Symptom presentation
| Presenting symptoms | Number of patients (n=524) | Frequency (%) | Sibling pairs concordant |
| Lower limb dysfunction | 174 | 33 | 32 |
| Upper limb dysfunction | 17 | 3 | 4 |
| Long tract sensory | 131 | 25 | 28 |
| Sphincter dysfunction | 4 | 0.7 | 2 |
| Sexual dysfunction | 1 | 0.2 | 0 |
| Facial motor weakness | 8 | 1.4 | 0 |
| Facial sensory weakness | 15 | 3 | 2 |
| Oculomotor | 35 | 7 | 3 |
| Vestibular dysfunction | 27 | 5 | 1 |
| Bulbar dysfunction | 0 | 0 | 0 |
| Visual symptoms | 98 | 19 | 7 |
| Psychiatric symptoms | 0 | 0 | 0 |
| Cognitive deterioration | 0 | 0 | 0 |
| Other | 10 | 2 | 2 |
| Unknown | 4 | 0.7 | 0 |