Table 3.

Studies of functional, QOL, and global impression outcomes after DBS in PD.

Study	Functional, QOL, or global impression scale	Significant predictors	Number of patients	Time lapse since surgery
Welter et al., 2002	UPDRS II	(i) Age (ii) Disease duration (iii) UPDRS III (iv) Axial motor score (v) LED	41	6 months
Daniels et al., 2011	PD-Q39 SF-36	(i) Daily off time (+ve) (ii) Lower dyskinesia score (+ve) (iii) Improvement in UPDRS III (+ve) (iv) Improvement in psychiatric scales (+ve) (v) Reduction of dyskinesia (−ve)	61	6 months
Soulas et al., 2011	PD-Q39 SF-36	(i) Age (ii) Disease duration (iii) Depression (iv) Less use of social support coping	41	6 months and 12 months
Smeding et al., 2011	PDQL	(i) L-dopa response at baseline (+ve)	105	12 months
Maier et al., 2013	Subjective perceived outcome	(i) Depression (ii) Apathy	30	3 months
Floden et al., 2014	PD-Q39	(i) Depression (ii) Single-trial learning (episodic memory) (iii) Preoperative PD-Q39 score (iv) Bilateral surgery (+ve)	85	8 months (average)
Genc et al., 2016	MDS-UPDRS II EQ-5D CGIS	(i) Household median income	125 (43 for MDS-UPDRS II and EQ-5D)	6 months and 12 months
Maier et al., 2016	Subjective perceived outcome	(i) Apathy (ii) Axial motor score	28	12 months
Abboud et al.	MDS-UPDRS II EQ-5D PGIS CGIS	(i) Falls/balance dysfunction (ii) Dyskinesia (iii) Absence of tremors (iv) Freezing (v) UPDRS III (vi) Preoperative BMI	130 (45 FOR MDS-UPDRS II and EQ-5D)	6 months and 12 months

UPDRS II: Unified Parkinson's Disease Rating Scale, part 2: activities of daily living; LED: L-dopa equivalent dose; PD-Q39: Parkinson's Disease Questionnaire-39; SF-36: 36-Item Short Form Health Survey; PDQL: Parkinson's Disease Quality of Life Questionnaire; MDS-UPDRS II: Movement Disorders Society-Unified Parkinson's Disease Rating Scale, part 2: motor experience of daily living; EQ-5D: European Quality of Life 5-dimension Questionnaire; CGIS: Clinician's Global Impression of Change Scale; PGIS: Patient Global Impression of Change Scale.