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Encephalitis

Encephalitis is inflammation of the brain.[5] The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting.[1][6] Complications may include seizures, hallucinations, trouble speaking, memory problems, and problems with hearing.[1]

Encephalitis

Neurology, infectious disease

Headache, fever, confusion, stiff neck, vomiting[1]

Seizures, trouble speaking, memory problems, problems hearing[1]

Weeks to months for recovery[1]

Herpes simplex, West Nile, rabies, Eastern equine, others[2]

Infection, autoimmune, certain medication, unknown[2]

Based on symptoms, supported by blood tests, medical imaging, analysis of cerebrospinal fluid[2]

Antiviral medication, anticonvulsants, corticosteroids, artificial respiration[1]

Variable[1]

4.3 million (2015)[3]

150,000 (2015)[4]

Causes of encephalitis include viruses such as herpes simplex virus and rabies virus as well as bacteria, fungi, or parasites.[1][2] Other causes include autoimmune diseases and certain medications.[2] In many cases the cause remains unknown.[2] Risk factors include a weak immune system.[2] Diagnosis is typically based on symptoms and supported by blood tests, medical imaging, and analysis of cerebrospinal fluid.[2]


Certain types are preventable with vaccines.[5] Treatment may include antiviral medications (such as acyclovir), anticonvulsants, and corticosteroids.[1] Treatment generally takes place in hospital.[1] Some people require artificial respiration.[1] Once the immediate problem is under control, rehabilitation may be required.[2] In 2015, encephalitis was estimated to have affected 4.3 million people and resulted in 150,000 deaths worldwide.[3][4]

Signs and symptoms[edit]

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.[7] 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.[8]

Brain scan, done by , can determine inflammation and differentiate from other possible causes.

MRI

in monitoring brain activity, encephalitis will produce abnormal signal.

EEG

(spinal tap), this helps determine via a test using the cerebral-spinal fluid, obtained from the lumbar region.

Lumbar puncture

Blood test

Urine analysis

(PCR) testing of the cerebrospinal fluid, to detect the presence of viral DNA which is a sign of viral encephalitis.

Polymerase chain reaction

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.[22] Diagnosing encephalitis is done via a variety of tests:[23][24]

Prevention[edit]

Vaccination is available against tick-borne[25] and Japanese encephalitis[26] 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.[27] Contraindication to Pertussis immunization should be observed in patients with encephalitis.[28]

Prognosis[edit]

Identification of poor prognostic factors include cerebral edema, status epilepticus, and thrombocytopenia.[33] In contrast, a normal encephalogram at the early stages of diagnosis is associated with high rates of survival.[33]

Terminology[edit]

Encephalitis with meningitis is known as meningoencephalitis, while encephalitis with involvement of the spinal cord is known as encephalomyelitis.[2]


The word is from Ancient Greek ἐγκέφαλος, enképhalos 'brain',[36] composed of ἐν, en, 'in' and κεφαλή, kephalé, 'head', and the medical suffix -itis 'inflammation'.[37]

WHO: Viral Encephalitis