Skip to content
Dx

ICD-10-CM 2027 diagnosis code

Q04.5Megalencephaly

✓ Billable / specificPOA exemptCC — complication/comorbidity

Q04.5 is a valid, billable ICD-10-CM code for megalencephaly. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Megalencephaly, ICD-10 code for Hemimegalencephaly.

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 Q04.5

Q04.5 is the ICD-10-CM diagnosis code for Megalencephaly. It belongs to category Q04 (other congenital malformations of brain), block Q00-Q07 (congenital malformations of the nervous system) and chapter 17 (congenital malformations, deformations, chromosomal abnormalities, and genetic disorders). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within Q04 (other congenital malformations of brain), Q04.5 is specifically for Megalencephaly. Related codes cover congenital malformations of corpus callosum (Q04.0), Arhinencephaly (Q04.1), holoprosencephaly (Q04.2), other reduction deformities of brain (Q04.3), Septo-optic dysplasia of brain (Q04.4), congenital cerebral cysts (Q04.6), other specified congenital malformations of brain (Q04.8) and congenital malformation of brain, unspecified (Q04.9).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

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), DRG 093 (Other Disorders of Nervous System without CC/MCC, relative weight 0.7783), DRG 791 (Prematurity with Major Problems, relative weight 4.1075) and DRG 793 (Full Term Neonate with Major Problems, relative weight 4.2195), in MDC 01 (Diseases and Disorders of the Nervous System) and MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period), 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 is exempt from present-on-admission (POA) reporting, so no POA indicator is required.

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 742.4 (other specified congenital anomalies of brain).

Notes that apply from higher levels

Instructions written at a parent level also apply to Q04.5.

› From Q04 Other congenital malformations of brain
Excludes1

Broader instructions also apply from Chapter 17: Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders.

Alphabetic index entries

2 entries

Terms in the official ICD-10-CM index that lead to Q04.5.

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.

MDC 15 · Newborns and Other Neonates with Conditions Originating in the Perinatal Period

MDC 15 · Newborns and Other Neonates with Conditions Originating in the Perinatal Period

ICD-9-CM equivalent

Converter →
  • 742.4Other specified congenital anomalies of brainapproximate

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 Q04.5

Is Q04.5 billable?

Yes. Q04.5 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can Q04.5 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict Q04.5 as a principal diagnosis.

Is Q04.5 a CC or MCC?

Q04.5 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does Q04.5 group to?

Q04.5 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), MS-DRG 093 (Other Disorders of Nervous System without CC/MCC), MS-DRG 791 (Prematurity with Major Problems) and MS-DRG 793 (Full Term Neonate with Major Problems). 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 Q04.5?

The CMS General Equivalence Mappings map Q04.5 to ICD-9-CM 742.4.