Diprospus (sometimes called Craniofacial duplication) is a rare disorder in which the face is duplicated on the head (as in the picture above). This is not to be confused with fetus in fetu   which is a joining of two separate fetuses; diprosopus is caused by a protein called (believe it or not) “sonic hedgehog homolog”. The odd name is due to a controversial tradition in molecular biology to use unusual names for genes. The protein determines the makeup of the face, and when there is too much of it, you get a second face in a mirror image. If you do not have enough of the protein, you can end up with underdeveloped facial features. Children with this defect are normally stillborn, but a young girl, Lali Singh, born in 2008 survived for 2 full months before dying of a heart attack.

 

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.

  Figure 2. Transverse CT scan shows duplication of the nasal cavities, nasal skeleton, and medial aspects of the maxillary bone (arrows).

 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).

 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.

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.

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).

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

Discussion

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.