Recent advances onGrading Facial Nerve Function
• Development of a uniform and accurate method for grading facial nerve function is a prerequisite for effective diagnosis and treatment of patients with facial nerve paralysis.• Facial nerve anatomy is complex, and its unique physiology poses special challenges in grading facial nerve function following injury. Seminars in plastic surgery 2004:18;1-21
An ideal grading system would be a well- calibrated instrument that is convenient to use.• universality and reproducibility with low interobserver variability;• Incorporation of measures of both static and dynamic components of facial muscle function;• Regional scoring;
• acknowledgement of the secondary defects of facial nerve dysfunction;• subjective scoring by the patient; and• convenience and ability to be performed at low cost and in a minimal amount of time. Otol Neurotol 2006:27;1030-1036.
• However, a system that has sufficient rigor for research purposes may prove impractical in the clinic because it is difficult to learn, time consuming, or requires specialized equipment.• Furthermore, a system that is designed to classify patients into groups based on overall level of disability may not be optimized for tracking the evolution of paralysis in a given patient.
• Facial nerve dysfunction is often considered in two categories. Loss of motor function in the muscles of facial expression Secondary defects (synkinesis, hemifacial spasm, contracture, crocodile tears, and hyperacusis).
Methods of grading facial nerve function Traditional approaches (no specialized computer equipment, use of subjective assessments by the observer) Computer-based approaches(specialized equipment to measure and quantify digital data objectively).
TRADITIONAL APPROACHES• House classified facial nerve scales as Gross, Regional, Specific/ objective
• Gross scales make an overall assessment of facial motor function.• Gross scales of facial function evaluate overall facial function and assign a grade that reflects the severity of all paralysis and secondary effects simultaneously.• These gross scales are descriptive rather than integral in nature, and as a result they cannot be manipulated mathematically.
• Eg:• Botman and Jongkees Scale(1955)• May Scale(1970)• Pietersen Scale• House-Brackmann Scale (1985) universal standard of the American Academy of Otolaryngology– Head and Neck Surgery on recommendation of the Facial Nerve Disorders Committee, sought to group together patients with similar degrees of disability.
• Drawbacks :• Cannot be used to distinguish finer differences in facial nerve dysfunction.• Fails to distinguish subtle differences in facial nerve recovery.• lack of strong interobserver reliability
• Prone to observer error• Considerably less agreement within the intermediate degrees of impairment• Ambiguity regarding secondary defects of facial nerve dysfunction
• Regional scales, ascribe independent scores to different areas of facial function, sometimes with weighting to reflect the greater or lesser importance of given areas of the face, such as eye closure or mouth movement.• Eg: Smith Scale Adour and Swanson Scale Facial Paralysis Recovery Profile (FPRP) The Yanagihara Grading System for Facial Palsy
Detailed Evaluation of Facial Symmetry (DEFS), AbridgedJanssen‟s ScaleSunnybrook facial grading system (Toronto)
• Drawback• Although incorporation of synkinesis into the composite score occurs in a clear and unambiguous manner, there is no mention of the other secondary defects.• Also, because it remains a subjective scale, the facial grading system is prone to the same interobserver variability as the HBGS.
• Specific scales ask the observer to respond „„yes‟‟ or „„no‟‟ to questions about specific areas of the face.• Eg: Stennert scale(Facial Paralysis Score of Stennert, Secondary Defect Facial Paralysis Score of Stennert) The Burres-Fisch system(1986) Nottingham system(1994)
• Burres-Fisch system (1986)• A scale relying solely on objective measurements has the benefit of eliminating observer bias and subjectivity; one such grading system is the Burres- Fisch system .• Based on a study of facial biomechanics of seven standard facial expressions in subjects with normal facial nerve function , this system quantifies facial nerve function with a defined linear measurement index.
• The linear measurement index (LMI) is calculated by a series of equations using the percent displacement of various facial anatomic landmarks during movement compared with repose.• An advantage of the Burres-Fisch system over the HBGS is that the linear measurement index represents a continuous graded scale, thereby allowing finer distinctions of function.
• A study comparing the Burres-Fisch method with the HBGS indicated a high degree of correlation between the two systems when they were used to evaluate patients with facial weakness, despite the fact that one scale is subjective and the other objective.
• Drawback• The calculation of the linear measurement index is an arduous, time-consuming process (taking approximately 20 minutes) and is unlikely to represent a practical tool for the busy clinician.• Also, no measures for secondary defects are incorporated.• Inability to make simultaneous recordings in different facial regions Seminars in plastic surgery 2004:18;1-21
• Drawback• Inability to assess bilateral facial nerve dysfunction. Because the composite number is expressed as a ratio to the contralateral side, bilateral facial nerve palsy, even if severe, would result in a high Nottingham score and therefore would not reflect the true status of either nerve.• In addition, the lettering system used to assess secondary defects does not contribute to the overall numerical score, and it is therefore useful as a descriptive modifier only.
scale Psychometric Clinical utility properties established Interobserver Reliability, widely used considered HBFNGS Repeatability universal standard Content validity,construct Good reviews widely used SFNGS validity , intrarater and inter- rater reliability ,agreement of score with HBFNGS and yanagihara scale , Repeatability Reliability compared to LMINOTTINGAMS _ SYSTEM Agreement of score with Widely used in japanYanagihara HBFNGS and SFNGS, scales
Studies uptil 2005 conclude……………• HBFNGS is prone to high interobserver variability due to its subjective nature. Clin Otolaryngol 1992;17:303–307• Reliability of Nottingams system is reported to be better than the Burres Fisch LMI with a variance of 7% versus 26%. Otol Neurotol 2003:24;118–122.• Sunnybrook FNGS composite score is reported to be more sensitive than the HBFNGS in detecting changes in facial nerve recovery and to have good interobserver reliability.
• The Sunnybrook system scores at the same agreement level as the House-Brackmann and Yanagihara grading systems.• Substantial agreement is found between the regional Sunnybrook and Yanagihara scales.• There is an evaluative difference between the weighted regional Sunnybrook and the gross House Brackmann systems. Sunnybrook grading is easy and quick.
• By adding objective measurements and additional secondary defects, the Sunnybrook system can be an alternative to the other predominating grading systems. Otol Neurotol 2004:25;1020–1026.• Agreement between the LMI and the HBFNGS is excellent (less than 10% difference) in only 50% of patients and satisfactory (between 10 and 25%) in 33% of patients . Otol Neurotol 2003:24;118–122.• Although many of the other grading scales have their advantages, none have duplicated the global appeal and ease of use of the HBFNGS.
Search strategies:• Databases searched: – Pubmed , Free medical journals, Google Scholar , Sage Pub , Ovid sp.• Selection Criteria: – Full text articles & abstract from yr 2006 to 2010. • Keywords used were: Facial nerve grading systems.
Studies on facial grading systems developed beyond 2005
Grading Facial Nerve Function: Why a New Grading System, the MoReSS, Should Be Proposed.(4) Alexander J, Weibel W B, Peter P G, Benthem B, Wim B B, Gerrit J H. Otol Neurotol 2006:27;1030-1036
• In this way, a total score of Mo 12, Re 8, S 6, and S 10 can be obtained• An extra letter (a-d) can be assigned for the paralytic region• Mo6ab, Re 4ab if the forehead and eye have gross asymmetry at rest, the eye cannot be closed, and there is no movement in the forehead, whereas there is normal function and symmetry in the lower part of the face.
• Objective: To compare the interobserver variability of a new grading system to the currently recommended House-Brackmann Grading Scale.• Study Design: Prospective case-control study.• Setting: Tertiary referral center.• Patients: All patients with a facial nerve paresis/paralysis (whatever the cause).• Intervention: All patients were evaluated for their facial nerve function by three observers, independently, using both the new system and the House-Brackmann Grading Scale.
• Main Outcome Measure: The level of agreement between the three observers using both scales.• Results: With the movement, rest, secondary defects, and subjective scoring grading scale, a higher percentage of agreement between the observers was noticed than with the House-Brackmann Grading Scale.• Conclusion: The movement, rest, secondary defects, and subjective scoring grading system is more useful for grading facial nerve dysfunction in clinical practice than the House-Brackmann Grading Scale.
• Discussion :• Regional scales more reliable• Gross scales more practical• Regional scales - weighted and unweighted• variation of function within one grade• HBGS does not always correlate with the worst function• Grading scale takes patients‟ values into consideration• weighing is done by the patient.
Facial Nerve Grading System 2.0(3b)Facial Nerve Disorders Committee: Vrabec J T et al Otolaryng–Head and Neck 2009:140; 445-450
• Elements of the revision• Regional Assessment - added• Objective Score - deleted• Acute Facial Paralysis• Secondary Movement
• OBJECTIVE: To present an updated version of the original Facial Nerve Grading Scale (FNGS), commonly referred to as the House- Brackmann scale.• STUDY DESIGN: Controlled trial of grading systems using a series of 21 videos of individuals with varying degrees of facial paralysis.
• RESULTS: The intraobserver and interobserver agreement was high among the original and revised scales. Nominal improvement was seen in percentage of exact agreement of grade and reduction of instances of examiners differing by more then one grade when using FNGS 2.0. FNGS 2.0 also offers improved agreement in differentiating between grades 3 and 4.
• CONCLUSION:• FNGS 2.0 incorporates regional scoring of facial movement, providing additional information while maintaining agreement comparable to the original scale. Ambiguities regarding use of the grading scale are addressed.
• Discussion:• This study finds the rating scales are quite comparable.• The addition of subscores within grades 3 and 4 may be useful in defining outcomes after facial nerve grafts.• In this version, each region is graded as a percentage of normal and can be used when grading bilateral weakness.• Without a normal side as a reference, interobserver variability is expected to be higher.
• Cause for the fair agreement (kappa 0.4)• Cases studied and raters• Moderate degrees of facial weakness,• Examiners have diverse training backgrounds and practice settings. The more uniform the group of examiners are, the more likely they are to use a scale in a similar manner.• Finally, there was no “coaching” in the use of the scales. A training period prior to the study of a rating scale will distinctly improve the reliability among a selected group of examiners
• Psychometric Testing of the Gordon Facial Muscle Weakness Assessment Tool (abstract)(3b) Shirley C G,cynthia A B,Dax AP J School Nurs 2010 :26; 461-472
• Background: School nurses may be the first health professionals to assess the onset of facial paralysis/muscle weakness in school-age children.• Purpose : to test the psychometric properties of the Gordon Facial Muscle Weakness Assessment Tool (GFMWT) developed by Gordon.• Methods : Data were collected in two phases. In Phase 1, 4 content experts independently rated each of the 22 items on the GFMWT for content relevance. The ratings were used to generate Item and Scale Content Validity Index (CVI) scores.
• In Phase 2, school nurses (N = 74) attending a state conference independently rated referral urgency on a set of 10 clinical scenarios using the GFMWT.• Results : The GFMWT had an item and scale CVI of 1.0. Overall, the interrater reliability was .602 (p < .001).• Conclusion :When used by school nurses, the GFMWT was shown to be both a reliable and a valid tool to assess facial muscle weakness in school-age children.
1a SR (with homogeneity) of Level 1 diagnostic studies; CDR with 1b studies from different clinical centres.1b Validating cohort study with good reference standards; or CDR tested within one clinical centre.1c Absolute SpPins and SnNouts.2a SR (with homogeneity) of Level >2 diagnostic studies.2b Exploratory cohort study with good reference standards; CDR after derivation, or validated only on split-sample or databases.3a SR (with homogeneity) of 3b and better studies.3b Non-consecutive study; or without consistently applied reference standards.4 Case-control study, poor or non-independent reference.5 Expert opinion without explicit critical appraisal, or based on physiology, bench research or first principles.
Implication for practice• The utility of subjective scales lies in the ease of use and amount of information conveyed. The FNGS 2.0 produces similar results to the original FNGS and adds distinct regional information about facial movement.(C)• Further improvement of quantification of facial nerve function will require an objective rating scale.(C)• Additional advances in motion analysis software are expected and, when refined, should allow widespread use of consistent, repeatable, objective scoring.(C)
• The movement, rest, secondary defects, and subjective scoring grading system is more useful for grading facial nerve dysfunction in clinical practice than the House-Brackmann Grading Scale.(C)• GFMWT was shown to be both a reliable and a valid tool to assess facial muscle weakness in school-age children.(C)
• The newly developed scales can be used clinically when their, psychometric properties and clinical utility is further well established .• Uptil then the use of SFNGS(weighted regional), which has well established psychometric properties and clinical utility should be encouraged.
Implication for further research• Studies should be done comparing the revised version of H-B FGS and SFGS• Validation, reliability, and reproducibility assessments of the newly developed MoReSS should be done.• And its comparison and agreement to the most frequently used and popular SFGS system should be done .
• Revision of the existing SFGS by adding objective measurements and additional secondary defect should be done.