Other congenital malformations of brain (Q04) ICD-10-CM
The Q04 code range covers other congenital malformations of brain with 10 ICD-10-CM diagnosis codes. 9 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Codes in the Q04 Range 10 codes · 9 billable
- Q04 Other congenital malformations of brainNon-billable
- Q04.0 Congenital malformations of corpus callosum
- Q04.1 Arhinencephaly
- Q04.2 Holoprosencephaly
- Q04.3 Other reduction deformities of brain
- Q04.4 Septo-optic dysplasia of brain
- Q04.5 Megalencephaly
- Q04.6 Congenital cerebral cysts
- Q04.8 Other specified congenital malformations of brain
- Q04.9 Congenital malformation of brain, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the Q04 range.
Holoprosencephaly
Anterior midline brain, cranial, and facial malformations resulting from the failure of the embryonic prosencephalon to undergo segmentation and cleavage. Alobar prosencephaly is the most severe form and features anophthalmia; cyclopia; severe INTELLECTUAL DISABILITY; CLEFT LIP; CLEFT PALATE; SEIZURES; and microcephaly. Semilobar holoprosencepaly is characterized by hypotelorism, microphthalmia, coloboma, nasal malformations, and variable degrees of INTELLECTUAL DISABILITY. Lobar holoprosencephaly is associated with mild (or absent) facial malformations and intellectual abilities that range from mild INTELLECTUAL DISABILITY to normal. Holoprosencephaly is associated with CHROMOSOME ABNORMALITIES.
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.
Megalencephaly
A congenital abnormality in which the occipitofrontal circumference is greater than two standard deviations above the mean for a given age. It is associated with HYDROCEPHALUS; SUBDURAL EFFUSION; ARACHNOID CYSTS; or is part of a genetic condition (e.g., ALEXANDER DISEASE; SOTOS SYNDROME).
Porencephaly
Cortical malformations characterized by white matter-lined cleft or cyst associated with ISCHEMIA and hemorrhagic insults. Symptoms include delayed growth and development, HYPOTONIA; SEIZURES; SPASTIC HEMIPLEGIA and MACROCEPHALY; MICROCEPHALY; or HYDROCEPHALUS. Mutations in the genes encoding COLLAGEN TYPE IV are associated with familial types.
Schizencephaly
Cortical malformations characterized by grey matter-lined cleft or cyst that extends from the EPENDYMA often to the PIA MATER outer surface. The grey matter that lines the cleft is often POLYMICROGYRIA. It is associated with developmental delay, motor disturbance and seizures.
About the Q04 Code Range
These are brain malformations present at birth, within the larger group of congenital nervous system malformations.
The subdivisions distinguish malformations of the corpus callosum (Q04.0), reduction deformities (Q04.3), and brain cysts (Q04.6). Other subdivisions identify specific named conditions: arhinencephaly (Q04.1), holoprosencephaly (Q04.2), septo-optic dysplasia (Q04.4), and megalencephaly (Q04.5). The remaining subdivisions are for other specified (Q04.8) or unspecified (Q04.9) congenital brain malformations.
Questions About This Page
How many billable codes are in the Q04 range?
Of the 10 codes in this range, 9 are billable and valid for claim submission from October 1, 2026 through September 30, 2027. Category header codes group them but cannot be reported on claims.
What does the Q04 range classify?
The range classifies other congenital malformations of brain. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
