Objective: To compare effects of STN-DBS and dopamine replacement therapy (DRT) on behaviour in PD in a 2 year follow-up study.

Background: A large panel of behavioural modifications have been described in PD patients treated by STN-DBS. Interpretation of variable behavioural outcomes of STN-DBS is hampered by the difficulty in disentangling changes in behaviour related either to DRT modulations allowed by STN-DBS or to possibly a STN-DBS direct effect. By classifying the full spectrum of behaviours observed in PD into i) hypodopaminergia (apathy, depression, anxiety) score range 0-20 points ii) hyperdopaminergia (impulse control disorders) score range 0-56 points and iii) non-motor fluctuations (NMF) score range 0-8 points, the Ardouin behavioural scale in PD (ABSPD) (Rieu et al., 2015) would allow to better separate behaviours related to STN-DBS or DRT.

Methods: In the EARLYSTIM study comparing STN-DBS to Best Medical Treatment (BMT) in PD patients disabled by early motor complications (Schuepbach et al.,2013), the ABSPD was used to evaluate changes in behaviour between baseline and 2 year follow-up. Patients were randomized at baseline into BMT (n=127) or STN-DBS groups (n=124). DRT was expressed as levodopa-equivalent dose (LED). Between-group differences of mean change in ABSPD variables and their correlation with DRT changes were analysed. Mixed model regression was used for the statistical analysis. P-values ≤0.05 were considered statistically significant.

Results: Over the 2 year follow-up LED was reduced by 363.3mg/day in the surgical group and increased by 245.8 mg/day in BMT. NMF improved with STN-DBS (-0.65 points, p<0.05) and did not change with BMT. Hyperdopaminergia improved with STN-DBS (-1.3 points, p<0.05) and worsened with BMT (+1.1 points, p<0.05). Hypodopaminergia did not change under either therapy. The DBS group had significant reductions in NMF (p=0.003) and hyperdopaminergia (p<0.001) as compared with BMT. Antidepressants were stopped in 12 patients on STN-DBS vs 4 patients on BMT. Neuroleptics were introduced in 9 patients under BMT vs 1 patient under STN-DBS.

Conclusions: Our data suggest that STN-DBS allows reducing DRT without inducing hypodopaminergia and requires less psychotropic medications compared to BMT. NMF are improved with STN-DBS. While hyperdopaminergic behaviors can be improved with chronic STN-DBS, they tend to worsen with BMT.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/earlystim-stn-dbs-alleviates-behavioural-side-effects-of-dopamine-replacement-therapy-when-compared-to-best-medical-treatment/