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)
Internal Codes
  • 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

    Other degenerative disorders of nervous system in diseases classified elsewhere

  • G32.0

    Subacute combined degeneration of spinal cord in diseases classified elsewhere

  • G32.8

    Other specified degenerative disorders of nervous system 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

    Multiple sclerosis

  • G35.A

    Relapsing-remitting multiple sclerosis

  • G35.B

    Primary progressive 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.C

    Secondary 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

    Other acute disseminated demyelination

  • 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

    Other demyelinating diseases of central nervous system

  • 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

  • G37.8

    Other specified demyelinating diseases of central nervous system

  • G37.81

    Myelin oligodendrocyte glycoprotein antibody disease

  • G37.89

    Other specified demyelinating diseases of central nervous system

  • G37.9

    Demyelinating disease of central nervous system, unspecified

  • G40

    Epilepsy and recurrent seizures

  • G40.0

    Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset

  • G40.00

    Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable

  • G40.001

    Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, with status epilepticus

  • G40.009

    Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, without status epilepticus

  • G40.01

    Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable

  • G40.011

    Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable, with status epilepticus

  • G40.019

    Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable, without status epilepticus

  • G40.1

    Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures

  • G40.10

    Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable

  • G40.101

    Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, with status epilepticus

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