Nervous System- Infection & Inflammation I
Question No. 16. The Answer is: (A) Involving sequestration of parasitized erythrocytes leading to blockage and obstruction of blood vessels.
Discussion: Among the four species of plasmodium that would cause malaria, Plasmodium falciparum is the only species that would cause severe cerebral disease. The characteristic macroscopic feature is disseminated petechial hemorrhages in the brain. Abscess formation is not a usual feature. Microscopically, most of the small vessels and capillaries are characterized by swollen endothelial cells with extravasation of red cells. The number of erythrocytes containing parasites is disproportionately high in the cerebral capillaries when compared to the other part of the body (sequestration of parasitized erythrocytes in vessels of the brain). The parasites are in different stages of development. This lead to blockage of capillaries, thromboses, and petechial hemorrhages. Hypoxic-ischemic changes can occur due to the blockage of blood vessels. Malarial pigment can also be seen in the capillaries. Proteinaceous material may be seen around the involved vessels. There is necrosis of the perivascular white matter, and focal loss of myelin staining, accumulation of reactive microglia and astrocytes in the vicinity. However, there is no isolated demyelination of the dorsal column.
The petechial hemorrhages often contain a necrotic blood vessel at the center that is surrounded by a ring of necrotic, demyelinating tissue and further surrounded by an annulus of extravasated erythrocytes. Parasites, interestingly, are not usually found in these erythrocytes. Dürck granuloma is also a feature of cerebral malaria and they occur as nodules of reactive astrocytes and microglial cells containing a core of neutral lipids and iron pigment. These nodules are morphologically similar to those occuring after resolution of fat emboli. Chronic inflammation can also be present and may extend to the leptomeninges.
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