S04.21 ICD-10-CM Code: Injury of trochlear nerve, right side
S04.21 is the authoritative medical code for Injury of trochlear nerve, right side. This classification is used in medical billing and clinical recording to specify the clinical criteria for injury of trochlear nerve, right side (ICD-10-CM S04.21), ensuring healthcare documentation aligns with current federal coding standards.
Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.
Code Set: Valid FY2026 and FY2027. FY2026 took effect October 1, 2025.
Official Registry Overview & Definition
Official Tabular Instructional Notes
Sequencing, inclusion, and exclusion notes published for S04.21 in the official ICD-10-CM tabular list.
Includes
Conditions the official ICD-10-CM tabular list includes under this code.
- injuries of ear
- injuries of eye
- injuries of face [any part]
- injuries of gum
- injuries of jaw
- injuries of oral cavity
- injuries of palate
- injuries of periocular area
- injuries of scalp
- injuries of temporomandibular joint area
- injuries of tongue
- injuries of tooth
Excludes2 — Not Included Here
Conditions not covered by this code, but which may be reported alongside it when both are present.
- burns and corrosions (T20-T32)
- effects of foreign body in ear (T16)
- effects of foreign body in larynx (T17.3)
- effects of foreign body in mouth NOS (T18.0)
- effects of foreign body in nose (T17.0-T17.1)
- effects of foreign body in pharynx (T17.2)
- effects of foreign body on external eye (T15.-)
- frostbite (T33-T34)
- insect bite or sting, venomous (T63.4)
Code First
Underlying conditions that must be sequenced before this code.
- any associated intracranial injury (S06.-)
Code Also
Additional codes that may be required to fully describe the encounter.
- any associated:
- open wound of head (S01.-)
- skull fracture (S02.-)
- for any associated infection
Frequently Asked Questions (FAQ) & Clinical Guidance
Can S04.21 be billed directly?
No. S04.21 (Injury of trochlear nerve, right side) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.
Does S04.21 require a 7th character?
Yes. The appropriate 7th character is to be added to each code from category S04.
Can S04.21 be reported alongside related conditions?
Per official ICD-10-CM Excludes2 instructions, S04.21 and the following are not considered part of each other and may both be reported when both conditions are present: burns and corrosions (T20-T32); effects of foreign body in ear (T16); effects of foreign body in larynx (T17.3); effects of foreign body in mouth NOS (T18.0).
Does S04.21 need to be sequenced after another code?
Yes. Code first: any associated intracranial injury (S06.-).
Nearest Codes in This Family
Official ICD-10-CM classifications closest to S04.21 in its code family, with their registry titles.
- S04.2 — Injury of trochlear nerve
- S04.20 — Injury of trochlear nerve, unspecified side
- S04.20XA — Injury of trochlear nerve, unspecified side, initial encounter
- S04.20XD — Injury of trochlear nerve, unspecified side, subsequent encounter
- S04.20XS — Injury of trochlear nerve, unspecified side, sequela
- S04.21XA — Injury of trochlear nerve, right side, initial encounter
- S04.21XD — Injury of trochlear nerve, right side, subsequent encounter
- S04.21XS — Injury of trochlear nerve, right side, sequela
- S04.22 — Injury of trochlear nerve, left side
- S04.22XA — Injury of trochlear nerve, left side, initial encounter