Mike Parenteau

Etiology / PathophysiologyEtiology / Pathophysiology

•EncephalitisEncephalitis is an is an acuteacute inflammation inflammation of the of the brainbrain, commonly caused by a , commonly caused by a viralviral infectioninfection. Sometimes, encephalitis . Sometimes, encephalitis can result from a can result from a bacterialbacterial infection, infection, such as bacterial such as bacterial meningitismeningitis, or it may , or it may be a complication of other infectious be a complication of other infectious diseases like diseases like rabiesrabies (viral) or (viral) or syphilissyphilis (bacterial) (bacterial)

Etiology / PathophysiologyEtiology / Pathophysiology

• Certain Certain parasiticparasitic protozoalprotozoal infestations, like by infestations, like by toxoplasmatoxoplasma, can , can also cause encephalitis in people also cause encephalitis in people with compromised with compromised immune systemsimmune systems. .

Etiology / PathophysiologyEtiology / Pathophysiology

• Victims are usually exposed to viruses Victims are usually exposed to viruses resulting in encephalitis by insect bites resulting in encephalitis by insect bites or food and drink. The most frequently or food and drink. The most frequently encountered agents are encountered agents are herpes simplexherpes simplex viruses, viruses, arbovirusesarboviruses (carried by (carried by arthropodsarthropods such as such as mosquitoesmosquitoes or or ticksticks, , see also see also tick-borne meningoencephalitistick-borne meningoencephalitis) and ) and enterovirusesenteroviruses ( (coxsackieviruscoxsackievirus, , polioviruspoliovirus and and echovirusechovirus). ).

Etiology / PathophysiologyEtiology / Pathophysiology

• Some of the less frequent agents are Some of the less frequent agents are measlesmeasles, , rabiesrabies, , mumpsmumps, and , and varicellavaricella

• Numerically, the most important Numerically, the most important cause of encephalitis worldwide is cause of encephalitis worldwide is probably Japanese encephalitis, as it probably Japanese encephalitis, as it causes up to 50 000 cases a year, causes up to 50 000 cases a year, with about 15 000 deaths. with about 15 000 deaths.

Etiology / PathophysiologyEtiology / Pathophysiology

• The most widespread cause of The most widespread cause of encephalitis worldwide, however, is encephalitis worldwide, however, is Herpes Simplex encephalitis. The herpes Herpes Simplex encephalitis. The herpes simplex virus causes inflammation on simplex virus causes inflammation on the temporal lobe of the brain, and if not the temporal lobe of the brain, and if not treated, half to three quarters of the treated, half to three quarters of the patients succumb. In very young patients succumb. In very young children, however, the virus could affect children, however, the virus could affect any part of the brain, even sparing the any part of the brain, even sparing the temporal lobe. temporal lobe.

Encephalitis lethargica Encephalitis lethargica

• Encephalitis lethargicaEncephalitis lethargica is an atypical form of is an atypical form of encephalitis which caused an encephalitis which caused an epidemicepidemic from from 19171917 to to 19281928. There have only been a small . There have only been a small number of isolated cases since, though in number of isolated cases since, though in recent years a few patients have shown recent years a few patients have shown very similar symptoms. The cause is now very similar symptoms. The cause is now thought to be a bacterial agent or an thought to be a bacterial agent or an autoimmune response following infection. autoimmune response following infection. As depicted in the book As depicted in the book AwakeningsAwakenings

Limbic System Encephalitis Limbic System Encephalitis

• In a small number of cases, the pathogens In a small number of cases, the pathogens responsible for encephalitis attack primarily responsible for encephalitis attack primarily the the limbic systemlimbic system (a collection of structures (a collection of structures at the base of the brain responsible for at the base of the brain responsible for basic basic autonomicautonomic functions), often causing functions), often causing memory deficits similar to those observed in memory deficits similar to those observed in Alzheimer's diseaseAlzheimer's disease or or Creutzfeldt-Jakob diseaseCreutzfeldt-Jakob disease (although limbic (although limbic encephalitis does not cause the same encephalitis does not cause the same cognitive deficits as these diseases cognitive deficits as these diseases

Clinical ManifestationsClinical Manifestations

• Patients with encephalitis suffer from Patients with encephalitis suffer from

• feverfever, headache, vomiting, confusion, , headache, vomiting, confusion, drowsiness and photophobia drowsiness and photophobia

• weakness, seizure, and less weakness, seizure, and less commonly, stiffness of the neck commonly, stiffness of the neck

• The symptoms of encephalitis are The symptoms of encephalitis are caused by the brain's defense caused by the brain's defense mechanisms activating to get rid of mechanisms activating to get rid of the infection, including swelling, the infection, including swelling, small bleedings and cell death. small bleedings and cell death.

AssessmentAssessment

• Neurologic examination usually Neurologic examination usually reveal a drowsy or confused patients reveal a drowsy or confused patients

• Stiff neck, due to the irritation of the Stiff neck, due to the irritation of the meninges covering the brain, meninges covering the brain, indicates that the patient has either indicates that the patient has either meningitis or meningoencephalitis. meningitis or meningoencephalitis.

Lumbar PunctureLumbar Puncture

• Examination of the cerebrospinal Examination of the cerebrospinal fluid obtained by a lumbar puncture fluid obtained by a lumbar puncture procedure usually reveals increased procedure usually reveals increased amounts of protein and white blood amounts of protein and white blood cells with normal glucose, though in cells with normal glucose, though in a significant percentage of patients, a significant percentage of patients, the cerebrospinal fluid may be the cerebrospinal fluid may be normal. normal.

Medical ManagementMedical Management

• Symptomatic and SupportiveSymptomatic and Supportive

• Diuretics and Corticosterids are used Diuretics and Corticosterids are used to control cerebral edemato control cerebral edema

• Acyclovir (Zovirax) and Vidarabine Acyclovir (Zovirax) and Vidarabine are used to treat encephalitis caused are used to treat encephalitis caused by herpes simplex virus.by herpes simplex virus.

Long TermLong Term

• Memory ImpairmentMemory Impairment

• EpilepsyEpilepsy

• AnosimiaAnosimia

• Personality ChangesPersonality Changes

• Behavioral AbnormalitiesBehavioral Abnormalities

• DysphasiaDysphasia