What is the CPT (Current Procedural Terminology) code for a surgical procedure involving thinning of the bony posterior external auditory canal, entry and enlargement of the antrum, thinning of the sinodural angle, discovery and bipolar reduction of a diverticulum, and placement of a bony plate?

CPT Code for Mastoidectomy with Diverticulum Management

The procedure described is CPT code 69670 (Mastoidectomy, radical; with tympanoplasty) or potentially 69641 (Tympanoplasty without mastoidectomy, with ossicular chain reconstruction), depending on whether ossicular chain reconstruction was performed.

Procedural Analysis

The surgical steps you've described involve several key components that help identify the appropriate CPT code:

Core Procedural Elements

• Thinning of the bony posterior external auditory canal represents canalplasty, which is a component of mastoid surgery 1
• Entry and enlargement of the antrum indicates a formal mastoidectomy was performed, as the antrum is the primary mastoid air cell accessed during this procedure 2
• Thinning of the sinodural angle represents work in the posterior-superior mastoid region where the sigmoid sinus and dura meet 3
• Discovery and bipolar coagulation of a diverticulum likely refers to an internal auditory canal diverticulum, which can occur independent of other pathology and may contain vascular structures 4
• Placement of bony plate suggests reconstruction was performed, possibly over the diverticulum site or as part of canal wall reconstruction 1

CPT Code Selection Algorithm

Primary Consideration: Mastoidectomy Type

If this was a canal wall down (radical) mastoidectomy:

• Use CPT 69670 if tympanoplasty was performed 2
• Use CPT 69645 if no tympanic membrane work was done 2

If this was a canal wall up (intact canal wall) mastoidectomy:

• Use CPT 69641 if ossicular reconstruction occurred 1
• Use CPT 69635 if no ossicular work was performed 2

Key Distinguishing Features

• The description of "thinning the bony posterior external auditory canal" and "bony plate placement" suggests either canal wall reconstruction or canalplasty, which are components of more extensive mastoid procedures 1
• The work at the sinodural angle indicates posterior mastoid dissection beyond simple antrotomy 3
• Management of the diverticulum with bipolar cautery and bone coverage represents additional work that is typically included in the mastoidectomy code but may warrant modifier consideration if unusually extensive 4

Clinical Context Considerations

• Internal auditory canal diverticula occur in approximately 25-70% of temporal bones and can contain vascular structures requiring careful management 4
• The diverticulum management described (bipolar coagulation and bone coverage) represents standard neurotologic technique for vascular control during mastoid surgery 5
• Documentation should specify whether the tympanic membrane was addressed, whether ossicular chain work was performed, and whether the canal wall was preserved or removed to ensure accurate coding 2, 6

Common Coding Pitfalls

• Do not separately code the canalplasty, as it is included in the mastoidectomy code 1
• Do not separately code the diverticulum management unless it represents a distinct, separately identifiable procedure requiring significantly additional work 5
• Ensure documentation clearly describes the extent of mastoid work, as incomplete documentation may result in downcoding to a simpler procedure 2