Residency · Residency · Physical Medicine Rehabilitation
ASIA/ISNCSCI Examination and SCI Classification
Overview
International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI). Published by the American Spinal Injury Association (ASIA). Gold standard for classifying spinal cord injury severity and level. Essential for prognosis, communication, and research. Should be performed serially: at admission, at discharge, and at follow-up visits.
The ISNCSCI Examination
Sensory Examination
Two modalities tested: light touch and pin prick. 28 dermatomes tested bilaterally (C2-S4-5). Each dermatome scored 0 (absent), 1 (altered/impaired), 2 (normal), NT (not testable). Key sensory points (one per dermatome): C2: occipital protuberance. C3: supraclavicular fossa. C4: top of acromioclavicular joint. C5: lateral antecubital fossa.
C6: thumb (dorsal surface, proximal phalanx). C7: middle finger (dorsal surface, proximal phalanx). C8: little finger (dorsal surface, proximal phalanx). T1: medial antecubital fossa. T2: apex of axilla. T3: third intercostal space. T4: nipple line. T6: xiphoid process. T8: midway between T6 and T10. T10: umbilicus. T12: inguinal ligament midpoint. L1: midway between T12 and L2.
L2: mid-anterior thigh. L3: medial femoral condyle. L4: medial malleolus. L5: dorsum of foot at third metatarsophalangeal joint. S1: lateral heel. S2: popliteal fossa. S3: ischial tuberosity. S4-5: perianal area.
Deep anal pressure (DAP): present or absent. Maximum score: 112 per modality per side (total 224 each for light touch and pin prick).
<image>ASIA dermatome map showing 28 key sensory points for ISNCSCI examination</image>
Motor Examination
10 key muscle groups tested bilaterally (5 upper, 5 lower). Upper extremity key muscles: C5: elbow flexors (biceps, brachialis). C6: wrist extensors (extensor carpi radialis longus and brevis).
C7: elbow extensors (triceps). C8: finger flexors (FDP to middle finger). T1: small finger abductors (abductor digiti minimi). Lower extremity key muscles: L2: hip flexors (iliopsoas). L3: knee extensors (quadriceps). L4: ankle dorsiflexors (tibialis anterior). L5: long toe extensors (extensor hallucis longus).
S1: ankle plantarflexors (gastrocnemius/soleus). Grading scale: 0-5 (standard MRC scale). 0: total paralysis. 1: palpable or visible contraction.
2: full ROM gravity eliminated. 3: full ROM against gravity. 4: active movement against some resistance. 5: normal strength.
5*: normal but prior weakness (examiner judgment). NT: not testable. Voluntary anal contraction (VAC): present or absent. Maximum motor score: 50 per side (100 total).
Anorectal Examination
Critical component - determines completeness of injury. Deep anal pressure (DAP): sensory component. Voluntary anal contraction (VAC): motor component. Either DAP or VAC present = sacral sparing = incomplete injury.
Determining Neurological Levels
Sensory Level
Most caudal dermatome with normal (grade 2) sensation for both light touch AND pin prick. Determined separately for right and left sides.
Motor Level
Most caudal key muscle with grade 3 or better strength, provided all muscles above are grade 5. In segments without testable myotomes (C1-C4, T2-L1, S2-S4-5), motor level = sensory level if sensory is normal.
Neurological Level of Injury (NLI)
Most cephalad of the four levels (right sensory, left sensory, right motor, left motor). Single level that represents the most rostral segment with abnormal function.
Single Neurological Level
When right and left levels are the same = single NLI. When different = reported separately.
<image>ASIA ISNCSCI worksheet showing motor and sensory scoring grid with level determination</image>
AIS (ASIA Impairment Scale) Classification
AIS A - Complete
No sensory or motor function preserved in sacral segments S4-5. No DAP, no VAC, no light touch or pin prick at S4-5.
AIS B - Sensory Incomplete
Sensory but NOT motor function preserved below NLI AND includes sacral segments S4-5. DAP or sensation at S4-5 present, but NO VAC and no motor function >3 levels below motor level.
AIS C - Motor Incomplete
Motor function preserved below NLI AND sacral sparing (VAC or motor function in S4-5). More than half of key muscles below NLI have grade < 3.
AIS D - Motor Incomplete
Motor function preserved below NLI AND sacral sparing. At least half of key muscles below NLI have grade >= 3.
AIS E - Normal
Sensory and motor function normal in all segments. Patient had prior deficits (otherwise not classified as SCI).
| AIS Grade | Classification | Criteria | Conversion Rate |
|---|---|---|---|
| A | Complete | No sensory or motor function at S4-5 | ~10-15% convert to incomplete |
| B | Sensory incomplete | Sensory preserved at S4-5, no motor below NLI | ~30-40% improve to C or D |
| C | Motor incomplete | Motor below NLI, >50% key muscles <3 | ~60-70% improve to D |
| D | Motor incomplete | Motor below NLI, ≥50% key muscles ≥3 | Good functional prognosis |
| E | Normal | Normal sensory and motor in all segments | Prior deficit resolved |
Zone of Partial Preservation (ZPP)
Only applies to AIS A (complete injuries). Most caudal dermatome/myotome with some preserved function. Reported separately for sensory and motor, right and left. Has prognostic significance for potential recovery.
Common Errors in ISNCSCI Classification
Forgetting the anorectal examination (most critical error). Testing incorrect key sensory points. Not testing pin prick AND light touch separately. Confusing motor level with NLI.
Assigning ZPP in incomplete injuries (only for AIS A). Not accounting for non-SCI conditions (peripheral nerve injury, pre-existing conditions). Testing strength with improper positioning (gravity-eliminated vs. against gravity). Confusing "not testable" with "absent".
<image>Flowchart for ASIA Impairment Scale classification decision-making algorithm</image>
Clinical Significance of Accurate Classification
Prognostication: AIS grade at 72 hours predicts long-term outcomes. AIS A: ~10-15% convert to incomplete (usually AIS B). AIS B: ~30-40% improve to AIS C or D. AIS C: ~60-70% improve to AIS D.
AIS D: majority achieve community ambulation. Research stratification: essential for clinical trial enrollment. Communication: standardized language across providers and institutions. Rehabilitation planning: functional expectations based on level and completeness.
Functional Expectations by Level
C4: dependent in ADLs, power wheelchair with head/chin control, ventilator dependent or diaphragmatic pacing. C5: may assist with feeding using adaptive equipment, power wheelchair with hand control. C6: modified independent feeding, some dressing, tenodesis grasp, manual wheelchair with rim modifications possible. C7: independent self-care, manual wheelchair independent, modified independent transfers.
C8-T1: independent ADLs, independent manual wheelchair, independent transfers. T6-T12: independent ADLs and wheelchair mobility, potential for limited ambulation with KAFOs (high energy cost). L1-L3: community ambulation with KAFOs or AFOs. L4-S1: community ambulation with AFOs or no device.
Clinical Pearls
The anorectal exam (DAP and VAC) is the single most important component for determining completeness - never skip it. A patient can have AIS A classification with preserved motor or sensory function below the NLI, as long as S4-5 is not spared. Serial ISNCSCI exams are essential - early classification may change significantly in the first 72 hours to weeks. "Sacral sparing" (any S4-5 function OR DAP OR VAC) is the defining feature that separates complete from incomplete injuries. The ZPP has prognostic value: preserved function in the ZPP segments predicts greater likelihood of recovery in those segments.
<image>Functional outcomes expected by spinal cord injury level from C4 through L5</image>
References
- Kirshblum SC, et al. International Standards for Neurological Classification of Spinal Cord Injury (Revised 2019). J Spinal Cord Med. 2021;44(1):1-11.
- Burns S, et al. International Standards for Neurological Classification of Spinal Cord Injury, Revised 2011. Top Spinal Cord Inj Rehabil. 2012;18(1):85-99.
- Kirshblum S, et al. Reference for the 2019 revision of the ISNCSCI. Spinal Cord. 2019;57(10):815-818.
- Marino RJ, et al. Reliability and repeatability of the motor and sensory examination of ISNCSCI. J Spinal Cord Med. 2008;31(2):166-170.
- Cifu DX, et al. Braddom's Physical Medicine and Rehabilitation. 6th ed. Elsevier; 2020.
