A 25-year-old man dives into a shallow pool and sustains a hyperflexion cervical injury at C5–C6. He is quadriplegic below C5 but has preserved sacral sensation (perianal sensation intact) and voluntary anal contraction. The ASIA Impairment Scale classification is:

• A ASIA B — sensory incomplete: sensory but not motor function preserved below injury including S4–S5 ✓
• B ASIA A — complete injury, no motor or sensory function preserved below injury level
• C ASIA C — motor incomplete: motor function preserved below injury, more than half of key muscles have grade <3
• D ASIA D — motor incomplete: motor function preserved below injury, at least half of key muscles grade ≥3

Explanation

ASIA Impairment Scale: A (complete — no motor/sensory below injury including S4–S5); B (sensory incomplete — some sensory preserved below injury level including S4–S5 sacral segments, but NO motor function below injury); C (motor incomplete — motor preserved, but majority key muscle grades below level are <3); D (motor incomplete — motor preserved, majority key muscle grades ≥3); E (normal). The key to ASIA B is preserved sacral sensation (perianal) +/- voluntary anal contraction, indicating incomplete injury and sacral sparing, but NO useful motor function below C5. Sacral sparing is the critical prognostic marker distinguishing complete from incomplete cord injury.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.