G40.811
BillableLennox-Gastaut syndrome, not intractable, with status epilepticus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G40.811 an HCC code?
Yes. G40.811 maps to Seizure Disorders and Convulsions under the CMS-HCC V28 risk adjustment model (and Seizure Disorders and Convulsions under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for G40.811
For G40.811 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G40.811 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G40.811 is the ICD-10-CM diagnosis code for lennox-gastaut syndrome, not intractable, with status epilepticus. Lennox-Gastaut syndrome, a severe childhood epilepsy with multiple seizure types that can be controlled with medication, currently experiencing a prolonged seizure state. G40.811 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering episodic and paroxysmal disorders (g40-g47).
Under the CMS-HCC V28 risk adjustment model, G40.811 maps to Seizure Disorders and Convulsions (HCC 201) with a community, non-dual, aged base RAF weight of 0.262. Under the older V24 model, G40.811 mapped to the same category but with a base RAF weight of 0.244 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Lennox-Gastaut is a specific, well-defined epilepsy syndrome; ensure diagnosis is confirmed before coding. Because G40.811 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G40.811 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Lennox-Gastaut is a specific, well-defined epilepsy syndrome; ensure diagnosis is confirmed before coding
- •Status epilepticus in this syndrome is particularly dangerous and requires emergency management
Clinical Significance
Lennox-Gastaut syndrome is a severe childhood-onset epilepsy characterized by multiple seizure types (tonic, atonic, atypical absence), slow spike-and-wave EEG pattern, and intellectual disability. Status epilepticus in LGS is particularly dangerous and may present as non-convulsive status. This syndrome carries significant lifelong morbidity and requires comprehensive multidisciplinary management.
Documentation Requirements
- ✓Confirmed diagnosis of Lennox-Gastaut syndrome by neurologist
- ✓Documentation of characteristic features: multiple seizure types, cognitive impairment, EEG findings
- ✓Active status epilepticus during the encounter
- ✓Statement that condition responds to medication (not intractable)
- ✓Current antiepileptic drug regimen
- ✓Emergency interventions for status epilepticus
Commonly Confused Codes
- •G40.812 — Lennox-Gastaut, not intractable, WITHOUT status epilepticus
- •G40.813 — Lennox-Gastaut, INTRACTABLE, with status epilepticus
- •G40.821 — Epileptic spasms with status epilepticus; LGS may evolve from infantile spasms but is a distinct diagnosis
- •G40.401 — Other generalized epilepsy with status epilepticus; use when LGS criteria are NOT met
- •G40.801 — Other epilepsy with status epilepticus; less specific than LGS