reproductive medicine Case Report Pushing the Limits of Prenatal Ultrasound: A Case of Dorsal Dermal Sinus Associated with an Overt Arnold–Chiari Malformation and a 3q Duplication Olivier Leroij 1, Lennart Van der Veeken 2,*, Bettina Blaumeiser 3 and Katrien Janssens 3 1 Faculty of Medicine, University of Antwerp, 2610 Wilrijk, Belgium; [email protected] 2 Department of Obstetrics and Gynaecology, University Hospital Antwerp, 2650 Edegem, Belgium 3 Department of Medical Genetics, University Hospital and University of Antwerp, 2650 Edegem, Belgium; [email protected] (B.B.); [email protected] (K.J.) * Correspondence: [email protected] Abstract: We present a case of a fetus with cranial abnormalities typical of open spina bifida but with an intact spine shown on both ultrasound and fetal MRI. Expert ultrasound examination revealed a very small tract between the spine and the skin, and a postmortem examination confirmed the diagnosis of a dorsal dermal sinus. Genetic analysis found a mosaic 3q23q27 duplication in the form of a marker chromosome. This case emphasizes that meticulous prenatal ultrasound examination has the potential to diagnose even closed subtypes of neural tube defects. Furthermore, with cerebral anomalies suggesting a spina bifida, other imaging techniques together with genetic tests and measurement of alpha-fetoprotein in the amniotic fluid should be performed. Citation: Leroij, O.; Van der Veeken, Keywords: dorsal dermal sinus; Arnold–Chiari anomaly; 3q23q27 duplication; mosaic; marker chro- L.; Blaumeiser, B.; Janssens, K. mosome Pushing the Limits of Prenatal Ultrasound: A Case of Dorsal Dermal Sinus Associated with an Overt Arnold–Chiari Malformation and a 3q 1. Introduction Duplication. Reprod. Med. 2021, 2, Neural tube defects are the most common central nervous system anomaly. 118–124. https://doi.org/10.3390/ Two major types are distinguished: the open spina bifida aperta and closed spina bi- reprodmed2030012 fida occulta. Open spina bifida lesions are usually diagnosed prenatally by means of an ultrasound based on the characteristic brain abnormalities: the lemon-sign, which reflects Academic Editor: Berthold Huppertz the abnormal skull shape, and the banana-sign, reflecting the abnormal cerebellar shape. Furthermore, in open spina bifida, a dorsal sac (myelomeningocele) or missing processi Received: 10 May 2021 spinosi can easily be detected on ultrasound, which confirms the diagnosis. Closed spina Accepted: 16 June 2021 Published: 9 July 2021 bifida lesions are usually more difficult to diagnose based on prenatal ultrasound because of the absence of cranial abnormalities. The diagnosis can still be made if the lesion is Publisher’s Note: MDPI stays neutral characterized by a skin-covered sac (meningocele). However, certain subtypes of closed with regard to jurisdictional claims in spina bifida are more subtle and are, therefore, often missed during prenatal ultrasound. published maps and institutional affil- Dorsal dermal sinuses are one of the subtypes of closed spina bifida lesions. These lesions iations. are characterised by an epithelial-lined tract that connects the skin surface with the intra- canalicular space. Due to the absence of secondary cranial abnormalities, as found in open spina bifida lesions, and the absence of cysts or masses at the spine, these lesions are usually missed during prenatal ultrasound screening. Alfa-fetoprotein levels in amniotic fluid can be measured to help to find the diagnosis. If there is leakage of spinal fluid, these levels Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. will rise. This technique is presently rarely performed; however, in difficult or atypical This article is an open access article cases, it can still assist in confirming the diagnosis. We present a case of a fetus with cranial distributed under the terms and abnormalities typical of open spina bifida but with an intact spine on ultrasound and fetal conditions of the Creative Commons MRI. Here, we want to demonstrate that even in closed spina bifida, cranial abnormalities Attribution (CC BY) license (https:// can be present. Furthermore, when cranial abnormalities are detected during prenatal creativecommons.org/licenses/by/ ultrasound but the spine appears to be intact, alfa-fetoprotein remains a powerful tool to 4.0/). help diagnose prenatal atypical spina bifida cases. Reprod. Med. 2021, 2, 118–124. https://doi.org/10.3390/reprodmed2030012 https://www.mdpi.com/journal/reprodmed Reprod. Med. 2021, 2, FOR PEER REVIEW 2 prenatal ultrasound but the spine appears to be intact, alfa-fetoprotein remains a powerful tool to help diagnose prenatal atypical spina bifida cases. Reprod. Med. 2021, 2 2. Case Presentation 119 A 27-year-old primigravida was referred to the outpatient clinic of our hospital at a gestational age (GA) of 17 + 3 weeks following detection of a fetal unilateral hydronephro- 2.sis Case by Presentationthe peripheral gynecologist. Ultrasonography demonstrated a duplex collecting systemA 27-year-old in the left primigravida kidney with was hydronephrosis referred to the of outpatient the cranial clinic pole, of our moderate hospital dilatation at a of gestationalthe upper agepole (GA) uret ofer 17, and + 3 weeksmild dilatation following detectionof the lower of a fetalpole unilateralureter. The hydronephro- cerebellum at that sistime by showed the peripheral a minimal gynecologist. posterior Ultrasonography curving (Figure demonstrated 1), but no distinct a duplex banana collecting-sign. Inspec- systemtion of inthe the spine left was kidney inconspicuous. with hydronephrosis The patient of the was cranial reevaluated pole, moderate in our center dilatation at 24 weeks ofGA the. The upper hydronephrosis pole ureter, and of mild the upper dilatation pole of of the the lower left polekidney ureter. remained The cerebellum stable. However, at that time showed a minimal posterior curving (Figure1), but no distinct banana-sign. the cerebellum presented a banana-shape with herniation of the hindbrain onto C2 and Inspection of the spine was inconspicuous. The patient was reevaluated in our center at 24minimal weeks GA.lemon The-sign hydronephrosis of the skull of(Figure the upper 2). The pole lateral of the leftventricles kidney remainedwere not stable.dilated. Ultra- However,sound examination the cerebellum of the presented spine arevealed banana-shape a closed with skin herniation except of for the a hindbrainminimal ontofistula in the C2sacro and-coccygeal minimal lemon-sign region (Figure of thes skull 3–5). (Figure Furthermore,2). The lateral an abnormal ventricles weregap between not dilated. the second Ultrasoundand third digit examination was seen of on the both spine hands revealed as awell closed as a skin syndactyly except for between a minimal the fistula first and sec- inond the toe. sacro-coccygeal Cardiac sonography region (Figures was3 normal–5). Furthermore, at both 17 an- abnormaland 24-weeks gap between GA, with the a normal secondfour-chamber and third view, digit was outflow seen on tracts both hands, and asthree well-vessel as a syndactyly view. An between amniocentesis the first and was per- secondformed toe. to Cardiacrule out sonography genetic anomalies was normal and at bothto measure 17- and 24-weeksalfa 1-fetoprotein. GA, with a normalAdditionally, a four-chamber view, outflow tracts, and three-vessel view. An amniocentesis was performed fetal MRI was carried out mainly to assess the fetal spine, as the cerebral findings all indi- to rule out genetic anomalies and to measure alfa 1-fetoprotein. Additionally, a fetal MRI wascated carried the outpresence mainly of to assessan op theen fetalneural spine, tube as thedefect. cerebral MRI findings analysis all indicated confirmed the the hy- presencedroureteronephrosis of an open neural as tubewell defect. as the MRI lemon analysis-shaped confirmed skull, the Arnold hydroureteronephrosis–Chiari malformation as11mm well asbelow the lemon-shaped the foramen skull, magnum, Arnold–Chiari absent malformationcerebrospinal 11mm fluid below around the foramenthe cerebellum, magnum,and possible absent mild cerebrospinal tethering fluidof the around cord. the However, cerebellum, MRI and failed possible to milddemonstrate tethering an open ofspina the cord. bifida However, or any MRIskin faileddefects. to demonstrateThe Alfa 1- anfetoprotein open spina was bifida elevated, or any skinfurther defects. reinforcing Thethe Alfaassumption 1-fetoprotein of a classic was elevated, spina bifida. further QF reinforcing-PCR showed the assumption no aneuploidy of a classic for chromosomes spina bifida.13,18, QF-PCR21, X, or showed Y, but SNP no aneuploidy array demonstrated for chromosomes a terminal 13, 18, multiplication 21, X, or Y, but SNP of approximately array demonstrated a terminal multiplication of approximately 56 Mb of the long arm (3q23qter) 56 Mb of the long arm (3q24-qter) of chromosome 3: arr 3q23q29 (141903905–197845233) × of chromosome 3: arr 3q23q29(141903905-197845233)x2~4. The nature of the multiplication 2~4. The nature of the multiplication could not be deduced. Interphase FISH with probes could not be deduced. Interphase FISH with probes in chromosomal regions 3q26 and 3q27in chromosomal showed 4 copies region of boths 3q26 chromosomal and 3q27 bands showed in approximately 4 copies of 50%both of chromosomal the interphases. bands in Metaphaseapproximately FISH 50% proved of thatthe theinterphases. 2 extra copies Metaphase were located FISH on proved a marker that chromosome.