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Introduction to Brain Infections

By

John E. Greenlee

, MD, University of Utah School of Medicine

Last full review/revision Jul 2020| Content last modified Jul 2020
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Brain infections can be caused by viruses, bacteria, fungi, or, occasionally, protozoa or parasites.

Certain noninfectious disorders can mimic encephalitis. An example is the autoimmune condition anti-NMDA (N-methyl-d-aspartate) receptor encephalitis, which involves an autoimmune attack on neuronal membrane proteins.

Brain infections often also involve other parts of the central nervous system (CNS), including the spinal cord. The brain and spinal cord are usually protected from infection, but when they become infected, the consequences are often very serious.

Infections may cause the meninges to become inflamed (meningitis) Overview of Meningitis Meningitis is inflammation of the meninges and subarachnoid space. It may result from infections, other disorders, or reactions to drugs. Severity and acuity vary. Findings typically include... read more . Often, bacterial meningitis spreads to the brain, causing encephalitis, infecting mainly the brain parenchyma. Similarly, viral infections that cause encephalitis often also cause meningitis. Technically, when both the brain and the meninges are infected, the disorder is called meningoencephalitis. However, the term meningitis is usually used to refer to infection that affects mainly the meninges, and encephalitis is usually used to refer to infection that affects mainly the brain.

CNS infections may manifest as follows:

Brain involvement may also be a manifestation of postinfectious mechanisms, such as acute disseminated encephalomyelitis.

Bacteria and other infectious organisms can reach the brain and meninges in several ways:

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Overview of Meningitis
Meningitis is defined as inflammation of the meninges and subarachnoid space and may be classified under several different categories. Of these categories, which of the following types is particularly serious due to the speed of its progression? 
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