Introduction
Facial palsy affects many areas of life for the individual: social, aesthetic, functional, and psychological. Management of such patients has been overwhelmingly directed to physical interventions and in order to determine the effects of any interventions, there has been a need to document the status of the patient before and after intervention in order to monitor progress. Currently, rigorously validated quantitative measures of outcome are essential to determine severity, variation with time, and impact of therapeutic interventions. One of the greatest difficulties of facial palsy is the subjective nature of the severity of the disorder comprising a complex interplay of functional, aesthetic, and psychological factors (for both the patient and observer). This means that assessment of facial palsy is one of the most difficult problems to describe, quantify, classify, and follow over time.
What Can We Assess?
Given the multiple facets of facial palsy, assessment needs to be directed to the many heterogeneous aspects of the disorder. Appearance and its effect on social interaction; functional issues including eye closure, nasal airflow, speech, and oral continence; and how all these add up to make the patient feel (psychology/patient-reported outcomes) are not encompassed by a single assessment modality.
In order to document the facial nerve, we need to assess the appearance of the face for signs of dysfunction in both static and dynamic states. We may record brow ptosis and rhytids of the forehead. Examination of the palpebral aperture and lid positions, ptosis of the cheek, the depth of the nasolabial fold, and commissure position are all features that indicate facial nerve dysfunction at rest. With voluntary movement we can detect asymmetries of motion such as brow elevation, lagophthalmos, smile asymmetry, lower lip asymmetry, and a failure to achieve lip seal. Platysmal dynamic abnormalities can also be manifest. One difficulty is in documenting whether movement is normal or abnormal, as asymmetric movement is generally considered abnormal. For example, a patient may have similar excursion of the commissure but the vector may differ resulting in a “crooked” smile. In addition, abnormal involuntary movements can be observed—synkinesis. Such movements are debilitating to many patients as they significantly contribute to the facial difference in animation; patients often avoid animation in social discourse in order to hide these.
In addition to the observable results of facial palsy, there are numerous ways to assess functional compromise. Lacrimation (dry eyes or epiphora), corneal examination, and airflow symptoms can be quantified. Oral continence with food and fluid and speech intelligibility are also affected and may be recorded. Gustation (taste) and hearing may also be affected and can be measured or reported by the patient. Gustation has specific issues in that there are no rigorously validated measures of taste that are comparable between individuals. Finally, apart from the appearance and functional issues, there is the psychological impact on the patient that is very individual in its manifestation for the patient’s quality of life.
Currently there are numerous scales and assessment tools for many different aspects of facial nerve disease. These range from palsy-specific measures geared to detailed examination of the eye such as the CADS scale (which is a facial palsy-specific grading instrument that has subjective and objective parameters to describe the C ornea, A symmetry, D ynamic function and S ynkinesis), to the application of rhinomanometry to study nasal airflow or the Goldman-Fristoe Test of Articulation 3, which are not designed specifically for facial palsy but provide quantitative information that may be used to evaluate clinical status. Therefore, it is clear that over time many different methods of assessment have been used to try and document the status of the palsy patient.
This chapter will focus on facial nerve assessment with (some may argue) the most pertinent and immediate factor being the visual appearance of the patient, which is determined by the facial nerve function as a motor to the facial muscles.
Documenting Facial Nerve Function
At the most basic level, the facial nerve serves to maintain muscle tone and effect movement in the face. Thus, the documentation of facial nerve function has historically focused on the static appearance of the face (muscle tone) and facial movement. Other aspects of facial nerve function (e.g., taste, lacrimation, hearing) have generally been omitted from assessment tools directed to facial nerve function. Such function may be recorded photographically and attempts have been made to grade this function based on the severity of the facial palsy.
Visual Documentation
The standard documentation of appearance and facial movement is by photography or videography. The traditional approach was to take a photograph in repose with pictures that document the standard movements of the each of the divisions of the facial nerve (e.g., raised eyebrows, smile). Evaluation of the literature shows that there are very few publications that relate to photographic documentation of facial palsy with inconsistent approaches presented. Similarly, all professionals in a recent survey used photography to document facial palsy but only four views were consistently used (repose, smile, raised eyebrows, and eye closure). This indicates that there are no accepted standards for which photographic views should be recorded. The lack of consistency stimulated the Sir Charles Bell Society (https://www.sircharlesbell.com; an international society to promote the sharing of knowledge between professionals of all disciplines that specialize in the management of facial nerve disorders) to suggest minimum standards for photographic recordings to document facial palsy.
Almost 82% of respondents in the same survey used videography; this is considered essential to capture spontaneous motion, synkinesis, and speech (when coupled with sound recording). The use of video allows the observer to see the movement of the face and grade the palsy in a manner that cannot be conveyed with static pictures ( 
). As such, this modality can be used as a method of exchanging information between clinicians with a high degree of fidelity allowing observers to grade or assess the palsy with greater accuracy.
Apart from video and photographs, other visual modalities exist and are being used in some institutions. Three-dimensional imaging is becoming cheaper and simpler to perform and may allow more detailed analysis , but is not a routine assessment in the majority of centers. The downside is the time taken to acquire the images in different positions (especially in the pediatric population) but this essentially gives us the same issue of static pictures from which to assess the facial palsy, albeit from multiple perspectives. Four-dimensional (“three-dimensional video”) technology is also available and will give a great deal of information on dynamic movement and allow a 360-degree assessment of the palsy. However, limitations in computer processing power and data storage (as well as cost) remain the most significant barriers to adoption in the medium term. One may also argue that they do not convey much more information than two-dimensional photography and video, unless you are making quantitative surface measurements typically part of a research project rather than routine clinical assessment.
Assessment in General
Thus far, we can appreciate that there are a large number of areas that can be assessed and documented. But what is the best way to assess the patient efficiently in the clinic? Visual documentation records the status of the patient but in itself does not interpret the severity of the palsy. In order to do so, numerous authors have attempted to create ranked scales that score the severity of the palsy and try to present this as a numeric output. Such an approach has two components: a scale to measure against and an interpretation of this scale which can be objective or subjective. The scale itself needs to be validated and based on evidence and it should have interobserver (between individuals) and intraobserver (the same individual at different time points) consistency. Components of an assessment can be objective (e.g., a measurement of movement) or subjective (e.g., is that movement symmetric?). When an assessment is performed, it relies on the clinician (rater) and the patient (subject) to communicate effectively and may be subject to confounding factors that affect this interaction.
Historic Scales
Currently, many scales exist because there is no perfect grading system that is fast, cost effective, sensitive, specific, minimally invasive, wholly objective, and quantitative. Some scales are descriptive, such as that of Botman and Jongkees ( Table 7.1 ), which employs a five-point scale to document the degree of paralysis. They look at the patient’s face as a whole and attempt to grade the palsy based on an overall appearance. A modification of this approach is to look at specific regions of the face to create a regional scoring that independently evaluates different areas of facial function to compile an overall score. House’s seminal paper details many of the early grading systems, as well as analyzing their benefits and limitations. Key points that remain pertinent today are that regional scales are generally reliable with observers being more consistent in their ratings. However, descriptive scales have greater agreement between observers as there are fewer broad categories within which to rank patients. However, in contrast to regional scales, descriptive scales are poorer at differentiating different degrees of facial nerve function.
| 0 | Normal facial nerve activity | |
| 1 | Light paresis | Normal at rest, talking normal, the eyes can be closed, some dissymmetry in laughing and whistling |
| 2 | Moderate paresis | Normal at rest; asymmetry in talking and laughing, the eyes cannot be closed |
| 3 | Severe paralysis | Asymmetry at rest, dysfunction in movements |
| 4 | Total paralysis | No tone, total loss of function, contracture of the muscles may result in apparent improvement and degeneration atrophy may cause a more serious aspect |
House-Brackmann Scale
Due to the difficulty in trying to describe the degree of facial palsy and recovery in their cohort of acoustic neuroma patients, Brackmann and House described a questionnaire and method of measuring brow and mouth movement to standardize the way they record the recovery of their patients’ function. It was performed by the patients as a subjective exercise but includes an objective measurement. The following year a modified version of this was adopted by the Facial Nerve Disorders Committee of the American Academy of Otolaryngology-Head and Neck surgery as “ a universal standard for grading facial nerve recovery ”. In this iteration, the scale comprised a six-point descriptive scale ( Box 7.1 ).
Grade I—Normal
Normal facial function in all areas
Grade II—Slight Dysfunction
Gross: slight weakness noticeable on close inspection; may have very slight synkinesis
At rest: normal symmetry and tone
Motion: forehead—moderate to good function; eye—complete closure with minimum effort; mouth—slight asymmetry
Grade III—Moderate Dysfunction
Gross: obvious but not disfiguring difference between two sides; noticeable but not severe synkinesis, contracture, and/or hemi-facial spasm
At rest: normal symmetry and tone
Motion: forehead—slight to moderate movement; eye—complete closure with effort; mouth—slightly weak with maximum effort
Grade IV—Moderate Severe Dysfunction
Gross: obvious weakness and/or disfiguring asymmetry
At rest: normal symmetry and tone
Motion: forehead—none; eye—incomplete closure; mouth—asymmetric with maximum effort
Grade V—Severe Dysfunction
Gross: only barely perceptible motion
At rest: asymmetry
Motion: forehead—none; eye—incomplete closure; mouth—slight movement
Grade VI—Total Paralysis
No movement
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