Contributors: Kyle Braund

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Cause: infection via middle ear or through hematogenous spread.
  • Signs: head tilt, circling and nystagmus (vestibular syndrome).
  • Deafness and disturbances of balance occur together.
  • Facial nerve and sympathetic trunk can be involved in middle ear. Virtually always unilateral.
  • Important to differentiate this disorder from central vestibular disturbances.
    Print off the owner factsheet on Chronic otitis to give to your client.

Presenting Signs

  • Vestibular syndrome.
  • General dullness and inappetence.
  • Unilateral facial paralysis.
  • Rolling and falling towards affected side.
  • Hemifacial spasm on affected side.

Breed Predisposition

  • Breeds prone to otitis externa, eg Spaniels.

Pathogenesis

Etiology

  • Extension of opportunistic infection by Staphylococcusspp Staphylococcus spp ,Streptococcusspp Streptococcus sppMalassezia,Clostridium welchii and (especially) Pseudomonas aeruginosa Pseudomonas aeruginosa.
  • Iatrogenic: trauma due to excessive pressure from overzealous irrigation or use of ototoxic compounds in irrigating middle ear.
  • Idiopathic form: hematogenous spread of infectious agent, possibly viral.
  • Trauma to head (rare).

Predisposing Factors

General

Specific

Pathophysiology

  • Trigger factor usually unilateral spread of otitis media through round cochlear window to inner ear → in process facial nerve and sympathetic trunk to eye may be damaged → facial paralysis and partial or complete Horner's syndrome on affected side → loss of function of cochlea and semicircular canals → unilateral deafness and disturbance of balance.
Other trigger factors
  • Direct hematogenous infection of inner ear.
  • Iatrogenic damage during treatment of otitis media, through overzealous irrigation or use of ototoxic compounds for irrigation.
  • Head trauma → damage to round cochlear window → leakage of perilymph from semicircular canals.

Diagnosis

Presenting Problems

  • Vestibular syndrome.

Client History

  • Concurrent long-term otitis externa Skin: otitis externa.
  • Concurrent otitis media Otitis media.
  • Recent treatment of otitis by instilling potentially ototoxic agents into ear.
  • Recent bulla irrigation or bulla osteotomy Bulla osteotomy.
  • Head tilt.
  • Vomiting.
  • Circling.
  • Head trauma.
  • Seizures.

Clinical Signs

  • Head tilt, affected side down.
  • Circling towards affected side.
  • Nystagmus, fast component away from affected side.
  • Stagger towards affected side.
  • Unilateral deafness present, but only detectable with sophisticated audiological tests.
  • General dullness and inappetence
  • Unilateral facial paralysis, involving upper and lower face.
  • Rolling and falling in direction of lesion.
  • Partial or complete Horner's syndrome: miosis (small pupil), slight ptosis (drooping upper eyelid), enopthalmos (sunken eye), protrusion of third eyelid, conjunctival flare.
  • Bilateral otitis interna.
  • Hemifacial spasm on affected side.
Auroscopic examinationFull neurological examination
  • Findings if central vestibular involvement:
    • Abnormal function of cranial nerve V (trigeminal) - sensory to face; cranial nerve VI (abducens) - eye position → downward strabismus (squint); cranial nerve IX (glossopharyngeal) - gag response; cranial nerve X (vagus) - vocal capacity; cranial nerve XII (hypoglossal) - lingual function.
    • Deficits in hopping and placing responses.
    • When held up, dog's body turned towards side of lesion.
    • Unilateral hypermetria.
    • History of recent onset of seizures.

Diagnostic Investigation


Radiography
  • To diagnose chronic otitis media Otitis media.
  • Absence of normal air shadow in tympanic bulla.
  • Diffuse thickening of bulla wall.
  • Bony destruction and gross bony proliferative changes in the bulla.
  • Gross bony proliferative changes with involvement of the temporomandibular joint.
Other
  • Examination under anaesthesia:
  • Eardrum rupture identified by palpation with blunt needle or probe Otitis media.
  • Eustachian tube not patent Otitis media.
    Only test for Eustachian tube patency when a cuffed endotrachial tube is in place.
  • Caloric stimulation:
  • When otitis interna present, no nystagmus initiated by irrigating external ear canal with warm or cold water.
Bacteriology
  • Microbiology:
  • Bacteriology and sensitivity of aural discharge: mixed infection, including yeasts, susceptible to broad-spectrum antibiotics or polypharmaceutical preparations.

Differential Diagnosis


Peripheral vestibular syndromeVestibular syndrome with additional central nervous system signs

Treatment

Standard Treatment

  • All of: Broad-spectrum, bacteriocidal antibiosis.
  • and: Oral corticosteroids.
  • and: Bulla osteotomy with bulla irrigation if evidence of otitis media Otitis media.
Vestibular osteotomy if marked tissue changes in tympanic bulla, eg granulation tissue or bony proliferation.

Monitoring

Subsequent Management

Monitoring

  • Neurological re-examination.

Outcomes

Prognosis

  • Reasonable.

Expected Response to Treatment

  • Neurological signs resolve over a long time period (months) if effective treatment given.
  • Head tilt may be permanent.

Reasons for Treatment Failure

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Garosi L S et al (2001) Results of magnetic resonance imaging in dogs with vestibular disorders - 85 cases (1996-1999)JAVMA 218 (3), 385-391 PubMed.
  • Dvir E et al (2000) Magnetic resonance imaging of otitis media in a dog. Vet Radiol 41 (1), 46-49 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