Introduction to Single System Designs for Neurorehabilitation Research

The evolution of evidence based practice in health care has produced an emphasis on documenting the effectiveness of interventions used in neurologic rehabilitation. This paper describes the methods of single system designs as one approach to address the demands of evidence based practice. Single system designs include a wide range of strategies that are practice based and practitioner oriented. The designs provide an alternative to traditional experimental approaches requiring the random assignment of a large number of subjects to treatment and no treatment (control) groups. The characteristics of single system designs include the repeated assessment of individual ized outcome measures for single patients or small groups of patients treated as a sin gle unit. The designs can be used to monitor patient improvement over time and to demonstrate relationships between intervention and outcome measures for specific pa tients. Data analysis focuses on the presentation and interpretation of patterns of re sponses over time. The emphasis in single system data analysis is on the clinical sig nificance of individual change versus the statistical significance of comparisons between groups. The advantages and limitations of single system designs are discussed, and the argument is made that these designs can contribute to the evolving knowl edge base in neurologic rehabilitation.