Parasites affecting the brain include protozoa, animalia (metazoa), fungi, and stramenopila (formerly chromista). Clinical signs are variable. Typical infections with Toxoplasma gondii (congenital toxoplasmosis and acquired toxoplasmosis) and taeniasis (coenurosis and cysticercosis) are described.
Toxoplasmosis restricted to the CNS can be pαathogenetically classified as reactivation of a latent infection, whereas acute, systemic toxoplasmosis involving other organs is seen in patients who probably acquired the infection during HIV-induced immunosuppression. The ways of infection from cats to humans is described. Treatment of immunocompromised patients as well as of mothers and fetuses is quite succesful. Clinical outcome depends on the underlying cause of immunodeficiency. In congenital toxoplasmosis the infection has devastating effects.
Neurocysticercosis is the infection of the central nervous system and its covering by the larval stage of the tapeworm Taenia solium leading to the development of seizures, mental disturbances, focal neurologic deficits, and signs of space-occupying intracerebral lesions. Coenurosis is due to Taenia multiceps and T. serialis. Drug treatment has to be administered before surgical treatment and should be supplemented with concomitant steroid medication for minimizing the inflammatory response to dying larvae. Clinical outcome depends on the brain regions involved. The prognosis worsens when cyst ruptures during surgical removal.
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