ICD-10-CM diagnosis code
S04.21XS Injury of trochlear nerve, right side, sequela
- Billable
- Yes, a complete code (FY2026)
- Category
- S04 Injury of cranial nerves
Encounter (7th character)
This code is for a sequela: a complication or condition that arises as a direct result of the injury. The sequela itself is usually coded first, followed by this code.
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Other codes in S04
114 complete codes in this category.
- S04.12XSInjury of oculomotor nerve, left side, sequela
- S04.20XAInjury of trochlear nerve, unspecified side, initial encounter
- S04.20XDInjury of trochlear nerve, unspecified side, subsequent encounter
- S04.20XSInjury of trochlear nerve, unspecified side, sequela
- S04.21XAInjury of trochlear nerve, right side, initial encounter
- S04.21XDInjury of trochlear nerve, right side, subsequent encounter
- S04.21XSInjury of trochlear nerve, right side, sequela
- S04.22XAInjury of trochlear nerve, left side, initial encounter
- S04.22XDInjury of trochlear nerve, left side, subsequent encounter
- S04.22XSInjury of trochlear nerve, left side, sequela
- S04.30XAInjury of trigeminal nerve, unspecified side, initial encounter
- S04.30XDInjury of trigeminal nerve, unspecified side, subsequent encounter
Documentation tips
- Make sure the note supports every element of the title, “Injury of trochlear nerve, right side, sequela”: each detail in it should be traceable to the history, examination or assessment.
- Code to the highest specificity the documentation supports. If a detail is missing from the note, add it to the note rather than choosing a less specific code by default.
- Check the Tabular List and official guidelines for instructional notes (“code first”, “use additional code”, Excludes1/Excludes2) that apply to S04.
The international WHO ICD-10 also has S04, with its inclusion and exclusion notes; titles and detail can differ from ICD-10-CM.
ICD-10-CM is developed by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, and is based on the WHO ICD-10. Codes and titles are reproduced unchanged from the FY2026 code list (effective 1 October 2025). Their use here does not imply endorsement by CDC, HHS or the U.S. Government. Changes effective on or after 1 October 2026 may not be reflected yet; check the current release at cdc.gov or cms.gov before submitting claims.
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