Hypertensive Encephalopathy

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BACKGROUND AND CLINICAL INFORMATION: Head  

Hypertensive encephalopathy: refers to a relatively rapidly evolving syndrome of severe hypertension in association with severe headache, nausea, and vomiting, visual disturbances, convulsions, altered mental status and, in advanced cases, stupor and coma.

• When these diffuse symptoms are accompanied by focal or lateralizing neurologic signs, cerebral hemorrhage or infarction should be suspected. By the time the neurologic manifestations appear, the blood pressure has usually, but not always necessary, reached the malignant stage (i.e., diastolic pressure is about 130-165 mmHg). Lowering the blood pressure may reverse the picture in a day or two but uncontrolled hypertension is usually fatal. Hypertensive encephalopathy can complicate hypertension from any cause.

• In children, neurologic symptoms may occur with diastolic pressure still in the range of about 100 mmHg (normal upper limit for infant is 60-65 mmHg and for teenager is 80-85 mmHg). Renal disease is frequently present in children with hypertensive encephalopathy.

• When multiple infarcts occur over a period of months or years, vascular dementia may develop. The term Binswanger subcortical leukoencephalopathy may be used when the lesions are confined largely confined to the white matter with relative sparing of the cortex and the basal ganglia.

Ophthalmoscopic findings: typical findings include arteriolar disease, papilledema, cotton wool patches, hard exudates, and hemorrhage.

NEUROIMAGING: Head  

Imaging: radiologic findings often suggest large areas of infarctions or demyelination but the tendency to normlize over several weeks is remarkable. The major changes on MRI is bilaterally increased T2 signal intensity consistent with edema in the white matter often in the posterior part of the hemispheres. There is no mass effect and the fluid has no tendency to track along white matter tracks such as the corpus callosum.

Reversivle posterior leukoencephalopathy (reversible occipitoparietal encephalopathy): this is reversible syndrome of headache, altered mental status, seizures, and visual loss occuring primarily in adults in the setting of hypertension, eclampsia, and immunosuppression. Abrupt increase in blood pressure is often, but not necessarily, present. The white matter is primarily affected but the gray matter is also involved. Abnormal T2-weighed MRI signal is seen most common, but not exclusively, in the occipitoparietal white matter.

GROSS PATHOLOGY: Head  

The brain is usually of normal weight. There may be focal infarction or softening.

HISTOPATHOLOGY AND IMMUNOHISTOCHEMISTRY: Head  

Brain Pathology:

Lacunar infarcts are more frequently seen in cases with malignant hypertension than non-malignant hypertension.

Vascular and parenchymal lesions of the brain: The following lesions are typically multiple and show a diffuse distribution in the cases of malignant hypertension. They are most frequently confined to the brain stem, particularly the basis pontis, but are also present, in decreasing order of frequency, in the basal ganglia and diencephalon, cerebral white matter, cerebral cortex, and spinal cord.

• Fibrinoid necrosis: this is the most striking change and is seen in about 75% of the cases. It involves mainly the arterioles and, less commonly, small arteries up to approximately 0.2 mm in diameter. The walls appear swollen and homogenous and stained bright red with HE and deep blue or purple with PTAH. Fibrinous thrombi are also common and extravascular fibrin deposits are also present.

• Arteriosclerosis and arteriosclerosis: hyalinized changes similar to hypertensive changes of non-malignant hypertensions are also present. Focal irregularities of the wall are also present.

• Charcot-Bouchard microaneurysm: This is an infrequent observation. They are ecstatic aneurismal outpouches in an abnormal wall. Their lumina may be partially or completely obliterated and hemorrhage or hemosiderin laden macrophages are often found in the perivascular space. They can be seen in other small vessel disease and is not completely specific for hypertensive changes.

• Microscopic or miliary zones of infarction ranging from 100 micron to 2 mm in diameter are seen in all cases with malignant hypertension but not in benign hyperten. These areas are associated with vessels demonstrating either fibrinoid necrosis and fibrin occlusion or focal irregularities of the wall.

Petechial hemorrhage is also a frequent finding.

Ophthalmic pathology:

Retinal and choroid vascular changes: 

• Thickening and hyalinization of the vessel walls of arterioles and less frequently fibrinoid necrosis are seen in the retinal and choroid blood vessels. Microaneurysms are also present in some cases. Renal changes are similar to those in the CNS and eye.

• Retinal small infarcts are noted in the nerve fiber and ganglion cell layers around the vascular lesions and consist of retraction ball of Cajal surrounded by proliferating glial cells.

Optic nerve: sclerosis and hyalinization, and less often, fibrinoid necrosis are noted in the arterioles of the optic nerve.

Papilla edema: the papilla is protruded, swollen, and shows lateral extension.

Chester EM et al., Neurology 1978 28:928

Pavlakis SG et al., J Child Neurol 1999 14:277

Nag S et al., Lab Inv 1977 36:150

Rhonda R et al., J Child Neurol 1996 11:193

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Background    Neuroimaging    Gross Pathology    Histopathology & Immunohistochemistry   Reference