What is Hypertensive Encephalopathy?
The blood supply to the brain primarily comes from two arteries – the internal carotid and the vertebral arteries. These arteries and their branches are located in a space called the subarachnoid space.
The internal carotid arteries start in the neck from arteries known as common carotid arteries, and they move upward to enter the base of the skull. From there, they make their way to the middle of the brain through passages called carotid canals. The terminal branches of these arteries are referred to as the anterior and middle cerebral arteries, which are the front part of the brain’s blood circulation. An artery called the anterior communicating artery connects the right and left anterior cerebral arteries.
The vertebral arteries begin as the first branches from the subclavian arteries located at the base of the neck. They make their way through spaces in the C1 to C6 vertebrae (the bones in your neck). The terminal branches of these arteries enter the brain and cross a large opening called the foramen magnum. The basilar artery, which arises from the fusion of the two vertebral arteries, ascends towards the upper part of the brainstem and splits into two posterior cerebral arteries. This constitutes the back part of the brain’s blood circulation.
The posterior communicating arteries link the internal carotid and posterior cerebral arteries, connecting the front and back circulations of the brain. This connection forms a circular network called the circle of Willis.
Veins in the brain drain into the dural venous sinuses, which ultimately connect to the internal jugular veins. The veins located on top of the brain drain into the topmost sinus, while those at the back and lower part of the brain drain into the straight, superior petrosal, and transverse sinuses.
The blood-brain barrier (BBB) is a unique feature of brain circulation. It separates the circulation of the brain from the rest of the body via endothelial cells joined by tight junctions. Other cells, like astrocytes and pericytes, also contribute to this barrier. This barrier prevents large or potentially harmful substances from entering the brain circulation.
Receptors found in the BBB respond to a hormonal system involving renin, aldosterone, and angiotensin. These receptors have crucial roles in regulating water and electrolyte balance, blood vessel resistance, antioxidative response, inflammation of brain tissue, and overall brain health.
A hypertensive emergency is a life-threatening condition that occurs due to extremely high blood pressure. This could lead to damage in various organs, like the lungs, heart, kidneys, aorta, eyes, brain, and during pregnancy (eclampsia). Damage to the organs can lead to conditions like pulmonary edema, heart ischemia, acute kidney failure, aortic dissection, retinopathy, encephalopathy, and brain hemorrhages.
Hypertensive encephalopathy is a rare condition that arises due to unrestrained high blood pressure. Symptoms include severe headaches, nausea, vomiting, visual disturbances, seizures, and changes in mental state. The condition is identified after other possible conditions affecting brain function have been ruled out. Lowering blood pressure quickly can significantly improve symptoms. Early detection of hypertensive encephalopathy is important for a positive outcome since timely treatment can reverse the symptoms of this condition.
What Causes Hypertensive Encephalopathy?
Hypertensive encephalopathy, a condition which affects the brain, is often caused by poorly managed primary hypertension, or high blood pressure. Secondary causes of high blood pressure, like kidney problems and adrenal gland tumors can also lead to this condition.
Normally, the brain has a system that allows it to change the resistance in the arteries in response to changes in the body. This ensures that the brain gets an appropriate supply of blood. But, when blood pressure rises too quickly, this system can fail leading to damage to the blood vessel walls. This, in turn, can cause disruption of the blood-brain barrier (a structure that stops certain particles in the blood from reaching the brain), along with leakage of plasma (liquid part of the blood), red blood cells, and other large particles.
Hypertensive encephalopathy can present with similar signs to other conditions that lead to brain swelling, such as Posterior Reversible Encephalopathy Syndrome (a condition where parts of the brain swell), hypertensive brainstem encephalopathy (inflammation of the lower part of the brain), and eclampsia (a severe complication in pregnancy).
Therefore, it’s important to check for underlying issues like kidney disease, drug use (especially stimulant drugs like amphetamines and cocaine), side effects of certain medications like those used to dampen the immune system, and high blood pressure conditions during pregnancy in patients who are not known to already have high blood pressure.
Risk Factors and Frequency for Hypertensive Encephalopathy
In the United States, about half of all adults have some level of high blood pressure. However, emergencies caused by high blood pressure make up less than 2% of cases in emergency departments. Among these emergencies, 15% are due to hypertensive encephalopathy, a severe condition resulting from extremely high blood pressure. The recorded number of people hospitalized due to this condition in the US significantly increased from 2000 to 2011. However, this rise is not just due to more cases but also due to changes in how we label and charge for these cases in the medical field.
Signs and Symptoms of Hypertensive Encephalopathy
Hypertensive emergencies can occur both outside and within a clinical setting and can get worse quickly without timely treatment. To tackle this, an initial assessment should be done to check the patient’s airway, breathing, circulation, mobility, and exposure to the environment. The patient’s blood pressure, heart, and brain functions should be constantly checked after the initial treatment. After the patient is stable, and other emergencies are ruled out, further examination and diagnostic tests can be started.
Patients may initially report symptoms like headaches, blurry vision, nausea, vomiting, tiredness, and neck pain that have been going on for hours or days. The patients who have these emergencies are usually aged 40 or older, have hypertension, and may not be consistently taking their antihypertensive medications. The symptoms can be triggered by trauma, emotional or physical stress, or coming out of anesthesia. If the symptoms persist or new symptoms like seizures or changes in mental status arise, the patient may need to get medical consultation.
It’s important to note that high blood pressure in patients under 40 is usually due to a secondary cause such as illegal drug use, pregnancy, or chronic kidney disease. The doctor must include tests for underlying conditions which might have led to the high blood pressure episode.
Acute high blood pressure is a systemic condition that can cause harm to other organs like the heart and kidneys. In many cases, brain malfunction (encephalopathy) may occur. This might be accompanied by heart and respiratory symptoms, such as chest pain and difficulty in breathing, regardless of the patient’s age.
The American College of Cardiology and American Heart Association (ACC/AHA) guidelines define stage 1 hypertension as having a systolic blood pressure (top number) of 130 mm Hg or a diastolic blood pressure (bottom number) of 80 mm Hg. However, according to the 8th Joint National Committee, hypertension is defined as having two or more blood pressure measurements within 2 years of either a systolic blood pressure of 130 mm Hg or a higher or diastolic blood pressure of 90 mm Hg or higher.
In clinical terms, patients with a systolic blood pressure higher than 180 mm Hg or diastolic blood pressure higher than 120 mm Hg without any symptoms are diagnosed with hypertensive urgency. However, acute damage to organs, such as happens with hypertensive encephalopathy, makes the condition a hypertensive emergency.
No matter the presentation, patients with high systolic or diastolic pressure as per ACC/AHA or JNC 8 guidelines should have a thorough physical exam, including a detailed assessment of their heart and brain. Signs of heart involvement may include extra heart sounds, high jugular venous pressure, swelling in both feet, or irregular breath sounds. Eye involvement can be checked by looking at the back of the eye, where hemorrhages, swelling of the macula, fibrinous leakages, or cotton wool spots may be observed. Neurological issues may be found if there are changes in consciousness and specific weaknesses, especially after a seizure. Transient and mild weakness may be associated with acute high blood pressure. Sudden unconsciousness and persistent lateralizing signs may point to a bleeding stroke, which can occur if high blood pressure is not handled quickly. Suspect a subarachnoid hemorrhage if patients report severe headaches with or without auras.
Acute damage to the kidneys, if present, may show decreased urine output, sudden behavioral changes, breathing difficulty, and seizures due to the build-up of waste products in the blood (uremia). Uremia may also worsen the brain damage caused by the sudden increase in blood pressure.
Testing for Hypertensive Encephalopathy
Untreated severe high blood pressure, or acute hypertension, can have serious consequences like seizures, stroke, coma, and even death. The diagnosis of acute hypertension is made in people with dangerously high blood pressure and symptoms affecting the brain, after other similar conditions are ruled out. Conditions like stroke and brain bleedings occur differently and are treated differently than high blood pressure, so those need to be ruled out first.
Monitoring of Vital Signs and Heart
It is important for patients suspected of acute hypertension to have their heart and vital signs monitored. An electrocardiogram (ECG), which measures the electrical activity of the heart, may be done initially to check heart function. Chronic high blood pressure may thicken the heart muscle, and signs pointing towards this can be observed in the ECG test. Unless there are previous ECG results for comparison, the doctor must also rule out a heart attack by checking markers in the blood called cardiac enzymes.
The ECG can also help detect high potassium levels (hyperkalemia) if there is an acute injury to the kidneys. In younger patients or individuals without a history of hypertension, ECG may show signs of poor blood flow to heart muscles caused by things like substance abuse, severe high blood pressure during pregnancy (preeclampsia), or kidney damage due to toxins.
Keeping an eye on blood pressure is crucial, especially right after starting high blood pressure medications. Sudden changes in heart and breathing rates may be signs of heart damage. If a patient has difficulty breathing, it is important to continuously monitor their oxygen levels.
For pregnant patients, especially those with labor contractions, the unborn baby’s heart rate might need to be monitored to assess their well-being.
Laboratory Tests
Initial blood tests conducted may include a complete blood count, a clotting profile, and a comprehensive metabolic panel. If acute hypertension is managed quickly, and there is no pre-existing condition, these test results are usually normal or only slightly abnormal. If they are abnormal, it could be due to an underlying condition or damage to organs by the high blood pressure.
Chronic kidney disease often results in a specific kind of anemia but not acute kidney injury. If the kidney function is very poor , it may affect the function of platelets, which are involved in clotting, leading to prolonged bleeding times. Poor kidney function can also bring about a decrease in sodium, and increase in creatinine, blood urea nitrogen, and potassium levels. It may also present with characteristic findings in arterial blood gases.
For women who have severe pregnancy-induced hypertension, the condition may advance to a condition called “HELLP syndrome”, which stands for hemolysis (breakdown of red blood cells), elevated liver enzymes, and low platelets count. HELLP syndrome can lead to widespread clotting and bleeding throughout the body.
Cardiac enzymes need to be tested for people suspected of having heart involvement. Elevated levels of certain heart enzymes and new changes on ECG could indicate acute damage to the heart.
A urine test can help identify potential kidney damage. It may show low urine output, abnormal cells, and protein if high blood pressure has caused damage to the kidneys. A urine toxicity test can also be considered, especially in young patients with sudden onset hypertension.
Imaging Studies
If the patient has a sudden change in behavior, altered consciousness, or specific neurological deficits, a brain computed tomography (CT) scan without contrast is a good initial imaging test. This specific type of scan can identify a stroke or brain bleed. However, Posterior Reversible Encephalopathy Syndrome (PRES), a disorder that presents with brain swelling, may not be picked up well on a CT but can be seen on a magnetic resonance imaging (MRI). Even though MRI is more sensitive in identifying regions of swelling in the brain, CT is usually quicker, more readily available and helps rule out many other conditions affecting the brain.
A lumbar puncture is not usually required to diagnose brain swelling due to high blood pressure, but it might be needed if they suspect brain infections.
If the patient has difficulty breathing or there is suspected heart involvement, a chest x-ray may be needed. Findings may include an enlarged heart and fluid in the lungs.
In patients with severe high blood pressure during pregnancy, an ultrasound scan of the pelvis may be needed to decide whether the baby can be safely delivered. The best treatment for severe hypertension during pregnancy is ending the pregnancy.
Treatment Options for Hypertensive Encephalopathy
A hypertensive emergency is when your blood pressure rises dangerously high. The first response to this usually occurs in the emergency department, with definitive care performed in an intensive care unit. The aim of the treatment involves using medications to gradually and delicately lower the systolic (higher number) blood pressure. The goal is to avoid dropping the blood pressure too quickly, as this could put you at risk of a stroke. Therefore, the blood pressure is slowly brought down. This approach minimizes the risk of events linked to inadequate blood flow to the brain and allows time for the blood vessels in the brain to heal. In some situations, like stroke or aortic dissection, blood pressure needs to be reduced faster.
Initially, medications delivered directly to the bloodstream are used. These types of medications allow a more precise control in reducing blood pressure. Commonly used medications include nicardipine, labetalol, esmolol, fenoldopam, sodium nitroprusside, and clevidipine. Oral medications, taken by mouth, are avoided in the beginning because they act slower and their effects can’t be adjusted as needed. After achieving the blood pressure target, intravenous medications can be gradually stopped and oral medications can be started.
Pregnancy-induced high blood pressure requires close monitoring due to the implications for both the mother and baby’s health. If the mother experiences a hypertensive emergency, including seizures, immediate delivery may be necessary, regardless of how far along in the pregnancy she might be.
In certain cases, where seizures have occurred, antiseizure medication may be necessary. This can be continued until symptoms and brain-imaging results improve, and then the medication may be tapered off. Deciding on the appropriate seizure treatment can depend on existing conditions, like pregnancy or kidney function issues.
Antihypertensive drugs are used to treat a condition known as PRES (Posterior Reversible Encephalopathy Syndrome) that is associated with high blood pressure. The main goal of treating PRES is to tackle the underlying cause, so managing this condition could involve reducing blood pressure, prescribing antiepileptic drugs, adjusting or stopping certain medications, as well as correcting any imbalance in electrolytes (minerals needed for body processes). In pregnant women, timely delivery must be ensured. For patients undergoing immunosuppressive therapy and presenting symptoms of PRES, adjustments to the therapeutic regimen might be required.
What else can Hypertensive Encephalopathy be?
When a doctor is trying to figure out if a patient has a condition called hypertensive encephalopathy, there are several other conditions that have similar symptoms that they will want to rule out:
- Ischemic or hemorrhagic stroke
- Intracerebral (inside the brain) hemorrhage
- Brain tumor
- Hidden (occult) brain trauma
- Acute toxic metabolic encephalopathy (a brain disorder caused by certain toxic substances)
- Hepatic encephalopathy (a brain disorder caused by liver disease)
- Central venous thrombosis (a blood clot in a major vein)
A good thorough medical examination and diagnostic tests can help the doctor figure out whether the patient has hypertensive encephalopathy or one of these other conditions.
What to expect with Hypertensive Encephalopathy
Hypertensive encephalopathy, a condition caused by high blood pressure affecting the brain, can often be reversed if blood pressure is carefully and gradually reduced. PRES, a particular condition affecting the brain originally thought to have favorable outcomes, has nonetheless been associated with death in 19% of diagnosed patients, with function impairment found in 44%.
The likelihood of recovery from PRES depends on if there are other coexisting health problems. Factors pointing to potential poor outcomes include having cancer, severe brain disease, delayed treatment of the underlying cause, problems with blood clotting, and high sugar levels in the blood.
Recent data suggests that outcomes are generally better for individuals with PRES caused by conditions related to high blood pressure in pregnancy, such as preeclampsia and eclampsia. However, certain issues seen on brain scans, like involvement of corpus callosum (thick band of nerve fibers in brain), severe brain swelling, worsening scan results, bleeding in the brain and restricted movement of water molecules within the brain tissues, contribute to poorer outcomes.
Once patients are discharged from the hospital, they should continue to closely monitor their blood pressure while at home. Failing to follow prescribed treatment for high blood pressure increases the chance of experiencing another health crisis caused by high blood pressure.
Possible Complications When Diagnosed with Hypertensive Encephalopathy
If a medical condition called a hypertensive emergency isn’t treated on time, it can lead to serious health problems. These problems can include kidney failure, an eye condition that affects the retina (retinopathy), heart attack, and stroke. Swelling in the brain can also get worse and result in continuous seizures (status epilepticus), a state of unconsciousness (coma), or even death if blood pressure continues to be high. This is especially risky for patients experiencing brain swelling with encephalopathy.
However, lowering blood pressure too quickly can also be dangerous. It can cause damage to organs like the heart, particularly in patients with longstanding high blood pressure. Their bodies have adjusted to this high blood pressure and reducing it aggressively can cause more harm than good.
People with certain risk factors are more likely to have recurrent cases of a condition called PRES, which is linked with high blood pressure. These risk factors include having an autoimmune disease, kidney failure, a painful condition affecting red blood cells called sickle cell crisis, and hypertensive crisis.
Common Consequences:
- Kidney failure
- Retinopathy (eye condition)
- Heart attack
- Stroke
- Worsening brain swelling
- Status epilepticus (continuous seizures)
- Coma
- Potential death
- Damage to organs due to too quick blood pressure reduction
- Recurrent cases of PRES
Preventing Hypertensive Encephalopathy
It’s important for patients to understand and follow their treatment plans, as well as regularly check their blood pressure at home. Doing this can help prevent dangerous spikes in blood pressure. Also, eating less sodium (salt) and cholesterol can be beneficial. Maintaining a healthy weight, eating a balanced diet, and exercising regularly are also suggested. These healthy lifestyle habits can help regulate blood pressure effectively.