This midline cranial cleft usually occurs with a midline facial cleft that completes a median craniofacial dysraphia. A broad nasal root and bifid nose are associated with orbital hypertelorism and a median frontal encephalocele. The frontal bone abnormality varies from a minor flattening to a large midline defect. There is an increased distance between the olfactory grooves. The crista galli is widened, duplicated, or in some cases absent. Marked inferior prolapse of the enlarged ethmoid bone occurs with orbital hypertelorism. The severe orbital hypertelorism is associated with a broad flattening of the glabella and extreme lateral displacement of the inner canthi. The periorbita, including the eyelids and eyebrows, are otherwise normal. A long midline projection of the frontal hairline marks the superior extent of the soft tissue features of this midline cranial cleft. The median frontal defect delineates the region through which the frontal encephalocele herniates. The lateral segments of the frontal bone sweep upward from the region of the intact glabella and are flattened laterally. No pneumatization of the frontal sinus is evident. The crista galli and the perpendicular plate of the ethmoid are bifid. Just as the ethmoid, including the cribriform plate, is widened and caudally displaced, the sphenoid sinus is broadened and extensively, but symmetrically pneumatized. The lateral rotation of the greater and lesser wings of the sphenoid results in a relative shortening of the anteroposterior dimension of the middle cranial fossa. The floor of the anterior cranial fossa is upslanting from its medial aspect to its lateral aspect, with a harlequin appearance on the coronal scan. [from
HPO]