Cranial CT in acquired immunodeficiency syndrome: spectrum of diseases and optimal contrast enhancement technique.

A retrospective review of cranial CT scans obtained over a 4 year period in patients with acquired immunodeficiency syndrome (AIDS) and documented central nervous system (CNS) pathology is presented. The spectrum of diseases and the value of CT in detecting new, recurrent, and superimposed disease processes were determined. Fifty-one AIDS patients with confirmed CNS pathology were identified. Six of them had two coexistent diseases. Opportunistic infections predominated, especially Toxoplasma encephalitis and cryptococcal meningitis, while tumor was seen infrequently. Initial CT was positive in 76% of cases. In contrast to meningeal processes, where it was not very effective, CT was very sensitive in detecting most parenchymal disease processes. Characteristic although not pathognomonic CT patterns were found for certain diseases. Improvement or resolution of CT abnormalities in patients on medical therapy for Toxoplasma encephalitis correlated well with clinical improvement. Recurrence of CT abnormalities correlated well with medical noncompliance. The optimal contrast enhancement technique for detecting CNS pathology and for monitoring the effectiveness of medical therapy was also evaluated by a prospective study in which both immediate (IDD) and 1 hr delayed (DDD) double-dose contrast CT scans were compared. The examination found to be diagnostically superior in 30 of the 41 IDD/DDD studies was the delayed scan. It is recommended that CT be used routinely and with the 1 hr DDD scan to evaluate and follow AIDS patients with neurologic symptoms and/or signs.