Congenital nasal pyriform aperture stenosis (CNPAS) is a congenital anomaly that is a rare cause of neonatal nasal obstruction. It is definitively diagnosed by CT scan. If respiratory symptoms are severe, surgical intervention is required. If the symptoms are mild to moderate, watchful waiting can be recommended.
36 Repair of Pyriform Aperture Stenosis
Congenital nasal pyriform aperture stenosis (CNPAS) is a congenital anomaly that is a rare cause of neonatal obstruction. It was not clinically described in neonates as a cause of congenital nasal obstruction until 1989. More likely causes of neonatal nasal obstruction are choanal atresia, midnasal stenosis, nasal trauma, cysts, skull base defects (i.e., meningoencephalocele and encephalocele), tumors (rhabdomyosarcoma, hemangioma, glioma, lymphangioma, teratoma), nasopharyngeal mass, and nasal hypoplasia. Birth trauma resulting in septal displacement, hematoma or displaced nasal bone fractures can also cause neonatal nasal obstruction and should be differentiated from CNPAS.
The pyriform aperture (PA) is a pear-shaped bony inlet bounded by nasal bone superiorly, nasal process of maxilla laterally, and horizontal process inferiorly. The PA is the narrowest most anterior bony portion of nasal airway. CNPAS most often occurs bilaterally and is typically characterized by bony overgrowth or medial position of the nasal processes of the maxilla. This is thought to occur during the fourth month of fetal development.
Infants are considered obligate nasal breathers until the first few months of life; therefore any narrowing at the PA, which is already the most anterior and narrow portion of the nose, can significantly compromise babies’ ability to breathe. Typically oral ventilation appears between 3 and 6 months of age.
CNPAS classically presents with episodic apnea and cyclical cyanosis, sudden total airway obstruction relieved by crying, tachypnea, noisy breathing, and inability to feed. Signs and symptoms often occur immediately after birth. But the degree of narrowing, in combination with any additional comorbidities, dictates severity of presentation, and some patients may present later in infancy.
CNPAS may be an isolated anomaly or may be associated with other midline anomalies such as central incisor (▶ Fig. 36.1) or holoprosencephaly (HPE). HPE is a brain malformation resulting from incomplete cleavage of the prosencephalon into right and left hemispheres. CNPAS may also be associated with craniofacial anomalies in 40% of cases. Other associated comorbidities include shallow sella turcica, craniopharyngeal canal, submucous cleft palate, or hypoplastic maxillary sinuses.
Arlis and Ward identified an association with single maxillary-mega incisor (SMMI) and considered CNPAS to be a developmental field defect along the HPE spectrum or a midfacial dysostosis with associated endocrine and central nervous system abnormalities. HPE usually includes facial dysmorphisms such as ocular hypotelorism, midline cleft lip and/or flat nose, cerebral malformations, learning disabilities, arrhinencephaly, agensis of corpus callosum, hypopituitarism, and a single maxillary central incisor. Chromosomal analysis and magnetic resonance imaging (MRI) to assess hypothalamic–pituitary–thyroid–adrenal axis and brain are indicated when HPE abnormality is suspected. Endocrinology, electrolyte evaluation, and a craniofacial and genetics workup may also be useful.
Diagnosis can be made via clinical exam and computed tomography (CT) findings. Exam will reveal narrow anterior nasal fossae and inability to pass 5 Fr suction catheter or 1.9 mm endoscope. Recommended CT scan should have contiguous thin sections (1–3 mm thick) through midface from palate to orbital roof. CT scan often reveals narrowed anterior nasal inlet and bony overgrowth of maxillary nasal processes. There is some controversy over exact diagnostic measurements, but it is generally accepted that PA width less than 11 mm at the level of the inferior meatus in a term infant is diagnostic of CNPAS. Brown et al reported CNPAS should be diagnosed when maximum transverse diameter of each aperture is </=3 mm in term neonates and in preterm neonates. Chinwuba et al suggested nasal airway <2 mm is diagnostic. More recently, there has been an increasing diagnostic role for 3D craniofacial CT scan. 3D CT is viewed by some as a better diagnostic tool for CNPAS because it provides more spatial information and preoperative planning information than 2D CT. With 3D CT it is easier to measure distance between the bilateral nasal processes of the maxilla, which can be defined as the interprocess distance (IPD). Lin et al reviewed 40 patients retrospectively and developed a growth curve for the PA. This curve was a cubic curve with two inflection points at 42.9 and 70.9 months and resulted in a formula to estimate growth of IPD. They found no difference in initial IPD between patients who required surgery and those who did not. Further, when IPD fails to progressively increase with age, more aggressive interventions may need to be considered and treatment may progress from observation to conservative management or conservative management to surgical intervention.
Treatment will depend on severity of symptoms. Most authors agree that first-line conservative management should be attempted when possible. This includes use of a McGovern nipple or oral airway with appropriate monitoring in an intensive care unit (ICU) setting. Additional management may include humidification, gentle suctioning, topical steroid and decongestant drops, and gavage feeding if necessary. Some studies suggest that if patients are able to tolerate conservative management, their nasal airway is likely to improve with growth, typically within 6 months of life. The ability to pass a 5 Fr suction catheter is thought to predict success of nonsurgical management. Ideally, surgery should be delayed when possible until the “rule of 10” is met and the infant is at least 10 lbs, 10 weeks of age, and has a hemoglobin of 10 g. This of course is not always possible. Moreddu et al proposed an algorithm for workup and treatment of CNPAS (▶ Fig. 36.2).
Indications for surgery include obstruction refractory to medical therapy, severe degree of obstruction, failure to thrive, and severe obstructive sleep apnea. Contraindications include overall poor prognosis of patient or an unsuitable operative candidate. Since its first clinical description in 1989, surgery has evolved from simple transnasal dilation to sublabial and submucosal approaches. Special instruments typically required are otologic instruments such as small diamond burr drills and a microscope with 300-mm F lens. Other concomitant airway surgeries, neurologic deficits, and other craniofacial anomalies can limit surgical success and prolong hospital course.