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Q07.03 ICD-10-CM Code: Arnold-Chiari syndrome with spina bifida and hydrocephalus

Q07.03 maps to CMS-HCC V28 182. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools

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Code lookupQ07.03

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

Q07.03

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

Arnold-Chiari syndrome with spina bifida and hydrocephalus

A birth defect combining brain tissue extending into the spinal canal, an opening in the spine, and excess fluid in the brain, causing multiple neurological complications.

Buddy the Bee presenting code insight

Buddy Insight

This represents the most complex form of Arnold-Chiari syndrome, combining brain herniation, open spine defects, and increased intracranial pressure.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 182

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 114

Code-level coefficient reference

+ HCC 121

ESRD/PACE

HCC 72

Code-level coefficient reference

RXHCC

HCC 155

Code-level coefficient reference

Code Book Path

Official
Q07Other congenital malformations of nervous systemQ07.0Arnold-Chiari syndromeQ07.03Arnold-Chiari syndrome with spina bifida and hydrocephalus

Inclusion Terms

Official
  • Arnold-Chiari syndrome, type IIInherited from Q07.0

Excludes 2

Official
  • inborn errors of metabolism (E70-E88)Inherited from Q00-QA0, Q07
  • congenital central alveolar hypoventilation syndrome (G47.35)Inherited from Q00-QA0, Q07
  • familial dysautonomia [Riley-Day] (G90.1)Inherited from Q00-QA0, Q07
  • neurofibromatosis (nonmalignant) (Q85.0-)Inherited from Q00-QA0, Q07

Related Codes

Official
Q07.00Arnold-Chiari syndrome without spina bifida or hydrocephalusQ07.01Arnold-Chiari syndrome with spina bifidaQ07.02Arnold-Chiari syndrome with hydrocephalus

Includes

Official

No Includes notes are included in this display for Q07.03. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • Arnold-Chiari syndrome, type III (Q01.-)Inherited from Q07.0
  • Arnold-Chiari syndrome, type IV (Q04.8)Inherited from Q07.0

Code First

Official

No Code First sequencing instructions are included in this display for Q07.03. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for Q07.03. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for Q07.03. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
MRI confirmation of cerebellar tonsillar herniation
Documentation of spina bifida with anatomical location
Evidence of hydrocephalus and increased intracranial pressure
Comprehensive neurological deficit assessment

MEAT Support

HCC Buddy guidance
MRI confirmation of cerebellar tonsillar herniation
Documentation of spina bifida with anatomical location
Evidence of hydrocephalus and increased intracranial pressure
Comprehensive neurological deficit assessment

Audit Caution

HCC Buddy guidance
Using separate codes when all three components are present
Missing one of the three key components
Failing to document the complexity of care required
Not coding secondary complications separately when appropriate

Common Mistakes

HCC Buddy guidance
Q07.00 — Arnold-Chiari syndrome without spina bifida or hydrocephalus
Q07.01 — Arnold-Chiari syndrome with spina bifida only
Q07.02 — Arnold-Chiari syndrome with hydrocephalus only
Q05.4 — unspecified spina bifida with hydrocephalus

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is Q07.03 an HCC code?

Yes. Q07.03 (Arnold-Chiari syndrome with spina bifida and hydrocephalus) maps to HCC 182, Spinal Cord Disorders/Injuries under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.478. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: Q07.03 is billable and maps to V28 HCC 182, Spinal Cord Disorders/Injuries. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
Q07.03
Description
Arnold-Chiari syndrome with spina bifida and hydrocephalus
HCC (V28)
HCC 182 — Spinal Cord Disorders/Injuries
RAF reference coefficient
0.478
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 182, Spinal Cord Disorders/Injuries
0.478
ESRDHCC 72, Spinal Cord Disorders/Injuries
Not separately weighted
RxHCCHCC 155, Spinal Cord Disorders
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work Q07.03 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for Q07.03

For Q07.03, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

Q07.03 is the ICD-10-CM diagnosis code for arnold-chiari syndrome with spina bifida and hydrocephalus. A birth defect combining brain tissue extending into the spinal canal, an opening in the spine, and excess fluid in the brain, causing multiple neurological complications. Q07.03 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, Q07.03 maps to Spinal Cord Disorders/Injuries (HCC 182) with a source-labeled community, non-dual, aged reference coefficient of 0.478. No V24 mapping is shown for Q07.03; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

This code requires documentation of all three components: Arnold-Chiari, spina bifida, AND hydrocephalus. For Q07.03, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for Q07.03 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •This code requires documentation of all three components: Arnold-Chiari, spina bifida, AND hydrocephalus
  • •Carefully review imaging and clinical notes to confirm all three conditions are present before assigning this code

Clinical Significance

This represents the most complex form of Arnold-Chiari syndrome, combining brain herniation, open spine defects, and increased intracranial pressure. This combination requires the most intensive multidisciplinary management, multiple surgical interventions, and carries the highest risk of severe neurological complications.

Documentation Requirements

  • ✓MRI confirmation of cerebellar tonsillar herniation
  • ✓Documentation of spina bifida with anatomical location
  • ✓Evidence of hydrocephalus and increased intracranial pressure
  • ✓Comprehensive neurological deficit assessment
  • ✓Multiple surgical intervention history
  • ✓Shunt function and complications
  • ✓Functional status and quality of life measures
  • ✓Complex care coordination documentation

Commonly Confused Codes

  • •Q07.00: Arnold-Chiari syndrome without spina bifida or hydrocephalus
  • •Q07.01: Arnold-Chiari syndrome with spina bifida only
  • •Q07.02: Arnold-Chiari syndrome with hydrocephalus only
  • •Q05.4: unspecified spina bifida with hydrocephalus
  • •Q04.3: other reduction deformities of brain

Child Codes

Q07.00Arnold-Chiari syndrome without spina bifida or hydrocephalus
HCC 182
Q07.01Arnold-Chiari syndrome with spina bifida
HCC 182
Q07.02Arnold-Chiari syndrome with hydrocephalus
HCC 182
Q07.03Arnold-Chiari syndrome with spina bifida and hydrocephalus
HCC 182

Code Hierarchy

└Q07Other congenital malformations of nervous system└Q07.0Arnold-Chiari syndrome└Q07.03Arnold-Chiari syndrome with spina bifida and hydrocephalus
└Q07.03Arnold-Chiari syndrome with spina bifida and hydrocephalus

For Q07.03, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

Q07.03 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. The mapping identifies a payment HCC category for Q07.03. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

More on Q07.03

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