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Central Nervous System Trauma

Simon R. Platt, BVM&S, FRCVS, DACVIM (Neurology), DECVN

Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA, USA

Spinal Trauma vides a window for therapeutic intervention, we are cur-
rently less capable of halting these processes, which
Traumatic spinal cord injury (SCI) is a devastating disease include vasospasm and localized ischemia, delayed cell
in human and veterinary medicine. The majority of SCIs damage and apoptosis, ion‐mediated cell damage and
result from vehicle‐related accidents but other impor- excitotoxicity, and neuroinflammation, as well as mito-
tant causes include gunshots, dog fights, falls, accidental chondrial dysfunction and oxidative cell damage.
owner‐induced injuries, and falling objects. Clinical signs associated with spinal trauma are caused
by injury to the spinal cord, the spinal nerves as they exit
Pathophysiology of Spinal Cord Injury the vertebral canal, and the vertebral column itself. The
different injuries resulting from trauma include vertebral
The normal spinal cord is a stable structure throughout fractures, subluxations and luxations, flexion/extension
life, but it exhibits modest decrements in myelinated injuries, and traumatic disk herniations. Subluxation
axon and neuron numbers with advancing age. Its and luxation can occur in combination with a vertebral
complexity greatly exceeds that of other tissues, and its fracture or due to soft tissue disruption only, without
thin cellular processes can extend long distances, thereby evidence of vertebral injury. These injuries occur most
increasing their vulnerability. It has unique vascular frequently at the lumbosacral, thoracolumbar, and
barriers and fluid compartments. Its cellular compo- atlantoaxial junctions. Cats are more likely to suffer sac-
nents and the tissues that they form are highly suscepti- rocaudal fractures than dogs, and typically have a com-
ble to injury. Together with the brain, this organ has the bination of fracture and luxation, whereas approximately
least ability to undergo self‐repair. Increasing evidence 20% of dogs suffer a luxation only.
indicates that the spinal cord also has distinct differ- These events can cause spinal cord contusion and
ences from the brain in its injury responses. laceration, and can result in compression by bone, soft
The pathophysiology of SCI can be divided into two
phases: the initial primary injury and subsequent second- tissue or blood (hematomas). Ongoing instability can
result in repeated contusive injuries, additional laceration
ary injury.
of the cord, and increasing severity of compression.
Primary injury refers to the initial traumatic insult to Compression of the spinal cord reduces perfusion, poten-
●
the spinal cord, which results in immediate severing of tially causing neuronal and glial cell death by the second-
axons and death of spinal cord cells. ary injury mechanisms described above. Demyelination
Secondary injury invariably follows and leads to pro- is a common finding histopathologically, as a result of
●
gressive tissue damage for weeks after the initial insult. both direct damage to myelin and death of oligodendro-
It results from a complex series of related events on a cytes. Physical deformation of axons can cause failure of
number of physiologic levels. Hypotension and hypoxia ion channels, changing membrane permeability and pro-
are important preventable causes of secondary injury at ducing conduction block that rapidly reverses when
a clinical level and must be recognized and either pre- decompressed. Ongoing spinal cord compression can
vented or treated proactively. Numerous secondary also cause development of syringohydromyelia cranial to
injury mechanisms also occur on the cellular level, and the compression site, potentially causing neuropathic
although their delayed time course theoretically pro- pain in addition to further neurologic deterioration.

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical