SCI Pathophysiology

OT Dude Academy’s Free NBCOT® Exam Prep Course Spinal Cord Injury (SCI) SCI Pathophysiology

SCIs commonly result from the sudden acute impact on the spine that fractures or dislocates vertebrae.1 2 3  Most spinal cord injuries do not result in the spinal cord completely being severed.4 

3 Mechanisms of SCI include:

Retrieved from https://www.researchgate.net/figure/Schematic-diagrams-of-the-three-spinal-cord-injury-SCI-mechanisms-The-spinal-column_fig3_287204200 License: Creative Commons Attribution-NonCommercial 4.0 International

The most common form of injury is impact plus compression, typically through burst fractures with bone fragments compressing the spinal cord. Impact with transient compression is seen commonly in hyperextension injuries. Distraction injuries occur with two adjacent vertebrae being pulled apart, causing a tear in the axial plane.2 5 6 

A classification system by Bunge et al. divides SCI into four groups based on gross findings and percentage of cases from 1993:

  1. Solid cord injury (10% of cases): a cord appears normal, however damage to the cord can be ascertained on histological examination.
  2. Contusion/cavity (49% of cases): no breach or disruption in the surface anatomy and no adhesions to the dura, but areas of hemorrhage and necrosis are identified in the cord parenchyma (tissue).
  3. Laceration/transection (21% of cases): disruption of the surface anatomy. Often caused by sharp fragments of bone. There is damage to the cord parenchyma.
  4. Massive compression (20% of cases): The cord is macerated or pulpified to a varying degree Often accompanied by severe vertebral body fractures.7 

Combat SCI due to blast injuries are often associated with higher severity scores, longer hospital stays, and poorer neurological recovery compared to civilian SCI.8 

Treatment

The most effective clinical treatment to limit SCI damage is early spinal decompression (less than 24 hours post-injury) of the spinal cord. Generally, the extent of the SCI will determine the severity and outcome.9 10 11 12 

SCI Terminology

  • Paraplegia: paralysis affects all or part of the trunk, legs, and pelvic organs.
  • Tetraplegia (Quadriplegia): arms, hands, trunk, legs and pelvic organs are all affected by your spinal cord injury.13 
  • Complete: neurological assessments show no spared motor or sensory function below the level of injury.14 
  • Incomplete: some motor or sensory function below the level of injury.
  • Zone of partial preservation (ZPP): all the segments below the level of injury that have some preserved sensory or motor function. ZPP helps providers to distinguish spontaneous from treatment-induced functional recovery and is essential for evaluating the therapeutic efficacy of treatments.11 
  • Spinal Shock: immediately follows a severe SCI due to a complete loss of motor and sensory function below the level of injury, loss of deep tendon reflexes, and absent sphincter reflex. A four-phase model is often used to characterize spinal shock. The initial phase (24 hours after injury) involves absent deep tendon and cutaneous reflexes below the level of injury. The second phase (1-3 days post-injury) is characterized by an initial return of cutaneous reflexes. The third phase (lasting up to 1 month after injury) is characterized by early hyperreflexia with the early return of deep tendon reflexes as a result of axon-synapse growth. The last phase (lasts 1-12 months after injury) is characterized by spasticity and hyperreflexia of cutaneous and deep tendon reflexes. Synapse growth continues.15 
  • Sacral Sparing: the presence of Sensory or Motor Function in the most Caudal Sacral Segments i.e. preservation of light touch or pinprick sensation at S4-5 Dermatome, Deep Anal Pressure (DAP), or Voluntary Anal Sphincter Contraction. Used to diagnose complete vs. incomplete.16 17 

Obsolete Scoring Systems

Currently in use: American Spinal Injury Association (ASIA) Scoring System

  • Frankel Grade (1969)18 
  • Bracken et al., Yale University School of Medicine’s 5 and 7-scale system19 
  • Lucas and Ducker, Maryland Institute for Emergency Medical Services (1970s)20 
  • Klose – University of Miami Neuro-spinal Index (UMNI) in the 1980s21 
  • Chehrazi – Yale Scale in 198122 
  1. Oyinbo CA. Secondary injury mechanisms in traumatic spinal cord injury: a nugget of this multiply cascade. Acta Neurobiol Exp. (2011) 71:281–99.[↩]
  2. Dumont RJ, Okonkwo DO, Verma S, Hurlbert RJ, Boulos PT, Ellegala DB, et al. Acute spinal cord injury, part I: pathophysiologic mechanisms. Clin Neuropharmacol. (2001) 24:254–64. doi: 10.1097/00002826-200109000-00002[↩][↩]
  3. Sekhon L, Fehlings M. Epidemiology, demographics, and pathophysiology of acute spinal cord injury. Spine. (2001) 26:S2–12. doi: 10.1097/00007632-200112151-00002[↩]
  4. Tator C, Fehlings M. Review of the secondary injury theory of acute spinal cord trauma with emphasis on vascular mechanisms. J Neurosurg. (1991) 75:15–26.[↩]
  5. Choo AM, Liu J, Liu Z, Dvorak M, Tetzlaff W, Oxland TR. Modeling spinal cord contusion, dislocation, and distraction: characterization of vertebral clamps, injury severities, and node of Ranvier deformations. J Neurosci Methods. (2009) 181:6–17. doi: 10.1016/j.jneumeth.2009.04.007[↩]
  6. Fehlings MG, Smith JS, Kopjar B, Arnold PM, Yoon ST, Vaccaro AR, et al. Perioperative and delayed complications associated with the surgical treatment of cervical spondylotic myelopathy based on 302 patients from the AOSpine North America Cervical Spondylotic Myelopathy Study. J Neurosurg Spine. (2012) 16:425–32. doi: 10.3171/2012.1.SPINE11467[↩]
  7. Norenberg, M. D., Smith, J., & Marcillo, A. (2004). The pathology of human spinal cord injury: defining the pro[↩]
  8. Blair JA, Patzkowski JC, Schoenfeld AJ, Cross Rivera JD, Grenier ES, Lehman RA, et al. Are spine injuries sustained in battle truly different? Spine J. (2012) 12:824–9. doi: 10.1016/j.spinee.2011.09.012[↩]
  9. Fehlings MG, Vaccaro A, Wilson JR, Singh A,W, Cadotte D, Harrop JS, et al. Early versus delayed decompression for traumatic cervical spinal cord injury: results of the Surgical Timing in Acute Spinal Cord Injury Study (STASCIS). PLoS ONE. (2012) 7:e32037. doi: 10.1371/journal.pone.0032037[↩]
  10. Wilson JR, Tetreault LA, Kwon BK, Arnold PM, Mroz TE, Shaffrey C, et al. Timing of decompression in patients with acute spinal cord injury: a systematic review. Global Spine J. (2017) 7(3 Suppl.):95S−115S. doi: 10.1177/2192568217701716[↩]
  11. Michael Fehlings AR, Boakye M, Rossignol S, Ditunno JF Jr, Anthony S. Burns Essentials of Spinal Cord Injury Basic Research to Clinical Practice. Denver, CO: Thieme Medical Publishers Inc. (2013).[↩][↩]
  12. Wilson JR, Hashimoto RE, Dettori JR, Fehlings MG. Spinal cord injury and quality of life: a systematic review of outcome measures. Evid Based Spine Care J. (2011) 2:37–44. doi: 10.1055/s-0030-1267085[↩]
  13. Mayo Clinic. (n.d.). Spinal cord injury. Retrieved from https://www.mayoclinic.org/diseases-conditions/spinal-cord-injury/symptoms-causes/syc-20377890[↩]
  14. Wilson JR, Cadotte DW, Fehlings MG. Clinical predictors of neurological outcome, functional status, and survival after traumatic spinal cord injury: a systematic review. J Neurosurg Spine. (2012) 17(1 Suppl.):11–26. doi: 10.3171/2012.4.AOSPINE1245[↩]
  15. Hachem, L. D., Ahuja, C. S., & Fehlings, M. G. (2017). Assessment and management of acute spinal cord injury: from point of injury to rehabilitation. The journal of spinal cord medicine, 40(6), 665-675.[↩]
  16. Shepard Center. (n.d.). ASIA/ISCoS Exam and Grade. Retrieved from https://www.spinalinjury101.org/details/asia-iscos[↩]
  17. Flint Rehab. (2021). Sacral Sparing After Spinal Cord Injury: Determining Your Chances of Recovery. Retrieved from https://www.flintrehab.com/sacral-sparing-spinal-cord-injury/[↩]
  18. Frankel HL, Hancock DO, Hyslop G, Melzak J, Michaelis LS, Ungar GH, et al. The value of postural reduction in the initial management of closed injuries of the spine with paraplegia and tetraplegia. Paraplegia I. (1969) 7:179–92. doi: 10.1038/sc.1969.30[↩]
  19. Bracken MB, Webb SB Jr, Wagner FC. Classification of the severity of acute spinal cord injury: implications for management. Paraplegia. (1978) 15:319–26. doi: 10.1038/sc.1977.48[↩]
  20. Lucas JT, Ducker TB. Motor classification of spinal cord injuries with mobility, morbidity and recovery indices. Am Surg. (1979) 45:151–8.[↩]
  21. Klose KJ, Green BA, Smith RS, Adkins RH, MacDonald AM. University of Miami Neuro-Spinal Index (UMNI): a quantitative method for determining spinal cord function. Paraplegia. (1980) 18:331–6.[↩]
  22. Chehrazi B, Wagner FC Jr, Collins WF Jr, Freeman DH, Jr. A scale for evaluation of spinal cord injury. J Neurosurg. (1981) 54:310–5. doi: 10.3171/jns.1981.54.3.0310[↩]
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