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Brain Infection

A virus, bacteria, fungus, or parasite can all cause a brain infection. The spinal cord and other areas of the central nervous system (CNS) are frequently affected as well.

There are various forms of brain infections, and each one affects the brain in a unique way:

  • Encephalitis, inflammation of the brain
  • Meningitis, inflammation of the lining of the brain and spinal cord (the meninges)
  • Traverse myelitis, inflammation of the spinal cord
  • Cerebral abscess, a pocket of pus in the brain
Brain Infection

Due to the swelling of the brain or spinal cord, inflammation, the body's normal response to infection, can cause both physical and neurological symptoms. Abscesses cause damage by putting pressure on the parenchyma, the functioning tissues of the brain.

This article examines the causes and symptoms of four prevalent forms of brain infections. Additionally, it describes how brain infections are detected, handled, and avoided.

Types of Brain Infections

The causes and locations of the various forms of brain infections varies. Some, like encephalitis, affect the entire brain, while others, like an abscess, are restricted to a specific region of the brain. But every kind of brain infection needs to be treated straight away.


In the United States, arboviruses, or the herpes simplex types 1 and 2 are the most common viruses to cause encephalitis. Arboviruses cause illness that is carried by mosquitoes and are transmitted from animals to people. The West Nile virus is one illustration. Mild flu-like symptoms and headaches may first present, but these are often swiftly followed by behavioural abnormalities, hallucinations, and confusion.


A virus or bacteria may be the source of meningitis. Meningitis caused by bacteria is a dangerous infection that needs to be treated right away. Rarely, a parasite or fungus can also cause meningitis. Numerous bacteria can first produce an upper respiratory tract infection before moving on to the brain via the circulation. When specific bacteria directly enter the meninges, bacterial meningitis can also result. Meningitis is typically characterised by sudden onset of fever, severe headache, stiff neck, photophobia, nausea, and vomiting. Meningitis can be detected if patients are unable to lower the chin to their chest. The signs and symptoms may initially resemble a cold or upper respiratory infection, but they can quickly worsen.

Are Meningitis and Encephalitis Contagious?

Contagious bacterial meningitis and encephalitis can spread through close contact in some cases. On college campuses, one kind of meningitis is frequently seen. Doctor may prescribe a prophylactic course of antibiotics if patient recently came into touch with someone who has bacterial meningitis or encephalitis.

Traverse Myelitis

The spinal cord oversees sending motor instructions from the brain to the body and returning sensory data to the brain. Pain, limb weakness, bowel and bladder issues, and sensory issues can all occur when it is inflamed, as in the case of transverse myelitis. Along with muscle spasms, headaches, fevers, and appetite loss, myelitis commonly affects large numbers of people. An immunological problem or an infection from a virus, bacteria, fungus, or parasite may be the cause of myelitis. Most myelitis patients fully recover; however, it can take months or years. Myelitis cannot be cured; however, the symptoms can be managed.

Cerebral Abscess

When a buildup of pus becomes encased in brain tissue, it develops into a cerebral abscess, also known as a brain abscess. This uncommon illness may result from trauma or surgery, as well as from bacterial or fungal infections. The likelihood of developing a brain abscess is higher in people with weakened immune systems. High fever, excruciating headache, altered behaviour, nausea, and vomiting are among symptoms. Speech abnormalities, muscular weakness, stiffness, and seizures can all develop over time as a result of an abscess. An abscess must be detected, surgically drained, and then treated with antibiotics for four to eight weeks after it is found.


There are many different causes of brain infections, and each one has a unique method of transmission. By sharing drinking glasses or kissing, for example, or by respiratory secretions, viruses can be transmitted through intimate contact. Close touch or contaminated food preparation can potentially spread bacterial illnesses.

Here is a list of all the reasons why brain infections might occur:

  • Virus: Several viruses have the potential to infect the brain, spinal cord, or surrounding tissues, albeit this is unusual. Herpes simplex, varicella zoster, cytomegalovirus, Epstein-Barr, and influenza viruses are a few examples of potential causes. West Nile and Zika, two mosquito-borne diseases, may also cause brain infections.
  • Bacteria: In the United States, Streptococcus pneumoniae, group B Streptococcus, Neisseria meningitidis, Haemophilus influenzae, and Listeria monocytogenes are the bacteria most likely to cause a bacterial brain infection.
  • Fungus: There are several fungi that can cause a fungal infection to spread to the brain, including Aspergillus, Blastomyces, Coccidioides, and Cryptococcus.
  • Parasite: It's possible for toxoplasmosis, cysticercosis, schistosomiasis, or strongyloidiasis to infect the brain with parasites.
  • Immune system disorders: Chance of developing a brain infection may increase if the immune system is already impaired for any reason. Rare infections like a brain abscess are more common in HIV-positive individuals. Myelitis may also result from multiple sclerosis.


The location of the diseased brain tissue and the infection's severity will both affect the symptoms of a brain infection. Each form of brain infection has different signs, which are as follows:

  • Meningitis: Nausea, vomiting, photophobia, severe headache, stiff neck, and sudden fever.
  • Encephalitis: Headache, altered level of consciousness, behavioural changes, hallucinations.
  • Myelitis: Arms and legs weakness, sharp pain, numbness and tingling, and bowel and bladder issues.
  • Abscess: High fever, excruciating headache, altered behaviour, nausea, and vomiting.


Symptoms and the results of physical exam will determine the diagnostic method utilised to identify the brain infection. A medical professional should be consulted straight soon to assess any signs of a brain infection. Doctor will conduct a neurological examination to assess the motor and sensory function if they are worried about a brain infection.

Healthcare professional may suggest the following tests following a complete history and physical examination:

  • Imaging studies: To find lesions or inflammation in the brain or spinal cord, imaging studies are used. An abscess or lesion in the brain can be found with a brain MRI, as well as an underlying disorder like multiple sclerosis that may be the source of the symptoms. Inflammation may be found with a brain CT scan.
  • Blood cultures: Blood cultures will be taken to identify the particular bacterial species causing the infection if a bacterial infection is suspected. The most potent antibiotic will then be chosen using this information.
  • Lumbar puncture: To retrieve cerebrospinal fluid, which circulates through the brain and spinal cord, a lumbar puncture, also known as a spinal tap, entails inserting a needle between the vertebrae in the lower back. Testing for germs, proteins, or elevated white blood cells could be performed on this fluid.


Depending on the sort of illness the patient has, course of treatment will vary. However, prompt treatment is crucial for reducing complications and serious symptoms, so patient should never delay in seeing the doctor if he/she have any concerns.

The following therapies can be used to treat a brain infection:

  • As soon as a bacterial infection is suspected, antibiotics are started. The medical team will most likely start IV antibiotics while awaiting test results if patients are being assessed for meningitis.
  • The purpose of corticosteroids is often to reduce inflammation in the brain or spinal cord. Inflammation is a common component of brain infections, and this inflammation can put pressure on the brain and spinal cord and cause catastrophic problems. A corticosteroid may assist in lowering immune system activity and oedema.
  • If medical team believes a virus is to blame for the brain illness, antiviral treatments will be recommended. The typical practise is to immediately prescribe an antiviral medication if patient exhibit encephalitis symptoms.


The severity of the disease, the source of the infection, and how quickly treatment was started all affect the prognosis for a brain infection. Most persons who suffer from a brain infection recover completely.

Long-term healing may require the following therapies:

  • Occupational therapy, physical therapy, and psychotherapy

Depending on the level of brain inflammation, recovery from a brain infection will differ. Inflamed brain tissue can occasionally result in coma and death.

Survival and Mortality

The location of the illness, the type of infection, and other factors can all affect the chance of death (mortality).

  • Encephalitis: No matter the type of illness, between 5% and 20% of encephalitis patients die in the hospital.
  • Meningitis: The most common cause of bacterial meningitis, streptococcus pneumonia, carries a 17% mortality risk among hospitalised patients.
  • Traverse myelitis: The typical survival time from the time of diagnosis is 8-9 years, according to some studies, with some people living up to 16 years. Shorter survival periods are correlated with older age and tobacco usage.
  • Cerebral abscess: Even though studies differ, most seem to indicate that the in-hospital mortality rate for those with a brain abscess is around 16%. cases frequently involve the bacterium streptococcus.


Although a brain infection cannot always be avoided, getting vaccinated is a useful precaution to take. The following vaccines can currently prevent many causes of bacterial brain infections:

  • Pneumococcal immunisations help prevent from S. pneumoniae.
  • Meningococcal vaccines help protect against N. meningitidis.
  • Hib vaccinations aid in preventing Hib.

Take routine precautions like washing hands and avoiding contact with sick people to prevent viral and bacterial infections that can spread to the brain.

Use insect repellent and wear long sleeves and trousers when outdoors to guard against diseases spread by ticks or mosquitoes that could cause a brain infection. When mosquitoes are more active at night, try to limit outdoor activities, and take care of any standing water near home area.

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