CPT code 78635 represents a diagnostic imaging procedure that measures cerebrospinal fluid (CSF) flow to evaluate brain ventricular size and dynamics. This test is clinically important for diagnosing and monitoring hydrocephalus and related CSF circulation disorders, particularly in pediatric populations. Nationally, accurate coding and interpretation affect clinical decision-making, care coordination, and use of neurosurgical interventions.

Key payers in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context and typical settings for the service, along with benchmarking and policy-oriented information relevant to coverage and claims processing. The publication summarizes utilization patterns, common billing considerations, and potential documentation points that influence payment and medical necessity determinations. Where payer-specific policies are available, contrasts in prior authorization, coverage criteria, and reimbursement practice are highlighted to inform providers, coding professionals, and policy analysts.

The report is intended to equip clinicians and billing staff with a clear understanding of the code's clinical purpose, typical care settings, and the payer landscape that shapes access and reimbursement for CSF flow imaging.