Published online before print November 21, 2002, 10.1148/radiol.2261011754
(Radiology 2003;226:210-213.)
© RSNA, 2002
Craniofacial Duplication (Diprosopus): CT, MR Imaging, and MR Angiography Findings— Case Report1
Stefan Hähnel, MD,
Peter Schramm, MD,
Stefan Hassfeld, MD,
Hans H. Steiner, MD and
Angelika Seitz, MD
1 From the Departments of Neuroradiology (S. Hähnel, P.S., A.S.), Oral- and Cranio-Maxillofacial Surgery (S. Hassfeld), and Neurosurgery (H.H.S.), University of Heidelberg Medical School, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany. Received October 29, 2001; revision requested January 18, 2002; revision received March 25; accepted April 19. Address correspondence to S. Hähnel (e-mail: stefan_haehnel@med.uni-heidelberg.de).
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ABSTRACT
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Diprosopus is one of the rarest malformations in humans. In addition to the facial structures, the cerebral frontal lobes were duplicated in this case. Three pairs of anterior cerebral arteries were detected, and the rostral parts of the superior sagittal sinus were duplicated. Computed tomography, magnetic resonance (MR) imaging, and MR angiography allowed study of the degree of duplicative changes in diprosopus, especially for planning cosmetic correction.
© RSNA, 2002
Index terms: Face, abnormalities, 28.19 • Infants, newborn, central nervous system, 131.19 • Twins, abnormalities
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INTRODUCTION
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The prevalence of conjoined twins (Siamese twins) is reported to be one in 2,800 to 200,000 deliveries (1). Of all monoamniotic, monochorionic, and monozygotic twins, 10% are conjoined. Conjoined twins are classified according to their symmetry, site of fusion, and degree of duplication (2). The most frequent type of conjoined twins is thoracopagus (32.7%), with joining at or near the sternal wall and contained viscera, and the rarest type is diprosopus (0.4%), with two faces, one head, and one body (1). We report the computed tomographic (CT), magnetic resonance (MR) imaging, and MR angiographic findings in a 12-month-old boy with diprosopus. To our knowledge, this is the first postnatal in vivo report of diprosopus. The parents of the child gave written consent to include a photograph of the child’s face in this report. Our institutional review board does not require approval or informed consent for the review of patient records, files, or images.
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Case Report
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The 12-month-old child’s face demonstrated two noses and a large distance between the eyes as the most conspicuous features. In the midline, a supernumerary third orbit without an eyeball was visible. Furthermore, the child had an enlarged asymmetric mouth. The right nose was smaller than the left, as was the right part of the mouth with respect to the left (Fig 1). At the age of 3 months, a ventricular septal defect of the heart was treated by means of pulmonary artery banding. Otherwise, the child showed no physical or mental developmental abnormality.
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Figure 1. Photograph of the face demonstrates duplication of the nose, a large distance between the fully developed outer orbits, the supernumerary orbit (arrow) in the midline, and the large asymmetric mouth.
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Imaging Methods
CT, MR imaging, and MR angiography were performed in the 12-month-old boy to plan surgical reconstruction of the face. A three-dimensional data set was acquired with a Volume Zoom CT scanner (Siemens Medical Systems, Erlangen, Germany) with a section thickness of 1 mm. MR imaging was performed with a 1.5-T MR imager (Marconi Medical Systems, Highland Heights, Ohio) by using a head coil. The MR imaging protocol included a transverse three-dimensional fast low-angle-shot gradient-echo sequence (30/4.4 [repetition time msec/echo time msec]; section thickness, 1.3 mm; flip angle, 30°), a transverse time-of-flight arterial MR angiographic sequence (25/6.7; section thickness, 1.3 mm; flip angle, 20°), a transverse time-of-flight venous MR angiographic sequence (30/7.0; section thickness, 1.5 mm; flip angle, 30°), and a transverse fast spin-echo MR imaging sequence (3,016/16, 80; section thickness, 6 mm; flip angle, 90°).
Abnormal Findings
Skull base.—CT images showed complete duplication of the nasal skeleton, nasal cavity, and medial aspects of the maxillary bones (Figs 2, 3). The borders of the supernumerary rudimentary third orbit were formed by the duplicated orbital parts of the frontal bone and the duplicated orbital lamina of the ethmoid bone. The content of the supernumerary orbit was isointense with respect to fat on both CT and MR images.
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Figure 3. Surface-rendered three-dimensional reconstruction of a spiral CT data set, frontal view (section thickness, 1 mm), shows duplication of the nasal skeleton (white arrows), the large distance between the normal outer orbits, and the supernumerary orbit (black arrow).
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Cerebrum.—CT and MR images showed two lateral (Fig 4, F1 and F4) and two paramedial (Fig 4, F2 and F3) cerebral frontal lobes. The paramedial frontal lobes were fused at their dorsal aspects (Fig 5), and each paramedial frontal lobe was connected with the adjacent lateral frontal lobe (Fig 5, F2 with F1 and F3 with F4) by small commissures (Fig 6). The corpus callosum was completely absent. The amount of white matter in the paramedial frontal lobes (Fig 6, F2 and F3) was smaller than that in the lateral frontal lobes (Fig 6, F1 and F4), and there were no ventricles in the paramedial frontal lobes. The lateral frontal lobes, including the rostral parts of the lateral ventricles and the sylvian fissures, were lateralized. The basal ganglia and the thalamus were also lateralized but otherwise normally developed.
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Figure 4. Transverse MR image (30/4.4; flip angle, 30°) shows two lateral (F1, F4) and two paramedial (F2, F3) cerebral frontal lobes. The sylvian fissures (arrows) containing the middle cerebral arteries are lateralized. Three pairs (arrowheads) of postcommunicating segments of the anterior cerebral arteries are delineated as hyperintense tubular structures in the interlobar fissures between the frontal lobes.
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Figure 5. Transverse MR image (3,016/80; flip angle, 90°) shows the fusion site of the paramedial frontal lobes (F2, F3) and the vein of Galen (large arrow). The duplicated rostral parts (small arrows) of the superior sagittal sinus are also shown. Lateralization of the rostral parts of the lateral ventricles is evident.
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Figure 6. Reconstructed coronal MR image (30/4.4; flip angle, 30°) shows the small fusion sites (arrows) between each paramedial frontal lobe (F2, F3) and the adjacent lateral frontal lobe (F1, F4).
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Arteries.—In normal development, there is one right and one left anterior cerebral artery, and, usually, an unpaired communicating vessel (anterior communicating artery) between the right and left anterior cerebral arteries, defining the border between the pre- and postcommunicating segments of the anterior cerebral arteries. In our patient, the anterior cerebral arteries divided into three pairs of postcommunicating segments (Figs 4, 7): The right and middle pairs arose from the right anterior cerebral artery, and the left pair arose from the left anterior cerebral artery. A communicating vessel was not detected between the left anterior cerebral artery and the middle pair of the postcommunicating segments of the anterior cerebral artery and thus was aplastic or hypoplastic (Fig 7). No other abnormalities were detected in the carotid or vertebrobasilar vascular territories.
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Figure 7. Maximum intensity projection of an MR angiographic image, frontal view (25/6.7; flip angle, 20°), shows three pairs (arrows) of postcommunicating segments of the anterior cerebral arteries; the communicating vessel (arrowhead) between the middle and the left pair is hypoplastic or aplastic. No other abnormality in the carotid or vertebrobasilar system was evident.
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Veins.—The rostral parts of the superior sagittal sinus were duplicated and located between the paramedial frontal lobes and the lateral frontal lobes. A large bridging vein was delineated that crossed from the midline over the surface of the left paramedial frontal lobe and drained into the left rostral part of the superior sagittal sinus (Fig 8). Apart from a hypoplastic left transverse sinus, there was no other abnormality in the venous system.
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Figure 8a. Maximum intensity projections (a, lateral view; b, frontal view; c, oblique view) of MR angiographic images (30/7; flip angle, 30°) show the duplicated rostral parts (arrows) of the superior sagittal sinus and a large bridging vein (arrowheads) draining into the left rostral part of the superior sagittal sinus (SSS). The internal cerebral veins, the straight sinus (SS), and the right transverse sinus (RTS) were normal; the left transverse sinus was hypoplastic.
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Figure 8b. Maximum intensity projections (a, lateral view; b, frontal view; c, oblique view) of MR angiographic images (30/7; flip angle, 30°) show the duplicated rostral parts (arrows) of the superior sagittal sinus and a large bridging vein (arrowheads) draining into the left rostral part of the superior sagittal sinus (SSS). The internal cerebral veins, the straight sinus (SS), and the right transverse sinus (RTS) were normal; the left transverse sinus was hypoplastic.
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Figure 8c. Maximum intensity projections (a, lateral view; b, frontal view; c, oblique view) of MR angiographic images (30/7; flip angle, 30°) show the duplicated rostral parts (arrows) of the superior sagittal sinus and a large bridging vein (arrowheads) draining into the left rostral part of the superior sagittal sinus (SSS). The internal cerebral veins, the straight sinus (SS), and the right transverse sinus (RTS) were normal; the left transverse sinus was hypoplastic.
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The cerebellum, midbrain, brainstem, and pituitary gland did not show any abnormality.
For cosmetic reconstruction, the supernumerary facial bone structures, including the third orbit, were resected; the roofs of the normally developed lateral orbits were medialized; and the lateral aspects of the right and left noses were adapted with good result.
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Discussion
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The rarest type of conjoined twins and one of the rarest malformations in humans is diprosopus, with two faces, one head, and one body (1). Since 1884, there have been only 35 reports of diprosopus in the world medical literature, including the present case, which is the first postnatal in vivo report of diprosopus (3-7), to our knowledge. We found no case of a live-born neonate with diprosopus in the medical literature. The spectrum of diprosopus ranges from simple nasal duplication to two complete faces on a single head (diprosopus monocephalus) (8). In our case, the duplicative changes were relatively mild, involving only noses, eyes, and the cerebral frontal lobes.
Currently, the most widely accepted theory for the formation of conjoined twins is incomplete splitting of a single embryo between the 13th and 25th day after conception (9,10). More recently, however, some authors have postulated that conjoined twins result from the development of two independent notochords initially destined to become separate twins but which are too close to develop independently (11).
With regard to diprosopus in particular, Barr (12) addressed the problem of distinguishing between a focal duplicative process and true twinning in the facial region: In contrast to all other forms of conjoined twins, which always have two complete notochordal axes, diprosopus might represent a genuine rostral bifurcation or duplication of the notochord. Alternatively, diprosopus could be closely related to dicephalus, in which there are two completely separate but parallel notochordal axes within one vertebral column (1,8,12). In our case, except for the forebrain, the neuroaxis showed no abnormality. Therefore, we believe that this is a case of focal duplication rather than true twinning.
The duplication of the eyes always implies a duplication of the major portion of the prosencephalon, because such a duplication leads to the appearance of three or four optic vesicles and one set of telencephalic vesicles, each with one rhinencephalon (12). Each pair of rhinencephalons would, in turn, induce the development of an olfactory placode, leading to two complete noses, as observed in this case. Whereas duplication of the eyes is always associated with duplication of the nose, the converse is not true: Nasal duplication may be isolated, since nasal development appears to proceed normally in the absence of discernible olfactory bulbs and nerves, as in arhinencephaly (12).
Most neonates with diprosopus are stillborn. In the rare case of a live-born neonate with diprosopus, CT, MR imaging, and MR angiography all provide information for evaluating the degree of duplication, particularly if cosmetic correction is planned.
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FOOTNOTES
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Author contributions: Guarantor of integrity of entire study, S. Hähnel; study concepts, S. Hähnel; study design, S. Hähnel, P.S.; literature research, P.S., A.S.; clinical studies, P.S., H.S.; data acquisition, P.S., S. Hähnel; data analysis/interpretation, all authors; manuscript preparation and definition of intellectual content, S. Hähnel; manuscript editing, S. Hähnel, S. Hassfeld; manuscript revision/review and final version approval, all authors.
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ABSTRACT
INTRODUCTION
