2027 ICD-10-CM Diagnosis Code G13.1Other systemic atrophy primarily affecting central nervous system in neoplastic disease
ICD-10-CM Codes›G00–G99›G10-G14›G13
- Billable — Valid for Submission
- Chronic Condition
G13.1 is a billable ICD-10-CM diagnosis code for other systemic atrophy primarily affecting central nervous system in neoplastic disease. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 73 through 74. The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as paraneoplastic cerebellar degeneration. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Conditions due to neoplasm or the treatment of neoplasm and Other nervous system disorders (neither hereditary nor degenerative).
G13.1 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 75 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 75, ESRD (V21) category 75, ESRD (V24) category 75, and RxHCC Part D (V08) category 158 for payment year 2027.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for G13.1.
Medicare Risk Adjustment (HCC)Billing
G13.1 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Paraneoplastic cerebellar degeneration
- Secondary cerebellar degeneration
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to G13.1: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Paraneoplastic limbic encephalopathy
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Code First
The underlying condition named in the note is sequenced before this code.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Brain Diseases
Your brain is the control center of your body. It controls your thoughts, memory, speech, and movement. It regulates the function of many organs. It's part of your nervous system, which also includes your spinal cord and peripheral nerves. The nervous system sends signals between your brain and the rest of the body.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert G13.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About G13.1Overview
Is G13.1 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other systemic atrophy primarily affecting central nervous system in neoplastic disease on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does G13.1 group to?
On inpatient claims, other systemic atrophy primarily affecting central nervous system in neoplastic disease maps to MS-DRG 74, 73, with relative weights from 1.0172 to 1.5773 depending on complications. Higher weights mean higher Medicare reimbursement.
Can G13.1 be a principal diagnosis?
No. This is a manifestation code: other systemic atrophy primarily affecting central nervous system in neoplastic disease describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.
What is coded first with G13.1?
The Code First note reads: underlying neoplasm (C00-D49). When one of these applies, it is sequenced before G13.1.
What is the ICD-9 equivalent of G13.1?
Under the General Equivalence Mappings, other systemic atrophy primarily affecting central nervous system in neoplastic disease converts to ICD-9-CM 357.3 (neuropathy in malig dis). The mapping is approximate, so confirm the match fits the documentation.
Does G13.1 risk-adjust for Medicare Advantage payment?
Not for Medicare Advantage. G13.1 mapped to HCC 75 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 75 (Myasthenia Gravis/Myoneural Disorders and Guillain-Barre Syndrome/Inflammatory and Toxic Neuropathy), ESRD (V21) category 75 (Polyneuropathy), ESRD (V24) category 75 (Myasthenia Gravis/Myoneural Disorders and Guillain-Barre Syndrome/Inflammatory and Toxic Neuropathy), and RxHCC Part D (V08) category 158 (Inflammatory and Toxic Neuropathy).
