ASIA Impairment Scale
/ AY-zhuh; A-I-S /
After the ISNCSCI exam has mapped exactly what works, the team needs one short verdict that sums up how severe the injury is and how much function survives below it. The ASIA Impairment Scale (AIS) is that summary: a five-letter grade, A through E, that everyone in spinal cord injury care recognises instantly. It is the SCI equivalent of saying a burn is 'first degree' or 'third degree' — a quick shorthand for severity.
The grades run from worst to best. AIS A is a complete injury: no motor or sensory function is preserved in the lowest sacral segments (S4–S5) — meaning no anal sensation and no voluntary sphincter squeeze. AIS B is sensory incomplete: some sensation survives below the level, including at S4–S5, but no useful muscle movement does. AIS C is motor incomplete: voluntary movement is preserved below the level, but more than half of the key muscles below are weaker than grade 3 (cannot lift against gravity). AIS D is also motor incomplete but stronger: at least half of those key muscles are grade 3 or better. AIS E means a person who had a documented SCI now tests entirely normal on the exam. The dividing line between A/B and C/D/E is whether voluntary movement survives at the very bottom of the cord — sacral sparing.
In rehabilitation the AIS grade is a powerful, honest predictor and a planning tool. Roughly speaking, AIS A injuries recover little additional movement, while incomplete grades (C and especially D) often regain meaningful function, with many AIS D patients eventually walking. It is not a destiny — people improve and occasionally convert to a better grade over months — but it lets the team set realistic goals from day one and choose where to invest therapy. Its honesty cuts both ways: it tempers false hope and false despair alike.
Two people with the same C6 level differ completely on the AIS: one is grade A with no sacral sparing and uses a wheelchair, while the other is grade D with strong legs below the level and walks with a cane. The level is the same, but the grade decides the future.
Two SCIs at the same level can have very different futures — the AIS grade, not just the level, predicts function.
A frequent error is reading 'incomplete' (AIS B/C/D) as 'mild'. An AIS B injury is incomplete yet still severe — sensation survives but no useful movement. The crucial dividing line is sacral sparing, not how much function feels preserved overall.