Neurological score (a functional assessment of impairment of disability) and our classification of impairment into three groups
| Neurological score |
| • Grade 0, no impairment or disorder detected |
| • Grade 1, impairment or disorder detected but no apparent disability and requiring no treatment |
| • Grade 2, impairment or disorder detected with no apparent disability but requiring treatment |
| • Grade 3, impairment plus disorder but compensates well enough to cope |
| • Grade 4, impairment plus disorder requiring continuing treatment support or management |
| • Grade 5, impairment plus disorder preventing satisfactory functioning |
| Major impairment |
| • General cognitive index < 70 |
| • Neurological score grade 4 or 5 |
| • Sensory-neural hearing loss requiring aids |
| • Visual impairment of 6/60 or worse despite correction |
| Minor impairment |
| • General cognitive index 70–79 |
| • Neurological score grade 1, 2, or 3 |
| • Sensory-neural hearing loss not requiring aids |
| • The presence of amblyopia (visual acuity of 6/18 or worse) |
| • Treatment for hydrocephalus |
| Normal |
| • General cognitive index ⩾80 |
| • Neurological score of 0 |
| • No sensory-neural hearing loss |
| • No amblyopia |
| • No hydrocephalus |