ICD-10 Code G40.21 – Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G40.21 – Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable
What it is
This code identifies focal symptomatic epilepsy with complex partial seizures that are difficult to control. Use it when the record documents persistent seizures despite treatment, and the cause is a known brain lesion or other symptomatic origin.
Clinical signs
Clinical features vary; refer to documentation. Complex partial seizures typically involve impaired awareness, staring, automatisms, or brief confusion, and may arise from a focal neurologic source.
When to use this code
Use G40.21 when the provider documents focal symptomatic epilepsy with complex partial seizures and states that it is intractable or refractory. It may also apply when repeated seizures continue despite appropriate therapy, as documented in the chart. Check that the seizure type and intractable status are both clearly recorded.
Do not use for
Do not use this code for generalized epilepsy, seizure disorders without epilepsy, or focal epilepsy without documented intractability. If the seizure type or control status is unclear, check documentation.
Coding tip
Confirm both the focal symptomatic epilepsy diagnosis and the phrase “intractable” before assigning G40.21.