external otitis

The physiological removal of foreign bodies in the horse’s external ear canal is best achieved by head-shaking. However, external otitis in the horse induces moderate to severe pain: therefore, the horse does not shake his head. The causes of external otitis are dust, water in the external ear canal, keratin, and ceruminous debris. The clinical symptoms are ear discharge, skittishness, facial nerve paresis, and/or head tilt. After the horse has been sedated, the most important diagnostic procedure is the endoscopy of the cartilaginous and osseous part of the external ear canal, including the evaluation of the transparency of the tympanic membrane. The clinical complications of external otitis are hearing loss, facial nerve paresis, head tilt, hypertrophy of the tympanostylohyoideum, and corneal ulcers. The most important treatment is soaking up the exudate in the osseous part of the external ear canal using small cotton balls which are held by the foreign body forceps of the endoscope. Based on the results of the culture of exudate and the antibiogram, an antibacterial drug must be administered orally for 3 to 4 weeks. At this time, an endoscopy of the external ear canals and guttural pouches also has to be done. Based on the outcome of the endoscopy, endoscopic and clinical investigations have to be performed six months later as well. Only 7/19 horses had a normal osseous part of the external ear canal with a transparent tympanic membrane, including normal hearing measured by the brainstem auditory-evoked response after one month of treatment.