ICD-10 Code G40.81 – Lennox-Gastaut syndrome (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G40.81 – Lennox-Gastaut syndrome
What it is
G40.81 identifies Lennox-Gastaut syndrome, a severe childhood-onset epileptic disorder. It is used when the diagnosis is documented and the seizure pattern fits this syndrome.
Clinical signs
Common features include multiple seizure types, developmental impairment, and characteristic EEG abnormalities. Clinical features vary; refer to documentation.
When to use this code
Use G40.81 when the provider documents Lennox-Gastaut syndrome as the confirmed diagnosis. It may be appropriate in neurology, inpatient, or outpatient records when the syndrome is the reason for evaluation or ongoing management.
Code it only when the record supports this specific epileptic syndrome, not just generalized seizures or developmental delay. If the documentation is unclear, check documentation before assigning the code.
Do not use for
Do not use this code for other seizure disorders, isolated seizures, or epilepsy without a documented Lennox-Gastaut syndrome diagnosis. Do not assume the syndrome from anticonvulsant use alone.
Coding tip
Verify the exact syndrome name in the assessment or problem list before coding, and query if the record only says “epilepsy” or “seizure disorder.”