Contributors: Agnes Delauche, Rosanna Marsella, Harry Scott, Sue Paterson

 Species: Feline   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Infection involving the organs of hearing and balance housed within the bony labyrinth.
  • Cause: most commonly spread of infection from middle ear, also hematogenous route or ascending infection through the Eustachian tube.
  • Signs: head tilt, circling and nystagmus (vestibular syndrome); unilateral deafness.
  • Diagnosis: history, clinical signs, neurological assessment, advanced diagnostic imaging (MRI, CT).
  • Treatment: broad-spectrum antibiotics initially, then based on cytology and bacterial culture of material collected on myringotomy where possible.
  • Prognosis: good but high frequency of residual deficits.
    Print off the owner factsheet on Chronic otitis to give to your client.

Presenting Signs

Pathogenesis

Etiology

  • Extension of opportunistic infection from otitis media/externa.
  • Hematogenous spread.

Specific

Pathophysiology

Inner ear disease

  • Damage to cochlea:
    • Sensory nerve endings within the cochlea damaged by infection/trauma/ototoxicity leading to deafness.
  • Damage to vestibular apparatus:
    • Vestibular system consists of proprioceptors (saccule, utricle and semicircular canals) within the inner ear (petrosal temporal bone), the vestibular nerve (VIII), four brainstem nuclei and the cerebellum. Peripheral vestibular dysfunction (PVD) is as a result of damage to structures with the petrosal temporal bone. Central vestibular dysfunction (CVD) is due to damage to structures in the brain stem and cerebellum.
    • PVD most commonly extension of otitis externa/otitis media or idiopathic vestibular syndrome (IVS).
    • CVD most commonly caused by neoplasia, inflammatory or infectious disease, thiamine deficiency Thiamine deficiency, vascular, traumatic or toxic conditions.

Diagnosis

Presenting Problems

  • Vestibular syndrome.
  • Deafness.

Client History

  • Concurrent otitis media/externa.
  • Recent treatment of otitis by instilling potentially ototoxic agents into ear.
  • Recent bulla irrigation or bulla osteotomy Bulla osteotomy.
  • Head trauma Head: trauma.

Clinical Signs

  • Otitis interna usually presents with signs of PVD.
  • Head tilt, affected side down Otitis media: tilted head.
  • Circling towards affected side.
  • Horizontal nystagmus, fast component away from affected side and not affected with head position.
  • Rolling/falling to affected side.
  • Unilateral deafness present Deafness: acquired, detectable by Brainstem auditory evoked response (BAER) testing in specialist center Hearing tests.
  • Positional ventral strabismus in ipsilateral eye.
  • Vomiting Vomiting.
  • Concurrent otitis media Otitis media.
  • General dullness and inappetence.
  • Unilateral facial paralysis Facial nerve neuropathy, involving upper and lower face but only with concurrent otitis media.
  • Horner's syndrome Horner's syndrome Eye: Horners syndrome 01 - affected right eyeEye: Horners syndrome 01 - normal left eyeEye: Horners syndrome 02Eye: Horners syndrome 05 - with left facial nerve paralysis.

Diagnostic Investigation

Other

  • Neurological assessment Neurological examination:
    • Necessary to differentiate from CVD.
    • Head tilt.
    • Ataxia Ataxia.
    • Horizontal nystagmus with quick phase away from side of lesion. With central lesions, positional and vertical nystagmus may be present, ie direction is altered with head position.
    • With central vestibular lesions, paresis and reduction or absence of proprioception can occur in the ipsilateral limbs. There may also be evidence of multiple cranial nerve involvement.
  • Otoscopic examination:
    • Concurrent otitis media/externa where disease has developed from ear disease.
  • Radiography:
    • Only of use in identification of otitis media (but up to 25% of otitis media cases have no radiographic changes), neoplasia Ear: otitis media and polyp - radiograph VDor traumatic injury to skull.
  • Brainstem auditory-evoked response (BAER):
    • Evidence of hearing loss.

Differential Diagnosis

Peripheral vestibular syndrome

Central vestibular syndrome

Treatment

Initial Symptomatic Treatment

  • Broad-spectrum antibiotics Therapeutics: antimicrobial drug initially but where possible they should be based on cytology, and culture and sensitivity of material collected from the middle ear by myringotomy Myringotomy. Drugs needed for 6-8 weeks in chronic cases.
  • See also ear therapeutics Therapeutics: ear.

Standard Treatment

All of Broad-spectrum, bacteriocidal antibiosis Therapeutics: antimicrobial drug Therapeutics: ear.
And Ventral bulla osteotomy Bulla osteotomy with bulla irrigation, if evidence of unresponsive otitis media.

Monitoring

  • Gradual resolution of neurological deficits, (balance, circling, nystagmus).
    In many cases the neurological deficits are irreversible but compensation occurs for the vestibular deficits.
  • Resolution of signs of otitis media.

Subsequent Management

Monitoring

  • Neurological re-examination.

Outcomes

Prognosis

  • Good in straightforward cases of otitis interna/labyrinthitis. Damage to delicate nerve endings is likely to be irreparable but disease is rarely bilateral, so some degree of compensation occurs; however, facial paralysis is usually irreversible.

Expected Response to Treatment

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

Reasons for Treatment Failure

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Negrin A, Cherubini G B & Platt S (2010) Clinical signs, magnetic resonance imaging findings and outcomes in 77 cats with vestibular disease: a retrospective study journal of feline medicine and surgery. J Feline Med Surg 12 (4), 291-299 PubMed.
  • Bischoff M G & Kneller S K (2004) Diagnostic imaging of the canine and feline ear. Vet Clin North Am Small Anim Pract  34 (2), 437-458 PubMed.
  • Trevor P B & Martin R A (1993) Tympanic bulla osteotomy for treatment of middle-ear disease in cats - 19 cases (1984-1991). JAVMA 202 (1), 123-128 PubMed.
  • Boothe H W Jr. (1988) Surgical management of otitis media and otitis interna. Vet Clin North Am Small Anim Pract 18 (4), 901-911 PubMed.
  • Schunk K L (1988) Disorders of the vestibular system. Vet Clin North Am Small Anim Pract 18 (3), 641-665 PubMed.
  • Shell L G (1988) Otitis media and otitis interna - etiology, diagnosis, and medical management. Vet clin North Am Small Anim Pract 18 (4), 885-899 PubMed.

Other Sources of Information