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Measuring maternal serum alpha-fetoprotein (AFP) levels in the second trimester is an effective screening test for identifying pregnancies at increased risk for neural tube defects. In the absence of a neural tube defect there are many nonpathologic and pathologic causes for elevated AFP including underestimated gestational age, twin gestation, impending fetal death, and rare fetal malformations. In this series, intraplacental sonolucent spaces were detected in a significant percentage of second trimester pregnancies with elevated serum AFP in the absence of any other cause for the elevation. It is postulated that these cystic spaces are a conduit for the transfer of fetal blood into the maternal circulation, thus accounting for the nonpathologic AFP elevation in the maternal serum.

The authors report an adult patient with a symptomatic interhemispheric cyst demonstrated by computerized tomography (CT), angiography, and at surgery. Choroid plexus epithelium was identified arising from the inner aspect of the cyst wall. Partial agenesis of the corpus callosum is postulated on the basis of the CT findings and the presence of choroid plexus in the interhemispheric cyst.

Serial neurosonography was performed in 210 high-risk, preterm neonates. Eleven (5.8%) demonstrated small cystic formations in the subependymal lining of the lateral ventricles. These subependymal cysts were unilateral and were detected at the exact site of a previous subependymal hemorrhage in two cases. These 11 infants were not significantly different in maturity, size, or clinical parameters from our main high-risk newborn population. Ten survivors had marked motor retardation at follow-up ages of 9-13 months, and one died from neonatal sepsis.

The ultrasonic appearance of the normal and abnormal fetal spine before 20 weeks' gestation was reviewed in 121 pregnances. A model was constructed to establish the mechanism of production in the various configurations seen. The relative roles of ultrasonography, alpha fetoprotein assay, and fetoscopy in the diagnosis of spina bifida are discussed.

Nonvisualization of the gallbladder is the primary finding in cholescintigraphy for acute cholecystitis. Recent investigators have described a useful secondary finding of increased pericholecystic hepatic activity (PCHA). A case of acute cholecystitis is presented in which the PCHA was round in configuration and appeared in the first 5 minutes of the study. This may be a source of diagnostic error if it is interpreted as visualization of the normal gallbladder. Appearance of the PCHA has not been previously described before 30 minutes. This case of early appearance raises the possibility that hyperemia may play a role as the cause in some forms of the PCHA. The phantom gallbladder was correctly identified as PCHA by observing the peak of activity of the PCHA occurring before the appearance of intrahepatic biliary radicals.