The blood has nowhere to go, so it accumulates-and the pinna can start to look like a big, swollen balloon. Flanders, “may scratch its head frequently and, in the process, rupture blood vessels inside the pinna. A relatively common source of such obsessive scratching, according to James Flanders, DVM, associate professor of surgery at Cornell University’s College of Veterinary Medicine, is otitis externa stemming from the proliferation of ear mites within the outer ear. Otitis externa may result from a yeast or bacterial infection or the invasion of parasites within the ear canal. The most frequent cause, however, is the trauma that a cat may inflict upon itself by persistently and furiously scratching at its own ears to relieve the relentless itching stemming from otitis externa, an infection of the external ear canal.

The swelling can be caused by, for example, blunt trauma to the skull or by deep wounds to the ears that a cat may sustain in fights with other animals. Although normally a sturdy structure, protected on both the front and back surfaces by a layer of tough skin, the pinna-directly exposed as it is to the outside world-is subject to various traumas that can lead to a swelling called aural hematoma. A thin, funnel-shaped, mobile structure, supported internally by cartilage and tiny muscles that give the ear its shape, the pinna serves to collect sound waves from the external environment, concentrate them, and channel them into the depths of the auditory canal-the middle and inner ears. While structurally much simpler than the other components of a cat’s hearing apparatus, the pinna-the fleshy, visible portion of the outer ear-is an essential part of the feline auditory system.

Canine aural hematoma