This patient presented with a lump on the head of long duration. A dermoid cyst was suspected clinically, and CT requested to assess for possible intracranial extension. The sagittal reformat (main image) shows a well-defined soft-tissue & fat density lesion extending through the frontal bone and contacting the superior sagittal sinus. The 3D reformat shows well-defined scalloping of the frontal bone. The imaging features are typical of a midline dermoid cyst.

Dermoid cysts are found in several locations in the skull. They are thought to arise from inclusion of ectodermal elements at sites of sutural and neural tube closure. They are commonly seen near the anterior fontanelle, glabella, nasion, vertex, and subocciput. Nasal and ethmoid dermoids may be associated with long sinuses and skin ostia. Nasal and ethmoidal dermoids should be imaged with high resolution MRI to define sinus tracts, as there is a high risk of intracranial extension and associated complications.

Reference: MorĂ³n FE, et al. Lumps and Bumps on the Head in Children: Use of CT and MR Imaging in Solving the Clinical Diagnostic Dilemma. RadioGraphics 2004;24:1655-1674

Credit: Dr Laughlin Dawes