ICD-10 Code G31.9 – Degenerative disease of nervous system, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G31.9 – Degenerative disease of nervous system, unspecified
What it is
G31.9 identifies a degenerative disorder of the nervous system when the record does not specify the exact disease. Use it for a documented neurodegenerative process, but not for a more defined diagnosis.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings may include progressive neurologic decline, cognitive or motor impairment, or other evidence of nervous system degeneration.
When to use this code
Use this code when the provider documents degenerative disease of the nervous system and gives no further detail. It also fits when the note confirms a degenerative neurologic condition but the exact type is unavailable or not stated. Check documentation before defaulting to an unspecified code.
Do not use for
Do not use G31.9 when the chart names a specific degenerative neurologic disorder, such as a coded dementia or other defined condition. Also avoid it if the record only describes symptoms without a documented degenerative diagnosis.
Coding tip
Query for the exact neurologic diagnosis whenever possible, because a more specific code usually replaces G31.9.