2027 ICD-10-CM Diagnosis Code Q04.3Other reduction deformities of brain
ICD-10-CM Codes›Q00-Q99›Q00-Q07›Q04
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 182
- POA Exempt
- Chronic Condition
Q04.3 is a billable ICD-10-CM diagnosis code for other reduction deformities of brain. 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 major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 14 closely related codes. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nervous system congenital anomalies.
For Medicare Advantage risk adjustment, Q04.3 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
Q04.3 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
Q04.3 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.
- Abnormality of neurogenesis
- Absence of septum pellucidum
- Agenesis of cerebellum
- Agenesis of cerebrum
- Agenesis of left hemisphere of cerebellum
- Agenesis of right hemisphere of cerebellum
- Aicardi's syndrome
- Anomalies of hypothalamus
- Anterior pituitary hormone deficiency
- Aplasia of cerebellum
- Aplasia of the vermis
- Aprosencephaly
- Aprosencephaly/atelencephaly spectrum
- Arachnoid cyst
- Atelencephaly
- Autosomal recessive frontotemporal pachygyria
- Bilateral frontal polymicrogyria
- Bilateral frontoparietal polymicrogyria
- Bilateral generalized polymicrogyria
- Bilateral parasagittal parieto-occipital polymicrogyria
- Bilateral polymicrogyria
- Cerebellum agenesis with hydrocephaly
- Cerebral cortical dysgenesis
- CIMDAG syndrome
- Cobblestone lissencephaly without muscular or ocular involvement
- Combined malformation of central nervous system and skeletal muscle
- Complete agenesis of vermis
- Congenital absence of part of brain
- Congenital agenesis of brainstem nuclei
- Congenital bilateral perisylvian syndrome
- Congenital cerebellar hypoplasia
- Congenital cerebellar hypoplasia co-occurrent with tapetoretinal degeneration
- Congenital chorioretinal degeneration
- Congenital conduction defect
- Congenital diaphragmatic hernia
- Congenital hepatic fibrosis
- Congenital hypoplasia of anterior pituitary
- Congenital hypoplasia of brainstem
- Congenital hypoplasia of cerebral hemisphere
- Congenital hypoplasia of cerebral white matter
- Congenital hypoplasia of cerebrum
- Congenital hypoplasia of frontal lobe
- Congenital hypoplasia of inferior vermis
- Congenital hypoplasia of inner granular layer of cerebellum
- Congenital hypoplasia of pars basalis of pons
- Congenital hypoplasia of part of brain
- Congenital malformation of anterior pituitary
- Congenital malformation of cerebellum
- Congenital muscular dystrophy with cerebellar involvement
- Congenital pontocerebellar hypoplasia
- Congenital pontocerebellar hypoplasia type 1
- Congenital pontocerebellar hypoplasia type 10
- Congenital pontocerebellar hypoplasia type 11
- Congenital pontocerebellar hypoplasia type 12
- Congenital pontocerebellar hypoplasia type 13
- Congenital pontocerebellar hypoplasia type 14
- Congenital pontocerebellar hypoplasia type 2
- Congenital pontocerebellar hypoplasia type 3
- Congenital pontocerebellar hypoplasia type 4
- Congenital pontocerebellar hypoplasia type 5
- Congenital pontocerebellar hypoplasia type 6
- Congenital pontocerebellar hypoplasia type 7
- Congenital pontocerebellar hypoplasia type 8
- Congenital pontocerebellar hypoplasia type 9
- Congenital porencephaly
- Cortical dysgenesis with pontocerebellar hypoplasia due to TUBB3 mutation
- Craniotelencephalic dysplasia
- Dyke-Davidoff-Masson syndrome
- Dysgenesis of the brainstem
- Early-onset progressive encephalopathy, hearing loss, pons hypoplasia, brain atrophy syndrome
- Epileptic spasms
- Facial dysmorphism, global developmental delay, hypotonia, polymicrogyria syndrome
- Familial aplasia of the vermis
- Fetal hereditary disease
- Fetal microcephaly
- Granular cell hypoplasia
- Hemispheric cerebellar agenesis
- Hemispheric cerebral agenesis
- Hydranencephaly
- Hydranencephaly with proliferative vasculopathy
- Hypoplasia of brain gyri
- Intellectual disability, coarse face, macrocephaly, cerebellar hypotrophy syndrome
- Isolated agenesis of cerebellar vermis
- Isolated bilateral hemispheric cerebellar hypoplasia
- Isolated cerebellar vermis hypoplasia
- Isolated lissencephaly type 1 without known genetic defect
- Isolated unilateral hemispheric cerebellar hypoplasia
- Jeune thoracic dystrophy
- Joubert syndrome
- Joubert syndrome with congenital hepatic fibrosis
- Joubert syndrome with Jeune asphyxiating thoracic dystrophy
- Joubert syndrome with ocular defect
- Joubert syndrome with oculorenal defect
- Joubert syndrome with orofaciodigital defect
- Joubert syndrome with renal defect
- Lethal hydranencephaly, diaphragmatic hernia syndrome
- Lethal pontocerebellar hypoplasia, hypotonia, respiratory insufficiency syndrome
- Lissencephaly
- Lissencephaly due to LIS1 mutation
- Lissencephaly due to TUBA1A mutation
- Lissencephaly syndrome Norman Roberts type
- Lissencephaly type 1 due to doublecortin gene mutation
- Lissencephaly type 3 familial fetal akinesia sequence syndrome
- Lissencephaly type 3 metacarpal bone dysplasia syndrome
- Lissencephaly with cerebellar hypoplasia
- Lissencephaly with cerebellar hypoplasia type A
- Lissencephaly with cerebellar hypoplasia type B
- Lissencephaly with cerebellar hypoplasia type C
- Lissencephaly with cerebellar hypoplasia type D
- Lissencephaly with cerebellar hypoplasia type E
- Lissencephaly with cerebellar hypoplasia type F
- Macroencephaly
- Macrogyria
- MARCH syndrome
- Megalencephaly, polymicrogyria, postaxial polydactyly, hydrocephalus syndrome
- Microcephalus, cerebellar hypoplasia, cardiac conduction defect syndrome
- Microcephaly, corpus callosum and cerebellar vermis hypoplasia, facial dysmorphism, intellectual disability syndrome
- Microcephaly, polymicrogyria, corpus callosum agenesis syndrome
- Microgyria
- Microlissencephaly
- Microlissencephaly micromelia syndrome
- Micromelia
- NDE1-related microhydranencephaly
- Neonatal diabetes mellitus
- Neonatal hypotonia
- Neonatal muscle tone disorder
- Neonatal neuromuscular disorder
- Nephronophthisis
- Occipital pachygyria and polymicrogyria
- Pachygyria, intellectual disability, epilepsy syndrome
- Partial absence of septum pellucidum
- Partial agenesis of corpus callosum
- Partial corpus callosum agenesis, cerebellar vermis hypoplasia with posterior fossa cysts syndrome
- Permanent neonatal diabetes mellitus
- Permanent neonatal diabetes mellitus with cerebellar agenesis syndrome
- Polymicrogyria due to TUBB2B mutation
- Polymicrogyria with optic nerve hypoplasia
- Pontine tegmental cap dysplasia
- Porencephaly, cerebellar hypoplasia, internal malformations syndrome
- Posterior-predominant lissencephaly, broad flat pons and medulla-midline crossing defects syndrome
- Progressive microcephaly
- Respiratory insufficiency syndrome of newborn
- Rhombencephalosynapsis
- Short rib dysplasia
- Short stature, pituitary and cerebellar defect and small sella turcica syndrome
- Spinal cord hypoplasia
- Type 1 lissencephaly
- Type 2 lissencephaly
- Type 3 lissencephaly
- Unilateral polymicrogyria
- Vascular Ehlers-Danlos, polymicrogyria syndrome
- White matter hypoplasia, corpus callosum agenesis, intellectual disability syndrome
- XK aprosencephaly syndrome
- X-linked intellectual disability with cerebellar hypoplasia syndrome
- X-linked intellectual disability, cerebellar hypoplasia, spondyloepiphyseal dysplasia syndrome
- X-linked lissencephaly with abnormal genitalia syndrome
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to Q04.3: its own notes plus those printed at Q04 and Chapter 17. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Absence of part of brain
- Agenesis of part of brain
- Agyria
- Aplasia of part of brain
- Hydranencephaly
- Hypoplasia of part of brain
- Lissencephaly
- Microgyria
- Pachygyria
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- congenital malformations of corpus callosum (Q04.0)
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.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
part of Q04.3
cerebellum Q04.3
vermis of cerebellum Q04.3
Agyria Q04.3
Aplasia See Also: Agenesis;
part of Q04.3
cerebellum Q04.3
reduction Q04.3
reduction (extremity) (limb), congenital See Also: condition and site; Q73.8
brain Q04.3
cerebellum Q04.3
Microgyria (congenital) Q04.3
Pachygyria Q04.3
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Lissencephaly
a smooth brain malformation of the cerebral cortex resulting from the abnormal location of developing neurons during corticogenesis. it is characterized by an absence of normal convoluted indentations on the surface of the brain (agyria), or fewer and shallower indentations (pachygryia). there is a reduced number of cortical layers, typically 4 instead of 6, resulting in a thickened cortex, and reduced cerebral white matter that is a reversal of the normal ratio of cerebral white matter to cortex.
Patient EducationClinical
Brain Malformations
Most brain malformations begin long before a baby is born. Something damages the developing nervous system or causes it to develop abnormally. Sometimes it's a genetic problem. In other cases, exposure to certain medicines, infections, or radiation during pregnancy interferes with brain development.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert Q04.3 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About Q04.3Overview
What is the ICD-10 code for other reduction deformities of brain?
The ICD-10-CM code for other reduction deformities of brain is Q04.3 (sometimes written as Q043). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is Q04.3 (Other congenital malformations of brain) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other reduction deformities of brain on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does Q04.3 group to?
When other reduction deformities of brain 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 Q04.3 a CC or MCC?
CMS lists Q04.3 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 14 closely related codes in its exclusion list.
Is Q04.3 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 other reduction deformities of brain 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 Q04.3?
Q04.3 (other reduction deformities of brain) 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 Q04.3 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, Q04.3 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.
