Intraosseous epidermoid cyst of the skull: case study and radiological imaging considerations

We report an atypical case of an epidermoid cyst associated with a skull defect to emphasize the diagnostic utility of bedside ultrasonography for the evaluation of subcutaneous scalp nodules. A 24-year-old woman presented with what appeared to be a benign cyst on the right parietal scalp. The cyst was first noticed one year prior to presentation and caused only mild irritation. Upon excision of the cyst, a notable calvarial defect was found in the frontoparietal bone and surgical excision was suspended. Head and brain imaging was performed confirming the calvarial defect with mild mass effect on the brain. A neurosurgical consultation was obtained, and the patient underwent craniotomy followed by cranioplasty with titanium plate placement. The histological evaluation confirmed the suspicion of an intraosseous epidermoid cyst. We hope to raise awareness of the potential for intraosseous involvement of otherwise routine scalp nodules and emphasize the utility of bedside ultrasonography as a quick, easy, and benign imaging modality to assist in preoperative evaluation.