# Deep Neck Space Infections

## Introduction

**Deep neck space infections (DNSIs)** are potentially life-threatening conditions involving the fascial compartments of the neck. Despite the availability of modern antibiotics, these infections remain dangerous due to the risk of airway compromise, vascular complications, and mediastinal extension. Prompt recognition, appropriate imaging, airway management, and surgical drainage when indicated are the cornerstones of treatment.

## Cervical Fascia and Spaces

### Superficial Cervical Fascia
Invests the platysma; infections superficial to this layer are cervical cellulitis or superficial abscesses.

### Deep Cervical Fascia
**Superficial layer (investing fascia)**: encloses the SCM, trapezius, parotid, submandibular glands. **Middle layer (visceral/pretracheal fascia)**: encloses the thyroid, trachea, esophagus, strap muscles. **Deep layer (prevertebral fascia)**: covers the prevertebral muscles and cervical spine. **Alar fascia**: between the middle and deep layers; creates the danger space.

### Key Deep Neck Spaces
**Parapharyngeal space (PPS)**: central; connects to all other spaces; shaped like an inverted pyramid. **Retropharyngeal space**: between the pharynx and prevertebral fascia; extends from skull base to T1-T2. **Danger space**: between the alar and prevertebral fascia; extends from skull base to the diaphragm; conduit for mediastinal spread. **Submandibular space**: contains the submandibular gland; divided by the mylohyoid into sublingual and submylohyoid components. **Peritonsillar space**: between the tonsil capsule and the superior constrictor. **Masticator space**: contains the muscles of mastication and the mandible. **Prevertebral space**: deep to the prevertebral fascia.

![Cross-sectional anatomy of the deep neck spaces showing the superficial, middle, and deep layers of cervical fascia](/images/deep-neck-spaces-anatomy.jpg)

## Etiology and Sources

### Common Sources
**Odontogenic infections**: most common cause in adults (dental caries, periodontal disease, mandibular third molars). **Tonsillar and pharyngeal infections**: peritonsillar abscess, pharyngitis (common in children). **Salivary gland infections**: sialadenitis, suppurative parotitis. **Upper respiratory tract infections**: sinusitis, otitis. **Foreign body ingestion**: pharyngeal or esophageal perforation. **IV drug use**: direct injection into neck veins. **Iatrogenic**: dental procedures, tonsillectomy, neck surgery.

### Microbiology
**Polymicrobial** in most cases. **Streptococcus** species (S. pyogenes, viridans group): most common aerobic organisms. **Staphylococcus aureus** (including MRSA): increasing prevalence. **Anaerobes**: Prevotella, Bacteroides, Fusobacterium, Peptostreptococcus. **Eikenella**: associated with human bites. **Klebsiella pneumoniae**: associated with diabetic patients, particularly in Asian populations.

## Clinical Presentation

### General Symptoms
Fever, malaise, odynophagia, dysphagia, neck pain, trismus. **Neck swelling**: may be unilateral or bilateral. **Toxic appearance**: sepsis, dehydration.

### Space-Specific Presentations

| Space | Classic Presentation | Key Danger |
|-------|---------------------|------------|
| Peritonsillar | Unilateral tonsillar swelling, trismus, uvular deviation, "hot potato" voice | Parapharyngeal extension |
| Submandibular (Ludwig angina) | Bilateral floor-of-mouth swelling, elevated tongue, drooling | Airway obstruction |
| Parapharyngeal | Trismus, medial pharyngeal wall displacement | Carotid sheath involvement |
| Retropharyngeal | Dysphagia, neck stiffness, posterior pharyngeal bulge | Mediastinal extension via danger space |
| Masticator | Trismus, mandibular angle swelling | Intracranial extension |

**Peritonsillar abscess**: unilateral tonsillar swelling, trismus, uvular deviation, muffled ("hot potato") voice. **Submandibular space (Ludwig angina)**: bilateral floor-of-mouth swelling, elevated tongue, drooling, airway compromise. **Parapharyngeal space**: trismus, medial displacement of the pharyngeal wall, deep neck pain. **Retropharyngeal space**: dysphagia, neck stiffness, posterior pharyngeal bulge; **especially dangerous in children** (retropharyngeal lymph nodes suppurate). **Masticator space**: trismus, mandibular angle swelling.

### Life-Threatening Complications
**Airway obstruction**: most common cause of death. **Mediastinitis**: infection spreads via retropharyngeal/danger space to the mediastinum. **Internal jugular vein thrombophlebitis (Lemierre syndrome)**: Fusobacterium necrophorum septic thrombophlebitis with septic emboli. **Carotid artery erosion**: hemorrhage from mycotic pseudoaneurysm. **Necrotizing fasciitis**: rapidly progressive, high mortality.

## Diagnostic Workup

### Laboratory
CBC with differential, CRP, blood cultures, Blood glucose (screen for diabetes), renal function, Lactate if sepsis is suspected.

### Imaging
**CT neck with IV contrast**: gold standard; ring-enhancing fluid collection, loss of fat planes, edema. Evaluate: specific space involvement, airway narrowing, vascular complications (thrombosis, pseudoaneurysm), mediastinal extension. **CT chest**: if mediastinal extension suspected. **Ultrasound**: useful for peritonsillar abscess (intraoral) and superficial collections. **MRI**: reserved for selected cases; superior for differentiating phlegmon from abscess.

![Axial CT with contrast showing a large parapharyngeal space abscess with rim enhancement and mass effect on the airway](/images/parapharyngeal-abscess-ct.jpg)

## Management

### Airway Management
**Secure the airway first** if there is any concern for compromise. Options: awake fiberoptic intubation, tracheotomy. **Ludwig angina** with floor-of-mouth swelling may make intubation impossible — prepare for surgical airway.

### Medical Management
**IV antibiotics**: empiric broad-spectrum coverage. Ampicillin-sulbactam or clindamycin + ceftriaxone (cover aerobes and anaerobes). Add vancomycin if MRSA suspected. Tailor based on culture and sensitivity results. **IV hydration and pain control**. **Corticosteroids**: may reduce edema and improve airway (controversial; do not use if necrotizing fasciitis suspected).

### Surgical Drainage
Indicated for: drainable abscess on imaging, failure to improve on IV antibiotics within 48 hours, airway compromise, suspected necrotizing fasciitis. **Peritonsillar abscess**: needle aspiration or incision and drainage (intraoral); quinsy tonsillectomy if recurrent. **Submandibular/sublingual space**: transoral or transcervical drainage depending on extent. **Parapharyngeal and retropharyngeal abscess**: transcervical approach for large collections; transoral for selected retropharyngeal abscesses. Drains left in place until output diminishes. Repeat imaging if clinical improvement stalls.

## Special Considerations

### Ludwig Angina
Bilateral sublingual and submandibular space infection. Rapidly progressive; can cause airway obstruction within hours. **Airway management is the priority** — prepare for surgical airway. Antibiotics + surgical drainage (transcervical bilateral submandibular and sublingual drainage).

### Lemierre Syndrome
Septic thrombophlebitis of the **internal jugular vein** following pharyngeal infection. Caused by **Fusobacterium necrophorum**. **Septic pulmonary emboli**: chest X-ray shows bilateral cavitary infiltrates. Treatment: prolonged antibiotics (4-6 weeks); anticoagulation is controversial; IJV ligation if septic emboli continue despite treatment.

![CT demonstrating internal jugular vein thrombosis in Lemierre syndrome with perivenous inflammation](/images/lemierre-syndrome-ct.jpg)

## Key Clinical Pearls

**Airway management** is the first priority in any deep neck space infection. Odontogenic sources are the most common etiology in adults; tonsillar/pharyngeal infections in children. **CT with contrast** is the imaging study of choice; ring-enhancing collections typically require drainage. Ludwig angina is a clinical diagnosis — bilateral floor-of-mouth swelling with an elevated tongue is an airway emergency. Any DNSI patient with chest pain, dyspnea, or clinical deterioration should be evaluated for **descending mediastinitis**. **Lemierre syndrome** should be suspected in a young patient with pharyngitis followed by sepsis with pulmonary infiltrates.

## References

1. Vieira F, Allen SM, Stocks RM, Thompson JW. Deep neck infection. *Otolaryngol Clin North Am*. 2008;41(3):459-483.
2. Huang TT, Liu TC, Chen PR, et al. Deep neck infection: analysis of 185 cases. *Head Neck*. 2004;26(10):854-860.
3. Reynolds SC, Chow AW. Severe soft tissue infections of the head and neck: a primer for critical care physicians. *Lung*. 2009;187(5):271-279.
4. Ridder GJ, Technau-Ihling K, Sander A, Boedeker CC. Spectrum and management of deep neck space infections: an 8-year experience of 234 cases. *Otolaryngol Head Neck Surg*. 2005;133(5):709-714.