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Q06.4 ICD-10-CM Code: Hydromyelia

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

Coding at a Glance

Tabular directives
1 inclusion term
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 Q06.4 in the official ICD-10-CM tabular list, quoted as published.

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

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Hydrorachis

Code Overview

Hydromyelia is a billable ICD-10-CM diagnosis code (Q06.4).

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 (2)

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

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.

Q05.4 — Unspecified spina bifida with hydrocephalus, Q05.5 — Cervical spina bifida without hydrocephalus, Q05.6 — Thoracic spina bifida without hydrocephalus, Q05.7 — Lumbar spina bifida without hydrocephalus, Q05.8 — Sacral spina bifida without hydrocephalus, Q05.9 — Spina bifida, unspecified, Q06.0 — Amyelia, Q06.1 — Hypoplasia and dysplasia of spinal cord, Q06.2 — Diastematomyelia, Q06.3 — Other congenital cauda equina malformations, Q06.8 — Other specified congenital malformations of spinal cord, Q06.9 — Congenital malformation of spinal cord, unspecified, Q07.00 — Arnold-Chiari syndrome without spina bifida or hydrocephalus, Q07.01 — Arnold-Chiari syndrome with spina bifida, Q07.02 — Arnold-Chiari syndrome with hydrocephalus, Q07.03 — Arnold-Chiari syndrome with spina bifida and hydrocephalus, Q07.8 — Other specified congenital malformations of nervous system, Q07.9 — Congenital malformation of nervous system, unspecified, S14.0XXA — Concussion and edema of cervical spinal cord, initial encounter, S14.0XXD — Concussion and edema of cervical spinal cord, subsequent encounter, +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).

Q05.4 — Unspecified spina bifida with hydrocephalus, Q05.5 — Cervical spina bifida without hydrocephalus, Q05.6 — Thoracic spina bifida without hydrocephalus, Q05.7 — Lumbar spina bifida without hydrocephalus, Q05.8 — Sacral spina bifida without hydrocephalus, Q05.9 — Spina bifida, unspecified, Q06.0 — Amyelia, Q06.1 — Hypoplasia and dysplasia of spinal cord, Q06.2 — Diastematomyelia, Q06.3 — Other congenital cauda equina malformations, Q06.8 — Other specified congenital malformations of spinal cord, Q06.9 — Congenital malformation of spinal cord, unspecified, Q07.00 — Arnold-Chiari syndrome without spina bifida or hydrocephalus, Q07.01 — Arnold-Chiari syndrome with spina bifida, Q07.02 — Arnold-Chiari syndrome with hydrocephalus, Q07.03 — Arnold-Chiari syndrome with spina bifida and hydrocephalus, Q07.8 — Other specified congenital malformations of nervous system, Q07.9 — Congenital malformation of nervous system, unspecified, Q85.00 — Neurofibromatosis, unspecified, Q85.01 — Neurofibromatosis, type 1, +29 more

Contextual Map

Every relationship of Q06.4 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.

Hierarchy

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

  • Hydromyelia[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Hydrorachis[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

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. "Q06.4 — Hydromyelia." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/q06.4-hydromyelia

Change history

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

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.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Q06.4 in its code family, with their registry titles.

View all codes in the Q06 family