ICD-10-CM Code First Notes · Chapter 6 · FY 2027 G00-G99

Code First Notes in Chapter 6: Diseases of the nervous system ICD-10-CM

A Code First note means the underlying condition named in the note is sequenced before this code. In Chapter 6 (G00-G99), notes printed in the chapter name other codes 67 times, and Code First Notes anywhere in the Tabular List name the chapter’s codes 23 times, covering 15 distinct codes, categories and ranges. Switch views to read the list either way.

✓ From the official FY 2027 ICD-10-CM Tabular ListDefinitions follow the Official Guidelines, Section I.A
67
References in Its Notes
23
References to Its Codes
15
Chapter Codes Named
G00-G99
Chapter 6
Chapter 6

Code First Notes by the code that carries the note

29 of 29 shown
  • G02 Meningitis in other infectious and parasitic diseases classified elsewhere
    • African trypanosomiasis (B56.-)
    • poliovirus infection (A80.-)
  • G05 Encephalitis, myelitis and encephalomyelitis in diseases classified elsewhere applies to 2 codes
    • congenital toxoplasmosis encephalitis, myelitis and encephalomyelitis (P37.1)
    • cytomegaloviral encephalitis, myelitis and encephalomyelitis (B25.8)
    • encephalitis, myelitis and encephalomyelitis (in) systemic lupus erythematosus (M32.19)
    • eosinophilic meningoencephalitis (B83.2)
    • human immunodeficiency virus [HIV] disease (B20)
    • poliovirus (A80.-)
    • suppurative otitis media (H66.01-H66.4)
    • systemic lupus erythematosus (M32.19)
    • trichinellosis (B75)
  • G07 Intracranial and intraspinal abscess and granuloma in diseases classified elsewhere
    • schistosomiasis granuloma of brain (B65.-)
  • G13.0 Paraneoplastic neuromyopathy and neuropathy
  • G13.1 Other systemic atrophy primarily affecting central nervous system in neoplastic disease
  • G13.2 Systemic atrophy primarily affecting the central nervous system in myxedema
    • hypothyroidism (E03.-)
    • myxedematous congenital iodine deficiency (E00.1)
  • G21.2 Secondary parkinsonism due to other external agents
    • (T51-T65) to identify external agent
  • G32.0 Subacute combined degeneration of spinal cord in diseases classified elsewhere
    • other dietary vitamin B12 deficiency anemia (D51.3)
    • vitamin B12 deficiency anemia due to intrinsic factor deficiency (D51.0)
    • vitamin B12 deficiency anemia, unspecified (D51.8)
    • vitamin B12 deficiency (E53.8)
  • G32.8 Other specified degenerative disorders of nervous system in diseases classified elsewhere applies to 2 codes
    • amyloidosis cerebral degeneration (E85.-)
    • cerebral degeneration (due to) hypothyroidism (E00.0-E03.9)
    • cerebral degeneration (due to) neoplasm (C00-D49)
    • cerebral degeneration (due to) vitamin B deficiency, except thiamine (E52-E53.-)
  • G32.81 Cerebellar ataxia in diseases classified elsewhere
    • celiac disease (with gluten ataxia) (K90.0)
    • cerebellar ataxia (in) neoplastic disease (paraneoplastic cerebellar degeneration) (C00-D49)
    • non-celiac gluten ataxia (M35.9)
  • G46 Vascular syndromes of brain in cerebrovascular diseases applies to 9 codes
    • underlying cerebrovascular disease (I60-I69)
  • G53 Cranial nerve disorders in diseases classified elsewhere
  • G55 Nerve root and plexus compressions in diseases classified elsewhere
  • G62.2 Polyneuropathy due to other toxic agents
    • (T51-T65) to identify toxic agent
  • G63 Polyneuropathy in diseases classified elsewhere
  • G70.1 Toxic myoneural disorders
    • (T51-T65) to identify toxic agent
  • G72.2 Myopathy due to other toxic agents
    • (T51-T65) to identify toxic agent
  • G73.1 Lambert-Eaton syndrome in neoplastic disease
  • G73.3 Myasthenic syndromes in other diseases classified elsewhere
  • G73.7 Myopathy in diseases classified elsewhere
  • G90.81 Serotonin syndrome
    • linezolid (T36.8X- with sixth character 1-4)
    • monoamine oxidase inhibitors (T43.1X with sixth character 1-4)
    • selective serotonin and norepinephrine reuptake inhibitors [SSNRI] (T43.21 with sixth character 1-4)
    • selective serotonin reuptake inhibitors [SSRI] (T43.22 with sixth character 1-4)
  • G91.4 Hydrocephalus in diseases classified elsewhere
  • G92.0 Immune effector cell-associated neurotoxicity syndrome applies to 6 codes
    • complications of immune effector cellular therapy (T80.82)
  • G92.8 Other toxic encephalopathy
    • poisoning due to drug or toxin, if applicable, (T36-T65 with fifth or sixth character 1-4)
  • G92.9 Unspecified toxic encephalopathy
    • poisoning due to drug or toxin, if applicable, (T36-T65 with fifth or sixth character 1-4)
  • G93.7 Reye's syndrome
    • poisoning due to salicylates, if applicable (T39.0-, with sixth character 1-4)
  • G99.0 Autonomic neuropathy in diseases classified elsewhere
  • G99.2 Myelopathy in diseases classified elsewhere
  • G99.8 Other specified disorders of nervous system in diseases classified elsewhere

The first view lists notes printed in this chapter (a note on a category or block applies to every code beneath it). The second lists codes of this chapter named by Code First Notes anywhere in the Tabular List, including notes in other chapters.

Questions About Code First Notes

What does a Code First note mean?

A Code First note means the underlying condition named in the note is sequenced before the code that carries the note. Under the etiology/manifestation convention, a “code first” note appears at the manifestation code and a “use additional code” note at the etiology code (Section I.A.13). The FY 2027 Tabular List has 810 of them; 600 name other codes, with 736 references to 429 distinct codes, categories and ranges.

Can a code with a Code First note be the principal diagnosis?

Not when it is a manifestation code. Codes titled “in diseases classified elsewhere” are never permitted as the first-listed or principal diagnosis; they must follow the underlying condition. The etiology and manifestation page lists them all.

Related References

ICD-10-CM Official GuidelinesICD-10-CM Code LookupICD-10-CM Codes ListCode Lists by Tag

Source: FY 2027 ICD-10-CM Tabular List (CMS and NCHS) and the ICD-10-CM Official Guidelines for Coding and Reporting FY 2027, Section I.A. ICD List is not affiliated with CMS or NCHS.