Otitis media

• 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.

• Head shaking.
• Head tilt (ipsilateral).
• Otorrhea.
• Horner's syndrome (ipsilateral) Horner's syndrome.
• Facial nerve paralysis Facial nerve neuropathies.
• Pain on opening mouth.
• Persistent otitis externa Skin: otitis externa with purulent discharge, particularly when surgical treatment of the external canal has failed to cure the condition.
• Otitis interna Otitis interna.
• Fever Pyrexia: overview.

• Shown to be predisposed to secretory otitis media:
  • Cavalier King Charles Spaniel Cavalier King Charles Spaniel.
  • French Bulldog French Bulldog.
  • West Highland White Terrier West Highland White Terrier.
  • Cocker Spaniel Cocker Spaniel.

• 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.

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.

• 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.

• >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).

• Head-shaking, irritation and pain on palpation of the external ear canal.
• Lethargy and inappetence.
• Painful to open mouth (yawning, catching ball, eating hard food).
• Head tilt.
• Facial nerve paralysis.
• Deafness Deafness: acquired (PSOM) due to conduction loss.

• Head-shaking.
• Lethargy and inappetence.
• Characteristic head tilt with affected ear pointed downwards for a short time after head-shaking.

• Persistent, refractory otitis externa.
• Recent upper respiratory tract infection.

• Intermittent slow head-shaking.
• Affected ear tilted downwards.
• Persistent purulent aural discharge.
• Otitis interna Otitis interna.
• Involvement of temporomandibular joint.
• Facial nerve paralysis.
• Horner's syndrome Horner's syndrome. Uncommon as a sequel in the dog.

Neurological examination

• Facial nerve paralysis.
• Horner's syndrome Horner's syndrome.

Radiography

• Diffuse thickening/sclerosis of tympanic bulla wall   .
• Loss of normal air shadow in tympanic bulla .
• Bony destruction and proliferative changes of bulla wall.
• Osteomyelitic changes of bulla with temporomandibular joint involvement.

Computed tomography

• Presence of soft tissue/bony changes within bulla where chronic inflammation is present Computed tomography: head  . Fluid visible with PSOM.

Other

• Video-otoscope:
  • Tympanic membrane often obscured by discharge, fluid.
  • Defect in eardrum between malleus and ventral tympanic sulcus.
  • If longer-standing case, remnants of eardrum may be difficult to see.
  • If long-standing otitis externa, eardrum is gray color before perforating.
  • Ruptured eardrum in healthy dog with no sign of otitis.
  • Under general anesthetic palpate eardrum using a blunt needle or probe.
    Perform with care - danger of rupturing eardrum.
  • If probe passes through damaged eardrum → tap medial wall of tympanum (sharp bony tapping sensation).
  • If probe touches granulation tissue within tympanum → dull tap.
• Exploratory surgery of bulla:
  • Necessary if non-responsive case, foreign body, neoplasia.

Bacteriology

• Cytology and culture and sensitivity Bacteriology may help if discharge present from middle ear. This can be collected through a ruptured tympanic membrane or by myringotomy Myringotomy.

Causes of head shaking, irritation, painful external ear canal

• Otitis externa Skin: otitis externa.
• Aural hematoma Ear: aural hematoma drainage.
• Aural foreign body.
• Aural neoplasia.

Causes of head tilt

• Otitis interna Otitis interna.
• Idiopathic peripheral vestibular disease.
• Congenital peripheral vestibular disease Vestibulocochlear neuritides Intervertebral disk: type 2 herniation.
• Central vestibular disease.
• Canine geriatric vestibular disease Vestibular disease: geriatric.
• Toxicity.
• Cerebellar disease Brain: cerebellar disease.

• If concurrent otitis externa:
  • Topical antiseptic flush (EDTA tris + 0.2% chlorhexidine Chlorhexidine) and topical antibiotics and glucocorticoids. Off license aqueous solutions of enrofloxacin Enrofloxacin and dexamethasone Dexamethasone may be used.
  • And: Oral corticosteroid therapy, eg prednisolone Prednisolone.
  • And: Analgesic gabapentin Gabapentin or tramadol Tramadol.
• If ascending otitis media:
  • All of: Parenteral, broad-spectrum antibiosis.
  • And: Non-steroidal anti-inflammatory drugs.

• If middle ear is accessible and diagnostic imaging does not show signs of chronic irreversible change:
  • Flush the bulla (under general anesthetic) with sterile normal saline solution followed by sterile normal saline, or with sterile normal saline until the washings are clear of debris. After this use a second flsuh of EDTA tris with 0.2% chlorhexidine Chlorhexidine as an antiseptic flush. This will have antipathogenic effects and potentiate topical antibiotics.
  • Instill aqueous solution of antibiotics (based where possible on culture and sensitivity) and dexamethasone Dexamethasone directly into the bulla after flushing.
  • Give injection of anti-inflammatory dose of dexamethasone and analgesia before waking dog.
  • Send home on systemic steroids (prednisolone Prednisolone) at anti-inflammatory doses over two weeks.
  • Off license topical solution of EDTA tris with 0.2% chlorhexidine Chlorhexidine with antibiotic and steroid added to it instilled into the ear daily.
  • Analgesic – gabapentin.
• If middle ear is not accessible due to chronic change in the canal and diagnostic imaging does not show signs of chronic irreversible change:
  • Give systemic steroids (prednisolone Prednisolone) at anti-inflammatory doses for two weeks before general anesthesia and treat as above.
• If the ear is chronically irreversibly damaged, ie changes in canal unresponsive to systemic prednisolone or advanced imaging shows irreversible change:
  • Total ear canal ablation Ear: vertical canal ablation and bulla osteotomy Bulla osteotomy.

• Changing quality of flushed material from ear.
• Resolution of infection and inflammation as assessed by cytology.
• Improvements in clinical signs.
• Otoscopy: to check middle ear.

• Good: except where chronic irreversible change is present and where animals predisposed to otitis externa Skin: otitis externa.

• Improvement in demeanor over 24-48 h.
• Improvement in head-shaking/aural discharge over 1-2 weeks.

• Lack of client compliance.
• Client inability to maintain treatments.
• Financial constraints.
• Resistance to antibiotics.
• Chronic irreversible change.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Paterson S (2018) Brainstem auditory evoked responses in 37  dogs  with  otitis  media  before and after topical therapy. J Small Anim Pract 59 (1), 10-15 PubMed.
• Garosi L S, Dennis R, Penderis J, Lamb C R, Targett M P, Cappello R & Delauche A J (2001) Results of magnetic resonance imaging in dogs with vestibular disorders - 85 cases (1996-1999). JAVMA 218 (3), 385-391 PubMed.
• Dvir E, Kirberger R M & Terblanche A G (2000) Magnetic resonance imaging of otitis media in a dog. Vet Rad Ultra 41 (1), 46-49 PubMed.
• Garosi L S, Lamb C R & Targett M P (2000) MRI findings in a dog with otitis media and suspected otitis interna. Vet Rec 146 (17), 501-502 PubMed.
• McKeever P J, Torres S M (1997) Ear disease and its management. Vet Clin North Am Small Anim Pract 27 (6), 1523-1536 PubMed.

Other sources of information

• Rosychuk R A Wet al (2000) Diseases of the ear. In: Textbook of Veterinary Internal Medicine. 5th edn. Eds: S J Ettinger & E C Feldman. W B Saunders, USA. pp 986-1002.