Bacterial Infection of the Thyroglossal Duct
Bacteria infect the thyroglossal duct through direct communication between the cyst and the oral cavity, allowing contamination by oral flora. 1
Primary Mechanism of Infection
The thyroglossal duct cyst maintains a communication pathway with the mouth, creating a direct route for oral bacteria to contaminate and infect the cyst. 1 This anatomical connection is the fundamental reason why infection and abscess formation are frequent complications of thyroglossal duct cysts. 1
Source of Infecting Organisms
The bacteria originate from normal oral flora, which includes:
- Viridans group streptococci (α-hemolytic streptococci) 2
- Staphylococcus species 2
- Anaerobic bacteria including Prevotella species and Fusobacterium 2
- Other oral commensals that colonize the oropharynx 2
The oral cavity harbors hundreds of bacterial strains representing both aerobic and anaerobic species. 2 In the gingival crevice—the most likely source of bacteremia—dense colonies of bacteria have ready access to the circulation, particularly when gingival inflammation or manipulation occurs. 2
Routes of Bacterial Entry
Bacteria reach the thyroglossal duct through:
- Direct extension from the oral cavity via the persistent duct communication 1
- Transient bacteremia from routine oral activities (toothbrushing occurs 39-46% of the time, potentially hundreds of times annually) 2
- Dental procedures that create bacteremia (incidence ranges 0-97% depending on the procedure) 2
Clinical Presentation of Infection
Infected thyroglossal duct cysts are the most common presentation in adults, appearing as a painful midline neck mass. 1, 3 The infection rate is substantial:
- 40.8% of patients have a history of infection prior to definitive surgery 4
- 41-43% present with an infected neck mass as their initial symptom 3, 5
- School-aged children more commonly present with infection compared to toddlers (43% vs 22%) 5
When infected, the cyst fills with purulent material and causes pain, particularly with swallowing. 1
Critical Clinical Pitfall
Preoperative infection significantly increases recurrence risk after surgical excision. Patients with preoperative infection have a 20% recurrence rate compared to only 4% in those without prior infection (P = 0.002). 4 This underscores the importance of preventing infection through early definitive surgical management when feasible.
However, incision and drainage of an infected cyst—when necessary—does not appear to increase recurrence risk beyond that associated with infection itself. 4 Only 1 of 6 patients who underwent incision and drainage experienced recurrence. 4
Prevention Strategy
The definitive treatment is the Sistrunk procedure, which removes the cyst, the central portion of the hyoid bone, and the tract extending to the base of the tongue. 1, 4, 3 This eliminates the communication pathway that allows bacterial contamination and prevents the 10.8% overall recurrence rate. 4