Brain Infection Symptoms and Treatment

A brain infection can be caused by a virus, bacteria, fungus, or parasite. The infection can involve other parts of the central nervous system (CNS), including the spinal cord.

There are several types of infections, each of which affects different parts of the CNS. These include:

• Encephalitis: Inflammation of the brain
• Meningitis: Inflammation of the lining of the brain and spinal cord (called the meninges)
• Traverse myelitis: Inflammation of part of the spinal cord
• Cerebral abscess: A pocket of pus inside the brain

Most people recover from brain infections. But in some cases,  the infections can be serious and even life-threatening.

This article explores four common types of brain infections, including their causes and symptoms. It also explains how brain infections are diagnosed, treated, and prevented.

Types of Brain Infections

The different types of brain infections vary by their cause and location. Some, like encephalitis, involve the entire brain, while others are localized to one part of the brain, such as an abscess. Each requires immediate treatment to avoid potentially severe nerve injury.

Encephalitis

Encephalitis is usually caused by a virus. In the United States, these include viruses that cause herpes and shingles. Autoimmune encephalitis is a less common form in which the body's immune system inappropriately attacks cells in the brain.

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

Meningitis

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 associated with upper respiratory tract infections can become invasive and 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 (sensitivity to light), and nausea and vomiting. Being unable to bend your chin to your chest is also a sign of meningitis.

While the symptoms may initially resemble those of a cold or upper respiratory infection, they can quickly become more severe. 

Traverse Myelitis

Traverse myelitis is inflammation of part of the spinal cord, namely the protective coating on nerves called the myelin sheath. Inflammation of spinal myelin can affect multiple body functions, causing pain, muscle spasms, headache, fever, loss of appetite, limb weakness, and the loss of bowel and bladder control. 

Traverse myelitis may also be due to an autoimmune disorder or a viral, bacterial, fungal, or parasitic infection. Most people experience a full recovery, but the process can take months to years. There is no cure for traverse myelitis, but the symptoms can be treated. 

Cerebral Abscess

A cerebral abscess, also known as a brain abscess, is a pocket of pus in the brain. This rare condition can be caused by a bacterial or fungal infection. It is also a possible complication of surgery or brain trauma. People with compromised immune systems are at greatest risk. 

Symptoms include a high fever, severe headache, behavior changes, and nausea and vomiting. Over time, an abscess can cause difficulty speaking, motor weakness, spasticity, and seizures. An abscess requires surgical drainage, followed by four to eight weeks of antibiotic drugs. 

Causes of Brain Infections

The pathogenesis (disease pathway) of a brain infection can differ based on the cause. Viruses may be spread through respiratory secretions, while bacterial infections can be passed through close contact or contaminated foods. 

Other infections occur only in special situations. Fungal brain infections, for example, typically involve people with severely weakened immune systems who lack the defenses other people have.

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

• Virus: While rare, several viruses can lead to an infection of the brain or CNS, including the herpes simplex viruses, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, and influenza viruses. Mosquito-borne illnesses like West Nile fever and Zika may also lead to a brain infection.
• Bacteria: The bacteria most likely to lead to a brain infection in the United States are Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenza, and Listeria monocytogenes.
• Fungus: A fungal infection that spreads to the brain may be caused by the Aspergillus, Blastomyces, Coccidioides, or Cryptococcus fungi.
• 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, you are at greater risk because an infection can more readily disseminate (spread throughout the body). People with advanced HIV are vulnerable to invasive fungal infections. Multiple sclerosis can also lead to traverse myelitis.

Symptoms of Brain Infections

Inflammation, the body's natural response to infection, can trigger both physical and neurological symptoms due to the swelling of the brain or spinal cord. Abscesses pose harm by placing pressure on the functional tissues of the brain, called the parenchyma.

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 vary as follows:

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

Possible Complications of Brain Infection

A brain infection can cause lasting and even permanent damage if the infection is severe or left untreated. Despite improvements in diagnosis and treatment, the risk of death from infections like meningococcal meningitis remains inordinately high, hovering around 10%.

Those who survive severe events may be left with permanent disabilities, including:

• Chronic fatigue
• Hearing loss
• Impaired concentration
• Memory loss
• Personality changes
• Clinical depression
• Aphasia (speech and language problems)
• Dysphagia (difficulty swallowing)
• Loss of balance or coordination
  
• Seizures
• Blindness

How Brain Infections Are Diagnosed

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 healthcare provider 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 healthcare provider 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. 

How Brain Infections Are Treated

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 healthcare provider 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 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 immediately.

Prognosis

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. In some cases, inflammation of the brain can lead to coma and death.

Survival and Mortality

The risk of death (mortality) can vary by both the location of the infection, the type of infection, and other factors:

• Encephalitis: Between 5% of 20% of people hospitalized for encephalitis die in the hospital irrespective of the infection type.
• Meningitis: Streptococcus pneumonia, the most frequent cause of bacterial meningitis, is associated with a 17% risk of mortality among hospitalized people.
• Traverse myelitis: Studies vary, but some suggest that the median survival time from the time of diagnosis is 8.9 years, with some people living up to 16 years. Older age and tobacco use contribute to shorter survival times.
• Cerebral abscess: Studies vary, but most suggest that the in-hospital death rate among people with a brain abscess hovers at around 16%. Cases commonly involve Streptococcus bacteria.
  

Prevention

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 Haemophilus influenzae type b (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. Limit your outdoor activities at night when mosquitoes are more active and address any standing water around your home.

Summary

A brain infection is a serious condition that can become life-threatening if left untreated. Examples include encephalitis, meningitis, traverse myelitis, and cerebral abscesses. Complications of untreated brain infections include memory loss, hearing loss, vision problems, seizures, personality changes, loss of bladder or bowel control, and death.

Blood tests, imaging studies, and a spinal tap may be needed to diagnose the cause. Treatment may involve a course of antimicrobial drugs delivered by mouth, injection, or intravenous infusion. Abscesses may require surgery to drain pus from the brain.