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INTRODUCTION-
An abscess in the brain of an otherwise healthy person is usually caused by bacterial infection. Fungal brain abscesses tend to occur in people with weakened immune systems. The infection will cause your brain to swell from the collection of pus and dead cells that forms.
A brain abscess forms when fungi, viruses, or bacteria reach your brain through a wound in your head or an infection somewhere else in your body. According to the Children’s Hospital of Wisconsin, infections from other parts of the body account for between 20 and 50 percent of all brain abscess cases. Heart and lung infections are among the most common causes of brain abscesses. However, brain abscesses can also begin from an ear or sinus infection, or even an abscessed tooth.
See your doctor right away if you think you may have a brain abscess. You’ll need the appropriate treatment to prevent any brain damage from the swelling.
Intracranial abscesses are uncommon, serious, life-threatening infections. They include brain abscess and subdural or extradural empyema and are classified according to the anatomical location or the etiologic agent. The term brain abscess is used in this article to represent all types of intracranial abscesses.
Intracranial abscesses can originate from infection of contiguous structures (eg, otitis media, dental infection, mastoiditis, sinusitis) secondary to hematogenous spread from a remote site (especially in patients with cyanotic congenital heart disease), after skull trauma or surgery, and, rarely, following meningitis. In at least 15% of cases, no source can be identified.
A brain abscess is a collection of pus that develops in response to an infection or trauma. It remains a serious and potentially life-threatening condition.
In the past, a brain abscess was “invariably fatal,” but researchers writing in 2014 noted that progress in diagnosis and treatment have significantly increased the chances of survival.
The effects vary, depending on the size of the abscess and where it forms in the brain.
Between 1,500 and 2,500 cases occur each year in the United States. Brain abscesses are most likely to affect adult men aged under 30 years. Among children, they most commonly develop in those aged 4–7 years. Newborns are also at risk.
Vaccination programs have reduced the incidence of brain abscesses in young children.
CAUSES-
A brain abscess is most likely to result from a bacterial or fungal infection in some part of the brain. Parasites can also cause an abscess.
When the bacteria, fungi, or parasites infect part of the brain, inflammation and swelling occur. In these cases, the abscess will consist of infected brain cells, active and dead white blood cells, and the organisms that cause the problem.
As the cells accumulate, a wall or membrane develops around the abscess. This helps to isolate the infection and keep it from spreading to healthy tissue.
If an abscess swells, it puts increasing pressure on surrounding brain tissue.
The skull is not flexible, and it cannot expand. The pressure from the abscess can block blood vessels, preventing oxygen from reaching the brain, and this results in damage or destruction of delicate brain tissue.
here are 3 main ways a brain abscess can develop. These are:
- an infection in another part of the skull – such as an ear infection, sinusitis or dental abscess, which can spread directly into the brain
- an infection in another part of the body – for example, the infection that causes pneumonia spreading into the brain via the blood
- trauma, such as a severe head injury – that cracks open the skull, allowing bacteria or fungi to enter the brain
However, in some cases, the source of the infection remains unknown.
SYMPTOM-
Symptoms usually develop slowly over several weeks, but they can also come on suddenly. Symptoms you should watch for are:
- differences in mental processes, such as increased confusion, decreased responsiveness, and irritability
- decreased speech
- decreased sensation
- decreased movement due to loss of muscle function
- changes in vision
- changes in personality or behavior
- vomiting
- fever
- chills
- neck stiffness, especially when it occurs with fevers and chills
- sensitivity to light
In babies and young children, most of the symptoms are similar. However, your child may show other symptoms of a brain abscess. The soft spot on top of your baby’s head, called the fontanelle, may be swollen or bulging. Other symptoms in your child can include:
- projectile vomiting
- high-pitched crying
- spasticity in the limbs
The signs and symptoms of a brain abscess are as follows:
- a headache (69–70 percent of cases)
- a fever (45–53 percent)
- seizures (25–35 percent)
- nausea and vomiting (40 percent)
A seizure may be the first sign of an abscess. Nausea and vomiting tend to occur as pressure builds inside the brain.
Pain usually starts on the side of the abscess, and it may begin slowly or suddenly.
Changes in mental status occur in 65 percent of cases, and they may lead to:
- confusion
- drowsiness and lethargy
- irritability
- poor mental focus
- poor responsiveness
- slow thought processes
- coma (possibly)
Neurologic difficulties affect 50–65 percent of people with brain abscesses. These issues often follow a headache, appearing within days or weeks, and they can include:
- muscle weakness
- weakness or paralysis on one side of the body
- speech problems, such as slurred speech
- poor coordination
Other symptoms may include:
- a stiff neck, back, or shoulders
- blurred, double, or graying vision
The symptoms of a brain abscess result from a combination of infection, brain tissue damage, and pressure on the brain, as the abscess grows to take up more space.
If the headache suddenly becomes worse, it may mean that the abscess has burst.
In two-thirds of cases, symptoms are present for as long as 2 weeks. On average, doctors diagnose the issue 8 days after symptoms start.
When to get medical advice
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Any symptoms that suggest a problem with the brain and nervous system should be treated as a medical emergency. These include:
- slurred speech
- muscle weakness or paralysis
- seizures occurring in a person with no previous history of seizures
If you or someone you know experiences any of these symptoms, phone 999 immediately and ask for an ambulance.
Any symptoms that suggest a worsening infection, such as a high temperature or being sick, should be reported to your GP immediately.
DIAGNOSIS-
Many of these symptoms closely resemble other diseases or health problems. Talk to your doctor immediately if you develop any of the symptoms. You’ll likely need a neurological exam. This exam can reveal any increased pressure within the brain, which can occur from swelling. CT and MRI scans can also be used to diagnose a brain abscess.
In some cases, your doctor may need to perform a lumbar puncture, or spinal tap. This involves the removal of a small amount of cerebral spinal fluid to test for any problems other than an infection. A lumbar puncture will not be performed if any significant brain swelling is suspected, as it can temporarily worsen the pressure inside the head. This is to avoid the risk of brain hematoma, or a ruptured blood vessel in the brain.
To diagnose a brain abscess, the doctor will evaluate signs and symptoms and look at the patient’s recent medical and travel histories.
They will need to know whether the individual:
- has had an infection recently
- has a weakened immune system
Symptoms can be similar to those of other illnesses and conditions, so it may take time to confirm a diagnosis. The diagnosis will be more straightforward if the doctor can pinpoint exactly when symptoms started and how they progressed.
Tests may include:
- a blood test to check for high levels of white blood cells, which can indicate an infection
- imaging scans, such as an MRI or a CT scan, in which an abscess will show up as one or more spots
- a CT-guided aspiration, a type of needle biopsy, which involves taking a sample of pus for analysis
The number of fatalities from brain abscesses has fallen in recent decades, due to the increasingly routine use of CT and MRI scans in detection.
How infection enters the brain
Brain infections are fairly uncommon for several reasons.
One reason involves the blood-brain barrier, a protective network of blood vessels and cells. It blocks certain components from the blood that flows to the brain, but it allows others to pass through.
Sometimes, an infection can get through the blood-brain barrier. This can happen when inflammation damages the barrier, leading to gaps.
The infection enters the brain through three main routes.
It may:
- come through the blood from an infection in another part of the body
- spread from a nearby site, such as the ear
- result from a traumatic injury or surgery
Infection from another area of the body
If an infection occurs somewhere else in the body, the infectious organisms can travel through the bloodstream, bypass the blood-brain barrier, and enter and infect the brain.
Between 9 and 43 percent of abscesses result from pathogens that traveled from another part of the body.
Many bacterial brain abscesses stem from a lesion somewhere else in the body. It is crucial to find that primary lesion, or there may be a repeat infection in the future.
A person with a weakened immune system has a higher risk of developing a brain abscess from a bloodborne infection.
A person may have a weakened immune system if they:
- have HIV
- have AIDS
- are infants under the age of 6 months
- are receiving chemotherapy
- are using long-term steroid medication
- have had an organ transplant and take immunosuppressant drugs to prevent organ rejection
The most common infections known to cause brain abscesses are:
- endocarditis, an infection of the heart valve
- pneumonia, bronchiectasis, and other lung infections and conditions
- abdominal infections, such as peritonitis, an inflammation of the inner wall of the abdomen and pelvis
- cystitis, or inflammation of the bladder, and other pelvic infections
Direct contagion-
An infection can spread from a nearby area, and this accounts for 14–58 percent of brain abscesses.
If an infection starts inside the skull, for example in the nose or the ear, it can spread to the brain.
Infections that can trigger a brain abscess include:
- otitis media, or a middle ear infection
- sinusitis
- mastoiditis, an infection of the bone behind the ear
The location of the abscess may depend on the site and type of the original infection.
Direct trauma
A brain abscess can result from trauma, such as from neurological surgery or a penetrating brain injury.
An abscess can result from:
- a blow to the head that causes a compound skull fracture, in which fragments of bone are pushed into the brain
- the presence of a foreign body, such as a bullet, if someone does not remove it
- a complication of surgery, in rare cases
What are the risk factors?
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Nearly anyone can get a brain abscess, but certain groups of people are at a higher risk than others. Some diseases, disorders, and conditions that raise your risk include:
- a compromised immune system due to HIV or AIDS
- cancer and other chronic illnesses
- congenital heart disease
- major head injury or skull fracture
- meningitis
- immunosuppressant drugs, such as those used in chemotherapy
- chronic sinus or middle ear infections
Certain birth defects allow infections to reach the brain more easily through the teeth and intestines. One example of this is tetralogy of Fallot, which is a heart defect.
TREATMENT-
Treatment for a brain abscess usually involves a combination of medicines and surgery, depending on the size and number of brain abscesses.
A brain abscess is a medical emergency, so you’ll need treatment in hospital until your condition is stable.
Treatment with medicines often begins before a diagnosis is confirmed to reduce the risk of complications.
Medicines
In some cases, it may be possible to treat an abscess with medicine alone, or surgery may be too risky.
Medicines are recommended over surgery if you have:
- several abscesses
- a small abscess (less than 2cm)
- an abscess deep inside the brain
- meningitis (an infection of the protective membranes that surround the brain) as well as an abscess
- hydrocephalus (a build-up of fluid on the brain)
You’ll normally be given antibiotics or antifungal medicine through a drip, directly into a vein. Doctors will aim to treat the abscess and the original infection that caused it.
Surgery
If the abscess is larger than 2cm, it’s usually necessary to drain the pus out of the abscess. However, you’ll still need a course of antibiotics after surgery.
There are 2 surgical techniques for treating a brain abscess:
- simple aspiration
- craniotomy
Simple aspiration involves using a CT scan to locate the abscess and then drilling a small hole known as a “burr hole” into the skull. The pus is drained and the hole sealed.
A simple aspiration takes around an hour to complete.
Open aspiration and excisions are usually carried out using a surgical procedure known as a craniotomy.
Craniotomy
A craniotomy may be recommended if an abscess does not respond to aspiration or reoccurs at a later date.
During a craniotomy, the surgeon shaves a small section of your hair and removes a small piece of your skull bone (a bone flap) to gain access to your brain.
The abscess is then drained of pus or totally removed. CT-guidance may be used during the operation, to allow the surgeon to more accurately locate the exact position of the abscess.
Once the abscess has been treated, the bone is replaced. The operation usually takes around 3 hours, which includes recovery from general anaesthetic, where you’re put to sleep.
Complications of a craniotomy
As with all surgery, a craniotomy carries risks, but serious complications are uncommon.
Possible complications of a craniotomy may include:
- swelling and bruising around your face – which is common after a craniotomy and should lessen after the operation
- headaches – these are common after a craniotomy and may last several months, but should eventually settle down
- a blood clot in the brain – further surgery may be required to remove it
- stiff jaw – the surgeon may need to make a small cut to a muscle that helps with chewing, which will heal but can become stiff for a few months; exercising the muscle by regularly chewing sugar-free gum should help relieve the stiffness
- movement of the bone flap – the bone flap in your skull may feel like it moves and you may experience a clicking sensation; this can feel strange, but it is not dangerous and will stop as the skull heals
The site of the cut (incision) in your skull can become infected, although this is uncommon. You’re usually given antibiotics around the time of your operation to prevent infection.
Recovering from surgery
Once your brain abscess has been treated, you’ll probably stay in hospital for several weeks so your body can be supported while you recover.
You’ll also receive a number of CT scans, to make sure the brain abscess has been completely removed.
Most people need a further 6 to 12 weeks rest at home before they’re fit enough to return to work or full-time education.
After treatment for a brain abscess, avoid any contact sport where there’s a risk of injury to the skull, such as boxing, rugby or football.
Advice for drivers
If you’ve had brain surgery and you hold a driving licence, you’re legally required to inform the Driver & Vehicle Licensing Agency (DVLA).
It’s likely that the DVLA will suspend your driving licence due to your increased risk of having a seizure. Your licence will only be returned once your GP or surgeon confirms it’s safe for you to drive.
For most people, this is likely to be 12 months after surgery without having any seizures during this time.
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