Table 2 The clinical phenotype comparison between different clinical subgroup

Disease onset

Nystagmus, n (%)

28 (100)

56(100)

26(96.3)

Onset age (range)

0.85 m (0, 12)

1 (0, 24)

2 m (0, 16)^b

Hypotonia, n (%)

18 (64.3)^a

50 (89.3)

25 (92.6)^b

Onset age (range)

6.5 m (2. 18)

8 m (3, 26)

7 m (2, 18)

Disease progression

Nystagmus decrease

13 (46.4)

32 (57.1)

19 (73.1)

Decrease age (range)

12 m (4, 96)

26 m (8, 79)

24 m (7, 260)

Stridor

15 (53.6)^a

15 (26.8)

5 (18.5)^b

Motor milestone

Head control, n (%)

12 (42.9)

48 (85.7)

27 (100)

Acquire age (range)

11 m (4, 71)

10 (3, 60)^c

5 (3, 18)^b

Sit, n (%)

4 (14.3)

14 (25)^c

26 (88.9)^b

Acquire age (range)

47 (7, 96)

33 (8, 86)^c

12 (6, 84)

Stand, n (%)

1 (3.6)

4 (7.1)

5 (18.5)

Acquire age (range)

13 (13, 13)

41 (26, 48)

36 (16, 84)

Walk, n (%)

1 (3.6)

2 (3.6)

2 (7.4)

Acquire age (range)

15 (15, 15)

38.5 (29, 48)

108 (96, 120)

Cognitive milestone

Recognize stranger, n (%)

21 (75.0)

51 (91.1)

25 (92.6)

Acquire age (range)

8 (3, 48)

8 (4, 60)

8 (4, 36)

Speak, n (%)

11 (39.3)^a

44 (78.6)

25 (92.6)^b

Acquire age(range)

36 (12, 72)^a

19 (6, 86)

12 (6, 30)^b

Other neurological finding

Joint contracture, n (%)

8 (28.6)

10 (17.9)

5 (18.5)

Spasticity tetraparesis, n (%)

0

4 (7.1)

1 (3.7)

Pyramidal signs, n (%)

3 (10.7)

3 (5.4)

6 (22.2)

Brainstem dysfunction, n (%) (Swallowing difficulty, respiration dysfunction)

15 (53.6)^a

8 (14.3)

0 (0)^b

Ataxia, n (%)

2 (7.1)

3 (5.4)

2 (7.4)

Seizure, n (%)

4 (14.3)

4 (7.1)

0