Chapter 6

G00–G99: Diseases of the Nervous System

Diseases of the Nervous System diagnostic classification updated for 2026.

Chapter Instructions

Excludes2(Not included here. Code separately if applicable.)

certain conditions originating in the perinatal period (P04-P96)
certain infectious and parasitic diseases (A00-B99)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

All Codes Billable Only

Internal Codes

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G25.70|
Drug induced movement disorder, unspecified
G25.71|
Drug induced akathisia
G25.79|
Other drug induced movement disorders
G25.81|
Restless legs syndrome
G25.82|
Stiff-man syndrome
G25.83|
Benign shuddering attacks
G25.89|
Other specified extrapyramidal and movement disorders
G25.9|
Extrapyramidal and movement disorder, unspecified
G26|
Extrapyramidal and movement disorders in diseases classified elsewhere
G30.0|
Alzheimer's disease with early onset
G30.1|
Alzheimer's disease with late onset
G30.8|
Other Alzheimer's disease
G30.9|
Alzheimer's disease, unspecified
G31.01|
Pick's disease
G31.09|
Other frontotemporal neurocognitive disorder
G31.1|
Senile degeneration of brain, not elsewhere classified
G31.2|
Degeneration of nervous system due to alcohol
G31.80|
Leukodystrophy, unspecified
G31.81|
Alpers disease
G31.82|
Leigh's disease
G31.83|
Neurocognitive disorder with Lewy bodies
G31.84|
Mild cognitive impairment of uncertain or unknown etiology
G31.85|
Corticobasal degeneration
G31.86|
Alexander disease
G31.87|
Primary progressive apraxia of speech
G31.89|
Other specified degenerative diseases of nervous system
G31.9|
Degenerative disease of nervous system, unspecified
G32.0|
Subacute combined degeneration of spinal cord in diseases classified elsewhere
G32.81|
Cerebellar ataxia in diseases classified elsewhere
G32.89|
Other specified degenerative disorders of nervous system in diseases classified elsewhere
G35.A|
Relapsing-remitting multiple sclerosis
G35.B0|
Primary progressive multiple sclerosis, unspecified
G35.B1|
Active primary progressive multiple sclerosis
G35.B2|
Non-active primary progressive multiple sclerosis
G35.C0|
Secondary progressive multiple sclerosis, unspecified
G35.C1|
Active secondary progressive multiple sclerosis
G35.C2|
Non-active secondary progressive multiple sclerosis
G35.D|
Multiple sclerosis, unspecified
G36.0|
Neuromyelitis optica [Devic]
G36.1|
Acute and subacute hemorrhagic leukoencephalitis [Hurst]
G36.8|
Other specified acute disseminated demyelination
G36.9|
Acute disseminated demyelination, unspecified
G37.0|
Diffuse sclerosis of central nervous system
G37.1|
Central demyelination of corpus callosum
G37.2|
Central pontine myelinolysis
G37.3|
Acute transverse myelitis in demyelinating disease of central nervous system
G37.4|
Subacute necrotizing myelitis of central nervous system
G37.5|
Concentric sclerosis [Balo] of central nervous system
G37.81|
Myelin oligodendrocyte glycoprotein antibody disease
G37.89|
Other specified demyelinating diseases of central nervous system

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