Retrotympanic lesions are usually discovered during otoscopic examination for hearing loss,
otalgia,
or tinnitus.
Most of these lesions are associated with abnormal whitish,
reddish,
or bluish coloring of the eardrum,
and the coloring helps limit the differential diagnosis. (Fig. 1 )
√ A whitish eardrum: usually suggests congenital cholesteatoma; other diagnoses like primary tumors of the middle ear are less common.
√ A reddish eardrum: the paragangliomas are most likely,
though vascular malformations are also possible.
√ A bluish eardrum: suggests different diagnoses like a dehiscent jugular bulb,
a cholesterol granuloma,
or meningoencephalocele.
Fig. 1: We classify the diseases according to the otoscopic findings into three major groups: red, blue, and white lesions.
High resolution CT and MRI of the temporal bone are mandatory when a retrotympanic mass is seen at otoscopy.
CT and MRI are complementary: which technique is most useful depends on the disease suspected in the clinical evaluation.
» We make a schematic overview of the basic anatomy of the ear and the normal otoscopy (Fig. 2 ,Fig. 3 ):
Fig. 2: Anatomic diagram of the ear: 1. Malleus, 2. Incus, 3. Stapes, 4. Cochlea, 5. Semicircular canals, 6. Facial nerve, 7. Vestibular nerve, 8. Cochlear nerve, 9. Tympanic membrane, 10. Epitympanic recess, 11. Eustachian tube, 12. Carotid. A. Ear canal, B. Middle ear, C. Inner ear, D. Internal auditory canal.
Fig. 3:
A- Otoscopy (right ear): 1. Flaccid portion, 2. Tense portion, 3. Manubrium, 4. Lateral process of the malleus, 5. Anterior fold of the malleus, 6. Posterior fold of the malleus, 7. Annulus, 8.Umbo, 9. Cone
of light.
B- Tympanic quadrants: The manubrium divides the eardrum into the anterior and posterior regions. If a line is also projected perpendicularly at the level of the umbo, the 4 classic quadrants are obtained: anterosuperior, posterosuperior, anteroinferior, & posteroinferior.