2026 ICD-10-CM Diagnosis Code S44.42XAInjury of musculocutaneous nerve, left arm, initial encounter
S44.42XA is a billable ICD-10-CM diagnosis code for injury of musculocutaneous nerve, left arm, 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. Coders also document this condition as injury of left musculocutaneous nerve. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Injury to nerves, muscles and tendons, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Injury of left musculocutaneous nerve
- Injury of musculocutaneous nerve
- Musculocutaneous nerve lesion
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Injury of nerves at shoulder and upper arm level (S44). 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.
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 S44.42XA to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S44.42XAOverview
Is S44.42XA (Injury of musculocutaneous nerve, left arm) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report injury of musculocutaneous nerve, left arm, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S44.42XA mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for injury of musculocutaneous nerve, left arm, such as an emergency visit or first evaluation.
What MS-DRG does S44.42XA group to?
When injury of musculocutaneous nerve, left arm, 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 S44.42XA?
Under the General Equivalence Mappings, injury of musculocutaneous nerve, left arm, initial encounter converts to ICD-9-CM 955.4 (inj musculocutan nerve). 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.
