CNPAS: A Differential to Choanal Atresia

Abstract

A case of 7 day old male child, born at 36 weeks, presented with feeding difficulties, hypothermia and failure to thrive. After clinical examination to rule out any gross congenital anomalies, CT scan was done which was suggestive of pyriform aperture stenosis. It was surgically dilated and stented successfully.

Introduction

Congenital nasal pyriform aperture stenosis (CNPAS), first clinically described in 1988, arises due to bony overgrowth of nasal process of maxilla [1]. The pyriform aperture is the narrowest part of the nasal airway and so even minimal reduction in diameter here can cause significant problems [2]. It typically presents with clinical features that may mimic posterior choanal atresia, and it is important to differentiate it from latter as there are differences in clinical management of both the conditions [3, 4].

Case Report

A 7 day old male child, born prematurely at 36 weeks of gestation to nonconsanguineous parents, presented with complaints of feeding difficulty, hypothermia and failure to thrive. There was a history of respiratory distress and cyanosis at birth. The antenatal period was uneventful. Clinical examination of the child did not show any external dysmorphic features. The child was noted to have mouth breathing. There was no evidence of cleft palate. A no. 6 infant feeding tube could not be negotiated through both the nostrils.

A CT scan of the paranasal sinuses was performed which showed severe narrowing of anterior and mid nasal cavity with decreased bony width (Fig. 1). One prominent central incisor was noted (megaincisor). Hard palate was triangular in shape. Anterior bony width on CT scan was 7 mm, hence a diagnosis of CNPAS was made.

Fig. 1.

CT scan of paranasal sinus in axial and coronal section showing bony overgrowth of medial process of maxilla marked by arrows

It was decided to give a pacifier trial before embarking on any operative intervention. Accordingly the child was extubated on day 10 of life and put on pacifier (Fig. 2). The patient maintained saturation for around 36 h but had multiple episodes of respiratory distress in between and had to be intubated again on day 12 of life.

Fig. 2.

Patient with pacifier which acted as a oropharyngeal airway

Hence, we decided to surgically dilate the stenosis. The patient was operated under general anaesthesia on day 14 of life, in which under direct visualization, both the nasal cavities were dilated serially using Hegar’s dilator from no. 2.5 to 5.0. Endotracheal tube of size 3.5 was used in left nasal cavity as a stent and was fixed at mark 3.5 and of size 2.5 was used in right nasal cavity as a stent and was fixed at mark 4.0 using adhesive tape (Fig. 3).The position of the stents was confirmed endoscopically via the oral cavity. The patient tolerated the procedure well and was extubated on table.

Fig. 3.

At the end of surgery, 2.5 no. endotracheal tube in right nasal cavity and 3.5 no. in left nasal cavity were used as stents, and were kept for 2 weeks

Both the stents were removed after 2 weeks. The patient was able to maintain saturation off oxygen and had a good air blast from both nasal cavities. The patient is under regular follow up and has no complaints thereof.

Discussion

Nasal airway obstruction in newborns can lead to respiratory distress as they are obligate nasal breathers [2]. Most common cause of congenital nasal obstruction in newborns is choanal atresia, which occurs at incidence of 1 in 7000. CNPAS has much rarer—approximately 1 in 70,000 [2].

The pyriform aperture is the narrowest part of normal nasal airway. CNPAS is caused by narrowing of anterior bony nasal apertures [1]. The clinical presentation can be variable, with respiratory distress at birth, or a cyanosis relieved by crying, or feeding difficulties [2, 5, 6].

Two theories about the pathogenesis of CNPAS exist: (a) deficiency of the primary palate, associated with a triangular hard palate, and (b) bony overgrowth in the nasal process of the maxilla, with a normal-shaped palate [1]. Our patient had a triangular hard palate, and in addition, exhibited a single central maxillary megaincisor [SCMI]—these findings can be explained by the hypothesis of a primary palatal deficiency and strongly suggest the diagnosis of CNPAS [4]. There are two forms of CNPAS: an isolated form and a form that is associated with other anomalies including a midface dysostosis with associated central nervous system and endocrine abnormalities [7].

The diagnosis of pyriform aperture stenosis can be made accurately with a CT scan, by obtaining thin (1.5–3.0 mm), contiguous axial sections in a plane parallel to the anterior hard palate. It is important to demonstrate the narrowing on contiguous sections, as apparent narrowing may be caused by oblique imaging [1]. The normal range of width of the pyriform sinus in the age group of 0–6 months is 8.8–17.2 mm [median width = 13.5 mm] [8]. In full term infant, each pyriform aperture width less than 3 mm, or a whole pyriform aperture width less than 8 mm, in a term infant, confirms the diagnosis of CNPAS [4]. Our patient had a pyriform aperture width of 7 mm.

Once the diagnosis of CNPAS has been established, conservative treatment is the initial line of management which includes steam inhalation, saline nasal drops, pacifier trial. When conservative management fails, then surgery aimed at widening bony inlet can be performed. The surgical approach can either be transnasal dilatation of stenosis (if width of stenosis is more than 5 mm) [5] or a sublabial approach to drill the pyriform aperture (if width of stenosis is less than 5 mm) [5]. In our case, since the pyriform aperture width was 7 mm, we decided to attempt dilatation of stenosis which is lesser morbid as compared to the sublabial approach of drilling pyriform aperture. This is in contrast to the treatment of posterior choanal atresia which is treated surgically [9].

Conclusion

This case has been presented to increase the awareness about this rare entity, to highlight the importance of recognizing the typical findings of CNPAS in cases undergoing evaluation of nasal airway obstruction and respiratory distress in neonates, and the role of the CT scan in its diagnosis which will help in deciding surgical (dilatation/drilling of pyriform aperture) management.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.