Catherine J. Babcook

A Magnetic Resonance Template for Normal Neuronal Migration in the Fetus

OBJECTIVE Although the features of neuronal migration have been known since the turn of the century, the serial features of neuronal migration as seen with magnetic resonance imaging (MRI) have not been described. Our objective was to provide a template of the normal appearance and the temporal pattern of neuronal migration in the human fetal brain early in the second trimester as seen with MR imaging and to correlate our findings with histological sections and atlases. METHODS Twenty-eight normal fetal specimens, which ranged from 9 to 24 weeks of gestational age, were imaged with a 1.5 T clinical MRI unit by use of conventional spin echo, fast spin echo, and three-dimensional Fourier transformation spoiled gradient refocussed pulse sequences. RESULTS The three-dimensional Fourier transformation spoiled gradient refocussed pulse sequence provided the highest resolution images of neuronal migration. At 13 weeks of gestational age, the germinal matrix was identified. A five-layer pattern of the fetal forebrain, which included layers of neuroblast formation and migration, could be identified at 16 to 18 weeks by MRI. The germinal matrix and layers of migrating neurons diminished considerably in size by 21 weeks. Histological studies and correlation with anatomic atlases confirmed the MRI findings. CONCLUSION Images obtained by use of MRI with standard clinical pulse sequences can document the appearance and the temporal patterns of neuronal migration in postmortem fetal specimens. With the evolution of high-resolution MRI and faster scanning techniques, these findings may serve as a template for the in utero MRI appearance of neuronal migration and thereby compliment the antenatal ultrasonic investigation of congenital anomalies.

A magnetic resonance template for normal cerebellar development in the human fetus

OBJECTIVE Although ultrasound is the primary imaging modality for prenatal anatomic evaluation, some central nervous system malformations may be better defined with high-resolution magnetic resonance imaging (MRI). MRI allows us to visualize the features of brain development that were previously only seen histologically by embryologists and anatomists. Although there are several reports of the postnatal development of the cerebellum as revealed on magnetic resonance (MR) images, systematic MR studies of cerebellar development during the fetal period are lacking. Our objective was to use high-resolution MRI to provide a template of cerebellar development during the late first and early second trimesters, a period when the diagnosis of congenital malformations is most medicoethically relevant. The MR findings were then correlated with histological data. METHODS Twenty-six normal formalin-fixed fetal specimens with a gestational age of 9 to 24 weeks were examined with high-resolution MRI using a conventional clinical magnet and pulse sequences. The MR findings were correlated with the whole-mount histological specimens catalogued in a well-known fetal atlas. RESULTS Resolution of the morphological features of cerebellar development in fetuses greater than 10 weeks gestational age was possible. Development of the rhombic lips, vermis, fourth ventricular roof, foramen of Magendie, and the cerebellar fissures was documented. Development of the cerebellum as revealed on MR images lagged behind the known stages of development by as much as 5 weeks. Features of cerebellar histogenesis were beyond the resolution of MRI. However, differences in signal intensity between gray and white matter of the developing cerebellum were detected and are postulated to represent differences in cellularity and water content of the constituent tissues. CONCLUSION Direct correlation of MR images of fetuses during the late first and early second trimesters with anatomic atlases could result in a mistaken diagnosis of delayed or abnormal development of the posterior fossa contents because of a time lag in the detection of structures on MR images. An MR template of normal cerebellar development would be useful to avoid confusion of normal development with abnormal development and to identify the expected developmental features when provided the estimated gestational age of a fetus.

Prevalence of aneuploidy and additional anatomic abnormalities in fetuses with open spina bifida: population based study in Utah.

Data were used to determine the population prevalence of aneuploidy and additional anatomic abnormalities in fetuses with open spina bifida. The ability of sonography to predict aneuploidy and identify additional anatomic abnormalities in euploid fetuses was assessed. All cases of spina bifida occurring in the state of Utah from 1995 through 1997 were reviewed using Utah Birth Defect Network data, including stillborn, liveborn, and terminated cases. Chromosomes were known in 45 of 51 cases of open spina bifida. Of the 45 fetuses, 6 (13%) were aneuploid. Major anatomic abnormalities were present in four of six (67%) cases, and two of six (33%) cases had additional anomalies that could be missed sonographically. Of 39 euploid fetuses, 12 (31%) had additional abnormalities, but only half likely would be detected sonographically. Our 4% risk of aneuploidy in sonographically isolated spina bifida is substantially higher than the risk associated with advanced maternal age (0.37%).

Ruptured malignant ovarian tumor mimicking ruptured ectopic pregnancy.

Ovarian carcinoma is uncommon in premenopausal women and few cases appear during pregnancy. Acute symptoms, such as pain secondary to rupture or torsion, are unusual. The majority of women with epithelial ovarian carcinoma remain asymptomatic for long periods of time. When symptoms do occur they are often vague and nonspecific. Unsuspected ovarian carcinomas may be detected incidentally during routine obstetrical examinations. We present a case of ovarian carcinoma complicating an early pregnancy in a young woman with findings suggestive of ectopic pregnancy. The ultrasonographic findings also were initially thought to be consistent with ectopic pregnancy.