562 DISEASES/DISORDERS
(a)(c)(b)Fig. 37.23.(a) Cerumen cyst occupying the external ear canal of a 5-year-old male-castrate mix breed dog.
(b) Under visualization with video-otoscopy, the cerumen cyst is punctured and drained of tan-yellow fluid by
rigid catheter (asterisk). (c) Following drainage, the wall of the cerumen cyst has retracted towards the dorsal
aspect of the external ear canal (white arrowhead). Remnants of the tympanum are visualized on the ventral
aspect of canal (red arrowhead). The ruptured tympanic membrane allows visualization of the tympanic bulla
(yellow arrowhead).
Fig. 37.24.Myringotomy procedure in a 12-year-old male-castrate DSH. The myringotomy tube (red asterisk)
is inserted through the tympanic membrane (yellow asterisk) ventral and caudal to the manubrium of the malleus
(m) to produce a defect in the tympanum (white arrowhead), permitting sample collection and cleaning of the
tympanic bulla.