Subgaleal dermoid cyst of the anterior fontanelle: diagnosis with sonography.

We report the plain film and sonographic findings in six children (2 1/2 months to 5 years old) with a subgaleal dermoid cyst at the anterior fontanelle. Plain films of the skull made in all patients showed a soft-tissue mass superficial to the anterior fontanelle with a normal subcutaneous fat layer above it. In three children, the margins of the anterior fontanelle were beveled to match the contour of the mass. Sonography in the five children with open fontanelles showed the mass to have a well-defined sonolucent interior with a clear wall separating it from the superior sagittal sinus and other intracranial contents. The combination of clinical evaluation, plain films, and sonography appears to be sufficient to make the diagnosis of subgaleal dermoid cyst of the anterior fontanelle.