Surgery for Parkinson's disease improves disability but not impairment components of the UPDRS-II

The Unified Parkinson's Disease Rating Scale (UPDRS) activities of daily living (ADL) items have been described as reflecting both disability (true ADL items) and impairment (rather than ADLs). As a result of combining these scores, UPDRS part II scores may not accurately reflect the impact of surgery on ADLs [Hariz G.M., Lindberg M., Hariz M.I., Bergenheim A.T. Does the ADL part of the unified Parkinson's disease rating scale measure ADL? An evaluation in patients after pallidotomy and thalamic deep brain stimulation. Mov Disord 2003;18:373–81.]. The goal of the present study was to assess the metric properties of the ADL section of the UPDRS in terms of its ability to measure surgical change. We tested the effects of unilateral pallidotomy (N=14) and bilateral subthalamic nucleus (STN) DBS (N=11) on both disability and impairment components of the UPDRS-II at uniform follow-up assessment periods of 6 months and 1 year, with a subset of pallidotomy patients (N=9) re-assessed at 2 years. Across the follow-up periods in both patient groups, items identified as best reflecting disability showed significant improvement from pre-surgical levels, whereas items representing impairment showed no overall change. Consistent with this, change in total ADL scores was tempered by the inclusion of the impairment items. Because the measurement of a patient's functional status is important in determining the effectiveness of an intervention, analysis of appropriate items from the UPDRS ADL section is imperative.