Encephalitis

Encephalitis is irritation and swelling (inflammation) of the brain parenchyma, most often due to infections.

Encephalitis with meningitis is known as meningoencephalitis.

Causative Agents

• Specifically to rural areas are Arboviruses or Arthropod-borne Viruses (viruses carried by arthropods, such as mosquitoes and tick), while in urban areas it is most frequently caused by Enteroviruses (Coxsackievirus, Poliovirus and Echovirus)
• Enteroviruses Incubation Period is most oftenly 3-5 days

Mode of Transmission

• Breathing in respiratory droplets from an infected person
• Skin contact
• Mosquito, tick, and other insect bites Tick of Horses
• Migratory Birds
• Contaminated food or drink

Pathogenesis

• Virus enters blood & reaches the parenchyma of brain, cortex, white matter, basal ganglia and brainstem
• Inclusion bodies are often present in neurons and  glial cells and there is infiltration of polymorphonuclear cells in perivascular space
• There is neuronal degeneration and diffuse glial proliferation often associated with cerebral edema and increased  ICP
• Thrombosis may occur in small arteries of brain
• Tonsillar herniation may also be seen due to raised ICP

Signs and symptoms

• Severe headache
• Fever , appetite loss, weakness
• Altered consciousness Confusion or agitation Personality changes
• Seizures
• Loss of sensation or paralysis in certain areas of the body
• Muscle weakness Hallucinations
• Double vision Perception of foul smel Is Problems with speech or hearing
• Loss of consciousness
• In infants, important signs include:  vomiting, a full or bulging fontanel, crying that doesn't stop or that seems worse when an infant is picked up or handled in some way, body stiffness

Diagnostic procedure

• Neurological examinations reveal a drowsy or confused patient
• Stiff neck, may indicate meningoencephalitis
• Electroencephalography (EEG) This can identify abnormal brain waves by monitoring electrical activity in the brain through the skull. Among its many functions, EEG is used to help diagnose certain seizure disorders, brain damage from head injuries, specific viral infections such as herpesvirus, and inflammation of the brain and or spinal cord.

• Blood tests These tests can show what type of virus is causing encephalitis.

• Computer-assisted imaging (Computed tomography: CT SCAN and Magnetic resonance imaging: MRI)

This can reveal signs of brain inflammation, internal bleeding or hemorrhage, or other brain abnormalities.

Treatment

• Maintain fluid and nourishment
• Antiviral medications, such as Acyclovir (Zovirax) and Foscarnet (Foscavir) — to treat herpes encephalitis or other severe viral infections (however, no specific antiviral drugs are available to fight encephalitis) 

• Antibiotics — if the infection is caused by certain bacteria
• Anti-seizure medications (such as Phenytoin) - to prevent seizures
• Steroids (such as Dexamethasone) - to reduce brain swelling (in rare cases)
• Sedatives - to treat irritability or restlessness
• Acetaminophen - for fever and headache

Prevention

• Encephalitis cannot be prevented except to try to prevent causes that may lead to it.
• Encephalitis that may be seen with common childhood illness can be largely prevented through proper immunization.
• Children should avoid contact with anyone who already has encephalitis.