Diagnostic Image: Coronal T2-weighted MRI of a pediatric brain demonstrating characteristic features of semilobar holoprosencephaly. The image shows a single, horseshoe-shaped lateral ventricle with presence of temporal horns but a notable absence of developed anterior horns. Key anatomical findings include the complete midline fusion of the frontal lobes and partial fusion of the deep gray matter structures, specifically the thalami and caudate nuclei. A rudimentary third ventricle is visible. The interhemispheric fissure is absent anteriorly due to the cerebral fusion but shows partial formation posteriorly. This visual is used to teach midline brain malformations and the continuum of prosencephalic cleavage failure, distinguishing semilobar variants from alobar and lobar types. Clinical significance pertains to neuroradiology, pediatrics, and embryology, illustrating severe neurodevelopmental defects often associated with craniofacial anomalies or chromosomal syndromes.

Two B-mode grayscale two-dimensional antenatal ultrasound images demonstrate fetal facial anomalies in a fetus at approximately 16 weeks gestation. (A) The 'en face' view shows a cross-sectional representation of the fetal face with visible orbits and a prominent midline soft tissue projection. (B) The 'sagittal' view provides a side profile clearly illustrating the forehead, nasal region, and oral cavity, with a distinct tubular or cylindrical structure extending outwards from the midline of the forehead. This structure, marked by yellow arrows in both views, is a proboscis, a hallmark facial dysmorphism often associated with holoprosencephaly spectrum disorders such as ethmocephaly or cyclopia. These images are critical for the prenatal diagnosis of midline craniofacial defects and the assessment of associated central nervous system malformations.

This composite image illustrates severe craniofacial malformations, specifically holoprosencephaly manifestations, comparing historical medical art with preserved pathology specimens. The image is divided into three columns: (a) 19th-century copperplate engravings, (b) lithographs, and (c) color photographs of preserved wet specimens. The top row depicts cyclopia, characterized by a single, centrally located eye (synophthalmia) in a single orbital cavity and an absent nose (arrhinia) with a visible philtrum and mouth. The bottom row demonstrates a more complex cephalic malformation where a single orbital opening is situated below a tubular, fleshy appendage known as a proboscis, which is located in the supraorbital region. These comparisons highlight the evolution of medical illustration from detailed artistic interpretation to modern specimen preservation. The visual focus is on midline facial defects, dysmorphic ears, and the anatomical variations of the proboscis and eye fusion, providing a historical and clinical perspective on teratological study and dysmorphology.

Clinical photograph of a neonatal specimen demonstrating severe craniofacial malformations consistent with holoprosencephaly. The central feature is cyclopia, characterized by a single median orbit located in the midline of the face. The orbit contains a fused or partially divided ocular globe with visible iris and pupil structures, partially covered by rudimentary eyelids. Superior to the orbit, a cylindrical skin-covered appendage known as a proboscis is present. The nose is absent (arrhinia). Inferior to the median eye, a malformed oral cavity is visible, showing a small mouth opening and a glimpse of the tongue. The surrounding facial skin displays significant discoloration, congestion, and visible superficial vasculature. Superior to the proboscis, there is evidence of exposed neural tissue or severe cranial defect, possibly related to anencephaly or a significant skull vault deficiency. This image serves as a clinical example of extreme midline defects arising from the failure of the prosencephalon to divide during embryonic development.

**Imaging Modality:** Sagittal T1-weighted Magnetic Resonance Imaging (MRI).

**Imaging Modality:** Axial T2-weighted Magnetic Resonance Imaging (MRI) of the brain.

**Imaging Modality:** T2-weighted axial Magnetic Resonance Imaging (MRI) of the brain.

**Imaging Modality:** Axial T2-weighted MRI of the brain.

**Imaging Modality:** Non-contrast Computed Tomography (CT) scan of the head.