2026 ICD-10-CM Diagnosis Code G99.8Other specified disorders of nervous system in diseases classified elsewhere
ICD-10-CM Codes›G00–G99›G89-G99›G99
- Billable — Valid for Submission
- Not Chronic
G99.8 is a billable ICD-10-CM diagnosis code for other specified disorders of nervous system in diseases classified elsewhere. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as neurologic disorder due to degeneration of lumbar intervertebral disc. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other nervous system disorders (neither hereditary nor degenerative).
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for G99.8.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Neurologic disorder due to degeneration of lumbar intervertebral disc
- Neuroschistosomiasis
- Peripheral neuropathy due to metabolic disorder
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Code First
Type 1 Excludes
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Neuroschistosomiasis
schistosomiasis of the brain, spinal cord, or meninges caused by infections with trematodes of the genus schistosoma (primarily schistosoma japonicum; schistosoma mansoni; and schistosoma haematobium in humans). s. japonicum infections of the nervous system may cause an acute meningoencephalitis or a chronic encephalopathy. s. mansoni and s. haematobium nervous system infections are associated with acute transverse myelitis involving the lower portions of the spinal cord. (from joynt, clinical neurology, 1998, ch27, pp61-2)
Patient EducationClinical
Neurologic Diseases
The brain, spinal cord, and nerves make up the nervous system. Together they control all the workings of the body. When something goes wrong with a part of your nervous system, you can have trouble moving, speaking, swallowing, breathing, or learning. You can also have problems with your memory, senses, or mood.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert G99.8 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About G99.8Overview
Is G99.8 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other specified disorders of nervous system in diseases classified elsewhere on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Can G99.8 be a principal diagnosis?
No. This is a manifestation code: other specified disorders of nervous system in diseases classified elsewhere describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.
What is the ICD-9 equivalent of G99.8?
Under the General Equivalence Mappings, other specified disorders of nervous system in diseases classified elsewhere converts to ICD-9-CM 349.89 (cns disorder NEC). 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.
