Contributors: Kyle Braund, Rosanna Marsella

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Cause: sequel to chronic otitis externa Skin: otitis externa , ascending syndrome through the Eustachian tube.
  • 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 other imaging.
  • Treatment: antibiotics, ear flushing, bulla osteotomy if not responding.
  • Prognosis: may → otitis interna Otitis interna.
    Print off the owner factsheet on Chronic otitis Chronic otitis to give to your client.Follow the diagnostic tree for Evaluating and Managing Otitis Externa/Media Diagnostic tree: Evaluating and Managing Otitis Externa/Media.

Presenting Signs

  • Vestibular syndrome.
  • Persistent otitis externa Skin: otitis externa with purulent discharge, particularly when surgical treatment of the external canal has failed to cure the condition.

Breed Predisposition

Pathogenesis

Etiology

  • Descending infection (more common) following prolonged otitis externa Skin: otitis externa or ascending infection upper respiratory tract infection via Eustachian tube.

Predisposing Factors

General

Specific

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.
  • Can be associated with nasopharyngeal polyps.

Timecourse

  • >80% of dogs with chronic/recurrent otitis externa Skin: otitis externa develop otitis media Otitis media.
  • ?frequently undetected until severe.
  • Usually sequel to long-term otitis externa (weeks/months).

Diagnosis

Presenting Problems

  • Head-shaking, irritation and pain on palpation of the external ear canal.
  • Lethargy and inappetence.
  • Head tilt.

Client History

  • 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.

Clinical Signs

  • Intermittent slow head-shaking.
  • Affected ear tilted downwards.
  • Persistent purulent aural discharge.
  • Involvement of temporomandibular joint.
  • Facial paralysis.
  • Horner's syndrome Horner's syndrome.

Diagnostic Investigation


Radiography
Open mouth and dorsoventral views of whole skull.
  • Diffuse thickening/sclerosis of tympanic bulla wall Skull tympanic bulla normal - radiograph (open mouth) Otitis media right side - radiograph Otitis media right side - lateral radiograph.
  • Loss of normal air shadow in tympanic bulla Skull tympanic bulla disease - radiograph lateral oblique.
  • Bony destruction and proliferative changes of bulla wall.
  • Osteomyelitic changes of bulla with temporomandibular joint involvement.
Other
  • 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 anestheticpalpate 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.
  • Eustachian tube patency assessment.
  • Fluorescein does not appear at the contralateral nostril.
  • MRI - gives good details of tympanic bulla and associated changes Otitis media left side - MRI scan.
  • Exploratory surgery of bulla:
    • Necessary if non-responsive case, foreign body, neoplasia.

Bacteriology
  • Microbiology- two opinions:
    • Some authorities identify predisposing cause and treat microbial overgrowth.
    • Others use culture and sensitivity tests → vigorous antibiosis.

Differential Diagnosis


Causes of head shaking, irritation, painful external ear canalCauses of head tilt

Treatment

Initial Symptomatic Treatment

  • If concurrent otitis externa:
  • If ascending otitis media:
    • All of: Parenteral, broad-spectrum antibiosis.
    • And: Non-steroidal anti-inflammatory drugs.
  • If the patient is co-operative, and pain and ulceration of the external ear canal is not present, cleaning of the external ear canal with dilute saline through flushing and external massage in the conscious animal.
  • Removal of nasopharyngeal polyp.

Standard Treatment

  • If medical measures fail or eardrum is otherwise not accessible:
  • All of: Bulla osteotomy.
  • and: Flushing.
  • and: Broad-spectrum antibiosis.
  • If middle ear is accessible:
    • Every 3rd day, irrigate the bulla (under general anesthetic) with 0.5% cetrimide Cetrimide solution followed by sterile normal saline, or with sterile normal saline alone, until the washings are clear of debris.
      Always flush with sterile normal saline after using 0.5% cetrimide Cetrimide solution to prevent irritation.
  • If poor response to flushing or if eardrum not externally accessible:
    • Vertical canal ablation Ear: vertical canal ablation.
      May → non-healing surgical wound because this procedure will improve access to eardrum for flushing but alone will not prevent continuing discharge.

Monitoring

  • Changing quality of flushed material from ear.
  • Improvements in clinical signs.
  • Otoscopy: to check middle ear.

Subsequent Management

Treatment

  • Culture and sensitivity if initial antibiotic choice is not effective → change according to sensitivity results.

Monitoring

  • Radiology: follow-up film if clinical improvement needs confirming.

Outcomes

Prognosis

Expected Response to Treatment

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

Reasons for Treatment Failure

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

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • 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.
  • Allgoewer I, Lucas S & Schmitz S A (2000) Magnetic resonance imaging of the normal and diseased feline middle ear. Vet Rad Ultra 41 (5), 413-418 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. Philadelphia: W B Saunders. pp 986-1002.

Other Sources of Information