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ICD-10-CM 2027 diagnosis code

R94.01Abnormal electroencephalogram [EEG]

✓ Billable / specific

R94.01 is a valid, billable ICD-10-CM code for abnormal electroencephalogram [eeg]. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About R94.01

R94.01 is the ICD-10-CM diagnosis code for abnormal electroencephalogram [EEG]. It belongs to category R94 (abnormal results of function studies), block R90-R94 (abnormal findings on diagnostic imaging and in function studies, without diagnosis) and chapter 18 (symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within R94.0 (abnormal results of function studies of central nervous system), R94.01 is specifically for abnormal electroencephalogram [EEG]. Related codes cover brain scan (R94.02) and results of other function studies of central nervous system (R94.09).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 091 (Other Disorders of Nervous System with MCC, relative weight 1.7046), DRG 092 (Other Disorders of Nervous System with CC, relative weight 1.0239) and DRG 093 (Other Disorders of Nervous System without CC/MCC, relative weight 0.7783), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 794.02 (nonspecific abnormal electroencephalogram [EEG]).

Notes that apply from higher levels

Instructions written at a parent level also apply to R94.01.

› From R94 Abnormal results of function studies
Includes
  • abnormal results of radionuclide [radioisotope] uptake studies
  • abnormal results of scintigraphy

Broader instructions also apply from R90-R94 Abnormal findings on diagnostic imaging and in function studies, without diagnosis and Chapter 18: Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified.

Alphabetic index entries

1 entries

Terms in the official ICD-10-CM index that lead to R94.01.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 794.02Nonspecific abnormal electroencephalogram [EEG]exact

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about R94.01

Is R94.01 billable?

Yes. R94.01 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can R94.01 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict R94.01 as a principal diagnosis.

Is R94.01 a CC or MCC?

No. R94.01 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does R94.01 group to?

R94.01 is used in the MS-DRG v44.0 logic for MS-DRG 091 (Other Disorders of Nervous System with MCC), MS-DRG 092 (Other Disorders of Nervous System with CC) and MS-DRG 093 (Other Disorders of Nervous System without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for R94.01?

The CMS General Equivalence Mappings map R94.01 to ICD-9-CM 794.02.