Total ASM classes

Three or more total antiseizure medication (ASM) classes (including rescue therapies; eg, benzodiazepine, see appendix pp 2–3).

Simultaneous ASM classes

Two or more ASM classes where each ASM is prescribed at least one additional time after an initial overlapping period.

Status epilepticus

Any International Statistical Classification of Diseases (ICD) codes for status epilepticus after initial seizure (ICD-944: 345.2, 345.3, and 345.7; ICD-1045: G40.001, G40.011, G40.101, G40.111, G40.201, G40.211, G40.501, G40.801, G40.803, G40.901, G40.911, and G41).

Inpatient admissions for seizures

Inpatient admission where epilepsy is listed as primary or admitting billing code (ICD-9 code 345.** or ICD-10 code G40.*; eg, excluding convulsions ICD9–780** and ICD10-R56*).

Referrals to neurology or neurology notes

Four or more consult orders or neurology notes, or both, during the course of a visit where epilepsy is listed as a billing code (required to occur on unique days, at least 1 week apart).

Epilepsy-related procedure orders

Any of the following procedures during a visit with epilepsy billing codes (at least 1 week after an initial seizure-like event): electroencephalogram, brain MRI, head CT, fMRI, FDG-PET, or surgical treatment (eg, resective epilepsy surgery); the order must occur in an encounter with an epilepsy ICD code and the patient must have at least one more epilepsy ICD code more than 1 week after the procedure.

Distinct days with epilepsy ICD billing codes

More than 4 distinct days (each at least 1 week apart) with epilepsy ICD codes (ICD-9 code 345.** or ICD-10 code G40.*).

Patients will be considered to have had additional seizures if they match any of the above criteria in the 2 years after an initial seizure-like event.