Grading facial nerve_function

Recent advances
on
Grading 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.

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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), Abridged

Janssen‟s Scale

Sunnybrook 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

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• 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 LMI
NOTTINGAMS _
SYSTEM

Agreement of score with Widely used in japan
Yanagihara 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

Instructions for Use of FNGS 2.0

• 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.

Grading facial nerve_function

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