Objective: to evaluate the utility and correlates of UPDRS III OFF scores as  indicators of response to DBS.

Background: Changes in UPDRS III OFF scores have been often used as an indicator of response to DBS surgery. Consequently an artificial cut off of 30% of improvement has been set to divide responders (R) to non-responders (NR). In general values lower than 30% have been linked to DBS misplacement and/or erroneous indication.

Method: We compared 7 patients with a reduction of UPDRS III lower than 30% at the 12 months evaluation  from our data set operated in the last two years period, classified as NR, with 7 matched patients classified as R. Demographic, basal clinical and outcome variables were compared using Mann-Whitney’s U test.

Results: NR patients (n: 7) age of onset: 56 interquartile range (IQR): 43 to 63 years; age at surgery: 68 years IQR: 61 to 73; target: 5 GPi), and R patients (n: 7) age of onset: 56 year IQR: 50-59; age at surgery: 66 IQR: 63 to 71; target: 5 GPi. Baseline OFF UPDRS III were NR: 35 IQR: 31 to 49; R: 53 IQR: 45-57 (p=0.084).There were statistically significant differences in the percentage of reduction in baseline UPDRS III at 12 months follow-up (R 46% IQR: 36 to 65%; NR 14% IQR: -6 to 25% p=<0.05). There were no statistically significant differences between NR and R patients in changes in UPDRS II (NR: 10.5% [-31% to 42%]; R: 37% [28.5% to 48.5%]), ON-UPDRS III (NR: 15% [14% to 29%]; R: 23% [9% to 36%]) or UPDRS IV (NR: 67% [57% to 81%]; R: 83% [46% to 100%]). Baseline UPDRS II, ON-UPDRS III and UPDRS IV showed no correlation with 12 month follow-up scores. Only baseline OFF-UPDRS III scores had a negative correlation with 12 month follow-up OFF-UPDRS III scores (Spearman’s rho: -0.82 p:<0.05).

Conclusion: Our results show that in spite of a suboptimal reduction in OFF-UPDRS III-scores from baseline, NR patients still show improvement in ON-state scores,and motor complications. The severity of the  basal OFF measured by UPDRS III might be determinant of the degree of motor response measured by the reduction of said scale at follow-up, but not on the effect on motor fluctuations, and dyskinesias which can be in most of the patients the main indicators for surgery. The definition of R and NR might  need to involved wider evaluation than just off UPDRS III.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-reduction-in-updrs-3-off-score-the-best-indicator-of-response-to-dbs/