Grade I — Normal Facial Function
Both sides move equally; the reference point for every other grade.
- I: HB Grade (Normal function)
- 100%: Forehead movement (full symmetric wrinkling)
- 100%: Eye closure (complete, effortless)
- 100%: Mouth symmetry (no drift at rest)
What normal looks like
Baseline symmetry across forehead, eyes, and mouth at rest and motion.
Why baseline matters
Every grade above compares movement loss against this reference.
Grade II — Mild Dysfunction
Slight weakness noticeable up close; symmetry preserved at rest.
- II: HB Grade (Mild dysfunction)
- ~75%: Forehead movement (slightly reduced)
- ~95%: Eye closure (complete with effort)
- ~90%: Mouth symmetry (minor asymmetry on motion)
Subtle early signs
Close inspection reveals slight forehead and mouth weakness only.
Clinical exam cues
Synkinesis, if present, is minimal or absent at this stage.
Grade III–IV — Moderate Dysfunction
Obvious weakness and noticeable asymmetry, but not disfiguring.
- III–IV: HB Grade (Moderate dysfunction)
- ~35%: Forehead movement (slight to no movement)
- ~65%: Eye closure (incomplete closure)
- ~55%: Mouth symmetry (asymmetric with effort)
Incomplete eye closure
Lagophthalmos appears; protective blink reflex is compromised.
Functional impact
Noticeable but not disfiguring asymmetry; synkinesis may appear.
Grade V — Severe Dysfunction
Barely perceptible motion; asymmetry now visible even at rest.
- V: HB Grade (Severe dysfunction)
- ~10%: Forehead movement (barely perceptible)
- ~25%: Eye closure (largely incomplete)
- ~20%: Mouth symmetry (marked asymmetry at rest)
Rest asymmetry
Drooping is visible without any attempted facial movement.
Treatment urgency
Higher grades push earlier steroid and eye-care intervention.
Grade VI — Total Paralysis
No facial movement at all; grading guides prognosis and urgency.
- VI: HB Grade (Total paralysis)
- 0%: Forehead movement (no movement)
- 0%: Eye closure (no closure, exposure risk)
- 0%: Mouth symmetry (complete flaccidity)
Complete flaccid paralysis
No tone or movement on the affected side, any expression.
Prognosis and monitoring
Higher grade, longer duration — closer follow-up is warranted.
Early treatment matters more as House-Brackmann grade rises.