Ruptured intracranial dermoid cyst: A rare case

INTRODUCTION

Intracranial dermoid cystic tumors account for <1% of all intracranial masses. Dermoid cysts are congenital, non-neoplastic ectodermal inclusion cysts, containing various ectodermal derivatives, such as apocrine glands, sweat glands, sebaceous glands, hair follicles, squamous epithelium, and, occasionally, even teeth. The rupture of intracranial dermoid cysts is considered rare, though the exact frequency of this occurrence remains unclear. The rupture of an intracranial dermoid cyst can occur spontaneously or, more commonly, as a result of trauma; however, rupture itself remains an uncommon event. This rupture often leads to the development of aseptic chemical meningitis, resulting from the profound irritative effects of the disseminated cholesterol debris. This condition typically presents with symptoms such as headaches and, in many cases, seizures.^[1]

We present the case of a 38-year-old patient who underwent surgery due to a ruptured dermoid cyst in the region of the Sylvian fissure.

CASE REPORT

We present a case of a 38-year-old male patient who experienced an epileptic seizure 4 months before admission and examination at our facility. The patient had no prior medical conditions and was previously in good health. His personal medical history was unremarkable, and his family history was non-contributory. Following the seizure, he was evaluated at another hospital, where a computed tomography (CT) scan of the brain indicated a lesion that was initially misinterpreted as an arachnoid cyst in the region of the anterior pole of the right temporal lobe, and thus, no therapy or follow-up was prescribed, with the patient only advised to consult a neurologist, which he did not do before presenting at our institution. After experiencing another epileptic seizure of the generalized tonic-clonic type, the patient was examined at our facility. On examination, the patient was asymptomatic and showed no signs of illness; the neurological findings were completely normal. Another CT scan of the brain showed a lesion in the temporo-frontal area on the right side [Figure 1a], which was further investigated with magnetic resonance imaging (MRI) [Figure 1b-d]. The MRI confirmed a lesion in the region of the anterior pole of the right temporal lobe, extending through the Sylvian fissure into the frontal lobe, reaching the gyrus rectus where it exerts compression. The lesion is well-defined with dimensions of approximately 5.1 × 3 × 4 cm [latero-lateral (LL) × anteroposterior (AP) × craniocaudal (CC)]. In the T1 sequence, the lesion shows areas of varying signal intensity, with no significant enhancement following contrast administration. In the T2 sequence, the lesion demonstrates mixed signal characteristics, indicative of differing tumor components. It is clearly observed that this tumor mass is pushing the middle meningeal artery posteriorly. MRI images also confirmed the presence of fat locules bilaterally in the brain sulci (subarachnoid space), consistent with fat from a ruptured dermoid cyst, which is almost pathognomonic feature.

Close

Figure 1:

(a) A brain computed tomography scan showing a lesion in the region of the anterior pole of the right temporal lobe, involving the adjacent frontal lobe, predominantly of fat tissue density with areas of calcification. (b) A brain magnetic resonance imaging (MRI) of the patient in the T1 sequence with contrast administration showing the lesion with mixed signal intensity. (c) A brain MRI in the T2 sequence clearly showing a lesion that compresses the right middle cerebral artery. (d) A brain MRI of the patient in the T1 sequence. The arrows point to cholesterol fat droplets in the brain sulci (subarachnoid space).

Export to PPT

Based on the correlation of the clinical presentation, disease progression, and neuroradiological findings, surgical treatment was indicated. The patient underwent elective surgery, where a near-total resection of the tumor was performed. A Sylvian split was initially performed, followed by access to the tumor [Figure 2a]. The tumor appeared soft and whitish and contained a large number of hair-like structures [Figure 2b]. After an internal tumor decompression, which was easily aspirated and drawn into the aspirator, a thick, pearly-white tumor capsule was clearly visible. In some areas, the capsule thickness reached up to half a centimeter and was resected from its attachment to the frontal and temporal lobes. In smaller areas near the middle cerebral artery, a few adherent fragments of the capsule remained, which were shrunk and cauterized with a bipolar cautery; thus, nearly total resection was achieved [Figure 2c]. The specimen was sent for histopathological examination, which confirmed the diagnosis of a dermoid cast. The post-operative course was uneventful. The patient recovered well, and the follow-up CT scan of the brain showed satisfactory postoperative results, with focal cholesterol deposits at multiple sites in the brain sulci (subarachnoid space), without clinical significance. The patient was discharged from the hospital on the 5^th post-operative day. Three months after the surgery, the patient is doing well, without any complaints, with a normal neurological examination, and no signs of tumor recurrence.

Close

Figure 2:

(a) Intraoperative findings before the Sylvian fissure split. The arrow points to the yellowish-enhanced cortex beneath which the tumor was accessed. (b) The portion of the tumor showing hair-like structures and hard areas resembling dental enamel. (c) The cavity remaining after the resection of the tumor and its capsule.

Export to PPT

DISCUSSION

Intracranial dermoid cystic tumors are uncommon, benign lesions, and typically exhibit slow growth. They are most often located in the sellar or parasellar regions, as well as the frontonasal area, and are often situated near the base of the skull. These dermoid cysts can also be located in the posterior cranial fossa, either within or near the fourth ventricle. In addition, they may be found in the pineal gland region, along with several other less common intracranial locations.^[2] We present a case involving a large dermoid cyst located in a relatively rare site, specifically in the region of the Sylvian fissure and the anterior part of the temporal lobe. This unusual location initially led to a misdiagnosis by the emergency medicine physician, who mistakenly diagnosed it as an arachnoid cyst in a typical temporal lobe location.

Dermoid cysts are typically asymptomatic but may become symptomatic, particularly when they rupture. It is thought that the rupture occurs due to the accumulation of hair and sebaceous material from the internal dermal components, which increases intracystic pressure. However, trauma can also precipitate rupture. Although the rupture of intracranial dermoid cysts is relatively rare, the exact frequency of this event remains unclear. In one neurosurgical study of central nervous system tumor resections, ruptured dermoid cysts accounted for only 0.18% of all tumors removed over a 12-year period.^[3] The clinical symptoms following the rupture of dermoid cysts can be attributed to two primary mechanisms. One is the impact of the lesion on adjacent structures, while the other involves aseptic meningitis, vasospasm, and nerve damage, due to the irritation of the surrounding meninges, blood vessels, and nerves by the spilled contents.^[1] Thus, the rupture of the cyst typically presents with a sudden onset of headache, seizures, or more severe complications such as chemical meningitis, vasospasm, and cerebral infarction.^[4] In our patient, the rupture manifested with a seizure, which recurred after a short period, prompting further investigation. Intracranial dermoid cyst rupture displays characteristic imaging features. CT scans often reveal a mixed-density area, particularly below the cerebellar vermis. MRI, however, provides a more detailed evaluation, confirming the nature of the lesion through characteristics such as lipid signals, absence of enhancement, and limited spread. Detailed imaging assessment is essential for guiding appropriate treatment strategies.^[5,6] In our case, the CT and MRI scans strongly suggested the presence of a ruptured dermoid cyst with a compressive effect on the brain parenchyma.

Surgical removal of the cystic contents and tumor capsule is the primary treatment approach. In cases of rupture, fat droplets in the subarachnoid space are frequently observed and can be aspirated and irrigated. However, some of the cystic contents, including fat droplets, are likely to remain dispersed. Given the rarity of the tumor and the variability of postoperative outcomes, the long-term effects of the remaining fatty deposits remain uncertain; however, it is believed that these remaining deposits are rarely symptomatic or may lead to tumor recurrence.^[6,7] In our case, a near-total resection was performed, with the majority of the cystic component successfully removed. In addition, the capsule was mostly excised from the frontal and temporal lobes, leaving behind small areas of the membrane that remained adherent to vascular structures, which is why they were intentionally not resected. Due to the small remnants of the capsule and the presence of cholesterol deposits diffusely in the subarachnoid space, regular follow-up has been recommended.

CONCLUSION

This case highlights the exceptionally rare presentation of a ruptured intracranial dermoid cyst and emphasizes the importance of including such lesions in the differential diagnosis of brain tumors and cystic brain lesions.