Ceruminoliths

If the dog in which a ceruminolith is developing has a large number of hairs origi­nating from around the annulus of the tympanic membrane, the hairs are included in the matrix of the ceruminolith.

Figure 11-5

A hard concretion at the eardrum of a 15-year-old Poodle. Note the hairs included in the matrix of the ceruminolith. Also notice the normal ear canal epithelium.

Figure 11-6

This large ceruminolith in a German Shepherd illustrates the inclusion of bristly hairs in the wax ball. In this photo, the thick hairs are touching the horizontal ear canal wall and causing discomfort. The horizontal ear canal epithelium appears normal.

Figure 11-7

Soft wax ball. The owner of a 4-year-old cat presented the animal for diminished hearing and head tilt. The history indicated that the cat had recurrent ear mites as a kitten.

When epithelial migration is prevented from continuing, the keratinocytes on the eardrum form layers on top of each other and are pushed backward toward the eardrum. Over time, the net effect is significant accumulation of desquamation products that cannot clear away from the eardrum and out of the ear canal. Cerumen and hairs mix into the heap. Cytologic smears of these concretions will show heavy growth of Malassezia yeasts.

These waxy accumulations can become quite large, some of them measuring 1 or 2 inches in length. Although innocuous in appearance, ceruminoliths plugging the horizontal ear canal diminish hearing. In certain head positions, the weight of the ceruminolith pushes against the eardrum and may cause increased air pressure within the middle ear cavity, leading to signs of vestibular disease (Figure 11-7).

Otoscopic examination of a ceruminolith reveals that there is a base attached to the eardrum, with the body of the mass freely movable and unattached to the surrounding ear canal. The tips of long hairs may be seen on the surface. In many cases the peripheral portion of the pars tensa can be visualized.