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Second branchial cleft cyst

Dr Yuranga Weerakkody and Dr Frank Gaillard et al.

A second branchial cleft cyst is a cystic dilatation of remnant of the 2^ndbranchial apparatus, and along with 2^nd branchial fistulae and sinuses accounts for 95% of all branchial cleft anomalies.

Demographics and clinical presentation

Although a congenital abnormality, they tend to present in early adulthood (10-40 years of age) often after minor trauma on infection. Second branchial cleft sinus or fistulas on the other hand present earlier.

Typically second branchial cleft cysts present as a rounded swelling just below angle of mandible, anterior to sternocleidomastoid (although the position is variable - see classification below).

Pathology

The cyst is typically filled with mucoid material, is well circumscribed and other than presenting as a swelling, is asymptomatic. If infected however, then surrounding stranding and skin changes are evident.

Location

Cysts can occur anywhere along the course of the second branchial apparatus, from the pharyngeal wall to the skin, as it passes laterally and inferiorly between the ICA and ECA. The angle of the mandible is a frequent location.

Classification

Bailey classification (1929)

Radiographic features

CT

rounded, sharply circumscribed
fluid density centrally
thin wall
extension of the cyst wall between the ICA and ECA just above the carotid bifurcation (sometimes referred to as the notch sign) is said to be 'pathognomonic'.

Ultrasound

sharply demarcated
posterior acoustic enhancement - 70% ³
imperceptible walls - 82%
echogenicity is variable ³
- anechoic - 41%
- homogeneously hypoechoic with internal debris - 24%
- pseudosolid - 12%
- heterogeneous - 23%

MRI

T1 - variable signal dependant on protein content
- high protein content : high signal
- low protein content : low signal
T2 - usually high signal
T1 C+ (Gd) - no enhancement in uncomplicated lesions