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Hypertensive encephalopathy is a rare complication of severe hypertension that can lead to coma or death within hours if left untreated. Symptoms include severe headache, dizziness, confusion, blurred vision, nausea, vomiting, and seizures. Treatment involves the administration of parenteral drugs to lower blood pressure.
One of the complications of severe hypertension, or high blood pressure, is called hypertensive encephalopathy. This complication occurs when the brain doesn’t get enough blood to maintain life and function. It is important to differentiate hypertensive encephalopathy from other cerebrovascular diseases such as cerebral ischemia, stroke, delirium, seizures and uremic encephalopathy, because the treatment is different. If left untreated, hypertensive encephalopathy can lead to coma or death within hours. This is why it is called a hypertensive emergency.
Hypertensive encephalopathy is very rare, affecting only 1% of people with long-standing hypertension. The affected person is usually male and middle-aged. When Oppenheimer and Fishberg first used the term “hypertensive encephalopathy” in 1928, they were referring to a constellation of symptoms that included severe hypertension, acute kidney inflammation or nephritis, and brain dysfunction. In the past, cerebral symptoms accompanying this type of encephalopathy included cerebral hemorrhage, transient ischemia, dizziness, and headache. These symptoms were all associated with malignant hypertension, a syndrome in which a known hypertensive person experiences a sudden increase in blood pressure or a previously non-hypertensive person experiences a sudden and unpredictable increase in blood pressure.
The definition of hypertensive encephalopathy, however, has been changed. It now refers to transient and reversible neurological dysfunction in a person experiencing the malignant phase of hypertension. Other causes of this condition include acute nephritis, abrupt failure to take antihypertensive medications, Cushing’s syndrome, pheochromocytoma, and renal artery thrombosis. Pregnant women who suffer from preeclampsia or eclampsia and drug addicts who take cocaine, lysergic acid diethylamide (LSD), and amphetamines are also at risk for this condition.
A person with this condition would complain of a sudden onset of severe headache, dizziness, confusion, blurred or altered vision, nausea, vomiting, and seizures. When the doctor examines the patient’s eyes, papilloedema or swelling of the optic disc is observed, along with hemorrhages, cotton wool spots, and exudates. These funduscopy findings are collectively called grade IV retinal changes and indicate increased intracranial pressure.
How this type of encephalopathy is addressed can be explained by its pathophysiology. Normally, blood flow through the brain is maintained despite changes in blood pressure. For example, even if an individual’s systolic blood pressure increases by 60 to 150 millimeters of mercury (mmHg), the blood supply would not be compromised due to a process called autoregulation. This is because small blood vessels called arterioles narrow in response to a decrease in blood pressure, and dilate in response to an increase in blood pressure. When the autoregulatory mechanism fails in the upper blood pressure range, the result is dilation of blood vessels and excessive perfusion, or hyperperfusion, of the brain.
The goal of therapy is therefore to decrease blood pressure to restore normal perfusion. Treatment of hypertensive encephalopathy involves the administration of parenteral drugs. These drugs include nicardipine, labetalol and nitroprusside. They help by dilating blood vessels, thereby lowering blood pressure.
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