Chapter 17

Q00–Q99: Congenital Malformations, Deformations and Chromosomal Abnormalities

Congenital Malformations, Deformations and Chromosomal Abnormalities diagnostic classification updated for 2026.

Chapter Instructions

Excludes2(Not included here)
  • inborn errors of metabolism (E70-E88)
All CodesBillable Only
Browse by Section12 Sections
Internal Codes
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  • Q00—

    Anencephaly and similar malformations

  • Q00.0—

    Anencephaly

  • Q00.1—

    Craniorachischisis

  • Q00.2—

    Iniencephaly

  • Q01—

    Encephalocele

  • Q01.0—

    Frontal encephalocele

  • Q01.1—

    Nasofrontal encephalocele

  • Q01.2—

    Occipital encephalocele

  • Q01.8—

    Encephalocele of other sites

  • Q01.9—

    Encephalocele, unspecified

  • Q02—

    Microcephaly

  • Q03—

    Congenital hydrocephalus

  • Q03.0—

    Malformations of aqueduct of Sylvius

  • Q03.1—

    Atresia of foramina of Magendie and Luschka

  • Q03.8—

    Other congenital hydrocephalus

  • Q03.9—

    Congenital hydrocephalus, unspecified

  • Q04—

    Other congenital malformations of brain

  • 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

  • Q05—

    Spina bifida

  • Q05.0—

    Cervical spina bifida with hydrocephalus

  • Q05.1—

    Thoracic spina bifida with hydrocephalus

  • Q05.2—

    Lumbar spina bifida with hydrocephalus

  • Q05.3—

    Sacral spina bifida with hydrocephalus

  • 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—

    Other congenital malformations of spinal cord

  • Q06.0—

    Amyelia

  • Q06.1—

    Hypoplasia and dysplasia of spinal cord

  • Q06.2—

    Diastematomyelia

  • Q06.3—

    Other congenital cauda equina malformations

  • Q06.4—

    Hydromyelia

  • Q06.8—

    Other specified congenital malformations of spinal cord

  • Q06.9—

    Congenital malformation of spinal cord, unspecified

  • Q07—

    Other congenital malformations of nervous system

  • Q07.0—

    Arnold-Chiari syndrome

  • 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

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