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ICD-10-PCS 2027 procedure code

4A00X4ZMeasurement of Central Nervous Electrical Activity, External Approach

✓ Valid for 2027

Short description: Measurement of CNS Electr Activity, Extern 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 4A00X4Z

4A00X4Z is the ICD-10-PCS code for a measurement procedure on the central nervous using an external approach with electrical activity. In ICD-10-PCS, measurement means determining the level of a physiological or physical function at a point in time.

In plain terms, this corresponds to electroencephalogram, the ICD-9-CM procedure title it maps to (89.14).

For a different body part, codes include 4A01X4Z (peripheral nervous), 4A02X4Z (cardiac), 4A0HX4Z (products of conception, cardiac) and 4A0JX4Z (products of conception, nervous).

The same procedure with a different approach is coded 4A0004Z (open), 4A0034Z (percutaneous), 4A0074Z (via natural or artificial opening) and 4A0084Z (via natural or artificial opening endoscopic).

With a different device, use 4A00X2Z (conductivity).

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
0Measurement

Determining the level of a physiological or physical function at a point in time

4. Body System
0Central Nervous
5. Approach
XExternal

Procedures performed directly on the skin or mucous membrane and procedures performed indirectly by the application of external force through the skin or mucous membrane

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

Other versions of this procedure

Different function / device

ICD-9-CM equivalent

Converter →
  • 89.14Electroencephalogramapproximate

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 4A00X4Z

Is 4A00X4Z a valid ICD-10-PCS code for 2027?

Yes. 4A00X4Z is valid for inpatient procedures from October 1, 2026 through September 30, 2027.

What is the ICD-9 procedure code for 4A00X4Z?

The CMS GEMs map 4A00X4Z to ICD-9-CM 89.14 (Electroencephalogram).