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Acute Spinal Cord Injury (SCI)

Neurological Grading, Pathophysiology, and Evidence-Based Management

Acute spinal cord injury (SCI) is one of the most common and devastating neurologic emergencies seen in veterinary practice. The etiology is broadly divided into compressive disorders (e.g., Hansen Type I Intervertebral Disc Extrusion [IVDE], vertebral fractures/luxations) and non-compressive/concussive disorders (e.g., Acute Non-Compressive Nucleus Pulposus Extrusion [ANNPE], Fibrocartilaginous Embolism [FCE]).

The overarching clinical goal in the acute phase is to halt the cascade of secondary injury, decompress the neural parenchyma if indicated, and stabilize the vertebral column. A rigorous, standardized neurological examination is paramount, as the presence or absence of deep pain (conscious nociception) remains the single most powerful prognostic indicator in veterinary neurology.

Pathophysiology: Primary vs. Secondary Injury

Primary Injury: This is the immediate, mechanical damage to the neural tissue. It can be concussive (rapid transfer of kinetic energy, as in ANNPE), compressive (sustained mechanical pressure, as in IVDE), or lacerating. The primary injury is instantaneous and irreversible.

Secondary Injury: This is the complex, biochemical cascade triggered by the primary insult. It includes ischemia, ATP depletion, excitotoxicity (massive glutamate release), intracellular calcium influx, lipid peroxidation, and free radical generation. This cascade leads to delayed neuronal apoptosis and progressive tissue destruction. All acute medical management is aimed at blunting this secondary cascade.

Neurological Grading (Modified Frankel Scale)

Accurate grading dictates both the therapeutic approach and the prognostic discussion with the client:

  • Grade 1: Spinal hyperesthesia (pain) only. Normal gait and proprioception.
  • Grade 2: Ambulatory paraparesis/tetraparesis. Proprioceptive deficits are present, but the patient can bear weight and take purposeful steps.
  • Grade 3: Non-ambulatory paraparesis/tetraparesis. Voluntary motor function is present, but insufficient to bear weight.
  • Grade 4: Paraplegia/tetraplegia with intact deep pain. No voluntary motor function.
  • Grade 5: Paraplegia/tetraplegia with absent deep pain. The worst prognostic category.

Diagnostic Imaging

While plain orthogonal radiographs are useful for identifying gross fractures, luxations, or discospondylitis, they cannot reliably diagnose spinal cord compression or parenchymal damage. High-field MRI is the gold standard. MRI differentiates between surgical/compressive lesions (extruded nucleus pulposus) and non-surgical/concussive lesions (FCE, ANNPE), while also evaluating the cord for intramedullary T2W hyperintensity, which can be an early indicator of myelomalacia.

Evidence-Based Treatment Protocols

Medical Management: Indicated for Grades 1 and 2, or strictly non-compressive concussive injuries (FCE/ANNPE). The cornerstone is strict cage confinement for 4-6 weeks to allow the annulus fibrosus to scar. Analgesia should be multimodal (e.g., NSAIDs or Gabapentin, plus opioids). As noted, glucocorticoids are contraindicated.

Surgical Decompression: Indicated for compressive lesions in patients who are Grade 3, 4, or 5, or those failing medical management. Techniques include hemilaminectomy (thoracolumbar) and ventral slot (cervical). For Grade 5 dogs, time to surgery is critical; decompression ideally should occur within 12–24 hours of the loss of deep pain to maximize the chance of recovery.

Prognosis

For compressive IVDE treated surgically, dogs in Grades 1–4 have an excellent prognosis for return to ambulation (typically >85-90%). Once a patient progresses to Grade 5 (loss of deep pain), the surgical prognosis plummets to roughly 50%, even with rapid intervention. Clients must be warned about Progressive Myelomalacia (PMM) in Grade 5 dogs, which results in respiratory paralysis (due to ascending involvement of the phrenic nerve) and necessitates euthanasia.

References & Clinical Citations

  • Olby, N. J., et al. (2020). Prognostic Factors in Canine Acute Intervertebral Disc Disease. Frontiers in Veterinary Science.
  • Jeffery, N. D., et al. (2016). The role of methylprednisolone in acute spinal cord injury in dogs. Journal of Veterinary Internal Medicine.
  • Granger, N., et al. (2020). Canine Intervertebral Disc Disease: The Current State of Knowledge. Veterinary Clinics of North America: Small Animal Practice.
  • Castel, A., et al. (2017). Clinical characteristics of dogs with progressive myelomalacia following acute intervertebral disc extrusion. Journal of Veterinary Internal Medicine.
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BoneVet Orthopaedics Logo Veterinary Orthopaedic & Neurosurgical Service

Acute Spinal Cord Injury (SCI)

Initial Management, Pathophysiology, and Evidence-Based Guidelines

Acute spinal cord injury (SCI) is one of the most common and devastating neurologic emergencies seen in veterinary practice. The overarching clinical goal in the acute phase is to halt the cascade of secondary injury, decompress the neural parenchyma if indicated, and stabilize the vertebral column.

Because these patients are remarkably fragile, early decisions regarding handling, analgesia, and imaging profoundly impact the ultimate prognosis. This guide outlines the standard of care for the initial assessment and management of acute SCI prior to surgical referral.

1. Primary Assessment & Immobilization

Stabilize the patient (airway, breathing, circulation) as for any other emergency. Early consideration must be given to systemic blood pressure and oxygenation. Hypotension will result in a further decrease in the already compromised perfusion of the injured spinal cord, while hypoxemia exacerbates local energy failure. Oxygen supplementation is particularly important for animals with cervical SCI, where hypoventilation is common.

Feline Considerations: FIV and FeLV testing should be performed in feline patients, as a positive result markedly increases the likelihood of lymphoma as the cause of neurological deficits.

Immobilization: Immediate cage confinement is the minimum requirement for suspected Hansen Type I disc extrusions. If vertebral fracture or subluxation is suspected, strapping the patient to a rigid board is strictly recommended to prevent catastrophic secondary injury during handling.

2. Neurological Grading & True Deep Pain Assessment

The single most powerful prognostic indicator in veterinary neurology is the presence or absence of deep pain (conscious nociception). It is absolutely vital to evaluate deep pain before administering potent opioid analgesics, as a patient with weak sensation may appear to have completely lost perception under the influence of opioids.

Testing Deep Pain: A Progressive Approach

Limb retraction (a withdrawal reflex) is not an indication of pain sensation. Look for a conscious response: vocalizing, turning to look, attempting to bite, or sudden pupillary dilation. Stimulus must be applied to the medial and lateral digits (and tail) in a progressively escalating manner:

  1. Strong finger pressure.
  2. Light pressure with small haemostats.
  3. Heavy pressure with large haemostats (sufficient to compress the periosteum).
  4. If no response is elicited, the careful use of pliers across the calcaneus may be considered. While this may sound brutal, confirmed absence of deep pain dictates prognosis and often the owner's decision regarding euthanasia. It is vitally important to be sure.

3. The Pre-Referral Radiography Trap

Should you undertake radiographic investigation before considering referral? Generally, no. Plain radiographs rarely yield sufficient information to plan appropriate surgical management, as advanced imaging (MRI/CT) is required to visualize parenchymal damage and extruded disc material.

More importantly, taking radiographs prior to referral poses a massive physical risk to the patient. When spinal cord injuries occur, paraspinal muscles spasm, creating a splinting effect that contributes substantially to the stability of the spinal column. Sedation or anesthesia results in the loss of this muscle "splinting." Unstable vertebral segments are more likely to displace, and increased movement at disc spaces may cause further extrusion. It is quite common for patients to show severe neurological deterioration following sedation for plain X-rays.

Clinical Warning: Radiographs of suspected atlantoaxial (AA) subluxations taken with a ventroflexed cervical spine are highly dangerous. This position markedly exacerbates cervical spinal cord compression and risks precipitating acute respiratory failure or cardiac arrest. A neutral position is sufficient.

4. Analgesia and the Glucocorticoid Consensus

Analgesia should be instigated immediately following the neurological exam. NSAIDs are useful (provided the patient is normotensive and well-hydrated), and pure mu-agonist opioids are appropriate for severe pain.

The Glucocorticoid Stance: Glucocorticoids are widely used in veterinary practice for the mismanagement of spinal cord trauma. They prejudice the survival of injured neurons by interfering with glucose metabolism.

  • Dexamethasone: Associated with a poorer prognosis and significantly increases the risk of severe GI ulceration. With the current body of knowledge, the use of dexamethasone in the management of spinal cord trauma is unwise and potentially negligent.
  • Methylprednisolone Sodium Succinate (MPSS): There are NO veterinary studies demonstrating benefits following the use of MPSS. Endoscopic studies have revealed severe, subclinical gastrointestinal hemorrhage in 90% of dogs following MPSS treatment. Routine glucocorticoid therapy in spinal patients is strongly discouraged.

5. Prognosis and Referral Timing

Acute onset non-ambulatory paraparesis or paraplegia should always be considered a potential surgical emergency. Owners must be warned that delays in referral can have catastrophic consequences, as partially extruded disc material may continue to herniate.

Disc Extrusion (IVDE)

  • Deep Pain Present: Excellent prognosis. 90-95% expected functional recovery following surgical decompression.
  • Deep Pain Absent: Guarded prognosis. 50-60% expected functional recovery (provided surgery occurs within 24-48 hours of loss of deep pain). Risk of Progressive Myelomalacia (PMM).

Spinal Fracture / Subluxation

  • Deep Pain Present: Very good prognosis. 80-90% expected functional recovery following surgical stabilization.
  • Deep Pain Absent: Extremely poor prognosis. Confirmed absence of deep pain in a fracture scenario essentially precludes any chance of functional recovery.