Laryngocele

General features:
Usually in middle-aged men
Bilateral in 25%
Infection in 10% = laryngopyocele
Associated with laryngeal carcinoma, in 15% coexist with laryngeal carcinoma

Embryology:
Laryngeal ventricle is slitlike cavity located between false and true vocal cords
Laryngeal saccule lies along anterior third of roof of ventricle and extends superiorly between false vocal cord, and between aryepiglottic fold and thyroid cartilage
Large in newborns and children and involutes by 6th year
Laryngoceles are dilated laryngeal saccule

Types:
Internal - 40%, confined to larynx, do not pierce thyrohyoid membrane.
External - 25%, extend through thyrohyoid membrane at the level of insertion of the superior laryngeal neurovascular bundle, and dilatation superficial to thyrohyoid membrane only
Mixed - 45%, abnormal dilatation on both sides of thyrohyoid membrane

Etiology:
Due to increase in supraglottic pressure with a long saccule
Pure congenital ones are rare

Clinical features:
Hoarseness, dysphagia, stridor
Increases with Valsalva
Bryce sign = gurgling or hissing sound on compression of mass

Imaging:
Internal are limited by thyrohyoid membrane. External and mixed lie superficial to thyrohyoid membrane

Plain radiograph:
Well defined, round or oval radiolucent area within paralaryngeal soft tissues
50% of laryngoceles detected on plain film have carcinoma

CT:
Well-defined, smooth mass in lateral aspect of superior paralaryngeal space
May be filled entirely with air or contain air-fluid levels
If obstructed, may contain mucoid secretions
Presence of soft-tissue attenuation suggests laryngeal neoplasm
Connection between the air sac and the airway helps to establish diagnosis

References:
1. Koeller KK et al. Congenital Cystic Masses of the Neck: Radiologic-Pathologic Correlation. Radiographics. 1999;19:121-146