In detail

Infections of the Central Nervous System (CNS)

Infections of the Central Nervous System (CNS)

The central nervous system (CNS) is the part of the body's nervous system that includes the brain and spinal cord. It controls most of the functions of the body and the mind. Like any other part of the body, it can be infected by bacteria, viruses, fungi and other infectious agents.An infection of the central nervous system can be a life-threatening condition, especially in children with weakened immune systems. Others can have equally devastating effects that only appear progressively years after infection. These infections need a rapid diagnosis and immediate treatment by an infectious disease specialist. Bacteria, fungi and viruses are the most common causes of central nervous system infections.


  • 1 Meningitis
  • 2 brain abscesses
  • 3 HIV infection
  • 4 Herpetic encephalitis
  • 5 Neurosyphilis
  • 6 Creutzfeldt-Jakob disease


Meningitis is an infection that causes the protective membranes of the nervous system to swell. Inflammation of the brain and spinal cord can affect all parts of your body. Fever and other symptoms may appear suddenly and progress very fast, causing devastating effects.

The viral meningitis It can make us very sick, but it often leaves no lasting effects. Bacterial meningitis instead is much more serious. It progresses rapidly and can cause permanent damage or even endanger life.

Rapid diagnosis and treatment can help prevent some of the possible long-term side effects. Anyone can get meningitis, but it is most common in babies, children and adolescents.

Meningitis symptoms

Headache may be an early warning sign of meningitis. Inflammation of the brain can cause numerous problems, including cognitive disorders and seizures. Problems with memory and concentration may last until long after the disease has passed. Children may have persistent learning difficulties.

Swelling in the brain can also interfere with the senses. May cause ringing in the ears (tinnitus), partial deafness or total deafness. May cause speech problems, sensitivity to light, eye pain and even loss of vision.

Inflammation and fever can cause loss of appetite. The stomach upset, the nausea and vomiting They are common. Babies and young children can become fussy, irritable and hard to comfort. And the drowsiness Excessive is a symptom of meningitis, so it can be difficult to wake a sleeping child. If left untreated, meningitis can lead to coma.

Bad coordination, dizziness and clumsiness may persist for a while after treating meningitis. Children may have emotional problems after illness, such as anxiety, moodiness and sleep disturbances.

Brain abscesses

An abscess is a focus of infection. These can come from infections of distal parts of the body that reach the nervous system through the blood, from contiguous foci, such as dental or ear infections, or by direct introduction of pathogens after penetrating cranial lesions or surgical interventions. They are treated with surgery and / or antibiotics. Its neuropsychological effects are typical of a space-occupying focal lesion, that is, they depend on their location and the compression they cause on the tissue.

Image obtained by MRI where several ring-shaped lesions that correspond to brain abscesses are observed.

HIV infection

The AIDS virus, in addition to infecting the cells of the immune system, can also infect the cells of the Central Nervous System.

In HIV-infected patients, neurological involvement may occur due to direct infection of brain cells. or due to opportunistic infections or tumors that affect the nervous system.

In some HIV-positive individuals who have not yet developed AIDS, poor performance can be observed in some neuropsychological tests, especially in attention, memory, processing speed, denomination or motor coordination tasks. This is a reversible state with current treatments that can stop the evolution of the virus.

Dementia-AIDS complex

We consider that a seropositive individual develops AIDS when he presents some of the diseases that are associated with this state of immunosuppression. The diseases that most frequently present these patients are pneumonia, Kaposi's sarcoma (a type of cancer) and AIDS-associated dementia.

Among the individuals who develop the disease, a high percentage will present dementia. For some patients, dementia may be the first symptom of the disease, or even the only one.

AIDS-associated dementia is a subcortical dementia.

Therefore, these patients will have a deterioration similar to that seen in other subcortical dementias. In the study of pathological changes in the cerebral plane, it is observed white matter involvement and atrophy of subcortical structures, but the bark is normally preserved.

Once dementia has developed, it is irreversible. Generally, other systemic and nervous system infections will also be observed, which will aggravate the patient's condition.

Herpetic encephalitis

It is a very serious disease caused by infection by the herpes simplex virus. Many patients do not survive the acute phase of the disease, although rapid treatment with antivirals (such as acyclovir) can stop its course.

In herpetic encephalitis, an exclusive affectation of the frontal and temporal lobes is observed.

Image obtained by MRI showing the exclusive involvement of the left temporal lobe in a patient affected with herpetic encephalitis.

Surviving patients show a very severe memory impairment (due to the destruction of the hippocampus), alteration of emotional behavior (due to the destruction of the tonsil and frontal lobes) and alteration of all functions related to the prefrontal cortex.


Also known as neuroluas, is observed in a 20% of patients with syphilis. It can affect the meninges or brain tissue in various ways, in some cases shortly after infection, but in others at twenty years or more. One of its manifestations is progressive general paralysis (PGP), which causes atrophy of cortical cells, especially those of the frontal lobe, and cause dementia, psychiatric disorders and motor impairment.

Creutzfeldt-Jakob disease

This is a disease that is part of the group of spongiform encephalopathies.

It is produced by infection through a prion, which is a protein.

Forms of infection include contact with infected nerve tissue, contaminated surgical material or by ingestion of infected meat from some animals.

For some years there was an important social alarm around this disease, mainly due to the evil of the "crazy cows". Very little is known about prions, the infectious agent that transmits this disease. They are proteins, and it seems that their effect is to interfere with the synthesis of some protein in the cells of the central nervous system. The protein that causes damage to sheep can infect cows, but not humans. The protein that causes damage to cows, on the other hand, can infect humans, but it seems that a certain consumption or genetic predisposition is necessary to develop the disease.

Among the natives of some Papua New Guinea tribes this is an endemic disease, which is known as kuru. It seems to be related to the ritual consumption of the brain of the dead.

Infection is not the only way to get Creutzfeldt-Jakob disease. In some cases it is hereditary. Some families mistakenly synthesize the protein responsible for the disease without the need for any prion to interfere with this process. The course of the disease is similar to when it develops due to infectious cause. In this case, it usually appears between the ages of forty and fifty.

It produces a rapidly evolving and irreversible cortical dementia, which leads to death in about a year.


Bradford, H.F. (1988). Fundamentals of neurochemistry. Barcelona: Labor.

Carpenter, M.B. (1994). Neuroanatomy Fundamentals Buenos Aires: Panamerican Editorial.

Diamond, M.C .; Scheibel, A.B. and Elson, L.M. (nineteen ninety six). The human brain Work book. Barcelona: Ariel.

Guyton, A.C. (1994) Anatomy and physiology of the nervous system. Basic Neuroscience Madrid: Pan American Medical Editorial.

Martin, J.H. (1998) Neuroanatomy. Madrid: Prentice Hall.

Nolte, J. (1994) The human brain: introduction to functional anatomy. Madrid: Mosby-Doyma.

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