Cerumen

Cerumen, also known as earwax, is a natural secretion produced by and found within the external auditory canal (EAC). It has important roles as part of the first line of defense of the ear from micro-organisms and optimizing function of the tympanic membrane and EAC.

Secretion

Cerumen is secreted by the ceruminous glands, in concert with the sebaceous glands. The ceruminous glands are a specialized subtype of apocrine (sweat) glands, with approximately 1,000 to 2,000 within the lining of each external ear canal.

Two main forms of cerumen have been identified :

  • a watery brownish-yellow wax, primarily found in Caucasian and African populations
  • a drier white form, primarily found in Eastern Asian and native American populations

Function

Cerumen has a variety of functions including:

  • lubrication and waterproofing of the external ear canal, maintaining optimal tympanic membrane suppleness
  • trapping foreign material e.g. fungal spores, bacteria, dust
  • antibacterial properties

Radiographic features

Cerumen may mimic a pathological lesion in the external ear canal on CT. It generally has fatty attenuation with a rim of air (see Case 1) . If there is any doubt then direct visual inspection will usually clarify its nature.