S04.21XA — Injury of trochlear nerve, right side, initial encounter
Is S04.21XA billable?
Yes — S04.21XA is billable for FY2027. S04.21XA is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. S04.21XA may be submitted for encounters from October 1, 2026 through September 30, 2027.
S04.21XA at a glance
| Code | S04.21XA |
|---|---|
| Description | Injury of trochlear nerve, right side, initial encounter |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
| 7th character "A" | initial encounter |
What does the 7th character "A" mean in S04.21XA?
In S04.21XA, the 7th character A means initial encounter. The 7th character is required for S04.21XA to be a valid, complete code.
Same condition, different episode of care — switch the 7th character:
Which MS-DRGs does S04.21XA group to?
S04.21XA sits in MDC 01 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 073Cranial and Peripheral Nerve Disorders with MCCmedical
- 074Cranial and Peripheral Nerve Disorders without MCCmedical
As a secondary diagnosis, S04.21XA is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is S04.21XA listed in the Alphabetic Index?
The Alphabetic Index lists these routes under S04.2, the nearest indexed parent of S04.21XA. Use them to find the family, then select the specific code.
- Injury › nerve NEC › trochlear
- Injury › nerve NEC › trochlear › contusion
- Injury › nerve NEC › trochlear › laceration
- Injury › nerve NEC › trochlear › specified type NEC
Code first — inherited from S04
The underlying condition below must be sequenced before S04.21XA. S04.21XA describes a manifestation and cannot be the principal or first-listed diagnosis.
- any associated intracranial injury (S06.-)
Use additional code — inherited from Chapter 19
Report an additional code alongside S04.21XA to fully describe the condition. S04.21XA is sequenced first.
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes2 — not included here — inherited from Chapter 19
The conditions below are not part of S04.21XA, but a patient may have both at the same time. When documentation supports it, S04.21XA and the excluded code may both be reported.
Excludes2 — not included here — inherited from S00-S09
The conditions below are not part of S04.21XA, but a patient may have both at the same time. When documentation supports it, S04.21XA and the excluded code may both be reported.
- 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 also — inherited from S00-S09
Two codes may be needed to describe the condition fully. Whether S04.21XA is sequenced first depends on the reason for the encounter.
- for any associated infection
Code also — inherited from S04
Two codes may be needed to describe the condition fully. Whether S04.21XA is sequenced first depends on the reason for the encounter.
How long has S04.21XA existed?
S04.21XA has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.