2026 ICD-10-CM Diagnosis Code Q04.3Other reduction deformities of brain

AHRQ’s CCSR groups this code into broader clinical categories.

• Classical Lissencephalies and Subcortical Band Heterotopias

  disorders comprising a spectrum of brain malformations representing the paradigm of a diffuse neuronal migration disorder. they result in cognitive impairment; seizures; and hypotonia or spasticity. mutations of two genes, lis1, the gene for the non-catalytic subunit of platelet-activating factor acetylhydrolase ib; and dcx or xlis, the gene for doublecortin, have been identified as the most common causes of disorders in this spectrum. additional variants of classical (type i) lissencephaly have been linked to reln, the gene for reelin, and arx, the gene for aristaless related homeobox protein. (from leventer, r.j., et al, mol med today. 2000 jul;6(7):277-84 and barkovich, a.j., et al, neurology. 2005 dec 27;65(12):1873-87.)

• Cobblestone Lissencephaly

  the smooth pebbled appearance of the cerebral cortex with a thickened cortex and reduced and abnormal white matter, which results from migration of heterotopic neurons beyond the marginal zone into the leptomeninges through gaps in the external basement membrane. there is also enlarged ventricles, underdeveloped brainstem and cerebellum, and absence of the corpus callosum. these abnormalities occur as a syndrome without other birth defects (cobblestone complex) or in other syndromes associated with congenital muscular dystrophy, often involving the eye, such as the walker-warburg syndrome, fukuyama congenital muscular dystrophy, and muscle-eye-brain disease.

• Doublecortin Protein

  a microtubule-associated protein that is primarily found in neuronal precursor cells and immature neurons in embryonic and adult cortical structures.

• 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.

• Hydranencephaly

  a congenital condition where the greater portions of the cerebral hemispheres and corpus striatum are replaced by csf and glial tissue. the meninges and the skull are well formed, which is consistent with earlier normal embryogenesis of the telencephalon. bilateral occlusions of the internal carotid arteries in utero is a potential mechanism. clinical features include intact brainstem reflexes without evidence of higher cortical activity. (menkes, textbook of child neurology, 5th ed, p307)

• Neurons

  the basic cellular units of nervous tissue. each neuron consists of a body, an axon, and dendrites. their purpose is to receive, conduct, and transmit impulses in the nervous system.

• Cerebral Cortex

  the thin layer of gray matter on the surface of the cerebral hemispheres that develops from the telencephalon and folds into gyri and sulci. it reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.

• DCX wt Allele|DBCN|DC|Doublecortex Gene|Doublecortex; Lissencephaly, X-Linked (Doublecortin) Gene|Doublecortin wt Allele|LISX|SCLH|XLIS

  human dcx wild-type allele is located within xq22.3-q23 and is approximately 119 kb in length. this allele, which encodes neuronal migration protein doublecortin, plays a role in the mediation of neural migration. mutations in the gene are associated with lissencephaly x-linked type 1 and subcortical band heterotopia x-linked.

• Multinucleated Neurons, Anhydramnios, Renal Dysplasia, Cerebellar Hypoplasia and Hydranencephaly|MARCH

  a lethal autosomal recessive condition caused by mutation(s) in the cep55 gene, encoding centrosomal protein of 55 kda. it is characterized by renal dysplasia, anhydramnios, hydrancephaly, cerebellar hypoplasia, and multinucleated neurons in remaining brain tissue.

• Congenital Cerebellar Hypoplasia

  hypoplasia of the cerebellum that is associated with inherited metabolic disorders and neurodegenerative disorders. signs and symptoms include mental and developmental delays, walking and balance difficulties, floppy muscle tone, and seizures.

• Congenital Diaphragmatic Hernia

  diaphragmatic hernia that is present at birth.

• Classical Lissencephaly|Lissencephaly Type I

  a genetic disorder caused by mutations in the lis1, xlis, or tuba1a genes. it results in brain malformation characterized by the underdevelopment or absence of gyri or ridges in the cerebral cortex. signs and symptoms include epilepsy and mental retardation.

• DCX Gene|DCX|DCX|Doublecortex; Lissencephaly, X-Linked (Doublecortin) Gene

  this gene is involved in neuronal migration.

• DCX wt Allele|DBCN|DC|Doublecortex; Lissencephaly, X-Linked (Doublecortin) wt Allele|LISX|SCLH|XLIS

  human dcx wild-type allele is located within xq22.3-q23 and is approximately 119 kb in length. this allele, which encodes neuronal migration protein doublecortin, plays a role in the mediation of neural migration. mutations in the gene are associated with lissencephaly x-linked type 1 and subcortical band heterotopia x-linked.

• Lissencephaly

  a rare genetic brain malformation characterized by smooth folds and grooves in the brain. there are approximately 20 different types of lissencephaly that are identified by various symptoms.

• Lissencephaly 3|LIS3

  an autosomal dominant sub-type of lissencephaly caused by mutation(s) in the tuba1a gene, encoding adhesion tubulin alpha-1a chain.

• Mental Retardation, Autosomal Recessive 34|MRT34|Mental Retardation, Autosomal Recessive 34, with Variant Lissencephaly

  an autosomal recessive condition caused by mutation(s) in the cradd gene, encoding death domain-containing protein cradd. it is characterized by mild to moderate intellectual disability and lissencephaly with anterior-predominant pachygyria.

• Miller-Dieker Syndrome|Miller-Dieker Lissencephaly Syndrome

  a rare syndrome caused by deletion of genetic material in the short arm of chromosome 17. it is characterized by an abnormally smooth brain with fewer folds and grooves. it results in intellectual disability, developmental delay, seizures, spasticity, hypotonia, and feeding difficulties. affected individuals have distinctive facial features that include a prominent forehead, midface hypoplasia, small, upturned nose, low-set ears, small jaw, and thick upper lip.

• Platelet-Activating Factor Acetylhydrolase IB Subunit Alpha|LIS-1|Lissencephaly-1 Protein|PAF Acetylhydrolase 45 kDa Subunit|PAF-AH 45 kDa Subunit|PAF-AH Alpha|PAFAH Alpha

  platelet-activating factor acetylhydrolase ib subunit alpha (410 aa, ~47 kda) is encoded by the human pafah1b1 gene. this protein is involved in neuronal migration.

• Nephrocystin-1|Juvenile Nephronophthisis 1 Protein|NPHP1

  nephrocystin-1 (732 aa, ~83 kda) is encoded by the human nphp1 gene. this protein is involved in the modulation of signaling.

• Nephronophthisis

  progressive tubulointerstitial injury, inherited in an autosomal recessive pattern, caused by mutations in genes involved in ciliary function, which may result in an end stage renal failure.

• Nephronophthisis 1|Familial Juvenile Nephronophthisis|Juvenile Nephronophthisis|NPH1

  progressive tubulointerstitial nephritis inherited in an autosomal recessive manner. it is caused by mutations in the nphp1 gene. patients present with anemia, polyuria, and polydipsia during childhood. the progressive bilateral kidney damage results in renal failure.

• NPHP1 Gene|NPHP1|NPHP1|Nephronophthisis 1 (Juvenile) Gene

  this gene is involved in the mediation of signal transduction.

• NPHP1 wt Allele|FLJ97602|JBTS4|NPH1|Nephronophthisis 1 (Juvenile) wt Allele|SLSN1

  human nphp1 wild-type allele is located in the vicinity of 2q13 and is approximately 83 kb in length. this allele, which encodes nephrocystin-1 protein, plays a role in the progression of adhesion-dependent signaling pathways. mutations in the gene are associated with familial juvenile nephronophthisis type 1, senior-loken syndrome type 1, and joubert syndrome type 4.

• ACD Gene Mutation|ACD, Shelterin Complex Subunit and Telomerase Recruitment Factor Gene Mutation|Adrenocortical Dysplasia Homolog (Mouse) Gene Mutation|PIP1 Gene Mutation|PTOP Gene Mutation|TINT1 Gene Mutation|TPP1 Gene Mutation

  a change in the nucleotide sequence of the acd gene.

• ACD wt Allele|ACD, Mouse, Homolog of Gene|ACD, Shelterin Complex Subunit and Telomerase Recruitment Factor wt Allele|Adrenocortical Dysplasia Homolog (Mouse) Gene|PIP1|PTOP|TPP1

  human acd wild-type allele is located in the vicinity of 16q22.1 and is approximately 3 kb in length. this allele, which encodes adrenocortical dysplasia protein homolog, is involved in telomere protection.

• Adrenocortical Dysplasia Protein Homolog|ACD|POT1 and TIN2 Organizing Protein|POT1 and TIN2-Interacting Protein|POT1- and TIN2- Organizing Protein|POT1-Interacting Protein 1|TIN2 Interacting Protein 1|TIN2-Interacting Protein 1|Telomere Protein TPP1

  adrenocortical dysplasia protein homolog (544 aa, ~58 kda) is encoded by the human acd gene. this protein plays a role in both the elongation and maintenance of telomeres.

• Complex Cortical Dysplasia with other Brain Malformations 5|CDCBM5|TUBB2A Tubulinopathy

  an autosomal dominant condition caused by mutation(s) in the tubb2a gene, encoding tubulin beta-2a chain. it is characterized by cortical dysplasia and is associated with impaired intellectual development, hypotonia, global developmental delay, cortical dysplasia, and dysmorphic corpus callosum.

• Cortical Dysplasia

  malformation of the cerebral cortex due to improper migration of neurons in utero.

• Cortical Dysplasia-Focal Epilepsy Syndrome|CDFE Syndrome

  an autosomal recessive condition caused by mutation(s) in the cntnap2 gene, encoding contactin-associated protein-like 2. it is characterized by normal development until the onset of intractable focal seizures at age 1-9. after the onset of seizures, language regression, intellectual disability, hyperactivity, and impulsive behaviors begin to occur. the majority of children eventually fulfill the criteria for autism spectrum disorder.

• Aprosencephaly

  a very rare congenital brain defect in which the cerebral cortex, striatum, globus pallidus, thalamus, hypothalamus, and eyes are absent or rudimentary.

• Hydranencephaly

  a rare congenital brain disorder in which the cerebral hemispheres are absent and replaced by sacs that contain cerebrospinal fluid. signs and symptoms include irritability, increased muscle tone, seizures, and hydrocephalus. the prognosis is poor.

• Bilateral Frontoparietal Polymicrogyria|BFPP

  an autosomal recessive condition caused by mutation(s) in the adgrg1 gene, encoding adhesion g-protein coupled receptor g1. it is characterized by motor and cognitive developmental delay, pyramidal signs, and seizures.

• Microgyria

  a congenital abnormality characterized by the presence of abnormally small convolutions in the brain. it results in mental retardation.

• Polymicrogyria

  a developmental brain abnormality characterized by an excessive amount of small convolutions on the surface of the brain and cognitive dysfunction.

• Permanent Neonatal Diabetes Mellitus

  hyperglycemia in the first month of life due to a genetically determined defect in the structure, secretion and/or function of insulin that does not resolve spontaneously.

• Joubert Syndrome

  a rare genetic syndrome characterized by the hypoplasia or absence of the cerebellar vermis. signs and symptoms include rapid breathing (hyperpnea), sleep apnea, abnormal eye movements, mental retardation, and ataxia.

• Joubert Syndrome 17|JBTS17

  an autosomal recessive subtype of joubert syndrome caused by mutation(s) in the cplane1 gene, encoding ciliogenesis and planar polarity effector 1.

• Joubert Syndrome 3|JBTS3

  an autosomal recessive subtype of joubert syndrome caused by mutation(s) in the ahi1 gene, encoding jouberin.

• Joubert Syndrome 4

  a rare genetic syndrome caused by mutations in the nphp1 gene. it is characterized by the hypoplasia or absence of the cerebellar vermis. signs and symptoms include rapid breathing (hyperpnea), sleep apnea, abnormal eye movements, mental retardation, and ataxia.

• Joubert Syndrome 7|JBTS7

  an autosomal recessive sub-type of joubert syndrome caused by mutation(s) in the rpgrip1l gene, encoding a protein thought to function in programmed cell death. it is characterized by cerebellar and oculomotor apraxia, hypotonia and psychomotor delay, neonatal respiratory abnormalities, renal abnormalities, and retinal dystrophy.

• Joubert Syndrome 9|JBTS9

  an autosomal recessive subtype of joubert syndrome caused by mutation(s) in the cc2d2a gene, encoding coiled-coil and c2 domain-containing protein 2a.

• Congenital Hepatic Fibrosis

  a congenital disorder usually inherited in an autosomal recessive pattern. it affects the hepatobiliary system and the kidneys. it is characterized by liver fibrosis, portal hypertension, and renal cysts.

• X-Linked Lissencephaly-1|LISX1|X-linked Subcortical Band Heterotopia

  an x-linked subtype of lissencephaly caused by mutation(s) in the dcx gene, encoding neuronal migration protein doublecortin.

• Focal Cortical Dysplasia Type 1|FCD1|FCDI|Focal Cortical Dysplasia Type I

  focal cortical dysplasia characterized by abnormal cortical layering. it is associated with mild symptoms, late onset, and changes present in the temporal lobe. it includes the following: type ia with abnormal radial migration and maturation of neurons; type ib with disruption of the six-layered tangential composition of the cortex with immature neurons; and type ic comprising both architectural abnormalities.

• Focal Cortical Dysplasia Type 2|FCD2|FCDII|Focal Cortical Dysplasia Type II

  focal cortical dysplasia characterized by disrupted cortical lamination and specific cytological abnormalities. it includes type iia with dysmorphic neurons and type iib with dysmorphic neurons and balloon cells.

• Focal Cortical Dysplasia Type 3|FCD3|FCDIII|Focal Cortical Dysplasia Type III

  focal cortical dysplasia characterized by different cortical dyslamination and cytological abnormalities with the main lesions located in the same area. it includes the following: type iiia with architectural distortion of cortical layer in temporal lobe with hippocampal atrophy; type iiib with architectural distortion of cortical layer adjacent to glial or glioneuronal tumor; type iiic with architectural distortion of cortical layer adjacent to vascular malformation; and type iiid with architectural distortion of cortical layer adjacent to other lesions acquired in early childhood (e.g., trauma, ischemic event, and encephalitis).

• Focal Cortical Dysplasia|FCD

  a congenital cortical developmental abnormality characterized by focal architectural distortion of the cortical brain layers. it is associated with the presence of cytologic abnormalities including hypertrophic and dysmorphic neurons. it is caused by genetic or acquired factors and is often associated with epilepsy.

• Multinucleated Neurons, Anhydramnios, Renal Dysplasia, Cerebellar Hypoplasia And Hydranencephaly|MARCH

  a lethal autosomal recessive condition caused by mutation(s) in the cep55 gene, encoding centrosomal protein of 55 kda. it is characterized by renal dysplasia, anhydramnios, hydrancephaly, cerebellar hypoplasia, and multinucleated neurons in remaining brain tissue.

• Megalencephaly-Polymicrogyria-Polydactyly-Hydrocephalus Syndrome-1|MPPH1

  an autosomal dominant condition caused by mutation(s) in the pik3r2 gene, encoding phosphatidylinositol 3-kinase regulatory subunit beta. it is characterized by mild to severe intellectual disability, megencephaly, polymicrogyria, and postaxial polydactyly.

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.

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