G40.814
BillableLennox-Gastaut syndrome, intractable, without status epilepticus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G40.814 an HCC code?
Yes. G40.814 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 G40.814
For G40.814 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 G40.814 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G40.814 is the ICD-10-CM diagnosis code for lennox-gastaut syndrome, intractable, without status epilepticus. Lennox-Gastaut syndrome, a severe childhood epilepsy with multiple seizure types that cannot be adequately controlled with medication, not currently in a prolonged seizure state. G40.814 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, G40.814 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, G40.814 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.
Document failed antiepileptic drug trials and consider noting if patient is evaluated for surgical options. Because G40.814 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 G40.814 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document failed antiepileptic drug trials and consider noting if patient is evaluated for surgical options
- •This intractable form often requires multidisciplinary management including neurology and developmental pediatrics
Clinical Significance
Lennox-Gastaut syndrome, intractable, without status epilepticus is the most common clinical presentation of LGS — a severe epileptic encephalopathy that is typically drug-resistant. These patients have ongoing uncontrolled seizures despite multiple medication trials, significant cognitive impairment, and may be candidates for palliative epilepsy surgery, corpus callosotomy, or VNS therapy.
Documentation Requirements
- ✓Confirmed Lennox-Gastaut syndrome diagnosis with characteristic features
- ✓Documentation of intractability with list of failed antiepileptic drugs
- ✓Absence of status epilepticus at the encounter
- ✓Current seizure types and frequency
- ✓Cognitive and developmental status
- ✓Treatment plan including advanced therapy considerations
- ✓Multidisciplinary care team involvement
Commonly Confused Codes
- •G40.812 — LGS, NOT intractable; rare presentation where seizures are controlled
- •G40.813 — LGS, intractable, WITH status epilepticus
- •G40.824 — Epileptic spasms, intractable; distinct from LGS even though LGS may evolve from infantile spasms
- •G40.834 — Dravet syndrome, intractable; different epileptic encephalopathy
- •G40.804 — Other epilepsy, intractable; less specific when LGS is confirmed