Introduction

• Cause: sequel to chronic otitis externa Skin: otitis externa, ascending syndrome through the Eustachian tube and hematogenous spread. Otitis media with effusion (primary secretory otitis media (PSOM) associated with auditory tube dysfunction.
• Signs: vestibular syndrome Vestibulocochlear neuritides variable depending on stage and route of infection, eg:
  • Ascending otitis media shows as lethargy, inappetence, fever, slow head-shaking transient head tilt to affected side; signs of otitis externa, ie head-shaking, scratching, pain on palpation of external canal.
• Diagnosis: signs, radiography or computer tomography.
• Treatment: topical antibiotics and glucocorticoids, analgesics, ear flushing, bulla osteotomy if not responding.
• Prognosis: may → otitis interna Otitis interna.
  Print off the owner factsheet on Chronic otitis to give to your client.

Pathogenesis

Etiology

• Descending infection (more common) following prolonged otitis externa Skin: otitis externa or ascending infection upper respiratory tract infection via Eustachian tube.
• PSOM thought to be caused by auditory tube dysfunction leading to mucous build up in middle ear.
• Cholesteatoma causes otitis media.

Predisposing factors

General

• Most common primary cause of otitis externa is allergy. Breeds prone to allergy are the most likely to develop otitis media/interna.
• Prediposing factors for otitis include conformation (dogs with pendulous or hairy ears) and life style (swimming dogs), these increase an animal risk of developing disease if a primary cause is present.
• Otitis externa Skin: otitis externa.
• Otitis media Otitis media.

Specific

• Iatrogenic damage to eardrum during ear cleaning treatment of otitis externa Skin: otitis externa.

Pathophysiology

• Descending: otitis externa → debris accumulation in contact with eardrum → eardrum weakened by infection and ruptures or penetrated by migrating grass seed → medial extension of inflammatory process → hyperemia and thickening of mucoperiosteal lining → accumulation of exudate in tympanic bulla → thickening/sclerosis of bulla → medial spread to cause otitis interna or, rarely, bulla osteomyelitis with involvement of the temporomandibular joint.
• Ascending otitis media: upper respiratory tract infection → inflammatory spread up Eustachian tube to middle ear → hyperemia and thickening of mucoperiosteal lining → accumulation of exudate → rupture of eardrum in presence of infection → ascending otitis externa and/or medial spread to cause otitis interna → (rarely) bulla osteomyelitis with involvement of temporomandibular joint.

Timecourse

• >80% of dogs with chronic/recurrent otitis externa Skin: otitis externa develop otitis media Otitis media.
• Occult otitis can exist without any obvious signs until it becomes severe.
• Usually sequel to long-term otitis externa (weeks/months).

Diagnosis

Treatment

Prevention

Outcomes