ICD-10 Code G40.0 – Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G40.0 – Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset
What it is
This code identifies idiopathic epilepsy with focal seizures that begin in one area of the brain. Use it when the record shows localized-onset seizures without a known structural, metabolic, or infectious cause.
Clinical signs
Typical findings include recurrent focal seizures, sometimes with sensory, motor, or autonomic features, and possible progression to impaired awareness or generalized activity. Clinical features vary; refer to documentation.
When to use this code
Use G40.0 when the provider documents idiopathic focal epilepsy or a focal seizure syndrome with localized onset. It fits cases where the epilepsy type is specified and no secondary cause is identified. Check documentation if the note only says “seizure” or “epilepsy” without localization.
Do not use for
Do not use this code for generalized epilepsy, symptomatic epilepsy, or seizures caused by another condition. Also avoid it when the record does not support an idiopathic focal diagnosis.
Coding tip
Confirm both the focal onset and idiopathic nature in the provider’s documentation before assigning G40.0.