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Diagnostic Coding for Epilepsy

Williams, Korwyn; Nuwer, Marc, R.; Buchhalter, Jeffrey, R.

CONTINUUM: Lifelong Learning in Neurology: February 2016 - Volume 22 - Issue 1, Epilepsy - p 270–280
doi: 10.1212/CON.0000000000000281
Practice Issues

Accurate coding is an important function of neurologic practice. This contribution to Continuum is part of an ongoing series that presents helpful coding information along with examples related to the issue topic. Tips for diagnosis coding, Evaluation and Management coding, procedure coding, or a combination are presented, depending on which is most applicable to the subject area of the issue.

Address correspondence to Dr Korwyn Williams, Phoenix Children’s Hospital, Division of Neurology, 1919 East Thomas Rd, Phoenix, AZ 85016,

Relationship Disclosure: Dr Williams reports no disclosure. Dr Nuwer has received personal compensation for speaking engagements from the American Clinical Neurophysiology Society and the Virginia Commonwealth University, serves as a consultant for CortiCare, Inc, and has provided expert legal testimony. Dr Nuwer receives royalties from Cambridge University Press and research support from the National Institutes of Health and the US Army. Dr Buchhalter has served as a consultant for Eisai Co, Ltd, and Upsher-Smith Laboratories, Inc, and receives research support from the Alberta Children’s Hospital Foundation.

Unlabeled Use of Products/Investigational Use Disclosure: Drs Williams, Nuwer, and Buchhalter report no disclosures.

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Coding is an unavoidable component of patient encounters. Use of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM)1 became a statutory requirement for Medicare reimbursement in 1989. The International Classification of Diseases, Tenth Revision (ICD-10)2 was published in the early 1990s by the World Health Organization (WHO), and ICD-10 coded data have been adopted by over 100 countries in some form. While ICD-10 is currently used for mortality reporting in the United States, by early 2016 it will also incorporate morbidity reporting. The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM)3 was expected to have been adopted by October 1, 2014, but the Protecting Access to Medicare Act of 2014 prohibited adoption of this US-specific version before October 1, 2015.4

This new classification scheme is beneficial in several ways. ICD-10-CM allows for more succinct coding of disease severity (eg, the ability to code for “medically intractable,” or “… with status epilepticus”), providing the type of severity adjustment data needed to justify more appropriate reimbursements for the work that neurologists perform. Modern advanced health care reimbursement systems use these diagnoses to set relative acuity factors, which are one basis for payments to hospitals and physicians.

ICD-10-CM also provides benefits at the public health level: greater specificity in diagnosis, etiology, and severity of disease and disease outcome; comparison of US morbidity to international reports; and identification of fraud and abuse. With more precise epidemiologic data, policy makers will be better informed to allocate health care resources more effectively. On a more practical level, ICD-10-CM greatly expands the capacity of disease description with a fivefold increase in the number of diagnosis codes as the available codes in the International Classification of Diseases, Ninth Revision (ICD-9) were full and new disorders have been identified since ICD-9 was published in 1977 (eg, Dravet syndrome).5

Medical knowledge continues to evolve and expand at a rapid pace. ICD-10 is designed to be a robust framework to encompass the current complexity and yet still be able to incorporate currently unknown disorders that may be identified in the future. This article guides readers through the coding for epilepsy using ICD-10. The good news is that the taxonomy is not much different between the old and new systems.6

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While ICD-9-CM codes consist of five placeholders (the first is alphanumeric and the rest are all numerals), ICD-10-CM codes have three to seven characters (the first is a letter, the second and third are numeric, and the rest are alphanumeric). The first three characters specify the category; the next three specify etiology, severity, laterality, or other clinical detail. For neurologists, the last character is likely to be used only in the context of injuries, poisonings, and other conditions with external causes and not epilepsy; therefore, it will not be discussed further in this article.7 With ICD-10-CM, the epilepsy code is based on etiology, pathophysiology, determination of intractability or not, and whether the patient is in status epilepticus or not. However, one of the challenges with the transition to ICD-10-CM is that the most recent definitions and classifications promulgated by the International League Against Epilepsy (ILAE) do not always easily harmonize with ICD-10-CM.8,9

Under ICD-9, a first-time unprovoked seizure would be classified as 780.39, Other convulsions. However, this same code could be used for seizures associated with an external cause (eg, hypocalcemia, posttraumatic brain injury) or even nonepileptic events. Under ICD-10-CM, a first-time unprovoked seizure is coded as R56.9, Unspecified convulsions (Coding Table 1). However, seizures due to external causes are coded as G40.5, Epileptic seizures related to external causes. A conversion disorder with seizurelike symptoms is now coded as F44.5, Conversion disorder with seizures or convulsions, separate from the conversion disorder code for a symptom such as astasia-abasia. These are good examples of the increased granularity of ICD-10-CM compared to ICD-9-CM. ICD-10-CM no longer combines etiologically different seizures, yet the underlying conceptualization has not changed.

Coding Table 1 International Classification of Diseases, Tenth Revision, Clinical Modification Epilepsy and Seizure-Related Codes

Coding Table 1 International Classification of Diseases, Tenth Revision, Clinical Modification Epilepsy and Seizure-Related Codes

Epilepsy, defined by the ILAE as recurrent unprovoked seizures more than 24 hours apart or a first-time unprovoked seizure with a high likelihood of recurrence, is subdivided into several categories in ICD-10-CM (Coding Table 1). A tabular list of the codes can also be found at the Centers for Disease Control and Prevention website: Again, the conceptualization remains essentially the same between ICD-9-CM and ICD-10-CM: partial onset versus generalized onset, simple versus complex, symptomatic versus idiopathic, intractable versus well controlled. ICD-10-CM now specifically incorporates whether the patient is in status epilepticus. With this information in hand, coding is straightforward.

To establish a partial-onset epilepsy, focal onset of the seizure, lateralizing clinical features (eg, unilateral blinking) or focal EEG or neuroradiographic findings should be documented. Absent a history of focality and with the presence of a history consistent with generalized seizures (eg, absence, myoclonic, atonic, tonic, clonic, or tonic-clonic), the documentation would be consistent with a generalized epilepsy.

To establish a complex versus simple partial classification, documentation of an alteration in awareness during the seizure should be explicit. If awareness is preserved during the seizure, then the epilepsy would be classified as a simple partial seizure.

If an etiologic basis exists for the epilepsy (eg, stroke, dementia, chromosomal anomaly, central nervous system lymphoma, mesial temporal sclerosis) or the neurologic examination demonstrates focal findings, then the epilepsy would be described as “symptomatic.” Otherwise, under the ICD-10-CM framework it would be coded as “idiopathic.” Under certain classification schemes, idiopathic implies an underlying genetic epilepsy, but in the context of ICD-10-CM, “idiopathic” can be thought of as “not symptomatic.” One caveat to keep in mind is that with better understanding of the genetic basis of the epilepsy syndromes (eg, juvenile myoclonic epilepsy), gene mutations may be identified for these syndromes. These would not be classified under symptomatic epilepsies, but rather continue to be classified under the more appropriate epilepsy syndromes (eg, G40.B, Juvenile myoclonic epilepsy [impulsive petit mal]). (Bear in mind that ICD-10 was released in the 1990s and is not consistent with the most recent classification of epilepsy by the ILAE and that archaic terms are included in ICD-10.)3,5

For the age-dependent genetic epilepsies, such as benign neonatal convulsions, myoclonic epilepsy in infancy, myoclonic astatic epilepsy, and grand mal seizures upon awakening, code families G40.0-, Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, or G40.4-, Other generalized epilepsy and epileptic syndromes, would be used, depending on whether they are focal or generalized in onset, respectively. It is important to recall that absence epilepsy and juvenile myoclonic epilepsy have their own unique codes.

The code G40.8, Other epilepsy and recurrent seizures, includes “epilepsy and epileptic syndromes undetermined as to whether they are focal or generalized” in onset. Landau-Kleffner syndrome is specifically mentioned under this heading. Lennox-Gastaut syndrome and epileptic (infantile) spasms are also given specific subheadings in this category (G40.81- and G40.82-, respectively).

The codes under G40.9, Epilepsy, unspecified, should only be used infrequently when sufficient information is lacking for more specific coding. The guiding principle in coding is that each encounter should be coded to the highest level of certainty.

Other seizures that do not fulfill a diagnosis of epilepsy are commonly seen in general practice but retain the same classification, only the codes used are different. For example, in pediatrics, the commonly encountered febrile seizures retain the same classifications: R56.00, Simple febrile convulsions, and R56.01, Complex febrile convulsions. Neonatal convulsions maintain their unique code as well: P90, Convulsions of newborn.

With the information gathered in the epilepsy encounter, coding is straightforward. The first four characters are the fundamental descriptors for epilepsy in ICD-10-CM. The fifth placeholder usually signifies intractability (ie, failure of two appropriate anticonvulsants at high doses) with either “0” (not intractable) or “1” (intractable). The sixth placeholder usually signifies either active status epilepticus with “9” or not being in status epilepticus with “1.”

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Consider stepwise coding for an epilepsy encounter for a patient with an epilepsy characterized by complex partial seizures and an MRI demonstrating mesial temporal sclerosis (G40.2-), who continues to seize despite adequate trials with oxcarbazepine and lamotrigine (“intractable”, G40.21-), and who presents in status epilepticus (G40.211).

Similarly, a 16-year-old patient with recent onset of generalized tonic-clonic seizures provoked by flashing lights could fall under several headings (G40.3-, Generalized idiopathic epilepsy and epileptic syndromes; G40.A-, Absence epileptic syndrome; G40.B-, Juvenile myoclonic epilepsy [impulsive petit mal]; G40.4-, Other generalized epilepsy and epileptic syndromes; G40.9-, Epilepsy, unspecified); however, if further history elicits a history of myoclonic seizures but no absence seizures, then the appropriate diagnosis would be G40.B, Juvenile myoclonic epilepsy [impulsive petit mal]. If the seizures are well controlled with medications and the patient is not in status epilepticus, the final code would be G40.B09, Juvenile myoclonic epilepsy, not intractable, without status epilepticus.

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The world has moved on from ICD-9, and the United States is moving to catch up. The transition to ICD-10-CM is not without its challenges, but tools exist to assist with the transition. In the long term, ICD-10-CM will be of benefit from a public health perspective, but it will also allow for more accurate coding of disease and disease severity, which will demonstrate the type of effort put forth by neurologists. This type of information can be used to inform policy makers’ decision making regarding reimbursements for the work performed by neurologists.

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1. Centers for Disease Control and Prevention. International classification of diseases, ninth revision, clinical modification (ICD-9-CM). /nchs/icd/icd9cm.htm. Updated June 18, 2013. Accessed December 22, 2015.
2. The ICD-10 classification of mental and behavioural disorders: clinical descriptions and diagnostic guidelines. Geneva, Switzerland: World Health Organization, 1992.
3. Centers for Disease Control and Prevention. International classification of diseases, tenth revision, clinical modification (ICD-10-CM). Updated October 29, 2015. Accessed December 22, 2015.
4. Bergen DC, Beghi E, Medina MT. Revising the ICD-10 codes for epilepsy and seizures. Epilepsia 2012; 53(suppl 2): 3–5. doi:10.1111/j.1528-1167.2012.03550.x.
5. Centers for Disease Control and Prevention. International Classification of Diseases, (ICD-10-CM/PCS) Transition. Updated November 5, 2013. Accessed December 9, 2015.
6. World Health Organization. ICD-10 Version: 2015. Accessed December 9, 2015.
7. American Medical Association. Preparing for the ICD-10 code set: October 1, 2014 compliance date. Accessed December 9, 2015.
8. Fisher RS, Acevedo C, Arzimanoglou A, et al. ILAE official report: a practical clinical definition of epilepsy. Epilepsia 2014; 55(4): 475–482. doi:10.1111/epi.12550.
9. Jette N, Beghi E, Hesdorffer D, et al. ICD coding for epilepsy: past, present, and future–a report by the International League Against Epilepsy Task Force on ICD codes in epilepsy. Epilepsia 2015; 6(3): 348–355. doi:10.1111/epi.12895.
© 2016 American Academy of Neurology