Arnold-Chiari syndrome with hydrocephalus

This code identifies a specific type of Arnold-Chiari malformation, a structural defect in the cerebellum, where the brainstem and cerebellum extend into the spinal canal, specifically when it is complicated by the presence of hydrocephalus. Hydrocephalus is characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the brain's ventricles, leading to increased intracranial pressure. This combination can result in a range of neurological symptoms due to compression of brain structures and elevated CSF pressure.

Use this code when documentation clearly indicates a diagnosis of Arnold-Chiari malformation (typically Type II or III) co-occurring with hydrocephalus. This diagnosis is often made based on neuroimaging studies (e.g., MRI) showing cerebellar tonsillar herniation and ventricular enlargement. Supporting documentation should detail both the Chiari malformation and the presence of hydrocephalus, including any associated symptoms or treatment.

• Ensure documentation specifies the presence of hydrocephalus; otherwise, a code for Arnold-Chiari without hydrocephalus may be more appropriate.
• Do not use this code for isolated hydrocephalus or other types of Chiari malformations without documented hydrocephalus.
• Consider sequencing this code as the primary diagnosis if it is the main reason for the encounter, followed by codes for any associated neurological manifestations or complications.