2027 ICD-10-CM Diagnosis Code R94.01Abnormal electroencephalogram [EEG]
ICD-10-CM Codes›R00–R99›R90-R94›R94
- Billable — Valid for Submission
- Not Chronic
R94.01 is a billable ICD-10-CM diagnosis code for abnormal electroencephalogram [EEG]. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 91 through 93. As a symptom code, it should not be used as a principal diagnosis once a related definitive diagnosis has been established. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Abnormal findings without diagnosis.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Alpha amplitude asymmetry
- Alpha coma type recording
- Alpha frequency asymmetry
- Asymmetric beta activity
- Asymmetric EEG
- Asymmetrical mu activity
- Beta coma type recording
- Bilateral periodic epileptiform discharges
- Burst suppression
- Café-au-lait macules with temporal dysrhythmia
- Continuous periodic complexes
- Dominant alpha activity
- Dominant beta activity
- Dominant delta activity
- Dominant EEG frequency - finding
- Dominant theta activity
- EEG abnormality with seizure
- EEG abnormality without seizure
- EEG artifact
- EEG artifact - patient movement
- EEG artifact - technical problems
- EEG pattern of uncertain significance
- EEG symmetry - finding
- Electrocerebral silence
- Electroencephalogram abnormal
- Excessive overbreathing response
- Focal continuous delta activity
- Focal continuous EEG abnormality
- Focal continuous theta activity
- Focal episodic delta activity
- Focal episodic EEG abnormality
- Focal episodic sharp waves
- Focal episodic spike wave
- Focal episodic spike wave with secondary generalization
- Focal episodic spikes
- Focal episodic theta activity
- Focal recruiting discharge
- Focal reduction of EEG activity
- Focal rolandic spikes
- Focal sharp waves
- Focal spikes
- Frontal intermittent rhythmic delta activity
- Generalized atypical spike wave
- Generalized continuous EEG abnormality
- Generalized EEG amplitude asymmetry
- Generalized EEG frequency asymmetry
- Generalized EEG pattern - finding
- Generalized epileptiform discharges
- Generalized episodic EEG abnormality
- Generalized intermittent delta activity
- Generalized intermittent theta activity
- Generalized multifocal spikes
- Generalized slow spike wave
- Generalized three per second spike wave
- Intermittent periodic complexes
- Isoelectric recording
- Light-induced EEG abnormality
- Loss of reactivity
- Low amplitude EEG tracing
- Low amplitude six per second spike wave
- Low frequency alpha activity
- Low frequency background activity
- Low frequency delta activity
- Low frequency theta activity
- Occipital intermittent rhythmic delta activity
- Periodic complexes
- Periodic lateralized epileptiform discharges
- Positive spikes
- Prolonged overbreathing response
- Reduction of alpha activity in left cerebral hemisphere
- Reduction of alpha activity in right cerebral hemisphere
- Rhythmic mid-temporal discharge
- Small sharp transients during sleep
- Sound-induced EEG abnormality
- Subclinical rhythmical EEG discharges in adults
- Temporal slowing
- Trace alternant EEG pattern
- Triphasic waves
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to R94.01: its own notes plus those printed at R94, block R90-R94, and Chapter 18. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- abnormal results of radionuclide [radioisotope] uptake studies
- abnormal results of scintigraphy
- nonspecific abnormal findings on diagnostic imaging by computerized axial tomography [CAT scan]
- nonspecific abnormal findings on diagnostic imaging by magnetic resonance imaging [MRI][NMR]
- nonspecific abnormal findings on diagnostic imaging by positron emission tomography [PET scan]
- nonspecific abnormal findings on diagnostic imaging by thermography
- nonspecific abnormal findings on diagnostic imaging by ultrasound [echogram]
- nonspecific abnormal findings on diagnostic imaging by X-ray examination
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- abnormal findings on antenatal screening of mother (O28.-)
- diagnostic abnormal findings classified elsewhere - see Alphabetical Index
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Notes
General instructions on how these codes are used.
- This chapter includes symptoms, signs, abnormal results of clinical or other investigative procedures, and ill-defined conditions regarding which no diagnosis classifiable elsewhere is recorded.
- Signs and symptoms that point rather definitely to a given diagnosis have been assigned to a category in other chapters of the classification. In general, categories in this chapter include the less well-defined conditions and symptoms that, without the necessary study of the case to establish a final diagnosis, point perhaps equally to two or more diseases or to two or more systems of the body. Practically all categories in the chapter could be designated 'not otherwise specified', 'unknown etiology' or 'transient'. The Alphabetical Index should be consulted to determine which symptoms and signs are to be allocated here and which to other chapters. The residual subcategories, numbered .8, are generally provided for other relevant symptoms that cannot be allocated elsewhere in the classification.
- The conditions and signs or symptoms included in categories R00-R94 consist of:
- (a) cases for which no more specific diagnosis can be made even after all the facts bearing on the case have been investigated;
- (b) signs or symptoms existing at the time of initial encounter that proved to be transient and whose causes could not be determined;
- (c) provisional diagnosis in a patient who failed to return for further investigation or care;
- (d) cases referred elsewhere for investigation or treatment before the diagnosis was made;
- (e) cases in which a more precise diagnosis was not available for any other reason;
- (f) certain symptoms, for which supplementary information is provided, that represent important problems in medical care in their own right.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Abnormal, abnormality, abnormalities See Also: Anomaly;
electroencephalogram [EEG] R94.01
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Convert R94.01 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About R94.01Overview
What is the ICD-10 code for abnormal electroencephalogram [EEG]?
The ICD-10-CM code for abnormal electroencephalogram [EEG] is R94.01 (sometimes written as R9401). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is R94.01 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report abnormal electroencephalogram [EEG] on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does R94.01 group to?
When abnormal electroencephalogram [EEG] is the principal diagnosis on an inpatient stay, it groups to MS-DRG 91, 92, 93, with relative weights from 0.7783 to 1.7050 depending on complications. Higher weights mean higher Medicare reimbursement.
Can R94.01 be a principal diagnosis?
Use it with care. This is a symptom code, so once a definitive diagnosis explaining the abnormal electroencephalogram [EEG] is established, that condition takes the principal position instead.
Can R94.01 be reported with a code from O28?
Not as a rule. The Excludes1 note at block R90-R94, which applies to R94.01, lists "abnormal findings on antenatal screening of mother (O28.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
