Pathologies of the Larynx & Trachea – Comprehensive Study Notes

FUNCTIONS & GENERAL POSITION OF THE LARYNX

Four core roles
- Protection of lower airway during deglutition (laryngeal closure + epiglottic descent)
- Respiration (maintaining airway patency)
- Phonation (primary sound generator)
- Fixation of the chest (Valsalva, heavy lifting, parturition)
Adult topography: lies between $C3 – C6$
Infant topography: slightly higher at $C2 – C3$ then descends with growth

SKELETAL FRAMEWORK OF THE LARYNX

9 cartilages total → 3 single, 3 paired
- Unpaired: Thyroid, Epiglottis, Cricoid
- Paired: Arytenoid, Corniculate, Cuneiform

Thyroid cartilage

Largest, shield-shaped; two laminae fuse at mid-line → laryngeal prominence (Adam’s apple)
Hyaline; tends to calcify/ossify with age

Cricoid cartilage

Signet-ring shaped; ONLY complete cartilaginous ring of airway
Articulates posteriosuperiorly with arytenoids

Epiglottis

Slightly curved, leaf-shaped; anterior wall of larynx
Protects airway during swallowing

Arytenoid, corniculate, cuneiform

Form posterior part of glottic mechanism; give attachment to intrinsic muscles & ligaments

LIGAMENTS OF THE LARYNX

Attached to thyroid cartilage
- Thyroepiglottic ligament: root of epiglottis → thyroid angle
- Vestibular ligament (false cord): below epiglottic attachment
- Vocal ligament (true cord): thickened upper edge of cricothyroid membrane; core of vocal fold

MEMBRANES

Extrinsic (anchor larynx to neighbours)
- Thyrohyoid membrane (+ median & lateral ligaments)
- Cricothyroid membrane (median ligament)
- Cricotracheal ligament
Intrinsic (regulate intra-laryngeal motion)
- Conus elasticus (lateral cricothyroid membrane)
- Quadrangular membrane (arytenoid → epiglottis)
- Aryepiglottic folds (superior border of quadrangular membrane)

MUSCLES

Extrinsic (suspend & move larynx en bloc)
- Suprahyoids: digastric, stylohyoid, mylohyoid, geniohyoid
- Infrahyoids: sternohyoid, sternothyroid, thyrohyoid, omohyoid
Intrinsic (fine phonatory control) – 3 functional groups
1. Open/close glottis
- Posterior cricoarytenoid (sole abductor)
- Lateral cricoarytenoid, transverse & oblique arytenoids (adductors)
1. Tension controllers
- Cricothyroid (tensor)
- Thyroarytenoid & vocalis (relaxers)
1. Inlet shapers
- Aryepiglottic & thyroepiglottic

SUBSITES OF THE LARYNX

Supraglottis: epiglottis → vestibular folds
Glottis: true vocal cords, anterior & posterior commissures
Subglottis: $5\,\text{mm}$ below glottis to first tracheal ring

VASCULAR & NERVE SUPPLY

Arterial: superior & inferior laryngeal branches (from superior/inferior thyroid aa.) + cricothyroid branch
Venous: superior & inferior thyroid vv. → IJV / brachiocephalic vv.
Innervation (branches of Vagus)
- Internal laryngeal n.: sensory above cords
- External laryngeal n.: motor to cricothyroid
- Recurrent laryngeal n.: motor to all other intrinsic muscles; sensory below cords
- Ansa of Galen: communicating loop between internal & recurrent branches

DISTINCTIVE FEATURES OF THE CHILD’S LARYNX

Higher position, touches soft palate during swallowing → obligate nasal breathing
Cartilages soft; epiglottis omega-shaped
Thyroid cartilage flat; laryngeal lumen small & conical
Narrowest point = cricoid ring (smaller than glottis)
Loose submucosa easily oedematous → rapid obstruction

TRACHEA

Begins below cricoid at $C6$ ; ends at carina $T5$ ( $T6$ on deep inspiration)
Length: $10\,\text{cm}$ (neck $5\,\text{cm}$ , thorax $5\,\text{cm}$ ); up to $15\,\text{cm}$ on inspiration
Diameter ≈ $2\,\text{cm}$
15–20 C-shaped hyaline cartilages; posterior wall membranous
Blood: inferior thyroid & bronchial arteries; venous drainage via inferior thyroid v.
Nerves: mucosa afferents via vagus & RLN; sympathetic trunk to smooth muscle & vessels

KEY LARYNGEAL SYMPTOMS/SIGNS

Hoarseness, Stridor, Dyspnea, Cough, Hemoptysis, Dysphagia

HOARSENESS (DYSPHONIA)

Any alteration in voice quality due to laryngeal pathology
Requirements for normal voice
1. Adequate cord approximation
2. Proper size & stiffness
3. Regular vibratory capacity

Pathophysiological mechanisms

Loss of approximation (masses, fixed CA joint)
Altered bulk (paralysis, oedema)
Altered stiffness (↓ with paralysis, ↑ with fibrosis)

Temporal classification

Acute (<2 wk): usually viral laryngitis, chemicals, brief overuse; rarely malignancy
- Rx: voice rest, hydration/humidification, ± antibiotics
Chronic (≥2 wk): reflux, nodules, polyps, papillomatosis, malignancy, neuro disorders, smoking/abuse
- Progressive > months = suspect cancer
- Rx: treat cause, stop smoking, voice therapy, ± surgery/RT

Differential diagnosis

Common: acute viral laryngitis, nodules/polyps/cysts, VC paralysis, hypothyroidism, rhinosinusitis, laryngeal CA, post-intubation, LPR, allergies
Systemic: hypothyroidism, MS, RA, Parkinson’s, SLE, ALS, Wegener’s, MG, sarcoid, tremor, amyloidosis

VOCAL CORD NODULES

“Singer’s/screamer’s” nodes; bilateral, at anterior one-third of VC edge
Epidemiology: women > men; occupations with voice abuse (singers, teachers, traders)
Pathology: abuse → submucosal oedema/haemorrhage → hyalinisation & fibrosis → epithelial hyperplasia
Clinical: hoarseness, otalgia, globus; often symmetrical on laryngoscopy
Management: voice rest, speech therapy; microlaryngoscopic excision if persistent

STRIDOR

Turbulent, harsh sound from partial airway obstruction
Phase indicates level
- Inspiratory → supraglottic/glottic
- Expiratory → intrathoracic trachea/bronchi
- Biphasic → glottis, subglottis, cervical trachea

Etiology

Congenital: choanal atresia, macroglossia, micrognathia (Pierre-Robin), laryngeal web, laryngomalacia, subglottic stenosis, VC paralysis
Acquired: epiglottitis, laryngitis, acute LTB (croup), foreign body, papillomatosis, retropharyngeal abscess, tumours

Evaluation

History: onset, duration, relation to feeding, position changes
Exam: retractions, phase, fever, positional relief (e.g. prone in laryngomalacia)
Flexible laryngoscopy
Imaging (x-ray, CT), MLS/bronchoscopy as required

Management (cause-directed)

Medical, removal of FBs, adenotonsillectomy, microlaryngoscopic excision (papilloma), tracheostomy for severe stenosis, I&D for abscess

RECURRENT RESPIRATORY PAPILLOMATOSIS (RRP)

HPV-induced benign neoplasm; HPV-6 & 11 (11 → more severe)
Two forms: Juvenile (3–5 yr, aggressive) & Adult (less common)
Risk triad: firstborn, vaginal delivery, maternal age < 20 yr
Symptoms: hoarseness, stridor, dyspnea, wheeze, choking, cough, FB sensation
Dx: flexible scope → warty lesions; confirmation by DL + biopsy; lateral neck x-ray screening
Treatment goals: airway, voice, remission
- Repeated microlaryngoscopic CO₂-laser or debrider debulking (avoid vocal ligament injury)
- Adjuvants: intralesional cidofovir, indole-3-carbinol, quadrivalent HPV vaccine (6/11/16/18)
Malignant change rare; recurrences common

LARYNGITIS

Acute

Viral URTI most common; may be bacterial secondary
Non-infectious triggers: alcohol, tobacco, voice trauma, inhaled irritants
S/S: low raspy voice, hoarseness, throat discomfort, dysphagia, dry cough, malaise/fever; cords symmetrically red with sticky secretions ± submucosal haemorrhage
Course: resolves in days; hoarseness may linger 2 wk
Rx: voice & bed rest, steam, lozenges, warm compresses, cough mixture, analgesics, ± antibiotics

Chronic (mentioned under hoarseness)

ACUTE EPIGLOTTITIS (BACTERIAL SUPRAGLOTTITIS)

Rapidly progressive supraglottic inflammation in children $2 – 7$ yr; now less common post-HiB vaccine
Pathogens: $H.\,influenzae\,type\,B$ , Streptococcus spp.
S/S (within < 12 h): high fever, toxic, sore throat, drooling, muffled "hot-potato" voice (NOT hoarse), inspiratory stridor, tachycardia, tripod/sniffing posture
4 Ds mnemonic: Dyspnea, Drooling, Dysphagia, Dysphonia
Avoid oral exam until airway secured
Investigations: lateral neck x-ray → "thumb sign"; cultures after stabilization
Management: hospital admit, airway preparedness (ET tube/tracheostomy tray), humidified O₂, IV broad-spectrum cephalosporin (e.g. ceftriaxone), IV steroids, fluids, analgesics/antipyretics

CROUP (ACUTE LARYNGOTRACHEOBRONCHITIS, LTB)

Commonest upper airway obstruction 6 mo – 6 yr (peak 1–3 yr); viral (parainfluenza I > II, influenza)
Prodrome URTI then
- Barking "seal" cough
- Hoarseness
- Inspiratory stridor, dyspnea, circumoral pallor/cyanosis
- Fever but non-toxic
Signs: subglottic oedema, tenacious crusts; possible atelectasis
X-ray AP neck → "steeple sign" (subglottic narrowing)
Rx: admit, reassurance, humidified air, systemic steroids (dexamethasone), O₂, fluids, antibiotics if bacterial superinfection, ± intubation/tracheostomy, secretion clearance

Epiglottitis vs Croup (key contrasts)

Epiglottitis: toxic, abrupt, high fever > $38.5^{\circ}\text{C}$ , minimal cough, severe dysphagia & drooling, unable to speak
Croup: well-looking, slower viral prodrome, moderate fever, barking cough, can swallow, hoarse voice

FOREIGN BODY ASPIRATION (FBA)

Major cause of accidental death in < 1 yr; 3000 deaths/yr (US)
KATH study: majority 1–3 yr; male:female $2:1$

Risk factors

Children: lack molars, immature swallow, explore orally, active while eating, poor discrimination
Adults: intoxication, sleep, neurological deficits

Common FBs (region specific)

Peanuts, maize, seeds; metallic objects (coins, pins, nails, whistles), bones

Clinical phases

Initial: choking, gagging, paroxysmal cough, obstruction
Asymptomatic: object lodges, reflex fatigue
Complications: haemoptysis, pneumonia, atelectasis, abscess

Symptoms/signs

Sudden cough during play/eating, stridor, dyspnea, voice change, choking, dysphagia, local pain
Classic triad (40 %): wheeze, cough, dyspnea; 40 % may be asymptomatic

Investigations

AP & lateral neck x-ray, CXR ± CT; many FBs radiolucent → look for air-trapping, shift, atelectasis
Diagnostic rigid bronchoscopy = gold standard

Management

Heimlich manoeuvre (per age technique) for acute obstruction
Removal via direct laryngoscopy or rigid bronchoscopy
Tracheostomy if large laryngeal FB
Post-op antibiotics & steroids

UPPER AIRWAY OBSTRUCTION (UAO)

Blockage from nose → carina; narrowest point: subglottis (child), glottis (adult)

Etiological spectrum

Nasal: tumours, choanal atresia, FB, trauma, sinusitis, rhinitis medicamentosa
Nasopharynx: adenoid hypertrophy/itis, tumours, encephalocele
Pharynx: deep neck space infection, FB, tumour, angio-edema
Larynx/trachea: epiglottitis, LTB, trauma, FB, tumours, laryngo-/tracheomalacia, GERD, subglottic stenosis, compression, VC paralysis

Clinical features

Hallmark: stridor
Others: dyspnea, dysphagia, cough, hoarseness, choking, pain, drooling, SQ emphysema, bleeding, fever

Diagnostics

Imaging: neck/chest x-ray (thumb/steeple signs, deviation, FB), CT/MRI (tumour, vascular anomaly)
Endoscopy: definitive diagnosis, biopsy & staging
Blood gases for severity

Treatment

Medical (ICU)

Oxygen, humidification, corticosteroids, antibiotics, cautious intubation (contra in laryngeal #, cervical spine injury)

Surgical

Cricothyrotomy: emergent airway via cricothyroid membrane; palliative in terminal cases or anatomic variants
Tracheostomy: definitive stoma in anterior tracheal wall
- Indications: bypass UAO, bronchial toileting, assisted ventilation, prolonged intubation

TRACHEOSTOMY DETAILS

Functions: alternate airway, improve ventilation, protect lower tract, facilitate secretion removal, permit anaesthesia/IPPV
Disadvantages: anosmia, aphonia, inability to swim/lift, aspiration risk without cuff
Types
1. Timing: emergency vs elective
2. Purpose: temporary vs permanent
3. Position: high / mid / low (Jackson’s safety triangle guides mid)
Jackson’s Safety Triangle boundaries
- Base: inferior border of thyroid cartilage
- Apex: suprasternal notch
- Sides: medial borders of SCM muscles

Complications

Immediate (0–6 h): haemorrhage, air embolism, apnoea, cardiac arrest, local injury, false passage, posterior wall puncture, loss of airway
Early (6–72 h): tube dislodgement, surgical emphysema, pneumothorax/mediastinum, crusts, infection, necrosis, tracheo-arterial fistula, dysphagia, BP-related bleed
Late (>72 h): scarring, stenosis, difficult decannulation, tracheo-innominate fistula, tracheo-oesophageal/cutaneous fistula

ETHICAL & PRACTICAL NOTES

Early recognition of paediatric airway disease prevents fatal obstruction
Vaccination (HiB, HPV) lowers incidence of epiglottitis and papillomatosis
Voice conservation strategies & occupational health crucial for professionals
Tracheostomy care demands multidisciplinary follow-up to mitigate morbidity

NUMERICAL & STATISTICAL HIGHLIGHTS

Larynx levels: $C3 – C6$ (adult), $C2 – C3$ (infant)
Subglottis length: $5\,\text{mm}$ to first tracheal ring
Tracheal length: $10\,\text{cm}$ (rest), $15\,\text{cm}$ (full inspiration); diameter $2\,\text{cm}$
Cartilage rings: $15 – 20$ in trachea
Croup peak age: $1 – 3$ yr; Epiglottitis: $2 – 7$ yr
FBA mortality pre-20th C = $100\%$ ; contemporary paediatric deaths ≈ $3000$ /yr (US)
Male:female in KATH FBA study $2:1$