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PubMed This is a summary of 13 peer-reviewed journal articles Updated
Neurology

Classifying Your Injury: Understanding Levels and Grades

At a Glance

A spinal cord injury is classified using the ASIA Impairment Scale (AIS), grading the injury from A (complete) to E (normal). The Neurological Level of Injury identifies the lowest point on the spinal cord where sensation and muscle strength remain normal.

In the first few days after a spinal cord injury, your medical team will perform a detailed physical exam to “map” your injury. This exam, known as the ISNCSCI (International Standards for Neurological Classification of Spinal Cord Injury), uses a framework called the ASIA Impairment Scale (AIS) to describe exactly how the injury has affected your body [1][2].

Understanding these results is key to setting goals and tracking your progress.

Determining Your Level of Injury

The Neurological Level of Injury (NLI) is the lowest point on your spinal cord where you still have normal sensation and muscle strength [3]. Your doctors test 28 sensory points and 10 key muscle groups on each side of your body [1].

  • Tetraplegia (formerly Quadriplegia): This occurs when the injury is in the cervical (neck) area (levels C1 to C8). It affects the arms, hands, trunk, and legs [4][5].
  • Paraplegia: This occurs when the injury is in the thoracic (chest), lumbar (lower back), or sacral areas. It affects the trunk and legs, but the arms and hands remain fully functional [6][7].

The ASIA Impairment Scale (AIS)

The AIS grades your injury from A to E based on how much “signal” is getting through the site of the injury [1].

Grade Classification What it Means
AIS A Complete No sensory or motor function is found in the lowest sacral segments (S4-S5) [1].
AIS B Sensory Incomplete You have feeling (sensation) in the lowest sacral segments, but no muscle control below the injury level [1].
AIS C Motor Incomplete There is muscle movement below the injury level, but more than half of those muscles are not strong enough to lift against gravity [1].
AIS D Motor Incomplete At least half of the key muscles below the injury level are strong enough to lift against gravity [1].
AIS E Normal Sensory and motor functions have returned to normal [1].

Why “Sacral Sparing” is Significant

You may hear your doctors talk about sacral sparing. This refers to any sensation or muscle control at the very end of the spinal cord (segments S4-S5) [8].

  • The Hallmark of Incompleteness: If you have sacral sparing, your injury is classified as “incomplete” (AIS B, C, or D) [9].
  • A Positive Sign: Sacral sparing indicates that some nerve fibers are still connected between your brain and the lowest part of your spinal cord [8]. This is often a robust predictor that you may regain more function over time [10].

The Zone of Partial Preservation (ZPP)

Even if an injury is classified as “complete” (AIS A)—and in some cases of incomplete injuries (per 2019 ISNCSCI revisions)—there is often a Zone of Partial Preservation (ZPP) [11]. This is an area immediately below your Neurological Level of Injury where some nerves are still partially working, even if they aren’t fully functional yet [12]. Tracking the ZPP helps your team identify which muscles or areas of skin might be the most likely to improve during rehabilitation [13].

Common questions in this guide

What is the ASIA Impairment Scale (AIS)?
The ASIA Impairment Scale is a grading system doctors use to describe the severity of a spinal cord injury. It ranges from Grade A, meaning no movement or feeling below the injury, to Grade E, meaning normal sensory and motor function.
What is the difference between tetraplegia and paraplegia?
Tetraplegia, formerly called quadriplegia, occurs from an injury in the neck area and affects the arms, hands, trunk, and legs. Paraplegia involves damage lower in the back and affects the trunk and legs, but the arms and hands still work normally.
What does sacral sparing mean?
Sacral sparing means you have some feeling or muscle control at the very end of your spinal cord. This is a positive sign that nerve fibers are still connected to the brain, which often means you may regain more function over time.
What is a complete versus incomplete spinal cord injury?
A complete injury (AIS A) means there is no sensory or motor function at the lowest part of the spinal cord. An incomplete injury means some feeling or movement remains below the level of the injury, allowing signals to pass through.
What is the Zone of Partial Preservation (ZPP)?
The Zone of Partial Preservation is an area just below your primary injury level where some nerves still work partially, even if they aren't fully functional yet. Tracking this zone helps doctors identify which muscles might improve during rehabilitation.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my specific Neurological Level of Injury (NLI), and how does that relate to the movement I currently have?
  2. 2.Am I classified as AIS A, B, C, or D, and what does that mean for my long-term goals?
  3. 3.Did my exam show 'sacral sparing'? If not now, how often will we re-test for it?
  4. 4.If I have a 'complete' injury, do I have a 'Zone of Partial Preservation' (ZPP)? How many levels does it extend below my injury?
  5. 5.How might my classification change as my spinal cord's initial swelling goes down?

Questions For You

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References

References (13)
  1. 1

    International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019.

    Rupp R, Biering-Sørensen F, Burns SP, et al.

    Topics in spinal cord injury rehabilitation 2021; (27(2)):1-22 doi:10.46292/sci2702-1.

    PMID: 34108832
  2. 2

    Updates of the International Standards for Neurologic Classification of Spinal Cord Injury: 2015 and 2019.

    Kirshblum S, Snider B, Rupp R, et al.

    Physical medicine and rehabilitation clinics of North America 2020; (31(3)):319-330 doi:10.1016/j.pmr.2020.03.005.

    PMID: 32624097
  3. 3

    Spinal cord injury: A multisystem physiological impairment/dysfunction.

    Perrouin-Verbe B, Lefevre C, Kieny P, et al.

    Revue neurologique 2021; (177(5)):594-605 doi:10.1016/j.neurol.2021.02.385.

    PMID: 33931244
  4. 4

    Pediatric Traumatic Cervical Distraction Injury: A Case Report.

    Watanabe S, Nakanishi K, Uchino K, et al.

    Cureus 2024; (16(6)):e62910 doi:10.7759/cureus.62910.

    PMID: 39040785
  5. 5

    Non-invasive spinal cord electrical stimulation for arm and hand function in chronic tetraplegia: a safety and efficacy trial.

    Moritz C, Field-Fote EC, Tefertiller C, et al.

    Nature medicine 2024; (30(5)):1276-1283 doi:10.1038/s41591-024-02940-9.

    PMID: 38769431
  6. 6

    Prevalence of Spasticity and Below-Level Neuropathic Pain Related to Spinal Cord Injury Level and Damage to the Lower Spinal Segments.

    Skoog B, Jakobsson KE

    Journal of rehabilitation medicine. Clinical communications 2020; (3()):1000039 doi:10.2340/20030711-1000039.

    PMID: 33884141
  7. 7

    Assessment of hindlimb motor recovery after severe thoracic spinal cord injury in rats: classification of CatWalk XT® gait analysis parameters.

    Zheng G, Zhang H, Tail M, et al.

    Neural regeneration research 2023; (18(5)):1084-1089 doi:10.4103/1673-5374.355763.

    PMID: 36254997
  8. 8

    Characterizing Natural Recovery after Traumatic Spinal Cord Injury.

    Kirshblum S, Snider B, Eren F, Guest J

    Journal of neurotrauma 2021; (38(9)):1267-1284 doi:10.1089/neu.2020.7473.

    PMID: 33339474
  9. 9

    A Comparison of Diagnostic Stability of the ASIA Impairment Scale Versus Frankel Classification Systems for Traumatic Spinal Cord Injury.

    Kirshblum S, Botticello A, Benedetto J, et al.

    Archives of physical medicine and rehabilitation 2020; (101(9)):1556-1562 doi:10.1016/j.apmr.2020.05.016.

    PMID: 32531222
  10. 10

    Patterns of Sacral Sparing Components on Neurologic Recovery in Newly Injured Persons With Traumatic Spinal Cord Injury.

    Kirshblum SC, Botticello AL, Dyson-Hudson TA, et al.

    Archives of physical medicine and rehabilitation 2016; (97(10)):1647-55.

    PMID: 26971670
  11. 11

    International standards for neurological classification of spinal cord injury: impact of the revised worksheet (revision 02/13) on classification performance.

    Schuld C, Franz S, Brüggemann K, et al.

    The journal of spinal cord medicine 2016; (39(5)):504-12 doi:10.1080/10790268.2016.1180831.

    PMID: 27301061
  12. 12

    The 2019 revision of the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI)-What's new?

    Spinal cord 2019; (57(10)):815-817 doi:10.1038/s41393-019-0350-9.

    PMID: 31530900
  13. 13

    The Role of Motor Zones of Partial Preservation in Conversion From Initially Complete to Motor Incomplete Spinal Cord Injury.

    Kirshblum S, Snider B, Botticello A, et al.

    Archives of physical medicine and rehabilitation 2025; (106(7)):1053-1063 doi:10.1016/j.apmr.2025.01.473.

    PMID: 39947273

This page explains spinal cord injury classification for educational purposes. Your neurologist or rehabilitation specialist is the best source for interpreting your specific ASIA Impairment Scale grade and prognosis.

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