Equis ISSN 2398-2977

Optic nerve: neuropathy - trauma

Contributor(s): Dennis E Brooks, Graham Munroe

Introduction

  • Cause: associated with skull trauma, particularly to the occipital crest, causing damage to retrobulbar optic nerve; usually following backward falls or rearing in confined space.
  • Signs: sudden onset, unilateral/bilateral visual loss; usually with no ophthalmoscopic lesions; occasional edema and hemorrhage +/- extrusion of optic disk; subsequent optic nerve atrophy   Optic nerve: atrophy  if delay in treatment or severe damage.
  • Treatment: immediate intensive intravenous DMSO   Dimethyl sulfoxide  , NSAIDs and corticosteroids.
  • Prognosis: poor to grave.

Pathogenesis

Etiology

  • Skull trauma.

Predisposing factors

General
  • Skull trauma particularly to occipital crest.

Specific

  • Falling over backwards.
  • Rising up in starting gates, trailers or stocks with low ceilings.

Pathophysiology

  • Associated with skull trauma following backward falls or raising head upwards.
  • Retrobulbar stretching and damage to optic nerve.
  • Rupture of nerve axons due to stretching forces produced by posterior movement of brain away from the fixed canalicular portion of optic nerve.
  • Direct compression associated with edema/hemorrhage or wing fractures of basisphenoid bone   Head: fractures  .
  • Subsequent ischemic neuroretinopathy.
  • Damage to optic nerve may occur within optic canals or at a point of exit from optic foramen.

Timecourse

  • Visual loss within 24 h of injury.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Reppas G P et al (1995) Trauma-induced blindness in two horses. Aust Vet J 72 (7), 270-272 PubMed.
  • Rebhun W C (1992) Retinal and optic nerve diseasesVet Clin N A Equine Pract (3), 587-608 PubMed.


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