Facial disability index (FDI): Adaptation to Spanish, reliability and validity

OBJECTIVES To adapt to Spanish the facial disability index (FDI) described by VanSwearingen and Brach in 1995 and to assess its reliability and validity in patients with facial nerve paresis after parotidectomy. STUDY DESIGN The present study was conducted in two different stages: a) cross-cultural adaptation of the questionnaire and b) cross-sectional study of a control group of 79 Spanish-speaking patients who suffered facial paresis after superficial parotidectomy with facial nerve preservation. The cross-cultural adaptation process comprised the following stages: (I) initial translation, (II) synthesis of the translated document, (III) retro-translation, (IV) review by a board of experts, (V) pilot study of the pre-final draft and (VI) analysis of the pilot study and final draft. RESULTS The reliability and internal consistency of every one of the rating scales included in the FDI (Cronbach's alpha coefficient) was 0.83 for the complete scale and 0.77 and 0.82 for the physical and the social well-being subscales. The analysis of the factorial validity of the main components of the adapted FDI yielded similar results to the original questionnaire. Bivariate correlations between FDI and House-Brackmann scale were positive. The variance percentage was calculated for all FDI components. CONCLUSIONS The FDI questionnaire is a specific instrument for assessing facial neuromuscular dysfunction which becomes a useful tool in order to determine quality of life in patients with facial nerve paralysis. Spanish adapted FDI is equivalent to the original questionnaire and shows similar reliability and validity. The proven reproducibility, reliability and validity of this questionnaire make it a useful additional tool for evaluating the impact of facial nerve paralysis in Spanish-speaking patients.