ENCEPHALITIS

Dr.Hemant(PT-NEURO)

Encephalitis

An inflammation of the brain parenchyma, presents

as diffuse and/or focal neuropsychological

dysfunction

Viral infection is the most common and important cause, with over 100 viruses implicated worldwide

Incidence of 3.5-7.4 per 100,000 persons per year

CAUSES

VIRUS -• Arboviruses – examples: Japanese encephalitis; St. Louis

encephalitis virus; West Nile encephalitis virus; Eastern, Western and Venzuelan equine encephalitis virus; tick borne encephalitis virus

• Herpes viruses – HSV-1, HSV-2, varicella zoster virus, cytomegalovirus, Epstein-Barr virus, human herpes virus 6

• Adenoviruses• Influenza A• Enteroviruses, poliovirus• Measles, mumps, and rubella viruses• Rabies• Bunyaviruses – examples: La Crosse strain of California

virus• Reoviruses – example: Colorado tick fever virus• Arenaviruses – example: lymphocytic choriomeningitis virus

Japanese Encephalitis

Most important cause of arboviral encephalitis worldwide, with over 45,000 cases reported annually

Transmitted by culex mosquito, which breeds in rice fields

› Mosquitoes become infected by feeding on domestic pigs and wild birds infected with Japanese encephalitis virus

› Infected mosquitoes transmit virus to humans and animals during the feeding process

History of Japanese Encephalitis

1800s – recognized in Japan

1924 – Japan epidemic. 6125 cases, 3797 deaths

1935 – virus isolated in brain of Japanese patient who died

of encephalitis

1938 – virus isolated from Culex mosquitoes in Japan

1948 – Japan outbreak

1949 – Korea outbreak

1966 – China outbreak

Today – extremely prevalent in South East Asia 30,000-

50,000 cases reported each year

Causes

Bacteria

H. influenza

S. pneumoniae

N. meningitidis

M. tuberculosis

Mycoplasma pneumoniae

Others

Rickettsia, Spirochete & Malaria

Clinical manifestation

Initial Signs

Fever

Headache

Malaise

Anorexia

Nausea and Vomiting

Abdominal pain

Clinical manifestation

Developing Signs

Altered LOC – mild lethargy to deep coma

AMS – confused, delirious, disoriented

Mental aberrations :

hallucinations

personality change

behavioral disorders ; occasionally frank psychosis

Focal or general seizures in >50% severe cases.

Severe focused neurologic deficits

Clinical manifestation

Neurologic Signs

Most Common

Aphasia

Ataxia

Hemiparesis with hyperactive tendon reflexes

Involuntary movements

Cranial nerve deficits (ocular palsies, facial weakness)

Diagnosis

Patient History

Physical exam

Work up

Patient History

Prodromal illness, recent vaccination, development

of few days → Acute Disseminated

Encephalomyelitis (ADEM)

Biphasic onset : systemic illness then CNS disease →

Enterovirus encephalitis

Abrupt onset, rapid progression over few days →

HSV encephalitis

Patient History

Recent travel and the geographical :

› Africa → Cerebral malaria

› Asia → Japanese encephalitis

› High risk regions of Europe and USA → Lyme disease

Recent animal bites → Tick borne encephalitis or

Rabies

Occupation

› Forest worker, exposed to tick bites

› Medical personnel, possible exposure to infectious

diseases

Patient History

Season

› Japanese encephalitis : rainy season

› Arbovirus infections are : summer and fall

Predisposing factors :

› Immunosuppression caused by disease and/or drug treatment

› Organ transplant → Opportunistic infections

› HIV → CNS infections

HSV-2 encephalitis and CMV infection

Drug ingestion and/or abuse

Trauma

Physical exam

Focal neurological deficit → HSV encephalitis

Hallucination or aphasia → HSV encephalitis

Local paresthesia → Rabies encephalitis

Brain stem signs, Unilateral peripheral motor weakness or

Cerebellar sign → Meliodosis

Eschar → Scrub typhus

Parotitis → Mumps

Systemic sign eg. Rash → Mycoplasma & Enterovirus

Work up

CBC : usually within the reference range

Electrolytes : usually within reference range

Syndrome of inappropriate secretion of antidiuretic

hormone (SIADH)

Serum glucose : Use this level as a baseline for

determining normal CSF glucose values

Work up

BUN/creatinine and liver function tests (LFTs) :

Assess organ function and the need to adjust the

antibiotic dose

Platelet test and a coagulation profile : indicated

in patients with chronic alcohol use, liver disease, or

if DIC is suspected

Urinary electrolyte test : Perform this assessment if

SIADH is suspected

Urine and/or serum toxicology screening

Work up

Lumbar puncture

CSF examination (Polymorphonuclear cells may

predominate early in the illness but are replaced by

mononuclear cells within hours)

Viral culture

Viral PCR may identify the virus

Serology tests antibodies to an specific virus → JEV,

Dengue, Mycoplasma (4 fold rising )

CSF

It reveals 5-500 lymphocytes.

The protein is mildly elevated

The glucose is normal

EEG

Certain EEG wave patterns can suggest encephalitis

due to herpes

Unilateral or Bilateral periodic focal spike with slow

activity background

Imaging

Differential diagnosis

Metabolic causes

Drug & Toxicology

Mass lesion

Epilepsy

Subarachnoid hemorrhage

Acute confusional migraine

Autoimmune : SLE

CNS Vasculitis

Differential diagnosis

Encephalopathy Encephalitis

Fever Uncommon Common

Headache Uncommon Common

AMS Steady deterioration May fluctuate

Focal Neurologic Signs Uncommon Common

Types of seizures Generalized Both

Blood: Leukocytosis Uncommon Common

CSF: Pleocytosis Uncommon Common

EEG: Diffuse slowing Common +Focal

MRI Often normal Focal Abn.

Treatment

No satisfactory treatment exists for the relatively

common acute arboviral encephalitides, which vary

in epidemiology, mortality, and morbidity, if not

clinical presentation

Treatment

Clinically distinguishing these acute arboviral

encephalitis from the 2 potentially treatable acute

viral encephalitis is important

Herpes simplex encephalitis (HSE), which is a sporadic

and lethal disease of neonates and the general

population

Less common varicella-zoster encephalitis, which is

deadly in immunocompromised patients

Treatment

Specific treatment

HSV encephalitis : Neonate & infant Acyclovir 60

mg/kg/day IV div 8 hr 14 -21 days, Child & Adult 30

mg/kg/day 14 -21 days

Varicella zoster encephalitis : Acyclovir

CMV encephalitis : Gancyclovir or Foscanir

Others : depend on etiology

Treatment

Supportive treatment

Reduce intracranial pressure : restrict fluid ,

hyperventilation( if on ventilator), low body

temperature , steroid ? (Mycoplasma )

Rest, nutrition, fluids (SIADH), antipyretic, Anticonvulsant

Acute psychosis : haloperidol

Prognosis

Depends the virulence of the virus and on variables

associated with the patient's health status, such as

extremes of age, immune status, and preexisting

neurologic conditions

Rabies, EEE, JE, and untreated HSE have high rates

of mortality and severe morbidity, including mental

retardation, hemiplegia, and seizures

Prognosis

The mortality rate in treated HSE averages 20%

and is correlated with mental status changes at time

of first dose of acyclovir

Approximately 40% of survivors have minor-to-

major learning disabilities, memory impairment,

neuropsychiatric abnormalities, epilepsy, fine-motor-

control deficits, and dysarthria

Prevention

Controlling mosquitoes : Dengue

Animal vaccination : Rabies virus

Human vaccination : JEV

Medical/Legal Pitfalls

Failure to consider HSE in the diagnosis or to initiate

administration of acyclovir in a timely fashion