Diagnostic Dilemma: Cerebellopontine Angle Lipoma Versus Dermoid Cyst

Abstract

Both lipomas and dermoid cysts of the cerebellopontine angle are rare tumors. These tumors differ in their embryological origin but share similar features on imaging. Both of these congenital lesions can be found in the cerebellopontine angle (CPA), and symptomatic clinical presentation is dictated by the location of the lesion. This paper demonstrates a unique case in which a CPA lipoma was misidentified as a dermoid cyst, leading to surgical intervention. Further, the paper provides a literature review of CPA lipomas and dermoid cysts to aid readers in further differentiating between these two unique tumors.

Keywords: cpa; dermoid cyst; lipoma; posterior fossa; retrosigmoid craniotomy; vertigo.

Figure 1. Axial fast imaging employing steady-state acquisition (FIESTA) sequence magnetic resonance imaging (MRI)

Image demonstrates a 17-mm hyperintense mass in the left cerebellopontine angle (CPA) with moderate mass effect on brainstem and surrounding structures. Arrow highlights involvement of cranial nerves VII and VIII.

Figure 2. Axial T1 precontrast sequence magnetic resonance imaging (MRI)

Image demonstrates a subtle increase in signal intensity from the mass (red arrow) compared to subcutaneous fat (green arrow). There are scattered hypointense calcifications present within the mass.

Figure 3. Axial T1 post-contrast fat saturation sequence magnetic resonance imaging (MRI)

Image demonstrates loss of signal hyperintensity within the left cerebellopontine angle mass with fat saturation techniques (see arrow), as is typical of fatty lesions.