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Antenatal diagnosis of partial agenesis of the corpus callosum: A benign cause of ventriculomegaly
Antenatal diagnosis of partial agenesis of the corpus callosum: A benign cause of ventriculomegaly Charles J. Lockwood, MD, Alessandro Ghidini, MD, Renu Aggarwal, MD, and John C. Hobbins, MD New Haven, Connecticut, and Mineola, New York Dilation of the posterior horns of the cerebral ventricles may be an early finding of fetal hydrocephalus, but it is also the hallmark of partial agenesis of the corpus callosum. Reported is the first precise prenatal diagnosis of posterior agenesis of the corpus callosum. Accurate diagnosis allows for appropriate obstetric management. (AM J OBSTET GYNECOL 1988;159:184-6.)
Key words: Agenesis of corpus callosum, ventriculomegally, prenatal diagnosis, ultrasound
The prenatal diagnosis of partial agenesis of the corpus callosum has not, to our knowledge, been reported in the world's literature. Because this anomaly is not rare and represents a benign cause of ventriculomegaly, its accurate diagnosis is important. Antenatal diagnosis in the present case allowed for parental reassurance and appropriate, noninvasive perinatal care.
Case report A 28-year-old woman (gravida, 3, para 1) underwent an initial ultrasound examination at 18 weeks' gestation that confirmed the gestationa~ age and noted no fetal malformations. A repeat ultrasound at 30 weeks' gestation to assess fetal growth identified "fetal hydrocephalus." The patient was then referred to the Yale Perinatal Unit. The patient's past medical history was noncontributory. There was no family history of neural tube defects, hydrocephalus, or other congenital neurologic abnormalities. The patient denied alcohol, drug, tobacco, or toxin exposure. Sonographic evaluation revealed a live singleton fetus in cephalic lie with a posterior placenta (grade 1) and a normal amount of amniotic fluid. Biometric data were consistent with 32 weeks' gestation and estimated fetal weight was in the 50th percentile. Stomach, bladder, kidneys, abdominal wall, extremities, face, and spine appeared normal. Evaluation of the cranial anatomy demonstrated a biparietal diameter of 7.9 cm (consistent with 32 weeks' gestation), a cephalic index of 80.6%, and a cephalic circumference of 28. 7 cm, all within normal limits. There was discrete enlargement of the posterior horns From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, and the Department of Neonatology and Newborn Medicine, Winthrop-University Hospital, University of New York at Stony Brook School of Medicine, Mineola. Received for publication May 6, 1987; accepted November 16, 1987. Reprint requests: Charles Lockwood, MD, Department of Obstetrics and Gynecology, St. Margaret's Hospital, 90 Cushing Ave., Boston, MA 02125.
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and atria of the lateral ventricles bilaterally. The lateral ventricular wall to hemispheric width rado at the level of the posterior horn measured 65% at the point of maximal dilatation (normal values 26% to 36%). The frontal horns appeared appropriate in size (Fig. 1). The third ventricle was normally positioned and not enlarged. The choroid plexuses were also normal in size. The transverse cerebellar diameter measured 3.9 cm, appropriate for 32 weeks' gestation. Attempts to visualize the entire corpus callosum on sagittal and coronal views failed to demonstrate the splenium. A diagnosis of partial (posterior) agenesis of corpus callosum was made. Because a diagnosis of early hydrocephalus could not be ruled out with certainty, repeat ultrasound evaluations were carried out at 35 and 37.5 weeks' gestation, with no change in the intracranial findings. The patient underwent amniocentesis at 38.5 weeks' gestation to confirm pulmonic maturity and subsequently underwent a successful repeat cesarean section, trial of labor having been declined. A normal-appearing female infant was delivered who weighed 3050 gm, with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. Neurologic assessment failed to identify abnormalities. A computed tomography scan and cranial ultrasound confirmed absence of the posterior two thirds of the corpus callosum occipital and temporal horn dilation and minimal upward displacement of the roof of the third ventricle (Fig. 2). No other significant intracranial abnormalities were noted.
Comment The callosal structures form in a rostral to caudal fashion, completing their development by approximately 17 weeks' gestation. Therefore, when partial agenesis occurs, it usually involves the posterior-caudal segment; the splenium is absent, but the anterior callosal structures (rostrum and genu) are preserved. Prenatal recognition of complete agenesis of the corpus callosum has only recently been accomplished.' This diagnosis is readily made on transverse scan by the
Partial agenesis of corpus callosum
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Fig. 1. Transverse section of fetal head above the level of the thalami at 32 weeks' gestation demonstrates discrete enlargement of posterior horns of both lateral ventricles (small arrows). Frontal horns are not dilated but are laterally displaced (long arrows). The third ventricle is not seen at this level, as would be found in complete agenesis of the corpus callosum.
findings of superior displacement and enlargement of the third ventricle, lateral displacement of the frontal horns with a concave appearance to their medial border, and dilation of the posterior horns of the lateral ventricles. Views in the coronal and sagittal planes demonstrate an absence of the characteristic echo-spared structure delineated superiorly by the echogenic pericallosal cistern and inferiorly by the cavum septi pellucidi, cavum vergae, and the third ventricle. In posterior agenesis of the corpus callosum, these findings are not so evident. Superior displacement and enlargement of the third ventricle are either absent or less recognizable. There is less lateral displacement of the frontal horns, while the posterior horns of the lateral ventricles remain significantly dilated. The significance of agenesis of the corpus callosum is poorly understood. In 1957, Slager et al.2 reported their neuropathologic experience and reviewed the world's literature of agenesis of the corpus callosum. They concluded that "the function of the corpus callosum is apparently such that an adult can well live without this structure, compensating for its absence and living a perfectly normal life, with normal intelligence and motor performance." They postulated that coexisting neurologic abnormalities were due to anomalies associated with agenesis of the corpus callosum. In fact, partial or complete agenesis of the corpus callosum is frequently associated with other central nervous system abnormalties in psychologic and autopsy series. However, ascertainment bias probably results in gross overestimation of the prevalence. Specific associated defects include interhemispheric cysts, Dandy-Walker malfor-
Fig. 2. Neonatal computed tomography scan taken at same level as in Fig. I. Asymmetry of the enlarged posterior horns is due to a slightly oblique cut.
mations, Arnold-Chiari type II malformations, encephaloceles, and neurofibromas.' In addition, agenesis of corpus callosum can be found in a number of well-defined syndromes, including trisomies 13 and 18, Shapiro syndrome, Rubenstein-Taybi syndrome,
Lockwood et al.
acrocallosal syndrome, Aicardi syndrome, and Andermann syndrome.' It is therefore imperative that a detailed assessment of the fetal anatomy be carried out. Chromosomal evaluation may not be indicated unless other anomalies or growth retardation is present. Posterior ventriculomegaly, the most prominent finding of this condition, must be differentiated from early hydrocephalus. This latter condition is usually associated with involution of the choroid plexuses and a worsening of ventricular dilation over time. The finding of persistent posterior ventriculomegaly should also be differentiated from biltaeral porencephalic cysts. The importance of the accurate diagnosis of isolated
July 1988 Am J Obstet Gynecol
posterior agenesis of the corpus callosum is related to its benign prognosis. In fact, once associated central nervous system anomalies are excluded, the parents may be reassured and unnecessary obstetric intervention avoided. REFERENCES I. Comstock CH, Culp D, Gonzalez J, et al. Agenesis of the
corpus callosum in the fetus: Its evolution and significance. J Ultrasound Med 1985;4:613. 2. Slager UT, Kelly AB, Wagner JA. Congenital absence of the corpus callosum. Report of a case and review of the literature. N Engl J Med 1957;256: 1171.
Low serum a-fetoprotein level and sex chromosome monosomy York E. Winston, MD, E. O. Horger III, MD, and J. Peter Van Dorsten, MD Charleston, South Carolina A case of 45,X karyotype in association with low maternal serum a-fetoprotein levels is reported. Previous cases of trisomy have been linked to low a-fetoprotein levels. Cases of sex chromosome aneuploidy may be included in the group of aneuploidies with low levels of maternal serum a-fetoprotein. (AM J OssrET GYNECOL 1988;159:186-7.)
Key words: Low maternal serum cx-fetoprotein level, trisomy, aneuploidy
Multiple reports have confirmed the association between low maternal serum cx-fetoprotein levels and fetal chromosomal trisomies. As routine maternal serum cx-fetoprotein screening has become universal, a marked increase has been noted in referrals for genetic amniocentesis because of low maternal serum cx-fetoprotein levels. We recently discovered a fetal sex chromosome monosomy in a pregnant woman referred for amniocentesis because of a low maternal serum cx-fetoprotein level.
the median) at 16 weeks' gestation and 11.5 ng/ml (0.30 multiples of the median) at 17 weeks. Ultrasound examination at 19 weeks' gestation showed bilateral cystic hygromata, fetal ascites, and pleural effusion. The cx-fetoprotein level in the amniotic fluid was found to be 6.9 µg/ml (normal 4.1 to 19.6 µg/ml). Chromosome analysis revealed a karyotype of 45,X. After counseling, the patient elected pregnancy termination. The 45,X karyotype of the abortus was confirmed.
Case report The patient is a 24-year-old white primigravidous woman with a negative family history and no risk factors for inherited disorders. Maternal serum cx-fetoprotein levels were 11.4 ng/ml (0.34 multiples of
Merkatz et al. 1 first noted an association between low maternal serum cx-fetoprotein levels and autosomal trisomies. They reported 44 cases of chromosomal aneu ploidy with maternal serum cx-fetoprotein levels below the median not only in 28 of 32 cases of fetal autosomal trisomy, but also in 7 of 12 cases of sex chromosome aneuploidy. In a recent retrospective study, Doran et al.2 concluded that 5% of screened patients had maternal serum cx-fetoprotein levels <0.5 multiples of the median, and that the risk of trisomy in these patients was I: 180. The reason for low maternal serum cx-fetoprotein
From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Medical University of South Carolina. Received for publication November 4, 1987; accepted December 29, 1987. Reprint requests: York E. Winston, MD, Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC 29425.
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Comment
Key words: Agenesis of corpus callosum, ventriculomegally, prenatal diagnosis, ultrasound
The prenatal diagnosis of partial agenesis of the corpus callosum has not, to our knowledge, been reported in the world's literature. Because this anomaly is not rare and represents a benign cause of ventriculomegaly, its accurate diagnosis is important. Antenatal diagnosis in the present case allowed for parental reassurance and appropriate, noninvasive perinatal care.
Case report A 28-year-old woman (gravida, 3, para 1) underwent an initial ultrasound examination at 18 weeks' gestation that confirmed the gestationa~ age and noted no fetal malformations. A repeat ultrasound at 30 weeks' gestation to assess fetal growth identified "fetal hydrocephalus." The patient was then referred to the Yale Perinatal Unit. The patient's past medical history was noncontributory. There was no family history of neural tube defects, hydrocephalus, or other congenital neurologic abnormalities. The patient denied alcohol, drug, tobacco, or toxin exposure. Sonographic evaluation revealed a live singleton fetus in cephalic lie with a posterior placenta (grade 1) and a normal amount of amniotic fluid. Biometric data were consistent with 32 weeks' gestation and estimated fetal weight was in the 50th percentile. Stomach, bladder, kidneys, abdominal wall, extremities, face, and spine appeared normal. Evaluation of the cranial anatomy demonstrated a biparietal diameter of 7.9 cm (consistent with 32 weeks' gestation), a cephalic index of 80.6%, and a cephalic circumference of 28. 7 cm, all within normal limits. There was discrete enlargement of the posterior horns From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, and the Department of Neonatology and Newborn Medicine, Winthrop-University Hospital, University of New York at Stony Brook School of Medicine, Mineola. Received for publication May 6, 1987; accepted November 16, 1987. Reprint requests: Charles Lockwood, MD, Department of Obstetrics and Gynecology, St. Margaret's Hospital, 90 Cushing Ave., Boston, MA 02125.
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and atria of the lateral ventricles bilaterally. The lateral ventricular wall to hemispheric width rado at the level of the posterior horn measured 65% at the point of maximal dilatation (normal values 26% to 36%). The frontal horns appeared appropriate in size (Fig. 1). The third ventricle was normally positioned and not enlarged. The choroid plexuses were also normal in size. The transverse cerebellar diameter measured 3.9 cm, appropriate for 32 weeks' gestation. Attempts to visualize the entire corpus callosum on sagittal and coronal views failed to demonstrate the splenium. A diagnosis of partial (posterior) agenesis of corpus callosum was made. Because a diagnosis of early hydrocephalus could not be ruled out with certainty, repeat ultrasound evaluations were carried out at 35 and 37.5 weeks' gestation, with no change in the intracranial findings. The patient underwent amniocentesis at 38.5 weeks' gestation to confirm pulmonic maturity and subsequently underwent a successful repeat cesarean section, trial of labor having been declined. A normal-appearing female infant was delivered who weighed 3050 gm, with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. Neurologic assessment failed to identify abnormalities. A computed tomography scan and cranial ultrasound confirmed absence of the posterior two thirds of the corpus callosum occipital and temporal horn dilation and minimal upward displacement of the roof of the third ventricle (Fig. 2). No other significant intracranial abnormalities were noted.
Comment The callosal structures form in a rostral to caudal fashion, completing their development by approximately 17 weeks' gestation. Therefore, when partial agenesis occurs, it usually involves the posterior-caudal segment; the splenium is absent, but the anterior callosal structures (rostrum and genu) are preserved. Prenatal recognition of complete agenesis of the corpus callosum has only recently been accomplished.' This diagnosis is readily made on transverse scan by the
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Volume 159 Number I
185
Fig. 1. Transverse section of fetal head above the level of the thalami at 32 weeks' gestation demonstrates discrete enlargement of posterior horns of both lateral ventricles (small arrows). Frontal horns are not dilated but are laterally displaced (long arrows). The third ventricle is not seen at this level, as would be found in complete agenesis of the corpus callosum.
findings of superior displacement and enlargement of the third ventricle, lateral displacement of the frontal horns with a concave appearance to their medial border, and dilation of the posterior horns of the lateral ventricles. Views in the coronal and sagittal planes demonstrate an absence of the characteristic echo-spared structure delineated superiorly by the echogenic pericallosal cistern and inferiorly by the cavum septi pellucidi, cavum vergae, and the third ventricle. In posterior agenesis of the corpus callosum, these findings are not so evident. Superior displacement and enlargement of the third ventricle are either absent or less recognizable. There is less lateral displacement of the frontal horns, while the posterior horns of the lateral ventricles remain significantly dilated. The significance of agenesis of the corpus callosum is poorly understood. In 1957, Slager et al.2 reported their neuropathologic experience and reviewed the world's literature of agenesis of the corpus callosum. They concluded that "the function of the corpus callosum is apparently such that an adult can well live without this structure, compensating for its absence and living a perfectly normal life, with normal intelligence and motor performance." They postulated that coexisting neurologic abnormalities were due to anomalies associated with agenesis of the corpus callosum. In fact, partial or complete agenesis of the corpus callosum is frequently associated with other central nervous system abnormalties in psychologic and autopsy series. However, ascertainment bias probably results in gross overestimation of the prevalence. Specific associated defects include interhemispheric cysts, Dandy-Walker malfor-
Fig. 2. Neonatal computed tomography scan taken at same level as in Fig. I. Asymmetry of the enlarged posterior horns is due to a slightly oblique cut.
mations, Arnold-Chiari type II malformations, encephaloceles, and neurofibromas.' In addition, agenesis of corpus callosum can be found in a number of well-defined syndromes, including trisomies 13 and 18, Shapiro syndrome, Rubenstein-Taybi syndrome,
Lockwood et al.
acrocallosal syndrome, Aicardi syndrome, and Andermann syndrome.' It is therefore imperative that a detailed assessment of the fetal anatomy be carried out. Chromosomal evaluation may not be indicated unless other anomalies or growth retardation is present. Posterior ventriculomegaly, the most prominent finding of this condition, must be differentiated from early hydrocephalus. This latter condition is usually associated with involution of the choroid plexuses and a worsening of ventricular dilation over time. The finding of persistent posterior ventriculomegaly should also be differentiated from biltaeral porencephalic cysts. The importance of the accurate diagnosis of isolated
July 1988 Am J Obstet Gynecol
posterior agenesis of the corpus callosum is related to its benign prognosis. In fact, once associated central nervous system anomalies are excluded, the parents may be reassured and unnecessary obstetric intervention avoided. REFERENCES I. Comstock CH, Culp D, Gonzalez J, et al. Agenesis of the
corpus callosum in the fetus: Its evolution and significance. J Ultrasound Med 1985;4:613. 2. Slager UT, Kelly AB, Wagner JA. Congenital absence of the corpus callosum. Report of a case and review of the literature. N Engl J Med 1957;256: 1171.
Low serum a-fetoprotein level and sex chromosome monosomy York E. Winston, MD, E. O. Horger III, MD, and J. Peter Van Dorsten, MD Charleston, South Carolina A case of 45,X karyotype in association with low maternal serum a-fetoprotein levels is reported. Previous cases of trisomy have been linked to low a-fetoprotein levels. Cases of sex chromosome aneuploidy may be included in the group of aneuploidies with low levels of maternal serum a-fetoprotein. (AM J OssrET GYNECOL 1988;159:186-7.)
Key words: Low maternal serum cx-fetoprotein level, trisomy, aneuploidy
Multiple reports have confirmed the association between low maternal serum cx-fetoprotein levels and fetal chromosomal trisomies. As routine maternal serum cx-fetoprotein screening has become universal, a marked increase has been noted in referrals for genetic amniocentesis because of low maternal serum cx-fetoprotein levels. We recently discovered a fetal sex chromosome monosomy in a pregnant woman referred for amniocentesis because of a low maternal serum cx-fetoprotein level.
the median) at 16 weeks' gestation and 11.5 ng/ml (0.30 multiples of the median) at 17 weeks. Ultrasound examination at 19 weeks' gestation showed bilateral cystic hygromata, fetal ascites, and pleural effusion. The cx-fetoprotein level in the amniotic fluid was found to be 6.9 µg/ml (normal 4.1 to 19.6 µg/ml). Chromosome analysis revealed a karyotype of 45,X. After counseling, the patient elected pregnancy termination. The 45,X karyotype of the abortus was confirmed.
Case report The patient is a 24-year-old white primigravidous woman with a negative family history and no risk factors for inherited disorders. Maternal serum cx-fetoprotein levels were 11.4 ng/ml (0.34 multiples of
Merkatz et al. 1 first noted an association between low maternal serum cx-fetoprotein levels and autosomal trisomies. They reported 44 cases of chromosomal aneu ploidy with maternal serum cx-fetoprotein levels below the median not only in 28 of 32 cases of fetal autosomal trisomy, but also in 7 of 12 cases of sex chromosome aneuploidy. In a recent retrospective study, Doran et al.2 concluded that 5% of screened patients had maternal serum cx-fetoprotein levels <0.5 multiples of the median, and that the risk of trisomy in these patients was I: 180. The reason for low maternal serum cx-fetoprotein
From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Medical University of South Carolina. Received for publication November 4, 1987; accepted December 29, 1987. Reprint requests: York E. Winston, MD, Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC 29425.
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Comment