🦠 Deep Space Neck Infections
Lemierre’s syndrome, Ludwig’s angina, retropharyngeal abscess, parapharyngeal space infections — the anatomical spread pathways and life-threatening complications.
Deep Neck Space Infections — Overview
Deep neck space infections (DNSIs) are potentially life-threatening infections spreading within the fascial compartments of the neck. They follow predictable anatomical pathways determined by the fascial planes — understanding these pathways explains both the clinical presentation and the pattern of complications. The most feared consequence is descending necrotising mediastinitis, with mortality exceeding 40–50%.
The Critical Principle — Fascial Planes Determine Spread
Infections do not spread randomly — they follow the path of least resistance along fascial planes. The deep cervical fascia creates compartments that can both contain and channel infection. The key anatomical pathway connecting the neck to the mediastinum is the Danger Space (between alar and prevertebral fascia) → posterior mediastinum to the diaphragm. The pretracheal space → anterior mediastinum. Understanding which fascial space is involved predicts where the infection will go.
Deep Neck Spaces — Complete Reference Table
| Space | Boundaries | Common Source | Spread / Complication |
|---|---|---|---|
| Peritonsillar | Between tonsillar capsule and superior pharyngeal constrictor | Acute tonsillitis (Group A Strep) | Most common DNSI. Spreads to parapharyngeal space. Quinsy → I&D. |
| Parapharyngeal (lateral pharyngeal) | Inverted cone: base at skull base, apex at hyoid. Medial = pharyngeal constrictors. Lateral = medial pterygoid / parotid. | Quinsy, dental, parotid, tonsil. Divided into prestyloid (anterior) and retrostyloid (posterior) compartments by the styloid process. | Prestyloid: trismus (pterygoid), airway compromise. Retrostyloid: great vessel involvement (ICA, IJV), CN IX–XII palsy. → Lemierre’s (IJV thrombosis). → Retropharyngeal space. |
| Retropharyngeal | Between posterior pharyngeal wall and alar fascia. Midline raphe divides it into two halves. | Suppurative lymphadenitis in children (Level II nodes drain here). Vertebral osteomyelitis. Penetrating trauma. | → Danger Space (breach alar fascia) → posterior mediastinum → descending necrotising mediastinitis (DNM). Airway compromise from posterior pharyngeal wall bulging. |
| Danger Space (Space 4) | Between alar fascia (anterior) and prevertebral fascia (posterior). Skull base to diaphragm — no anatomical barriers. | Extension from retropharyngeal space | → Posterior mediastinum to diaphragm. Gateway to DNM. Most feared pathway. |
| Pretracheal | Between pretracheal fascia and trachea/thyroid. Continuous with fibrous pericardium inferiorly. | Tracheal perforation, thyroid surgery, oesophageal perforation, dental infection spreading anteriorly | → Anterior mediastinum → pericarditis, cardiac tamponade. Continuous with fibrous pericardium. |
| Prevertebral | Behind prevertebral fascia and vertebral column | Vertebral osteomyelitis / discitis (TB — Pott’s spine most common). IV drug users. | Tracking along vertebral column. Cold abscess (TB) → psoas abscess, paraplegia if cord compression. |
| Submandibular/Sublingual | Submandibular space (below mylohyoid) + sublingual space (above mylohyoid). Communicate posteriorly around mylohyoid. | Lower molar dental infection (particularly 2nd/3rd molars — roots below mylohyoid attachment) | → Ludwig’s angina (bilateral cellulitis — airway emergency). → Parapharyngeal space posteriorly. |
| Masticator | Contains masseter, medial pterygoid, lower ramus/posterior body mandible | Lower 3rd molar infection, mandibular fracture, parotid abscess | Trismus (masseter/pterygoid spasm). Can spread to parapharyngeal space. |