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ICD-10-PCS 2027 procedure code

4A1004GMonitoring of Central Nervous Electrical Activity, Intraoperative, Open Approach

✓ Valid for 2027

Short description: Monitoring of CNS Electr Activity, Intraop, Open Approach

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

About 4A1004G

4A1004G is the ICD-10-PCS code for a monitoring procedure on the central nervous using an open approach with electrical activity (qualifier: intraoperative). In ICD-10-PCS, monitoring means determining the level of a physiological or physical function repetitively over a period of time.

In plain terms, this corresponds to intra-operative neurophysiologic monitoring, the ICD-9-CM procedure title it maps to (00.94).

For a different body part, codes include 4A1104G (peripheral nervous).

The same procedure with a different approach is coded 4A1034G (percutaneous), 4A1074G (via natural or artificial opening), 4A1084G (via natural or artificial opening endoscopic) and 4A10X4G (external).

It doesn't appear in the MS-DRG procedure index, so on its own it doesn't change the DRG assignment.

It has been valid since ICD-10-PCS took effect on October 1, 2015.

What each character means

1. Section
4Measurement and Monitoring
2. Body System
APhysiological Systems
3. Operation
1Monitoring

Determining the level of a physiological or physical function repetitively over a period of time

4. Body System
0Central Nervous
5. Approach
0Open

Cutting through the skin or mucous membrane and any other body layers necessary to expose the site of the procedure

6. Function / Device
4Electrical Activity
7. Qualifier
GIntraoperative

Other versions of this procedure

Different body system

Different qualifier

ICD-9-CM equivalent

Converter →
  • 00.94Intra-operative neurophysiologic monitoringapproximate

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 4A1004G

Is 4A1004G a valid ICD-10-PCS code for 2027?

Yes. 4A1004G is valid for inpatient procedures from October 1, 2026 through September 30, 2027.

What is the ICD-9 procedure code for 4A1004G?

The CMS GEMs map 4A1004G to ICD-9-CM 00.94 (Intra-operative neurophysiologic monitoring).