Ruptured Intracranial Dermoid Cyst with Fat Dissemination: A Clinical Case Mimicking an Epidermoid Cyst and Review of the Literature

Abstract

Background and Clinical Significance: Intracranial dermoid cysts (IDCs) are rare benign congenital intracranial lesions. In the case of IDC rupture, these lesions may manifest clinically. Cysts may be visualized on non-enhanced computed tomography (NECT) and magnetic resonance imaging (MRI), facilitating discussions between clinicians and radiologists to determine cyst content and potential dissemination in cases of rupture. This case report describes an IDC rupture presenting as fat-containing lesions in the subarachnoid space and ventricular system, resembling a subarachnoid hemorrhage on MRI. Case Presentation: A thirty-two-year-old Caucasian male patient was admitted to the hospital due to recurrent headaches and visual impairment that began at the age of thirty-one. MRI revealed a lesion radiologically consistent with a ruptured dermoid or epidermoid cyst in the anterior fossa with a mass effect on the optic nerve intracranial segments, the chiasma opticum, and proximal optic tracts. The patient underwent a successful neurosurgical resection of the lesion, and histopathological analysis confirmed the diagnosis of a dermoid cyst. The postoperative period was uneventful. MRI follow-up revealed residual tissue of the IDC without any volume increase. Multiple punctate fat-containing lesions were noted, similar to previous MRIs. The patient reported no complaints at discharge. Follow-up MRI imaging demonstrated no recurrence or progression of the dermoid cyst at 4 months, 1 year, and 2 years. Conclusions: IDC rupture is a rare event that may present clinically and appear as a blooming artifact on MRI, mimicking subarachnoid hemorrhage. Fat-containing lesions in the subarachnoid space and ventricular system can demonstrate findings indicative of an IDC rupture. MRI diffusion-weighted imaging (DWI) and decreased apparent diffusion coefficient (ADC) values may mimic an epidermoid cyst, a phenomenon rarely described in the literature, further complicating the diagnostic process.

Keywords: blooming artifact; epidermoid cyst; intracranial dermoid cyst rupture; intraventricular fat dissemination; subarachnoid fat dissemination.

Figure 1

(A): MRI of the brain (T2-FLAIR axial sequence) showing a slightly hyperintense lesion, most likely a dermoid cyst, located in the basal dorsal anterior fossa. The cyst extended into the suprasellar cisterns, positioned above the chiasma opticum and the prechiasmal part of the optic nerve. It was situated under the anterior cerebral arteries and caused compression and displacement of the anterior parts of the third ventricle. Despite this, the foramen of Monro remained open. Additionally, there was an expansion of the lateral and third ventricles. (B): MRI of the brain (T2W-TSE axial sequence) showing an intracranial cyst located in the anterior fossa. The lateral ventricles were dilated, with the temporal horns measuring up to 8.5 mm, indicative of hydrocephalus. The likely cause of hydrocephalus development was a combination of the ruptured dermoid cyst and its intraventricular spread, exerting a mass effect on the third ventricle and aqueductus cerebri. TV—third ventricle, *—intracranial dermoid cyst.

Figure 2

(A): MRI of the brain T1W sag. The intracranial dermoid cyst located in the anterior fossa with hyperintense fat-containing lesions (small arrows) and extracellular methemoglobin-containing hemorrhage (arrowhead), representing a small subacute hemorrhage due to cyst rupture. (B): MRI of the brain T1W ax. sequence showing the intracranial dermoid cyst located in the anterior fossa with a mass effect on the chiasma opticum. Dermoid cyst rupture with massive subarachnoid fat inclusions of various sizes in the frontal lobes, cisterns, occipital, temporal lobes, and upper parts of the cerebellar hemispheres. CC—corpus callosum, CO—chiasma opticum, *—intracranial dermoid cyst, arrows—fat-dissemination lesions, arrowhead—extracellular methemoglobin-containing subacute hemorrhage.

Figure 3

(A): MRI of the brain SWI susceptibility-weighted imaging sequence showing the intracranial dermoid cyst located in the anterior fossa with fat-containing lesions, revealing a blooming artifact (yellow arrows). (B): MRI T1W post-contrast axial sequence showing leptomeningeal enhancement around the uncus most likely due to chemical meningitis (arrowhead). Arrows—punctate fat-containing lesions, *—intracranial dermoid cyst.

Figure 4

In the images (A) (DWI sequence) and (B) (ADC map), there is a lesion located in the anterior cranial fossa along the midline, demonstrating slight diffusion restriction and minimally decreased ADC values (yellow arrow). Preoperatively, this lesion mimicked an epidermoid cyst; however, histology confirmed it to be a dermoid cyst.

Figure 5

Hematoxylin and Eosin stain of the dermoid cyst. Tissue samples lined by squamous epithelium with keratinization. Subepithelially abundant sebaceous gland foci and hair follicles. The tissue lacks cytological atypia. (A): Microscopic magnification 4× (HPF). (B): Microscopic magnification 10× (HPF).

Figure 6

Follow-up. (A): MRI of the brain T1W sagittal at the 1-year follow-up, showing that the dermoid cyst has been subtotally resected (*). There are very small fat lesions (yellow arrows), as well as residual calcifications of the dermoid along the left side of the postoperative lobe, and, as in the previous MR examination, small scarring changes with encephalomalacia in the dorsal parts of the gyrus recti of both frontal lobes. No data are provided on the progression of the dermoid cyst. (B): CT of the brain at the 2-year follow-up, showing that the intracranial dermoid cyst has been largely resected (*). There are very small fat lesions (yellow arrows). No data are provided on the progression of the dermoid cyst. *—intracranial dermoid cyst, arrows—punctate fat-containing lesions.