N129 – Posterior fossa decompression for Arnold Chiari malformation
OHIP Otolaryngology Code — NEUROLOGICAL SURGICAL PROCEDURES · Schedule of Benefits
Posterior fossa decompression for Arnold Chiari malformation. This is a surgical procedure performed under the 'Cranial' subsection of Neurological Surgical Procedures. The service fee includes payment for the surgeon (A), assistant (B), and anaesthetist (C). For assistant services (N129B), 15 base units are assigned. For anaesthesia services (N129C), 15 base units are assigned. The use of an operating microscope can be claimed separately with add-on code E901.
When to Use
- Use N129 for the definitive surgical decompression of the posterior fossa specifically indicated for symptomatic Arnold-Chiari malformation.
- Use N129 when the procedure involves craniectomy and/or laminectomy for decompression, distinguishing it from general spinal decompression codes like N027 or N028.
Common Pitfalls
- Failing to claim E901 on the same claim as N129 when an operating microscope is utilized, as it is not automatically bundled into the base fee.
- Attempting to bill N129B or N129C in addition to other surgical assistant or anaesthesia units when multiple procedures are performed; only the major procedure units are eligible.
Billing Tips
- Ensure the operating microscope add-on E901 is explicitly linked to the N129 service line to avoid rejection for missing the required base procedure.
- Apply the appropriate age-based percentage premium to the surgeon, assistant, and anaesthetist fees if the patient is under 16 years of age, as these are not automatically calculated.
Effective: April 1, 2026
X. Neurological Surgical Procedures
NEUROLOGICAL SURGICAL PROCEDURES
Surgical
Neurological Surgical Procedures
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