CNS Nocardia in AIDS patients: CT and MRI with pathologic correlation

Since CNS nocardiosis is an often fatal yet potentially treatable infection in HIV patients, we sought to identify and characterize imaging features that may suggest the diagnosis in the appropriate clinical setting.

The CT scan (six), MR scans (one), or both (two) were evaluated in nine HIV patients with pathologically proven CNS Nocardia asteroides. Chest X-ray films were available in seven patients. Findings were correlated with pathologic examination.

All nine patients had brain abscesses, and in seven that received intravenous contrast agent, all lesions demonstrated ring enhancement. Five of nine patients had hydrocephalus and four of these had clinical evidence of meningitis. Small subependymal nodules were seen in five of nine patients and four of these also had meningitis. Pathologic examination in three of nine cases demonstrated a dense inflammatory infiltrate lining the ventricles that extended through the ependymal lining, producing small subependymal abscesses. Six of seven available chest X-ray films demonstrated infiltrates due to Nocardia.

Our radiologic-pathologic correlation indicates that in an HIV-positive patient with enhancing parenchymal lesions, the additional findings of subependymal nodules and/or meningitis may suggest the diagnosis of nocardiosis. An associated pulmonary infiltrate can provide a clue to the diagnosis and serve as more accessible site for biopsy or culture.