech - In the majority of patients, conservative manage - niques should therefore be practiced in all chil - ment with close observation and follow-up is dren with PRS. The severity of the condition is successful. Isolated PRS patients usually respond variable with a more difficult course in the syn - more favourably to the conservative approach. dromic variant. As the mandible grows with Prone positional therapy has proved to be age, the problem usually resolves. Conservative highly efficient in airway management. Oral treatment is effective and the surgical options airway placement, laryngeal mask, nasopharyn - are reserved for more severe cases. Treatment geal stenting and short-term intubation (less modalities include prone/lateral positioning, than two weeks) are other options in case posi - nasopharyngeal and endotracheal intubation, tioning is inadequate. Intubation is often diffi - glossopexy (including tongue-lip adhesion), tra - cult due