Failure of Epithelial Migration

Damage to the germinal epithelium of the eardrum from infection or ear mite infes­tation results in damage to the keratinocytes on the surface of the tympanic membrane (Figure 11-3).

Figure 11-1

For legend, see p. 224.

Continued

Figure 11-1—cont'd

A through E, Movement of India ink across the eardrum demonstrates epithelial migration. India ink was placed on the eardrum at the junction with the horizontal canal. Photos are taken at 2-week intervals. The entire series covered 2 months.

Figure 11-2

Accumulation of ceruminous exudates in the ear. Epithelial migration is not able to remove the waxy matter.

Figure 11-3

The patient, a 3-year-old cat, was presented with severe ear mite infestation. The ear canal was gently flushed with a dilute povidone-iodine solution to remove the ear mite debris. After cleaning, the eardrum can be seen to have a tear in it. It is here that epithelial cells that would migrate to the ear canal will stop their journey. This will result in waxy accumulations on the eardrum in the future.

Figure 11-4

Soft wax ball seen attached to the eardrum. Part of the eardrum is visible at the ventral portion of the wax ball between it and the horizontal canal.

changes to the tympanic membrane. Normal epithelial migration may be disrupted. Failure of epithelial migration may result in the accumulation of flakes of skin in the ear canal. More often, however, wax and keratin accumulate at the base of the eardrum and form either soft wax plugs (Figure 11-4) or large, hard concretions called Ceruminoliths (Figure 11-5). To find them when examining the ear canals with an otoscope, the veterinarian should follow the bend in the ear cartilage and look in the horizontal canal toward the eardrum. Ceruminoliths are found attached to the eardrum lying along the floor of the horizontal ear canal.