What is Posterior Reversible Encephalopathy Syndrome?
Posterior reversible encephalopathy syndrome, or PRES, is a condition that can change a person’s mental state, make them drowsy or even unconscious, affect their vision, or cause them to have seizures and headaches that start suddenly or are continuous and can’t be traced back to a specific location. Symptoms of PRES can appear quickly or over a longer period of time, usually developing within a few hours to a few days. Most often, PRES shows up when a person’s blood pressure can’t be controlled and is very high, typically between 160 to 190 millimeters of mercury (a unit for measuring blood pressure).
The name ‘Posterior Reversible Encephalopathy Syndrome’ comes from two observations: the first is how this condition looks on certain types of brain scans (like Magnetic Resonance Imaging, or MRI), which often show swelling (also known as edema) in certain areas towards the back of the brain. The swelling appears brighter on T2 images and darker on T1 images. But it’s also possible for this pattern to be asymmetric, with uneven distribution of the swelling. The second part of the name, ‘reversible’, comes from the fact that the symptoms can go away if the condition is identified and treated quickly.
However, the name ‘Posterior Reversible Encephalopathy Syndrome’ can be somewhat misleading. This is because the swelling isn’t always located in the back of the brain, but can show up in other areas as well. Also, while in most cases the condition is reversible, some people can experience serious, even life-threatening complications, such as a cerebellar herniation (where part of the brain shifts into an area it’s not supposed to be) and specific neurological problems, especially if they don’t receive treatment promptly.
What Causes Posterior Reversible Encephalopathy Syndrome?
Certain people are more likely to develop PRES (posterior reversible encephalopathy syndrome), a condition that impacts the brain, if they have certain risk factors. These factors can include high blood pressure, preeclampsia (a complication during pregnancy that causes high blood pressure), or kidney disease. Kidney disease can make the body have too little blood volume (hypovolemia) and cause secondary high blood pressure by activating the renin-angiotensin system, a body system that helps regulate blood pressure.
Other conditions, such as liver disease, exposure to certain medications that kill cancer cells or suppress the immune system, autoimmune disorders (where the body’s defense system attacks its own cells), and sepsis (a serious infection spreading throughout the body) also increase the risk.
Amongst these risk factors, high blood pressure that is not well-controlled is the most common. However, just having high blood pressure that comes on suddenly does not mean that a person will develop PRES, and it’s hard to predict which individuals with high blood pressure will end up developing it.
Risk Factors and Frequency for Posterior Reversible Encephalopathy Syndrome
PRES, short for Posterior Reversible Encephalopathy Syndrome, had been largely underdiagnosed, possibly because of limited awareness. But with better and more accessible imaging techniques, knowledge about PRES has improved. Recent research has shown us more about who this condition affects. It can impact people of all ages, but it appears most often in middle-aged women.
In one study that looked back at 113 patients with PRES, they found some interesting results. They learned that almost half of the patients (45%) were also suffering from an autoimmune disease. Most patients reported having seizures (74%), followed by symptoms like mental confusion or delirium (28%), headaches (26%), and issues with vision (20%). They discovered that having a seizure was the most likely indicator of PRES. Mental confusion or delirium came in as the second-most common indicator. Other key factors that indicated PRES were exposure to chemotherapy and kidney failure.
- PRES can affect anyone but is most common in middle-aged women.
- Nearly half of PRES patients in a study also had an autoimmune disease (45%).
- The most common symptoms associated with PRES are seizures (74%), mental confusion or delirium (28%), headaches (26%), and visual disturbances (20%).
- The most reliable sign of PRES is a seizure.
- Exposure to chemotherapy and kidney failure also suggest a higher chance of having PRES.
Signs and Symptoms of Posterior Reversible Encephalopathy Syndrome
Posterior Reversible Encephalopathy Syndrome (PRES) diagnosis relies on both clinical symptoms and radiographic findings. History taking and a physical examination are essential steps in diagnosing PRES. In the history taking process, questions about headache, visual issues like double vision or vision loss, having seizures, and any medications being taken are important.
Sometimes the person affected might not be able to provide a reliable history due to changes in their mental state. In these cases, gathering information from family members, friends or anyone who knows the person well can be helpful. While conducting a physical examination, doctors primarily look out for several signs.
- Partial or complete vision loss
- Ignoring one side of the field of vision
- Total blindness caused by brain damage (cortical blindness)
- Difficulty moving eyes horizontally but still being able to visually track a moving object (horizontal gaze palsy with intact vestibulo-ocular reflex)
- Swelling in the optic nerve (papilledema)
- Bites on the tongue resulting from a seizure (oral trauma)
- Overly responsive reflexes (brisk reflexes)
- Active seizures
- Loss of bladder or bowel control (urinary and fecal incontinence)
Testing for Posterior Reversible Encephalopathy Syndrome
In the case of suspecting a condition known as “PRES”, imaging tests are incredibly important as these are the key to making an accurate diagnosis. You may undergo a head CT scan which is a type of X-ray test that produces detailed images of your brain. This test is usually carried out when one experiences sudden changes in mental ability, headaches and seizures, as it can rule out other severe conditions like brain bleeding.
An MRI scan of the brain is typically the preferred imaging test for PRES. This test uses a powerful magnetic field and radio waves to create detailed images of the brain. You won’t need to be given a special dye (which is called contrast) for this test. The MRI looks for a specific change in the brain, known as vasogenic edema, which appears as a bright or ‘hyperintense’ signal on the test result. This change is most commonly found in the back of your brain but could occur in other regions too. The MRI scan also assists in investigating other possible conditions like damage from a lack of oxygen or blood flow to the brain, blocked blood flow in the back of the brain, and inflammation of the brain’s blood vessels.
Another imaging test which you might undergo is called a magnetic resonance angiography (MRA) of the brain. This type of scan typically appears normal in PRES but it can detect abnormal patterns of the brain’s blood vessels that could be potential signs of inflammation. Furthermore, you may have magnetic resonance venography (MRV). Just like MRA, MRV usually looks normal in PRES but it’s carried out to rule out blood clots in the brain’s large, central veins as a possible cause of your symptoms.
To find out what might have caused PRES, your doctor might recommend some blood tests. These tests will look at your electrolyte balance (minerals that are critical for body functions), levels of albumin (a protein) and potentially the presence of infections, such as herpes simplex virus which can cause a type of brain infection. The blood tests will also check if low blood sugar could be causing your symptoms.
There are times that a procedure called lumbar puncture might be necessary especially in individuals with weakened immune systems. This test involves taking a small sample of fluid from your spine in your lower back to look for signs of brain infection.
An electroencephalogram (EEG) may be done if you have PRES as well. This test measures electrical activity in your brain. It can be helpful especially if your mental state continually fluctuates without any visible physical movement which may hint at concealed seizures. However, the patterns observed in the EEG are usually not specific to any particular condition.
Treatment Options for Posterior Reversible Encephalopathy Syndrome
Managing a condition called PRES (Posterior Reversible Encephalopathy Syndrome) involves identifying and tackling the cause of the condition while also treating high blood pressure carefully. There hasn’t been a specific high blood pressure treatment plan officially recommended for people with PRES. However, doctors usually suggest addressing the issue when the blood pressure goes over 160/110. The target goal would be to bring it down to a range of 130-150 over 80-100.
Reducing blood pressure suddenly or drastically can sometimes interfere with the flow of blood to the brain, raising the risk for a condition called ischemia. Ischemia restricts blood flow to certain parts of the body, causing damage due to lack of oxygen and nutrients. As a result, it’s suggested that the blood pressure should not be lowered more than 10 to 20 units every 10 to 20 minutes.
This painstaking process of managing blood pressure might necessitate hospitalization in the intensive care unit until the blood pressure levels stabilize. After this stage, it is recommended to maintain the target blood pressure in a hospital setting or at home. The precise duration for continued high blood pressure medication after the acute phase is uncertain and will vary from person to person.
In some cases, people with PRES can face life-threatening conditions such as constant seizures or coma. In such situations, the person would be referred to the intensive care unit for managing these issues. At present, there isn’t an established seizure treatment for seizures in people with PRES, and research to identify a specific regimen is still ongoing. However, anti-seizure medication is sometimes given during the acute phase of the condition and stopped once PRES improves. In certain scenarios, complications such as long-term epilepsy may arise, wherein anti-seizure medications will have to be administered for a longer duration.
If PRES is caused due to a type of drug known as an immunosuppressant, it is usually recommended to reduce the dosage of the drug or replace it with a different one.
What else can Posterior Reversible Encephalopathy Syndrome be?
When a doctor is trying to diagnose PRES, which stands for Posterior Reversible Encephalopathy Syndrome, they must consider a wide range of other health conditions that can cause similar symptoms. Here are some of them:
- Bleeding within the brain (intracranial hemorrhage)
- Bleeding between the brain and the skull (subdural hemorrhage)
- Bleeding around the brain (subarachnoid hemorrhage)
- Blood clot in the brain’s venous sinuses (cerebral sinus venous thrombosis)
- Stroke affecting the back part of the brain, which could be due to lack of blood supply (ischemic) or bleeding (hemorrhagic)
- Blood clot in the basilar artery, a major blood vessel supplying the brain
- Inflammation of blood vessels in the brain (vasculitis of the central nervous system)
- Brain inflammation due to herpes simplex virus infection (herpes simplex encephalitis)
- Brain inflammation due to auto-immune disorders (autoimmune encephalitis)
- Brain disorder resulting from severe kidney disease (uremic encephalopathy)
- Low blood sugar (hypoglycemia)
What to expect with Posterior Reversible Encephalopathy Syndrome
If diagnosed and treated early, people with PRES, a health condition that affects the brain, usually have a positive outcome. Their symptoms often improve or disappear in a few days or weeks. Particularly, vision problems often completely go away, especially with early treatment. However, there have been some cases where some vision issues still remain even 3 to 4 months after the start of the illness. It is still unknown who might be more likely to experience these lasting vision issues.
It’s important to start treatment for PRES as soon as possible because if it’s delayed, the symptoms might become permanent. If PRES causes a lot of fluid buildup (also called ‘cerebral vasogenic edema’) in the brain, the outcome can get worse. This is because the pressure from this buildup can reduce blood flow and result in a condition called ‘ischemia’ where your tissues don’t get enough oxygen.
In some cases, if the condition also affects the brainstem (the part of your brain that connects to your spinal cord), the outcome can worsen. There have been instances where PRES came back in people who were getting dialysis, a treatment that filters waste from your blood when your kidneys can’t do it themselves.
Possible Complications When Diagnosed with Posterior Reversible Encephalopathy Syndrome
If Posterior Reversible Encephalopathy Syndrome (PRES) is not treated quickly, it can lead to serious complications. These can include specific neurological issues from restricted blood supply to the brain, epilepsy, and even life-threatening conditions. A severe issue that can occur includes transforaminal cerebellar herniation, a dangerous condition where part of the brain squeezes through a hole at the base of the skull. This has been reported in children.
Complications of untreated PRES:
- Specific neurological issues from poor blood supply to the brain
- Epilepsy
- Life-threatening conditions
- Transforaminal cerebellar herniation
Preventing Posterior Reversible Encephalopathy Syndrome
Recognizing and treating a condition known as PRES early on can help lower the chance of facing complications and improve the overall health outcome. It is crucial to be aware of this condition and to understand how to manage it properly. For example, learning how to control your blood pressure can decrease the chances of problems associated with brain blood flow, which can lead to PRES and other health issues. Additionally, understanding how certain types of immune-suppressing drugs affect the protective layer around your brain, even if you don’t have high blood pressure, can help healthcare providers be more alert to the development of PRES in patients who are taking these medications.
