Analysis
Data were extracted from the medical records and questionnaires for analysis, including information related to medical and developmental histories, level of ambulation and cognition, and degree of functional disability. Medical and developmental histories, level of ambulation, and level of cognition were assessed based on questions from the medical history and current medical history questionnaires. The degree of functional disability was assessed based on the score from a 31-point functional disability scale (FDS) from 0 (lowest level of achievement) to 31 (highest level of achievement).9 This score was derived from measures of nine areas of function: employment/education, speech, diet, dressing, toileting, drawing/writing, walking, sitting, and breathing (See Figure 1). FDS scores were gathered from one of two mechanisms. 1) From chart review based on FDS scores previously obtained as part of prior participation in a PLP1-RD study or as part of clinical care for PLP1-RD or 2) From a series of questions asked in the medical history and current medical history questionnaires.