Fig. 6.58 A-G. Cerebral paracoccidioidomycosis. CT scanning will often show enhancing nodules, some with a peripheral rim of enhancement such as A in the parietal cortex, or B in the brain stem. C A thalamic lesion which is small and surrounded by marked edema. The lesions in A-C are all cerebral granulomas. D-G are scans of a different patient and show enhancement of the meninges and cortical gyri, particularly in the basal cysterns. A small nodule with peripheral enhancement is present in the left frontal lobe (G) and there is also ventricular enlargement. These changes are due to meningoencephalitis. (Courtesy of Drs. A.C. Francesconi do Valle and R. R. Guimaras, Rio de Janeiro)

Imaging Diagnosis

The chest images reflect the different patterns of the infection.

Peripheral pleural fungal collections may be found in patients who are asymptomatic: these appear as multiple subpleural masses, often bilateral. Granulomas may also occur in the lung parenchyma, particularly in the lower lobes: they are best imaged by CT scanning. On plain radiographs they are from 0.5 to 4 cm in diameter and appear solid, almost always without cavitation or calcification. However, on lung biopsy (which is the most likely way to establish the diagnosis) there will probably be some central necrosis. CT or standard tomography may show air bronchograms in some of these masses. These well-circumscribed granulomatous nodules have been called "toruloma" in some publications.

In patients who presented clinically with chronic flu-like symptoms or more severe illness, chest radiographs may show unilateral or bilateral consolidation, which can be segmental or lobar. There may be a discrepancy in the appearance between frontal and lateral projections (Fig. 6.62 D, E). Because this "consolidation" is fungal rather than inflammatory, air bronchograms may be seen on standard tomography or, better, by CT scanning. Patients with cryptococcal pneumonia may have hilar or mediastinal lymphadenopathy.

In patients who are immunocompromised, and in a few patients in whom the apparent balance between the infection and host is unexpectedly disturbed, dissemination of the infection may occur. There is usually clinical evidence that the patient's illness has worsened. The chest radiographs will then show miliary or diffuse reticulonodular patterns: interstitial thickening may be found on high-resolution CT scanning before it is recognized on chest radiographs.

Cryptococcosis then becomes a more severe and acute disease, and few patients remain relatively asymptomatic. In the majority there is rapid progression both clinically and radiographically. Disseminated lung disease, pleural effusions, and lymphadenopathy are common and in a few patients cavitation may be recognized in some of the pulmonary or subpleural nodules. Lymphadenopathy without any visible pulmonary lesions may occur, but is uncommon.

The extent of the pneumonic consolidation depends on the severity of the infection and the patient's immune response. In some, the consolidation is extensive and diffuse, but in others, with a poor response, the disease is more rapidly progressive and consolidation is less significant. Adult respiratory distress syndrome may develop.

Cryptococcal meningitis is the most frequent complication of disseminated infection in those who are immunocompromised. Many patients have only CNS symptoms and their chests are clinically and radiographically normal. In these patients, CT scanning may show a pulmonary focus and at autopsy there is almost always a pulmonary lesion even when the clinical presentation has been meningeal.

Magnetic resonance imaging and CT scanning may show focal meningitis, dilated perivascular spaces, and multiple cryptococcomas. In the basal ganglia and midbrain there is usually symmetrical perivascular infection with multiple miliary nodules. There can be cryptococcomas in the brain, apparently without meningeal involvement; more commonly, both parenchymal and meningeal infections coexist. Perivascular invasion is best seen on MRI: on T 1-weighted sequences it will appear symmetrical, bilateral, and hypointense or isointense, and on T 2-weighted sequences as hyperintense areas. The appearance in the basal ganglia, thalamus, and substantia nigra has been described as "soap bubbles." Gadolinium-enhanced T 1-weighted sequences will identify miliary nodules more clearly. Cryptococcomas are hypointense on T 1-weighted scans and hyperintense on T 2-weighted scans, which often show surrounding edema. Following intravenous gadolinium contrast, there may be ring enhancement (Tiweighted scans).

Plain skull radiographs are of no significant value in the diagnosis of cryptococcosis, but may show well-circumscribed osteolytic lesions, with very little periosteal reaction. The same osteolytic pattern is found whenever any bone is involved. The gelatinous material from these bone lesions may spread into the subcutaneous tissues and resemble a tuberculous abscess. It can be imaged by ultrasound or MRI. Skeletal infections can be detected by radioisotope scanning. Fortunately, such skeletal lesions seldom, if ever, occur unless there is disseminated cryptococcosis, because there are no specific diagnostic findings on imaging.