Prenatal detection of corpus callosum agenesis: the potential of ultrasound. A case report. Seidel, Vera, MD¹; Scherer, Katrin, MD¹; Longardt, Ann Carolin, MD²; Hinkson, Larry, MD¹; Henrich, Wolfgang, MD¹ 1: Department of Obstetrics, Charité University Hospital Berlin, Berlin 13353, Germany 2: Department of Neonatology, Charité University Hospital Berlin, Berlin 13353, Germany Context The corpus callosum (CC) is crescent shaped and approximately 10 cm long. It consists of four parts, from anterior to posterior: rostrum, genu, body, splenium. It assumes its final shape by 18-20 weeks of gestation (Schell-Apacik et al. 2008), thus imaging of the structure is advised not to be performed before 20 weeks of gestation (Santo et al. 2012). The assessment of the pericallosal arteries by color Doppler ultrasonography at 11-14 weeks of gestation can be an earlier marker to assess the CC (Diaz-Guerrero et al. 2013). The incidence of corpus callosum agenesis (CCA) is low ranging from 0.03% to 0.7% in the general population. It can either be isolated, be associated to central nervous malformations or be linked to a complex syndrome. Isolated forms are usually associated with a favorable outcome (Sotiriadis and Makrydimas 2012). If CCA with fetal ventriculomegaly is associated with other malformations, a poor outcome is highly probable (Noguchi et al. 2014). The termination rate of pregnancies is 42.4% when CCA is detected (Ozyuncu, 2013). The causes of CCA can be genetic, metabolic or vascular abnormalities, but in most cases the reason is unknown. Case description and Results We present a 25 year-old primigravida, referred with dilatation of the lateral ventricles detected in 20 weeks of gestation. The subsequent examination at our clinic was highly suspicious of CCA because of indirect prenatal ultrasound signs (see figure 1). Further detailed neurosonography and fetal scan did not show other cerebral or extracranial malformations. The mother did not want any invasive genetic testing. The TORCH serology did not show any intrauterine infections. The glucose tolerance test was not indicative of gestational diabetes mellitus. The mother received detailed counseling and chose to continue the pregnancy. Because of increasing head circumference (see table 1) the child was delivered via cesarean section at 37+6 weeks of gestational age. Follow-up care was performed at our tertiary center. The newborn was diagnosed with CCA and internal non-obstructive hydrocephalus (see figure 2). Adducted thumbs syndrome without other neurologic abnormalities was diagnosed. The suspicion of L1CAM syndrome was raised. Confirmation is still pending. Figure 1: 23+6 WG Figure 1: Prenatal sonographic findings upper row: Images from 23+6 WG: symmetric dilatation of the lateral ventricles with colpocephaly, absence of CSP and widening of the interhemispheric fissure. Middle row: Images from 30+5 WG: increasing hydrocephalus and progradient dilatation of the interhemispheric fissure. Lower row: Images from 31+4 WG: increasing hydrocephalus. 30+5 WG Left hemisphere Right hemisphere Biometric measurements WG pLV [mm] pLV/h I BPD [mm] FOD [mm] HC [mm] EW [g] 23+6 13 0,54 14 0,58 61 79 222 552 30+5 28 0,70 0,67 87 113 314 1467 31+4 32 0,72 34 0,77 92 116 327 1677 Table 1: Overview of biometrical measurements within in the course of the pregnancy: Symmetric dilatation of the lateral ventricles with increasing disproportion between hemisphere and pLV. The HC at 23+6 WG correlates with 77th percentile. In the following two examinations the HC correlates with >95th percentile. The AC (results not shown) stays between 15th and 33rd percentile. WG: weeks of gestation, pLV: posterior lateral ventricle, pLV/h I: posterior lateral ventricle/hemispheric index. BPD: biparietal diameter, FOD: fronto-occipital diameter, HC: head circumference, AC: abdominal circumference, FL: femur length. EW: estimated weight according to Hadlock (BPD, HC, AC, FL). 31+4 WG Figure 2: Postnatal ultrasound Postnatal MRI Figure 2: postnatal findings: Left: ultrasound from second day of life confirming CCA and bilateral symmetric dilatation of LV. Right: MRI scan 1 month after birth: CCA and persistent dilatation of the lateral ventricles, no other brain anomalies are detected. Discussion If there is any suspicion of CCA based on the ultrasound examination, fetal MRI is proposed as the better diagnostic tool (Craven et al. 2015). In our case there was a suspicion after detailed ultrasonographic examination. But further information about the diagnosis of CCA would not have influenced her decision to continue the pregnancy. In such cases it is cost- and time-effective not to perform a fetal MRI. The prognosis of CCA is difficult. As in our case prenatally isolated CCA with fetal ventriculomegaly was suspected prenatally, but after birth an additional adducted thumbs syndrome was diagnosed. Long-term follow-up is needed to evaluate the outcome of the case we present. Summary While in-utero MRI has been proposed as the best diagnostic tool when CCA is suspected by prenatal ultrasound, this case report shows the potential of high end ultrasound technology to diagnose and follow up this cerebral malformation. Ultrasound is particularly useful for follow up when parents have decided against termination of pregnancy and further prenatal diagnostic investigations. References Craven et al.: Antenatal diagnosis of agenesis of the corpus callosum. Clin Radiol. 2015 Mar;70(3):248-53. Diaz-Guerrero et al.: Assessment of pericallosal arteries by color Doppler ultrasonography at 11-14 weeks: an early marker of fetal corpus callosum development in normal fetuses and agenesis in cases with chromosomal anomalies. Fetal Diagn Ther. 2013;34(2):85-9. Noguchi et al.: Outcomes of patients with prenatally diagnosed agenesis of the corpus callosum in conjunction with ventriculomegaly. Arch Gynecol Obstet. 2014 Aug;290(2):237-42. Özyüncü et al.: Antenatal diagnosis and outcome of agenesis of corpus callosum: A retrospective review of 33 cases. J Turk Ger Gynecol Assoc. 2014 Mar 1;15(1):18-21. Santo et al.: Counseling in fetal medicine: agenesis of the corpus callosum. Ultrasound Obstet Gynecol. 2012 Nov;40(5):513-21. Schell-Apacik et al.: Agenesis and dysgenesis of the corpus callosum: Clinical, genetic and neuroimaging findings in a series of 41 patients. Am J Med Genet A. 2008 Oct 1;146A(19):2501-11. 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