The posterior nasal apertures are also called the choanae. If you've ever stared at a skull in anatomy lab and wondered why those two oval openings at the back of the nasal cavity have a special name — this is it. But choanae. Sounds like a Greek goddess. It's actually Greek for "funnels Easy to understand, harder to ignore..
Most people never think about them. But air just moves. But if you're a med student, an ENT resident, a speech-language pathologist, or just someone who likes knowing how the body actually works — these two holes matter more than they look That's the part that actually makes a difference..
What Are the Choanae
The choanae are the paired openings that connect the nasal cavity to the nasopharynx. Posteriorly, the choanae are the back door. Anteriorly, you've got the piriform aperture — the bony front door of the nose. Each one is bounded by bone and soft tissue: the body of the sphenoid bone above, the vomer medially, the medial pterygoid plate laterally, and the horizontal plate of the palatine bone below.
In adults, each choana measures roughly 20–25 mm vertically and 10–15 mm transversely. They're not round. They're oval, taller than they are wide, and they sit at the junction where the nasal cavity becomes the nasopharynx.
Why "Choanae" and Not Just "Posterior Nares"
"Posterior nares" is the older term. So Choanae specifies the funnel-shaped openings at the back of the nasal cavity. It's more precise. Worth adding: "Nares" just means nostrils — anterior or posterior. Say it out loud: koh-AH-nah. You'll still see it in some textbooks. Still, the singular is choana. But choanae is the Terminologia Anatomica standard now. Feels good Surprisingly effective..
Why They Matter More Than You Think
Airflow. That's the obvious one. That's why every breath you take through your nose passes through the choanae. But they're also a choke point — literally and clinically Easy to understand, harder to ignore..
The Air Conditioning Chamber
Before air hits the choanae, it's been warmed, humidified, and filtered by the nasal mucosa. The turbinates do the heavy lifting. By the time air squeezes through the choanae, it's close to body temperature and near 100% humidity. That's not trivia. Here's the thing — that's lung protection. Bypass the nose — mouth breathe — and you're sending cold, dry, unfiltered air straight to your trachea. Your lungs notice.
The Drainage Highway
Mucus from the frontal, maxillary, anterior ethmoid, and sphenoid sinuses all drains into the nasal cavity. Practically speaking, where does it go? That's why posteriorly. Through the choanae. Practically speaking, into the nasopharynx. That's why swallowed. Cleared. If the choanae are narrowed or blocked, that drainage backs up. Sinusitis. Plus, post-nasal drip. Chronic cough. The choanae are the exit ramp for everything your sinuses produce.
The Eustachian Tube Neighbor
The pharyngeal opening of the Eustachian tube sits just lateral to the torus tubarius, which forms the lateral wall of the nasopharynx right next to the choanae. Inflammation, adenoid hypertrophy, or tumors in this region can mess with middle ear ventilation. Otitis media with effusion in kids? Often starts with choanal-level obstruction.
How They Develop — And What Goes Wrong
Embryology in 60 Seconds
The nasal cavities start as olfactory placodes. They invaginate, form nasal pits, then nasal sacs. The oronasal membrane separates them from the oral cavity. That membrane ruptures around week 7–8, creating the primitive choanae. But initially, they open into the oral cavity. As the palate forms — primary palate first, then secondary palate — the choanae shift posteriorly and superiorly, ending up above the soft palate in the nasopharynx No workaround needed..
Choanal Atresia: The Classic Disaster
This is the big one. Now, failure of the oronasal membrane to rupture. Or failure of recanalization. Result: bony or membranous blockage of one or both choanae Easy to understand, harder to ignore..
- Unilateral (more common, ~60%): Often missed at birth. Baby breathes fine through the other side. Presents later with unilateral nasal discharge, recurrent sinusitis, or feeding difficulties.
- Bilateral: Neonatal emergency. Newborns are obligate nasal breathers. They can't breathe. They turn cyanotic when feeding, pink up when crying. That's the classic presentation. Intubate. Stabilize. Surgery later.
Choanal atresia occurs in roughly 1 in 7,000 live births. And it's associated with CHARGE syndrome (Coloboma, Heart defects, Atresia choanae, Retarded growth, Genital anomalies, Ear anomalies). If you see it, look for the rest.
Choanal Stenosis
Not fully blocked — just narrowed. Even so, acquired causes: trauma, surgery (overzealous turbinectomy, septoplasty), radiation, granulomatosis with polyangiitis, syphilis (yes, still happens), chronic infection. Because of that, can be congenital or acquired. Symptoms: chronic nasal obstruction, hyponasal speech, difficulty with CPAP tolerance.
Common Mistakes / What Most People Get Wrong
"The Choanae Are Just Holes in Bone"
No. That's functional stenosis. Day to day, the posterior ends of the inferior and middle turbinates, the septum, the torus tubarius — all of these can encroach. The bony boundaries are fixed, but the functional choana includes the soft tissue. A deviated septum crashing into the medial wall of the choana? Don't just measure bone on CT The details matter here..
"Bilateral Choanal Atresia Is Always Obvious at Birth"
It should be. But sometimes it's missed. Which means baby gets intubated for "respiratory distress," extubated, turns blue again, re-intubated. Someone finally passes a catheter or does a mirror test. By then, the baby's had multiple hypoxic episodes. If a newborn can't maintain saturation while feeding but is fine crying — check the choanae before you extubate It's one of those things that adds up..
"Choanal Atresia Repair Is Just Punching a Hole"
Endoscopic repair is standard now. But restenosis rates are real — 10–30% depending on technique. Consider this: stenting helps. Mitomycin C helps. But the real key? Preserving mucosa. If you strip the raw bone on both sides, they scar together. Leave mucosal flaps. Rotate them. That's what keeps it open.
"Adults Don't Get Choanal Problems"
Wrong. Acquired choanal stenosis is underdiagnosed. Post-radiation fibrosis. In practice, autoimmune disease. Prior sinonasal surgery. These patients show up with "chronic sinusitis" that never clears, or "CPAP intolerance," or "nasal obstruction unresponsive to sprays.Here's the thing — " Scope them. Look at the back. Measure. You'll find it.
It sounds simple, but the gap is usually here.
Practical Tips / What Actually Works
For Students: How to Find Them on a Skull
Don't just stare at the front. Look at the base. Practically speaking, trace it from the piriform aperture, along the floor, up and back. The choanae are right there — above the hard palate, behind the maxilla, medial to the pterygoid plates. Stick a pipe cleaner through. In practice, that's the nasal cavity. Flip the skull. The exit is the choana That's the whole idea..
For Clinicians: The Mirror Test (Still Works)
Cold metal mirror, warmed slightly. Day to day, hold under the nose. Fogging = airflow. No fogging on one side?
Choanal atresia can be unilateral or bilateral. Day to day, unilateral cases are often asymptomatic unless there's associated nasal obstruction or sinus disease. Bilateral choanal atresia presents shortly after birth when the amniotic fluid is no longer present to keep the nasal passages patent. Newborns with bilateral choanal atresia may present with severe respiratory distress, poor feeding, and cyanosis.
Counterintuitive, but true Small thing, real impact..
Imaging Modalities
CT scans provide excellent bony detail and are considered the gold standard for evaluating choanal anatomy. MRI is useful for assessing soft tissue involvement, especially in cases of suspected malignancy or granulomatous disease. In children, ultrasound has been used as a screening tool due to its accessibility and lack of radiation exposure That's the part that actually makes a difference..
Surgical Approach
Transnasal endoscopic approach is the preferred method for both diagnosis and treatment. It allows direct visualization and precise intervention without external incisions. In cases of complex anatomy or prior failed surgeries, combined endoscopic and external approaches may be necessary.
Postoperative Care
Postoperative monitoring focuses on preventing restenosis through appropriate stenting and mucosal protection. Patients should be observed for signs of bleeding, infection, or re-obstruction. Follow-up imaging is typically performed at 3 months post-surgery to assess patency Simple, but easy to overlook..
Conclusion
Choanal atresia and stenosis represent a spectrum of conditions that demand careful attention from clinicians across various specialties. Also, early recognition and appropriate management can significantly improve outcomes for affected patients. Still, whether dealing with congenital anomalies or acquired strictures, understanding the underlying pathophysiology and employing modern surgical techniques are essential. Continued education and awareness of these often-overlooked conditions will ensure better care for patients presenting with nasal obstruction or respiratory compromise.
