Ruptured intracranial dermoid cyst as an incidental finding: Case report

Abstract

Intracranial dermoid cysts are rare, benign congenital lesions originating from ectodermal remnants. Though typically asymptomatic, their rupture, although infrequent, can lead to significant neurological complications, such as chemical meningitis, vasospasm, and hydrocephalus. Imaging with computed tomography (CT) and magnetic resonance imaging (MRI) plays a crucial role in diagnosis, providing characteristic features related to the high lipid content of these lesions. An 86-year-old female presented with a 3-day history of headache, nausea, vomiting, and facial cellulitis after an arthropod bite. Concern that the facial cellulitis might have progressed and involved deeper structures prompted imaging studies. Non-contrast CT revealed an incidental ruptured pericallosal dermoid cyst with lipid material in the ventricular system. MRI confirmed the rupture, showing hyperintense lesions on T1-weighted sequences. Cerebrospinal fluid analysis indicated aseptic meningitis. The patient has been diagnosed with herpes zoster-related meningoencephalitis. Despite their rarity, ruptured intracranial dermoid cysts remain challenging due to their complex presentation. Early identification through advanced imaging is essential for guiding appropriate intervention. While complete resection is the goal, subtotal excision can be indicated when the cyst capsule adheres to critical neurovascular structures, given the low risk of recurrence and malignant transformation.

Introduction

Intracranial dermoid cysts are benign congenital inclusion tumors, accounting for 0.04% to 0.6% of all primary intracranial neoplasms [1]. These lesions originate from ectodermal, mesodermal, and endodermal germ layers, but are characterized by a thick capsule of stratified squamous epithelium, predominantly containing sebaceous and apocrine glands, underscoring their ectodermal dominance. The most common anatomical distributions include the midline of the posterior fossa, as well as suprasellar, frontobasal, and temporobasal regions [[1], [2], [3]]. Due to their slow growth, these cysts frequently remain asymptomatic until they reach a size sufficient to exert a mass effect. Depending on their anatomical location, clinical manifestations may include headache, nausea, and vomiting. Rupture, though uncommon, has been documented secondary to closed head trauma, iatrogenic injury during neurosurgical procedures, or spontaneous events [4,5]. While asymptomatic rupture has been reported [6], symptomatic rupture often leads to acute neurologic deterioration, with complications such as altered mental status, chemical meningitis, and, in severe cases, sudden death. Cerebrospinal fluid (CSF) analysis in these scenarios typically reveals findings consistent with aseptic or chemical meningitis [[4], [5], [6], [7], [8], [9]]. The present article aims to report a case of ruptured pericallosal epidermoid cyst with ventricular and basal cisterns dissemination and also to provide a review of literature on this uncommon topic.

The imaging characteristics of intracranial dermoid cysts are highly variable and influenced by their embryologic origin. Some authors have noted positional mobility of these lesions relative to changes in head orientation [9]. Fawcitt and Isherwood first delineated the radiologic features of ruptured dermoid cysts on computed tomography (CT) in 1976 [3], describing them as well-defined, extra-axial lesions with rounded or lobulated morphology, demonstrating fat-fluid levels in the periventricular region and/or fat density within the subarachnoid space. On magnetic resonance imaging (MRI), these lesions typically exhibit hyperintensity on T1-weighted sequences and hypo to hyperintensity on T2-weighted sequences. It is important to note, however, that in the absence of significant lipid content, the relaxation times and resultant signal characteristics may deviate from this classic appearance [2,9].

Material and methods

A comprehensive literature review was conducted using the PubMed and Clinical Key databases. The search strategy incorporated the keywords “ruptured intracranial dermoid cysts,” “ventricular fluid,” and “cistern fluid.” Boolean operators such as "OR" were applied to expand the search by incorporating all identified synonyms according to the terminology of each thesaurus. Additionally, case reports and articles providing valuable insights into the presentation, imaging findings, or clinical management of ruptured intracranial dermoid cysts were considered, regardless of the anatomical site. No restrictions were applied concerning the year of publication.

Titles and abstracts of all retrieved articles were independently screened by the authors. Eligible studies were selected for inclusion based on relevance, and categorized as accepted or rejected. Extracted data included author names, year of publication, patient demographics, imaging modalities utilized, and reported radiological findings. Full-text versions of the selected articles were subsequently obtained and reviewed in detail for qualitative analysis.

Case report

An 86-year-old woman with no significant past medical history presented to the emergency department of our institution following an unspecified arthropod bite on the right frontal region of the face. She reported a 3-day history of severe frontal headache, nausea, vomiting, fever, and generalized myalgias. On physical examination, the patient was in acceptable general condition but exhibited apparent right-sided facial cellulitis. Given the presence of red flag signs associated with the headache, a non-contrast cranial computed tomography (CT) scan was performed, revealing central predominant ex vacuo changes and leukoaraiosis.

Incidentally, a pericallosal epidermoid cyst with rupture and dissemination of lipid material into the ventricular system and basal cisterns was identified (Fig. 1). Based on these findings, the patient’s clinical deterioration, and cerebrospinal fluid (CSF) cytochemical analysis consistent with aseptic meningitis, a contrast-enhanced brain magnetic resonance imaging (MRI) was obtained. The MRI demonstrated lipid-containing lesions with hyperintensity on T1-weighted sequences and blooming artifacts on susceptibility-weighted imaging (SWI), localized within the ventricular cavities and subarachnoid spaces. In general, this magnetic behavior suggests fat particles that could correspond to a ruptured dermoid cyst (Fig. 2).

Fig. 1.

Non-contrast cranial computed tomography in a brain parenchyma window (A and B) demonstrate sagittal reconstruction image (A) showed accumulation of lipid material in the cisternal and pericallosal regions (white arrows) and coronal reconstruction image (B) showed the presence of lipid density material in the same regions (white arrows).

Fig. 2.

Cerebral magnetic resonance imaging reveals intraventricular lipid material (white arrows in A, B, C, D, E). Axial (A) and sagittal (B) T1-weighted images show a hyperintense signal due to cholesterol components. Axial T2-weighted image (C) demonstrates a hypointense signal corresponding to the lipid material. Axial susceptibility-weighted image (D) reveals blooming artifacts, without hypointensities or paramagnetic components. Post-contrast T1-weighted image (E) shows no enhancement, as expected in uncomplicated cases.

Subsequently, the patient was diagnosed with meningoencephalitis secondary to herpes zoster, confirmed via FilmArray® panel testing.

Table 1.

Compilation of reported cases of ruptured intracranial dermoid cysts identified in the literature, organized by year of publication, patient sex and age, anatomical location of the cyst, clinical presentation, diagnostic imaging modality, and radiological findings [[10], [11], [14], [12], [15], [13]] (Table 1).

Authors	Year	Number of patients	Sex	Age	Anatomic location	Imaging modality	Imaging findings
Orakcioglu et al.	2008	7	Female	19 year-old	Left fronto-basal, intraventricular	CT	Hypodense, some solid structures
Orakcioglu et al.	2008	7	Male	33 year-old	Intrasellar, roof of orbit, right petrous bone, intraventricular	MRI	T1-hyperintensity (nonhomogenous), T2-hyperintensity, fatty particles T1-hyperintense
Orakcioglu et al.	2008	7	Female	16 year-old	Parasellar, right suprasellar, intraventricular, basal cisterns	MRI	T1-hypointensity (nonhomogenous), T2-hyperintensity, Gd enhancement, fatty particles T1-hyperintense
Orakcioglu et al.	2008	7	Male	60 year-old	Right posterior fossa with compression of 4th ventricle	MRI	T1-hypointensity (nonhomogenous), T2-hyperintensity, Gd enhancement, DWI hyperintensity, leptomeningeal Gd enhancement, (convexity, Sylvian fissure, perimedullary)
Orakcioglu et al.	2008	7	Male	56 year-old	Suprasellar with compression of optic chiasm	MRI	T1-hypointensity, T2-hyperintensity, Gd enhancement, DWI hyperintensity, (inhomogeneous)
Orakcioglu et al.	2008	7	Female	19 year-old	Meckel’s cave, Foramen ovale	MRI	T1-hyperintensity, mild enhancement, T2-hyperintensity, fat suppression, DWI hyperintensity, extradural
Orakcioglu et al.	2008	7	Male	52 year-old	Right temporomesial	MRI	T1-hypointensity (nonhomogenous), T2-hyperintensity, no Gd enhancement
Sahoo et al.	2019	1	Male	42 year-old	lumbar dermoid	MRI	T1 and T2 hyperintense deposits along ventricular wall and T1, T2 hyperintense intramedullary lesion at the lumbar region with multiple fat deposits along the spinal axis.
Zhang et al.	2024	1	Male	28 year-old	left frontotemporal region	MRI	Lesion with high signal areas on T1- and T2-weighted images, irregular hyperintensity on DWI, and dissemination of cyst contents in the Sylvian fissures showing high signal on both T1 and T2.
Karabulut N et al.	2000	1	Male	26 year-old	interpeduncular cistern	MRI	T1 hyperintense fat droplets in the basal cisterns and ventricles, often with fat–fluid levels and associated hydrocephalus.
Reed et al.	2024	1	Female	74 year-old	Lateral ventricles and basal cisterns	MRI	T1 weighted and FLAIR MRI showed hyperintense lesions “floating” on top of the CSF in the lateral ventricles
Boissonot L et al.	1986	1	Female	22 year-old	Intraventricular region.	MRI	Low density areas disseminated on the cortical surface and intra-ventricular fat level.

Compilation of cases from the literature:

A total of 12 patients described in 6 articles published between 1986 and 2024 were analyzed. Most of the patients were male (66.7%), with ages ranging from 16 to 74 years. The most frequently involved anatomical locations included the intraventricular region, basal cisterns, suprasellar area, and Sylvian fissures. Some cases demonstrated multifocal involvement, including dissemination along the spinal axis or extension to regions such as Meckel’s cave and the interpeduncular cistern.

Magnetic resonance imaging (MRI) was the diagnostic modality of choice. A common imaging pattern consisted of lesions showing T1- and T2-weighted hyperintensity, often with heterogeneous signal characteristics and the presence of fatty components. Diffusion-weighted imaging (DWI) and fat suppression sequences were particularly helpful in detecting intralesional fat and in characterizing the extent of dissemination. Two additional articles identified in the literature search were not included in this analysis because the full texts were not available.

Discussion

Intracranial dermoid cysts are benign, slowly-growing tumors derived from ectodermal remnants, resulting from the inclusion of the skin along the lines of embryonic closure at the time of neural tube closure (3rd-5th week of embryogenesis) and have a capacity to grow, due to secretion of dermal elements [16,17]. Although typically asymptomatic and incidentally discovered, their rupture can lead to a wide range of neurological symptoms depending on the location and extent of the leakage [16]. While rupture is relatively uncommon, it can result in serious complications such as chemical meningitis, vasospasm, and cerebral infarction.

Dermoid cysts are significantly less common than epidermoid cysts and tend to present in a younger patient population. The rupture of an intracranial dermoid cyst is a rare event, primarily due to its thick, protective capsule. While rupture is most often spontaneous, traumatic rupture is exceedingly uncommon [18]. In a 12-year retrospective study by Esquenazi, ruptured dermoid cysts accounted for only 0.18% of all surgically treated intracranial tumors [19]. When rupture does occur, it poses significant clinical challenges, as the release of lipid-rich contents into the subarachnoid or ventricular spaces can lead to severe complications such as chemical meningitis, vasospasm, or hydrocephalus [20].

The radiologic evaluation of ruptured dermoid cysts remains a critical aspect of diagnosis, which are most commonly located in the midline, specifically in the suprasellar cistern and the posterior fossa. Imaging features of the appearance of both unruptured and ruptured dermoid cysts on CT and MRI play a pivotal role, primarily due to their high lipid content [21]. The classic CT findings include fat-fluid levels in the ventricles or subarachnoid spaces, low attenuation, with the fat content of the cyst visible, usually circumscribed [20]. In addition, frequently the dermoid wall contains calcifications and partially enhances following the administration of CT-iodinated contrast material [18].

MRI, conversely, provides more detailed insights for identifying the site of dermoid tumors and the involvement of nearby tissues [21,22]. The radiological features of these lesions typically present hyperintensity on T1-weighted images due to the high lipid content. The fat appears hyperintense to hypointense on T2-weighted images and other sequences. Importantly, MRI also has the advantage of detecting subtle signs of rupture, such as the presence of fat within the sulci or ventricles, which may not be as evident on CT scans. Fluid-attenuated inversion recovery (FLAIR) sequence demonstrates subtle sulcal hyperintensity, T2 GRE/SWI sulcal “bloom” and inherently present “fat suppressed” with low signal from the fatty components presented secondary to the ruptured dermoid cyst or the globules of fat in the subarachnoid space [20].

On the other hand, angiography can show the displacement or encasement of blood vessels near the tumor, such as magnetic resonance angiography (MRA) or computed tomography angiography (CTA) [22].

In our case, the patient’s headache could be attributed to meningoencephalitis, compounded by the mass effect of the lesion. According to the literature, headache is one of the main symptoms associated with dermoid cyst rupture. The intensity of the headache varies depending on the cyst’s size and location, but it can occur anywhere within the cranium, with or without signs of meningeal irritation. This headache arises secondary to intracranial lesions and is caused by direct irritation of pain-sensitive structures within the skull. These structures include the arteries within the circle of Willis, the venous sinuses, cranial nerves, dura mater, and dural arteries [23,10]. The literature reports an incidence of chemical meningitis in ruptured dermoid cysts of up to 7% [17]. The presence of disseminated fat droplets in the subarachnoid space or ventricles on neuroimaging is considered to be diagnostic of a ruptured dermoid cyst. Symptom onset may occur between 5 months and 6.5 years post-rupture, as the irritative effects of the leaked contents typically require time to develop. The arthropod bite was a circumstantial event that potentially contributed to the patient's clinical presentation, however, it is mentioned primarily to rule out other possible causes and emphasize that it was unlikely to be the direct cause of the symptoms [11].

Close differential diagnoses for intracranial dermoid cysts include epidermoid cysts, lipomas, teratomas, and craniopharyngiomas [23]. Rupture may result in dissemination of lipid material into the subarachnoid spaces and ventricles, with intraventricular fat fluid levels providing an important diagnostic clue [24]. Intracranial lipid droplets may also originate from ruptured spinal dermoid cysts, with migration through cerebrospinal fluid pathways [[13], [14]]. Disseminated cyst contents can interfere with cerebrospinal fluid circulation or absorption and lead to hydrocephalus [[14], [15]].

Surgical resection is the primary treatment, as it effectively reduces the risk of recurrence, which is already low for these benign lesions [[12], [25]]. Complete excision of the cyst, including its capsule, is ideal; however, in cases where the capsule firmly adheres to critical neurovascular structures, subtotal resection is recommended to minimize the risk of neurological injury [[12], [25]]. Furthermore, incomplete removal rarely leads to recurrence or malignant transformation [25]. Residual lipid material within the subarachnoid spaces can persist for years postoperatively, often without causing symptoms, further supporting the safety and efficacy of a conservative surgical approach when necessary [[12], [25]].

In our patient, conservative management was chosen, consisting of close neurological monitoring and antiviral therapy, as the clinical and laboratory findings were consistent with herpes zoster meningoencephalitis. Surgical intervention was deferred given the stability of the lesion and the favorable clinical response to medical treatment.

Conclusion

Intracranial epidermoid cysts are rare, typically asymptomatic entities. Although uncommon, their rupture can result in severe and nonspecific neurological symptoms. Radiologists play a pivotal role, imaging studies, particularly, computed tomography (CT) and magnetic resonance imaging (MRI) reveal characteristics features that facilitate accurate diagnosis and lesion identification, thereby helping to prevent further complications and inform appropriate treatment strategies. While surgical resection remains the treatment of choice, conservative management may be appropriate in selected cases, especially when the lesion is stable and the clinical symptoms are attributable to other concurrent conditions, as demonstrated in the present case.

Limitations

This case report has inherent limitations, primarily due to its descriptive and focus on a single patient. While the incidental finding of a ruptured intracranial dermoid cyst in the context of an unrelated clinical presentation provides valuable insight, it limits the generalizability of the conclusions. Further studies with larger patient populations are needed to better understand the clinical implications, optimal management strategies, and long-term outcomes of ruptured intracranial dermoid cysts.

Author contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by

Patient consent

Complete written informed consent was obtained from the patient for the publication of this study and accompanying images.