2027 ICD-10-CM Diagnosis Code S04.811AInjury of olfactory [1st ] nerve, right side, initial encounter

ICD-10-CM Codes›S00–T88›S00-S09›S04

ICD-10-CM S04.811A
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

S04.811A is a billable ICD-10-CM diagnosis code for injury of olfactory [1st ] nerve, right side, 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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 73 through 74, 963 through 965. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 7 closely related codes. 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
S04.811A
Billable Status
Yes — Valid for Submission
Code Describes
Injury of olfactory [1st ] nerve, right side, initial encounter
Short Description
Injury of olfactory nerve, right side, initial encounter
Parent Code
S04.811
Injury of olfactory [1st ] nerve, right side

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS00-S09Injuries to the head
CategoryS04Injury of cranial nerve
This CodeS04.811AInjury of olfactory [1st ] nerve, right side, initial encounter

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 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to S04.811A: its own notes plus those printed at S04, block S00-S09, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block S00-S09 Injuries to the head applies to 1,934 codes
  • 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: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block S00-S09 Injuries to the head applies to 1,934 codes
  • 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)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Code First

The underlying condition named in the note is sequenced before this code.

From S04 Injury of cranial nerve applies to 114 codes
  • any associated intracranial injury (S06.-)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From S04 Injury of cranial nerve applies to 114 codes
  • any associated:
  • open wound of head (S01.-)
  • skull fracture (S02.-)
From Block S00-S09 Injuries to the head applies to 1,934 codes
  • for any associated infection

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From S04 Injury of cranial nerve applies to 114 codes
  • The appropriate 7th character is to be added to each code from category S04
Values for category S04 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name S04.811A, its category, or a range that includes it.

Code Also 1

These codes say S04.811A may also be needed to fully describe the condition. The note gives no sequencing direction.

  • S01 Open wound of head
    injury of cranial nerve (S04.-) names S04.-, which includes this code

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 S04.811A to ICD-9-CMHistory

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

ICD-9-CM
951.8 Injury cranial nerve NEC
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About S04.811AOverview

What is the ICD-10 code for injury of olfactory [1st ] nerve, right side, initial encounter?

The ICD-10-CM code for injury of olfactory [1st ] nerve, right side, initial encounter is S04.811A (sometimes written as S04811A). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is S04.811A (Injury of olfactory [1st ] nerve, right side) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report injury of olfactory [1st ] nerve, right side, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in S04.811A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for injury of olfactory [1st ] nerve, right side, such as an emergency visit or first evaluation.

What MS-DRG does S04.811A group to?

When injury of olfactory [1st ] nerve, right side, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 964, 965, 74, 73, 963, with relative weights from 1.0054 to 2.6361 depending on complications. Higher weights mean higher Medicare reimbursement.

Is S04.811A a CC or MCC?

CMS lists S04.811A as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 7 closely related codes in its exclusion list.