P14.71: Prenatal diagnosis of diastematomyelia at 15 weeks by 3-D ultrasound

31 August–4 September 2004, Stockholm, Sweden

P14.69 Ultrafast magnetic resonance of the fetal spine – the importance of the extra-axial cerebrospinal fluid space E. Whitby, M. N. Paley, J. Morris, P. D. Griffiths University of Sheffied UK Background: Ultrafast MR of the fetal nervous system is an expanding specialty. The fetal Central nervous system has been the main region of interest but most of this has concentrated on the brain and little on the fetal spine. In our experience we noted that the extra axial cerebrospinal fluid (CSF) space was absent in many of our cases with a myelomeningocele (MMC). Objective: To assess if the absence of extra-axial CSF space is indicative of a myelomeningocele. Method: We reviewed all our cases of spinal MR imaging and assessed the position of the tonsils, amount of extra axial CSF space, morphology and size of the ventricles and compared these to the MR diagnosis. Results: 44 fetal images were reviewed (41 singletons and 3 sets of twins). 21 had MMC, 13 lumbar/sacral, 3 thoracic, 4 sacral and 1 hemimyelomeningocele. 15 had other pathologies, 8 were normal. Of the 21 with MMC, 13 had low cerebellar tonsils and 8 had normally placed tonsils. The 13 with low cerebellar tonsils had NO extra-axial CSF space. All but 3 of the patients with normally placed tonsils had a normal amount of extra-axial CSF. None had low tonsils and a normal CSF space. Absence of the extra-axial CSF space was not seen in any other spinal pathology. The ventricles were abnormal in all cases with low placed tonsils- an angular morphology was seen in 6 cases (46%), moderate disproportionate dilatation was seen in 6 cases (46%) and mild disproportionate dilatation in 1 (8%). All cases with low tonsils and no extra-axial CSF space had ventriculomegaly. The 3 cases with normal tonsils and no extra-axial CSF space had normal sized ventricles (1lumbar sacral MMC, 1 thoracic MMC and 1hemimyelomeningocele with spurious limb growth). Conclusion: Absence of the extra axial CSF space appears to be indicative of a myelomeningocele.

P14.70 Routine assessment of amniotic fluid alpha-fetoprotein in second trimester genetic amniocentesis to detect fetal neural tube defects K. Ferm1 , T. Gottvall1 , E. Dahlen2 , B. Orlenius1 Central Hospital Norrkoping, Sweden, 2 Central Hospital ¨ Jonk Sweden ¨ oping, ¨

1

Objective: The main aim of the study was to evaluate the clinical usefulness of routine assessment of amniotic fluid alpha-fetoprotein (AF-AFP) in second trimester genetic amniocentesis, to detect fetal neural tube defects (NTD). A secondary aim was to survey the routine for analyses of AF-AFP in obstetric clinics in Sweden today. Methods/material: This is a retrospective study. The studied population included all 1919 pregnant women, from the county ¨ ¨ oping, ¨ hospitals of Norrkoping and Jonk who underwent second trimester genetic amniocentesis, during the years 1993–2003. Indications for the genetic amniocentesis were elevated maternal age (> 35 years old) or increased anxiety for chromosomal defects of the expected baby. A questionnaire concerning policy and experience of AF-AFP analyses was sent to all obstetric clinics in Sweden who performed genetic amniocentesis in 2003. Result: Of the 1811 analysis of AF-AFP, eight cases had increased values (0.4%) and five of them were false positive (63%). Of the three true positive cases, one had clinical relevance. In the other two cases the detection of NTD was of subordinate importance; one fetus had trisomy 18 and the other pregnancy was a missed abortion at the ultrasound check-up. In Sweden 91% (39/43) of the obstetric clinics perform routine assessment of AF-AFP at second trimester genetic amniocentesis,

Ultrasound in Obstetrics & Gynecology 2004; 24: 269–372

Poster abstracts

but according to the answers in the questionnaire only 8% of the clinics regarded the analyses useful in clinical practice. During 2003 about 8000 genetic amniocentesis were made in Sweden. Conclusion: We concluded that routine assessment of AF-AFP in second trimester genetic amniocentesis does not appear to be justified. The clinical usefulness seems to be limited, and the result of AF-AFP more often creates parental anxiety.

P14.71 Prenatal diagnosis of diastematomyelia at 15 weeks by 3-D ultrasound S. Maslovitz, A. Jaffa, R. Amster, I. Gull, G. Fait, J. B. Lessing, J. Har-Toov Lis Maternity Hospital, Sourasky Medical Center, Israel Diastematomyelia is a rare structural anomaly of dorso-ventral spinal cord splitting by an osseous or fibrous septum. Prenatal diagnosis of diastematomyelia is usually made during a third trimester ultrasound scan and is based on widening of the interpedicular vertebral space accompanied by interposing echogenic focus. Additionally, fetal MRI may be used to further specify the type of this rare dysraphism. Data on prenatal diagnosis of this occult lesion is scarce and based on few case reports. We present a case of diastematomyelia suspected during early second trimester ultrasound (15 weeks’ gestation) and clearly demonstrated by 3-D imaging but not supported by MRI imaging. Pathological report confirmed the diagnosis of diastematomyelia with a bony spur dividing the cord into two hemicords, an image which was accurately depicted by 3-D scan in early 2nd trimester. We thus report a very early detection of diastematomyelia with the aid of a novel means of diagnosis – the three dimensional ultrasound scan.

P14.72 Combined ultrasound and MRI diagnosis in a novel case of sirenomelia with associated upper limb abnormalities H. Berger, J. Slevin, S. Keating, S. Pantazzi, J. Kingdom, D. Chitayat Mount Sinai Hospital, Canada Sirenomelia is a rare congenital malformation characterized by single or fused lower limbs along with other severe anomalies. Invariably, bilateral renal agenesis is present resulting in severe oligohydramnios. The incidence of this disorder ranges from 1:60000–1:100000 births. As prenatal diagnosis by traditional 2-D ultrasound is hindered by the presence of anhydramnios, the adjunct usage of amnioinfusion or MRI has been advocated. We report the case of a 33 year old G1P0 referred for level II ultrasound due to severe oligohydramnios at 20 weeks of gestation. Ultrasound examination revealed anhydramnios, renal agenesis, small chest, caudal spinal abnormalities and a single femur. Fetal MRI performed at 23 weeks of gestation confirmed the ultrasound findings in addition to identifying flexion deformity of wrists thus raising the suspicion of upper limb abnormalities. Following misoprostol termination of pregnancy at 25 weeks of gestation, autopsy revealed type VI Sirenomelia with bilateral absent radii and thumbs and radial deviation of hands. Additional findings included tracheo-esophageal fistula and imperforate anus with blind-ending rectum. After reviewing nine additional cases of sirenomelia from our institution, we found two cases with upper limb abnormalities: one with unilateral absent thumb and one with bilateral absent radii. There is a debate regarding the etiology of sirenomelia with some suggesting that it is but a variant of the Caudal Regression Syndrome (CRS). Others have noted an association between VACTERL and sirenomelia. The presence of upper limb abnormalities in three of our ten cases would support this association. Alternatively, since two of the cases had the same pattern of upper limb abnormalities

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