EC Cancer

Background: Epidermoid cysts are congenital, benign lesions most commonly located in the cerebellopontine angle (CPA) and parasellar cisterns. They typically show restricted diffusion on MRI without contrast enhancement, a feature that often confirms the diagnosis. However, in some cases, they may exert significant mass effect that mimics low-grade or cystic tumors.

Case Report: We present the case of a 34-year-old man who experienced a first-time generalized seizure. MRI revealed a non-enhancing lesion in the left CPA and suprasellar cistern that showed bright diffusion restriction, consistent with an epidermoid cyst. The lesion displaced nearby brain structures-including the temporal lobe, pons, and posterior cerebral artery-yet did not cause edema or enhancement. A complete imaging work-up, including DWI, T1, T2, fat-suppressed, and susceptibility sequences, confidently excluded neoplastic or dermoid pathology.

Conclusion: Even when epidermoid cysts cause mass effect, their lack of enhancement and absence of edema are distinguishing features that separate them from tumors. Careful use of multi-sequence MRI is essential in evaluating these lesions and can help avoid unnecessary intervention while guiding appropriate surgical planning [1,2,3,6].

 Keywords: Epidermoid Cyst; Cerebellopontine Angle; Diffusion-Weighted Imaging; Tumor Mimic; Suprasellar Cistern; Internal Auditory Canal

1. Reddy VN., et al. “Spectrum of intracranial and spinal epidermoids including unusual locations and imaging findings: A pictorial review”. Journal of Medical Imaging and Radiation Oncology 1 (2023): 65-76.
2. Jia Z., et al. “Neuroendoscopic cystectomy through the posterior approach to the sigmoid sinus for intracranial epidermoid cysts: A review of two cases”. Interdisciplinary Neurosurgery 40 (2025): 102059.
3. Alosaimi A., et al. “Unilateral hearing loss as the sole presentation of extensive intracranial epidermoid cyst: a case report”. Cureus5 (2025): e84721.
4. Vernon V., et al. “Surgical management of cerebellopontine angle epidermoid cysts: An institutional experience of 10 years”. British Journal of Neurosurgery2 (2022): 203-212.
5. Bonneville F., et al. “Imaging of cerebellopontine angle lesions: an update”. European Radiology 10 (2007): 2472-2482.
6. Golfinos JG., et al. “Nonschwannoma tumors of the cerebellopontine angle”. Otolaryngologic Clinics of North America3 (2015).