The ASIA Impairment Scale (AIS) classifies spinal cord injuries. A patient who has no motor or sensory function below the level of injury, but has preserved sacral function (voluntary anal contraction or perianal sensation), is classified as:

• A AIS A (Complete injury)
• B AIS C (Motor incomplete, most motor key muscles grade <3)
• C AIS B (Sensory incomplete) ✓
• D AIS D (Motor incomplete, most motor key muscles grade ≥3)

Explanation

AIS (American Spinal Injury Association Impairment Scale): Grade A — complete, no sensory or motor function in sacral segments S4–S5; Grade B — sensory incomplete — no motor but sensory preserved below NLI including S4–S5 (perianal sensation or deep anal pressure); Grade C — motor incomplete — motor preserved below NLI, >50% key muscles grade <3; Grade D — motor incomplete, >50% key muscles grade ≥3; Grade E — normal. Sacral sparing (voluntary anal contraction, perianal sensation, or toe flexor voluntary movement) is the KEY distinction between complete (AIS A) and incomplete injury — preserved sacral function indicates continuity of long tracts.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.