Normal Sonographic Variants of the Neonatal Head

Abstract

Normal sonograms on 50 infants admitted to the Johns Hopkins Hospital Neonatal Intensive Care Unit were reviewed as to the echogenicity of the caudate nucleus relative to the thalamus. The infants were divided into two populations according to gestational age and birth weight. A review of sequential follow-up examinations showed that the caudate nucleus of those infants whose gestational ages were less than 32 weeks or who weighed less than 1,500 g increased in echogenicity as the infants matured. The caudate nucleus of those infants whose gestational ages were greater than 32 weeks or who weighed more than 1,500 g decreased in echogenicity as the infants matured. The author observed that the variation in caudate nucleus echogenicity was a normal finding, not pathologic, and was dependent on maturation and gestational age. Also noted was the incidence of a band of occipital echogenicity posterior to the occipital horns of the lateral ventricles. Its presentation in a large percentage of infants in both populations demonstrated it to be a normal variant. Key words: neonatal, echoencephalography, neurosonography, cerebral echogenicity, caudate nucleus, intracranial hemorrhage, high-risk pregnancy.In recent years, sonography has proved to be a valuable diagnostic study.' The most common diagnostic methods used in recognizing neonatal intracranial pathology before sonography were cranial computed tomography and clinical evaluation.2 Previous research has proven the usefulness of sonography in the diagnosis of hydrocephalus and cystic malformations.3More recent studies have demonstrated its value in detecting various forms of cerebroventricular hemorrages Ultrasound examination of the neonatal brain demonstrates that the caudate nucleus is usually slightly more echogenic than the thalamus, being nearly equivalent in echogenicity to that of surrounding brain parenchyma.3 Occasionally, the caudate nucleus has been observed to be considerably more echogenic than the thalamus; this finding may be misinterpreted as hemorrhage. Similarly, a band of increased echogenicity has been observed posterior to the lateral ventricles; this may be erroneously identified as hemorrhage. This retrospective study was undertaken to evaluate the degree of echogenicity of the caudate nucleus relative to the thalamus in normal cases and to determine the incidence of the occipital echogenicity posterior to the lateral ventricles. Recognition of the normal patterns of echogenicity is important to distinguish them from hemorrhage. MATERIALS AND METHODSSonograms on 50 infants admitted to the Johns Hopkins Hospital Neonatal Intensive Care Unit were reviewed. Sonograms were selected as normal on the basis of 1) normal ventricular size; 2) no evidence of intraventricular echogenic material; and 3) no evidence of subependymal or intraparenchymal echogenic focus.Each study was reviewed as to the echogenicity of the caudate nucleus relative to the thalamus to the right and left of the midsagittal plane. If the caudate nucleus was equal in echogenicity ...