The layer cake skull refers to the CT appearance of layered diffuse calvarial hyperostosis in a distinct concentric pattern deep to the inner table of the skull seen most frequently in the setting of spontaneous intracranial hypotension although it is also sometimes encountered in normal individuals 2.
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Epidemiology
A layer cake skull appearance is seen in 14-32% of patients with spontaneous intracranial hypotension but only in 5% of controls 1,2. It has also been described in paediatric patients who have ventricular shunts 3.
Pathology
It is hypothesised that this layered hyperostosis occurs due to chronic, but presumably variable, intracranial hypovolaemia resulting in increased bony deposition during times of maximal hypotension. The exact mechanism, however, remains to be determined 2.
Radiographic features
CT
On bony algorithm CT of the skull, the skull vault is thickened with discernable layers of new bone seen internally 1,2. This is in contrast to more common hyperostosis frontalis interna where no such layering is present 2.
Differential diagnosis
-
hyperostosis frontalis interna
multiple layers absent
often more nodular
region (frontal or fronto parietal)
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