Diagnosing cranial fasciitis based on distinguishing radiological features.

Primary skull lesions, albeit rare in the pediatric population, have been well described and classified. These lesions are usually benign and commonly present as a painless mass. The most common lesions are epidermoid, dermoid, and Langerhans cell histiocytosis. Cranial fasciitis, encountered less frequently, is usually not considered in this differential diagnosis. Given such few cases reported, it is commonly misdiagnosed preoperatively. The authors retrospectively reviewed data obtained in 4 patients with cranial fasciitis in whom the diagnosis was based on histopathological findings. In 2 patients the onset of the lesion was spontaneous. One patient had a lesion 4 months following a vacuum extraction and subsequent cephalohematoma formation. One patient developed a lesion following a previous craniectomy. Presentation, imaging studies, and histopathological findings were all reviewed and analyzed. All patients presented with a firm nontender mass. Radiological features included a lytic bone lesion with a mildly sclerotic margin, T1 isodensity, T2 heterogeneous hyperdensity, and heterogeneous enhancement. The enhancing portion was not bright on T2-weighted MR images, likely representing the fibrous component; the nonenhancing portion was bright on T2-weighted images, likely representing the myxoid matrix. Histopathological examination revealed proliferating fibroblasts in a myxoid matrix. Cranial fasciitis is a benign, painless but rapidly growing lesion of the skull mainly limited to the pediatric population. It is histologically similar to nodular fasciitis, a fibroblastic proliferation of varying size. These lesions are often related to trauma but can also be insidious or can develop at a prior craniectomy site. The appropriate clinical picture and distinguishing radiographic features may help to differentiate cranial fasciitis from other lesions of the skull allowing for earlier intervention.