![]() 16 Less common causes of pinnal dermatitis may include adverse food reaction, parasitic mange, vasculitis, and ectoparasitism. ![]() Pinnal dermatitis has been described in horses and most commonly develops secondary to atopic dermatitis, fly bite trauma, insect bite hypersensitivity, solar dermatitis, or dermatophytosis. However, horses are able to rub the ears with their hind feet as well as against solid objects and can violently shake the head, all of which have the potential to damage small auricular vessels. 15 Horses and small animal species with irritating ear conditions tend to self-traumatize differently horses are unable to scratch the pinnae as readily as dogs or cats because horses lack claws. 14 Importantly, in horses, a unique sequela of otitis media is temporohyoid osteoarthropathy, which can result in fracture of the petrous temporal bone. 13 Pathological changes in the ear canal of horses occur secondary to otitis media or by extension of auditory tube diverticulum (guttural pouch) infection. The difference in incidence of aural hematoma between horses and small animal species may be related to the infrequency of primary otitis externa in horses. 10, 11, 12 Anecdotally, aural hematomas are rare in horses, and there are no reports detailing the possible underlying causes, to the authors' knowledge. 7, 8, 9 For any affected animal, identification of the cause of the aural hematoma is important when working toward treatment and resolution and for the prevention of additional hematoma formation.Īural hematomas in swine, sheep, and guinea pigs have also been reported. 5, 6 In dogs with aural hematomas, there is often concurrent otitis externa, which is a pruritic, inflammatory condition affecting the external ear canal with multiple overlapping predisposing and perpetuating factors along with primary and secondary causes. The exact pathogenesis of aural hematoma remains unclear, 4 and theories include trauma, hypersensitivity diseases, ectoparasitism, increased capillary fragility (eg, associated with hyperadrenocorticism), and autoimmune diseases. 1, 2, 3 The pressure from the accumulation of blood causes pain and irritation, triggering self-trauma and exacerbation of the injury. In small animal practice, aural hematoma is a commonly diagnosed condition and is defined as hemorrhage occurring between the skin and cartilage of the concave portion of a pinna.
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