| Secondary survey | |||||
| Category | NMO (category 1) | NMOsd (category 2) | NMOsd (category 3) | NMOsd (category 4) | Total |
| Number of patients | 506 | 180 | 298 | 58 | 1042 |
| Sex ratio (M:F) | 1:9.8 | 1:3.2 | 1:5.0 | 1:57.0 | 1:6.4 |
| Age at onset (years) | 39.4 (39) | 43.0 (43) | 46.7 (48) | 41.2 (41) | 42.2 (43) |
| Age at the time of study (years) | 52.8 (53) | 48.9 (50) | 53.3 (55) | 47.3 (47) | 52.0 (53) |
| Family history (%) | 12 (2.3) | 1 (0.5) | 4 (1.3) | 1 (1.7) | 16 (1.7) |
| Able to walk (%) | 174 (34.0) | 129 (70.9) | 36 (37.7) | 36 (61.0) | 463 (42.9) |
| Wheelchair bound (%) | 115 (22.5) | 8 (4.4) | 60 (19.9) | 2 (3.4) | 187 (17.3) |
| Bedridden (%) | 35 (6.8) | 1 (0.5) | 9 (3.0) | 1 (1.7) | 46 (4.3) |
| Bilateral severe visual impairment (%) | 81 (15.8) | 27 (14.8) | 0 (0.0) | 1 (4.3) | 109 (10.5) |
NMO, neuromyelitis optica; NMOsd, NMO spectrum disorder. For the primary survey, the actual numbers of patients are shown, with the estimated numbers of patients in parentheses. Data for the secondary survey are reported as mean (median) for age at onset and age at the time of study and as numbers (percentages) for family history, able to walk, wheelchair bound, bedridden and bilateral severe visual impairment. Patients with NMO had to fulfil both of the absolute criteria, that is , optic neuritis and acute myelitis. These patients also met at least two out of the three supportive criteria, namely contiguous spinal cord lesion extending over > 3 vertebral segments, brain MRI not meeting Paty’s criteria for MS and positive results in an AQP4 antibody test (category 1). Patients with NMOsd were classified into three groups (categories 2, 3 and 4). Patients in category 2 had no spinal cord lesions, those in category 3 had no optic nerve lesions and those in category 4 had positive results in the anti-AQP4 antibody test but were not categorised as category 2 or 3.