Hypertensive Encephalopathy

The hypertensive encephalopathy (term introduced in 1928) is the encephalopathic findings associated with the accelerated malignant phase of hypertension. The terms accelerated and malignant were used to describe the retinal findings associated with hypertension, as follows:

Accelerated hypertension is associated with group 3 Keith-Wagener-Barker retinopathy, which is characterized by retinal hemorrhages and exudates on funduscopic examination
Malignant hypertension is associated with group 4 Keith-Wagener-Barker retinopathy, which is characterized by the presence of papilledema, heralding neurologic impairment from an elevated intracranial pressure (ICP)

Hypertensive encephalopathy refers to the transient migratory neurologic symptoms that are associated with the malignant hypertensive state in a hypertensive emergency.

The clinical symptoms are usually reversible with prompt initiation of therapy. In the evaluation of an encephalopathic patient, it is vital to exclude systemic disorders and various cerebrovascular events that may present with a similar constellation of clinical findings.

Pathophysiology

The clinical manifestations of hypertensive encephalopathy are due to increased cerebral perfusion from the loss of blood-brain barrier integrity, which results in exudation of fluid into the brain. In normotensive individuals, an increase in systemic blood pressure over a certain range (ie, 60-125 mm Hg) induces cerebral arteriolar vasoconstriction, thereby preserving a constant cerebral blood flow (CBF) and an intact blood-brain barrier.In chronically hypertensive individuals, the cerebral autoregulatory range is gradually shifted to higher pressures as an adaptation to the chronic elevation of systemic blood pressure.This adaptive response is overwhelmed during a hypertensive emergency, in which the acute rise in systemic blood pressure exceeds the individual’s cerebral autoregulatory range, resulting in hydrostatic leakage across the capillaries within the central nervous system (CNS). Brain MRI scans have shown a pattern of typically posterior (occipital greater than frontal) brain edema that is reversible. This usually is termed reversible posterior leukoencephalopathy or posterior reversible encephalopathy syndrome (PRES).
With persistent elevation of the systemic blood pressure, arteriolar damage and necrosis occur.

54-year-old man with hypertensive brainstem encephalopathy. Admission computed tomography (CT) scan: Sequential axial CT images at the level of the upper brainstem show diffuse hypodensity of the upper pons (long black arrow), as well as hypodense areas within the superior cerebellar hemispheres (short black arrows

54-year-old man with hypertensive brainstem encephalopathy. Followup computed tomography (CT) scan: Sequential axial CT images at the level of the upper brainstem show almost complete resolution of the hypodense appearance of the upper pons, cerebellum white matter, and subthalamic nuclei bilaterally

Presentation

Patients usually have vague neurologic symptoms and may present with symptoms of headache, confusion, visual disturbances, seizures, nausea, and vomiting. Headaches are usually anterior and constant in nature. The onset of symptoms usually occurs over 24-48 hours, with neurologic progression over 24-48 hours.

Patients also may present with symptoms resulting from other end-organ damage.Examples of these symptoms include the following:

Cardiovascular symptoms of aortic dissection, congestive heart failure,angina, palpitations, irregular heartbeat, or dyspnea
Renal hematuria and acute renal failure

Special Considerations:

Hypertensive encephalopathy is a diagnosis of exclusion, and other potentially life-threatening causes must be considered in the assessment of a patient with neurologic deficits. In addition to the conditions listed in the differential diagnosis, other problems to be considered include the following: