Table 1.

Characteristics of the eligible studies.

Number	Author	N	Age	Disease duration	DBS programming	State in the evaluation	Scale	Follow-up	Preoperative score	Preoperative LEDD	Postoperative score	Postoperative LEDD
1	Houvenaghel et al. [21]	26	56.6 ± 7.4	11.47 ± 4.54	Bilateral STN-DBS	Drug on and stimuli on	AES	3 months	31.8 ± 7.0	1271.2 ± 555.6	31.2 ± 7.7	758.0 ± 407.79
2	Robert et al. [20]	44	56.3 ± 7.5	11.4 ± 4.1	Bilateral STN-DBS	Drug on and stimuli on	AES	3 months	31.4 ± 6.4	1280.8 ± 632.4	31.6 ± 7.1	889.9 ± 209.3
3	Lewis et al. [17]	27	61.1 ± 9.1	12.7 ± 6.7	Bilateral STN-DBS	Drug on and stimuli on	AES	1 year	34.04 ± 9.58	831.5 ± 425.91	37.44 ± 8.71	359.23 ± 264.46
4	Lewis et al. [18]	28	61.1 ± 8.9	12.43 ± 6.74	Bilateral STN-DBS	Drug on and stimuli on	AES	1 year	33.85 ± 9.71	832 ± 426	37.0 ± 8.91	359.3 ± 264.5
5	Lhommee et al. [16]	67	57.8 ± 7.2	10.5 ± 3.1	Bilateral STN-DBS	Drug on and stimuli on	SAS	1 year	6.2 ± 3.5	1026 ± 459	9.4 ± 4.5	284 ± 312
6	Chou et al. [19]	10	62.1 ± 6.5	9.1 ± 5.8	Bilateral STN-DBS	Drug on and stimuli on	SAS	6 months	13.2 ± 8.6	1164.9 ± 752.9	13.6 ± 7.4	567.9 ± 512.4
7	Drapier et al. [15]	17	56.9 ± 8.7	11.8 ± 2.6	Bilateral STN-DBS	Drug on and stimuli on	AES	3 months	37.2 ± 5.5	-	42.5 ± 8.9	-
8	Castelli et al. [14]	19	62.1 ± 4.2	14.7 ± 5.0	Bilateral STN-DBS	Drug on and stimuli on	SAS	17 months	11.6 ± 4.1	1192.5 ± 415.7	12.6 ± 5.3	571.6 ± 274.8
9	Drapier et al. [13]	15	59.7 ± 7.6	12.2 ± 2.8	Bilateral STN-DBS	Drug on and stimuli on	SAS	6 months	13.0 ± 6.5	1448 ± 400	18.8 ± 9.7	1127 ± 482

AES: Apathy Evaluation Scale; SAS: Starkstein Apathy Scale.