Page 186 - AIDSBK23C

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ALS, they are unusually rapidly progressive, they show evidence of inflammatory response in
the CNS which is typically absent in classical ALS, and they do not progress inexorably, but
show variable improvement with ART. Reports of classical ALS in patients with HIV infection
are rare and probably coincidental.[796]

MISCELLANEOUS FINDINGS.-- Purulent leptomeningitis, bacterial cerebritis, and
abscesses are often present in AIDS brains, particularly in persons with a history of injection
drug use. Bacterial infection is typically secondary to septicemia because of infection elsewhere,
usually a pneumonia. Organisms such as Staphylococcus aureus, Streptococcus pneumoniae,
Pseudomonas aeruginosa, and Haemophilus influenzae should be considered in such a
setting.[498,500] In a patient with gastrointestinal disease, Listeria monocytogenes should also
be included as a possible pathogen.[499,503] A vasculitis with surrounding hemorrhage, or a
septic infarct, are common microscopic findings.
In the absence of opportunistic infections and neoplasms characteristic for AIDS, cerebral
infarction in HIV infected persons is not common. Up to 7% of AIDS patients at autopsy may
show some evidence for cerebral infarction, but clinical findings to accompany these lesions
were rarely evident. A vasculopathy often accompanies the ischemic lesions and consists of
hyaline thickening of small vessels, perivascular space dilation, rarefaction, and pigment
deposition, with vessel wall mineralization and perivascular inflammatory cell infiltrates in some
cases. Intravascular thrombi are rarely observed. Similar features have been observed in the
arterial vasculopathy accompanying HIV infection in children.[797] In a study of HIV-infected
persons with stroke, 20% were due to HIV vasculopathy, while an infectious etiology was
present in 28%, coagulopathy 19%, embolism from cardiac lesions 14%, and multiple etiologies
in 11%. HIV vasculopathy may affect carotid arteries or medium-sized intracranial arteries, with
pathologic features including multiple fusiform aneurysm formation, dilation, stenosis, and
variable lumen diameter.[798]
In a small number of AIDS cases, there is extensive subarachnoid, intraventricular, or
intracerebral hemorrhage without a demonstrable opportunistic infection or evidence of trauma.
The cause may be a vasculitis from systemic bacterial infection, with the presence of
neutrophilic infiltrates in and around small cerebral vessels. Central nervous system
hemorrhages may be due to direct endothelial damage resulting from HIV infection.
An acute necrotizing meningoencephalitis may be produced by Trypanosoma cruzi
infection, and is distinguished from T gondii infection by the presence of amastigote-filled
macrophages in the former.[799] Bacillary angiomatosis, caused by Bartonella henselae, can
produce encephalitis, myelitis, cerebral arteritis, and retinitis.[800] Cerebral microsporidiosis
can occur with dissemination from the gastrointestinal tract, with appearance of multiple small
ring-enhancing lesions by magnetic resonance imaging, and appearance of the spores in
cerebrospinal fluid.[487]
Systemic fungal infections may involve the CNS. AIDS patients with disseminated
blastomycosis have CNS involvement in half of cases. Dissemination is more likely with lower
CD4 counts. The mortality rate is high.[628] Coccidioides immitis infection is most likely to
produce meningitis with clinical presentation of headache. Radiographic imaging may show
basilar meningitis and hydrocephalus requiring ventriculoperitoneal shunting. Fluconazole
therapy yields a good prognosis in most cases.[801]
Though Penicillium marneffei is best known for skin infection, it can affect the CNS.
Half of persons with CNS involvement may not have the characteristic umbilicated skin lesions.