2026 年 13 巻 p. 385-388
Intracranial dermoid cysts are rare congenital lesions of ectodermal origin. Those arising in the Sylvian fissure are particularly rare, and rupture in this location has only infrequently been reported. A 54-year-old woman presented with a persistent headache after minor head trauma. Magnetic resonance imaging demonstrated a well-circumscribed 30-mm lesion in the left Sylvian fissure with heterogeneous hyperintensity on T1-weighted images. Multiple disseminated hyperintense droplets within the basal cisterns suggested cyst rupture. The patient underwent microsurgical resection via a trans-Sylvian approach. Intraoperatively, the cyst wall was partially deficient and adherent to the surrounding vessels. Owing to dense calcification of the wall and firm adhesion to adjacent neurovascular structures, the capsule was left in place, and the cyst contents were evacuated and curetted, followed by thorough irrigation. Histopathological examination confirmed a dermoid cyst. The postoperative course was uneventful, and no recurrence has been observed during 9 months of follow-up. Ruptured dermoid cysts in the Sylvian fissure are exceedingly rare. Recognition of disseminated lipid droplets is crucial for diagnosis, and safe resection with preservation of critical neurovascular structures is essential for favorable outcomes.
Intracranial dermoid cysts are rare, accounting for less than 1% of all intracranial tumors. They are benign congenital lesions derived from ectodermal inclusion during neural tube closure.1) These lesions are typically located along the midline, most commonly in the sellar and parasellar regions and the posterior fossa.2) Dermoid cysts arising in the Sylvian fissure are exceedingly rare. Upon rupture, cyst contents may disseminate into the subarachnoid space, potentially resulting in chemical meningitis, seizures, or hydrocephalus.3,4) This unusual presentation can make preoperative diagnosis difficult. Herein, we present a rare case of a ruptured dermoid cyst in the Sylvian fissure and provide a review of the relevant literature.
A 54-year-old woman presented with a headache after sustaining a fall-related head injury. Four days later, she visited a local clinic, where computed tomography revealed a hypodense mass with peripheral wall calcification in the left Sylvian fissure (Figure 1A). Subsequent magnetic resonance imaging (MRI) demonstrated a well-circumscribed 30-mm lesion in the left Sylvian fissure with heterogeneous hyperintensity on T1-weighted images (Figure 1B). Multiple disseminated T1-hyperintense droplets were observed in the basal cisterns, suggesting rupture of a dermoid cyst. She continued to receive symptomatic treatment for headache at the local clinic and was referred to our institution approximately 3 months after the injury. On admission, she exhibited no apparent neurological deficits or signs of meningitis. Based on the radiological findings, a ruptured dermoid cyst in the Sylvian fissure was diagnosed, and surgical treatment was planned to prevent further dissemination of cyst contents. A left frontotemporal craniotomy via a trans-Sylvian approach was performed. Intraoperatively, a yellowish mass with a partially calcified capsule was identified within the left Sylvian fissure. Focal disruption of the cyst wall was noted, with leakage of cyst contents into the surrounding cisterns. After enlargement of the capsular opening using a high-speed drill, the cyst contents were carefully evacuated (Supplementary Figure 1). Because the calcified capsule was firmly adherent to the middle cerebral artery, it was intentionally left in place to avoid vascular injury. Histopathological examination revealed keratinous debris, fibrous connective tissue, and hair elements, confirming the diagnosis of dermoid cyst (Supplementary Figure 2). The postoperative course was uneventful, with no neurological deficits. Follow-up MRI demonstrated no evidence of recurrence (Figure 1C).
Computed tomography demonstrated a well-demarcated hypodense mass with wall calcification in the left Sylvian fissure (A). T1-weighted MRI revealed a 30-mm lesion in the left Sylvian fissure with heterogeneous signal (B). Multiple disseminated T1-hyperintense droplets were noted in the basal cisterns, compatible with rupture of a dermoid cyst. Postoperative MRI demonstrated a marked reduction of the cyst contents without evidence of recurrence (C).
MRI: magnetic resonance imaging
Dermoid cysts of the Sylvian fissure are extremely rare, with only 15 cases reported in the literature to date, including the present case (Table 15-17)). These cases can be broadly classified into ruptured5-8,15,16) and non-ruptured9-14,17) lesions, which appear to differ in their clinical and radiological characteristics. Non-ruptured lesions usually present as well-circumscribed masses without dissemination into the subarachnoid space. Their clinical manifestations are often mild or nonspecific, and MRI typically demonstrates homogeneous T1 hyperintensity confined to the lesion. In previously reported non-ruptured cases, gross total resection was achieved in most patients, possibly because the capsule remained intact and showed limited adhesion to adjacent neurovascular structures.9-14,17)
Summary of Cases of Dermoid Cysts Arising in the Sylvian Fissure Reported in the Literature
| Author (year) | Age/sex | Rupture | Clinical presentation | Treatment | |
|---|---|---|---|---|---|
| F: female; GTR: gross total resection; M: male; STR: subtotal resection | |||||
| 1 | Shinoyama et al (2002) 5) | 22F | Yes | Headache | GTR |
| 2 | Chen et al (2005) 6) | 61M | Yes | Acute headache, intratumoral hemorrhage | GTR |
| 3 | Sugano et al (2006) 7) | 15M | Yes | Seizure | GTR |
| 4 | Liu et al (2008) 8) | 57M | Yes | Seizure | STR |
| 5 | Liu et al (2008) | 57M | Yes | Headache | STR |
| 6 | Kocaeli et al (2009) 9) | 58M | No | Dysgeusia | GTR |
| 7 | Akhaddar et al (2010) 10) | 50F | No | Chronic headache, hemiparkinsonism | GTR |
| 8 | Li et al (2012) 11) | 14M | No | Seizure | GTR |
| 9 | Schneider et al (2012) 12) | 11M | No | Headache | GTR |
| 10 | Kato et al (2014) 13) | 8F | No | Asymptomatic | GTR |
| 11 | Anand et al (2014) 14) | 30F | No | Headache | GTR |
| 12 | Skovrlj et al (2014) 15) | 51M | Yes | Progressive visual loss after rupture | GTR |
| 13 | Garces et al (2016) 16) | 61F | Yes | Seizure | GTR |
| 14 | Haider et al (2016) 17) | 43M | No | Asymptomatic | Conservative treatment |
| 15 | Present case | 54F | Yes | Headache | STR |
By contrast, ruptured dermoid cysts are characterized by dissemination of cyst contents into the subarachnoid space, most readily recognized as scattered T1-hyperintense droplets on MRI. These lipid droplets may spread along cerebrospinal fluid pathways and occasionally induce chemical meningitis or other inflammatory reactions. Headache is the most common presenting symptom,5,6,8) although some patients present with chemical meningitis or seizures.7,8,16) Intraoperatively, rupture of the cyst wall and inflammatory adhesions to adjacent structures, particularly the middle cerebral artery, are frequently encountered, which may preclude complete removal of the capsule.8)
Rupture of a dermoid cyst is uncommon and is generally considered to occur spontaneously, possibly as a result of cyst enlargement, capsular fragility, or inflammatory change.8) Several reports have suggested that trauma may trigger rupture;18-20) however, a definite causal relationship has not been established. In the present case, although the patient's symptoms developed after a head injury, the relationship remains speculative. Reported surgical outcomes for Sylvian fissure dermoid cysts have generally been favorable. Most patients experienced symptomatic improvement, and no recurrence has been documented during follow-up, even after subtotal resection.8) However, the number of reported Sylvian fissure cases remains very small, and the follow-up periods are relatively limited. Because intracranial dermoid cysts are slow-growing lesions, late regrowth after incomplete excision may become apparent only after many years. Yaşargil et al.21) emphasized that residual capsule after incomplete removal of intracranial dermoid and epidermoid tumors may be associated with delayed recurrence, underscoring the importance of long-term follow-up. In addition, malignant transformation of intracranial epithelial cysts is exceptionally rare, but a recurrent dermoid cyst with transformation into squamous cell carcinoma after subtotal resection and long-term follow-up has been reported.22) Therefore, when the capsule is densely adherent to critical neurovascular structures, leaving the residual capsule in place may be a reasonable strategy, as preservation of neurological function should take priority over radical excision; however, such patients require careful long-term MRI surveillance.11,21,22) In patients who are asymptomatic without evidence of rupture, careful radiological observation may be appropriate, particularly when dense adhesion is anticipated. In contrast, when rupture is suspected, the risk of inflammatory complications supports prompt surgical treatment with maximal safe resection and thorough irrigation.
In the present case, dense calcification and firm adhesion of the capsule to the middle cerebral artery prevented safe capsular removal, and surgery was limited to evacuation and curettage of the cyst contents. Nevertheless, the postoperative course was uneventful, and no recurrence has been observed. This case suggests that internal decompression and irrigation alone may provide favorable outcomes in selected patients and supports a surgical strategy that prioritizes safety over complete excision.
Ruptured dermoid cysts of the Sylvian fissure are rare but should be included in the differential diagnosis when disseminated T1-hyperintense droplets are identified in the subarachnoid space. In these cases, surgical management should prioritize preservation of neurological function, and leaving adherent capsular remnants in place may be an acceptable strategy. Favorable outcomes may be achieved even with limited surgery consisting of cyst evacuation and thorough irrigation.
All authors have no conflict of interest.
Informed consent was obtained from the patient for publication of this case report and accompanying images.
