Echinococcosis

Echinococcosis (hydatoid disease) is acquired by the ingestion of food contaminated by eggs of Taenia echi-nococcus, a common intestinal parasite of dogs. The disease has a worldwide distribution and is prevalent in sheep- and cattle-breeding countries.

The embryos reach the liver through the portal system; through the systemic circulation, they reach the visceral organs, the brain and spinal cord, the skull, and vertebrae. Here they develop into cysts that contain

FIGURE 6.3 1

Cerebral cysticercosis, granular ependymitis, and acute obstructive hydrocephalus. A 44-year-old woman experienced episodic fever and two episodes of lymphocytic meningitis within 1 year prior to her death. Six days before she died, she developed acutely severe headache, confusion, constantly falling backwards, and urinary incontinence due to an acute hydrocephalus from occlusion of the third ventricle. A. A collapsed, dead cystocercous cyst in the dorsomedial aspect of the thalamus displays a structureless wavy collagenous wall (van Gieson). B. Wall of the third ventricle shows perivascular lymphocytic cuffing (HE). C. Granulation tissue infiltrates the floor of the third ventricle (von Gieson).

FIGURE 6.3 1

Cerebral cysticercosis, granular ependymitis, and acute obstructive hydrocephalus. A 44-year-old woman experienced episodic fever and two episodes of lymphocytic meningitis within 1 year prior to her death. Six days before she died, she developed acutely severe headache, confusion, constantly falling backwards, and urinary incontinence due to an acute hydrocephalus from occlusion of the third ventricle. A. A collapsed, dead cystocercous cyst in the dorsomedial aspect of the thalamus displays a structureless wavy collagenous wall (van Gieson). B. Wall of the third ventricle shows perivascular lymphocytic cuffing (HE). C. Granulation tissue infiltrates the floor of the third ventricle (von Gieson).

clear fluid and scoleces. The nervous system may also be secondarily involved from a ruptured hepatic or cardiac hydatid cyst. Spilling of the cyst contents may evoke an anaphylactic reaction and dissemination of infection.

Central nervous system echinococcosis is more common in children than in adults. The cysts are usually solitary and large, some reaching several centimeters. Clinically, they present as expanding mass lesions. On CT scan, they are round or oval, well-defined, hypodense cystic lesions with minimal or no ring enhancement.

Pathologically, the hydatid cyst can be granulosus or multiloculous (Fig. 6.32). The cyst wall consists of an inner germinal layer and an outer laminated layer. Mild mononuclear cell infiltrates and occasional foreign body giant cells surround the cysts.

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