Epidermoid Cyst vs. Sinus Pericranii
Left picture: The diagnosis is an intraosseous parietal epidermoid cyst lying almost exclusively in the skull, and in which the internal tabula protrudes only slightly in the direction of the dura. Right picture: In this patient a so-called sinus pericranii is present which has been present since birth, and which can be diagnosed with a plain skull x-ray and ultrasound. The additional picture at the bottom shows a similar clinical finding in a 2-month-old infant with cushion-like masses in the frontoparietal region, corresponding to abnormal veins draining in the superior sagittal sinus (= sinus pericranii), or to other vascular malformations.
In both cases a skull defect is visible in the CT or MRI. Left picture: In this pathology the defect has a round limit, and the underlying pathology is almost exclusively restricted to the skull. Right picture: That is not the case in this radiological finding; the skull defect continues obliquely through the bone to the outside like a process.