FY2027 ICD-10-CM reference
G40.813: Lennox-Gastaut syndrome, intractable, with status epilepticus
By the HCC Buddy Coding Team
The official ICD-10-CM descriptor is Lennox-Gastaut syndrome, intractable, with status epilepticus. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Billable code. Verified against the official FY2027 order file.
FY2027 Tabular instructions
Instructions below include applicable chapter, section and parent-code notes. Each note identifies where it appears in the official source.
Excludes2
certain conditions originating in the perinatal period (P04-P96)
Source: G00-G99 (chapter, inherited).
Excludes2
certain infectious and parasitic diseases (A00-B99)
Source: G00-G99 (chapter, inherited).
Excludes2
complications of pregnancy, childbirth and the puerperium (O00-O9A)
Source: G00-G99 (chapter, inherited).
Excludes2
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
Source: G00-G99 (chapter, inherited).
Excludes2
endocrine, nutritional and metabolic diseases (E00-E88)
Source: G00-G99 (chapter, inherited).
Excludes2
injury, poisoning and certain other consequences of external causes (S00-T88)
Source: G00-G99 (chapter, inherited).
Excludes2
neoplasms (C00-D49)
Source: G00-G99 (chapter, inherited).
Excludes2
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: G00-G99 (chapter, inherited).
Instructional note
the following terms are to be considered equivalent to intractable: pharmacoresistant (pharmacologically resistant), treatment resistant, refractory (medically) and poorly controlled
Source: G40 (category, inherited).
Excludes1
conversion disorder with seizures (F44.5)
Source: G40 (category, inherited).
Excludes1
convulsions NOS (R56.9)
Source: G40 (category, inherited).
Excludes1
post traumatic seizures (R56.1)
Source: G40 (category, inherited).
Excludes1
seizure (convulsive) NOS (R56.9)
Source: G40 (category, inherited).
Excludes1
seizure of newborn (P90)
Source: G40 (category, inherited).
Excludes2
hippocampal sclerosis (G93.81)
Source: G40 (category, inherited).
Excludes2
mesial temporal sclerosis (G93.81)
Source: G40 (category, inherited).
Excludes2
temporal sclerosis (G93.81)
Source: G40 (category, inherited).
Excludes2
Todd's paralysis (G83.84)
Source: G40 (category, inherited).
Instructional note
Epilepsies and epileptic syndromes undetermined as to whether they are focal or generalized
Source: G40.8 (self, inherited).
Instructional note
Landau-Kleffner syndrome
Source: G40.8 (self, inherited).
Compare the FY2027 additions, removals and billable-status changes
What does G40.813 mean in FY2027?
The official ICD-10-CM descriptor is Lennox-Gastaut syndrome, intractable, with status epilepticus. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Is G40.813 billable in FY2027?
The FY2027 order file marks G40.813 as billable. Check the complete Tabular instructions and documentation before assigning it.
Does G40.813 map to an HCC?
In the CMS 2027 Initial ICD-10-CM Mappings (payment year 2027, 2026 dates of service), G40.813 maps to CMS-HCC V28 HCC 201 (Seizure Disorders and Convulsions). For 2027 dates of service, CMS has not yet published the payment year 2028 mappings. ESRD, RxHCC, PACE and HHS-HCC mappings are still pending verification for FY2027.
Source: CMS FY2027 ICD-10-CM order file. Read the FY2027 Official Guidelines.
Review the FY2026 April edition