Sinus

Background

A sinus (tract) is a narrow channel in the body that is open to an epithelial surface at one end (e.g. skin) and closed at the other end, often draining a cavity such as an abscess (e.g. pilonidal sinus disease). The sinus may only be visible at the skin surface as a small hole or pit.

In children, a preauricular sinus is a common congenital abnormality – present from birth. These are usually seen as a small pit in the skin anterior to the external ear – typically near the ascending limb of the helix or the tragus. They are frequently found on the patient’s right hand side, but may be bilateral, and can be inherited or develop sporadically in an embryo. Rarely, a preauricular sinus can be a sign of an underlying genetic condition.

Signs & symptoms

  • Pit/hole at skin surface
  • Asymptomatic unless infected, in which case the area may become painful and erythematous with purulent discharge
  • If associated with infection/abscess, a mass may be tender and palpable below the skin surface

Differentials

  • Fistula (e.g. orocutaneous fistula)
  • Trauma
  • Genetic condition (e.g. branchio-oro-renal ‘BOR’ syndrome)

Diagnosis

It is important to first obtain a thorough history and examination, after which the following investigations may be required:

  • Exploring the sinus with a probe
  • Imaging (e.g. x-rays, CT scans or MRI scans)
  • Swab with microscopy and culture
  • Biopsy

If a patient has a preauricular sinus and associated hearing loss, then BOR syndrome may be suspected and specialty referral for specific investigations will be required (e.g. audiometry testing, imaging of the temporal bone and renal ultrasound).

Management

The management of a sinus will depend upon the cause. A non-infected preauricular sinus may not require any management. If a sinus tract is infected, systemic antibiotics may be required and/or surgical intervention.

References

https://dermnetnz.org/topics/fistulas-and-sinuses-of-the-neck-and-face/#:~:text=A%20sinus%20may%20drain%20mucus,sinus%20draining%20into%20the%20pharynx.

https://rarediseases.info.nih.gov/diseases/10507/preauricular-sinus#:~:text=Preauricular%20sinus%20is%20a%20common,(bilateral)%20of%20the%20ear.

N.Scheinfeld et al., (2004). The preauricular sinus: a review of its clinical presentation, treatment and associations. Paediatric Dermatology. 21(3). Available at: https://pubmed.ncbi.nlm.nih.gov/15165194/