Brain Abscess

What is Brain Abscess?

A brain abscess is a specific area of the brain, which has died off and is surrounded by a special covering. This usually happens due to an infection or less commonly, from injuries or surgeries. The abscess may arise from nearby areas like the ear, teeth, sinuses, behind the ear, or outside the protective layer of the brain. Surprisingly, abscesses can also form from faraway areas such as the lungs, heart, or kidneys. Frequently in young children, brain abscesses can be linked to a condition they were born with that affects their heart. While anyone can have a brain abscess, people in their thirties seem to face this issue more often.

What Causes Brain Abscess?

Brain abscesses are pockets of infection that develop in the brain and can start locally and spread to other parts of the body. They may develop from infections near the brain, like in the ears or sinuses. Sometimes, these infections can reach even to distant areas like the heart or lungs.

Infections in the head and neck can lead to a brain abscess. These can include ear infections, mastoiditis (an infection in the bony air cells behind the ear), and sinus infections. Sinus infections contribute to 30-50% of brain abscess cases. Depending on the location of the infection, different parts of the brain like the frontal lobes could be affected. Regular dental infections can also lead to brain abscesses.

Injuries to the face or head, including those from surgical procedures affecting the brain, can lead to a brain abscess. Sometimes, if metal fragments or other foreign substances are left in the brain, they can cause an infection.

Conditions that spread infection throughout the body can also cause brain abscesses. Common sources include the lungs, with conditions such as lung abscesses or the progressive lung disease bronchiectasis. Cystic fibrosis, a chronic disease that affects the lungs, can be a significant contributor to brain abscesses.

Other factors can include pneumonia, certain heart defects in children, bacterial growth in the heart, blood clots, and infections in the skin, pelvis, or abdomen. Approximately 10% of patients with lung blood vessel problems (pulmonary arteriovenous malformations) develop brain abscesses.

The most common types of bacteria found in brain abscesses are Staphylococcus and Streptococcus. Particularly, Staphylococcus aureus and Viridian streptococci are the most frequently found species. Other common bacteria found include Streptococcus pneumoniae, Staphylococcus epidermidis, Enterococcus, and various other bacteria. These abscesses can also sometimes contain fungi and parasites.

Risk Factors and Frequency for Brain Abscess

Brain abscesses, which are a type of lump in the brain, make up about 8% of such lumps in developing countries and 1-2% in Western countries. In other words, around 4 out of every million people will get a brain abscess. People with AIDS have a higher chance of getting a brain abscess.

Each year in the US, there are about 1500 to 2500 cases of brain abscesses.
The number of brain abscesses caused by fungi has gone up because more people are using strong antibiotics and drugs that affect the immune system, like steroids.
The people most likely to get brain abscesses are adult men under 30, children aged 4 to 7, and newborns.
Vaccines have helped lower the number of brain abscesses in young children.
Men are more likely than women to get brain abscesses, with about 2 to 3 men getting them for every woman who does.
Where you live or what time of year it is doesn’t really affect your chances of getting a brain abscess.
In developing countries where people don’t live as well, brain abscesses take up a larger share of the lumps in the brain compared to developed countries.

Signs and Symptoms of Brain Abscess

Brain abscesses, which are infections in the brain, typically show symptoms within two weeks of onset. However, the vague nature of these symptoms often leads to delays in diagnosis, in some instances reaching up to approximately eight days after the first symptoms appear. The severity of the condition and its symptoms can range from mild to severe.

The symptoms generally vary depending on the size and location of the affected area in the brain. In fact, the combination of fever, headache, and focal neurological impairment is seen in less than half of the patients. Typical signs and symptoms vary in frequency as follows:

Headache (in 69%-70% of patients) is the most common symptom and it might become gradually severe or start suddenly
Mental status changes (seen in 65% of patients) can range from lethargy to coma, hinting at severe brain swelling, which is a sign of poor prognosis
Focal neurologic deficits (seen in 50%-65% of patients) may appear days to weeks after the onset of a headache
Pain, often on the side of the abscess, is usually severe and doesn’t respond to common pain relievers
Fever (seen in 45%-53% of patients)
Seizures (seen in 25%-35% of patients) could be the first sign of a brain abscess, with grand mal seizures being common with frontal abscesses
Nausea and vomiting (seen in 40% of patients) are usually linked to an abscess in the back part of the brain or an abscess that has leaked into a lateral ventricle, which is a cavity in the brain
Nuchal rigidity (seen in 15% of patients) or neck stiffness is commmon with an occipital lobe abscess or an abscess that has leaked into a lateral ventricle
Deficits in the third and sixth cranial nerve functions

If the abscess ruptures, it usually causes a sudden, severe headache, followed by signs of inflammation of the membranes covering the brain and spinal cord.

Testing for Brain Abscess

If your doctor suspects that you have a brain abscess, they will need to carry out a number of tests to confirm the diagnosis:

Routine tests: These include a complete blood count to check the number and types of cells in your blood, an erythrocyte sedimentation rate (a test that measures how fast your red blood cells settle in a test tube), a serum C-reactive protein test (a measure of inflammation), and blood cultures to check for the presence of bacteria. Usually, two blood cultures are taken before starting on antibiotics.

Lumbar puncture: This is a procedure in which a needle is inserted into your back to collect a sample of cerebrospinal fluid (CSF), the fluid that surrounds the brain and spinal cord. However, this test is not usually required unless there is a specific reason for doing it, such as if there’s suspicion of meningitis, and it should only be conducted after a CT or MRI scan. In cases of rupture, when the white blood cell count (WBC) becomes high, additional findings may include elevated CSF lactic acid and many red blood cells (RBCs) in the CSF.

Stereotactic Computed Tomography or Surgical Aspiration: These give us a sample of the abscess content, making it possible to identify the type of bacteria causing the infection, the best type of antibiotics to use, and how the treatment is progressing.

Computed Tomography: Also known as a CT scan, this is an imaging test that uses x-rays to create detailed pictures of the brain. It’s not as detailed as MRI, but is often used in emergencies. The image changes as the infection evolves.

Magnetic Resonance Imaging: Also known as MRI, this is a type of imaging test that uses magnetic fields and radio waves to create images of the brain. It’s the preferred method for diagnosing and monitoring brain abscesses because it provides more detail than a CT scan, especially in the early stages of the infection.

Brain Biopsy: This involves taking a small sample of the abscess for laboratory analysis. This helps to confirm the diagnosis and to identify the specific fungus or parasite that might be causing the abscess. However, this procedure may not be necessary or may need to be delayed in some cases, such as if you are responding well to antibiotics, if the abscess is in a part of the brain that is difficult to reach, or if the abscess is small and you are otherwise well.

Treatment Options for Brain Abscess

A brain abscess is a serious condition that can cause pressure in the skull and carries significant risks, including death. Brain abscesses are typically treated using either medication, surgery, or a combination of both.

Medication can be an effective treatment for small abscesses (less than 2 cm across) located deep within the brain or in cases where there is concurrent meningitis. In such situations, the treatment may also involve surgery.

Imagining of the brain using CT and MRI scans is key to effective treatment. These scans can locate the abscess, show how big it is and reveal how many abscesses there are. Large abscesses (more than 2 cm in size) are usually drained or removed by a skilled surgeon. When multiple abscesses are present, the treatment typically involves a long-term course (4-8 weeks) of high-dose antibiotics. The treatment’s progress may be monitored using weekly CT scans.

The choice of antibiotic depends on the type of microorganisms (bacteria, fungi, etc.) detected in blood or cerebral fluid tests. Some antibiotics, such as first-generation cephalosporins, aminoglycosides, and tetracyclines, are not effective in treating brain abscesses as they can’t cross the blood-brain barrier – the protective barrier that prevents harmful substances in the blood from reaching the brain.

For example, certain types of bacteria are generally treated with third-generation cephalosporins (like cefotaxime, ceftriaxone) or penicillin G. Infections resulting from the bacteria known as S. aureus and S. epidermis, usually linked to brain trauma or neurosurgery are typically treated with vancomycin. Additionally, fungal infections are treated with a medication called amphotericin B. Infections caused by the parasite ‘Toxoplasma gondii’ are typically treated with pyrimethamine, sulfadiazine, and in cases of HIV, highly active antiretroviral therapy.

In some special situations, steroids can be considered as part of the treatment. Steroids can help to reduce the mass effect, improve how well antibiotics work, and decrease brain swelling. However, due to the risk of exacerbating an underlying infection or slowing down wound healing, their use needs to be carefully considered.

Surgery is very important for managing brain abscesses and the choice of surgical procedure depends on the surgeon’s skill and preference. Procedures can range from needle aspirations guided by ultrasound or CT scans, burr hole, or craniotomy for abscesses with multiple compartments. Surgery is often combined with medication targeting specific microorganisms.

When trying to diagnose a certain condition, doctors also need to consider other potential diseases or disorders that might be causing similar symptoms. These possibilities can include:

Bacterial meningitis
Brain tumors
Demyelination (breakdown of the protective layer around nerve fibers)
Abscess (a pocket of infection) in the epidural or subdural region (around the brain or spinal cord)
Encephalitis (inflammation of the brain)
Infestations by fungi or parasites, such as cryptococcosis and cysticercosis
Mycotic aneurysm (a bulge in a blood vessel caused by a fungal infection)
Septic dural sinus thrombosis (a blood clot forming in a vein in the brain due to infection)

What to expect with Brain Abscess

Thanks to the development of antibiotics and advanced imaging techniques like CT scans and MRI, the death rate from brain abscesses has dropped from 10% to 5%. However, if the brain abscess ruptures, it can still be a deadly complication. The long-term effects on the nervous system after an infection largely depend on early detection and prompt treatment with antibiotics. Therefore, prompt medical attention is crucial to manage this condition effectively.

Possible Complications When Diagnosed with Brain Abscess

Potential complications following a brain abscess can include:

Meningitis, which is an inflammation of the membranes covering the brain and spinal cord
Ventriculitis, an infection of the brain’s ventricles or cavities
Increased pressure inside the skull
Brain herniation, which is a potentially fatal side effect where brain tissue, cerebrospinal fluid, and blood vessels are moved away from their usual position in the brain
Seizures, or periods of abnormal electrical activity in the brain
Septicemia, also known as blood poisoning
Neurological deficits, such as difficulty moving, speaking, or thinking
Thrombosis of intracranial blood vessels, or blood clots in the vessels inside the skull
Death

Preventing Brain Abscess

It’s important that the patient understands the need to finish all prescribed antibiotics. If needed, they may also have to take medication to prevent seizures, which are called anticonvulsants. If the patient starts to have a new fever or signs of increased pressure inside the skull, they should go to the hospital as soon as possible.

Frequently asked questions

A brain abscess is a specific area of the brain that has died off and is surrounded by a special covering. It is usually caused by an infection or, less commonly, by injuries or surgeries.

Brain abscesses make up about 8% of lumps in the brain in developing countries and 1-2% in Western countries.

The signs and symptoms of Brain Abscess include: - Headache: It is the most common symptom, present in 69%-70% of patients. The headache can start suddenly or gradually become severe. - Mental status changes: Seen in 65% of patients, these changes can range from lethargy to coma, indicating severe brain swelling and a poor prognosis. - Focal neurologic deficits: Present in 50%-65% of patients, these deficits may appear days to weeks after the onset of a headache. - Pain: Often severe and located on the side of the abscess, the pain does not respond to common pain relievers. - Fever: Seen in 45%-53% of patients. - Seizures: Present in 25%-35% of patients, seizures can be the first sign of a brain abscess. Grand mal seizures are common with frontal abscesses. - Nausea and vomiting: Linked to an abscess in the back part of the brain or an abscess that has leaked into a lateral ventricle. - Nuchal rigidity: Neck stiffness is common with an occipital lobe abscess or an abscess that has leaked into a lateral ventricle. - Deficits in the third and sixth cranial nerve functions. - If the abscess ruptures, it can cause a sudden, severe headache, followed by signs of inflammation of the membranes covering the brain and spinal cord.

Brain abscesses can develop from infections near the brain, such as in the ears or sinuses. They can also be caused by injuries to the face or head, including surgical procedures affecting the brain. Conditions that spread infection throughout the body, such as lung abscesses or bronchiectasis, can also lead to brain abscesses. In addition, certain factors like pneumonia, heart defects, bacterial growth in the heart, blood clots, and infections in the skin, pelvis, or abdomen can contribute to the development of brain abscesses.

Bacterial meningitis, brain tumors, demyelination, abscess in the epidural or subdural region, encephalitis, infestations by fungi or parasites, mycotic aneurysm, septic dural sinus thrombosis.

The types of tests needed for diagnosing a brain abscess include: 1. Routine blood tests: Complete blood count, erythrocyte sedimentation rate, serum C-reactive protein test, and blood cultures. 2. Lumbar puncture: This is done to collect a sample of cerebrospinal fluid (CSF) for analysis. 3. Stereotactic Computed Tomography or Surgical Aspiration: This procedure provides a sample of the abscess content for identification of the bacteria causing the infection and determining the appropriate antibiotics. 4. Computed Tomography (CT) scan: This imaging test uses x-rays to create detailed pictures of the brain. 5. Magnetic Resonance Imaging (MRI): This imaging test uses magnetic fields and radio waves to create detailed images of the brain. 6. Brain Biopsy: In some cases, a small sample of the abscess may be taken for laboratory analysis to confirm the diagnosis and identify the specific fungus or parasite causing the abscess.

Brain abscesses are typically treated using medication, surgery, or a combination of both. Medication can be effective for small abscesses located deep within the brain or in cases where there is concurrent meningitis. Surgery is important for managing brain abscesses, and the choice of surgical procedure depends on the surgeon's skill and preference. Procedures can range from needle aspirations guided by ultrasound or CT scans, burr hole, or craniotomy for abscesses with multiple compartments. The choice of antibiotic for medication treatment depends on the type of microorganisms detected in blood or cerebral fluid tests.

The potential side effects when treating a brain abscess include: - Meningitis, which is an inflammation of the membranes covering the brain and spinal cord - Ventriculitis, an infection of the brain's ventricles or cavities - Increased pressure inside the skull - Brain herniation, where brain tissue, cerebrospinal fluid, and blood vessels are moved away from their usual position in the brain - Seizures, or periods of abnormal electrical activity in the brain - Septicemia, also known as blood poisoning - Neurological deficits, such as difficulty moving, speaking, or thinking - Thrombosis of intracranial blood vessels, or blood clots in the vessels inside the skull - Death

The prognosis for brain abscess has improved due to the development of antibiotics and advanced imaging techniques. The death rate has dropped from 10% to 5%. However, if the abscess ruptures, it can still be a deadly complication. Prompt medical attention is crucial for effective management and the long-term effects on the nervous system largely depend on early detection and prompt treatment with antibiotics.

A neurologist or a neurosurgeon.