A Rare Case of an Intracranial Dermoid Cyst with Atypical Appearance on Computed Tomography and Magnetic Resonance Imaging.

BACKGROUND Dermoid cysts are rare benign intracranial tumors that usually present classic computed tomography (CT) and magnetic resonance imaging (MRI) characteristics, allowing for relatively simple diagnostic confirmation. Atypical imaging features can occur due to their diverse ectodermal-derived content, which can result in a diagnostic dilemma. Making an accurate diagnosis is essential for adequate management. CASE REPORT We present a case of a 39-year-old woman with past medical history of increased blood pressure, presenting with worsening headaches non-refractory to medication. Imaging revealed an extra-axial lesion within the midline posterior fossa with an occipital transdiploic linear channel. The lesion was T2 profoundly hypointense on brain MRI, and prominently hyperdense on non-contrast CT scan. Catheter angiography excluded vascular etiology. After complete lesion resection, results of the histopathologic examination were consistent with a dermoid cyst. Dermoid cysts that are hyperdense on CT and hypointense on T2-WI are extremely rare. CONCLUSIONS Complete surgical resection is the treatment of choice for most dermoid cysts. Atypical radiologic features, in an already rare intracranial tumor, can delay correct diagnosis and management. Recognition of these findings is therefore important for adequate imaging analysis of these lesions.