Epilepsy and Seizures ICD-10-CM codes

Category G40 uses a consistent pattern: the fourth character is the epilepsy type (0 to 2 focal, 3 and 4 generalized, 5 related to external causes, 8 other, 9 unspecified, A absence, B juvenile myoclonic, C Lafora), the fifth character is intractable (1) or not intractable (0), and the sixth character is with (1) or without (9) status epilepticus. G40.909 (epilepsy, unspecified, not intractable, without status epilepticus) is the default for epilepsy or seizure disorder NOS.

Intractable has no clinical threshold in the code set; assign the intractable codes when the provider uses that word or one of the listed equivalents: pharmacoresistant, pharmacologically resistant, treatment resistant, refractory, or poorly controlled. A patient with breakthrough seizures is not automatically intractable.

A single seizure or a seizure that has not been diagnosed as epilepsy is R56.9 (unspecified convulsions), not G40. Febrile seizures are R56.00 (simple) or R56.01 (complex), and post-traumatic seizures are R56.1. Seizure disorder and recurrent seizures NOS both index to G40.909. Psychogenic non-epileptic seizures are F44.5 (conversion disorder with seizures).

Status epilepticus is coded within G40 by the sixth character, never as a separate code. When the record says seizures in a patient with known epilepsy, code the epilepsy (G40.-) rather than R56.9, and add long-term drug therapy codes when documented.