Séquence Pierre Robin

Synonyms: Pierre Robin syndrome (PRS), Pierre Robin anomaly/anomalad, Pierre Robin malformation (PRM) complex, Robin sequence, Robin complex

Related conditions - these may display features of the malformation: Stickler's syndrome, velocardiofacial syndrome, Catel-Manzke syndrome, Treacher Collins' syndrome, Nager syndrome, spondyloepithelial dysplasia congenita, campomelic dysplasia.

This condition was originally considered to be a single clinical entity but is now thought to represent a particular outcome of an abnormal developmental process, associated with a range of clinical entities and is more commonly referred to as Pierre Robin sequence (PRS). Pierre Robin, a French dental surgeon (1867-1950), is identified with the sequence/syndrome due to his role in the early part of the twentieth century, describing the typical triad of features and his many articles on its management. The typical features of PRS are:

• Micrognathia or retrognathia (small or retracted mandible).

• Cleft palate (classically U-shaped but V-shaped may occur, usually without cleft lip).

• Glossoptosis (implying a relatively large tongue. In reality, the tongue may be normal size or small, so upper airway obstruction may be substituted for this feature).

It is called a sequence because the mandibular abnormality sets off a sequence of events in the uterus, leading to the other deformities.The aetiology of the sequence is not fully understood and pathogenesis is thought to be multifactorial. The mandibular deformity either results from an inherent growth problem which may be genetic, syndromic (part of a syndrome) or is deformational where intrauterine growth of the mandible is restricted.¹Subtypes are recognised:²

• Isolated PRS (iPRS) - 40%

• Syndromic PRS (a syndrome plus PRS) - 25%

• Unique PRS (unique anomalies plus PRS) - 35%

It has been linked with deletions on chromosome 2 that are known to be associated with palatal abnormalities and some cases may have a Mendelian genetic basis that is, as yet, unclear. An inherited translocation defect has been identified in one Pierre Robin family.³Candidate genes and loci are under investigation.⁴

Épidémiologie

Incidence

PRS is a rare condition. A German prospective study reported an incidence of 12.4 per 100,000 live births.⁵

Présentation

• With the increasing routine use of antenatal ultrasound, diagnosis is frequently before birth - based on identification of micrognathism or retrognathism and glossoptosis. This may be complimented by MRI.⁶

• The craniofacial abnormalities are usually plainly evident at birth, if not diagnosed previously.

• Neonates with severe micrognathia present as emergencies at birth with significant respiratory obstruction, requiring a nasopharyngeal airway or intubation.

• Affected babies are at risk of obstructive sleep apnoea. Unrecognised or untreated airways obstruction may lead to chronic hypoxia and cerebral impairment, failure to thrive and cor pulmonale.

• The most common early problem is feeding difficulties, as the cleft palate prevents enough negative pressure to feed effectively.

• Careful examination for other somatic abnormalities, including examination of the eyes and ears, may indicate the presence of the malformation as one of the related syndromes.

Diagnostic différentiel

• Syndrome d'alcoolisme fœtal.

• Stickler's syndrome: PRS plus severe myopia, retinal detachment and blindness with abnormal epiphyseal development due to alpha-1 collagen II polypeptide mutation.⁷

• Velocardiofacial syndrome: 22q deletion with neuropsychiatric impairments and cardiac abnormalities.⁸

• Other rare syndromes that display the malformation.

Enquêtes

• Pulse oximetry, arterial or capillary blood gases

• Bone radiographs

• Genetic assessment

• Ophthalmological/auditory assessment

Gestion

Neonatal

• Babies presenting at birth with significant respiratory obstruction require urgent attention from someone experienced with difficult paediatric airways.

• Feeding can be problematic due to the cleft palate and posterior tongue. Where nursing is not possible, formula or breast milk can be provided via a specialist bottle and teats that are available for children with cleft palates e.g. squeeze bottles with different teats. Medical professionals should refer to neonatal feeding therapists or speech and language therapists for support. Positioning (in the prone position) is also vital.

• The multidisciplinary team involved is often large (incorporating paediatricians, ENT and plastic surgeons, dentists, orthodontists, nurses, speech therapists, audiologists and social workers) but ensures the most comprehensive care plan.

Airways

Micrognathia may improve in 'non-syndromal' PRS as catch-up growth occurs and no intervention beyond positioning is required. In one study, 61% of patients only required positioning. 59% of patients who failed to respond to positioning required a nasopharyngeal airway and 12% required short-term endotracheal intubation. The remainder required surgical treatment.⁹

Surgical options
These include:

• Distraction osteogenesis of the mandible (where the mandible is progressively elongated).

• Tongue-lip adhesion/glossopexy (connecting the tongue to the lower lip to improve the airway - later reversed).

One study found that distraction osteogenesis was superior to tongue-lip adhesion/glossopexy for the treatment of non-syndromic PRS when judged by the outcomes of oxygen saturation, apnoea/hypopnea index and tracheostomy.¹⁰

The EXIT (ex utero intrapartum therapy) procedure has been developed to treat a number of abnormalities affecting the fetal airway. Basically this involves performing a caesarean section, leaving the baby attached to the placenta, whilst surgical correction is undertaken.¹¹

Feeding

• If feeding is problematic, a feeding tube may be required.

• Palatal repair is usually carried out at 6-12 months.¹²

L'audition

Early audiological assessment is important as tympanostomy tube placement to ensure adequate speech and language development.⁹

Pronostic

A degree of palatal dysfunction and speech defect is to be expected in the long term. However, overall, the outlook is good but dependent on the presence or absence of other syndromes and their complications. By the age of 3, most children with PRS are taking an oral diet and do not have significant airways obstruction.²