Ans. b (Choanal atresia). (Ref. Diseases of ENT, PL Dhingra, 3rd ed., 78, 210, 510)# Persistant bucconasal membrane leads to choanal atresia.Choanal atresia# Is a autosomal recessive trait in which the posterior choanae unilaterally or bilaterally fail to develop properly.# Persistent bucconasal membrane is the basic etiology.# Occurs in 1 in 5,000 births; more common among girls (2:1)# Unilateral > bilateral atresia.# Because newborns are obligate nose breathers, bilateral atresia is immediately apparent as respiratory distress.# Characteristics is the history or failure to pass a rubber catheter or nasogastric tube into the pharynx.# Symptoms of choanal atresia include failure to thrive due to poor feeding and mucoid nasal discharge.# The presence of choanal atresia can be confirmed with visualization of retention material in the posterior part of the nose on a lateral radiograph with the patient in the supine position.# Anatomic characterization of the deformity with CT can be important for planning surgical procedures.# Surgical treatment methods for membranous atresia include puncture of the choanal membrane and placement of a stent for 6 weeks.# If bony atresia is present, the bony wall can be taken down transnasally with microsurgical techniques followed by placement of a stent.# When suboptimal resection for atresia or choanal stenosis occurs, transpalatal repair at 3-4 years age is advised.# The septum usually deviates to the affected side; however, more posterior examination shows atresia.# Transpalatal repair is being replaced by endoscopic techniques of repair of atresia in children and adults.