MRI findings of preauricular sinus: a case report

The preauricular sinus (PS) is a benign congenital abnormality affecting the soft tissues in the preauricular region. Diagnosis is typically clinical and routine imaging is usually unnecessary in symptomatic cases, but individuals with recurrent sinuses or previous unsuccessful surgeries may benefit from pre-operative imaging. Furthermore, PS may be detected incidentally during head and neck magnetic resonance imaging (MRI), emphasizing the need for radiologists and ear, nose, and throat specialists to be familiar with its characteristics. Notably, there is a gap in the existing literature regarding the MRI description of PS.

We present the case of a 19 year-old man complaining of pain in the right external auditory canal. During the physical examination, a small depression was observed at the front edge of the ascending limb of the helix with the discharge of particulate material. Suspecting a PS, further investigation through an MRI examination was requested. The contrast-enhanced MRI documented a PS characterized by a small superficial subcutaneous cyst located in front of the right external auditory canal at the front edge of the ascending limb of the helix, behind the superficial temporal artery, and behind and above the parotid gland. The cyst showed restricted diffusivity (due to purulent content) and was surrounded by inhomogeneous adipose tissue with contrast-enhancement (due to inflammatory phenomena).

To the best of our knowledge, there is a lack of clear description of MRI semeiotics of PS in the literature and this case helps to fill that gap. MRI could play a role in the pre-surgical planning of complex PS cases. Additionally, a comprehensive understanding of the MRI appearance is essential for distinguishing PS from other diseases, such as branchial fistulas, epidermal inclusion cysts, and trichilemmal cysts.