Deviated Nasal Septum (DNS)
ENT · Nose & PNS · lean revision notes
Deviated Nasal Septum (DNS)
A deviated nasal septum is a deflection of the bony or cartilaginous nasal septum away from the midline, producing asymmetry of the two nasal cavities. It is one of the commonest structural causes of nasal obstruction and an extremely favourite ENT topic in NEET PG because of its tidy facts: incision eponyms (Killian, Freer), the SMR-versus-septoplasty distinction, compensatory turbinate hypertrophy, and the strict minimum age for surgery.
Definition & relevant anatomy
The nasal septum is a midline partition dividing the nasal cavity into right and left halves. A perfectly straight septum is the exception rather than the rule — minor deviations are present in the majority of adults and are often asymptomatic. The septum is clinically significant ("deviated") only when the deflection produces symptoms (obstruction, sinusitis, epistaxis) or interferes with adjacent structures.
The septum has three structural components, and knowing them is essential because the type of deviation depends on which part is affected:
| Component | Nature | Contribution |
|---|---|---|
| Septal (quadrilateral) cartilage | Cartilaginous | Anterior part; most mobile |
| Perpendicular plate of ethmoid | Bony | Upper posterior part |
| Vomer | Bony | Lower posterior part |
Additional contributors at the margins: the crest of maxilla and palatine bone (floor), and the nasal spine of frontal bone / nasal crest superiorly. The cartilage sits in a groove (the vomerine groove / maxillary crest); dislocation of the cartilage out of this groove gives the classic anterior caudal dislocation visible at the nasal vestibule.
High-yield: The septal (quadrilateral) cartilage is the part most commonly involved in deviation and the part addressed in septoplasty. The vomer and perpendicular plate of ethmoid are the bony components.
Etiology
Causes are conveniently grouped as traumatic and developmental, with a few special situations.
- Trauma — the single commonest cause overall.
- Birth trauma / moulding during delivery (a recognised cause of neonatal deviation).
- Childhood falls and facial injuries (often forgotten by the patient).
- Adult nasal trauma (sports, road traffic accidents, assault).
- Developmental / racial — disproportionate growth between the bony septal framework and the palate/maxilla. The septum grows faster than the available bony space, so it buckles. This explains deviation in people with no history of trauma.
- Hereditary — familial tendency.
- Mass effect — a polyp or tumour pushing the septum (rare).
- High-arched palate (e.g. in mouth breathers, adenoid facies) restricts the septal base and favours buckling.
High-yield: Trauma is the commonest cause of DNS; developmental disproportion (septum outgrowing the bony framework) is the commonest non-traumatic cause.
Types / classification
Several useful classifications appear in MCQs.
By shape:
- C-shaped deviation — deviation in one plane, to one side.
- S-shaped deviation — deviation in two directions; may obstruct both nasal cavities. Surgically most difficult.
- Spur — a sharp, shelf-like, often bony projection at the junction of vomer with septal cartilage / ethmoid. Spurs may press on the lateral wall and trigger contact headaches and epistaxis (a common bleeding point).
- Thickening / dislocation — caudal cartilage dislocated into one vestibule.
By plane (Mladina-type concept, simplified):
- Anterior (cartilaginous) vs posterior (bony) deviation.
- Caudal dislocation — anteriormost cartilage out of the vomerine groove; cosmetically and functionally important, causes vestibular obstruction.
Cottle's classification of the deviation in relation to nasal valve area is a more advanced concept; for NEET PG, remember that deviation at the nasal valve area produces obstruction disproportionate to its size because the internal nasal valve is the narrowest part of the airway.
Pathophysiology — why it matters
A deviation does three things:
Deviation → narrows one cavity → turbulent airflow & obstruction → compensatory changes on the opposite (wider) side.
The key compensatory change is hypertrophy of the inferior turbinate on the concave (wider) side. Because the airstream is larger on that side, the turbinate enlarges to "fill" the space and humidify air; over time this hypertrophy becomes irreversible. This is why a patient with unilateral deviation may complain of bilateral obstruction — the deviation blocks the narrow side and the hypertrophied turbinate blocks the wide side.
Other consequences:
- Obstruction to sinus ostia / osteomeatal complex → stasis of secretions → recurrent sinusitis.
- Obstruction to the Eustachian tube region / nasopharynx → ear symptoms, recurrent otitis media (especially with posterior deviation).
- Drying of mucosa over the convex prominence and over spurs → crusting, mucosal atrophy, and a fragile vascular surface → epistaxis.
- Mouth breathing → dryness, snoring, contribution to obstructive sleep apnoea.
High-yield: Compensatory hypertrophy of the inferior turbinate occurs on the concave/wider side, opposite the deviation. This is the reason simple septal correction may need to be combined with turbinate reduction.
Clinical features
Symptoms:
- Nasal obstruction — the cardinal symptom; may be unilateral or bilateral (because of compensatory turbinate hypertrophy). Caudal/anterior deviation gives worse obstruction than equivalent posterior deviation.
- Recurrent sinusitis — headache, facial heaviness, post-nasal drip, hyposmia.
- Epistaxis — bleeding from the convex mucosa or from a spur.
- Headache — "contact" or Sluder's neuralgia-type headache when a spur presses on the lateral wall / turbinate (a referred pain via the sphenopalatine ganglion region).
- Anosmia / hyposmia — obstruction of airflow to the olfactory cleft.
- Snoring and OSA, mouth breathing, dry throat.
- Otitis media / Eustachian dysfunction with posterior deviation.
- External nasal deformity if the dorsal/caudal cartilage is involved (a deviated nose, distinct from internal DNS).
Signs (anterior rhinoscopy):
- Visible deflection of the septum, spur, or caudal dislocation in the vestibule.
- Compensatory hypertrophied inferior turbinate on the opposite side.
- Use a vasoconstrictor/decongestant before examination to shrink the mucosa and distinguish a true bony/cartilaginous deviation from mucosal turbinate swelling.
High-yield: Sluder's neuralgia / contact-point headache is classically produced by a septal spur impinging on the lateral nasal wall. Decongesting the nose before rhinoscopy differentiates a structural deviation from reversible turbinate congestion.
Diagnosis & investigation of choice
DNS is largely a clinical diagnosis made on anterior rhinoscopy.
Stepwise approach:
- History → unilateral/bilateral obstruction, trauma, sinusitis, epistaxis, snoring.
- Anterior rhinoscopy (after decongestion) → confirm deviation, spur, turbinate hypertrophy.
- Diagnostic nasal endoscopy (DNE) → best for posterior deviations, spurs and the osteomeatal complex; identifies the bleeding point and assesses concurrent polyps.
- CT scan of nose and PNS (coronal cuts) → investigation of choice when sinusitis or surgery is being planned; shows the bony deviation, OMC obstruction, concha bullosa and sinus disease. Not needed for simple uncomplicated DNS.
- Cold-spatula / anterior rhinomanometry / acoustic rhinometry → objective airflow assessment (academic, occasionally tested).
High-yield: Anterior rhinoscopy after decongestion is the basic diagnostic step; CT PNS (coronal) is the imaging investigation of choice when sinusitis or surgery is contemplated. Diagnostic nasal endoscopy best demonstrates posterior deviations and spurs.
Management
Conservative
- Asymptomatic minor deviation needs no treatment.
- Symptomatic mucosal/turbinate component → topical steroid sprays, decongestants (short-term only), treat allergic rhinitis.
Surgical
Surgery is offered for symptomatic deviation: persistent obstruction, recurrent sinusitis, recurrent epistaxis from a spur, headache from contact points, or as access for endoscopic sinus surgery.
The two classic operations — a must-know comparison:
| Feature | SMR (Submucous Resection) — Killian, 1904 | Septoplasty — Freer/Cottle, conservative |
|---|---|---|
| Principle | Resect deviated bone & cartilage between preserved mucoperichondrial flaps | Reposition / reshape cartilage; minimal resection |
| Tissue removed | Large amount of cartilage + bone | Minimal; cartilage conserved |
| Incision | Killian's incision (~1 cm behind the caudal margin) | Freer's / Cottle's (hemitransfixion) incision at the caudal margin |
| Caudal deviation | Cannot correct well (incision is posterior) | Corrects caudal/anterior deviation well |
| Age | Adults only (avoid in children) | Procedure of choice; more flexible |
| Complications | More — septal perforation, saddle nose, flapping septum, supratip depression | Fewer; preserves support |
| Current status | Largely replaced by septoplasty | Operation of choice today |
Why septoplasty replaced SMR: SMR removes a large block of cartilage, leaving little support → higher rates of septal perforation, saddle-nose deformity, supratip depression and a "flapping"/flail septum. Septoplasty is conservative — the cartilage is mobilised, scored, and repositioned in the midline, preserving an adequate dorsal and caudal L-strut for support.
High-yield: SMR uses the Killian incision (set back from the caudal edge); septoplasty uses the Freer / Cottle hemitransfixion incision at the caudal margin. The caudal-edge incision is why septoplasty — and not SMR — can correct caudal/anterior dislocations.
The L-strut: During septoplasty a minimum of about 1 cm (1.0–1.5 cm) of dorsal and caudal cartilage must be preserved to maintain nasal tip and dorsal support — sacrificing it causes a saddle/supratip deformity.
Minimum age — a favourite fact
Septal surgery should be deferred until ~17 years of age (after puberty / once facial growth is largely complete). Operating earlier risks damaging the septal growth centres and producing midface/nasal growth retardation. In emergencies (e.g. a septal haematoma/abscess) drainage is done at any age, but elective correction waits.
High-yield: Elective septoplasty/SMR is deferred until about 17 years of age because the septum is a midfacial growth centre; early surgery → arrested nasal and midface growth.
Adjuncts
- Turbinate reduction (submucosal diathermy, partial turbinectomy, coblation) for irreversible compensatory hypertrophy.
- FESS if sinusitis coexists.
- Septorhinoplasty when there is associated external (dorsal/caudal) deformity.
Complications
Of the disease itself: recurrent sinusitis, recurrent epistaxis, OSA, otitis media, anosmia, contact headache.
Of surgery (especially SMR):
| Complication | Mechanism / note |
|---|---|
| Septal perforation | Bilateral opposing mucosal tears; commoner after SMR |
| Saddle-nose / supratip depression | Excess dorsal cartilage removed |
| Flapping / flail septum | Both struts removed → no support (SMR) |
| Septal haematoma | Blood between flaps; must be drained — risk of abscess |
| Septal abscess | Infected haematoma → cartilage necrosis → saddle nose |
| Adhesions / synechiae | Between septum and lateral wall |
| Toxic shock syndrome | From retained nasal packing — remove pack timely |
| CSF rhinorrhoea | Injury to cribriform plate during high posterior work (rare) |
| Anosmia | Olfactory mucosa injury |
High-yield: A septal haematoma must be drained immediately — left untreated it becomes a septal abscess, the cartilage undergoes avascular necrosis, and the result is a saddle-nose deformity. Toxic shock syndrome is the dreaded complication of retained nasal packing.
Key differentials of nasal obstruction
Distinguish DNS from other causes of a blocked nose:
- Hypertrophic / allergic rhinitis — bilateral, boggy bluish turbinates, decongests well; obstruction is variable.
- Nasal polyps — pale, mobile, insensitive to probing, often bilateral (ethmoidal) or unilateral (antrochoanal); decongestion does not shrink them.
- Adenoid hypertrophy — children, mouth breathing, adenoid facies, nasal-quality voice.
- Concha bullosa — pneumatised middle turbinate on CT; can mimic/accompany DNS.
- Foreign body / rhinolith — unilateral foul discharge in a child.
- Sinonasal tumour / juvenile nasopharyngeal angiofibroma — unilateral obstruction + epistaxis in an adolescent male; do not biopsy in the clinic.
- Antrochoanal polyp (Killian polyp) — unilateral, single, arises from maxillary antrum.
High-yield: A spur causes a fixed obstruction that does not improve with decongestion, whereas turbinate/allergic swelling shrinks with a vasoconstrictor — the simplest bedside differentiator.
Eponyms & named facts (memory anchors)
- Killian incision → SMR.
- Killian's submucous resection described 1904.
- Freer's incision / Cottle hemitransfixion → septoplasty.
- Cottle's test/manoeuvre → cheek pulled laterally relieves obstruction → suggests nasal valve collapse/area pathology.
- Sluder's neuralgia → spur-induced facial pain.
- Little's area / Kiesselbach's plexus → anterior septal vascular zone (common epistaxis site, relevant when a spur bleeds).
- L-strut → dorsal + caudal cartilage to preserve.
Mnemonic for SMR complications — "SAD FACTS": Septal perforation, Abscess, Depression (supratip/saddle), Flapping septum, Adhesions, CSF leak, Toxic shock (packing), Synechiae.
Recently asked / exam angle
- Incision matching: "Which incision is used in SMR?" → Killian. "Septoplasty incision?" → Freer/Cottle hemitransfixion. Frequently asked as a single-line recall.
- Compensatory hypertrophy side: the inferior turbinate hypertrophies on the concave (opposite, wider) side — a classic two-step reasoning MCQ.
- Minimum age for septal surgery: ~17 years (after facial growth); asked directly.
- Why septoplasty preferred over SMR: conserves cartilage → fewer perforations/saddle nose.
- Investigation of choice with sinusitis: CT PNS coronal.
- Septal haematoma management: immediate incision & drainage to prevent abscess and saddle nose.
- Headache from spur: Sluder's neuralgia / contact-point headache.
- Cause of saddle nose: untreated septal abscess, or over-resection in SMR.
- Image-based: anterior rhinoscopy photo of a spur or coronal CT showing deviation with contralateral turbinate hypertrophy.
Rapid revision
- Septal cartilage = quadrilateral cartilage; bony parts = perpendicular plate of ethmoid + vomer.
- Commonest cause of DNS = trauma; commonest non-traumatic cause = developmental disproportion.
- S-shaped deviation can obstruct both nostrils and is the hardest to correct.
- Compensatory inferior turbinate hypertrophy is on the concave/opposite (wider) side.
- SMR → Killian incision; Septoplasty → Freer/Cottle hemitransfixion incision.
- Septoplasty is the operation of choice today (conservative, fewer complications).
- Preserve a dorsal + caudal L-strut (~1 cm) to avoid saddle/supratip deformity.
- Minimum age ~17 years for elective septal surgery (protect growth centres).
- Investigation of choice with sinusitis/before surgery = CT PNS (coronal).
- Spur → Sluder's neuralgia (contact-point headache) and a common epistaxis site.
- Septal haematoma → drain immediately to prevent abscess → cartilage necrosis → saddle nose.
- Toxic shock syndrome = dreaded complication of retained nasal packing.