viral encephalitis



OVERVIEW

Definition.

Viral encephalitis is an inflammatory lesion of the brain parenchyma caused by a virus.

It often presents with fever, cognitive impairment, mental behavioral abnormalities, impaired consciousness, and convulsions.

It is a common infectious disease of the central nervous system.

Incidence

Viral encephalitis is globally dispersed and can occur at any age, with no significant gender differences.

The global annual incidence is 3.5-7.4 per 100,000 people, with high mortality and disability rates.

Herpes simplex virus encephalitis is the most common type of viral encephalitis, with a global incidence of 1.5-7 per 100,000 persons per year.

Enteroviral encephalitis is distinctly seasonal, with most cases occurring in the summer and fall. There is no significant temporal difference in the onset of the other types.

Causes

Causes

Viral infections

Many viruses can cause encephalitis and meningitis. The common types of viruses are listed below:

Herpes viruses: herpes simplex virus, EBV, etc.

Enteroviruses: mainly include novel enterovirus, coxsackievirus, poliovirus, echovirus.

Arboviruses: encephalitis B virus, dengue virus, West Nile virus, etc.

Paramyxoviruses: measles virus, mumps virus, etc.

Transmission process

Viral encephalitis is contagious and the process of transmission varies from virus to virus. The basic conditions leading to epidemics include the following three aspects.

Sources of infection: patients, healthy carriers of the virus, domestic animals.

Transmission: mainly through the digestive tract, close contact, respiratory droplets and mosquito bites.

Susceptible population: The population is generally susceptible, and children, the elderly, malnourished and immunocompromised people are more prone to the disease.

Pathogenesis

After entering the human body through the respiratory tract and gastrointestinal tract, the virus first proliferates in the lymphatic system and several organs, then enters the bloodstream, forming viremia, and finally the virus passes the blood-brain barrier and invades the brain tissue.

The virus directly causes inflammation, degeneration and necrosis of brain tissue.

The immune response caused by the virus can lead to nerve fiber and vascular lesions and aggravate brain tissue damage.

Symptoms

Clinical manifestations are characterized by systemic and neurological symptoms, and different types of encephalitis caused by different viruses may have different accompanying symptoms. Serious complications may occur in severe cases.

Main symptoms

Systemic symptoms

Fever.

Headache.

Muscle pain.

Nausea.

Vomiting.

Weakness.

Neurological symptoms

There may be no obvious neurologic symptoms in mild cases, but in severe cases, whole brain symptoms and brainstem symptoms may be present.

Neck stiffness.

Headache, especially when head is bowed.

Projectile vomiting.

Infants and young children show agitation, screaming and crying.

Blurred vision.

Difficulty in verbal communication.

Twitching of limbs.

Unconsciousness, coma.

Limb weakness, paralysis, muscle atrophy.

Decreased sensation and numbness of limbs and facial skin.

Psychiatric symptoms: abnormal behavior, personality and character changes, etc.

Facial paralysis.

Choking on drinking water, difficulty in swallowing.

Slurred or labored pronunciation.

Ptosis of the eyelids, exophthalmos, inflexible eye movements, etc.

Exhibit of uncontrollable crying or laughing.

Accompanying Symptoms

Mumps virus encephalitis with enlarged parotid glands.

Herpes virus encephalitis with herpes on the skin.

In coxsackievirus and echovirus encephalitis, the following symptoms may accompany it.

Complications

Epilepsy.

Abnormal discharges occur when brain cells are damaged and epilepsy occurs.

This may be in the form of convulsions of the limbs, apnea, cyanosis of the face and lips, foaming at the mouth, and freezing.

Brain herniation and intracranial hypertension crisis

Edema and necrosis of brain tissue can lead to a sharp increase in intracranial pressure, causing the brain tissue to shift in the direction of low pressure.

It often manifests as headache, vomiting, coma, dilated pupils and even cardiac and respiratory arrest.

Systemic infection

Infections of the urinary system and lungs are caused by bed rest, impaired coughing and swallowing reflexes.

Often present with cloudy urine, fever, cough, sputum and other manifestations.

Consultation

Department of Medicine

Neurology

If fever, chills, cough, persistent headache, vomiting, etc. occur, prompt consultation is recommended.

Pediatrics

Infants and young children are advised to consult the doctor promptly if they develop recurrent fever, vomiting, screaming and crying, or drowsiness.

Emergency Department

If there is neck stiffness and limited movement, severe headache, generalized convulsions, drowsiness or coma, etc., it is recommended to go to the Emergency Department as soon as possible or call the 120 emergency number.

Preparation

Preparation for medical consultation: registration, preparation of information, common problems

Tips for seeking medical treatment

If you have a high fever, you can take physical measures to lower the temperature while waiting for medical treatment, such as warm towels to wipe the skin of the neck and armpits, and record the changes in body temperature. Self-application of antipyretic drugs before seeking medical treatment is not recommended as it may aggravate the symptoms or mask the condition.

If the patient loses consciousness, the patient’s mouth should be cleared of foreign objects and his/her head should be tilted to the side to prevent choking.

If the patient’s whole body is convulsing, remove dangerous objects from the surrounding area, and do not forcibly pry open the mouth or stuff towels or chopsticks in the patient’s mouth.

Children may not be able to describe their symptoms accurately. Parents can help to record the symptoms they have experienced so that they can give more reference to the doctor.

Checklist for preparing for medical treatment

Pay particular attention to the time of onset of symptoms, special manifestations, etc.

Is the headache severe? When does it get worse?

Is there a fever? How long did the fever last? What is the highest temperature?

Any twitching of limbs, weakness, abnormal sensations?

Is your appetite normal? What is your mental status?

Have you had chickenpox or shingles?

Have you been bitten by mosquitoes or traveled to a viral encephalitis infected area recently?

Have you been immunized?

Has there been contact with a person with viral encephalitis?

Test results in the last 6 months to bring to the doctor’s office

Laboratory tests: blood count, blood biochemistry

Imaging tests: cranial CT, cranial magnetic resonance imaging

Other tests: cerebrospinal fluid examination, electroencephalography

Medication for the past 3 months, if available, bring the box or package with you to the doctor.

Antivirals: acyclovir, ganciclovir, cidofovir, famciclovir

Other: acetaminophen, ibuprofen, prednisolone, carbamazepine

Diagnosis

Diagnosis is based on

medical history

History of exposure to patients with viral encephalitis.

History of herpes simplex virus and varicella-zoster virus infections.

Recent mosquito bites, visit to a viral encephalitis infected area or immunization.

Clinical manifestations

There may be systemic symptoms such as fever, headache, nausea and vomiting.

There may be neurological symptoms such as coma, convulsions, dysphagia, and limb weakness.

The doctor will check for abnormalities in vital signs, motor, sensory, and swallowing functions, as well as nerve reflexes through a physical examination.

Vital signs: Check whether blood pressure, heart rate, pulse, pupils, and breathing are normal and stable.

Motor function check: Observe whether you can complete movements such as lifting hands, sitting up, standing, walking, etc., and whether you need assistance.

Skin sensory examination: Slide a cotton swab over the patient’s skin or gently prick the skin with a blunt needle to assess the degree of sensory impairment according to the sensitivity to sensation.

Swallowing function test: Observe whether there is choking when drinking water to assess the swallowing function.

Tendon reflex examination

Meningeal irritation sign examination

Laboratory tests

Including blood routine, blood glucose, blood lipid, coagulation function, erythrocyte sedimentation rate examination, etc.

To understand the systemic condition and make a preliminary determination of the type of pathogen causing encephalitis.

Detect the virus in blood and cerebrospinal fluid to provide a basis for diagnosis.

Enzyme-linked immunosorbent assay or polymerase chain reaction.

Including complement binding test for epidemic encephalitis B, adenovirus, measles virus, poliovirus, influenza virus, etc., hemagglutination inhibition test, adenovirus immunofluorescence test, polio neutralization test.

Cerebrospinal fluid test (CSF)

Based on the changes of white blood cells and protein content in the cerebrospinal fluid, it can assist in determining the pathogens causing encephalitis.

Typical changes are lymphocytosis and a normal or mildly elevated white blood cell count.

Virus isolation can also be performed in the cerebrospinal fluid to detect associated antigens and antibodies.

Imaging

This includes cranial CT and cranial MRI.

Cranial MRI is the imaging method of choice for encephalitis.

It can show swelling and hemorrhagic changes in the involved areas, mostly with nodular or ring-like enhancement.

Precautions

Electrophysiologic examination

Includes EEG, evoked potentials.

May show changes associated with the disease.

Viral encephalitis can be seen as diffuse high amplitude slow waves, with unilateral or bilateral temporofrontal abnormalities being more pronounced, and even spike and spike waves in the temporal region.

Differential diagnosis

Acute purulent meningitis

Acute purulent meningitis has a rapid onset, starting with severe headache in the early stage, which is persistent and gradually aggravated.

Sometimes there is a strong explosive headache on the basis of persistent headache.

The headache often radiates to the shoulders, neck and back, and can be aggravated by physical exertion and coughing.

Tuberculous meningitis

Tuberculous meningitis starts slowly, mostly in children and young people, and early signs are not obvious.

Before the onset of the disease, there are often symptoms of tuberculosis poisoning such as night sweats, loss of appetite, emaciation, and poor sleep for 2 to 3 weeks.

Children often have convulsive seizures, depression, apathy, delirium, and in severe cases, coma and incontinence.

Viral meningitis

Viral meningitis is often acute or subacute.

The older the patient, the more severe the symptoms.

Positive signs are rare, and meningeal irritation is the only neurologic sign.

Treatment

Treatment goal: there is no specific treatment, control of intracranial pressure, high fever and convulsions as the focus of treatment.

Treatment principle: Drug treatment is the mainstay, together with traditional Chinese medicine and rehabilitation.

General treatment

Bed rest, reduce physical exertion.

Keep the respiratory tract open, and in serious cases, use the ventilator to assist breathing.

Maintain water-electrolyte balance.

Physical hypothermia is the mainstay when fever develops. Ice packs can be placed in the groin, armpits and neck, and cooling beds or cold mattresses can also be used.

Medication

Antiviral therapy

Commonly used drugs are acyclovir and ganciclovir.

Acyclovir: It is used for encephalitis caused by herpes simplex virus and has relatively few adverse effects.

Ganciclovir: It is used for encephalitis caused by cytomegalovirus infection, which may lead to renal impairment and bone marrow suppression, and is contraindicated in pregnant and breastfeeding women.

Drugs that inhibit virus replication in the body: iodoside, cytarabine, adenosine, etc.

Drugs that prevent the virus from penetrating into cells: amantadine, cyclooctylamine.

Drugs that cause the body’s cells to produce antiviral proteins: interferon, transfer factor.

Drugs that prevent virus adsorption: gammaglobulin, placenta globulin.

Symptomatic treatment

Can control the inflammatory reaction and reduce edema, limited to patients with severe or persistent cranial hypertension.

Commonly used drugs: dexamethasone, methylprednisolone.

Cautions: can not be used for a long time, pay attention to peptic ulcer, osteoporosis and other adverse reactions.

It can relieve cerebral edema and reduce intracranial pressure.

Commonly used drugs: mannitol, furosemide and so on.

Precautions: need to monitor urine volume and electrolytes during the use of drugs to avoid hyponatremia and renal function impairment.

Control seizures to avoid further aggravation of craniocerebral injury.

Commonly used drugs: midazolam, carbamazepine, sodium valproate, oxcarbazepine and so on.

Precautions

If there is emotional instability and irritability, diazepam, lorazepam and other drugs can be used for sedation.

Naproxen, ibuprofen, aspirin, etc. may be used as appropriate for severe headache.

If vomiting is frequent, metoclopramide can be used for symptomatic treatment.

Traditional Chinese Medicine (TCM)

Medication

Clearing heat and removing phlegm are the principles of treatment.

For those with phlegm-heat congestion, it is appropriate to remove fire and phlegm; for those with phlegm blocking the orifices, it is appropriate to remove phlegm and open the orifices; for those with phlegm-stasis obstruction, it is appropriate to remove phlegm and open the orifices, and to activate blood circulation and remove blood stasis. For those with phlegm and blood stasis blocking the collaterals, it is recommended to clear phlegm and open the orifices, and activate blood circulation.

Commonly used medicines: clearing plague and destroying poison drink, cleansing phlegm soup, Angong Niuhuang Pill, Niuhuang Qingxin Pill, Zixue Dan, etc.

Acupuncture and moxibustion

Acupuncture and moxibustion are mainly used to treat the symptoms, and the commonly used acupoints are as follows:

High fever and convulsion: Acupuncture Da Shi, Qu Chi, He Gu.

Difficulty in swallowing: Acupuncture Tian Tu, Nei Ting, He Gu, Lian Quan.

Aphasia, acupuncture mute door, Tongli, Lianquan, Hegu, Yongquan.

TCM treatment should be carried out under the guidance of a TCM physician in a regular hospital.

Rehabilitation treatment

Functional training for patients with residual neurologic sequelae, such as limb function training, speech and swallowing training, cognitive training.

Prognosis

Cure

Prognosis depends on the severity of the disease and whether the treatment is timely.

In most cases, patients with mild disease and timely treatment can be cured and have a good prognosis.

Patients with untimely or inadequate treatment and severe viral encephalitis can have a mortality rate of 60% to 80%.

Harmful

Causes brain damage.

Leaves different degrees of sequelae.

Patients with severe disease and poor basal condition can cause death.

Sequelae

Mental retardation.

Impaired consciousness.

Recurrent seizures.

Others: paralysis of limbs, muscles, etc.

Daily

Daily Management

Dietary management

Diet should be light and based on high protein and high vitamin diet.

Eat more fresh vegetables and fruits.

Eat more high quality protein, such as milk, soy products, eggs, lean meat and other foods.

Avoid cold, greasy and spicy stimulating foods, such as chili peppers, coffee and strong tea.

Abstain from alcohol.

Exercise management

Actively participate in exercises that are within your ability to enhance your physical fitness and immunity.

Start with low intensity exercise such as walking and gradually return to normal activities.

Work and rest management

Ensure adequate sleep and rest, and avoid exertion.

Keep a regular schedule and avoid staying up late.

Others

Keep the living environment quiet, with fresh air, suitable temperature, not too much light, and anti-mosquito measures.

Wash your hands and disinfect your food regularly, and pay attention to food hygiene to avoid diseases coming in from the mouth.

Keep indoor air circulating, and open the windows for ventilation when the air quality is good.

Keep a good mood.

Quit smoking.

Pay attention to protection, you can choose to go out and wear a mask.

Follow-up

Follow up with your doctor regularly.

If your symptoms do not decrease or even worsen, you need to see a doctor.

Blood tests, head MRI, lumbar puncture and other tests may be done during follow-up, so please be prepared in advance.

Prevention

Vaccination: e.g. inactivated encephalitis vaccine, mumps, measles, chickenpox, rubella, influenza vaccine.

Avoid traveling to areas where there have been outbreaks of viral encephalitis.

Avoid contact with people infected with the virus.

Avoid crowded enclosed places such as shopping malls and hospitals.

Wear a mask when going out.

Take rest and exercise properly to improve physical fitness and resistance.

Take care of balanced nutrition and ensure adequate intake of protein and vitamins.

Pay attention to mosquito prevention.