Reasons for Variability in the Reported Rate of Occurrence of Unilateral Spatial Neglect After Stroke

BACKGROUND AND PURPOSE: We sought to determine the frequency of occurrence of contralesional unilateral spatial neglect (USN) after stroke and to investigate the effect of side of lesion, nature of assessment tool used, and timing of assessment relative to stroke onset. METHODS: We performed a systematic review of published reports, identified by a search of electronic databases (MEDLINE 1966-1997, PSYCHLIT 1974-1996, and CINAHL 1982-1997) and by searching reference lists of the reports selected. Excluded were unpublished, non-English language, and nonhuman studies. RESULTS: Thirty published reports met the selection criteria, 17 of which directly compared right brain damage (RBD) and left brain damage (LBD). Contralesional USN appeared to occur more frequently after RBD than LBD in 16 of these. Both the assessment tool used and the time of assessment relative to stroke onset affected the reported rate of occurrence, although recovery rate data were inadequate (4 reports). CONCLUSIONS: The clinical belief that USN occurs more frequently after RBD than LBD was apparently supported by a systematic review of published data. However, an accurate estimate of the rates of occurrence and recovery after stroke could not be derived. Four reasons for the variability among studies were discussed, including subject selection, lesion localization, and nature and timing of assessment. Different USN disorders may exist, which may require type-specific rehabilitation approaches. This may have implications for epidemiological studies and for the development of new treatments. Theoretically driven epidemiological studies are required before adequately powered randomized controlled trials of rehabilitation can be conducted.