The facial disability index: Reliability and validity of a disability assessment instrument for disorders of the facial neuromuscular system

Background and Purpose. Disorders of the facial neuromuscular system can result in marked disfigurement of the face and difficulties in activities of daily living such as eating, drinking, and communicating. No systematic means of measuring the disability associated with facial nerve disorders exists. The purpose of this investigation was to examine the reliability and construct validity of the Facial Disability Index (FDI), a disease-specific, self-report instrument for the assessment of disabilities of patients with facial nerve disorders. Subjects and Methods. The FDI was administered to 46 ambulatory patients of the University of Pittsburgh Medical Center's Facial Nerve Center. The relationship of the FDI subscale and total scores with clinical impairment measures was determined, and a comparison of the use of the FDI and subscales of the more general SF-36 was made. Results, The FDI subscales produced reliable scores (theta reliability: physical function=.88; social/well-being-function=.83). Construct validity of the FDI physical function subscale was demonstrated by a correlation with the clinician's physical examination of facial movement. The FDI social/well-being subscale was associated with the FDI physical function subscale and with a clinical assessment of psychosocial status within a subset of the sample (n=14). The FDI represented the relationship between impairments, disability, and psychosocial status better than the generic SF-36 did. Conclusion and Discussion, The FDI subscales produce reliable measurements, with construct validity for measuring patient-focused disability of individuals with disorders of the facial motor system.