What is the House-Brackmann grading system used for in assessing facial paralysis?

House-Brackmann Grading System

The House-Brackmann grading system is a six-point scale used to systematically quantify facial nerve function, primarily designed to assess recovery after surgeries that put the facial nerve at risk, though it is now widely applied to Bell's palsy, facial trauma, and other causes of facial paralysis. 1, 2

Purpose and Clinical Application

• The scale was originally developed to measure facial nerve functional recovery after surgical procedures involving facial nerve risk, but has been expanded to assess recovery after trauma and Bell's palsy. 1, 2

• It was not originally designed to assess initial facial nerve paresis or paralysis in Bell's palsy, though it is commonly used for this purpose in clinical practice. 1, 2

• The system helps determine appropriate interventions based on severity of dysfunction and is used to evaluate candidates for facial nerve decompression surgery. 2

The Six-Grade Classification System

Grade I: Normal

• Normal facial function in all areas with complete symmetry. 1, 2

Grade II: Mild Dysfunction

• Slight weakness noticeable only on close inspection. 1, 2
• 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, 2
• 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
• 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, 2
• At rest: normal symmetry and tone. 1
• Motion: no movement of forehead and inability to close eye completely with maximal effort. 1
• 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, 2
• 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 with 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

• Complete loss of tone, asymmetry, no motion, and no synkinesis, contracture, or hemifacial spasm. 1, 2

Clinical Performance and Reliability

• The House-Brackmann system demonstrates good inter-observer reliability with 93% agreement among independent observers, though disagreements can occur by a maximum of one grade. 3

• The system shows moderate correlation with newer grading systems like the Facial Nerve Grading System 2.0, with an intraclass correlation coefficient of 0.908. 4

• The critical distinction between Grades III and IV hinges on whether synkinesis or spasm interferes with function and whether complete eye closure is possible, which has important implications for eye protection and quality of life. 1

Important Clinical Caveats

• The system is subjective and qualitative, which can lead to variability in grading, particularly in distinguishing between adjacent grades. 5, 6

• Eye closure ability is the most critical functional assessment, as inability to close the eye completely (Grade IV or worse) significantly increases risk of corneal exposure and requires aggressive eye protection measures. 1

• The presence and severity of synkinesis, contracture, or hemifacial spasm can override motor function assessment in determining the grade, particularly for Grades III and IV. 1