Laryngology & Airway
The larynx is easier to reason about once you accept that it does three things in a strict order of importance.
Airway first. Nothing else matters if air cannot pass.
Sphincter second. The larynx closes to protect the lower airway during swallowing, and a larynx that cannot close produces aspiration pneumonia.
Voice third. Phonation is evolutionarily the newest function and clinically the most expendable.
Every laryngeal disease, and every operation performed on the larynx, trades down that list. A tracheostomy sacrifices voice to secure airway. A cord medialisation sacrifices a little airway to restore voice and protect against aspiration.
This single hierarchy also produces the most reliable inversion in the subject, which is that the palsy with the good voice is the dangerous one.
1. The Nerves and What They Do
The vagus supplies the larynx through two branches, and their territories are worth separating precisely because examiners test the exceptions.
The superior laryngeal nerve divides into an internal branch, which is sensory to the larynx above the cords, and an external branch, which supplies only the cricothyroid muscle.
The recurrent laryngeal nerve supplies every other intrinsic muscle of the larynx and provides sensation below the cords.
Two consequences follow.
Internal laryngeal nerve injury abolishes the cough reflex above the cords, so the patient aspirates silently. This is why a normal-sounding patient can still be at risk.
External laryngeal nerve injury weakens the cricothyroid, the muscle that tenses the cord. The voice is not hoarse but loses its upper range and tires quickly, which matters enormously to a singer and is easily missed in anyone else. It is the nerve at risk when the superior thyroid pedicle is ligated.
Why the left recurrent laryngeal nerve is more often injured
The left nerve loops under the aortic arch and travels a far longer course through the mediastinum. The right loops around the subclavian artery in the neck.
That length exposes the left nerve to disease it has no business encountering: bronchogenic carcinoma, mediastinal nodes, an aortic arch aneurysm, a left atrium enlarged by mitral stenosis, and oesophageal carcinoma.
A new hoarseness with a normal larynx on examination but an immobile left cord is a chest problem until the chest has been imaged.
A non-recurrent laryngeal nerve occurs almost exclusively on the right, in association with an aberrant right subclavian artery, and is a surgical trap rather than a clinical one.
2. Vocal Cord Palsy
The clinical picture depends entirely on whether one cord or both are paralysed, and the two present as near-opposites.
| Feature | Unilateral palsy | Bilateral palsy |
|---|---|---|
| Voice | Breathy, weak, poor volume | Often surprisingly normal |
| Airway | Adequate | Stridor, may be critical |
| Aspiration | Common, from incompetent closure | Less prominent |
| Priority | Voice and swallowing | Secure the airway |
Bilateral palsy is the emergency, and it is the one with the better voice. Both cords sit near the midline, so they approximate well enough to phonate but leave a slit of an airway. Patients can speak clearly while heading toward obstruction, which is exactly why the diagnosis is missed.
Unilateral palsy leaves a wide glottic gap, so the voice is breathy and the patient aspirates thin liquids, but the airway is safe.
Management
Unilateral palsy is observed initially, because many recover, particularly after thyroid surgery where transient paralysis is far commoner than permanent. Reported figures after thyroidectomy run around 9 to 10 per cent transient and 2 to 3 per cent permanent.
Speech therapy is first-line. Where the gap persists, injection laryngoplasty with an absorbable material is used within the first year while recovery remains possible, with permanent medialisation or reinnervation procedures reserved for after 12 months.
Bilateral palsy needs the airway secured, often by tracheostomy, and later procedures that widen the glottis do so at the cost of voice, which returns to the hierarchy the chapter opened with.
3. Stridor: Read the Phase
Stridor is a physical sign, not a diagnosis, and the phase of respiration in which it occurs localises the obstruction.
| Phase | Level | Reasoning |
|---|---|---|
| Inspiratory | Supraglottic or glottic | Extrathoracic airway collapses inward on inspiration |
| Biphasic | Subglottic or tracheal | A fixed narrowing obstructs in both directions |
| Expiratory | Intrathoracic, lower airway | Airway narrows on expiration as pleural pressure rises |
This follows from pressure mechanics rather than from memorisation. During inspiration the extrathoracic airway is at negative pressure relative to atmosphere and tends to collapse; during expiration the intrathoracic airway is compressed by rising pleural pressure.
Stridor plus drooling plus a toxic child is epiglottitis until proved otherwise, and the child must not be laid flat or examined with a tongue depressor.
Assessing severity matters more than assessing cause in the first minutes. Rising respiratory rate with worsening recession is bad; a falling respiratory rate with a quietening stridor in an exhausted child is far worse, because it signals impending arrest rather than improvement.
Why the paediatric airway fails faster
Four anatomical differences explain why a child obstructs where an adult would cope.
The paediatric airway is absolutely narrower, and resistance to airflow rises with the fourth power of the radius, so a millimetre of circumferential oedema removes a far greater proportion of a child's lumen than of an adult's.
The narrowest point is the cricoid ring rather than the glottis, so subglottic swelling matters disproportionately. The larynx also sits higher and more anteriorly, and the epiglottis is longer and floppier, which changes intubation technique.
Finally, children have a proportionally higher oxygen consumption and a smaller functional residual capacity, so they desaturate within seconds rather than minutes once ventilation stops.
Together these mean that a child with stridor has less reserve than the calm appearance suggests, and deteriorates abruptly rather than gradually.
4. Voice Disorders
Most hoarseness is benign, but the distinction that matters is between lesions of use and lesions of concern.
| Lesion | Typical patient | Character |
|---|---|---|
| Vocal nodules | Teachers, singers, children who shout | Bilateral, symmetrical, at the junction of anterior and middle thirds |
| Vocal polyp | Often after a single episode of vocal abuse | Unilateral, pedunculated or sessile |
| Reinke oedema | Smokers, characteristically women | Diffuse, bilateral, low gruff voice |
| Contact ulcer or granuloma | Reflux, intubation, throat clearing | Posterior, near the vocal process |
Nodules are bilateral because they form where the cords strike each other hardest, which is a mechanical rather than a pathological explanation and predicts the site reliably.
Reinke oedema is a smoking disease, and it produces a strikingly deep voice; women often present because they are being mistaken for men on the telephone. It improves only if the patient stops smoking.
The rule that overrides all of this remains: hoarseness for more than three weeks in an adult requires visualisation of the cords. Assuming a benign cause without looking is the error that lets glottic carcinoma grow.
When the cords are normal
Muscle tension dysphonia is hoarseness produced by excessive laryngeal and paralaryngeal muscle activity in a structurally normal larynx, often following an upper respiratory infection or a period of vocal strain that has since resolved.
The point worth holding is that a normal-looking larynx does not mean a normal voice, and does not mean nothing is wrong. These patients are frequently told there is no problem, which entrenches the compensatory pattern.
Treatment is voice therapy, and it works well. Puberphonia, the persistence of a high-pitched voice in a post-pubertal male with a normal larynx, is a related functional disorder treated the same way.
5. Recurrent Respiratory Papillomatosis
Laryngeal papillomatosis is caused by HPV types 6 and 11, the low-risk types, acquired at birth in the juvenile form.
It is benign but behaves badly because it recurs relentlessly, obstructs the airway, and can seed distally into trachea and lung. Repeated debulking is the mainstay, and the aim is disease control rather than cure.
Adjuvant treatments are used in aggressive disease, and bevacizumab, given intralesionally or systemically, is the adjuvant with the most current interest, with recent prospective work showing reduced disease burden and improved voice. Cidofovir has been the older comparator.
Two management principles are worth carrying. Tracheostomy is avoided where possible, because it is associated with distal spread of papillomas into the tracheobronchial tree. And HPV vaccination is the only established preventive strategy, which links laryngology to a public health intervention.
Laryngopharyngeal reflux is associated with worse disease and more treatment complications, so it is treated alongside.
6. Reflux and the Larynx
Laryngopharyngeal reflux differs from gastro-oesophageal reflux in presentation, which is why patients deny heartburn.
The complaints are throat clearing, globus sensation, chronic cough, hoarseness worse in the morning, and postnasal drip. Heartburn is often absent, because the refluxate reaches the larynx in small volumes and in the upright position.
The larynx is far more vulnerable than the oesophagus, lacking the same mucosal defences and peristaltic clearance, so much smaller exposures produce symptoms.
Diagnosis is largely clinical, and the evidence for acid suppression is weaker than practice suggests, which is worth stating honestly. Behavioural measures, weight reduction and avoiding late meals carry real weight alongside any drug.
7. Securing the Airway
Tracheostomy
Indications group into three: bypassing upper airway obstruction, permitting prolonged ventilation with easier weaning and sedation, and allowing pulmonary toilet in a patient who cannot clear secretions.
Complications divide by timing, which is the framework examiners use.
| Timing | Complications |
|---|---|
| Immediate | Haemorrhage, pneumothorax, injury to recurrent laryngeal nerve or oesophagus, tube misplacement |
| Intermediate | Tube blockage, displacement, surgical emphysema, infection |
| Late | Tracheal stenosis, tracheo-oesophageal fistula, tracheo-innominate fistula, persistent fistula, scarring |
Tracheo-innominate fistula is rare and catastrophic, presenting with a sentinel bleed before massive haemorrhage, and it is a reason to take any bleeding around a tracheostomy seriously.
Cricothyroidotomy
In a can't intubate, can't oxygenate emergency, the cricothyroid membrane is the target because it is superficial, palpable and avascular relative to the trachea, lying between the thyroid and cricoid cartilages.
It is contraindicated in children, conventionally under about 12 years, because the cricoid is the narrowest part of the paediatric airway and the sole complete cartilaginous ring, so injury produces subglottic stenosis.
Cricothyroidotomy is a temporary measure converted to a formal tracheostomy when circumstances permit.
8. Trauma, Sleep and the Collapsing Airway
Laryngeal trauma
Blunt laryngeal injury, classically from a road traffic collision or a clothesline injury to the extended neck, is uncommon and easily underestimated.
The warning features are hoarseness or aphonia, surgical emphysema, loss of the normal thyroid cartilage contour, haemoptysis and pain on swallowing. Surgical emphysema after neck trauma means the airway has been breached until proved otherwise.
The danger is that the airway looks adequate on arrival and then swells shut. Oedema and haematoma accumulate over hours, so the decision about securing the airway is made early rather than reactively.
Blind or repeated intubation attempts can convert a partial laryngeal disruption into a complete one, so where the larynx is disrupted a tracheostomy under local anaesthesia is the safer route.
Obstructive sleep apnoea
Sleep apnoea is a laryngological problem in the broad sense, because it is caused by loss of pharyngeal dilator muscle tone during sleep in an airway that is already narrow.
The pharynx has no rigid skeleton and is held open actively by muscle. Sleep removes that tone, so any anatomical narrowing, from obesity, tonsillar hypertrophy, retrognathia or a large tongue base, becomes a collapse.
Diagnosis is by polysomnography, and severity is described by the apnoea-hypopnoea index. The consequences are systemic rather than local: daytime somnolence, hypertension, arrhythmia, and a well-documented excess of road traffic collisions.
In children the commonest cause is adenotonsillar hypertrophy, and adenotonsillectomy is usually curative. In adults, weight reduction and continuous positive airway pressure are the mainstays, with surgery reserved for specific anatomical obstruction.
Sleep apnoea also matters at intubation, since these are frequently difficult airways and are unusually sensitive to sedatives and opioids.
9. Worked Examples
Example 1. A 62-year-old smoker develops hoarseness. Flexible laryngoscopy shows a normal-looking larynx with an immobile left vocal cord. What is the next investigation?
Imaging of the chest and the whole course of the left recurrent laryngeal nerve, from skull base to aortic arch, usually by contrast CT.
The left nerve loops under the aortic arch, so its long mediastinal course exposes it to bronchogenic carcinoma, mediastinal nodes, aortic aneurysm, a left atrium enlarged by mitral stenosis and oesophageal carcinoma. A palsy with a normal larynx means the lesion lies along the nerve, not in the larynx, and in a smoker of this age lung cancer heads the list.
Example 2. Two days after total thyroidectomy a patient has stridor at rest but a clear, strong voice. What has happened and what is the priority?
Bilateral recurrent laryngeal nerve palsy. Both cords lie close to the midline, so they approximate well enough for phonation, giving a deceptively normal voice, while leaving only a slit for airflow.
The priority is the airway, not the voice: this patient may need reintubation or tracheostomy. The trap is that a good voice is falsely reassuring, and bilateral palsy is precisely the presentation in which the voice is preserved. Unilateral palsy would give the opposite picture, a breathy weak voice with a safe airway.
Example 3. A 4-year-old has inspiratory stridor, drooling, high fever and sits leaning forward refusing to lie down. A colleague reaches for a tongue depressor. Comment.
Stop. This is acute epiglottitis until proved otherwise, and examining the pharynx with a tongue depressor or laying the child flat can precipitate complete airway obstruction. The child should be kept upright, calm and with a parent, with no cannulation or throat examination attempted. The correct step is immediate involvement of the most senior anaesthetist and ENT surgeon available, with inspection and intubation performed in theatre with facilities for surgical airway. Antibiotics follow airway control, not the other way round.
Example 4. A 35-year-old schoolteacher has six months of hoarseness that worsens through the school day. Laryngoscopy shows symmetrical swellings at the junction of the anterior and middle thirds of both cords. What are they and how does the site help?
Vocal nodules. The site is diagnostic rather than incidental: the junction of the anterior and middle thirds is the point of maximum impact where the cords strike each other during phonation, which is why nodules form there and why they are bilateral and symmetrical.
This is a mechanical injury from voice use, matching her occupation and the diurnal worsening. Treatment is voice therapy and vocal hygiene rather than surgery in the first instance. A unilateral lesion at the same site would suggest a polyp instead, and any asymmetry or irregularity requires closer scrutiny for malignancy.
Example 5. A 5-year-old has a foreign body causing complete airway obstruction and cannot be intubated or oxygenated. Why is cricothyroidotomy the wrong procedure here, and what is the alternative?
Because the cricoid cartilage is the narrowest part of the paediatric airway and the only complete cartilaginous ring in the airway, so incising the cricothyroid membrane in a small child risks damaging it and producing subglottic stenosis. Cricothyroidotomy is conventionally avoided under about 12 years.
The alternative is needle cricothyroidotomy with jet insufflation as a temporising measure to oxygenate, followed by a definitive surgical airway or removal of the foreign body under controlled conditions. In adults the anatomy reverses the reasoning, since the cricothyroid membrane is superficial, palpable and relatively avascular, making it the correct emergency target.
Summary
The larynx does three things in priority order: airway, sphincter, voice. Every intervention trades down that list.
The external laryngeal nerve supplies only cricothyroid; injury costs vocal range, not clarity.
The internal laryngeal nerve is sensory above the cords; injury causes silent aspiration.
The left recurrent laryngeal nerve loops under the aortic arch, so a left cord palsy is a chest problem until imaged.
Bilateral cord palsy gives a good voice and a dangerous airway; unilateral gives a bad voice and a safe airway.
After thyroidectomy, transient palsy is far commoner than permanent.
Injection laryngoplasty with absorbable material is used within the first year; permanent procedures after 12 months.
Inspiratory stridor is supraglottic or glottic, biphasic is subglottic, expiratory is intrathoracic.
A falling respiratory rate with quietening stridor means exhaustion, not improvement.
Never use a tongue depressor or lay flat a child with suspected epiglottitis.
Nodules are bilateral at the anterior-middle third junction because that is where cords strike hardest.
Reinke oedema is a smoker's disease producing a deep gruff voice.
Hoarseness beyond three weeks in an adult requires visualisation of the cords.
Laryngeal papillomatosis is HPV 6 and 11; bevacizumab is the current adjuvant of interest.
Avoid tracheostomy in papillomatosis because it promotes distal spread.
HPV vaccination is the only established preventive strategy for papillomatosis.
Laryngopharyngeal reflux presents without heartburn, and the evidence for acid suppression is weaker than practice suggests.
Tracheostomy complications divide into immediate, intermediate and late; a sentinel bleed suggests tracheo-innominate fistula.
Cricothyroidotomy is contraindicated in young children because the cricoid is the narrowest point and the only complete ring.
