CNS Traumatic Injury - Pathology

Contusion

• "Contusion" is the term used to indicate focal haemorrhage within the brain.
  • Two further terms are used to describe the location of the contusive injury:
    • Coup
    • Contrecoup

Coup and Contrecoup

• The brain is smaller than the cranial vault, and so is free to move inside the skull.
• Before trauma occurs, the head is moving.
  1. The first point of impact is where a solid object hits the head. This suddenly stops the head's movement.
     • The force of impact stops the head moving, but the brain does not stop so quickly.
  2. The brain strikes the inside of the skull at the first point of impact.
     • This point is called the coup lesion.
  3. The brain has moved away from the centre of the cranium, towards the side of the coup lesion. This causes stretching and tearing of vessels and nerves on the opposite side to the original impact
     • This is the contrecoup lesion.

Laceration

• Tearing of the CNS is known as lacreation.
• This may be caused by
  • Bone within the skull
    • For example, a fractured skull
  • Penetrating objects
    • For example, bullets.
• Laceration is the most severe and serious form of traumatic injury as it carries the additional risk of contamination or infection.

Haemorrhage

• Haemorrhage may:
  • Follow contusion injury
  • Result from endothelial damage
• Locations of haemorrhage may be:
  • Epidural
  • Subdural
  • Leptomeningeal
  • Cerebral

Compression

• Compression may arise within or outside the spinal cord.
• Causes of compression include:
  • Abscess
    • Abscesses may be extradural, vertebral or intervertebral.
  • Fracture of vertebral bodies
    • Traumatic fracture
    • Pathological fracture, due to abscess, metabolic causes or neoplasia.
  • Neoplasia
  • Intervertebral disk disease
    • Prolapsed disks can cause acute or chronic compression.
  • Malformations
    • Wobbler horses
      • Caused by stenotic myelopathy.
      • The vertebral canal narrows due to malformation and malarticulation of the cervical vertebrae (usually C3-C4)
    • Cervical vertebral malformation-malarticulation in dogs has a similar pathogenesis to wobbler horses
    • Atlantoaxial subluxation of toy dogs.
      • A hypoplastic dens leads to subluxation.

Pathology

• Lesions associated with focal compressive spinal cord injury are similar regardless of cause.

Gross

• The spinal cord may be indented or flattened.

Histological

• The myelin sheath may balloon in all funiculi.
• Axonal swelling and loss is seen.
• Macrophages appear within days and remove debris within myelin "digestion chambers".
• Neuronal loss, gliosis, malacia and oedema may also be apparent.