Arnold-Chiari syndrome with spina bifida

This code identifies a congenital malformation of the brain, specifically a Chiari malformation type II, which is characterized by downward displacement of the cerebellar tonsils and brainstem through the foramen magnum. This condition is invariably associated with spina bifida, a birth defect where the spinal cord and/or its protective covering do not develop properly. Patients often present with neurological deficits related to both the hindbrain herniation and the spinal cord defect.

Use this code when documentation explicitly states Arnold-Chiari syndrome (specifically Type II) in conjunction with spina bifida. This code is appropriate for patients diagnosed with this specific combined congenital anomaly, often identified prenatally or in early infancy. Supporting documentation should clearly link the Chiari malformation to the presence of spina bifida.

• Ensure the documentation specifies "Arnold-Chiari syndrome" or "Chiari Type II" and explicitly mentions the co-occurrence of spina bifida.
• Do not use this code for isolated Chiari malformations without documented spina bifida; other Chiari codes exist for those scenarios.
• Code any associated neurological manifestations or complications of spina bifida (e.g., hydrocephalus, paralysis) separately, following sequencing guidelines.