A brain infection refers to an infection caused by viruses, bacteria, fungi, or parasites that affects the brain , spinal cord , or the surrounding area. Brain infections are serious and can be life-threatening.

    Infections and conditions affecting the brain and spinal cord can activate the immune system, leading to inflammation . These diseases and the resulting inflammation can produce a wide range of symptoms, including fever, headache, seizures, and changes in behavior or confusion. In extreme cases, they can result in brain damage, stroke , or even death.

    There are different types of brain infections, and each type has its own unique cause and treatment. Encephalitis refers to inflammation in the brain, and meningitis is inflammation of the meninges, the membranes that surround the spinal cord. Myelitis refers to inflammation of the spinal cord, and a brain abscess describes a collection of pus in the brain. Infections of the brain require emergency treatment.

    Verywell / Sydney Saporito


    The different types of brain infections vary by cause and location. Some like encephalitis affect the entire brain, while others are localized to one area of the brain, such as an abscess. However, each type of brain infection requires treatment right away. 


    Meningitis can be caused by a virus or bacteria. Bacterial meningitis is a serious condition and needs to be treated immediately. Rarely, meningitis can also be caused by a fungus or parasite. 

    Several types of bacteria can first cause an upper respiratory tract infection and then travel through the bloodstream to the brain. Bacterial meningitis can also occur when certain bacteria invade the meninges directly.

    The classic signs of meningitis include a sudden fever , severe headache , stiff neck, photophobia , and nausea and vomiting. Being unable to bend your chin down to your chest is a sign of meningitis. While the symptoms may start out resembling those of a cold or upper respiratory infection, they can quickly become more severe. 


    Encephalitis is usually caused by a virus, such as the herpes simplex virus types 1 and 2, or arboviruses, in the United States. Arboviruses are spread from animals to humans and causes mosquito-borne disease. An example is the West Nile virus.

    Symptoms may start out as mild flu-like symptoms and headaches, quickly followed by behavioral changes, hallucinations, and confusion.   

    Are Meningitis and Encephalitis Contagious?

    Some forms of bacterial meningitis and encephalitis are contagious and can be spread through contact. For example, meningococcal meningitis is easily spread among people who live together such as college students in a dormitory. If you have recently been in contact with someone who has been diagnosed with bacterial meningitis or encephalitis, talk with your doctor to find out if you need prophylactic antibiotics, which can help prevent a bacterial infection


    The spinal cord is responsible for carrying sensory information back to the brain and motor messages from the brain to the body. When it is inflamed like in the case of myelitis , symptoms can include pain, weakness in the limbs, bowel and bladder problems, and sensory problems. Many people with myelitis also experience muscle spasms , headache, fever, and loss of appetite.  

    Myelitis may be related to an immune disorder or infection from a virus, bacterium, fungus, or parasite. Most people who experience myelitis make a full recovery, but the process can take months to years. There is no cure for myelitis, but the symptoms can be treated.  


    A brain abscess occurs when a collection of pus becomes enclosed in brain tissue. This rare condition can be caused by a bacterial or fungal infection, and is also a possible complication of surgery or trauma. People with compromised immune systems are more at risk of having a brain abscess.  

    Symptoms include a high fever, severe headache, behavior changes, and nausea and vomiting. Over time, an abscess can cause changes in speech, motor weakness, spasticity, and seizures . Once it is discovered, an abscess must be located and surgically drained, followed by four to eight weeks of antibiotic therapy.  


    There are several types of causes of brain infections, and each one has its own transmission route. Viruses may be spread through close contact or respiratory secretions, such as sharing drinking glasses or kissing. Bacterial infections can also be spread through close contact or contaminated food preparation. 

    Here's a breakdown of all possible causes of brain infections:

    • Virus: While rare, several viruses can lead to an infection of the brain, spinal cord, or surrounding area. Possible causes include the herpes simplex virus, varicella zoster virus , cytomegalovirus , Epstein-Barr virus , and influenza viruses. Mosquito-borne illnesses like West Nile and Zika may also lead to a brain infection.
    • Bacteria: The bacteria most likely to lead to a bacterial brain infection in the United States include Streptococcus pneumoniae, group B Streptococcus, Neisseria meningitidis, Haemophilus influenzae ,and Listeria monocytogenes.
    • Fungus: A fungal infection that spreads to the brain may be caused by the Aspergillus, Blastomyces, Coccidioides, or Cryptococcus fungus.
    • Parasite: A parasitic infection in the brain may be caused by toxoplasmosis , cysticercosis, schistosomiasis, or strongyloides. 
    • Immune system disorders: If you have a compromised immune system for any reason, you may be more at risk of experiencing a brain infection. People with an HIV infection are more at risk of rare infections such as a brain abscess. Multiple sclerosis may also lead to myelitis. 


    The symptoms of a brain infection will depend on the area of the brain that has been infected, as well as the severity of the infection

    The symptoms for each type of brain infection is as follows:

    • Meningitis: Sudden fever, severe headache, stiff neck, photophobia, and nausea and vomiting
    • Encephalitis: Headache, behavioral changes, hallucinations, altered level of consciousness
    • Myelitis: Weakness of the arms and legs, shooting pain, numbness and tingling, bowel and bladder dysfunction
    • Abscess: High fever, severe headache, behavior changes, and nausea and vomiting


    The diagnostic tool used to diagnose your brain infection will depend on your symptoms and physical exam findings. Any symptoms of a brain infection should be evaluated by a physician right away. If you are concerned about a brain infection, your doctor will perform a neurological exam to evaluate your motor and sensory function. 

    After taking a thorough history and performing a physical exam, your physician may recommend the following tests: 

    • Imaging studies: Imaging studies are used to detect inflammation or lesions in the brain or spinal cord. A brain MRI can detect an abscess or lesion, as well as an underlying condition that could be causing the symptoms, such as multiple sclerosis. A brain CT scan may be used to detect inflammation. 
    • Blood cultures: If a bacterial infection is suspected, blood cultures will be drawn to determine the specific type of bacteria causing the infection. This information will then be used to select the most effective antibiotic medication. 
    • Lumbar puncture: A lumbar puncture, also called a spinal tap , involves inserting a needle in between the vertebrae in the lower back to remove cerebrospinal fluid , which flows through the brain and spinal cord. This fluid may be tested for bacteria, proteins, or increased white blood cells. 

    When a Lumbar Puncture Can't Be Used

    A lumbar puncture may be used for diagnosis but cannot be performed if there is too much brain swelling because it could worsen the pressure in the brain and cause complications like brain herniation. Symptoms of increased intracranial pressure to watch out for include a headache, blurred vision, vomiting, behavioral changes, muscle weakness, and extreme drowsiness.  


    Treatment for a brain infection depends on which type of infection you have. However, early treatment is essential for minimizing complications and dangerous symptoms, so never hesitate to see your doctor if you are concerned. 

    Therapies used to treat a brain infection can include the following:

    • Antibiotics are started right away if a bacterial infection is suspected. If you are being evaluated for meningitis, your medical team will most likely start IV antibiotics while waiting for test results. 
    • Corticosteroids are usually prescribed to help lower inflammation in the brain or spinal cord. Most brain infections involve some degree of inflammation, which can put pressure on the brain and spinal cord and lead to serious complications. A corticosteroid may help reduce swelling and immune system activity.
    • Antiviral medications are prescribed when the medical team suspects that your brain infection is caused by a virus. If you present with symptoms of encephalitis, an antiviral drug is usually prescribed right away.


    The prognosis for a brain infection depends on the severity of your condition, what caused the infection, and how fast treatment was initiated. Most people who experience a brain infection make a full recovery.

    The following treatments may be needed for long-term recovery:

    • Physical therapy
    • Occupational therapy
    • Psychotherapy 

    Recovery from an infection of the brain will vary depending on the degree of brain inflammation. Inflammation of the brain can lead to coma and death. Earlier symptoms include severe fatigue, muscle weakness, behavioral changes, memory problems, changes in speech, hearing loss, vision loss, and paralysis. Seek treatment right away if you believe you have a brain infection


    A brain infection cannot always be prevented, but one effective step to take is to get vaccinated. Many causes of bacterial brain infections are now preventable with the following vaccines:

    • Meningococcal vaccines help protect against N. meningitidis
    • Pneumococcal vaccines help protect against S. pneumoniae
    • Hib vaccines help protect against Hib

    To prevent viral and bacterial infections that can spread to the brain, take regular safety precautions like washing your hands and avoiding contact with individuals who are ill. To protect yourself against mosquito- or tick-borne illnesses that could lead to a brain infection, use insect repellent when spending time outdoors and opt for long sleeves and pants. Aim to limit your outdoor activities at night when mosquitoes are more active and address any standing water around your home.


    If you have symptoms of a brain infection, talk to your doctor or get emergency medical help immediately. Left untreated, a brain infection can cause serious complications.

    A Word From Verywell

    A brain infection is a serious condition that can quickly become life-threatening if left untreated. Learning what signs to look out for can help you prepare and get help right away if you do become infected. Be on the lookout, especially if you have a condition that places you at higher risk of a brain infection. If you or a loved one believe you are experiencing the symptoms of a brain infection, see your doctor or seek emergency medical help right away. Early treatment is crucial, and remember that most people who are treated right away make a full recovery.

    What infection causes brain swelling?
    Overview. Encephalitis (en-sef-uh-LIE-tis) is inflammation of the brain. There are several causes, including viral infection, autoimmune inflammation, bacterial infection, insect bites and others. Sometimes there is no known cause. more
    Is brain surgery a traumatic brain injury?
    Surgical brain injury (SBI) comprises a form of injury that inadvertently results from damaged brain tissue at the perisurgical site due to neurosurgical maneuvers such as incision, retraction, and electrocauterization, all of which are essential surgical techniques. more
    Does Covid infect the brain?
    Writing in Nature, researchers at Oxford University's Wellcome Centre for Integrative Neuroimaging reported that several months after study participants had SARS-CoV-2 infections, they had more gray matter loss and tissue abnormalities, mainly in the areas of the brain associated with smell, and more brain size more
    Why does brain swell in DKA?
    Abstract. Cerebral edema is the leading cause of death in children presenting in diabetic ketoacidosis and occurs in 0.2 to 1% of cases. The osmolar gradient caused by the high blood glucose results in water shift from the intracelluar fluid (ICF) to the extracellular fluid (ECF) space and contraction of cell volume. more
    Why does the brain swell with DKA?
    The causes of DKA-related cerebral edema are not well understood. Initially, many investigators hypothesized that DKA-related cerebral edema is caused by rapid declines in serum osmolality due to rapid infusion of hypotonic intravenous fluids. more
    What is the difference between a traumatic brain injury and an acquired brain injury?
    An acquired brain injury is the umbrella term for all brain injuries. There are two types of acquired brain injury: traumatic and non-traumatic. A traumatic brain injury (TBI) is defined as an alteration in brain function, or other evidence of brain pathology, caused by an external force. more
    Can a brain scan show brain damage?
    These newer, specialized types of MRI scans can now look and assess damage to the brains structure, or measure brain function to detect changes in the brains structure and function due to TBI and concussions. more
    Is it better to be right brain or left-brain?
    Left-handed people have right brain dominance for body control, which may also result in the more artistic personality for which such people are known. However, as can be seen by the fact that there are numerous right-handed artists as well as left-handed rational thinkers, brain lateralization only goes so far. more
    Does sleep clear brain?
    During deep sleep, waves of cerebrospinal fluid (blue) coincide with temporary decreases in blood flow (red). Less blood in the brain means more room for the fluid to carry away toxins, including those associated with Alzheimer's disease. more
    How is an ADHD brain different from a normal brain?
    ADHD brains have low levels of a neurotransmitter called norepinephrine. Norepinephrine is linked arm-in-arm with dopamine. Dopamine is the thing that helps control the brain's reward and pleasure center. The ADHD brain has impaired activity in four functional regions of the brain. more
    Do dogs have right brain or left brain?
    Individuals—canine or human—who favor the left paw or hand more often use the right hemisphere of their brain, while right-pawed and right-handed individuals have a more active left-brain hemisphere. Studies have shown differences between right-pawed and left-pawed dogs. more

    Source: www.verywellhealth.com

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