What Are the Common Causes of Encephalitis?

Encephalitis refers to inflammatory lesions of the brain parenchyma caused by pathogens. There are broad and narrow senses depending on the scope of the etiology. Narrow sense refers to the inflammatory changes in the brain caused by direct invasion of pathogenic microorganisms. A narrow concept is usually used. Most of the causes are viruses, and they can also be caused by infections such as bacteria, molds, Borrelia, Rickettsia, and parasites. Some may be allergic diseases, such as acute disseminated encephalomyelitis. The so-called encephalitis usually refers to viral encephalitis and post-infection encephalomyelitis, which are acute disseminated encephalomyelitis. It is divided into acute, subacute and chronic according to the course of disease; it is divided into bacterial, fungal and viral according to the pathogenic microorganisms; it is divided into epidemic and sporadic according to the epidemic situation. Encephalitis can occur in different genders and ages, mostly acute or subacute. It is clinically characterized by symptoms such as high fever, headache, vomiting, coma, and convulsions, and most of them are accompanied by changes in cerebrospinal fluid components. Prevention and treatment should be based on different causes.

Basic Information

English name

Encephalitis

Visiting department

Department of Infectious Diseases, Neurology

Common locations

brain

Common causes

Caused by viruses, bacteria, rickettsiae, parasites, etc.

Common symptoms

Fever, headache, nausea, vomiting, fatigue, disturbance of consciousness, meningeal irritation

Causes of encephalitis

Virus

Viruses do not have a cell structure, and are divided into two types according to the different nucleic acid components: one is DNA virus (DNA virus): including parvovirus, papilloma vacuole virus (causing progressive multifocal leukoencephalopathy), and adenovirus , Herpes virus, varicella-zoster virus. The other is RNA virus (RNA virus): including picornavirus (poliomyelitis virus, coxsackie virus, ECHO virus), arbovirus, orthomyxovirus (influenza virus), paramyxovirus (measles) Virus and mumps virus), grit virus (lymphocytic choriomeningitis virus), rhabdovirus (rabies virus). Viral encephalitis can be divided into acute, subacute, and chronic encephalitis according to the onset of the disease. According to the type of virus and the way of infection, it can be divided into arbovirus, enterovirus, respiratory virus, herpes virus encephalitis and so on. According to the incidence, it can be divided into epidemic and sporadic encephalitis. Acute encephalitis is generally considered to represent an acute viral infection, while subacute or chronic onsets such as subacute sclerosing panencephalitis and cortical striatum spinal cord degeneration represent a chronic viral infection.

2. Other

Bacteria (Bacterial Bartonella (Oroia fever), Bartonella and other species of the genus (cat scratch disease), Listeria monocytogenes, Mycoplasma pneumoniae, Corynebacterium gram-positive, Mycobacterium tuberculosis) , Rickettsia (granulocytosis, rickettsia, Q. rickettsii, rickettsia, rickettsia, Borrelia burgdorferi, Treponema pallidum) fungi (coccidioides, new Cryptococcus, capsular histoplasma), parasites (Amoeba, Plasmodium falciparum, Toxoplasma gondii, T. brucei subspecies Gambia, T. brucei subspecies Istera, Raccoon Bellis tapeworm, jaw Oral nematodes, Taenia solium) can cause encephalitis.

Clinical manifestations of encephalitis

Systemic toxemia symptoms

Fever, headache, body pain, nausea, vomiting, fatigue. A few have hemorrhoids and myocarditis.

2. Nervous system symptoms

Disorder of consciousness, meningeal irritation. There may be flaccid paralysis of the cervical and scapular muscles, causing the head to sag and the arm to be unable to lift up and shake. Cerebral nerve and lower limb involvement are rare. Paralysis can be recovered in 2 to 3 weeks, and about half of the muscles are atrophic. Mild symptoms without obvious neurological symptoms.

Because the location and severity of the lesions vary, the manifestations are diverse. Diffuse encephalitis is usually accompanied by general discomfort, and coma, convulsions, and fever may soon develop; brainstem encephalitis often has facial paralysis, cough, difficulty swallowing, numbness, weakness, and / or eye movement Paralysis, pseudoball paralysis and other manifestations. Pseudotumor encephalitis often has headache, vomiting, poor physical activity or paralysis, aphasia, mental symptoms, and intracranial hypertension. At the same time, pay attention to the primary symptoms, such as mumps virus encephalitis with parotid enlargement; herpes in the skin during herpesvirus encephalitis, and rash, myocarditis, hand, foot and mouth disease during coxsackie virus and ecovirus encephalitis. If the lesion involves the meninges (meningoencephalitis), a positive meningeal irritation sign appears.

Encephalitis examination

Nerve examination

Presence or absence of vision impairment, optic disc edema, paralysis of the eye muscles, hearing loss, dysphagia, limb paralysis, pathological reflexes, changes in muscle tone, ataxia, involuntary movements (tremor, dance-like movements, hand and foot movements), sensory disturbances , Urine retention, incontinence and meningeal irritation.

2. Auxiliary inspection

(1) General examination Blood routine: white blood cells (10-20) × 10 ⁹ / L, neutrophil elevation, urine routine, erythrocyte sedimentation, cerebrospinal fluid pressure, routine, biochemical, cytology, immunoglobulin (IgG, IgA, IgM ) Measurement and blood mixed rose wreath rate measurement.

(2) Electrophysiological examination EEG, brain-evoked (visual, auditory, somatosensory) potential.

(3) Imaging examination Brain CT or MRI examination.

(4) Immunological examination of virus infection. Enzyme-linked immunosorbent assay or polymerase chain reaction method is used to detect herpes simplex virus in blood and cerebrospinal fluid. Take two sera for complement binding tests for Japanese encephalitis, adenovirus, measles virus, polio, influenza virus, etc. (double sera titer increased more than 4 times or single sera titer 1: 16 or more can be diagnosed.), Hemagglutination inhibition test (double sera titer increased more than 4 times or single sera titer 1: 320 or more can be diagnosed) and adenovirus immunofluorescence test, polio neutralization test.

(5) Brain biopsy Immunofluorescence examination and pathological examination.

Encephalitis diagnosis

According to different pathogens, the route of infection, season of onset and age of onset are different. Because the location and severity of the lesions vary, there are a variety of manifestations, which are diagnosed based on examination and clinical manifestations.

Acute viral encephalitis

(1) Symptoms of infection, such as fever, general malaise, myalgia, and sore throat, can be from several days to several weeks, and some cases can have sudden fever, with a heat course of about 7 to 10 days. A few have bleeding rash. White blood cells were normal or increased to (15-30) × 10 / L.

(2) Meningeal irritation and cerebrospinal fluid changes Cerebrospinal fluid pressure is normal or increased, white blood cells increase, mainly lymphocytes. In the early stage of encephalitis caused by arbovirus, neutrophils account for the main component. Sugar is normal or slightly higher, a few can be reduced. The protein can be slightly increased to 0.5 to 1 g / L, and red blood cells can be present in the cerebrospinal fluid of herpes simplex virus encephalitis. Cerebrospinal fluid can be completely normal in a few cases of acute viral encephalitis.

(3) Local or diffuse encephalitis symptoms There are mental symptoms, delirium, coma and other conscious disturbances, convulsions, aphasia, strong grip, sucking reflexes, hemiplegia. Tendon reflexes are asymmetric, and pathological reflexes are positive. Brain damage includes cerebral palsy and autonomic nervous system dysfunction. Cerebellar damage includes nystagmus, ataxia, and inability to rotate.

(4) Relevant signs of primary lesions, such as measles, chicken pox, mumps, or infectious mononucleosis. Some cases are marked by mental symptoms or high intracranial pressure symptoms. For example, the lesion is mainly in the brainstem called brainstem encephalitis. Different types of viral encephalitis can also have their special manifestations.

2. Lentiviral encephalitis and encephalopathy

Known are: subacute sclerosing panencephalitis, progressive multifocal leukoencephalitis, degeneration of the cortical striatum and spinal cord, and Kuru disease.

Lentivirus infection is characterized by a long incubation period between infection and onset, from months to years or even decades. Subacute or chronic onset. Patients have immunodeficiency, mainly cellular immunodeficiency. The central nervous system lesions were diffuse and multifocal.

3. Several other viral encephalitis

(1) Mumps encephalitis virus directly invades the brain, most of which are symptoms of meningitis, severe headache, drowsiness, vomiting, positive meningeal irritation, non-purulent changes in cerebrospinal fluid, hemiplegia, and quadriplegic paralysis , Vision loss, deafness, epilepsy, altered consciousness, hearing loss, aphasia, etc. Mumps often occur at the same time or successively with encephalitis, and the general diagnosis is not difficult. Those without mumps can confirm the diagnosis by serum immunological examination.

(2) Shingles encephalitis Rarely, meningitis and encephalitis occur in individual cases after herpes on the trunk or head and face. Children are first affected by the cerebellum; they are usually self-limiting or have severe encephalitis; they often have insanity.

(3) Cytomegalovirus encephalitis Extensive evidence of cytomegalovirus infection, such as retinitis, local pneumonia, and myelitis, are mostly fetal and neonatal infections, occasionally seen in children and adults. Most of them show microcephaly of brain dysplasia, calcification around the ventricles and in the brain, and hydrocephalus. Adults can present with acute polyneuritis. Any infant with small head deformities, especially with choroiditis, retinal calcification, cataracts, and optic nerve atrophy, should be suspected of this disease. Specific antibodies were found in the blood of 44% of children. Can try adenosine therapeutic diagnosis.

(4) Progressive rubella encephalitis refers to encephalitis in which a mother develops rubella during pregnancy and the child is less than 14 years old after birth. Symptoms are progressive, headaches, dazzling, rashes within 1 to 6 days after abnormal behavior, may have epilepsy, deafness and dementia. Or show various brain developmental abnormalities. Acquired rubella encephalitis symptoms are mild, no special treatment is required, and the prognosis is good. Virus isolation and serum immunoassay during infection can confirm the diagnosis.

(5) Infectious mononucleosis (EB virus) encephalitis occurs in the case of systemic diseases, and occasionally occurs before blood and visceral symptoms. May have paralysis, aphasia, hyperactivity, neurological damage to the cerebellum, ataxia and paraplegia, cranial nerve palsy, deep coma, personality changes, epilepsy, etc. Typical haematology and heterophilic antibodies can confirm the diagnosis.

Differential diagnosis of encephalitis

Acute purulent meningitis

The onset is rapid, and it starts with severe pain in the head at an early stage. It is persistent and gradually worsens. Sometimes there is a burst-like headache on the basis of persistent headache. This headache is often radiated to the shoulder, neck and back. Headaches can be aggravated by physical exertion and coughing.

2. Tuberculous meningitis

The onset is mostly slow, more common in children and young people, and symptoms of tuberculosis often last 2 to 3 weeks before the onset. It can manifest as low fever, night sweats, loss of appetite, weight loss, and poor sleep. In the onset, all headaches are the main cause, and the degree of headache changes greatly. Some headaches are severe, accompanied by nausea and vomiting, and some are dull and swollen. They last for a long time. Children often have seizures, accompanied by mental weakness, indifference, delirium, and severe cases may have coma and incontinence. Early signs are not obvious, and typical signs of meningeal irritation and nerve localization appear in the later stages, such as abduction nerve and oculomotor nerve palsy, monoplegia or hemiplegia.

3. Viral meningitis

The clinical manifestations are acute or subacute onset. The clinical symptoms of viral meningitis for various reasons are very similar, with severe headache, persistent head pain, accompanied by fever, strong neck, nausea, vomiting, burnout, dizziness, neck back Pain. The older you get, the worse your symptoms are. Physical examination is rarely positive, and meningeal irritation is the only sign of the nervous system.

Encephalitis complications

The common complication is bronchopneumonia, which is more common in patients with coma or bulbar palsy, in addition to myocarditis and cold sores. If there are irregular breathing rhythms or pupils of different sizes, the possibility of intracranial hypertension and cerebral hernia should be considered.

Encephalitis treatment

There is no specific treatment for viral encephalitis. Controlling intracranial hypertension, fever, and seizures is particularly important. Patients in coma need to keep the airway open. Careful care prevents secondary infections.

Symptomatic treatment

(1) Glucocorticoid Hydrocortisone or dexamethasone, added intravenously in 5% glucose solution. Start with a larger dose and gradually decrease, the course of treatment does not exceed 1 month.

(2) Intravenous dehydration and diuretic 20% mannitol, the course of treatment depends on the condition.

(3) Cooling It is mainly based on physical cooling. It can be wiped with 30% alcohol, and ice packs can be placed in the groin, underarms and neck. It can also be a cooling bed or a cold mattress.

(4) Antipsychotics For psychomotor excitement, chlorpromazine, perphenazine or Telden can be given. The dose should be individualized.

(5) Reduce intracranial pressure

2. Antiviral treatment

(1) Acyclovir, iodoside, cytarabine, adenosine arabine, etc.

(2) Amantadine and cyclooctylamine.

(3) Interferon intramuscular injection, the course of treatment depends on the condition, early application.

(4) gamma globulin and placental globulin.

Encephalitis prognosis

Sequelae is mainly the most common muscle paralysis left after brain and bulbar lesions, mostly paralysis of one or both upper limbs. Disorders of consciousness, and even decortical status, to varying degrees. Most of the symptoms of increased intracranial pressure can be completely recovered, but a small number of residual sequelae such as epilepsy, limb paralysis, and retarded development.