House-Brackmann Grading — Facial Nerve Function Scale

When John House and Derald Brackmann published their facial nerve grading system in 1985, the problem they were solving was not clinical — it was communicative. Two surgeons reporting outcomes from different centres might describe the same patient as “moderate” or “good” and mean entirely different things. The House-Brackmann scale imposed a shared vocabulary: six ordinal grades, each with defined criteria for forehead movement, eye closure, and mouth function, that allow outcomes to be reported, compared, and understood across institutions. The AAO-HNS subsequently adopted it as the universal standard. It remains the most widely used facial nerve grading system in the world despite known limitations — and knowing those limitations is as important as knowing the grades themselves.

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The Six Grades — at a Glance

Grade	Descriptor	Forehead	Eye closure	Mouth	At rest
I	Normal	Normal	Complete, effortless	Symmetric	Normal
II	Mild dysfunction	Moderate to good	Complete, minimal effort	Slight asymmetry	Normal symmetry
III	Moderate dysfunction	Slight to moderate	Complete, requires effort	Slightly weak at maximum effort	Normal symmetry
IV	Moderately severe dysfunction	None	Incomplete	Asymmetric at maximum effort	Normal symmetry
V	Severe dysfunction	None	Incomplete	Barely perceptible movement	Asymmetric
VI	Total paralysis	None	None	None	Asymmetric, no tone

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The Grades in Detail — What the Examination Shows

A structured facial nerve examination assesses three movements: forehead wrinkling (raise your eyebrows), eye closure (close your eyes as tightly as you can), and mouth movement (show your teeth; smile broadly). At rest, observe nasolabial fold symmetry, palpebral fissure height, and mouth corner position.

Grade I — Normal

Complete symmetry at rest and with all voluntary movements. Both sides of the face perform identically. Forehead wrinkles bilaterally, both eyes close fully and effortlessly, the smile is symmetric, the nasolabial folds are equal.

Grade II — Mild Dysfunction

The weakness is present but requires close inspection to detect — a casual observer may not notice it. At rest, the face looks symmetric. On movement: the forehead still produces moderate to good wrinkling (some asymmetry may be visible on close look), the eye closes completely but with slightly more effort than the normal side, and the mouth shows only a slight asymmetry on smiling. No clinically significant synkinesis (involuntary facial movement accompanying voluntary movement, caused by aberrant nerve regeneration during recovery).

Grade III — Moderate Dysfunction

The difference between the two sides is now obvious to any observer, but not disfiguring — the patient does not look grotesque, and the affected side still has meaningful movement. At rest, symmetry is maintained. On movement: the forehead has slight to moderate function (noticeably reduced but still produces some wrinkles), the eye closes completely but only with definite, effortful closure (the patient has to squeeze deliberately), and the mouth is slightly weak even with maximum effort. Synkinesis, contracture, or hemifacial spasm may be present but are not severe.

Grade III is the level from which many Bell’s palsy patients plateau before further recovery, and it is clinically acceptable — the eye closes, the face moves, the patient can communicate and protect the cornea.

Grade IV — Moderately Severe Dysfunction

This is the grade that changes management. Two features define it and distinguish it from Grade III:

1. No forehead movement — where Grade III still has slight to moderate forehead wrinkling, Grade IV has none. The forehead is flat on the affected side even with maximum effort.

2. Incomplete eye closure — where Grade III achieves full closure with effort, Grade IV cannot fully close. There is visible sclera remaining even with maximum voluntary effort. This is a corneal exposure emergency — the cornea is no longer being protected by blinking.

At rest, the face may still appear grossly symmetric (this is counterintuitive but reflects the contracture and synkinesis that can “hold up” the resting face in partial palsy). Mouth movement is asymmetric even at maximum effort. Synkinesis, contracture, and hemifacial spasm may be prominent.

The Grade IV eye is the most important clinical finding in facial grading. Incomplete closure means the corneal reflex is absent, the tear film is disrupted on the inferior cornea, and without active corneal protection, the patient risks exposure keratopathy, corneal ulceration, and permanent visual loss.

Grade V — Severe Dysfunction

Only barely perceptible motion remains — a slight flicker when the patient strains to move. Crucially, the resting face is now visibly asymmetric: the nasolabial fold is effaced, the palpebral fissure is widened, and the mouth corner droops. This resting asymmetry is what separates Grade V from Grade IV, where resting symmetry is still maintained.

No forehead movement. Eye closure is incomplete (as in Grade IV). Mouth movement is at most a slight twitch. Synkinesis is characteristically absent at Grade V — because synkinesis requires some motor regeneration to produce aberrant co-contraction, and Grade V represents near-total denervation where there is insufficient regeneration to generate it.

Grade VI — Total Paralysis

No movement whatsoever. No voluntary function in any region of the face. No resting tone on the affected side. The face hangs flaccidly. There is no suggestion of movement even with maximum effort. No synkinesis (same reasoning as Grade V).

Total paralysis does not exclude recovery — but it carries the worst prognosis, and absence of any movement at three months is associated with a significantly reduced chance of complete recovery.

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The Clinical Thresholds That Change Management

Most of the HB grades are descriptive — they document function without necessarily demanding a specific response. Two thresholds are different.

Grade III → Grade IV: the eye closure line. This is the most clinically consequential step on the scale. Grade III: eye closes completely (with effort) — cornea is protected. Grade IV: eye does not close completely — cornea is exposed. When a patient crosses from Grade III to Grade IV, corneal protection becomes immediate management priority:

• Preservative-free lubricating drops during the day (every 1–2 hours if needed)
• Lubricating ointment at night (the eye does not close during sleep)
• Tape the eyelid closed at night if ointment alone is insufficient
• Moisture chamber spectacles in dry environments
• Ophthalmology referral if any corneal staining is found

A patient with Grade IV palsy who is not receiving corneal protection is at risk of a sight-threatening complication.

Grade V → Grade VI: the “is there anything there?” line. Both grades represent severe palsy, but Grade VI (complete absence of any movement) carries distinct prognostic weight. In Bell’s palsy, failure to show any voluntary movement by three weeks is a marker of poorer prognosis. By three months without recovery, the prognosis for complete functional return is significantly reduced, and specialist neurotological review is warranted. Electrophysiology (electroneuronography, needle EMG) becomes relevant for prognostic assessment at this level.

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Limitations of the Scale

The House-Brackmann system is not without its critics, and understanding its weaknesses prevents over-reliance on a single number.

Subjectivity. The grades are assigned by clinical observation without standardised measurement tools. Studies of inter-rater reliability show only moderate agreement between experienced clinicians, particularly in the middle grades (III and IV). The same patient examined by two surgeons may receive different grades.

Coarse granularity in the middle. Grades III and IV each cover a wide clinical spectrum. A patient recovering from Grade VI palsy who reaches “slight movement with maximum effort” lands in Grade V for many months before reaching Grade IV — but within Grade V, the clinician cannot distinguish early from late recovery. Similarly, Grade III encompasses both a patient who has nearly fully recovered and one who has just crossed the line from Grade IV.

No regional scoring. The grade is a global score. A patient with complete forehead and eye recovery but persistent marginal mandibular weakness scores Grade III — the same as a patient with uniform moderate weakness across all regions. The Sunnybrook Facial Grading System (Ross et al., 1996) addresses this by grading each facial region separately and scoring synkinesis explicitly — providing greater sensitivity for tracking regional recovery.

Synkinesis is underweighted. A patient recovering from severe palsy who develops disfiguring synkinesis (involuntary eye closure when smiling; tearing on eating — “crocodile tears”) may grade as III or even II by HB criteria, yet report significant quality-of-life impairment. The HB scale notes synkinesis but does not capture its severity systematically.

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Key Numbers

Parameter	Value
Published	1985 — House JW, Brackmann DE
Number of grades	6 (I = normal, VI = complete paralysis)
Grade with incomplete eye closure	IV, V, VI
Last grade with some forehead movement	III
Last grade with normal resting symmetry	IV
Grade where resting asymmetry appears	V
Synkinesis typically absent	V and VI (insufficient motor regeneration)
Main alternative system	Sunnybrook Facial Grading System (1996)

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Clinical Pearls

• The key distinction between Grade III and Grade IV is twofold: Grade III has residual forehead movement and complete (though effortful) eye closure; Grade IV has no forehead movement and incomplete eye closure. Both features must be present to assign Grade IV.
• Grade IV = corneal exposure risk. Start eye protection immediately — do not wait for ophthalmological confirmation of corneal damage.
• Resting asymmetry begins at Grade V, not earlier. If the face looks obviously abnormal at rest, you are at Grade V or VI.
• Synkinesis is a sign of recovery, not deterioration. It appears as the nerve regenerates — a patient whose eye twitches when they smile is recovering from palsy, not developing a new problem. But uncontrolled synkinesis can itself be disabling.
• The HB grade is a communication tool, not a diagnosis. Document it at first presentation and at every follow-up visit so the trajectory is visible — a Grade IV improving to Grade III is meaningful progress that a single snapshot cannot show.
• For formal outcome reporting, pair the HB grade with the timepoint — “Grade IV at 2 weeks, Grade III at 6 weeks” conveys the clinical picture in a way a single number never can.