Holoprosencefalia

Notas del editor

1. Cyclopic pig, an engraving by N. F. Regnault, in Morceau de la Sarthe, 1808. Arrow = proboscis. (Reprinted, with permission, from reference 2.)
2. La línea media se forma desde una estructura en la línea media bajo la infuencia del paltillo precodal , el campo visual debe separarse en derecho e izquerdi.
3. Aprosencephaly. Coronal in utero magnetic resonance (MR) image shows failure of normal division of the prosencephalon (forebrain) into telencephalon (cerebrum) and diencephalon (thalamus, hypothalamus). Note the intact calvaria and scalp (arrows) with no supratentorial brain. The key observation is that the falx is absent (* = expected locationn of normal falx). Figure 4. Atelencephaly. (a) Transverse ultrasonographic (US) image shows a featureless appearance with no identifiable brain architecture at 21 weeks gestational age. A = anterior, P = posterior. (b) Autopsy specimen confirms the diagnosis of atelencephaly, with formation of the diencephalon (black arrow) only and absence of telencephalic structures. Normal cerebella (arrowheads) and brainstem structures (white arrow) are present. (Fig 4b reprinted, with permission, from Amirsys [Salt Lake City, Utah].)
4. Minimal y microforma: These cannot be diagnosed in the fetus and will not be further discussed other than to note that identification of these forms in first-degree relatives (including parents) supports an underlying genetic component with potential for higher recurrence risk than in isolated sporadic cases.
5. Coronal endovaginal US image shows SOD in a fetus. Presence of the corpus callosum (arrowhead) with absence of the cavum helped identify SOD, with postnatal confirmation of the diagnosis. Axial T2-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) fetal MR image shows SOD. Communication between the frontal horns with an absent cavum septum pellucidum (arrow) is seen. No other abnormality was seen.
6. Saber el riesgo de recurrencua de HPE es imposible debido a su etilogia multifactorial-
7. The brain in alobar HPE can be described as ball-, cup-, or pancake-like in shape on the basis of the appearance on sagittal views. In the ball-like form, which is the most common, a relatively generous volume of cerebral cortex completely encircles the monoventricle. In the intermediate stage, the monoventricle is not completely encircled and the remaining cortex has a “cup” configuration. In the “pancake” forremaining cortex is flattened at the base of the skull. m, the small volume of
8. Alobar HPE. (a) Axial oblique US image obtained at 18 weeks shows fused thalami (arrowheads) and a monoventricle (*). (b) Axial oblique US scan obtained at a higher level shows the cuplike morphology of the noncleaved hemispheres (arrows) “cupping” the monoventricle (*). middle and anterior cerebral arteries may be absent, replaced by a network of vessels arising from the internal carotid and basilar vessels
9. Figure 12. Alobar HPE. (a) Coronal fetal MR image shows a monoventricle (*), fused thalami (arrows), and minimal overlying brain tissue (arrowheads). (b) Sagittal T2- weighted half-Fourier RARE MR image shows a flattened midface (arrow) and the “ball” configuration of the remaining cortex (arrowheads) surrounding the monoventricle (*). (c) Coronal US image in the neonate confirms the single monoventricle (*), fused thalami (arrows), and minimal overlying brain tissue (arrowheads).
10. Figure 13. Alobar HPE. Sagittal color Doppler US image of a fetal head shows the “snake under the skull” sign: a single anterior cerebral artery (arrow), also known as an azygous anterior cerebral artery, displaced anteriorly to run under the frontal bones, instead of between the frontal lobes as in a normally formed brain.
11. El diagnóstico prenatal de HPE alobar es bastante sencillo Semilobar y lobar pueden ser un desafío. In semilobar HPE, the interhemispheric fissure and falx cerebri may be present posteriorly and part of the corpus callosum may be seen in the region of the posteriorly sepa rated hemispheres , with the anterior extent corresponding to that of the interhemispheric fissure. somewhat arbitrary criterion used in postnatal imaging is that the malformation is semilobar if the frontal lobes are more than 50% fused
12. Semilobar HPE. (a) Axial oblique US image shows a continuous mantle of brain anteriorly (arrowheads) but posterior division into hemispheres (arrows). (b) More inferior axial US image in the same patient shows normal posterior fossa structures (arrow) below the tentorium but fused anterior supratentorial brain (arrowheads).
13. Semilobar HPE. (a) Coronal US image shows a monoventricle (*) and partial fusion of the thalami (T). (b) Coronal T2-weighted half-Fourier RARE MR image shows the continuous anterior brain parenchyma (arrow), monoventricle (*), and partially fused thalami (T). (c) Coronal T2-weighted half-Fourier RARE MR image more posteriorly shows two occipital lobes separated by the falx (arrow).
14. Lobar HPE. (a) Axial US image shows a continuous midline echo anteriorly (arrow). We were not able to demonstrate the cavum septum pellucidum in any plane. (b) Axial fetal MR image shows apparent complete division of the cerebral hemispheres (arrowheads). (c) Coronal fetal MR image shows anterior inferior gyral continuity between the frontal lobes (arrow). This was not demonstrable at US; the index finding was inability to demonstrate a normal cavum septum pellucidum.
15. MIH. Axial T2-weighted half-Fourier RARE MR images obtained at 33 weeks estimated gestational age. Note the lack of midline separation in the posterior frontal and parietal areas (*), while rostral and posterior regions of the cerebrum are cleaved normally, and the orbits are spaced normally. Also, note the vertically oriented sylvian fissures (arrows), which abnormally connect across the vertex.
16. MIH. Axial (a, b) and coronal (c) T2-weighted MR images in a neonate diagnosed prenatally with MIH show a lack of separation in the posterior frontal lobes (black arrowhead). Also note the abnormal appearance of the vertically oriented sylvian fissures (arrows in a and b), which extend more toward the midline than expected, and the cortical dysplasia (white arrowhead in c) and gray matter heterotopia (arrow in c).
17. The butterfly sign may be reliably seen in a cross section of the normal first-trimester brain. The choroid plexus is narrow in the middle but thicker at both ends, and when seen side by side the choroids create a butterfly appearance.