Table 1 General characteristics of the included studies

Chen 2014 [34]

1/12–10

1/6–8

53.4 ± 14.8

52.9 ± 14.5

21/21

20/18

J + H + Vitamin B12

J+ Vitamin B12

4 weeks

n.r.

NCV, TER

Qi 2010 [35]

(103.24 ± 17.62)/12

(98 ± 20.9)/12

56.31 ± 7.4

59.7 ± 8.1

27/15

25/15

J + H + Vitamin B12

J+ Vitamin B12

4 weeks

n.r.

NCV, TER

Li 2001 [36]

(37 ± 6)/12

(36 ± 6)/12

60 ± 12

62 ± 8

17/14

12/19

J + H + Vitamin B12

J+ Vitamin B12

4 weeks

No

NCV, TER

Chen 2007 [37]

10.8

10.2

55.2 ± 5.4

56.3 ± 6.1

20/21

19/22

J + H + Vitamin B12 & B1

J+ Vitamin B12 & B1

30 days

0/1

NCV, TER

Lin 2010 [38]

7.0 ± 2.3

7.2 ± 2.2

56.7 ± 1.8

54.9 ± 6.5

52/52

58/41

J + H + Vitamin B12

J+ Vitamin B12

80 days

n.r.

NCV, TER

Qiao 2006 [39]

n.r.

n.r.

n.r.

n.r.

n.r.

n.r.

J + H

J+ Vitamin B12

20 days

No

NCV, TER

Liu 2006 [40]

7.3

8.31

58.2

58.4

17/30

16/30

J + H

J+ Vitamin B12

8 weeks

n.r.

NCV, TER

Hua 2009 [41]

8.2

7.5

58.45

60.65

12/20

18/13

J + H

J+ Vitamin B12

30 days

n.r.

TER

Cao 2012 [42]

n.r.

n.r.

55.8 ± 4.2

54.7 ± 3.3

35/31

28/26

J + H

J+ Vitamin B12

8 weeks

5/2

NCV, TER

Zhang 2007 [43]

7.93 ± 2.36

6.88 ± 2.40

56.81 ± 9.36

55.64 ± 9.73

13/17

16/14

J + H

J+ Vitamin B12

8 Weeks

n.r.

TER

Hong 2006 [44]

7.72 ± 4.01

7.62 ± 3.80

58.22 ± 6.31

56.83 ± 7.02

20/10

18/12

J + H

J+ Vitamin B12, B1 and NGF

80 days

No

TER

Chen 2005 [45]

2.32 ± 1.50

2.34 ± 1.21

51.20 ± 7.81

52.3 ± 8.52

28/17

18/12

J + H

J+ Vitamin B12 and B6

4 weeks

n.r.

NCV, TER

Lin 2011 [46]

11.63 ± 5.09

11.5 ± 5.98

61.85 ± 8.09

62.7 ± 8.11

35/25

18/12

J + H

J+ Vitamin B12

3 months

n.r.

NCV, TER

Yi 2008 [47]

11.06 ± 3.67

11.13 ± 3.59

59.87 ± 6.37

60.03 ± 6.46

16/14

15/15

J + H

J+ Vitamin B12

4 weeks

n.r.

NCV, TER

Li 2012 [48]

8.4

7.6

56.5

54.8

35/25

38/22

J + H

J+ Vitamin B12

4 weeks

No

NCV, TER

Chen 2009 [49]

11.16 ± 3.57

10.93 ± 4.01

59.67 ± 6.27

60.03 ± 6.42

16/14

15/15

J + H

J+ Vitamin B12

12 weeks

n.r.

TER

Huang 2015 [50]

6–20

5–19

41–79

40–70

30/30

40/20

J + H

J+ Vitamin B12

4 weeks

n.r.

NCV, TER

Song 2015 [51]

(52.3 ± 41.3)/12

(54.3 ± 36.7)/12

59.8 ± 6.3

59.2 ± 9.4

14/16

13/17

J + H

J+ Vitamin B12

12 weeks

n.r.

NCV, TER

Chen 2015 [52]

6.91 ± 5.57

6.30 ± 4.97

54.32,61.07

54.38,62.27

14/16

17/13

J + H

J+ Vitamin B12

60 days

n.r.

NCV, TER

Zhao 2015 [53]

7.60 ± 5.8

7.11 ± 4.90

57.41 ± 8.98

55.83 ± 9.64

22/18

21/19

J + H

J+ Vitamin B12

8 weeks

3/4

NCV, TER

Liu 2015 [54]

6.44 ± 2.87

6.34 ± 2.78

53.15 ± 10.23

52.25 ± 10.18

34/31

35/29

J + H + α-lipoic acid

J+ a-lipoic acid

4 weeks

1/3

NCV, TER

Ma2015 [55]

8.5 ± 2.9

8.8 ± 2.7

62.1 ± 6.7

61.8 ± 6.9

26/17

28/15

J + H + α-lipoic acid

J+ a-lipoic acid

4 weeks

n.r.

NCV, TER

Chen 2015 [56]

12.62 ± 3.17

11.26 ± 3.51

60.16 ± 5.71

61.4 ± 6.15

17/13

15/15

J + H + Vitamin B12

J+ Vitamin B12

4 months

No

NCV, TER

Zhang 2015 [57]

8.9 ± 2.1

9.1 ± 2.1

53.7 ± 2.3

54.2 ± 2.5

41/19

39/21

J + H + Vitamin B12

J+ Vitamin B12

4 weeks

1/0

NCV, TER

Lang 2015 [58]

10.72 ± 7.96

11.34 ± 8.25

58.75 ± 19.01

57.02 ± 18.53

46/36

52/30

J + H + Vitamin B12 + α-lipoic acid

Vitamin B12 + a-lipoic acid

2 weeks

n.r.

NCV, TER