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ABSTRACT: OBJECTIVE: To assess the presence and degree of indirect signs of corpus callosum agenesis (ACC) by time of gestation. The endpoint is to define in which percentage each sign is already present in a gestational age < 24 weeks. METHODS: Fifty-four cases of ACC undergoing three-dimensional neurosonology at our unit from January 2005 to December 2012 were analysed. A single examination was available in 48 cases, while 6 cases were followed up longitudinally for a total of 69 examinations. The following variables were retrospectively assessed: indication for referral, width of the atrium, colpocephaly, visualization/non-visualization of the cavum septi pellucidi, presence of dorsal cyst, additional CNS and non-CNS anomalies, karyotype. RESULTS: Overall, there were 31 cases of cACC (44 examinations) and 23 cases of pACC (25 examinations). Mean gestational age was lower in the cases referred because of anomalies other than ACC than in those referred because of ventriculomegaly and/or suspicion of ACC (p < 0.05). Atrial width showed a positive linear correlation with advancing gestational age (p < 0.0001); it was < 10.0 mm in 25/34 (73.5%) < 24 gestational weeks and in 9/35 (25.7%) cases beyond 23 weeks (P < 0.001). Colpocephaly was present in 20.6% (7/34) of cases < 24 weeks of gestation and in 68.6% (24/35) of cases after 23 weeks (P < 0.05). The cavum septi pellucidi was present at least in part and visible in 17/25 (68%) of pACC cases. In 9/25 (36.0%) cases of pACC, there was nor ventriculomegaly nor absence of the cavum septi pellucidi. Associated anomalies were present in 25/54 (46.3%) cases, and in 11 cases these included or consisted of CNS abnormalities. Karyotype was abnormal in 7/40 (17.5%) cases in which it was available. CONCLUSIONS: Most of the indirect signs of ACC are either absent or barely visible at the time of the midtrimester screening ultrasound in a significant proportion of cases. Therefore, ACC may escape diagnosis at midtrimester screening ultrasound. In particular, pACC may not show any abnormality of the trans-ventricular screening view < 24 gestational weeks in 43.5% of cases. The medico-legal implications of such findings are important and should be considered.
Ultrasound in Obstetrics and Gynecology 05/2013; · 3.56 Impact Factor
Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 02/2012; 31(2):337-9. · 1.40 Impact Factor
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ABSTRACT: To review the normal and pathological development of the posterior membranous area (PMA) in the fetal brain, to define sonographic criteria with which to diagnose a Blake's pouch cyst (BPC) in the fetus and to review the ultrasound features, associations and outcome of 19 cases of BPC seen at our center over the last 5 years.
We conducted a MEDLINE search using the terms 'Blake's pouch', with or without 'fourth ventricle' or '4(th) ventricle', with or without 'roof' and identified articles describing normal and/or abnormal development of the PMA, whether or not they were cited in the limited clinical literature on BPC. A description of the normal and abnormal development of BPC was derived by collating these articles. The clinical retrospective study included 19 cases of posterior fossa anomalies with a final diagnosis of BPC seen at our institution. The following variables were assessed: referral indication, gestational age at diagnosis, ultrasound and magnetic resonance imaging (MRI) findings, associated anomalies, natural history and pregnancy and neonatal outcome. A transvaginal three-dimensional (3D) ultrasound examination was performed in all cases and 15 cases underwent MRI. To confirm the diagnosis, postnatal MRI, transfontanellar ultrasound or autopsy were available in all cases.
Among the 19 cases reviewed, referral indications were: suspicion of vermian abnormality in 11 (58%) cases and other non-central nervous system anomaly in eight (42%) cases. Sonographically, all cases showed the following three signs: 1) normal anatomy and size of the vermis; 2) mild/moderate anti-clockwise rotation of the vermis; 3) normal size of the cisterna magna. On 3D ultrasound, the upper wall of the cyst was clearly visible in 11/19 cases, with choroid plexuses on the superolateral margin of the cyst roof. On follow-up, the BPC had disappeared by 24-26 gestational weeks in six of the 11 cases which did not undergo termination of pregnancy (TOP), and remained unaltered until birth in the other five cases. There were associated anomalies in eight (42%) cases, in five of which this consisted of or included congenital heart disease. Karyotype was available in 14 cases, two of which were abnormal (both trisomy 21). Regarding pregnancy outcome, there were eight (42%) TOPs, two (10%) neonatal deaths and nine (48%) survivors. One neonate, in whom the BPC had disappeared by the time of birth, had obstructive hydrocephaly confirmed. Another neonate was diagnosed with Down syndrome after birth. Excluding the Down syndrome baby, neurodevelopmental outcome was normal at the time of writing in all eight cases.
Based on our analysis of ultrasound features, we propose that for BPC to be diagnosed in a fetus the following three criteria should be fulfilled: 1) normal anatomy and size of the vermis; 2) mild/moderate anti-clockwise rotation of the vermis; 3) normal size of the cisterna magna. Furthermore, we found that BPC can undergo delayed fenestration at 24-26 weeks in more than 50% of cases. Finally, it seems that BPC shows a risk of association with extracardiac anomalies (heart defects in particular) and, to a lesser extent, trisomy 21.
Ultrasound in Obstetrics and Gynecology 11/2011; 39(3):279-87. · 3.56 Impact Factor