Can total electrical energy (TEED) after subthalamic DBS alter verbal fluency in Parkinson's disease patients? A preliminary evidence.

Objective: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor outcomes in Parkinson's disease (PD) but may have adverse long-term effects on specific cognitive domains. The aim of this study was to investigate the association between total electrical energy (TEED) delivered by DBS and postoperative changes in verbal fluency.
Methods: Seventeen PD patients undergoing bilateral STN-DBS were assessed with the Alternate Verbal Fluency Battery (AVFB), which includes phonemic (PVF), semantic (SVF), and alternate verbal fluency (AVF) tests, before surgery (T0) and after 6 (T1) and 12 months (T2). Bilateral TEED and average TEEDM were recorded at T1 and T2. For each AVFB measurement, changes from T0 to T1 (Δ-01) and from T0 to T2 (Δ-02) were calculated.
Results: At T1, PVF ( p = 0.007) and SVF scores ( p = 0.003) decreased significantly. TEED measures at T1 and T2 were unrelated to Δ-01 and Δ-02 scores, respectively. However, an inverse, marginally significant association was detected between the TEEDM and Δ-01 scores for the AVF ( p = 0.041, against an α _adjusted = 0.025).
Conclusions: In conclusion, the present reports provide preliminary evidence that TEED may not be responsible or only slightly responsible for the decline in VF performance after STN-DBS in PD.