An Infratemporal Dermoid Cyst That Expanded the Foramen Ovale: A Case Report

Dermoid cysts are rare tumors usually seen in the midline structure of the brain but rarely arise in the petrous apex and cavernous sinus. There have been very few reports of dermoid cysts arising in the infratemporal fossa, with scarce anatomic descriptions. Here we report the case of a patient with a dermoid cyst in the left infratemporal fossa.

The patient was a 43-year-old female with complaints of nonspecific headaches. A computed tomography (CT) scan revealed a cystic lesion measuring 25 × 18 × 15 mm in the left infratemporal fossa that had expanded the foramen ovale. The same lesion was observed as a high-intensity area on T1-weighted magnetic resonance imaging (MRI) with fat saturation. Diffusion-weighted MRI showed no restriction, unlike in cases of epidermoid cysts. A left fronto-temporo-sphenoidal craniotomy with a detachment of the zygoma was performed to approach the lesion. The tumor wall was continuously attached to the dura, although the tumor itself was entirely extradural in location. The V3 branch of the trigeminal nerve was firmly attached around the tumor. The tumor was cystic, and it shrunk after the fatty yellowish contents were suctioned. Complete resection was achieved without complications. A pathological analysis enabled the diagnosis of a dermoid cyst. No tumor recurrences or associated complications were observed at the 1-year follow-up.

Dermoid cysts in the infratemporal fossa are extremely rare. However, tumor resections can be performed safely and efficaciously using anatomically detailed preoperative planning.