FCPS TOACS Mock Test · Pierre Robin Sequence (PRS)

❓ Q1. Describe the findings in the image. What is the most likely diagnosis? Define the classic triad.

✅ Model Answer:
• Findings: Micrognathia (small, recessed mandible), glossoptosis (posteriorly displaced tongue – inferred from airway obstruction), U-shaped cleft palate.
• Diagnosis: Pierre Robin Sequence (PRS).
• Classic triad: Micrognathia + Glossoptosis + Cleft palate (U-shaped).

❓ Q2. Why is Pierre Robin called a 'sequence' rather than a syndrome? Explain the pathogenesis.

✅ Model Answer:
• Sequence: Chain of events triggered by a single primary defect – mandibular hypoplasia (micrognathia).
• Secondary events: Small mandible displaces tongue posteriorly (glossoptosis) → posterior tongue prevents palatal shelf fusion → U-shaped cleft palate → airway obstruction and feeding difficulties.
• Isolated PRS (non-syndromic) vs Syndromic PRS (40-50% – Stickler, 22q11.2 deletion, Treacher Collins).

❓ Q3. Explain the mechanism of airway obstruction in Pierre Robin Sequence. Why does prone positioning help?

✅ Model Answer:
• Mechanism: Small recessed mandible allows tongue to fall posteriorly into pharynx (glossoptosis) → upper airway obstruction, especially during inspiration (negative pharyngeal pressure pulls tongue against posterior pharyngeal wall).
• Prone positioning helps because gravity pulls tongue anteriorly (forward) and mandible forward, relieving obstruction.
• Other measures: Nasopharyngeal airway, tongue-lip adhesion, mandibular distraction.

❓ Q4. What is your immediate management for this newborn with respiratory distress due to PRS?

✅ Model Answer:
1. Positioning: Prone or lateral (avoid supine).
2. Monitor oxygenation – pulse oximetry.
3. Oxygen supplementation if hypoxemic.
4. Nasopharyngeal airway (NPA) – soft suction catheter (size 8-10 Fr) through nose to bypass tongue obstruction.
5. NG/OG tube for feeding if unsafe oral feeding.
6. Consider CPAP if NPA insufficient.
7. Intubation if severe apnea or desaturation (difficult airway due to micrognathia).
8. Transfer to tertiary NICU with pediatric surgery/ENT/craniofacial team.

❓ Q5. What feeding problems occur in Pierre Robin Sequence? How are they managed?

✅ Model Answer:
• Problems: Glossoptosis → airway obstruction during feeding; cleft palate prevents suction; poor suck-swallow-breathe coordination; fatigue, aspiration risk.
• Management: Positioning (prone/side-lying), special nipples (Haberman, Pigeon), NG tube feeding if inefficient, gastrostomy tube for severe failure, treat GERD, palatal obturator (rare), feeding therapy.

❓ Q6. What surgical procedures are available for severe upper airway obstruction in PRS? Describe tongue-lip adhesion and mandibular distraction.

✅ Model Answer:
• Tongue-lip adhesion (TLA): Suture ventral tongue to lower lip to pull tongue forward. Temporary (released 3-6 months). Effective for moderate obstruction.
• Mandibular distraction osteogenesis (MDO): Surgical osteotomy of mandible with distraction devices, gradually lengthen mandible (1 mm/day for 2-3 weeks). Preferred for severe obstruction. Permanent advancement, improves airway and feeding.
• Tracheostomy: Reserved for failure of MDO or severe anomalies.

❓ Q7. How is the cleft palate managed in PRS? When is cleft palate repair performed?

✅ Model Answer:
• Cleft palate repair not urgent – priority is airway and feeding.
• Timing: 9-12 months of age (after airway stable, feeding established, adequate weight >7-8 kg). Earlier repair contraindicated (high risk of postoperative airway compromise).
• Procedure: Furlow palatoplasty or other techniques.
• Preoperative: Sleep study to ensure no significant residual OSA.

❓ Q8. How do you differentiate isolated (non-syndromic) PRS from syndromic PRS? Which syndromes are commonly associated?

✅ Model Answer:
• Isolated PRS (50-60%): No other dysmorphic features, normal development.
• Syndromic PRS (40-50%): Associated anomalies – dysmorphic facies, eye anomalies, hearing loss, cardiac defects, developmental delay.
• Most common: Stickler syndrome (COL2A1/COL11A1/2) – myopia, retinal detachment, hearing loss, arthropathy. Also 22q11.2 deletion, Treacher Collins, fetal alcohol syndrome.

❓ Q9. Why is an ophthalmology examination and hearing assessment mandatory in a newborn with PRS?

✅ Model Answer:
• Ophthalmology: Stickler syndrome (highly associated) causes high myopia – most common cause of retinal detachment in children. Early detection and prophylactic laser can prevent blindness.
• Hearing assessment: Conductive loss from cleft palate (Eustachian tube dysfunction, otitis media); sensorineural loss in Stickler, 22q11.2 deletion, Treacher Collins. Early intervention critical for speech/language development.
• Recommendations: Baseline within first few months; long-term follow-up.

❓ Q10. What is the long-term prognosis for a child with isolated PRS? What multidisciplinary follow-up is required?

✅ Model Answer:
• Excellent prognosis – mandibular catch-up growth, normal airway, feeding, speech.
• Multidisciplinary team: Plastic surgery (palate repair), ENT (airway, grommets), speech therapy, orthodontics, audiology, ophthalmology (retinal exams), pulmonology (OSA), feeding therapy, genetics, psychology.

❓ Q11. What respiratory monitoring is required for an infant with PRS after initial stabilization? When is polysomnography indicated?

✅ Model Answer:
• Inpatient: Continuous pulse oximetry, capnography, cardiorespiratory monitoring, frequent clinical assessment.
• Polysomnography indications: Diagnose OSA severity before discharge, assess residual obstruction after airway surgery, before cleft palate repair, in older children with OSA symptoms.

❓ Q12. What genetic testing is indicated in PRS? What is the recurrence risk for future siblings?

✅ Model Answer:
• Genetic testing: Chromosomal microarray (22q11.2 deletion), Stickler gene panel (COL2A1, COL11A1/2), FISH for 22q11.2.
• Recurrence risk: Isolated PRS <1-2%; Stickler syndrome (autosomal dominant) – 50% if parent affected; 22q11.2 deletion – 50% if parent carries deletion; Treacher Collins – 50%. Genetic counseling essential.

⚕️ FCPS Paediatrics TOACS · Mock Test