ICD-10 Code G31.83 – Neurocognitive disorder with Lewy bodies (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G31.83 – Neurocognitive disorder with Lewy bodies
What it is
G31.83 identifies a neurocognitive disorder caused by Lewy body disease. It covers progressive cognitive decline linked to abnormal alpha-synuclein deposits in the brain.
Clinical signs
Typical findings include fluctuating attention, visual hallucinations, parkinsonian motor features, and REM sleep behavior disorder. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents Lewy body dementia or neurocognitive disorder with Lewy bodies. It is also appropriate when the record clearly links dementia symptoms to Lewy body disease. If the diagnosis is uncertain, check documentation.
Do not use for
Do not use it for Alzheimer disease, Parkinson disease without documented dementia, or nonspecific cognitive decline. Do not code from symptoms alone when Lewy body disease is not documented.
Coding tip
Code G31.83 only when the clinician explicitly documents Lewy body involvement; otherwise, confirm the diagnosis in the chart.