What is the House‑Brackmann grading system for facial nerve weakness?

House-Brackmann Facial Nerve Grading System

The House-Brackmann grading system is a six-point scale (Grade I-VI) that systematically quantifies facial nerve function, ranging from normal function to complete paralysis, based on assessment of forehead movement, eye closure, and mouth symmetry at rest and with motion. 1

The Six Grades

Grade I: Normal

• Normal facial function in all areas 1

Grade II: Mild Dysfunction

• Slight weakness noticeable only on close inspection 1
• At rest: Normal symmetry of forehead, ability to close eye with minimal effort and slight asymmetry, ability to move corners of mouth with maximal effort and slight asymmetry 1
• No synkinesis, contracture, or hemifacial spasm 1

Grade III: Moderate Dysfunction

• Obvious but not disfiguring difference between the two sides with no functional impairment 1
• At rest: Normal symmetry and tone 1
• Motion: Slight to no movement of forehead, ability to close eye with maximal effort and obvious asymmetry, ability to move corners of mouth with maximal effort and obvious asymmetry 1
• Noticeable but not severe synkinesis, contracture, and/or hemifacial spasm 1
• Important caveat: Patients with obvious but not disfiguring synkinesis, contracture, and/or hemifacial spasm are Grade III regardless of degree of motor activity 1

Grade IV: Moderately Severe Dysfunction

• Obvious weakness and/or disfiguring asymmetry 1
• At rest: Normal symmetry and tone 1
• Motion: No movement of forehead; inability to close eye completely with maximal effort 1
• Critical distinction: Patients with synkinesis, mass action, and/or hemifacial spasm severe enough to interfere with function are Grade IV regardless of motor activity 1

Grade V: Severe Dysfunction

• Only barely perceptible motion 1
• At rest: Possible asymmetry with droop of corner of mouth and decreased or absence of nasolabial fold 1
• Motion: No movement of forehead, incomplete closure of eye and only slight movement of lid with maximal effort, slight movement of corner of mouth 1
• Synkinesis, contracture, and hemifacial spasm usually absent 1

Grade VI: Total Paralysis

• Loss of tone; asymmetry; no motion 1
• No synkinesis, contracture, or hemifacial spasm 1

Clinical Application and Limitations

The House-Brackmann system was originally designed to quantify facial nerve functional recovery after surgery that puts the facial nerve at risk, and has been adapted for assessing recovery after trauma or Bell's palsy 1. However, it was not designed to assess initial facial nerve paresis or paralysis of Bell's palsy 1.

Reliability

• The system demonstrates 93% inter-observer reliability when used by trained observers 2
• Inter-rater reliability is relatively strong for global scores (kappa = 0.541) and increases markedly with clinical experience 3

Important Pitfalls

In patients with differential facial function across nerve branches, a single global House-Brackmann score is inadequate 4, 3. The global score:

• Most strongly correlates with nose/midface function (59%), followed by mouth (51%), eye (48%), and forehead (35%) 3
• Does not correlate with the worst regional score in 79% of patients with variable weakness 4
• Primarily reflects eye function when differential weakness is present 4

For patients with variable facial weakness, use regional assessment reported as F(w) E(x) N(y) M(z), where w, x, y, and z represent House-Brackmann grades for forehead, eye, nose, and mouth respectively 4, 3. This more fully communicates facial function and provides clinically relevant information for treatment planning 4, 3.