| G10 | Huntington's disease |
| G11 | Hereditary ataxia |
| G11.0 | Congenital nonprogressive ataxia |
| G11.1 | Early-onset cerebellar ataxia |
| G11.2 | Late-onset cerebellar ataxia |
| G11.3 | Cerebellar ataxia with defective DNA repair |
| G11.4 | Hereditary spastic paraplegia |
| G11.8 | Other hereditary ataxias |
| G11.9 | Hereditary ataxia, unspecified |
| G12 | Spinal muscular atrophy and related syndromes |
| G12.0 | Infantile spinal muscular atrophy, type I [Werdnig-Hoffman] |
| G12.1 | Other inherited spinal muscular atrophy |
| G12.2 | Motor neuron disease |
| G12.20 | Motor neuron disease, unspecified |
| G12.21 | Amyotrophic lateral sclerosis |
| G12.22 | Progressive bulbar palsy |
| G12.29 | Other motor neuron disease |
| G12.8 | Other spinal muscular atrophies and related syndromes |
| G12.9 | Spinal muscular atrophy, unspecified |
| G13 | Systemic atrophies primarily affecting central nervous system in diseases classified elsewhere |
| G13.0 | Paraneoplastic neuromyopathy and neuropathy |
| G13.1 | Other systemic atrophy primarily affecting central nervous system in neoplastic disease |
| G13.2 | Systemic atrophy primarily affecting the central nervous system in myxedema |
| G13.8 | Systemic atrophy primarily affecting central nervous system in other diseases classified elsewhere |
| G14 | Postpolio syndrome |