CPT code 64421 represents an intercostal nerve injection performed at additional thoracic levels after the first level and is used when providers administer anesthetic and/or steroid adjacent to the ventral branches of the thoracic spinal nerves beneath the ribs. This procedure is clinically relevant for managing thoracic neuropathic pain and post-operative or post-traumatic chest wall pain, and it has implications for utilization, prior authorization, and clinical documentation nationally. Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical indication and procedural context for 64421, typical sites of service where the procedure is delivered, and common modifiers used for reporting. The publication also provides benchmark-focused content and policy context relevant to payer coverage and reimbursement practice nationally, as well as coding nuances that affect claim submission and audit risk. Data not available in the input is noted where applicable.