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Q02 ICD-10-CM Code: Microcephaly

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
2 inclusion terms · 1 Excludes1 · 1 code-first instruction
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 72 · RxHCC V08 category 155

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 091 — OTHER DISORDERS OF NERVOUS SYSTEM WITH MCC (MDC 01)
  • MS-DRG 092 — OTHER DISORDERS OF NERVOUS SYSTEM WITH CC (MDC 01)
  • MS-DRG 093 — OTHER DISORDERS OF NERVOUS SYSTEM WITHOUT CC/MCC (MDC 01)
  • MS-DRG 791 — PREMATURITY WITH MAJOR PROBLEMS (MDC 15)
  • MS-DRG 793 — FULL TERM NEONATE WITH MAJOR PROBLEMS (MDC 15)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 182 — Spinal Cord Disorders/Injuries

Other models: CMS-HCC V22 HCC 72 · RxHCC V08 HCC 155

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Q02 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • hydromicrocephaly
  • micrencephalon

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Code First

Underlying conditions that must be sequenced before this code.

  • Code first, if applicable, congenital Zika virus disease

Coder workflow for Q02

MedCoder structured workflow — derived from this code’s own official record

Before you code Q02

  1. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with Q02. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in Q02’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewQ61.9

  2. Is the underlying (etiologic) condition the Code First note names documented?
    Yes → Sequence the underlying condition first, then Q02.
    No → Continue; do not add an underlying condition the record does not document.

Consider Q02. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The underlying (etiologic) condition
Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).

Official instructions as workflow

  • Excludes1 — check before selecting Q02(1 note)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with Q02: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareQ61.9

    See the official tabular notes · Guidelines I.A.12.a

  • Code First — sequencing check(1 note)

    Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before Q02. Do not add an underlying condition the record does not document.

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition Q02 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewQ61.9

Documentation: The underlying condition the Code First note names is documented alongside this condition.

Coding question: How are the two sequenced?

Path: Review the Code First note.

Reason: The underlying condition is sequenced first and the manifestation follows (Guidelines I.A.13).

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Microcephaly is a billable ICD-10-CM diagnosis code (Q02).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (19)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name Q02 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: Q75 — Other congenital malformations of skull and face bones.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Use Additional Code instruction: Q87.88 — CTNNB1 syndrome.

These codes instruct coders to additionally report this code when it applies.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 5 MS-DRGs: DRG 091 (MDC 01), DRG 092 (MDC 01), DRG 093 (MDC 01), DRG 791 (MDC 15), DRG 793 (MDC 15).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):MAL004 — Nervous system congenital anomalies (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Spinal Cord Disorders/Injuries) for risk-adjusted payment.

G99.2 — Myelopathy in diseases classified elsewhere, P11.5 — Birth injury to spine and spinal cord, Q00.0 — Anencephaly, Q00.1 — Craniorachischisis, Q00.2 — Iniencephaly, Q01.0 — Frontal encephalocele, Q01.1 — Nasofrontal encephalocele, Q01.2 — Occipital encephalocele, Q01.8 — Encephalocele of other sites, Q01.9 — Encephalocele, unspecified, Q03.0 — Malformations of aqueduct of Sylvius, Q03.1 — Atresia of foramina of Magendie and Luschka, Q03.8 — Other congenital hydrocephalus, Q03.9 — Congenital hydrocephalus, unspecified, Q04.0 — Congenital malformations of corpus callosum, Q04.1 — Arhinencephaly, Q04.2 — Holoprosencephaly, Q04.3 — Other reduction deformities of brain, Q04.4 — Septo-optic dysplasia of brain, Q04.5 — Megalencephaly, +230 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Quadriplegia, Paraplegia

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Nervous system congenital anomalies).

Q00.0 — Anencephaly, Q00.1 — Craniorachischisis, Q00.2 — Iniencephaly, Q01.0 — Frontal encephalocele, Q01.1 — Nasofrontal encephalocele, Q01.2 — Occipital encephalocele, Q01.8 — Encephalocele of other sites, Q01.9 — Encephalocele, unspecified, Q03.0 — Malformations of aqueduct of Sylvius, Q03.1 — Atresia of foramina of Magendie and Luschka, Q03.8 — Other congenital hydrocephalus, Q03.9 — Congenital hydrocephalus, unspecified, Q04.0 — Congenital malformations of corpus callosum, Q04.1 — Arhinencephaly, Q04.2 — Holoprosencephaly, Q04.3 — Other reduction deformities of brain, Q04.4 — Septo-optic dysplasia of brain, Q04.5 — Megalencephaly, Q04.6 — Congenital cerebral cysts, Q04.8 — Other specified congenital malformations of brain, +29 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Anomaly, anomalous”, “Deformity”, “Agenesis”, …; these codes share that main term but sit in a different category of the Tabular List.

O33.7 — Maternal care for disproportion due to other fetal deformities (fetal, with fetopelvic disproportion), O33.8 — Maternal care for disproportion of other origin (lumbar spine, with disproportion), O34.8 — Maternal care for other abnormalities of pelvic organs (soft parts, organs or tissues, in pregnancy or childbirth NEC), O65.0 — Obstructed labor due to deformed pelvis (lumbar spine, with disproportion, causing obstructed labor), O65.5 — Obstructed labor due to abnormality of maternal pelvic organs (soft parts, organs or tissues, in pregnancy or childbirth NEC, causing obstructed labor), O66.3 — Obstructed labor due to other abnormalities of fetus (fetal, causing obstructed labor), P28.0 — Primary atelectasis of newborn (pulmonary, associated with short gestation), P37.1 — Congenital toxoplasmosis (due to toxoplasmosis), P83.5 — Congenital hydrocele (genitalia, genital organor system, male, hydrocele), Q00.0 — Anencephaly (brain), Q03.0 — Malformations of aqueduct of Sylvius (aqueduct of Sylvius), Q03.1 — Atresia of foramina of Magendie and Luschka (Dandy-Walker), Q03.9 — Congenital hydrocephalus, unspecified (skull, with, hydrocephalus), Q04.0 — Congenital malformations of corpus callosum (corpus callosum), Q04.3 — Other reduction deformities of brain (cerebellum), Q04.8 — Other specified congenital malformations of brain (gyri), Q04.9 — Congenital malformation of brain, unspecified (brain), Q05.9 — Spina bifida, unspecified (meningocele), Q06.0 — Amyelia (spinal cord), Q06.1 — Hypoplasia and dysplasia of spinal cord (spinal), +594 more

Contextual Map

Every relationship of Q02 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run Q02 with these 3 related codes in Claim Check

Hierarchy

Excludes1

Referenced by Excludes1 notes

Referenced by Use Additional Code instructions

  • Q87.88 — CTNNB1 syndrome[Use Additional Code]: “microcephaly (Q02)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 182 — Spinal Cord Disorders/Injuries [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

MDC crossing

  • MDC 01 — Diseases and Disorders of the Nervous System[MDC crossing]: “Diseases and Disorders of the Nervous System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 8,892 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026
  • MDC 15 — Newborns and Other Neonates with Conditions Originating in Perinatal Period[MDC crossing]: “Newborns and Other Neonates with Conditions Originating in Perinatal Period — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”— CMS MS-DRG Definitions Manual · FY2026

Index entries (19)

  • Absence (of) (organ or part) (complete or partial), skull bone (congenital), with, microcephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Agenesis, skull (bone), with, microcephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Anomaly, anomalous (congenital) (unspecified type), bone, skull, with, microcephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Anomaly, anomalous (congenital) (unspecified type), skull, with, microcephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Deformity, skull (acquired), congenital, with, microcephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Distortion (s) (congenital), skull bone NEC (s), with, microcephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Hydromicrocephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Hypoplasia, hypoplastic, brain[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • and 11 more

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "Q02 — Microcephaly." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/q02-microcephaly

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Microcephaly

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.