• Also known as 2nd branchial cleft remnant or branchial cleft anomaly (Coste 2023)
• Congenital developmental defect in 2nd branchial apparatus which may occur as a sinus, fistula, cyst, or any combination of the three (Mehmi 2019, Coste 2023)
• The most common branchial cleft anomaly (makes up 40-95% of all branchial cleft anomalies) (Mehmi 2019, Coste 2023)
• Characteristic location is anteromedial to the sternocleidomastoid (Coste 2023)
• Can occur anywhere between the tonsillar fossa to the supraclavicular region (the tract of the branchial cleft) (Coste 2023)
• May be in proximity to nerves (glossopharyngeal or hypoglossal) and carotid vessels (Coste 2023)
• Bilateral second branchial cleft cysts may be associated with branchio-oto-renal syndrome (Coste 2023)
• Upper respiratory tract infections can result in "increase in size of swelling, purulent discharge and abscess formation" (Mehmi 2019)
• On CT:
  • Low density, unilocular on non-contrast, may be septated if infected
  • Low density with non-enhancing wall on contrast CT, infection can appear as multilocular structure with fat-standing and wall-enhancement
• On MR:
  • T1 shows fluid signal isointense to CSF, infected cysts may have hyperintense proteinaceous contents
  • T2 is hyperintense
  • T1 post-contrast shows no enhancement, unless infection is present in which case the cyst may show ring-enhancement

References

Coste AH, Lofgren DH, Shermetaro C. Branchial Cleft Cyst. [Updated 2023 Jun 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499914/

Mehmi N, Kumar R, Sagar P, Singh CA, Kumar R, Thakar A, Sharma SC. Importance and Impact of Appropriate Radiology in the Management of Branchial Cleft Anomalies. Indian J Otolaryngol Head Neck Surg. 2019 Oct;71(Suppl 1):953-959. doi: 10.1007/s12070-019-01634-w. Epub 2019 Mar 23. PMID: 31742101; PMCID: PMC6848690.