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Encephalitis Is An Infection Of The Brain Biology Essay

Paper Type: Free Essay Subject: Biology
Wordcount: 4771 words Published: 1st Jan 2015

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Encephalitis is an infection of the brain that cause of irritation and inflammation to the brain Medical Encylopedia, 2012. Primary encephalitis is happened when the infection of the brain or spinal cord. Secondary encephalitis is happened when the infection is started to spread to the whole body and to the brain (Nordqvist, 2009).

Encephalitis is a swelling of the brain parenchyma (nervous tissue in brain) that responsible for function of electrochemical communication and the ability of body to send message to different parts (david)


Goodman (2003) argued that encephalitis is an acute inflammatory disease of the parenchyma of the brain. It is caused by direct viral invasion or hypersensitivity initiated by a virus. Encephalitis is characterized by inflammation primarily in the gray matter of the central nervous system (CNS). Neuronal death can result in edema. There can be damage to the vascular system and inflammation of the arachnoid and pia matter.

1.1.1 Encephalitis


Debbie Bridges (2012) argue that encephalitis is a swelling of the brain tissue, it will become serious when it can cause change personality, debility and another symptoms with the different part of brain affected. It usually happened to children and elder with low immune system. It is very rare, in U.S, about one in 200,000 people in year.

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Nordqvist (2009) agreed that encephalitis is acute inflammation of the brain because immune system of the body is too low to attacks viral infection. Fever and headache usually the first symptoms and it become more dangerous like unconsciousness, confusion and coma. The patient will be faced a problem such as behaviour changes, loss of memory, language and speech problem (aphasia) and epilepsy.

Arthropod — borne (mosquito — borne) viruses and herpes simplex (herpes simplex type 1) are the most common that causes encephalitis. Encephalitis is an acute febrile disease usually of viral origin and involves with nervous system ().

1.1.2 Viral Meningoencephalitis

According to kumar 2004, viral encephalitis is infection of the brain at parenchymal almost constantly associated with meningoencephalitis (meningeal inflammation) and sometimes with encephalomyelitis (involves spinal cord).

1.2 Anatomy of brain


Figure Anatomy of the brain


Figure Layer of meninges

The brain is protected by the scalp, the skull and the meninges, cerebrospinal fluid and blood-brain barrier. The structures of brain consists cerebellum, cerebrum, brainstem and pituitary gland. Layer of meninges include the dura mater (strongest layer), arachnoid mater) and pia mater (nearest to the brain). (Stephen n all 2010).

Antranik (2011) states that meninges are surround the brain and protect the brain itself. The function meninges is cover and protect the blood vessel that supply at brain and contains cerebrospinal fluid (CSF) between the pia mater and arachnoid mater. Dura mater consists periosteal and meningeal at immediately deep to the poriosteum.

Tortora (2009) notes that the function of the blood- brain barrier (BBB) is to protect the brain from harmful substances and pathogens by prevent it enter brain through blood. The function of CSF is protecting the brain and spinal cord from chemical and physical injury.

The cerebrum is the largest part of the brain. Each area of cerebrum is the most important function for example controls movement and languages. The function of cerebellum is control coordination and movement. Function of brainstem is control involuntary functions such as blood pressure, temperature and breathing movement. The structure that controls of the endocrine gland is pituitary gland (Stephen 2010)

1.3 Type of Encephalitis

Western equine encephalitis is arboviral infection that spread by mosquitoes which more occur in summer and most common in young children.

St. Louis encephalitis is more usually at United States and affected older person. It is more seriously than younger person.

West Nile fever is a form of encephalitis that caused by falvivirus, spread by mosquitoes with certain birds as an intermediate host. Encephalitis has spread from northeastern United States.

Neuroborreliosis (lyme disease) is due by a spirochete, transmitted by tick bites in summer season. The part of the tick bite is red with a pale center and gradually increasing size.

Herpes simplex encephalitis is arising from spread of herpes simplex virus type 1 from the trigeminal nerve ganglion. It is occurs occasionally and dangerous. This encephalitis can cause extensive necrosis and haemorrhage in the brain and usually involves the frontal and temporal lobes figures …..


Figure heamorrhagic necrosis of the temporal and frontal lobe in adult Herpes Simplex Virus encephalitis.



2.1 Causes


Figure 2 a – herpes simplex virus the most common cause encephalitis.

Viral infection is the cause that affects the encephalitis. Encephalitis may be cause with different type of viruses. Herpes simplex virus is the main cause of severe cases in all ages including newborns. The person will get this virus from an infected person through breathing in respiratory droplets and skin contact. It can also through by insect bites like a mosquito and contaminated food or drink. Arbovirus encephalitis is a viral encephalitis that carried by insect (mosquito and ticks). It is rare condition where severe case more likely is happened to young children and elderly.

Picture of Culex mosquito laying eggs

Figure Culex mosquito laying eggs

Picture of arbovirus transmission cycle

It also may cause by a vaccine such as rubella, mumps and measles (Kathryn & Sue 1994). Adenovirus, coxsackievirus. Eastern Equine Encephalitis Virus and Echovirus are also associated with encephalitis. A number of viruses for which there is now a vaccine may also cause encephalitis. These include meales, mumps, polio, rabies, rubella, varicella (chickenpox). Other causes of encephalitis may be occurring by an allergic reaction to vaccinations, autoimmune disease, bacteria (lyme disease and tuberculosis) and the effects of cancer.

According to (Christian Nordiqst ) the causes of encephalitis can be category by two which are primary (infectious) encephalitis and secondary (post infectious) encephalitis. For primary encephalitis, there are three main categories of viruses which are common viruses (herpes simplex virus) , childhood viruses (measles ,mumps), and arboviruses. Secondary encephalitis can be caused by a complication of viral infection.

2.2 Incidence

2.2.1 Incidence Encephalitis in Malaysia

In September 1998, an epidemic of severe fever encephalitis among pig farmers was first reported in the state of Perak Malaysia that was associated with high rate mortality. At first death were thought by Japanese encephalitis (JE) that is endemic in Malaysia and occur occasionally. However, characteristic of JE is different to these cases. A few cases patients were young children and most of the cases happened to men that have worked with pigs. Whereas, JE is mosquito borne that most common among young children and has no associated with particular occupation. JE was eliminated from possibility JE was the cause due to illness and deaths among infected pigs.

By February 1999, similar disease were happened in pigs and humans in other area in Malaysia.

2.2.2 Incidence Encephalitis in Overseas

Different viruses will occur in different locations. Many cases will tend to cluster in a certain season. According to Kathryn & Sue (1994) the arthropod —borne occurs in epidemics with different incidence like as geographic and seasonal incidence (table). Eastern equine encephalitis is the least common of encephalitis but is the most serious encephalitis.

table Viral encephalitis


Geographic incidence

Seasonal incidence

Arthropod- borne :

Eastern equine encephalitis

Eastern United States


Western equine encephalitis

Uniform distribution, throughout the United States

Summer and early fall

St. Louis encephalitis

Widespread distribution , in the far west occur in rural area, elsewhere in urban areas

Late summer

Venezuelan equine encephalitis

Sourthwestern united States

Year round

California virus encephalitis

Midwestern states

Early fall

Herpes simplex encephalitis

No particular geographic distribution

No seasonal incidence

Poliovirus poliomyelitis

Sporadic distribution where nonimmunized persons cluster

Summer and ealy fall


Sporadic distribution throughout the United States

Bites more common in the late spring and throughout the early fall




Herpes encephalitis

United states / the world

Human to human contact

West Nile encephalitis

Africa, West Asia, Middle East, United States

Mosquito / mostly birds

Eastern equine encephalitis

East Coast (from Massachussetts to Florida), Gulf Coast

Mosquito / birds

Western equine encephalitis

Western United States and Canada

Mosquito / birds

Venezuelan equine encephalitis

Western Hemisphere

Mosquito / rodents

La Crosse encephalitis

United States (Midwestern & Southeastern)

Mosquito / chipmunks, squirrels

St. Louis encephalitis

Milwestern & mid- Atlantic United States

Mosquito/ birds

Japanese encephalitis

Temperate Asia, southern and southeastern Asia

Mosquito/ birds and pigs

Picture of worldwide distribution of major arboviral encephalitides

Figure worldwide distribution and arbovirus transmission cycle.

2.3 Mortality/morbidity

Encephalitis may be a mild infectious disease to a severe disorder that is life-threatening. The dramatic clinical manifestations of encephalitis are fever delirium or confusion progressing to unconsciousness, seizure activity cranial nerve palsies, paresis and paralysis, involuntary movement and abnormal reflexes. Signs of marked intracranial pressure may be present,

2.3.1 Mortality

Charles Patrick 2012 argued that the certain of patients with encephalitis the death rate can be high. The death rates of St. Louis encephalitis can up to 30% of the cases. For Japanese encephalitis, the range death rate is from 0.3% to 60% of the people infected usually within the first week of illness and herpes encephalitis, 50%-755 of people die within 18 months. In contrast, it can increase survival up 90% when treatment by acyclovir (Zovirax).

2.3.2 Morbidity

According to james & nina 2004. Survival rates are due to the etiology of the disease. In some cases it can be fatal.

In USA, according to Centers for Disease Controls and Prevention), encephalitis most occur in children, elderly people and individuals have weakened immune systems approximately in 0.5 in every 100,000 individuals. Besides that, in UK the National Health Service (NHS) places a figure at 1.5 cases per 100,000 people. ( Christian Nordqist 2009)

2.4 Signs and Symptoms

2.4.1 Symptoms of Encephalitis

Before encephalitis begins, some patients will feel cold or stomach infection. For the case of encephalitis is not very severe, the symptoms may be similar with other disease such as fever (not very high), mild headache, low energy and poor appetite. For other symptom is confusion, drowsiness, light sensitivity, vomiting, irritability or poor temper control. (encephalitis , 2012)

According to Christian norqist 2009, symptom for less common severe in encephalitis is the patients will experience stiff neck and back (occasionally). There also can be stiffness of the limbs, slow movement and clumsiness. The patient will also have cough and feels drowsy. For the more severe cases, the patients experience severe headaches, nausea, vomiting, confusion, memory loss, hearing problems, hallucination, seizures and possibly coma. The patient will be become aggressive for some cases. (christain norqist 2009).

Symptoms of encephalitis in infants and newborns may be difficult to recognize. The parent or guardian should be alert of baby crying more than often (there will become worse when the baby is picked up and comforted). Besides that, the parent should be look out of vomiting, soft spot on the top of the head (frontal) may bulge out more. Other symptoms are includes body stiffness and poor feeding. (christain norqist 2009).

For emergency symptoms in encephalitis is the patients will loss of consciousness, poor responsiveness, coma, muscle weakness, seizures, severe headache, and sudden change in mental functions which are amnesia, lack of mood, impaired of judgement inability to make decision and less interest in daily activities. (encephalitis 2012)

2.4.2 Signs of Encephalitis

Signs of encephalitis may be show muscle weakness, speech problem, skin rash, mouth ulcers, mental confusion and neck stiffness. Other than that, signs of encephalitis are abnormal reflexes and increased intracranial pressure.

Table Summary of symptoms

Symptoms of encephalitis

Less severe

More severe

In newborn and young infants

Mild headache


Poor appetite

Light sensitivity



Stiff neck and back

Severe headache




Memory loss

Speech problem




body stiffness

poor feeding

Bulging soft spots on the top head

table Summary signs of encephalitis

Signs of encephalitis

Muscle weakness

Mouth ulcers

Neck stiffness

Skin rash

Speech problem

Abnormal reflexes

Increased intracranial pressure

Mental confusion

2.5 Pathophysiology

The virus causes inflammation of brain tissue. The brain tissue swells (cerebral edema), which may destroy nerve cells, cause bleeding in the brain (intracerebral haemorrhage), and brain damage.

When the virus spread by haematogenous (via bloodstream) like example rabies virus, it replicates outside the CNS and enter in the CNS. Since the virus through the blood- brain barrier t virus enter neural cells. These will result disruption of cell functioning, perivascular congestion, haemorrhage and a diffuse inflammatory response that disproportionately affects gray matters over white matter. Certain virus depend to neuron cell membrane preceptors that only found in specific parts of the brain like example Herpes Simplex Virus (HSV) more likely causes haemorrhage necrotic encephalitis with predilection for the limbic system, inferior and medial temporal lobes. (David)

According to james & nina 2004, individuals who obtain encephalitis more frequently develop permanent neurologic disabilities. This condition is more serious than meningitis. This is happened when the viral infection produce in cerebral edema with numerous hemorrhagic spots scattered throughout the cerebral hemispheres, brainstem and cerebellum.

2.6 Histopathology

2.6.1 Arthropod- Borne Viral Encephalitis



3.1 Computer Tomography (CT scan)

Computer Tomography is the combination of computer technology and x-rays as a result two dimensional images of organ, bones and tissues. To detect sign of encephalitis or inflammation of the meninges, usually procedure with contrast is required. The contrast is injected into bloodstream to more differentiate tissues in the brain. (national institude of neurological disorder and stroke 2011)

Mahesh (2011) states that in adult, encephalitis in CT scans visualize hypodensity in the temporal lobe either bilaterally or unilaterally. It also involves with or without frontal lobe.

3.2 Magnetic Resonance imaging (MRI)

MRI is use strong magnet and computer- generates radio waves to produce more detail images of body structures which are tissues, bones, organs and nerves. MRI is better than CT scan which is give more clearly picture that can help to recognize brain and spinal cord inflammation. Infection, tumors, eye disease and blood vessel irregularities that can be stroke. The images that require more detail, a contrast may be injected. (national institude of neurological disorder and stroke 2011)

3.3 Electroencephalography (EEG)

EEG is use by monitoring electrical activity in the brain through the skull to detect abnormal brain waves. The function of EEG is to help diagnose certain seizure disorder, specific viral infection, for example herpes virus and inflammation of the brain or spinal cord. (national institude of neurological disorder and stroke 2011)

3.4 Ultrasonography

Mahesh (2011) states that the role of ultrasonography in detects herpes encephalitis are limited. This is because it limited to identify the periventicular destructive process in neonatal evaluation ultrasonogaphy.

Ultrasound showing a good near field but less far field resolution (Cranial Ultrsonography in Neonates 2010) .

According to (james & nina , 2004) MRI is precious diagnosis because it can detect brain inflammation earlier than Computed tomography (CT), ultrasound, nuclear medicine studies, or EEG evaluation. Other anomalies such as a brain abscess or subdural emphysema or hematoma that mimics the clinical sign of viral encephalitis can be rule out by MR.

3.5 Nuclear Imaging



4.1 Computed Tomography (CT Scan)


Figure shows 30 years old men that have AIDS, presenting with left facial palsy. Figure (a) shows CT scan non contrast as a result a isodence lesion in the right basal ganglia, surrounded by hypodense edema and mass effect. Figure (b) shows CT with contrast that represent a ring- enchancing lesion in the right basal ganglia that surrounded by edema. ( Antonio, 2011)


b http://www.pediatriconcall.com/fordoctor/diseasesandcondition/pediatric_emergencies/IMAGE/v7c09a%5B1%5D.jpg

Figure (a) show some hypodensity in the thalami and temporal lobes without contrast, indicative of bilateral cortical and subcortical edema. Figure (b) shows there is meningeal enhancement at the margins of abnormal parenchymas as well as mild central enhancement after IV contrast is injected. There is no evidence of herniation.


bImage of encephalitis

Figure 4.1 (a) is a CT scan of a normal brain. Figure 4.1 (b) shows contrast materials have accumulate in infected areas and around the brain from encephalitis. (Paul 2011)

4.2 MRI Imaging


Figure 4.2 high signals in the temporal lobes including hippocampal formations and parahippogampal grae, insulae and right inferior gyrus by using coronal T2- weighted MR.


Figure shows that MRI demonstrates extensive oedema in the right temporal lobes with areas of intrinsic high T1 signal, in keeping with haemorrhage.

Axial proton density—weighted image in a 62-year-o

Figure shows 62 years old woman with confusion and herpes encephalitis with axial proton density- weight image. It demonstrates T2 hyperintensity involving the right temporal lobe.

4.3 Ultrosonography

Full-size image (20 K)

Figure demonstrate coronol ultrasound scan at the level of the frontal horns of the lateral ventricles. It performed with phased array transducer. It is shows mildly dilated frontal horns and bilateral grade 1 intraventricular hemorrhage (arrows).



5.1 Difference Encephalitis and Meningitis

Encephalitis is the dangerous than meningitis because the person that has encephalitis is more develop to permanent neurologic disabilities.

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According to james & nina 2004, meningitis is an inflammation of the meningeal that covering the brain and spinal cord. Bacteria, viruses or other organisms that reach the meninges are the causes of meningitis. This can be happened in elsewhere in the body by blood or lymph as a result from trauma and penetrating wounds, or from adjacent structures that become infected. Most common that cause meningitis is bacterial infection.

Kathryn & sue 1994 states that meningitis is infection of meninges that causes by bacteria, viruses, fungi, parasites and other toxins. This infection can be classified to acute, subacute and chronic. The pathophysiology, treatment and clinical manifestation are different for each type of organism. Bacterial meningitis is a primary of an infection of the pia mater and arachnoid, the subarachnoid space, the ventricular system and the CFS (kathyn & sue 1994).

The types of bacteria that carry for acute bacterial meningitis are meningococci, streptococci, and pneumocci. Middle ear or frontal sinus is responsible that carried the bacteria to meninges. The most common meningitis in children is meningococcal, the most common meningitis in adult is pneumococcal and streptococcal meningitis is the most common in young children.



6.1 Treatment

The objective of treatment is to help the human body to fight the infection and relieve symptoms with give supportive care like example rest, nutrition, and fluids. Antibiotics will give to patients if the infection is caused by bacteria (certain bacteria) and antiviral medication (acyclovir and foscarnet) to treat herpes encephalitis or the severe viral infection. Anti seizure medication ( phenytoin) will be given to prevent seizures. (encephalitis 2012)

Mayo 2011 states that treatment for mild cases include bed rest, drinking plenty of fluid and anti- inflammatory drugs such as acetaminophen to relieve fever and headache. For more severe cases of encephalitis can be category into three treatment which are Antiviral drugs, supportive care and follow up therapy.

6.1.1 Antiviral drugs

Acylovir and Ganciclovir are antiviral drugs that common used to treat encephalitis but it is not responding for some viruses such as insect-borne viruses. This drug also can be very effective to treat herpes simplex virus. Nausea, vomiting, diarrhea, pain of muscle or joint and loss of appetite are the side effect for the antiviral drugs. Abnormalities in kidney or liver function are rare serious problem (Mayo 2011)

6.1.2 Supportive Care

For severe encephalitis, additional supportive care also be needed in the hospital. This is including breathing assistance as monitor heart function and breathing, intravenous fluids is to ensure that appropriate levels of essential minerals and proper hydration. Anti- inflammatory also be given to help reduce pressure and swelling within the skull such as corticosteroids. Patient that have seizures or to prevent seizure, anticonvulsant medicine such as phenytoin is given (Mayo 2011).

6.1.3 Follow up therapy

Follow up therapy is depending to the type or severity of complication. This therapy includes physical therapy which is to help improve flexibility, strength, motor coordination and balance. Occupational therapy is to use adaptive products that help with everyday activities and develop everyday skills. Patient that have speech problem, speech therapy can be help to relearn muscle control and coordination. Psychotherapy is learning how to be coping strategies and have new behavioural skills that can improve personality changes and mood disorder (Mayo 2011).

6.2 Diagnosis

According to National Institute of Neurological disorders and stroke (2011), the doctor may diagnostic tests to confirm the presence of inflammation and infection by following a physical exam and medical history to looking activities of the past several days such as patient have bite by animal or insects or any contact with ill persons. The patients may perform a neurological examination, laboratory screening of blood, urine and body sections and analysis of the cerebrospinal fluid.

A neurological examination is to assess nerve function, coordination and balance, mental status, changes in behaviour and function of motor and sensory. Usually, the doctor use small light, reflex hammer to test of strength and sensation or nervous system.

Laboratory screening of blood, urine and body secretions is use to determine the presence of antibodies and foreign body that can detect and recognize brain and spinal cord inflammation and infection. Analysis of cerebrospinal fluid is the procedure that known as lumbar puncture. The procedure of lumbar puncture is special needle is inserted into the lower back and then a small of amount of cerebrospinal fluids is removed.



7.1 Expectations

Usually, outcome of encephalitis is depend on what infection involves, the severity of illness, how quickly time treatment is given. Patient with very mild encephalitis most of them can make a full recovery, although the process treatment may be slow. The patient can be recovering in 2-4 weeks for patient have experience only fever, body stiffness and headache. For the severe cases, the patient may be have problem with hearing, speech, blindness, behaviour changes, seizures, memory loss, muscle weakness, and cognitive disabilities. Long-term therapy, medication and supportive care may be required for these patients. (national institude of neurological disorder and stroke 2011)

Goodman (2003) notes that patient who may have been ill at the onset , their rate recovery range from 10% to 50%. The patients have mumps meningoencephalitis and Venezuelan equine encephalitis have an excellent expectation. Other encephalitis that have moderate to good rate of survival are western equine, St. Louis and California encephalitis. Herpes simplex encephalitis has a moderately good outcome, 50% of person neurologic disorder and 20% mortality. With similar infections, young children more take longer recover than adults. In infants, permanent cerebral sequelae are occurred.

7.2 Prevention

Christian Nordqist (2009) found that the effectives way to reduced risk to get encephalitis by keeping up to date with vaccines. Other than that, take measures to reduce the risk being bitten in area to have mosquito that carry virus encephalitis. For example, keep house mosquito free, wearing appropriate clothing, do not go mosquito infested area, using insect repellent, avoid go outside at specific time where there a lot of mosquito, for example at night and make sure there are no stagnant water in house.

Beside that, encephalitis can be prevented by avoid sharing food, glasses or other object that have be exposed from infected person. Good personal hygiene also can reduce risk to get disease from infected person. Wash hand frequently with soap and rinse under running water ( National Institude of Neurologic Disorder and Stroke 2011).




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