2027 ICD-10-CM Diagnosis Code Q07.02Arnold-Chiari syndrome with hydrocephalus
ICD-10-CM Codes›Q00-Q99›Q00-Q07›Q07
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 182
- POA Exempt
- Chronic Condition
Q07.02 is a billable ICD-10-CM diagnosis code for Arnold-Chiari syndrome with hydrocephalus. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 91 through 93, 791, 793. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 65 closely related codes. The code is exempt from POA reporting. Coders also document this condition as chiari malformation. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nervous system congenital anomalies.
For Medicare Advantage risk adjustment, Q07.02 maps to CMS-HCC Category 182 (Spinal Cord Disorders/Injuries) under the V28 model, adding a risk factor of about 0.478 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Present on Admission (POA)Billing
Q07.02 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Congenital malformations of the nervous system (Q00-Q07).
Medicare Risk Adjustment (HCC)Billing
Q07.02 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Chiari malformation
- Chiari malformation type II
- Hydrocephalus due to Arnold Chiari malformation
- Hydrocephalus due to Arnold Chiari malformation type 2
- Obstructive hydrocephalus
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to Q07.02: its own notes plus those printed at Q07.0, Q07, and Chapter 17. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Notes
General instructions on how these codes are used.
- Codes from this chapter are not for use on maternal records
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name Q07.02, its category, or a range that includes it.
Excludes1 3
These codes carry an Excludes1 note naming Q07.02: they are not reported together with it, unless the two conditions are unrelated.
- G91 HydrocephalusArnold-Chiari syndrome with hydrocephalus (Q07.-) names Q07.-, which includes this code
- Q03 Congenital hydrocephalusArnold-Chiari syndrome, type II (Q07.0-) names Q07.0-, which includes this code
- Q05 Spina bifidaArnold-Chiari syndrome, type II (Q07.0-) names Q07.0-, which includes this code
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Arnold-Chiari Malformation
a group of congenital malformations involving the brainstem, cerebellum, upper spinal cord, and surrounding bony structures. type ii is the most common, and features compression of the medulla and cerebellar tonsils into the upper cervical spinal canal and an associated meningomyelocele. type i features similar, but less severe malformations and is without an associated meningomyelocele. type iii has the features of type ii with an additional herniation of the entire cerebellum through the bony defect involving the foramen magnum, forming an encephalocele. type iv is a form a cerebellar hypoplasia. clinical manifestations of types i-iii include torticollis; opisthotonus; headache; vertigo; vocal cord paralysis; apnea; nystagmus, congenital; swallowing difficulties; and ataxia. (from menkes, textbook of child neurology, 5th ed, p261; davis, textbook of neuropathology, 2nd ed, pp236-46)
Patient EducationClinical
Chiari Malformation
Chiari malformations (CMs) are structural defects in the cerebellum. The cerebellum is the part of the brain that controls balance. With CM, brain tissue extends into the spinal canal. It can happen when part of the skull is too small, which pushes the brain tissue down. There are several types of CM.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert Q07.02 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About Q07.02Overview
What is the ICD-10 code for Arnold-Chiari syndrome with hydrocephalus?
The ICD-10-CM code for Arnold-Chiari syndrome with hydrocephalus is Q07.02 (sometimes written as Q0702). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is Q07.02 (Arnold-Chiari syndrome) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report Arnold-Chiari syndrome with hydrocephalus on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does Q07.02 group to?
When Arnold-Chiari syndrome with hydrocephalus is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 91, 92, 93, with relative weights from 0.7783 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Is Q07.02 a CC or MCC?
CMS lists Q07.02 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 65 closely related codes in its exclusion list.
Is Q07.02 exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for Arnold-Chiari syndrome with hydrocephalus on inpatient claims. The code appears in the Congenital malformations of the nervous system (Q00-Q07) range of the CMS exempt list.
What HCC is Q07.02?
Q07.02 (Arnold-Chiari syndrome with hydrocephalus) maps to CMS-HCC Category 182 (Spinal Cord Disorders/Injuries), commonly written as HCC 182, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 72 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 155.
Does Q07.02 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, Q07.02 adds a risk adjustment factor of about 0.478 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.270 to 0.478 depending on the payment segment). A more severe related category (HCC 180, HCC 181, HCC 191, and HCC 192) supersedes it when both are reported. See the full factor table on the HCC 182 category page.
