2026 ICD-10-CM Diagnosis Code S04.9XXAInjury of unspecified cranial nerve, initial encounter

ICD-10-CM Codes›S00–T88›S00-S09›S04

ICD-10-CM S04.9XXA
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S04.9XXA is a billable ICD-10-CM diagnosis code for injury of unspecified cranial nerve, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 963 through 965. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Injury to nerves, muscles and tendons, initial encounter.

Code Identity

ICD-10-CM Code
S04.9XXA
Billable Status
Yes — Valid for Submission
Code Describes
Injury of unspecified cranial nerve, initial encounter
Short Description
Injury of unspecified cranial nerve, initial encounter
Same as the full description in the CMS dataset.
Parent Code
S04.9
Injury of unspecified cranial nerve

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS00-S09Injuries to the head
CategoryS04Injury of cranial nerve
This CodeS04.9XXAInjury of unspecified cranial nerve, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Avulsion of cranial nerve
  • Chemical cranial nerve injury
  • Complete division of cranial nerve
  • Contusion of cranial nerve
  • Cranial nerve compression
  • Injuries of brain and cranial nerves with injuries of nerves and spinal cord at neck level
  • Injury of cranial nerve
  • Injury of superficial nerves of head AND/OR neck
  • Multiple injuries of vertebral column region
  • Multiple intracranial injuries
  • Partial division of cranial nerve
  • Thermal injury of cranial nerve
  • Traction injury of cranial nerve

Coding GuidelinesGuidance

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

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

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ025
Injury to nerves, muscles and tendons, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Peripheral Nerve Disorders

Nerves are like wires that carry messages back and forth between your brain and your body. Your peripheral nerves branch off from your brain and spinal cord and connect to all parts of your body, including your muscles and organs.

The full article covers:

  • What are peripheral nerves?
  • What are peripheral nerve disorders?
  • What causes peripheral nerve disorders?
  • What are the symptoms of peripheral nerve disorders?
  • How are peripheral nerve disorders diagnosed?
  • What are the treatments for peripheral nerve disorders?
  • Can peripheral nerve disorders be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert S04.9XXA to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
951.9 Injury cranial nerve NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About S04.9XXAOverview

Is S04.9XXA (Injury of unspecified cranial nerve) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report injury of unspecified cranial nerve, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in S04.9XXA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for injury of unspecified cranial nerve, such as an emergency visit or first evaluation.

What MS-DRG does S04.9XXA group to?

When injury of unspecified cranial nerve, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 963, 964, 965, with relative weights from 0.9405 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of S04.9XXA?

Under the General Equivalence Mappings, injury of unspecified cranial nerve, initial encounter converts to ICD-9-CM 951.9 (injury cranial nerve NOS). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.