OTITIS MEDIA INTERNA IN HORSES

Otitis media/interna is a cause of facial and vestibulocochlear nerve dysfunction in horses. The causes of otitis media/interna have been as sociated with conditions that can lead to middle ear effusions and ext ension into the inner ear. Clinical signs are referable to nerve dysfu nction and/or central nervous system-involvement. Other-causes of seve nth and eighth cranial nerve dysfunction must be considered in the dia gnosis. These can be ruled out by neuroanatomic localization of the le sion and by supportive diagnostic tests. Diagnostic imaging techniques are increasingly important in the evaluation of affected horses. Find ings can support and/or confirm a diagnosis of otitis media/interna wh en the lesion has been localized to the area of the tympanic bulla, pe trous temporal bone, or proximal stylohyoid bone by means of neurologi c examination. Radiography, guttural-pouch endoscopy, and nuclear scin tigraphy have been most helpful in this regard. Otoscopy may prove to be very useful as well. Treatment involves long-term antimicrobial and antiinflammatory drugs. When there is central nervous system involvem ent, drugs that penetrate the blood-brain barrier are preferable. Prog nosis has been difficult to assess accurately but will improve with ea rlier detection and better testing of nerve function.