Encephalitis
Template:Short description Template:Pp-protected Template:Cs1 config Template:Infobox medical condition (new)
Encephalitis is inflammation of the brain.<ref name="NHS2016">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The severity can be variable with symptoms including reduction or alteration in consciousness, aphasia, headache, fever, confusion, a stiff neck, and vomiting.<ref name=NIH207Main/><ref>Template:Cite journal</ref> Complications may include seizures, hallucinations, trouble speaking, memory problems, and problems with hearing.<ref name="NIH207Main">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Causes of encephalitis include viruses such as herpes simplex virus and rabies virus as well as bacteria, fungi, or parasites.<ref name=NIH207Main/><ref name=NIH2017Fact/> Other causes include autoimmune diseases and certain medications.<ref name="NIH2017Fact">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In many cases the cause remains unknown.<ref name=NIH2017Fact/> Risk factors include a weak immune system.<ref name=NIH2017Fact/> Diagnosis is typically based on symptoms and supported by blood tests, medical imaging, and analysis of cerebrospinal fluid.<ref name=NIH2017Fact/>
Certain types are preventable with vaccines.<ref name=NHS2016/> Treatment may include antiviral medications (such as acyclovir), anticonvulsants, and corticosteroids.<ref name=NIH207Main/> Treatment generally takes place in hospital.<ref name=NIH207Main/> Some people require artificial respiration.<ref name=NIH207Main/> Once the immediate problem is under control, rehabilitation may be required.<ref name=NIH2017Fact/> In 2015, encephalitis was estimated to have affected 4.3 million people and resulted in 150,000 deaths worldwide.<ref name="GBD2015Pre">Template:Cite journal</ref><ref name="GBD2015De">Template:Cite journal</ref>
Signs and symptomsEdit
Adults with encephalitis present with acute onset of fever, headache, confusion, and sometimes seizures. Younger children or infants may present with irritability, poor appetite and fever.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Neurological examinations usually reveal a drowsy or confused person. Stiff neck, due to the irritation of the meninges covering the brain, indicates that the patient has either meningitis or meningoencephalitis.<ref>Template:Cite book</ref>
Limbic encephalitisEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}}
Limbic encephalitis refers to inflammatory disease confined to the limbic system of the brain. The clinical presentation often includes disorientation, disinhibition, memory loss, seizures, and behavioral anomalies. MRI imaging reveals T2 hyperintensity in the structures of the medial temporal lobes, and in some cases, other limbic structures. Some cases of limbic encephalitis are of autoimmune origin.<ref>Template:Cite book</ref>
Encephalitis lethargicaEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}}
Encephalitis lethargica is identified by high fever, headache, delayed physical response, and lethargy. Individuals can exhibit upper body weakness, muscular pains, and tremors, though the cause of encephalitis lethargica is not currently known. From 1917 to 1928, an epidemic of encephalitis lethargica occurred worldwide.<ref>Template:NINDS</ref>
CauseEdit
In 30%-40% of encephalitis cases, the etiology remains unknown.<ref name=":1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ViralEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Viral infections are the usual cause of infectious encephalitis.<ref name=":1" /> Viral encephalitis can occur either as a direct effect of an acute infection, or as one of the sequelae of a latent infection. The majority of viral cases of encephalitis have an unknown cause; however, the most common identifiable cause of viral encephalitis is from herpes simplex infection.<ref>Template:Cite book</ref> Other causes of acute viral encephalitis are rabies virus, poliovirus, and measles virus.<ref>Template:Cite journal</ref>
Additional possible viral causes are arboviral flavivirus (St. Louis encephalitis, West Nile virus), bunyavirus (La Crosse strain), arenavirus (lymphocytic choriomeningitis virus), reovirus (Colorado tick virus), and henipavirus infections.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref> The Powassan virus is a rare cause of encephalitis.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
BacterialEdit
It can be caused by a bacterial infection, such as bacterial meningitis,<ref>Template:Cite book</ref> or may be a complication of a current infectious disease such as syphilis (secondary encephalitis).<ref>Template:Cite journal</ref>
Other bacterial pathogens, like Mycoplasma and those causing rickettsial disease, cause inflammation of the meninges and consequently encephalitis. Lyme disease or Bartonella henselae may also cause encephalitis.Template:Citation needed
Other infectious causesEdit
Certain parasitic or protozoal infestations, such as toxoplasmosis and malaria can also cause encephalitis in people with compromised immune systems.
The rare but typically deadly forms of encephalitis, primary amoebic meningoencephalitis and Granulomatous amoebic encephalitis, are caused by free-living amoeba.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Autoimmune encephalitisEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}}
Autoimmune encephalitis signs can include catatonia, psychosis, abnormal movements, and autonomic dysregulation. Antibody-mediated anti-N-methyl-D-aspartate-receptor encephalitis and Rasmussen encephalitis are examples of autoimmune encephalitis.<ref>Template:Cite journal</ref>
Anti-NMDA receptor encephalitis is the most common autoimmune form, and is accompanied by ovarian teratoma in 58 percent of affected women 18–45 years of age.<ref>Template:Cite journal</ref>
Another autoimmune cause includes acute disseminated encephalitis, a demyelinating disease which primarily affects children.<ref>Template:EMedicine</ref>
DiagnosisEdit
People should only be diagnosed with encephalitis if they have a decreased or altered level of consciousness, lethargy, or personality change for at least twenty-four hours without any other explainable cause.<ref>Template:Cite journal</ref> Diagnosing encephalitis is done via a variety of tests:<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref>
- Brain scan, done by MRI, can determine inflammation and differentiate from other possible causes.
- EEG, in monitoring brain activity, encephalitis will produce abnormal signal.
- Lumbar puncture (spinal tap), this helps determine via a test using the cerebral-spinal fluid, obtained from the lumbar region.
- Blood test
- Urine analysis
- Polymerase chain reaction (PCR) testing of the cerebrospinal fluid, to detect the presence of viral DNA which is a sign of viral encephalitis.
PreventionEdit
Vaccination is available against tick-borne<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and Japanese encephalitis<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and should be considered for at-risk individuals. Post-infectious encephalomyelitis complicating smallpox vaccination is avoidable, for all intents and purposes, as smallpox is nearly eradicated.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Contraindication to Pertussis immunization should be observed in patients with encephalitis.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
TreatmentEdit
An ideal drug to treat brain infection should be small, moderately lipophilic at pH of 7.4, low level of plasma protein binding, volume of distribution of litre per kg, does not have strong affinity towards binding with P-glycoprotein, or other efflux pumps on the surface of blood–brain barrier. Some drugs such as isoniazid, pyrazinamide, linezolid, metronidazole, fluconazole, and some fluoroquinolones have good penetration to blood brain barrier.<ref name="pmid20930076">Template:Cite journal</ref> Treatment (which is based on supportive care) is as follows:<ref>Template:MedlinePlus</ref> Template:Columns-list
Pyrimethamine-based maintenance therapy is often used to treat toxoplasmic encephalitis (TE), which is caused by Toxoplasma gondii and can be life-threatening for people with weak immune systems.<ref name="Connollyetal2017">Template:Cite journal</ref> The use of highly active antiretroviral therapy (HAART), in conjunction with the established pyrimethamine-based maintenance therapy, decreases the chance of relapse in patients with HIV and TE from approximately 18% to 11%.<ref name="Connollyetal2017" /> This is a significant difference as relapse may impact the severity and prognosis of disease and result in an increase in healthcare expenditure.<ref name="Connollyetal2017" />
The effectiveness of intravenous immunoglobulin for the management of childhood encephalitis is unclear. Systematic reviews have been unable to draw firm conclusions because of a lack of randomised double-blind studies with sufficient numbers of patients and sufficient follow-up.<ref name=":0">Template:Cite journal</ref> There is the possibility of a benefit of intravenous immunoglobulin for some forms of childhood encephalitis on some indicators such as length of hospital stay, time to stop spasms, time to regain consciousness, and time to resolution of neuropathic symptoms and fever.<ref name=":0" /> Intravenous immunoglobulin for Japanese encephalitis appeared to have no benefit when compared with placebo (pretend) treatment.<ref name=":0" />
PrognosisEdit
Identification of poor prognostic factors include cerebral edema, status epilepticus, and thrombocytopenia.<ref name="Venkatesan2015">Template:Cite journal</ref> In contrast, a normal encephalogram at the early stages of diagnosis is associated with high rates of survival.<ref name="Venkatesan2015" />
EpidemiologyEdit
The number of new cases a year of acute encephalitis in Western countries is 7.4 cases per 100,000 people per year. In tropical countries, the incidence is 6.34 per 100,000 people per year.<ref name="Jmor">Template:Cite journal</ref> The number of cases of encephalitis has not changed much over time, with about 250,000 cases a year from 2005 to 2015 in the US. Approximately seven per 100,000 people were hospitalized for encephalitis in the US during this time.<ref name="Venkatesan2015" /> In 2015, encephalitis was estimated to have affected 4.3 million people and resulted in 150,000 deaths worldwide.<ref name=GBD2015De/><ref name=GBD2015Pre/> Herpes simplex encephalitis has an incidence of 2–4 per million of the population per year.<ref name="Rozenberg">Template:Cite journal</ref>
TerminologyEdit
Encephalitis with meningitis is known as meningoencephalitis, while encephalitis with involvement of the spinal cord is known as encephalomyelitis.<ref name=NIH2017Fact/>
The word is from Ancient Greek {{#invoke:Lang|lang}}, {{#invoke:Lang|lang}} 'brain',<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> composed of {{#invoke:Lang|lang}}, {{#invoke:Lang|lang}}, 'in' and {{#invoke:Lang|lang}}, {{#invoke:Lang|lang}}, 'head', and the medical suffix -itis 'inflammation'.<ref>The word seems to have had a meaning of "lithic imitation of the human brain" at first, according to the Trésor de la langue française informatisé (cf. the article on "encéphalite" Template:Webarchive). The first use in the medical sense is attested from the early 19th century in French (J. Capuron, Nouveau dictionnaire de médecine, chirurgie..., 1806), and from 1843 in English respectively (cf. the article "encephalitis" in the Online Etymology Dictionary). Retrieved 11 March 2017.</ref>
See alsoEdit
ReferencesEdit
Further readingEdit
- Template:Cite journal
- Template:Cite journal
- {{#invoke:citation/CS1|citation
|CitationClass=web }} Template:Refend
External linksEdit
Template:Medical condition classification and resources Template:Sister project