What is encephalitis?
L'encephalitis it's a'inflammation affecting thebrain, what is commonly called the brain. It is a very serious condition of the nervous system which needs immediate treatment at the time of diagnosis, but it is also a very rare condition, as it more easily affects people with a poorly efficient immune system (children or immunosuppressed).
Causes of encephalitis
What are the causes of encephalitis? The main ones causes of encephalitis I'm:
- viral infections (viral encephalitis);
- changes in the immune system (autoimmune encephalitis);
- bacterial infections (bacterial encephalitis);
- protozoal infection (protozoal encephalitis);
- fungal infections (fungal encephalitis);
- presence of bacterial toxins (botulism and tetanus);
- presence of prions (spongiform encephalitis)
- changes in liver function (hepatic encephalopathy).
The viral encephalitis are divided into primary or secondary, on the basis of whether the virus directly affects the brain (and the spinal cord, in the case of viral encephalomyelitis) or indirectly, through the alteration of the immune reaction and its aberrant and unmotivated activation against the organism itself following a previous contagion: this is the pathogenesis of a family of post-infectious encephalitis, which is called ADEM or Acute Disseminated Encephalitis Myelitis and to which pathologies such as Bickerstaff's encephalitis belong.
The main pathogens responsible for brain infection are: Herpes Simplex Virus (which gives rise toherpetic encephalitis), Varicella Zoster Virus (which generates chickenpox encephalitis), various Enteroviruses, the rabies virus, Arbovirus and Flavivirus (a virus of this family is the cause of an encephalitis typical of areas of South-East Asia, called Japanese Encephalitis). There are pathologies in which there is the hypothesis of a viral involvement, but without any type of evidence (examples arelethargic encephalitis and theRasmussen's encephalitis). A classification of all encephalitogenic viruses has been made according to the reservoir used:
- there are extra-human reservoir viruses (rabies virus, Arbovirus), which use small animals, such as insects and arthropods, as transmission reservoirs. An example is tick-borne encephalitis, which is due to the bite of ticks of the genus Ixodes;
- there are human reservoir viruses, which are the majority of encephalitogenic viruses and which give rise to sporadic encephalitis.
In recent times, degenerative-like encephalitis caused by slow-growing viruses, such as measles virus (which causes SSP, or Pan Subacute Sclerosing Encephalitis), of rubella (causing the progressive rubeolic panencephalitis) , the JC papovavirus (which causes Progressive Multifocal Leukoencephalopathy, or LMP) or HIV-1 virus.
The autoimmune encephalitis they are characterized by an aberrant and improper response of the immune system against healthy tissues, inducing even very serious damage in them. An example of this is limbic encephalitis which, despite its name, rarely affects the limbic lobe. Autoimmune encephalitis can often affect the brain and spinal cord together, giving rise to a clinical overlap between encephalitis and myelitis, called Autoimmune Encephalomyelitis.
The bacterial encephalitis they are mainly caused by streptococci, Borrelia Burgdorferi, Bartonella Henselae and Mycoplasma Pneumoniae. These can reach the brain by contiguity (propagation from a neighboring infectious process), by blood from septic foci (more easily pulmonary), or through a chronic penetrating wound. This formation will most frequently be located in the areas of vascularization of the middle cerebral artery and in the temporal and frontal lobe. The reaction of our body to this colonization will be to form a brain abscess, that is an inflammatory process circumscribed by a capsule of fibrous tissue and which has dead nerve tissue, bacteria and pus in the center.
Amoebic encephalitis and other types
The protozoal encephalitis and the fungal encephalitis they are very rare in the world. Noteworthy is a very serious and very high percentage lethal form, called Primary amoebic meningoencephalitis (or PAM), caused by protists, the amoebas, which feed on brain cells.
Symptoms of encephalitis
What are the main ones manifestations of encephalitis? With which symptomatology of presents? The symptoms mainly depend on the type of pathogen causing theencephalitis. In the event that a bacterium, we have a symptomatic set and a fairly typical course:
- the onset is quite insidious, characterized by headache, fever and generalized fatigue;
- it is followed by a clinical latency period of several weeks to several months;
- subsequently we have a rapid worsening of the patient's condition due to the formation of the abscess, which produces a compression of the healthy nervous tissue. In this phase we can find signs of intracranial hypertension, disturbances of consciousness and a whole series of heterogeneous deficits linked to the compression of the different brain areas, each having a different function. These are associated with general signs of infection, such as high fever, increased white blood cells, marked fatigue and anorexia.
If at the base of the infectious process we find a virus, we can have a much more heterogeneous clinical picture depending on the cell-virus relationship starting from its attachment to the cell membrane. It is based on a specific symptomatological triad:
- signs of ongoing infectious process;
- signs of general brain distress, such as disturbed consciousness and seizures;
- signs of focal brain distress, depending on the site of infection.
Viral encephalitis symptoms: viral disease classically has a two-phase course:
- a first phase, characterized by general infectious signs and symptoms (nausea, dizziness and flu-like disorders) lasting a few days, followed by a complete regression of the symptoms. This phase corresponds to the first infection with brain inflammation and the subsequent distribution of the virus in the body;
- a second phase, characterized by neurological signs and symptoms, in which the virus is localized in thebrain.
Complications and consequences of encephalitis
If the diagnosis of encephalitis is late, it can be done consequences important or even permanent late neurologicals. The first to consider are the disturbances of the state of consciousness, which may be absent as present to the point of causing a state of deep coma.
Secondly, attention must be paid to disorders of localized involvement of the infection, such as language, memory, motor disorders and the genesis of epileptic seizures; subsequently we can find motility disorders, such as paralysis, tremors, hyperkinesis, poor motor coordination; Rare, however, is the finding of sensitivity disorders, but frequent and serious are the lesions of the optic pathways, which can lead to complete bilateral blindness. Meningeal involvement by the virus is also frequent, thus giving rise to a picture of meningoencephalitis, in which the signs and symptoms of the two pathologies overlap.
Diagnosis of encephalitis
There diagnosis of encephalitis from bacterial it is very complex if based solely on the clinic. The finding of the abscess collection with its fibrous capsule in neuroradiological imaging examinations is important: CT and MRI clearly show a hypodense lesion surrounded by abundant edema and a ring that becomes hyperdense after the injection of contrast medium intravenously. However, this picture is also shared by other pathologies, such as brain metastases and some brain tumors such as glioblastoma. Therefore, to solve this doubt, it is useful to resort to the execution of a scintigraphy, which uses lymphocytes labeled with a radioactive isotope that will be captured by the abscess lesion and will allow a diagnosis with a greater degree of safety.
There diagnosis of encephalitis from viral, instead, it starts from the clinic: the doctor must suspect this pathology if there are different neurological and infectious signs and symptoms in a patient who has frequent disturbances of consciousness. Often an examination of the Cephalus-Rachidian Liquor (LCR) through a procedure of rachicentesi it allows to demonstrate the concomitant involvement of the meninges and to isolate, through complex methods, parts of the virus in question dispersed in this fluid, leading to a precise etiological diagnosis.
Performing an electroencephalogram (EEG) does not always lead to the finding of clear results: it may happen to encounter frankly pathological but non-specific waves. Only in rare cases, as in the SSP, can we find a characteristic and suggestive path of the disease. Neuroimaging investigations often show intraparenchymal brain lesions with different signal alterations based on the virus involved.
Treatment and treatment of encephalitis
Bacterial encephalitis therapy
There therapy ofbacterial encephalitis depends on when the diagnosis is made:
- in general, for flu-like symptoms, anti-inflammatories are given, such as paracetamol and ibuprofen, with plenty of fluids and a period of absolute rest;
- if it occurs in the initial period of symptomatological onset, when the capsule is not yet well formed, a powerful antibiotic therapy can completely resolve the picture with a good success rate. Initially, we proceed with empirical antibiotic therapy, based on the bacterial agents most frequently involved, pending the antibiogram, which will allow the doctor to choose the best therapy to neutralize the pathogen;
- if the abscess is already formed, the only effective treatment is neurosurgery to excise the abscess. There are not a few cases in which, following excision, a diagnosis of abscess is made through the histological examination of the removed tissue.
Viral encephalitis therapy
In the case of acute viral encephalitis primary, it is important to distinguish the trigger of encephalitis. For some of them, effective antiviral drugs are available (aciclovir, ganciclovir, valanciclovir), such as in Herpes Virus infections and Varicella Zoster encephalitis, which are not free from serious side effects; for others, however, no type of drug is available.
There are forms of encephalitis, for example in that caused by the rabies virus, in which prophylaxis by means of vaccines specific and completely harmless. In secondary cases, important are the measures aimed at reducing the severity of the immune system: corticosteroids are mainly used (although, after a long period, they can give several side effects), immunoglobulins or, if the first two are ineffective. principals, resort to plasmapheresis, a sort of "washing" of the blood to remove the cells that cause inflammation.
In the case of encephalitis of autoimmune origin, they are used corticosteroids is immunosuppressants (azathioprine, prednisone, dexamethasone, methylpredinisolone), to reduce the number of immune system cells that react against the body. If these medicinal products do not at least partially resolve the clinical picture, plasmapheresis can be used.
Prognosis of encephalitis
Without treatment, the prognosis of encephalitis is negative. In 10% of cases, the patient dies, while the rate of long-term or even permanent complications is much higher. In case of healing, the therapeutic path and the rehabilitation it can also be very long.Tags: Brain Infectious diseases Neurology Virus