Differentiation and investigation of primary versus secondary hypertension (Cushing reflex).

Hypertensive encephalopathy is a rare complication of severe or malignant hypertension. When treated promptly it is potentially reversible without leaving long-term neurologic damage. It can be difficult to differentiate from cerebrovascular accidents or uremia. Acute elevations of intracranial pressure cause acute elevations of blood pressure--the Cushing reflex. This association is less clear for chronic elevations of intracranial pressure, which could occur with tumors. In patients with hypertensive encephalopathy, there are usually diffuse neurologic signs, evidence of visual upset, variable alterations in conscious level, and often a history of rather gradual onset and more systemic symptoms beforehand. The optic fundi show the characteristic hemorrhages, exudates and papilledema, while the urine usually contains protein red cells and casts. Early treatment is mandatory but need not be by the parenteral route, and any blood pressure reduction should be gradual. Vigorous antihypertensive therapy under such circumstances can lead to problems with relative hypotension and underperfusion of vital organs such as the brain, the heart and the kidneys.