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Leptomeningeal enhancement on CT and MR imaging studies secondary to cryptococcal meningitis is an uncommon finding. In immunocompromised patients, this meningitis incites only a mild inflammatory reaction and abnormalities are often absent on imaging studies. We recently encountered two patients with cryptococcal meningitis in whom postcontrast MR imaging showed thick enhancing subarachnoid spaces. Both had cryptococcal meningitis at autopsy. In a different patient with cryptococcal meningitis, postmortem MR imaging and pathologic examinations showed that these areas of enhancement correspond to abundant mucoid material secreted by the yeasts.

The dynamic computed tomography (CT) study of the brain consists of the rapid intravenous injection of 49 ml of radiographic contrast material in 7 sec followed by serial 5 sec CT scans with interscan times of only 1 sec. The data from these scans can be reprocessed to create 12 segmented images in 35 sec. When small samples of four to six pixels of cortex are examined by the cursor, sharp rises of 20 to 25 CT units (500 scale) are seen on the time--density curves. Samples of white matter are usually no more than 2 CT units. When larger cursor samples of 220 to 255 pixels including cortex and white matter are examined, the time--density curves represent a combination of these two patterns. Comparison between symmetrical areas in the two hemispheres generally shows parallel curves in controls. The studies provide high resolution cerebral perfusion images. In ischemia secondary to ipsilateral carotid stenosis, there is depression of the up-slope and a depressed and late peak. Infarctions show a flat perfusion curve. Several patterns in brain tumors are illustrated. The study, simple to perform, adds significant perfusion information to the previously static CT examination of the brain.

We present two patients with AIDS complicated by cryptococcal meningitis who displayed focal hypodense nonenhancing lesions in CT in the basal ganglia with corresponding areas of increased T2 and decreased T1 signal on magnetic resonance (MR). These lesions corresponded precisely to the distribution of the perforating arteries. Review of pathological specimens showed these lesions to be small cystic collections of cryptococcal organisms in the perivascular spaces of the arteries with minimal or no inflammatory reaction. The cryptococcal organisms spread from the basal cisterns through the Virchow-Robin spaces, dilating these spaces, to ultimately propagate in the basal ganglia, internal capsule, thalamus, and brain stem. Such lesions have been described as characteristic for cryptococcosis in the pathology literature before the AIDS epidemic, but the radiological manifestations have not been reported previously. The changes appear characteristic for cryptococcosis, which generally incites no host response in the form of perifocal edema or enhancement. These findings in a young adult, with otherwise normal CT or MR scans, may be the first indication that the patient has AIDS. The T2-weighted image sequences are more sensitive in the detection of these lesions when compared to CT or T1-weighted MR images.

Two initially healthy infants developed acute encephalopathic illnesses characterized by stupor, seizures, cerebrospinal fluid (CSF) erythrocytic and monocytic pleocytosis, increased CSF protein, and decreased CSF glucose and progression to chronic decerebration. In one case, herpes simplex virus was recovered from cutaneous lesions. The initial computed tomography (CT) scan revealed widespread subcortical increased attenuation with further increase after contrast medium injection and patchy areas of decreased attenuation in the deep cerebral white matter. Subsequent CT scans demonstrated progressive cortical calcifications and persistence of low attenuation areas. Autopsy revealed multiple cystic encephalomalacia. The second infant had similar clinical, CSF, and CT findings but remains in a chronic decerebrate state at 14 months of age. The CT abnormalities seen in these patients have not been encountered in any of 13 other infants with the clinical diagnosis of meningitis or encephalitis. Multiple cystic encephalomalacia of infancy is a rare condition with a uniformly bleak prognosis. Computed tomography may prove useful in the early diagnosis, thereby aiding clinicians in counseling and in the acute and long-term management of patients with this lesion.

Computed tomography (CT) in a child with typical clinical and biochemical features of adrenoleukodystrophy (ALD) revealed striking pathologic enhancement in the centra semiovalia, posterior corpus callosum, and corticospinal tracts within the internal capsules, cerebral peduncles, and basis pontis. Central calcifications were detected within otherwise typical symmetrical low attenuation lesions in the periatrial white matter. These findings further expand the spectrum of CT abnormalities in ALD and may represent a link between the recently described Type 1 and Type 11 CT patterns.

A case of neonatal herpes simplex virus (HSV) encephalitis is reported in which diffuse cerebral hemorrhagic lesions were seen in the neonatal period. Severe progressive cortical atrophy with parenchymal calcification developed over the subsequent 9 months, resulting in a striking computed tomography (CT) appearance. The range of CT findings in neonatal HSV encephalitis is reviewed, and differential diagnostic considerations in the present case are discussed.

We report on a 46-year-old man with a congenital nasal dermoid cyst that extended intracranially to form large bifrontal intraaxial dermoid cysts, which became secondarily infected through a nasal dermal sinus tract. Computed tomography demonstrated bilateral frontal lobe ring enhancing cystic masses containing fat-fluid levels consistent with dermoid cyst abscesses. Axial and coronal CT of the skull base and nose demonstrated a midline bony canal extending from two dimples on the dorsum of the patient's nose to the base of the anterior cranial fossa. The clinical, CT, and surgical findings are reviewed as well as the embryogenesis of congenital nasal dermoid cysts.

A malignant epidermoid tumor invading the fourth ventricle had histologic features that indicated malignant transformation in a benign epidermoid cyst. The computed tomographic (CT) findings correlated precisely with the histologic features, revealing both pathologic enhancement and a low attenuation zone. The spectrum of described CT findings in intracranial epidermoids is reviewed and contrasted with the appearance encountered in the present case.

This preliminary report describes the application of dynamic computed tomography (CT) to the study of the kidney. The study is a simple, rapid, noninterventional test that gives time--density perfusion curves for the renal cortices as compared with aortic perfusion. In normal subjects, renal cortical time--density curves almost parallel the aortic time--density curve. In theory, decreases in perfusion in the kidney should show a renal cortical perfusion curve that is flattened and no longer parallel to the aortic curve. An experimental model for renal infarction was developed in the dog. Time--density curves taken from the infarcted area do show a depressed renal perfusion curve, with a lower peak than the curve for the contralateral kidney. Dynamic CT may be useful in screening human subjects for possible renovascular hypertension.

The computed tomography (CT) scans of 92 infants and children were reviewed. Thirty-three had proven atrophy, and 44 had proven obstructive hydrocephalus. Twelve CT measurements were made, and the results were subjected to computer analysis. The pathologic patients were divided into three groups by ventricular size index: mild (33--39%), moderate (40--46%), and severe (greater than 46%) enlargement. Obstructive patients showed much greater measurements for the temporal horn diameter and the frontal horn radius. The angle of the frontal horn was narrower in the obstructed group than in the atrophic patients. As expected, there were significantly more sulci visualized in the atrophic group than in the obstructed group. Three of these four parameters were directly related to concentric expansion of the ventricles in the presence of obstructive hydrocephalus. This is contrasted with passive dilatation of the ventricular system with preservation of the normal ventricular configuration in atrophy. The temporal horn diameter, frontal horn radius, the angle of the frontal horn, and the number of sulci all distinguish between obstruction and atrophy with individual probabilities of less than 0.05. When used together, they assure a high probability of separating obstruction from atrophy. Preliminary data suggest that these findings may have application in adults, but the number of confirmed observations has been too small for statistical analysis.

Two patients, one with malnutrition due to anorexia nervosa and one with Cushing's syndrome, showed evidence of cerebral atrophy by computed tomography (CT) of the brain. Several months after the original diagnosis of cerebral atrophy, follow-up CT studies demonstrated essentially total return to normality. It is postulated that the mechanism responsible for the described atrophic changes may be related to protein loss or fluid retention, or both. Correction of these metabolic abnormalities may be followed, as in the two cases reported here, by reversion of the CT findings to normality.

A representation of cerebral perfusion is obtained using cranial computed tomography following the rapid bolus injection of iodinated intravenous contrast medium. This technique permits the definition of four gross patterns of perfusion (normal, circulatory arrest, hypoperfusion, and hyperperfusion). This classification is affirmed in an experimental model of cerebral infarction in the baboon. The limitations of dynamic imaging using computed tomography are reviewed.