Parapharyngeal Abscess

Overview

Definition

Parapharyngeal abscess is a deep neck infection involving the parapharyngeal space.

Epidemiology

• Incidence: 2.6 in 100,000 in Taiwan (unknown in the United States)
• Men > women
• More common in children
• Anterior compartment infection > posterior compartment

Risk factors

• Dental infections
• Tonsillar infections
• Mastoiditis
• Parotitis
• Traumatic injury of oral cavity and pharynx
• Immunosuppression
• Diabetes mellitus
• Hypertension

Etiology

• Most commonly arise from a septic focus of:
  • Lower teeth 
  • Tonsils
  • Parotid gland
  • Deep cervical lymph nodes
  • Middle ear
  • Sinuses
• Parapharyngeal infection is polymicrobial:
  • Common aerobic organisms include:
    • Streptococcus pyogenes
    • Staphylococcus aureus
    • Haemophilus influenzae
    • Viridans streptococci
  • Common anaerobic organisms are:
    • Fusobacterium
    • Prevotella
    • Peptostreptococcus
    • Bacteroides spp.

Pathophysiology

The layers of the deep cervical fascia represent the potential routes of spread of infections.

• Parapharyngeal space:
  • Extends from the base of the skull superiorly to the hyoid bone inferiorly
  • Contiguous with multiple other spaces that can be the source of infection
  • Posterior compartment contains important neurovascular structures:
    • Cranial nerves IX–XII
    • Cervical sympathetic trunk
    • Cervical sheath
  • Infection in the posterior compartment will result in neurologic symptoms.
• Deep-space infections can spread via multiple pathways:
  • Direct extension along fascial planes
  • Lymphatic extension from the oropharynx
  • Penetrating trauma
  • Vascular extension
  • Suppurative lymphadenitis with potential abscess formation

Clinical Presentation and Diagnosis

History

• Patients often present with:
  • Dysphagia
  • Odynophagia
  • Neck pain
  • Trismus: inflammation of pterygoid muscles
  • Torticollis: inflammation of paraspinal muscles
  • Neck swelling
  • Fluctuant mass (not always palpable)
  • Cervical lymphadenopathy 
  • Hoarseness or vocal cord paralysis: involvement of vagus nerve
  • Fever 
• Signs of possible airway obstruction include:
  • Stridor
  • Drooling
• Focus on history details that increase risks:
  • Dental disease
  • Tonsillar disease
  • Immunosuppression
  • Diabetes mellitus
• Neurologic symptoms

Physical exam

• Palpation of the neck to assess for:
  • Asymmetry
  • Fluctuance
  • Fullness
• Otoscopy
• Oral cavity examination: medial displacement of the tonsil and lateral pharyngeal wall
• Palpation of the facial and neck lymph nodes
• May have Horner syndrome, caused by damage to sympathetic nerves on the ipsilateral side of the neck and presenting with:
  • Ptosis
  • Miosis
  • Anhidrosis

Diagnostic testing

• Laboratory studies:
  • CBC/DIFF often shows leukocytosis.
  • Chemistry panel
  • Blood cultures if the patient is septic.
• Culture and Gram stain of aspirated abscess fluid
• Imaging:
  • CT scan:
    • Study of choice
    • A fluid collection with or without peripheral rim enhancement is visible.
  • MRI is used to identify vascular complications.

Management and Complications

The initial management focuses on airway stabilization. Infections are polymicrobial and comprise the usual flora from the adjacent source mucosa. Empiric IV antibiotic therapy should be initiated immediately.

Management

• If infection from a dental source → early removal of source indicated
• Medical therapy: immunocompetent patient regimens
  • Initial medications for presumed oral or dental source:
    • Ampicillin–sulbactam
    • Clindamycin plus levofloxacin
    • Ceftriaxone plus metronidazole
  • For presumed otogenic (ear or mastoid) source:
    • Cefepime plus metronidazole
    • Piperacillin–tazobactam
    • Imipenem or meropenem
  • For presumed sinus source:
    • Vancomycin plus ampicillin–sulbactam
    • Vancomycin plus ceftriaxone plus metronidazole
    • Clindamycin plus levofloxacin
  • MRSA coverage should be initiated in immunocompromised patients or those with a health care facility–associated infection:
    • Vancomycin or linezolid
    • Plus either cefepime and metronidazole, piperacillin–tazobactam, or imipenem
  • Antibiotic regimen can be narrowed when culture results are available.
• Indications for surgical drainage:
  • No improvement of symptoms with antibiotic therapy within 48 hours
  • Abscess loculation

Complications

• Lemierre’s syndrome: septic thrombophlebitis of the internal jugular vein
• Acute mediastinitis
• Aspiration pneumonia
• Damage of carotid sheath contents

Differential Diagnosis

• Meningitis: inflammation of protective membranes of the brain and meninges. Patients present with the classic triad of fever, neck stiffness, and altered mental status. Diagnosis of meningitis is made with a neurologic exam and CSF analysis. Management includes timely administration of broad-spectrum antibiotics. Delay in treatment can result in increased mortality.
• Pharyngitis: inflammation of the pharynx often caused by viral upper respiratory tract infection. Symptoms include sore throat, fever, cough, rhinorrhea, difficulty swallowing. Cough and coryza are absent in group A beta-hemolytic streptococcal pharyngitis. Diagnosis is made on the basis of clinical findings and throat swab results. Management of viral pharyngitis is supportive. Bacterial pharyngitis requires antibiotic therapy.
• Bacterial tracheitis: inflammation of the subglottic trachea. Bacterial tracheitis is a potentially life-threatening infection and is often preceded by a viral upper respiratory tract infection. Patients present with fever, stridor, productive cough, and drooling. Diagnosis is clinical. Management includes airway assessment and broad-spectrum antibiotics.