Keratosis obturans is characterized by the plugging and occlusion of the external auditory meatus with debris made up of keratin, leading to enlargement of the ear canal without bone erosion. The clinical manifestations include bilateral otalgia and conductive hearing loss. The diagnosis is based on the patient history, physical examination, and appropriate studies.
Keratosis obturans is a disease of the external auditory meatus in which keratinaceous debris accumulate and form a plug in the ear canal, thereby causing occlusion and widening of the bony component [1] [2]. This rare disorder was previously considered as a variation of cholesteatoma of the external auditory canal (CEAC) but is now regarded as a distinct condition [1]. While the etiology is not fully understood, keratosis obturans is classified as either inflammatory, which is associated with a recent acute infection or silent, which does not have a predisposing event [3]. The estimated incidence is 4 to 5 cases per 1000 patients with ear complaints [3].
This disorder occurs predominantly in younger individuals [1] [4] who manifest with acute bilateral ear pain and conductive hearing loss [1] [5]. Furthermore, discharge is not a frequent symptom in these patients [4] [6]. Moreover, the cases are overall healthy [5]. Additionally, keratosis obturans is associated with bronchiectasis and sinusitis [1] [7].
Complications
There are a few incidences in the literature describing facial nerve palsy in patients with keratosis obturans [5] [8] [9]. This neurologic sequela may develop secondary to inflammation [5] or bone erosion [8] [9], of which the latter is not a feature of keratosis obturans [1].
Physical exam
Otoscopy typically reveals an occluding mass in the ear canal [10]. Additionally, tuning fork [5] and pure tone audiometry (PTA) [10] are performed to test and confirm conductive hearing loss.
The victim should be evaluated for neurological deficits such as facial nerve palsy. Additionally, a full head, neck, and oropharynx exam should be completed.
The clinical presentation should raise suspicion for keratosis obturans and CEAC, in which a workup consisting of the patient history, physical exam, and appropriate tests will help determine the diagnosis.
Imaging
Key imaging modalities include high-resolution computed tomography (HRCT) scan of the temporal bone, which will display the soft-tissue accumulation residing in the external ear canal(s) [5] [11] and dilation of the walls of the canal [2] [11]. These findings are typically bilateral in people with keratosis obturans but unilateral in CEAC [12]. Moreover, imaging of the external auditory canal with axial CT reveals no necrosis or bone erosion [1]. Very importantly, keratosis obturans does not involve osseous erosion of the canal as seen with CEAC [2] [12].
Pathology
Keratosis obturans is associated with an enlarged ear canal, epithelial hyperplasia, and subepithelial inflammation [13]. Moreover, histopathological analysis of the debris reveals lamellar keratinous elements [1].
Other
In addition to performing a complete physical exam including a focus on the head and neck region, testing with the tuning fork and PTA are important to evaluate hearing loss [5] [10].