2024 ICD-10-CM Diagnosis Code G04.90

Encephalitis and encephalomyelitis, unspecified

ICD-10-CM Code:
ICD-10 Code for:
Encephalitis and encephalomyelitis, unspecified
Is Billable?
Yes - Valid for Submission
Chronic Condition Indicator: [1]
Not chronic
Code Navigator:

Code Classification

  • Diseases of the nervous system
    • Inflammatory diseases of the central nervous system
      • Encephalitis, myelitis and encephalomyelitis

G04.90 is a billable diagnosis code used to specify a medical diagnosis of encephalitis and encephalomyelitis, unspecified. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2023 through September 30, 2024.

Unspecified diagnosis codes like G04.90 are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Acute encephalitis
  • Autonomic disorder due to encephalitis
  • Bacterial ventriculitis
  • Brainstem encephalitis
  • Chorea due to and following encephalitis
  • Dystonia due to encephalitis
  • Encephalitis
  • Encephalitis, myelitis and encephalomyelitis
  • Encephalomyelitis
  • Encephalomyelitis caused by bacterium
  • Encephalomyelitis caused by Burkholderia
  • Ependymitis
  • Epilepsy due to infectious disease of central nervous system
  • Epilepsy due to infectious encephalitis
  • Focal encephalitis
  • Granular ependymitis
  • Infection caused by Mycoplasma pneumoniae
  • Infection causing encephalomyelitis
  • Infection causing encephalomyelitis
  • Infection causing encephalomyelitis
  • Infectious disease of brain
  • Infective encephalitis
  • Infective ventriculitis
  • Infective ventriculitis
  • Malignant ventriculitis
  • Meningoencephalitis
  • Meningoencephalomyelitis
  • Meningomyelitis
  • Mycoplasma pneumoniae encephalitis
  • Myelitis caused by bacterium
  • Myelitis caused by bacterium
  • Primary encephalitis
  • Seizures complicating infection
  • Situation-related seizures
  • Ventriculitis of the brain

Clinical Classification

Clinical Information

  • Anti-N-Methyl-D-Aspartate Receptor Encephalitis

    disorder characterized by symptoms of catatonia; hypoventilation; dyskinesias; encephalitis; and seizures followed by a reduced consciousness. it is often followed by a viral-like prodrome. many cases are self-limiting and respond well to immunomodulatory therapies against the nmda receptors antibodies.
  • Ascaridida Infections

    infections with nematodes of the order ascaridida.
  • Autoimmune Diseases of the Nervous System

    disorders caused by cellular or humoral immune responses primarily directed towards nervous system autoantigens. the immune response may be directed towards specific tissue components (e.g., myelin) and may be limited to the central nervous system (e.g., multiple sclerosis) or the peripheral nervous system (e.g., guillain-barre syndrome).
  • Diffuse Cerebral Sclerosis of Schilder

    a rare central nervous system demyelinating condition affecting children and young adults. pathologic findings include a large, sharply defined, asymmetric focus of myelin destruction that may involve an entire lobe or cerebral hemisphere. the clinical course tends to be progressive and includes dementia, cortical blindness, cortical deafness, spastic hemiplegia, and pseudobulbar palsy. concentric sclerosis of balo is differentiated from diffuse cerebral sclerosis of schilder by the pathologic finding of alternating bands of destruction and preservation of myelin in concentric rings. alpers' syndrome refers to a heterogeneous group of diseases that feature progressive cerebral deterioration and liver disease. (from adams et al., principles of neurology, 6th ed, p914; dev neurosci 1991;13(4-5):267-73)
  • Encephalitis

    inflammation of the brain due to infection, autoimmune processes, toxins, and other conditions. viral infections (see encephalitis, viral) are a relatively frequent cause of this condition.
  • Encephalitis Virus, California

    a species in the orthobunyavirus genus of the family bunyaviridae. serotypes are found in temperate and arctic regions and each is closely associated with a single species of vector mosquito. the vertebrate hosts are usually small mammals but several serotypes infect humans.
  • Encephalitis Virus, Eastern Equine

    a species of alphavirus causing encephalomyelitis in equidae and humans. the virus ranges along the atlantic seaboard of the united states and canada and as far south as the caribbean, mexico, and parts of central and south america. infections in horses show a mortality of up to 90 percent and in humans as high as 80 percent in epidemics.
  • Encephalitis Virus, Japanese

    a species of flavivirus, one of the japanese encephalitis virus group (encephalitis viruses, japanese), which is the etiological agent of japanese encephalitis found in asia, southeast asia, and the indian subcontinent.
  • Encephalitis Virus, Murray Valley

    a species of flavivirus, one of the japanese encephalitis virus group (encephalitis viruses, japanese), found in australia and new guinea. it causes a fulminating viremia resembling japanese encephalitis (encephalitis, japanese).
  • Encephalitis Virus, St. Louis

    a species of flavivirus, one of the japanese encephalitis virus group (encephalitis viruses, japanese), which is the etiologic agent of st. louis encephalitis in the united states, the caribbean, and central and south america.
  • Encephalitis Virus, Venezuelan Equine

    a species of alphavirus that is the etiologic agent of encephalomyelitis in humans and equines. it is seen most commonly in parts of central and south america.
  • Encephalitis Virus, Western Equine

    a species of alphavirus that is the etiologic agent of encephalomyelitis in humans and equines in the united states, southern canada, and parts of south america.
  • Encephalitis Viruses

    a collection of single-stranded rna viruses scattered across the bunyaviridae, flaviviridae, and togaviridae families whose common property is the ability to induce encephalitic conditions in infected hosts.
  • Encephalitis Viruses, Japanese

    a subgroup of the genus flavivirus which comprises a number of viral species that are the etiologic agents of human encephalitis in many different geographical regions. these include japanese encephalitis virus (encephalitis virus, japanese), st. louis encephalitis virus (encephalitis virus, st. louis), murray valley encephalitis virus (encephalitis virus, murray valley), and west nile virus.
  • Encephalitis Viruses, Tick-Borne

    a subgroup of the genus flavivirus that causes encephalitis and hemorrhagic fevers and is found in eastern and western europe and the former soviet union. it is transmitted by ticks and there is an associated milk-borne transmission from viremic cattle, goats, and sheep.
  • Encephalitis, Arbovirus

    infections of the brain caused by arthropod-borne viruses (i.e., arboviruses) primarily from the families togaviridae; flaviviridae; bunyaviridae; reoviridae; and rhabdoviridae. life cycles of these viruses are characterized by zoonoses, with birds and lower mammals serving as intermediate hosts. the virus is transmitted to humans by the bite of mosquitoes (culicidae) or ticks. clinical manifestations include fever, headache, alterations of mentation, focal neurologic deficits, and coma. (from clin microbiol rev 1994 jan;7(1):89-116; walton, brain's diseases of the nervous system, 10th ed, p321)
  • Encephalitis, California

    a viral infection of the brain caused by serotypes of california encephalitis virus (encephalitis virus, california) transmitted to humans by the mosquito aedes triseriatus. the majority of cases are caused by the la crosse virus. this condition is endemic to the midwestern united states and primarily affects children between 5-10 years of age. clinical manifestations include fever; vomiting; headache; and abdominal pain followed by seizures, altered mentation, and focal neurologic deficits. (from joynt, clinical neurology, 1996, ch26, p13)
  • Encephalitis, Herpes Simplex

    an acute (or rarely chronic) inflammatory process of the brain caused by simplexvirus infections which may be fatal. the majority of infections are caused by human herpesvirus 1 (herpesvirus 1, human) and less often by human herpesvirus 2 (herpesvirus 2, human). clinical manifestations include fever; headache; seizures; hallucinations; behavioral alterations; aphasia; hemiparesis; and coma. pathologically, the condition is marked by a hemorrhagic necrosis involving the medial and inferior temporal lobe and orbital regions of the frontal lobe. (from adams et al., principles of neurology, 6th ed, pp751-4)
  • Encephalitis, Japanese

    a mosquito-borne encephalitis caused by the japanese b encephalitis virus (encephalitis virus, japanese) occurring throughout eastern asia and australia. the majority of infections occur in children and are subclinical or have features limited to transient fever and gastrointestinal symptoms. inflammation of the brain, spinal cord, and meninges may occur and lead to transient or permanent neurologic deficits (including a poliomyelitis-like presentation); seizures; coma; and death. (from adams et al., principles of neurology, 6th ed, p751; lancet 1998 apr 11;351(9109):1094-7)
  • Encephalitis, St. Louis

    a viral encephalitis caused by the st. louis encephalitis virus (encephalitis virus, st. louis), a flavivirus. it is transmitted to humans and other vertebrates primarily by mosquitoes of the genus culex. the primary animal vectors are wild birds and the disorder is endemic to the midwestern and southeastern united states. infections may be limited to an influenza-like illness or present as an aseptic meningitis or encephalitis. clinical manifestations of the encephalitic presentation may include seizures, lethargy, myoclonus, focal neurologic signs, coma, and death. (from adams et al., principles of neurology, 6th ed, p750)
  • Encephalitis, Tick-Borne

    encephalitis caused by neurotropic viruses that are transmitted via the bite of ticks. in europe, the diseases are caused by encephalitis viruses, tick-borne, which give rise to russian spring-summer encephalitis, central european encephalitis, louping ill encephalitis, and related disorders. powassan encephalitis occurs in north america and russia and is caused by the powassan virus. aseptic meningitis and rarely encephalitis may complicate colorado tick fever which is endemic to mountainous regions of the western united states. (from joynt, clinical neurology, 1996, ch26, pp14-5)
  • Encephalitis, Varicella Zoster

    inflammation of brain tissue caused by infection with the varicella-zoster virus (herpesvirus 3, human). this condition is associated with immunocompromised states, including the acquired immunodeficiency syndrome. pathologically, the virus tends to induce a vasculopathy and infect oligodendrocytes and ependymal cells, leading to cerebral infarction, multifocal regions of demyelination, and periventricular necrosis. manifestations of varicella encephalitis usually occur 5-7 days after onset of herpes zoster and include headache; vomiting; lethargy; focal neurologic deficits; fever; and coma. (from joynt, clinical neurology, 1996, ch 26, pp29-32; hum pathol 1996 sep;27(9):927-38)
  • Encephalitis, Viral

    inflammation of brain parenchymal tissue as a result of viral infection. encephalitis may occur as primary or secondary manifestation of togaviridae infections; herpesviridae infections; adenoviridae infections; flaviviridae infections; bunyaviridae infections; picornaviridae infections; paramyxoviridae infections; orthomyxoviridae infections; retroviridae infections; and arenaviridae infections.
  • Encephalomyelitis, Acute Disseminated

    an acute or subacute inflammatory process of the central nervous system characterized histologically by multiple foci of perivascular demyelination. symptom onset usually occurs several days after an acute viral infection or immunization, but it may coincide with the onset of infection or rarely no antecedent event can be identified. clinical manifestations include confusion, somnolence, fever, nuchal rigidity, and involuntary movements. the illness may progress to coma and eventually be fatal. (adams et al., principles of neurology, 6th ed, p921)
  • Encephalomyelitis, Eastern Equine

    a form of arboviral encephalitis (primarily affecting equines) endemic to eastern regions of north america. the causative organism (encephalomyelitis virus, eastern equine) may be transmitted to humans via the bite of aedes mosquitoes. clinical manifestations include the acute onset of fever, headache, altered mentation, and seizures followed by coma. the condition is fatal in up to 50% of cases. recovery may be marked by residual neurologic deficits and epilepsy. (from joynt, clinical neurology, 1996, ch26, pp9-10)
  • Encephalomyelitis, Equine

    a group of alphavirus infections which affect horses and man, transmitted via the bites of mosquitoes. disorders in this category are endemic to regions of south america and north america. in humans, clinical manifestations vary with the type of infection, and range from a mild influenza-like syndrome to a fulminant encephalitis. (from joynt, clinical neurology, 1996, ch26, pp8-10)
  • Encephalomyelitis, Venezuelan Equine

    a form of arboviral encephalitis endemic to central america and the northern latitudes of south america. the causative organism (encephalitis virus, venezuelan equine) is transmitted to humans and horses via the bite of several mosquito species. human viral infection may be asymptomatic or remain restricted to a mild influenza-like illness. encephalitis, usually not severe, occurs in a small percentage of cases and may rarely feature seizures and coma. (from joynt, clinical neurology, 1996, ch26, pp9-10)
  • Encephalomyelitis, Western Equine

    a form of arboviral encephalitis (which primarily affects horses) endemic to western and central regions of north america. the causative organism (encephalomyelitis virus, western equine) may be transferred to humans via the bite of mosquitoes (culex tarsalis and others). clinical manifestations include headache and influenza-like symptoms followed by alterations in mentation, seizures, and coma. death occurs in a minority of cases. survivors may recover fully or be left with residual neurologic dysfunction, including parkinsonism, postencephalitic. (from joynt, clinical neurology, 1996, ch26, pp8-9)
  • Encephalopathy, Bovine Spongiform

    a transmissible spongiform encephalopathy of cattle associated with abnormal prion proteins in the brain. affected animals develop excitability and salivation followed by ataxia. this disorder has been associated with consumption of scrapie infected ruminant derived protein. this condition may be transmitted to humans, where it is referred to as variant or new variant creutzfeldt-jakob syndrome. (vet rec 1998 jul 25;143(41):101-5)
  • Henipavirus Infections

    infections with viruses of the genus henipavirus, family paramyxoviridae.
  • Herpesvirus 5, Bovine

    a species of varicellovirus that causes a fatal meningoencephalitis in calves.
  • Infectious Encephalitis

    brain inflammation caused by an infectious agent.
  • Japanese Encephalitis Vaccines

    vaccines or candidate vaccines used to prevent infection with japanese b encephalitis virus (encephalitis virus, japanese).
  • Leukoencephalitis, Acute Hemorrhagic

    a fulminant and often fatal demyelinating disease of the brain which primarily affects young adults and children. clinical features include the rapid onset of weakness, seizures, and coma. it may follow a viral illness or mycoplasma pneumoniae infections but in most instances there is no precipitating event. pathologic examination reveals marked perivascular demyelination and necrosis of white matter with microhemorrhages. (adams et al., principles of neurology, 6th ed, pp924-5)
  • Leukoencephalopathy, Progressive Multifocal

    an opportunistic viral infection of the central nervous system associated with conditions that impair cell-mediated immunity (e.g., acquired immunodeficiency syndrome and other immunologic deficiency syndromes; hematologic neoplasms; immunosuppression; and collagen diseases). the causative organism is jc polyomavirus (jc virus) which primarily affects oligodendrocytes, resulting in multiple areas of demyelination. clinical manifestations include dementia; ataxia; visual disturbances; and other focal neurologic deficits, generally progressing to a vegetative state within 6 months. (from joynt, clinical neurology, 1996, ch26, pp36-7)
  • Limbic Encephalitis

    a paraneoplastic syndrome marked by degeneration of neurons in the limbic system. clinical features include hallucinations, loss of episodic memory; anosmia; ageusia; temporal lobe epilepsy; dementia; and affective disturbance (depression). circulating anti-neuronal antibodies (e.g., anti-hu; anti-yo; anti-ri; and anti-ma2) and small cell lung carcinomas or testicular carcinoma are frequently associated with this syndrome.
  • Neurotoxicity Syndromes

    neurologic disorders caused by exposure to toxic substances through ingestion, injection, cutaneous application, or other method. this includes conditions caused by biologic, chemical, and pharmaceutical agents.
  • Parkinson Disease, Postencephalitic

    parkinsonism following encephalitis, historically seen as a sequella of encephalitis lethargica (von economo encephalitis). the early age of onset, the rapid progression of symptoms followed by stabilization, and the presence of a variety of other neurological disorders (e.g., sociopathic behavior; tics; muscle spasms; oculogyric crises; hyperphagia; and bizarre movements) distinguish this condition from primary parkinson disease. pathologic features include neuronal loss and gliosis concentrated in the mesencephalon; subthalamus; and hypothalamus. (from adams et al., principles of neurology, 6th ed, p754)
  • Poliomyelitis

    an acute infectious disease of humans, particularly children, caused by any of three serotypes of human poliovirus (poliovirus). usually the infection is limited to the gastrointestinal tract and nasopharynx, and is often asymptomatic. the central nervous system, primarily the spinal cord, may be affected, leading to rapidly progressive paralysis, coarse fasciculation and hyporeflexia. motor neurons are primarily affected. encephalitis may also occur. the virus replicates in the nervous system, and may cause significant neuronal loss, most notably in the spinal cord. a rare related condition, nonpoliovirus poliomyelitis, may result from infections with nonpoliovirus enteroviruses. (from adams et al., principles of neurology, 6th ed, pp764-5)
  • Subacute Sclerosing Panencephalitis

    a rare, slowly progressive encephalitis caused by chronic infection with the measles virus. the condition occurs primarily in children and young adults, approximately 2-8 years after the initial infection. a gradual decline in intellectual abilities and behavioral alterations are followed by progressive myoclonus; muscle spasticity; seizures; dementia; autonomic dysfunction; and ataxia. death usually occurs 1-3 years after disease onset. pathologic features include perivascular cuffing, eosinophilic cytoplasmic inclusions, neurophagia, and fibrous gliosis. it is caused by the sspe virus, which is a defective variant of measles virus. (from adams et al., principles of neurology, 6th ed, pp767-8)
  • West Nile Fever

    a mosquito-borne viral illness caused by the west nile virus, a flavivirus and endemic to regions of africa, asia, and europe. common clinical features include headache; fever; maculopapular rash; gastrointestinal symptoms; and lymphadenopathy. meningitis; encephalitis; and myelitis may also occur. the disease may occasionally be fatal or leave survivors with residual neurologic deficits. (from joynt, clinical neurology, 1996, ch26, p13; lancet 1998 sep 5;352(9130):767-71)
  • Betacoronavirus 1

    the type species of betacoronavirus genus causing gastroenteritis respiratory diseases in mammals. previously separate species human coronavirus oc43; bovine coronavirus; human enteric coronavirus; equine coronavirus; and porcine hemagglutinating encephalomyelitis virus merged into this species on the basis of similar genome nucleotide sequence and genome organization.
  • Borna disease virus

    a species in the genus bornavirus, family bornaviridae, causing a rare and usually fatal encephalitic disease in horses and other domestic animals and possibly deer. its name derives from the city in saxony where the condition was first described in 1894, but the disease occurs in europe, n. africa, and the near east.
  • Encephalomyelitis

    a general term indicating inflammation of the brain and spinal cord, often used to indicate an infectious process, but also applicable to a variety of autoimmune and toxic-metabolic conditions. there is significant overlap regarding the usage of this term and encephalitis in the literature.
  • Encephalomyelitis Virus, Avian

    a tentative species in the genus hepatovirus infecting primarily young chicks, but also found in turkeys, pheasants, and guinea fowl. it causes a fatal neuronal degeneration and is transmitted by mechanical contact.
  • Encephalomyelitis, Autoimmune, Experimental

    an experimental animal model for central nervous system demyelinating disease. inoculation with a white matter emulsion combined with freund's adjuvant, myelin basic protein, or purified central myelin triggers a t cell-mediated immune response directed towards central myelin. the pathologic features are similar to multiple sclerosis, including perivascular and periventricular foci of inflammation and demyelination. subpial demyelination underlying meningeal infiltrations also occurs, which is also a feature of encephalomyelitis, acute disseminated. passive immunization with t-cells from an afflicted animal to a normal animal also induces this condition. (from immunol res 1998;17(1-2):217-27; raine cs, textbook of neuropathology, 2nd ed, p604-5)
  • Encephalomyelitis, Enzootic Porcine

    a picornavirus infection producing symptoms similar to poliomyelitis in pigs.
  • Fatigue Syndrome, Chronic

    a syndrome characterized by persistent or recurrent fatigue, diffuse musculoskeletal pain, sleep disturbances, and subjective cognitive impairment of 6 months duration or longer. symptoms are not caused by ongoing exertion; are not relieved by rest; and result in a substantial reduction of previous levels of occupational, educational, social, or personal activities. minor alterations of immune, neuroendocrine, and autonomic function may be associated with this syndrome. there is also considerable overlap between this condition and fibromyalgia. (from semin neurol 1998;18(2):237-42; ann intern med 1994 dec 15;121(12): 953-9)
  • Leigh Disease

    a group of metabolic disorders primarily of infancy characterized by the subacute onset of psychomotor retardation, hypotonia, ataxia, weakness, vision loss, eye movement abnormalities, seizures, dysphagia, and lactic acidosis. pathological features include spongy degeneration of the neuropile of the basal ganglia, thalamus, brain stem, and spinal cord. patterns of inheritance include x-linked recessive, autosomal recessive, and mitochondrial. leigh disease has been associated with mutations in genes for the pyruvate dehydrogenase complex; cytochrome-c oxidase; atp synthase subunit 6; and subunits of mitochondrial complex i. (from menkes, textbook of child neurology, 5th ed, p850).
  • Lymphocytic Choriomeningitis

    a form of meningitis caused by lymphocytic choriomeningitis virus. mice and other rodents serve as the natural hosts, and infection in humans usually occurs through inhalation or ingestion of infectious particles. clinical manifestations include an influenza-like syndrome followed by stiff neck, alterations of mentation, ataxia, and incontinence. maternal infections may result in fetal malformations and injury, including neonatal hydrocephalus, aqueductal stenosis, chorioretinitis, and microcephaly. (from joynt, clinical neurology, 1996, ch26, pp1-3)
  • Maus Elberfeld virus

    a strain of encephalomyocarditis virus, a species of cardiovirus, usually causing an inapparent intestinal infection in mice. a small number of mice may show signs of flaccid paralysis.
  • Paraneoplastic Syndromes, Nervous System

    degenerative or inflammatory conditions affecting the central or peripheral nervous system that develop in association with a systemic neoplasm without direct invasion by tumor. they may be associated with circulating antibodies that react with the affected neural tissue. (intern med 1996 dec;35(12):925-9)
  • Theilovirus

    a species of cardiovirus which contains three strains: theiler's murine encephalomyelitis virus, vilyuisk human encephalomyelitis virus, and rat encephalomyelitis virus.
  • Visna

    demyelinating leukoencephalomyelitis of sheep caused by the visna-maedi virus. it is similar to but not the same as scrapie.
  • Central Nervous System Protozoal Infections

    infections of the brain, spinal cord, or meninges by single celled organisms of the former subkingdom known as protozoa. the central nervous system may be the primary or secondary site of protozoal infection. these diseases may occur as opportunistic infections or arise in immunocompetent hosts.
  • Lupus Vasculitis, Central Nervous System

    central nervous system vasculitis that is associated with systemic lupus erythematosus. clinical manifestations may include dementia; seizures; cranial nerve diseases; hemiparesis; blindness; dysphasia; and other neurological disorders.
  • Lyme Neuroborreliosis

    nervous system infections caused by tick-borne spirochetes of the borrelia burgdorferi group. the disease may affect elements of the central or peripheral nervous system in isolation or in combination. common clinical manifestations include a lymphocytic meningitis, cranial neuropathy (most often a facial neuropathy), polyradiculopathy, and a mild loss of memory and other cognitive functions. less often more extensive inflammation involving the central nervous system (encephalomyelitis) may occur. in the peripheral nervous system, b. burgdorferi infection is associated with mononeuritis multiplex and polyradiculoneuritis. (from j neurol sci 1998 jan 8;153(2):182-91)
  • Meningitis, Listeria

    inflammation of the meninges caused by listeria monocytogenes infection, usually occurring in individuals under the age of 3 years or over the age of 50 years. it may occur at any age in individuals with immunologic deficiency syndromes. clinical manifestations include fever, altered mentation, headache, meningeal signs, focal neurologic signs, and seizures. (from medicine 1998 sep;77(5):313-36)
  • Meningoencephalitis

    an inflammatory process involving the brain (encephalitis) and meninges (meningitis), most often produced by pathogenic organisms which invade the central nervous system, and occasionally by toxins, autoimmune disorders, and other conditions.
  • Ascaridida

    an order of nematodes of the subclass secernentea. its organisms possess two or three pairs of dorsolateral caudal papillae.
  • Alphavirus

    a genus of togaviridae, also known as group a arboviruses, serologically related to each other but not to other togaviridae. the viruses are transmitted by mosquitoes. the type species is the sindbis virus.
  • RNA

    a polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. rna is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (rieger et al., glossary of genetics: classical and molecular, 5th ed)
  • Alphavirus Infections

    virus diseases caused by members of the alphavirus genus of the family togaviridae.
  • Bornaviridae

    a family in the order mononegavirales comprising one genus bornavirus. this family has a unique form of mrna processing: replication and transcription takes place in the nucleus.
  • Hepatovirus

    a genus of picornaviridae causing infectious hepatitis naturally in humans and experimentally in other primates. it is transmitted through fecal contamination of food or water. hepatitis a virus is the type species.
  • Fibromyalgia

    a common nonarticular rheumatic syndrome characterized by myalgia and multiple points of focal muscle tenderness to palpation (trigger points). muscle pain is typically aggravated by inactivity or exposure to cold. this condition is often associated with general symptoms, such as sleep disturbances, fatigue, stiffness, headaches, and occasionally depression. there is significant overlap between fibromyalgia and the chronic fatigue syndrome (fatigue syndrome, chronic). fibromyalgia may arise as a primary or secondary disease process. it is most frequent in females aged 20 to 50 years. (from adams et al., principles of neurology, 6th ed, p1494-95)
  • Cardiovirus

    a genus of the family picornaviridae causing encephalitis and myocarditis in rodents. encephalomyocarditis virus is the type species.
  • Opportunistic Infections

    an infection caused by an organism which becomes pathogenic under certain conditions, e.g., during immunosuppression.
  • Acute Hemorrhagic Encephalitis

    acute encephalitis that is characterized by bleeding.
  • Acute Hemorrhagic Leukoencephalitis

    a degenerative brain disorder presenting with acute neurological manifestations. it usually associated with an acute infection or vaccination. it is characterized by brain hemorrhage, vascular necrosis and demyelination. signs and symptoms include fever, headache, vomiting, convulsions and loss of consciousness.
  • Aicardi-Goutieres Syndrome 1|AGS1|Cree Encephalitis|Encephalopathy, Familial Infantile, with Intracranial Calcification and Chronic Cerebrospinal Fluid Lymphocytosis|Pseudotoxoplasmosis Syndrome

    a heritable condition, caused by mutation(s) in the trex1 gene, encoding three-prime repair exonuclease 1. clinical features and onset may vary significantly, but is characterized in its most severe form by cerebral atrophy, leukodystrophy, intracranial calcifications, chronic cerebrospinal fluid (csf) lymphocytosis, and increased concentrations of csf alpha-interferon.
  • Anti-NMDA Receptor Encephalitis

    an autoimmune acute encephalitis caused by antibodies against the glutamate nmda receptor. it usually affects females and in the majority of cases it is associated with the presence of a tumor, most commonly an ovarian teratoma. the presence of a tumor in patients with this form of encephalitis implies that the latter is a paraneoplastic syndrome. it is manifested with psychiatric symptoms and epileptic seizures. it is a potentially lethal disorder; however, it is usually reversible with the prompt removal of the tumor.
  • Autoimmune Encephalitis

    inflammation of the brain secondary to an immune response triggered by the body itself.
  • Cordonnier Grade 3 Viral Complication, Viral Encephalitis|Grade 3 Any Viral Encephalitis

    any viral encephalitis.
  • COVID-19-Associated Acute Hemorrhagic Necrotizing Encephalitis|COVID-19-Associated Acute Hemorrhagic Necrotizing Encephalopathy|SARS-CoV-2-Associated Acute Hemorrhagic Necrotizing Encephalitis|SARS-CoV-2-Associated Acute Hemorrhagic Necrotizing Encephalopathy

    acute hemorrhagic necrotizing encephalitis caused by severe acute respiratory syndrome coronavirus 2 (sars-cov-2).
  • COVID-19-Associated Encephalitis|SARS-CoV-2 -Associated Encephalitis

    encephalitis caused by severe acute respiratory syndrome coronavirus 2 (sars-cov-2).
  • Encephalitis

    an inflammatory process affecting the brain parenchyma. causes include viral infections and less frequently bacterial infections, toxins, and immune-mediated processes.
  • Encephalitis Infection, CTCAE|Encephalitis Infection|Encephalitis infection

    a disorder characterized by an infectious process involving the brain tissue.
  • Encephalitis Lethargica

    a form of encephalitis, the etiology of which is uncertain, that is characterized by lethargy and headache.
  • Epidemic Encephalitis

    a term that may be used to describe encephalitis characterized by sleepiness, which is likely due to a viral cause.
  • Grade 3 Encephalitis Infection, CTCAE|Grade 3 Encephalitis infection

    iv antibiotic, antifungal, or antiviral intervention indicated; severe changes in mental status; self-limited seizure activity; focal neurologic abnormalities
  • Grade 4 Encephalitis Infection, CTCAE|Grade 4 Encephalitis infection

    life-threatening consequences; urgent intervention indicated
  • Grade 5 Encephalitis Infection, CTCAE|Grade 5 Encephalitis infection

  • Herpes Simplex Encephalitis

    a serious viral disorder characterized by infection of the brain by herpes simplex virus type 1 or 2. herpes simplex virus type 1 affects adults, whereas herpes simplex virus type 2 affects newborns. signs and symptoms include fever, headaches, vomiting, seizures and psychiatric manifestations.
  • Infectious Encephalitis|Encephalitis infection

    an acute infectious process that affects the brain tissue. it is usually caused by viruses and less often by bacteria, parasites, and fungi.
  • Infectious Meningoencephalitis

    inflammation of the meninges and brain caused by an infectious agent.
  • Japanese B Encephalitis|Japanese Encephalitis

    viral encephalitis caused by the mosquito-born japanese encephalitis virus. signs and symptoms include an initial period of fever, headaches, and malaise, followed by neck rigidity, hemiparesis, and convulsions. it may lead to coma.
  • Japanese Encephalitis Virus Antibody Measurement|JEVAB|Japanese Encephalitis Virus Antibody|Japanese Encephalitis Virus Antibody

    the determination of the amount of japanese encephalitis virus antibody present in a sample.
  • Limbic Encephalitis

    a rare disorder characterized by degenerative changes in the limbic area of the brain. causes include infections and autoimmune conditions; it may also manifest as a paraneoplastic syndrome, most often caused by small cell lung carcinoma. signs and symptoms include behavioral changes, hallucinations and dementia.
  • Lupus Encephalitis

    encephalitis that is associated with systemic lupus erythematosus.
  • Measles morbillivirus|MEASLES MORBILLIVIRUS|MEASLES VIRUS|Measles Virus|Measles Virus|Measles Virus|Rougeole Virus|Rubeola Virus|SSPEV|Subacute Sclerosing Panencephalitis Virus|measles virus

    a morbillivirus that causes the childhood disease measles and is responsible for subacute sclerosing panencephalitis.
  • Meningoencephalitis

    inflammation of the meninges and brain, generally secondary to an infectious cause. pathogens may be bacterial, viral, fungal, or protozoan.
  • Mosquito-Borne Viral Encephalitis

    viral encephalitis that is transmitted by mosquitos.
  • Rasmussen Subacute Encephalitis|CFE|Chronic Focal Encephalitis|Rasmussen Encephalitis

    a rare, progressive chronic inflammation of a single cerebral hemisphere that usually affects children. it is characterized by severe seizures, loss of motor skills and speech, hemiparesis, and dementia.
  • Subacute Sclerosing Panencephalitis|SSPE

    a rare, slowly progressive post-infectious neurological disorder affecting the central nervous system. it is characterized by seizures, ataxia, myoclonus, personality changes, spasticity, and coma. the symptoms appear several years following measles infection at an early age.
  • Tick-Borne Encephalitis Virus|FSME virus|TBEV|TICK-BORNE ENCEPHALITIS VIRUS

    a species of enveloped, spherical and icosahedral viruses in the flaviviridae family and flavivirus genus. the genome is composed of non-segmented, single-stranded, positive-sense rna. tick-borne encephalitis viruses are found in ticks of the ixodes species and humans and cause tick-borne encephalitis in humans. tick-borne encephalitis viruses are transmitted via the bite of infected ticks, primarily ixodes ricinus or ixodes persulcatus.
  • Tick-Borne Viral Encephalitis

    viral encephalitis that is transmitted by ticks.
  • Tyrosine-Protein Kinase Fer|C-FER|EC|FER Protein|FPS/FES-Related Tyrosine Kinase|Feline Encephalitis Virus-Related Kinase FER|Fujinami Poultry Sarcoma/Feline Sarcoma-Related Protein Fer|P94-FER|Phosphoprotein NCP94|Proto-Oncogene c-Fer|TYK3 Protein|Tyrosine Kinase 3|Tyrosine-Protein Kinase FER|p94-Fer

    tyrosine-protein kinase fer (822 aa, ~95 kda) is encoded by the human fer gene. this protein plays a role in tyrosine phosphorylation, receptor signaling and cytoskeleton reorganization.
  • Viral Encephalitis

    encephalitis resulting from viral infection.
  • Acute Disseminated Encephalomyelitis|ADEM|ADEM

    an inflammatory process affecting the central nervous system. it is characterized by perivascular demyelination. symptoms usually follow an acute viral infection or immunization and include fever, confusion, somnolence and involuntary movements. it may lead to coma and death.
  • Chronic Fatigue Syndrome|Myalgic Encephalomyelitis|Myalgic encephalomyelitis/chronic fatigue syndrome|chronic fatigue syndrome

    a syndrome of unknown etiology. chronic fatigue syndrome (cfs) is a clinical diagnosis characterized by an unexplained persistent or relapsing chronic fatigue that is of at least six months' duration, is not the result of ongoing exertion, is not substantially alleviated by rest, and results in substantial reduction of previous levels of occupational, educational, social, or personal activities. common concurrent symptoms of at least six months duration include impairment of memory or concentration, diffuse pain, sore throat, tender lymph nodes, headaches of a new type, pattern, or severity, and nonrestorative sleep. the etiology of cfs may be viral or immunologic. neurasthenia and fibromyalgia may represent related disorders. also known as myalgic encephalomyelitis.
  • Encephalomyelitis

    inflammation of the brain and the spinal cord.
  • Encephalomyelitis Infection, CTCAE|Encephalomyelitis Infection|Encephalomyelitis infection

    a disorder characterized by an infectious process involving the brain and spinal cord tissues.
  • Experimental Allergic Encephalomyelitis|EAE|Experimental Autoimmune Encephalomyelitis

    an autoimmune demyelinating disease of the central nervous system that is produced experimentally in animals by the injection of homogenized brain or spinal cord in freund's adjuvant. myelin basic protein appears to be the antigen that elicits the hypersensitivity immune response which is characterized by focal areas of lymphocyte and macrophage infiltration into the brain, associated with demyelination and destruction of the blood-brain barrier. experimental allergic encephalomyelitis (eae) is used as an animal model for demyelinating diseases of the human central nervous system such as multiple sclerosis.
  • Grade 3 Encephalomyelitis Infection, CTCAE|Grade 3 Encephalomyelitis infection

    iv antibiotic, antifungal, or antiviral intervention indicated; invasive intervention indicated
  • Grade 4 Encephalomyelitis Infection, CTCAE|Grade 4 Encephalomyelitis infection

    life-threatening consequences; urgent intervention indicated
  • Grade 5 Encephalomyelitis Infection, CTCAE|Grade 5 Encephalomyelitis infection

  • Infectious Encephalomyelitis|Encephalomyelitis infection

    an infectious process that affects the brain and spinal cord tissues. it is usually caused by viruses.
  • Western Equine Encephalomyelitis

    a mosquito-born viral infection caused by the western equine encephalitis virus. the signs and symptoms range from flu-like illness to permanent central nervous system damage, coma, and death.

Tabular List of Diseases and Injuries

The following annotation back-references are applicable to this diagnosis code. The Tabular List of Diseases and Injuries is a list of ICD-10-CM codes, organized "head to toe" into chapters and sections with coding notes and guidance for inclusions, exclusions, descriptions and more.

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Ventriculitis (cerebral) NOS

Index to Diseases and Injuries References

The following annotation back-references for this diagnosis code are found in the injuries and diseases index. The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10-CM code(s).

Convert G04.90 to ICD-9-CM

  • ICD-9-CM Code: 323.9 - Encephalitis NOS
    Approximate Flag - The approximate mapping means there is not an exact match between the ICD-10 and ICD-9 codes and the mapped code is not a precise representation of the original code.

Patient Education


Encephalitis is an inflammation of the brain. Usually the cause is a viral infection, but bacteria can also cause it. It can be mild or severe. Most cases are mild. You may have flu-like symptoms. With a mild case, you may just need rest, plenty of fluids, and a pain reliever.

Severe cases need immediate treatment. Symptoms of severe cases include:

  • Severe headache
  • Sudden fever
  • Drowsiness
  • Vomiting
  • Confusion
  • Seizures

In babies, additional symptoms may include constant crying, poor feeding, body stiffness, and bulging in the soft spots of the skull.

Severe cases may require a stay in the hospital. Treatments include oral and intravenous (IV) medicines to reduce inflammation and treat infection. Patients with breathing difficulties may need artificial respiration. Some people may need physical, speech, and occupational therapy once the illness is under control.

NIH: National Institute of Neurological Disorders and Stroke

[Learn More in MedlinePlus]

Spinal Cord Diseases

Your spinal cord is a bundle of nerves that runs down the middle of your back. It carries signals back and forth between your body and your brain. It is protected by your vertebrae, which are the bone disks that make up your spine. If you have an accident that damages the vertebrae or other parts of the spine, this can also injure the spinal cord. Other spinal cord problems include:

  • Tumors
  • Infections such as meningitis and polio
  • Inflammatory diseases
  • Autoimmune diseases
  • Degenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy

Symptoms vary but might include pain, numbness, loss of sensation and muscle weakness. These symptoms can occur around the spinal cord, and also in other areas such as your arms and legs. Treatments often include medicines and surgery.

[Learn More in MedlinePlus]

Code History

  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.


[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.