Equis ISSN 2398-2977

CNS: brain trauma

Contributor(s): Caroline Hahn, Jenny MacKay, Ruth Morgan, Katrin Schmallenbach

Introduction

  • Cause: brain trauma is usually caused by an injury. The three most common causes in the horse are blunt trauma, eg collision with an object, fracture of the basilar bones of the skull due to the horse flipping over backwards, and temporohyoid osteopathy with secondary fracture of the petrous temporal bone.
  • Signs: depend on the site and severity of brain injury.
  • Diagnosis: accurate history, neurologic examination, radiography.
  • Treatment: fluid therapy, corticosteroids, surgery.

Pathogenesis

Etiology

  • Head trauma in horses is usually a result of kicks from other horses, falling, running into solid objects, or occasionally by a penetrating wound or a severe blow to the head from a handler.
  • Impact to the frontal or parietal region of the head often leads to cerebral trauma.
  • Brainstem trauma is more likely when the impact is to the poll or the horse flips over backwards.
  • Brainstem signs also occur secondarily to compression from cerebral swelling.
  • Cerebellar trauma is usually associated with impact to the poll.

Pathophysiology

  • In cranial trauma, brain pathology may be divided into primary and secondary effects:
    • Primary: laceration or fracture of skull; parenchymal contusion (focal hemorrhage and laceration).
    • Secondary: meningeal, parenchymal and/or intraventricular hemorrhages; brain swelling, due to edema; hypoxic brain damage, due to increased ICP, excitotoxicity due to excessive release of excitatory neurotransmitters, calcium dysregulation.
  • The degree of brain damage is heavily related to:
    • Length of time of trauma.
    • Velocity of traumatic force.
    • Severity of trauma.
  • A small bang on the head is unlikely to cause any brain trauma.
  • The term concussion as applied to humans is probably not relevant to the horse, as a concussion is a transient, immediate loss of consciousness associated with a short period of amnesia that follows head trauma in humans; there is usually no grossly discernable pathologic change, and the mechanisms are not fully understood; because amnesia cannot be determined in horses, this term is not accurate for this species.
  • The brain is encased in the bony calvarium surrounded by CSF, but is only firmly attached at the base of the skull by the cranial nerve roots and major blood vessels   →   this allows the brain to move in a somewhat rotary fashion within the cranium when blunt forces are applied to the skull   →   the result is damage to the superficial cortex (contusions and lacerations) and shearing and tearing of axons in the white matter.
  • This occurs especially near the junction of the more mobile portions of the brain (cerebral hemispheres) and the brainstem.
  • Contusionsoccur under the point of impact (coup) or opposite the site of impact (contrecoup) and can range from small superficial petechie of the cortex to hemorrhagic malacia of large areas of the brain.
  • Hematomascan be epidural (frequently associated with a skull fracture), subdural, subarachnoid, or parenchymal.
  • Fractures may or may not accompany impacts causing brain trauma.

Timecourse

  • Secondary events, like expanding hematomas, cerebral edema, displacements of portions of the brain, ischemic or hypoxic damage, and meningitis (in case of penetrating injuries) can be critical in the outcome.

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.
  • De Zani D et al (2013) Magnetic resonance features of closed head trauma in two foals. Equine Vet Educ 25 (10), 493-498 VetMedResource.
  • Scrivani P V (2013) Neuroimaging in horses with traumatic brain injury. Equine Vet Educ 25 (10), 499-502 VetMedResource.
  • Lacombe V A, Sogaro-Robinson C & Reed S M (2010) Diagnostic utility of computed tomography imaging in equine intracranial conditions. Equine Vet J 42 (5), 393-399 PubMed.
  • Reed S M (2007) Head trauma: A neurological emergency. Equine Vet Educ 19 (7), 365-367 VetMedResource.
  • Hahn C (2006) The wobbly horse: differential diagnoses. In Pract 28 (1), 8-13 VetMedResource.
  • Ragle C A (1993) Head trauma. Vet Clin North Am Equine Pract (1), 171-183 PubMed.
  • Sinha A K, Hendrickson D A & Kannegeiter N J (1991) Head trauma in two horses. Vet Rec 128 (22), 518-521 PubMed.

Other sources of information

  • Summers B A, Cummings J F & De Lahunta A (1995) Injuries to the Central Nervous System. In: Veterinary Neuropathology. Mosby Year Book.


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