ICD-10-CM category G31
Other degenerative diseases of nervous system, not elsewhere classified: every G31 code with its CMS-HCC V28 status
G31, Other degenerative diseases of nervous system, not elsewhere classified, holds 17 codes in the FY2026 ICD-10-CM set: 14 billable codes and 3 header codes that need a further character. 7 of them maps to a CMS-HCC V28 payment category (HCC 127 and 200) for payment year 2026. The other 7 billable codes carry no V28 HCC and do not risk-adjust.
CMS-HCC V28 categories in G31 (2)
Coefficients are the code-level reference values from the CMS V28 factor file (community, non-dual, aged), not a member's score. Hierarchy, interactions, and enrollment segment decide what a documented condition contributes.
All 17 G31 codes (FY2026)
Descriptors are the FY2026 order-file text. Header codes need a further character and cannot be reported; open any billable code for its tabular notes, MEAT guidance, and mapping detail.
| Code | Description | FY2026 | CMS-HCC V28 |
|---|---|---|---|
| G31 | Other degenerative diseases of nervous system, not elsewhere classified | Header | Header code, not reportable |
| G31.0 | Frontotemporal dementia | Header | Header code, not reportable |
| G31.01 | Pick's disease | Billable | HCC 127 |
| G31.09 | Other frontotemporal neurocognitive disorder | Billable | HCC 127 |
| G31.1 | Senile degeneration of brain, not elsewhere classified | Billable | No V28 HCC |
| G31.2 | Degeneration of nervous system due to alcohol | Billable | No V28 HCC |
| G31.8 | Other specified degenerative diseases of nervous system | Header | Header code, not reportable |
| G31.80 | Leukodystrophy, unspecified | Billable | HCC 200 |
| G31.81 | Alpers disease | Billable | HCC 127 |
| G31.82 | Leigh's disease | Billable | HCC 127 |
| G31.83 | Neurocognitive disorder with Lewy bodies | Billable | HCC 127 |
| G31.84 | Mild cognitive impairment of uncertain or unknown etiology | Billable | No V28 HCC |
| G31.85 | Corticobasal degeneration | Billable | No V28 HCC |
| G31.86 | Alexander disease | Billable | HCC 127 |
| G31.87 | Primary progressive apraxia of speech | Billable | No V28 HCC |
| G31.89 | Other specified degenerative diseases of nervous system | Billable | No V28 HCC |
| G31.9 | Degenerative disease of nervous system, unspecified | Billable | No V28 HCC |
Documentation guides for G31
Frequently asked questions
How many G31 codes are there?
The G31 category (Other degenerative diseases of nervous system, not elsewhere classified) has 17 codes in the FY2026 ICD-10-CM order file: 14 billable and 3 header codes, counting the category itself. Only a billable code can be reported on a claim.
Which G31 codes map to an HCC under CMS-HCC V28?
7 billable codes in G31 map to HCC 127 and 200 in the CMS-HCC V28 model for payment year 2026. HCC 127 (Dementia, Mild or Unspecified) carries the most, with 6 codes. The 7 billable codes without a V28 category are marked "No V28 HCC" in the table.
Which G31 codes are not billable?
G31 itself and 2 subcategory codes are header codes that need a further character before they can be reported: G31.0 (Frontotemporal dementia), G31.8 (Other specified degenerative diseases of nervous system). Each one is listed in the table with the billable codes beneath it.
Source: FY2026 ICD-10-CM order file (FY 2026 Apr update) for codes, billability, and descriptors; CMS-HCC V28 PY2026 final ICD-10-CM mappings and relative factors for payment status. Table generated 2026-09-10.