"acrania: partial or complete absence of cranial vault bones with abnormal cerebral hemisphere development."
"cranium bifidum occultum (cleft skull): delayed ossification of the parietal bones with subsequent large midline skull defect"
"sinus pericranii: communication between intra- and extra-cranial venous systems through calvarial defects"
"acalvaria: absent superior osseous cranial vault and dura mater; normal skull base, brain and facial bones"
"arachnoid granulations: often multiple; irregular contour"
"acalvaria: absent superior osseous cranial vault and dura mater; normal skull base, brain and facial bones"