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Q02 ICD-10-CM Code: Microcephaly

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FY 2026 Apr update / Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0) / Congenital malformations of the nervous system (Q00-Q07)

Q02

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Microcephaly

A birth defect where the baby's head and brain are smaller than normal, which can affect development and function.

Buddy the Bee presenting code insight

Buddy Insight

Microcephaly represents significantly reduced head and brain size at birth, indicating impaired brain development with high risk for intellectual disability, developmental delays, and neurological complications.

CMS-HCC V28

HCC 182

RAF 0.478

CMS-HCC V24

HCC 72

RAF 0.481

ACA/HHS

HCC 114

Varies by metal level

ESRD/PACE

HCC 72

RAF 0.099

RXHCC

HCC 155

RAF 0.086

Code Book Path

Official
Q0Congenital malformations of the nervous system (Q00-Q07)
Q02Microcephaly

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for Q02 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for Q02 in this effective period.

Related Child Codes

Official

ICD-10-CM does not list child codes under Q02 for this display context.

Includes

Official
  • hydromicrocephaly
  • micrencephalon

Excludes 1

Official
  • Meckel-Gruber syndrome (Q61.9)

Code First

Official
  • , if applicable, congenital Zika virus disease

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for Q02 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for Q02 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Head circumference measurements below 2-3 standard deviations for gestational age
Documentation of small brain size on neuroimaging
Associated dysmorphic features if present
Maternal history including infections, exposures, genetic factors

MEAT Support

HCC Buddy guidance
Head circumference measurements below 2-3 standard deviations for gestational age
Documentation of small brain size on neuroimaging
Associated dysmorphic features if present
Maternal history including infections, exposures, genetic factors

Audit Caution

HCC Buddy guidance
Confusing with normal variation in head size vs true microcephaly
Using developmental delay codes instead of structural brain malformation
Missing documentation of head circumference measurements
Confusing with secondary microcephaly from acquired causes

Common Mistakes

HCC Buddy guidance
Q00.0 — Anencephaly, absent brain vs small brain
Q04.3 — Other brain reduction deformities, specific vs general small brain
P02.7 — Fetus affected by chorioamnionitis, potential cause vs condition itself
F79 — Unspecified intellectual disabilities, developmental outcome vs structural cause

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is Q02 an HCC code?

Yes. Q02 maps to Spinal Cord Disorders/Injuries under the CMS-HCC V28 risk adjustment model (and Spinal Cord Disorders/Injuries under V24).

HCC Category Mapping

V28HCC 182, Spinal Cord Disorders/Injuries
0.478
V24HCC 72, Spinal Cord Disorders/Injuries
0.481
ESRDHCC 72, Spinal Cord Disorders/Injuries
0.099
RxHCCHCC 155, Myelitis and Encephalomyelitis
0.086

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work Q02 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for Q02

For Q02to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

  • MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
  • EEvaluate: test results, medication response, or physical findings reviewed by the provider
  • AAssess: explicit mention in the assessment or plan with acknowledgment of status
  • TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed Q02 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

Q02 is the ICD-10-CM diagnosis code for microcephaly. A birth defect where the baby's head and brain are smaller than normal, which can affect development and function. Q02 sits in the ICD-10-CM chapter for congenital malformations, deformations and chromosomal abnormalities (q00-qa0), within the section covering congenital malformations of the nervous system (q00-q07).

Under the CMS-HCC V28 risk adjustment model, Q02 maps to Spinal Cord Disorders/Injuries (HCC 182) with a community, non-dual, aged base RAF weight of 0.478. Under the older V24 model, Q02 mapped to the same category but with a base RAF weight of 0.481, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Document the severity (mild, moderate, severe) if specified in clinical notes. Because Q02 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q02 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Document the severity (mild, moderate, severe) if specified in clinical notes
  • •Note any associated conditions such as intellectual disability or seizures

Clinical Significance

Microcephaly represents significantly reduced head and brain size at birth, indicating impaired brain development with high risk for intellectual disability, developmental delays, and neurological complications. This diagnosis requires comprehensive evaluation for underlying causes and early intervention services.

Documentation Requirements

  • ✓Head circumference measurements below 2-3 standard deviations for gestational age
  • ✓Documentation of small brain size on neuroimaging
  • ✓Associated dysmorphic features if present
  • ✓Maternal history including infections, exposures, genetic factors
  • ✓Neurological examination findings
  • ✓Genetic testing results if performed
  • ✓Developmental assessments and early intervention referrals
  • ✓Ophthalmologic and hearing evaluations

Includes

  • hydromicrocephaly
  • micrencephalon

Excludes 1, Do NOT code together

  • Meckel-Gruber syndrome (Q61.9)

Code First

  • , if applicable, congenital Zika virus disease

Commonly Confused Codes

  • •Q00.0: Anencephaly, absent brain vs small brain
  • •Q04.3: Other brain reduction deformities, specific vs general small brain
  • •P02.7: Fetus affected by chorioamnionitis, potential cause vs condition itself
  • •F79: Unspecified intellectual disabilities, developmental outcome vs structural cause

Code Hierarchy

└Q02Microcephaly
└Q02Microcephaly

Because Q02 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

Q02 maps to CMS-HCC V28 category 182, Spinal Cord Disorders/Injuries. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works.

Work Q02 in HCC Buddy

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