ICD-10 Code G13 – Systemic atrophies primarily affecting central nervous system in diseases classified elsewhere (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G13 – Systemic atrophies primarily affecting central nervous system in diseases classified elsewhere
What it is
G13 identifies systemic atrophies that mainly affect the central nervous system when the cause is another disease classified elsewhere. Use it when the neurologic degeneration is documented as secondary, not primary.
Clinical signs
Clinical features vary; refer to documentation. Commonly, records describe progressive neurologic decline, gait or coordination problems, and other signs of central nervous system involvement linked to the underlying disorder.
When to use this code
Use G13 when the provider states a systemic atrophy of the central nervous system and links it to another condition. This code is appropriate when the chart supports a secondary neurologic degeneration rather than a standalone disease. Confirm the causal condition and code it separately when instructed by the record.
Do not use for
Do not use G13 for primary degenerative neurologic diseases without an underlying cause documented elsewhere. If the note does not clearly link the atrophy to another disease, check documentation.
Coding tip
Always code the underlying condition first when the record identifies it, and verify that the neurologic atrophy is explicitly documented as secondary.