Type:
Educational Exhibit
Keywords:
CNS, Neuroradiology brain, CT, MR, Biopsy, AIDS, Infection, Cerebrospinal fluid
Authors:
F. LEITÃO1, P. COIMBRA2, P. M. Brasil1, J. Benevides Lima1, D. Brilhante1, T. Camara da Silva1, K. portela luz1, L. P. PEREIRA1, C. Leite Macedo Filho1; 1Fortaleza/BR, 2Fortaleza, CEARA/BR
DOI:
10.1594/ecr2018/C-0919
Background
Cryptococcus neoformans, a saprophytic fungus isolated from soil contaminated with bird excreta,
is particularly pathogenic in immunocompromised patients and is the third most common pathogen in central nervous system (CNS) infections,
in patients with acquired immunodeficiency syndrome (AIDS),
after infection with human immunodeficiency virus (HIV) and Toxoplasma gondii.
The major environmental sources of C.
neoformans include soil contaminated with pigeon excreta and eucalyptus trees/decaying wood. C.
neoformans var. gattii is found mainly in tropical and subtropical regions,
whereas C.
neoformans var. neoformans is encountered worldwide. C.
neoformans var. neoformans usually infects immunodeficient individuals,
leading to acute diffuse meningitis or meningoencephalitis.
In contrast,
infection with C.
neoformans var. gattii more typically manifests as a granulomatous inflammatory response in immunocompetent hosts.
The respiratory tract is the primary site of fungal infection in humans,
and the yeast forms of fungi spread hematogenously from the lungs to the CNS,
from which they penetrate the meningeal vessel walls,
migrating to the Virchow-Robin (perivascular) spaces,
which subsequently become dilated following the activation of inflammatory cells and the deposition of mucoid material.
Once the fungus crosses the blood-brain barrier,
the CNS provides an appropriate environment for fungal multiplication. C.
neoformans has a predilection for the CNS because of the presence of specific neuronal substrates,
especially neurotransmitters,
that can be used by the fungus to produce melanin,
which protects the fungus against oxidative stress,
phagocytosis,
and antifungal drugs,
as well as modifying the host immune responses.
The most common clinical findings in CNS cryptococcal infection are headache,
nausea,
and fever,
less common manifestations are meningism,
confusion (altered mental state),
seizures,
visual symptoms,
and focal neurological deficit.
A diagnosis of fungal CNS infection must be considered in every immunocompromised patient with any of those manifestations.
Cryptococcal meningitis is the leading fungal infection of the CNS in individuals with AIDS and the third leading neurological complication in HIV-infected patients. Neurocryptococcosis had become a major concern with the spread of AIDS,
and the spectrum of magnetic resonance imaging (MRI) patterns associated with CNS cryptococcal infection reflects the pathological behavior of the fungus.