2008-Issue1.indd A 30 YEAR OLD MULTIGRAVIDA PRESENTED TO the Gynecology Department of Sultan Qaboos University Hospital, Oman, at 32 weeks pregnancy. Both parents were healthy and the marriage was nonconsanguineous. There was no familyhistory of birth defects. An antenatal ultrasound study, Prenatal MRI Image of a Fetus with Semilobar Holoprosencephaly *Sukhpal Sawhney,1 Lovina Machado,2 Rajeev Jain1 SULTAN QABOOS UNIVERSITY MEDICAL JOURNAL MARCH 2008, VOLUME 8, ISSUE 1, P. 93-94 SULTAN QABOOS UNIVERSITY© SUBMITTED - 2ND JULY 2007 ACCEPTED - 21ST NOVEMBER 2007 I N T E R E S T I N G M E D I C A L I M A G E جنني عند الفصي نصف الدِّماغ مِ دَّ قَ مُ اجُ مَ ِالنْدِ صور الرنني املغناطيسي احلمل أثناء جني راجيف لوفينا ماجادو˛ سخبال سوهني˛ 1Department of Radiology and Molecular Imaging, Sultan Qaboos University Hospital, Muscat, Oman; 2Department of Gynecology and Obstetrics, Sultan Qaboos University Hospital, Muscat, Oman; 3Department of Radiology and Molecular Imaging, Sultan Qaboos University, College of Medi- cine & Health Sciences, Muscat, Oman *To whom correspondence should be addressed. Email: sukh@squ.edu.om 1a. Coronal plane at the level of the thalami: Central horseshoe-shaped single monoventricle (arrows) with absent frontal horns, absent ante- rior midline falx and inter-hemispheric fissure, absent septum pellucidum with failure of cleav- age of frontal and parietal lobes anteriorly; rudi- mentary temporal horns (arrowheads); thalami are partially separated with rudimentary third ventricle (marked *) 1b. Sagittal plane: Corpus callosum (arrow) is absent in the uncleavaged frontal region. Tem- poral horn (arrowhead) is identified. Note the proptosis. Figure 1a: Heavily T2W (HASTE) images in the fetal cranial coronal and sagittal planes. S U K H PA L S AW H N E Y, L O V I N A M A C H A D O A N D R A J E E V J A I N 94 at 32 weeks pregnancy, raised the suspicion of a brain malformation, but it was suboptimal due to maternal habitus. An MRI of the fetus, at 34 weeks pregnancy, demonstrated semilobar holoprosencephaly. The baby was born at term with microcephaly, proptosis, and dysmorphic features. The diagnosis was confirmed by a postnatal computed tomography (CT) scan. C O M M E N T Holoprosencephaly (HP) is a congenital anomaly char- acterized by lack of cleavage of the prosencephalon. Although relatively rare, it is the most common anom- aly that involves both the brain and the face. Prenatal diagnosis of this anomaly using ultrasonography, par- ticularly of the less severe forms, is difficult. Magnetic resonance imaging (MRI) has recently become an im- portant complement to ultrasound in prenatal diagno- sis of central nervous system anomalies.1 HP is the most common anomaly affecting the ven- tral forebrain, occurring in 1/250 embryos and 1/8300- 16,000 live births.2, 3 HP refers to a spectrum of disorders resulting from absent or incomplete cleavage of the forebrain (prosen- cephlon) during early embryologic development (days). HP is usually categorized as alobar, semilobar or lobar depending on the degree of forebrain cleavage. 4 Alo- bar is the most severe form with complete failure of cleavage of the two cerebral hemispheres. It results in a monoventricular cavity; fusion of the thalami; absence of the corpus callosum; falx cerebri; optic tracts and ol- factory bulbs. Semilobar HP shares many of these same features, but demonstrates partial segmentation of the ventricles and incomplete fusion of thalami. Septo-op- tic dysplasia, the least severe type of HP, results in sepa- ration of the ventricles and thalami and absence of the septum pellucidum.5 The advent of high-resolution real-time ultrasound imaging equipment has allowed detection of the group of holoprosencephalies, but lack of familiarity with uncommon forms may lead to diag- nostic confusion. Coronal sonograms of the fetal head, in addition to standard axial projections, should be per- formed whenever an intracranial cystic abnormality is identified.6 Several characteristic midline facial malfor- mations are associated with holoprosencephaly, includ- ing hypotelorism. The degree of facial dysmorphism tends to parallel the severity of holoprosencephaly and, therefore, sonographic evaluation of facial morphol- ogy may aid in prenatal diagnosis.7 Recently, diffusion tensor imaging and fiber tracking have revealed white matter structures not apparent on routine MRI imag- ing sequences, which are in agreement with pathologic descriptions of the holoprosencephalic brain.8 R E F E R E N C E S 1. Wong Alex MC, Bilaniuk LT, Ng KK, Chang YL, Chao AS, Wai YY. Lobar holoprosencephaly: Prenatal diagno- sis with post natal MR correlation. Prenat Diagn 2005; 25:296-299. 2. Roessler E, Muenke M. Holoprosencephaly: A paradigm for the complex genetics of brain development. J Inher Metab Dis 1998; 21:481-497. 3. Golden JA. Towards a greater understanding of the pathogenesis of holoprosencephaly. Brain Dev 1999; 21:513-521. 4. De Myer W. Holoprosencephaly (cyclopia arhinenceph- aly). In: Yinken PJ, Bruyn GW, eds. Handbook of clini- cal neurology, Vol 30. Amsterdam: Netherlands. 1977. p. 431-478. 5. Byrd SE, Harwood-Nash DC, Fitz CR, Rogovitz DM. Computed tomography evaluation of holoprosencephaly in infants and children. J Comput Assist Tomogr 1997; 1:456-463. 6. Cayea PD, Balcar I, Oswaldo A Jr, Jones TB. Prenatal di-