Detection of fetal central nervous system anomalies: A practical level of effort for a routine sonogram

Article Abstract:

Fetal ultrasound (US) examinations are being used in a wide variety of cases, such as maternal diabetes, multiple gestation, and the evaluation of factors affecting risk for fetal abnormalities. Evaluation of the development of the fetal central nervous system (CNS) is one of the most important areas of US utilization. With the large number of reported fetal abnormalities diagnosed via US, the survey for fetal anomalies has become more difficult and time consuming. The evaluation of second- and third-trimester CNS anomalies is both time-consuming and technically demanding because it involves a detailed exam of the intracranial anatomy as well as a diagnosis of the spine. Movement and position of the fetus can compromise the accuracy of the US image. The experience level of the US operator is an important factor as well; the diversity of anomalies adds to the need for experienced US technicians. The efficacy of observing three easily demonstrated fetal brain structures for the identification of prenatal CNS anomalies was studied. Of the three brain sites chosen for study the most powerful single observation for the detection of fetal CNS abnormalities is a measurement of the ventricular atrium. This structure of the brain is easily identified and assessed. The ventricular atrium was associated with 88 percent of the fetuses with CNS anomalies in this study. It is important to note that in the absence of a specific risk factor, the probability is raised to 99.900 percent that a fetus is normal before any examination of the brain or spine anatomy is completed. If the ventricular atrium measures ten millimeters or less, the probability of normalcy increases to 99.988 percent. The researchers also chose to include the cisterna magna and the cavum septi pellucidi in the battery of US exams for the evaluation of fetal abnormalities because of the frequent involvement of these parts of the fetal anatomy in fetal anatomical abnormalities. In selecting these three structures for study it was concluded that the vast majority of US exams will yield the type, amount, and quality of information that is required to make a correct diagnosis of fetal CNS health and development. However, not all congenital CNS anomalies will be detected with the proposed method. Anomalies of neural migration, with few exceptions, are associated with normal ventricular size, normal cisterna magna size, and a normally formed cavum septi pellucidi. The proposed methods are best used during the examination of a fetus for standard obstetric indications.

Research, Central nervous system, Prenatal diagnosis, Ultrasonics in obstetrics

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Mild lateral cerebral ventricular dilatation in utero: clinical significance and prognosis

Article Abstract:

Sonography, an imaging technique using high-frequency sound waves, is often used to detect abnormal brain development in the fetus. Ventricular dilatation (enlargement of brain ventricles, spaces inside the brain) is the most common brain abnormality found and is indicative of a poor outcome for the fetus. This abnormality is considered mild (mild ventriculomegaly, MVM) in about 15 to 20 percent of the cases discovered. This study examined whether sonographically-detected ventricular dilatation was associated with a better fetal prognosis when the case was mild, and whether the prognosis was better when MVM was found without other detectable problems. The records were reviewed of 39 cases of MVM, and 16 additional cases were followed-up. Results showed that 13 cases of MVM were not associated with other abnormalities, 23 had MVM plus a central nervous system (CNS) abnormality, 14 had MVM plus a CNS and a non-CNS abnormality, and 5 had MVM with only a non-CNS abnormality. Pregnancy was terminated in 30 of the cases, neonatal death occurred in 10 cases, and there were 15 live births. Combining the groups with MVM and other abnormalities versus MVM alone, deaths occurred in 83 percent of MVM-plus-other-abnormality cases and in 38 percent of MVM-alone cases. When leaving out terminated pregnancies, death occurred in 56 percent of the cases of MVM plus some other abnormality, and in 11 percent of the MVM-only cases. In the living children, six of eight who had MVM only were developing normally, with one having an unknown outcome and one with abnormal development. In the other living children, who had nonisolated MVM, development was normal in three, abnormal in one, and unknown or unavailable in three. Abnormalities not discovered by sonography were later found in 37 percent of the cases, but this would have only resulted in only one change from the MVM-only category, to the MVM-plus-other-abnormality category. These results indicate that when MVM is found using sonography, and no associated abnormalities are found with it, fetal prognosis is significantly more favorable. (Consumer Summary produced by Reliance Medical Information, Inc.)

Ultrasound imaging, Fetal brain

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Effacement of the fetal cisterna magna in association with myelomeningocele

Article Abstract:

Myelomeningocele, or spina bifida, is a common fetal abnormality that is detectable with prenatal ultrasound (US). Spina bifida is associated with hydrocephalic infants, a condition in which there is an enlarged skull and compromised brain function. This disease is treatable, but if left untreated it is fatal in about half of all cases. The spinal defects that occur in the fetus are often small, and may be difficult to detect on US exams due to the position of the fetus, fetal movement, maternal obesity, small size of the spinal defect, or the inexperience of the US technologist. The size of the fetal cisterna magna, the large cavity of the skull, is a good predictor of fetal myelomeningocele, and should be targeted for evaluation by the sonographer. The utility of evaluating the cisterna magna to identify spina bifida in a high-risk population of pregnant women was analyzed. The practical value of assessing the size of the cisterna magna is strengthened by the ease and consistency with which the cisterna magna is demonstrated in normal fetuses aged sixteen to twenty-four menstrual weeks, when most high- and low risk patients are referred for sonograms. A regular-sized cisterna magna is generally an indication that the fetus does not have spina bifida.

Risk factors, Pediatric diseases, Myelomeningocele, Meningomyelocele, Hydrocephalus in children, Hydrocephalus

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