Etiology is either congenital or acquire. Congenital deafness can be an inherited genetic mutation or as a result from toxic or viral damage in utero. Acquired deafness can be due to age, trauma, infection, loud noises, blockage of ear canal, chronic otitis externa, ear mites, AB/ototoxic drugs, parotitis, guttural pouch disease or conditions involving the brainstem such as a tumor. Any of these conditions can lead to damage of the auditory structures or nerve pathways within the internal ear. Older horses and those exposed to loud sounds are predisposed for the acquired type while (foals) are predisposed for the congenital type. Signs and symptoms include, hearing sound, but can’t localize it (unilateral), doesn’t pay attention, easier, notice behavioural or performance deficits, head tilt or head shaking and abnormal gait. test (brainstem auditory evoked response). This is when electrodes are placed under the skin around the ear and the cochlea & auditory pathways are assessed. Testing a horse’s reaction to loud sounds can help with early diagnosis. Diagnosis is the Treatment include being loud & clear with voice commands. There may be potential for reversal depending on the cause, which can involve treating the underlying condition. This will depend on permanent damage to the auditory structures. Fortunately, horses compensate well for hearing loss and can still have successful careers.
Other conditions that affect the ear that have been previously discussed include:
Aural plaques
Dentigerous cysts
Sweet Itch
Sarcoids
Squamous cell carcinoma
422
Made with FlippingBook Publishing Software