Congenital calvarial defects are a group of disorders characterised by congenital calvarial bone defects that vary in severity.
Radiographic features
CT with 3D shaded surface reformats is the best imaging tool as it demonstrates calvarial defects and bone margins:
amniotic band syndrome: large skull defects
acalvaria: absent superior osseous cranial vault and dura matter. Normal skull base, brain and facial bones.
acrania: partial or complete absence of cranial vault bones with abnormal cerebral hemisphere development.
arachnoid granulations: often multiple having irregular contour
abnormally large fontanelle: secondary to increased intracranial pressure or skeletal dysplasia
aplasia cutis congenita: congenital skin defect which may have underlying skull defect
cleidocranial dysplasia: enlarged sagittal and metopic sutures, wide anterior and posterior fontanelles, broad cranial diameter, multiple Wormian bones along lambdoid sutures
cranium bifidum occultum (cleft skull): delayed ossification of parietal bones with subsequent large midline skull defect
parietal fissure: small residual incomplete medial parietal bone suture
sinus pericranii: communication between intra- and extra-cranial venous systems through calvarial defects
Differential diagnosis
Imaging differential considerations include:
calvarial epidermoid/dermoid
calvarial Langerhans cell histocytosis
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