| G31 | Other degenerative diseases of nervous system, not elsewhere classified | NON-BILLABLE CODE |
| G31.0 | Frontotemporal dementia | NON-BILLABLE CODE |
| G31.01 | Pick's disease | BILLABLE CODE |
| G31.09 | Other frontotemporal neurocognitive disorder | BILLABLE CODE |
| G31.1 | Senile degeneration of brain, not elsewhere classified | BILLABLE CODE |
| G31.2 | Degeneration of nervous system due to alcohol | BILLABLE CODE |
| G31.8 | Other specified degenerative diseases of nervous system | NON-BILLABLE CODE |
| G31.80 | Leukodystrophy, unspecified | BILLABLE CODE |
| G31.81 | Alpers disease | BILLABLE CODE |
| G31.82 | Leigh's disease | BILLABLE CODE |
| G31.84 | Mild cognitive impairment of uncertain or unknown etiology | BILLABLE CODE |
| G31.85 | Corticobasal degeneration | BILLABLE CODE |
| G31.86 | Alexander disease | BILLABLE CODE |
| G31.89 | Other specified degenerative diseases of nervous system | BILLABLE CODE |
| G31.9 | Degenerative disease of nervous system, unspecified | BILLABLE CODE |
