Version 2024

2024 ICD-10-CM Diagnosis Code S04.21

Injury of trochlear nerve, right side

ICD-10-CM Code:
S04.21
Short Description:
Injury of trochlear nerve, right side
Is Billable?
Not Valid for Submission
Code Navigator:

Code Classification

  • Injury, poisoning and certain other consequences of external causes
    (S00–T88)
    • Injuries to the head
      (S00-S09)
      • Injury of cranial nerve
        (S04)

S04.21 is a non-specific and non-billable diagnosis code code, consider using a code with a higher level of specificity for a diagnosis of injury of trochlear nerve, right side. The code is not specific and is NOT valid for the year 2024 for the submission of HIPAA-covered transactions. Category or Header define the heading of a category of codes that may be further subdivided by the use of 4th, 5th, 6th or 7th characters.

Specific Coding Applicable to Injury of trochlear nerve, right side

Non-specific codes like S04.21 require more digits to indicate the appropriate level of specificity. Consider using any of the following ICD-10-CM codes with a higher level of specificity when coding for injury of trochlear nerve, right side:

  • Use S04.21XA for initial encounter - BILLABLE CODE

  • Use S04.21XD for subsequent encounter - BILLABLE CODE

  • Use S04.21XS for sequela - BILLABLE CODE

Coding Guidelines

The appropriate 7th character is to be added to each code from block Injury of cranial nerve (S04). Use the following options for the aplicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Patient Education


Eye Movement Disorders

When you look at an object, you're using several muscles to move both eyes to focus on it. If you have a problem with the muscles, the eyes don't work properly.

There are many kinds of eye movement disorders. Two common ones are:

  • Strabismus - a disorder in which the two eyes don't line up in the same direction. This results in "crossed eyes" or "walleye."
  • Nystagmus - fast, uncontrollable movements of the eyes, sometimes called "dancing eyes"

Some eye movement disorders are present at birth. Others develop over time and may be associated with other problems, such as injuries. Treatments include glasses, patches, eye muscle exercises, and surgery. There is no cure for some kinds of eye movement disorders, such as most kinds of nystagmus.


[Learn More in MedlinePlus]

Code History

  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.