External auditory canal cholesteatoma: clinical and imaging spectrum

Abstract

Background and purpose: Cholesteatoma is an inflammatory lesion of the temporal bone that uncommonly involves the external auditory canal (EAC). In this large case series, we aimed to define its imaging features and to determine the characteristics most important to its clinical management.

Methods: Thirteen cases of EAC cholesteatoma (EACC) were retrospectively reviewed. Clinical data were reviewed for the history, presentation, and physical examination findings. High-resolution temporal bone CT scans were examined for a soft-tissue mass in the EAC, erosion of adjacent bone, and bone fragments in the mass. The middle ear cavity, mastoid, facial nerve canal, and tegmen tympani were evaluated for involvement.

Results: Patients presented with otorrhea, otalgia, or hearing loss. Eight cases were spontaneous, and five were postsurgical or post-traumatic. CT imaging in all 13 cases showed a soft-tissue mass with adjacent bone erosion. Intramural bone fragments were identified in seven cases. This mass most often arose inferiorly (n = 8) or posteriorly (n = 8), but it was circumferential in two cases. We noted middle ear extension (n = 5), mastoid involvement (n = 4), facial canal erosion (n = 2), and tegmen tympani dehiscence (n = 1).

Conclusion: Temporal bone CT shows EACC as a soft-tissue mass within the EAC, with adjacent bone erosion. Bone fragments may be present within the mass. The cholesteatoma may extend into the mastoid or middle ear, or it may involve the facial nerve canal or tegmen tympani. Recognition of this entity and its possible extension is important because it may influence clinical management.

Fig 1.

EACC. Used with permission (24). A, Coronal temporal bone CT image shows an EACC as a soft-tissue mass in the inferior EAC, with associated erosion of the subjacent bone (arrow). Note the medial bowing of the tympanic membrane in this postsurgical 40-year-old woman with a history of hearing loss. B, Axial temporal bone CT image in the same patient shows the soft-tissue mass filling the inferior EAC (white arrow), with anterior (black arrow) and posterior EAC erosion. Erosion involving more than one EAC wall is typical.

Fig 2.

EACC with intramural bone fragments. Used with permission (24). A, Coronal temporal bone CT image shows an EACC as a soft-tissue mass in the inferior EAC with intramural bone fragments (white arrow). Erosion of the inferior wall of the EAC (black arrow) is present. Note preservation of the scutum in this 48-year-old woman with otalgia. B, Axial temporal bone CT image in the same patient as in A shows erosion of the anterior (black arrow) and posterior (white arrow) walls of the EAC. Note the involvement of the mastoid air cells (white arrow), which requires this patient to undergo a partial radical mastoidectomy. C, Coronal temporal bone CT image shows a soft-tissue mass filling the EAC, with associated erosion of the inferior EAC (arrow). Note the intramural bone fragments. The middle ear cavity is preserved in this 74-year-old man with otorrhea.

Fig 3.

EACC with extension into the middle ear cavity. Coronal temporal bone CT shows a soft-tissue mass in the EAC, with inferior wall erosion (black arrow) and intramural bone fragments. There is extension beyond the tympanic membrane into the middle ear cavity (white arrow). Note preservation of the facial nerve canal and scutum in this 45-year-old man with otorrhea and hearing loss. Used with permission (24).

Fig 4.

Illustration of the EACC shows erosion of bone, which leaves behind intramural bone fragments (solid arrow). Note the mucosal disruption (open arrow), seen on otologic examination. Used with permission (25).