Prenatal diagnosis of open spina bifida by MRI and ultrasonography

Prenatal diagnosis of open spina bifida by MRI and ultrasonography
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  Brain & Development, 15 (1993) 75 78 0387-7604/93/ 06.00 ~ 1993 Elsevier Science Publishers B.V. All rights reserved BRADEV 00005 Prenatal diagnosis of open spina bifida by MRI and ultrasonography Toshinori Nakahara a, MD, Tohru Uozumi a, MD, Shuji Monden a, MD, Zainal Muttaqin a, MD, Kaoru Kurisu a, MD, Kazunori Arita a, MD, Satoshi Kuwabara a, MD, Koso Ohama b, MD, Masatoshi Kumagai b, MD and Kyoko Nakahara b, MD Departments of Neurosurgery and bObstetrics and Gynecology, Hiroshima University School of Medicine, Hiroshima, Japan Received 7 September 1992; accepted 6 October 1992 A case that was diagnosed prenatally as having open spina bifida by magnetic resonance imaging (MRI) and ultrasound (US) examination is reported. At the time of the third US examination, the spina bifida cystica was detected, but it could not be determined by US whether it was open or closed spina bifida. A lumbosacral skin defect was detected on MRI, which permitted prenatal diagnosis of open spina bifida. Surgical repair was performed immediately after delivery. Prenatal intrauterine evaluation of the fetal CNS morphology and malformation has advanced with the improvement of diagnostic tools. Each diagnostic tool, however, has its own advantages and disadvantages. In prenatal intrauterine evaluation, it is important that observation be made through the combined use of multiple diagnostic tools. Key words: Spina bifida; Prenatal diagnosis; Magnetic resonance imaging; Ultrasound INTRODUCTION Marked improvement and development of radio- graphic technology now permits prenatal diagnosis of anomalies of the fetal central nervous system (CNS). A case is presented that was diagnosed prenatally as having open spina bifida (OSB) by means of magnetic resonance imaging (MRI) and ultrasound (US) exami- nation, and that underwent surgical repair immediately after delivery. CASE REPORT Ventriculomegaly of the fetus was indicated in a 28- year-old female by US at 34 weeks gestation, and so she was referred to the Department of Obstetrics and Gy- necology, Hiroshima University Hospital. At the time of the initial examination, US revealed ventriculomega- ly and oligoamnion, but no other anomalies. There- after, her clinical course was followed at the outpatient clinic by means of US examination. The second US examination conducted at 36 weeks gestation revealed only ventriculomegaly, as with the first examination. The third US examination at 38 weeks gestation Correspondence address: Dr. T. Nakahara, Department of Neuro- surgery, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minami-ku, Hiroshima 734, Japan. showed a defect of the spinous process and a mass le- sion in the lumbosacral region, in addition to ventricu- lomegaly (Fig 1). She was referred to the Department of Neurosurgery where MRI was immediately per- formed. MRI revealed OSB in the lumbosacral region associated with hydrocephalus (Fig 2). Chiari malfor- mation type II was strongly suspected, but confirma- tion could not be made by imaging diagnosis, e-Feto- protein determination could not be performed, because the patient was in the third trimester. In addition, CT was not performed in view of the possible effect of X- rays on the patient and her fetus. Because US did not provide any evidence of cardiopulmonary, genitourin- ary or gastrointestinal anomalies, that would interfere with an early operation, a plan and preparation were made to perform surgical repair for OSB immediately after delivery. A baby girl was born via a normal spon- taneous vaginal delivery after full-term gestation. Her weight at birth was 2,880 g and the Apgar score (5 min) was 9. There was a midline lumbosacral mass measuring 4 x 5 x 2 cm in size without skin, which was confirmed to be a myelomeningocele. On neurological examination, hip flexion was normal, knee extension was normal on the right side but 4/5 on the left side, and dorsal and plantar flexion of the ankles was 0/5 bilaterally. Club feet were observed bilaterally. The functions of the ur- Brain & Development, Vol 15, No 1, 1993 75  j vertebra eye ball lateral ventricle Z mid/ line / ,\ // \ // i~ ~'-. lj B Fig 1. Ultrasonogram. A: a longitudinal section of the fetal spine demonstrated a cystic mass and a defect of the spinous process. B: a transverse scan of the fetal cranium demonstrated ventriculomegaly. inary bladder and rectum were disturbed, but the re- mainder in the general physical examination was not remarkable. The affected site of the spinal cord was L5 on the right side and L4 on the left side. Surgical repair was conducted within 4 h after delivery. Chiari malfor- mation type II was confirmed on the 7th day after birth by MRI (Fig 3). DISCUSSION The incidence of spina bifida (SB) in Japan is 0.05 , which is lower than in Europe and America. However, SB occupies a very important place among anomalies of the CNS. Prenatal diagnosis of CNS anomalies pro- vides adequate time for the parents to consult with ob- stetricians, neonatologists and neurosurgeons, and is thus useful in determining whether therapeutic abor- tion should be performed in early pregnancy (within the legal limit of 22 weeks of gestation in Japan), and in determining the time of surgical intervention in late pregnancy. During early pregnancy, ~-fetoprotein ana- lysis in combination with US examination is chiefly employed as a diagnostic procedure [1], while during late pregnancy, such radiographical diagnostic proce- 76 Brain & Development, Vol 15, No l, 1993  Fig 2. MRI shows the skin defect and mass lesion in the lumbosacral region. A: sagittal Tt-weighted MRI. B: sagittal T2-weighted MRI. dures as CT, MRI and US are used. Selective surgery for SB was advocated in the 1970s [2,3], but at the pre- sent time, surgical repair immediately after birth is re- commended [4]. SB can be broadly classified into open spina bifida (OSB) without skin, and closed spina bifi- da (CSB), covered with skin. When considering the time of operation, it is important to determine whether the SB is OSB or CSB. In the case of OSB, early surgi- cal repair within 24 h after birth should be performed for the purposes of preventing infection and drying of the nerve tissues so that deterioration of the neurologi- cal function can be avoided. Prenatal intrauterine evaluation of the fetal CNS morphology and malformation has made remarkable advances with the development and improvement of diagnostic tools. Each diagnostic tool has its own ad- vantages and disadvantages. US is a superior method of examination, being simple and reproducible, and is thus useful as a screening test for evaluating bone and Fig 3. Sagittal T~-weighted MRI showed a herniated medulla oblon- gata, an elongated and beaked tectum, and hypogenesis of the cere- bellum. Brain & Development, Vol 15, No 1, 1993 77  mass lesions in the vertebra and cranium [5,6], but it is not uncommon that evaluation cannot be made by US as to whether the lesion is OSB or CSB [7]. In addition, the accuracy is 70 and elevation of diagnostic accu- racy requires a skilled specialist [8]. MRI is useful for evaluating the brain parenchyma and skin morphology, but is inferior for evaluating the vertebra and cranium. The effects of muscle relaxants to inhibit the artifacts due to fetal motion have posed a problem, but in the third trimester when the fetal cranium is fixed in the maternal pelvis, MRI can be conducted safely, without the administration of muscle relaxants, to obtain good pictures of the fetal intracranial structure [9]. In the present case, by means of US, the defect of the spinal process and the mass lesion in the lumbosacral region could be detected, permitting diagnosis of spina bifida cystica. However, it was not possible to ascertain whe- ther the mass lesion was covered with skin or not. MR1 was conducted to compensate for this weakness of US, but MRI could not detect the defects of the spinal pro- cess and spinal cord. The diagnosis of OSB could be made from the finding of a defect of the lumbosacral skin. On intrauterine evaluation of a CNS anomaly, when an anomaly is suspected with US used as a screening examination, it is important that a combina- tion of other diagnostic procedures be employed to es- tablish an accurate diagnosis. For the prenatal diagnosis of a CNS anomaly, it is always necessary to bear in mind the potential pre- sence of other anomalies. The frequency at which hy- drocephalus is accompanied by other CNS anomalies is 85 , SB being the most common [10]. When hydroce- phalus is accompanied by SB, Chiari malformation type II should be suspected. When fetal hydrocephalus is suspected, scrupulous and careful evaluation should be performed for other anomalies using multiple diag- nostic tools, including US. CONCLUSION When a CNS anomaly is suspected in a screening ex- amination, it is important (i) to be well acquainted with the diagnostic potential of each diagnostic tool, (ii) to make the diagnosis with the combined use of other diagnostic methods, and (iii) to perform scrupulous and careful evaluation regarding other possible associ- ated anomalies. REFERENCES 1. UK collaborative study on alpha-fetoprotein in relation to neural tube defects. Maternal serum-~-fetoprotein measurement in an- tenatal screening for anencephaly and spina bifida in early preg- nancy. Lancet 1977; i: I323 32. 2. Lorber J. Results of treatment of myelomeningocele: an analysis of 524 unselected cases, with special reference to possible selec- tion of treatment. Dev Med Chiht Neurol 1971; 13:279 303. 3. Stein S, Schut L, Ames M. Selection for early treatment in mye- lomeningocele: a retrospective analysis of various selection proce- dures. Pediatrics 1974: 54:553 7. 4. Soare P, Raimondi A. Intellectual and perceptual-motor charac- teristics of treated myelomeningocele children. Am J Di.s Chiht 1977; 131:199 204. 5. Filly R, Simpson G, Linlowski G. Fetal spine morphology and maturation during the second trimester. J Ultrasound Med 1987; 6:63 6. 6. Nyberg D, Mack L, Hirsch J, Pagon R, Shepard T. Fetal hydro- cephalus: sonographic detection and clinical significance associ- ated anomalies. Radioh~gy 163; 163:187 91. 7. Oi S, Tamaki N. Matumoto S, Katayama K, Mochizuki M. Morphological evaluation of fetus CNS and its related anoma- lies: the advantages and limitations of prenatal diagnosis by means of MRI-US. CT (in Japanese). CT Kenkyu (Kanot /i) 1989; I1:413 20. 8, Roberts C, Evans K, Hibbard B. Laurence K, Roberts E, Ro- bertson 1. Diagnostic effectiveness of ultrasound in detection of neural tube defect. Lancet 1983; ii: 1068 9. 9. Morimoto K, Hayakawa T, Takagi T, et al. Prenatal diagnosis and early neonatal surgery of central nervous system anomalies (in Japanese). CT Kenkyu (Kanot /i) 1992; 13:521 6. 10. Chervenak F. Berkowitz R. Tortora M, Hobbins J. The manage- ment of fetal hydrocephalus. Am J Obstet Gynecol 1985; 151: 933 42. 78 Brai~t & l)evelopmenl, Vol 15, No l. 1993
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