Zygomycetes (especially Mucor, Rhi-zopus)
Cryptococcus neofor- The point of entry for Cryptococcus is the lungs. Pul-mans monary infection is not evident in healthy individuals, but becomes invasive in immunocompromised patients. Cryptococcal meningitis is the most common CNS infection (50%)in chronically immuno-suppressed non-AIDS patients. Cryptococcal meningitis presents as a chronic febrile syndrome with headache. The ensuing meningoencephalitis reflects cognitive changes or dementia, irritability, personality changes, mass lesions with focal neurological deficits, and ocular abnormalities (papilledema, with or without loss of visual acuity, and cranial nerve palsies) in 40% of patients
Rhinocerebral disease typically occurs in patients with diabetic ketoacidosis or leukemia. The infection often begins as ulceration in the paranasal sinuses or in the palate, and may spread along perivascular and perineural channels through the cribriform plate into the frontal lobe, or through the orbital apex into the cavernous sinus. The Mucorales characteristically invade blood vessels, causing thrombosis and hemorrhagic infarctions as well as cerebritis
Aspergillosis involving the CNS has findings similar to those of mucormycosis. CNS aspergillosis may result either from direct extension of nasal cavity and paranasal sinus infection, or more commonly from hematogenous dissemination. By direct extension, Aspergillus invades the cavernous sinus and circle of Willis, resulting in angitis, thrombosis, and infarction. In hematogenous spread, septic infarction occurs, with associated cerebritis and abscess formation
Nocardia asteroides CNS infection occurs in 0.3 % of immunocompromised patients, as in AIDS, resulting in fever, headache, focal neurological deficits, and multiple brain abscesses
Candida albicans Candida CNS infection is a manifestation of dissemi nated disease, and is associated with intravenous drug use, indwelling venous catheters, abdominal surgery, and corticosteroid therapy. CNS infection with Candida species often results in scattered intraparenchy-mal granulomatous microabscesses secondary to arte-riolar occlusion. Meningitis is a common feature of CNS candidiasis, resulting from invasion of meningeal microvasculature by small groups of yeast cells
Coccidioides immitis Hematogenous spread of the endospores into the in-tracranial space results in meningeal inflammation, with infectious purulent and caseous granulomas, particularly at the base of the brain. Multiple coccidioidal microabscesses can be found in the cerebellum and periventricular area, causing secondary hydrocephalus
Blastomyces der- Hematogenous dissemination results in blastomycotic matitides meningitis, with an acute or fulminant onset of head ache, stiff neck, and focal signs
AIDS: acquired immune deficiency syndrome; CNS: central nervous system.
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