Effect of newly developed scissors-attached micro-forceps on the recipient clamp time and occurrence of anastomotic site infarction after bypass surgery for moyamoya disease.

Introduction: This study aimed to examine the effect of newly developed scissors-attached micro-forceps in superficial temporal artery-to-middle cerebral artery (STA-MCA) anastomosis for moyamoya disease (MMD). Materials and methods: Of 179 consecutive STA-MCA anastomoses on 95 hemispheres of 71 MMD patients at the University of Fukui Hospital between 2009 and 2023, 49 anastomoses on 26 hemispheres of 21 patients were enrolled in this retrospective cohort clinical trial intraoperative indocyanine green video-angiography did not demonstrate bypass patency in three anastomoses in two patients who were excluded. Twenty-one anastomosis in 19 hemispheres of 16 patients were performed using the conventional micro-forceps (conventional group, CG), and 25 anastomoses in 22 hemispheres of 19 patients were performed using scissors-attached micro-forceps (scissors group, SG). A small infarction near the anastomotic site detected using postoperative diffusion-weighted imaging was defined as anastomotic site infarction (ASI). Factors affecting the occurrence of ASI were examined by univariate, logistic regression, and receiver operating curve (ROC) analysis. Results: There were no significant differences in clinical parameters such as age, sex, number of sacrificed branches, number of sacrificed large branches, and number of sutures between the CG and SG. However, the clamp time and occurrence of ASI were significantly lower in the SG than in the CG. Logistic regression analysis revealed that the clamp time was the only significant factor predicting the occurrence of ASI. A receiver operating curve analysis also revealed that the clamp time significantly predicted the occurrence of ASI (area under the curve, 0.875; cutoff value, 33.2 min). Conclusion: The newly developed scissors-attached micro-forceps could significantly reduce the clamp time and occurrence of ASI in STA-MCA anastomosis for MMD.

Single-Cell Analysis of Unidirectional Migration of Glioblastoma Cells Using a Fiber-Based Scaffold.

Glioblastoma (GBM) is a malignant incurable brain tumor in which immature neoplastic cells infiltrate brain tissue by spreading along nerve fibers. The aim of the study was to compare the migration abilities of glioma cells with those of other cancer cells and elucidate the migratory profiles underlying the differential migration of glioma cells using a fiber-based quantitative migration assay. Here, wound healing and transwell assays were used to assess cell mobility in four cell lines: U87-MG glioblastoma cells, MDA-MB-231 breast cancer cells, HCT116 colorectal cancer cells, and MKN45 gastric cancer cells. We also assessed cell mobility using a fiber model that mimics nerve fibers. Time-lapse video microscopy was used to observe cell migration and morphology. The cytoskeleton arrangement was assessed in the fiber model and compared with that in the conventional cell culture model. The conventional evaluation of cell migration ability revealed that the migration ability of breast cancer and glioblastoma cell lines was higher than that of colon cancer and gastric cancer cell lines. The fiber model confirmed that the glioblastoma cell line had a significantly higher migration ability than other cell lines. Tubulin levels were significantly higher in the glioblastoma cells than in other cell lines. In conclusion, the developed fiber-based culture model revealed the specific migratory profile of GBM cells during invasion.

Nanofiber-Mâché Hollow Ball Mimicking the Three-Dimensional Structure of a Cyst.

The occasional malignant transformation of intracranial epidermoid cysts into squamous cell carcinomas remains poorly understood; the development of an in vitro cyst model is urgently needed. For this purpose, we designed a hollow nanofiber sphere, the "nanofiber-mâché ball." This hollow structure was fabricated by electrospinning nanofiber onto alginate hydrogel beads followed by dissolving the beads. A ball with approximately 230 mm3 inner volume provided a fibrous geometry mimicking the topography of the extracellular matrix. Two ducts located on opposite sides provided a route to exchange nutrients and waste. This resulted in a concentration gradient that induced oriented migration, in which seeded cells adhered randomly to the inner surface, formed a highly oriented structure, and then secreted a dense web of collagen fibrils. Circumferentially aligned fibers on the internal interface between the duct and hollow ball inhibited cells from migrating out of the interior, similar to a fish bottle trap. This structure helped to form an adepithelial layer on the inner surface. The novel nanofiber-mâché technique, using a millimeter-sized hollow fibrous scaffold, is excellently suited to investigating cyst physiology.

[Optic Neuropathy Secondary to Compression by the Internal Carotid Artery Concomitant with an Inflammatory Granuloma:A Case Report].

A 77-year-old man presented with a 6-month history of progressive right optic neuropathy secondary to compression by the ipsilateral internal carotid artery(ICA). We performed anterior clinoidectomy and optic canal unroofing. Subsequently, we wrapped the ICA with a polytetrafluoroethylene tape, pulled the vessel laterally, and sutured the tape to the dura mater at the anterior skull base for optimal decompression. An inflammatory mass lesion was observed around the ICA, which led to further compression of the optic nerve. Histopathological examination of the resected specimen showed an inflammatory granuloma. The patient's visual field deficit showed partial improvement postoperatively. Transposition using a tape might be an effective surgical alternative for compressive optic neuropathy.

[Progressive Multifocal Leukoencephalopathy Associated with HIV Infection Diagnosed by Brain Biopsy with Repeated Negative PCR Testing of CSF JC Virus DNA].

A 36-year-old man with human immunodeficiency virus (HIV) infection was admitted to our hospital due to progressive ataxia. Brain MRI demonstrated high-signal intensity in the white matter of the right parietal lobe and left cerebellar hemisphere on T2-weighted images. Despite antiretroviral therapy, as his clinical symptoms worsened and MRI lesions gradually increased with the appearance of gadolinium-enhanced lesions, immune reconstitution inflammatory syndrome by progressive multifocal leukoencephalopathy (PML) associated with HIV infection was suspected. However, JC virus (JCV) in the cerebrospinal fluid (CSF) was undetectable by DNA PCR twice. Therefore, biopsy of the right parietal lobe was performed. JCV DNA was detected by PCR using the biopsy sample. JC viral protein was also identified by immunohistochemistry. Brain biopsy should be considered for the clinical diagnosis of PML when CSF JCV is negative on repeated DNA PCR. (Received September 20, 2019; Accepted January 14, 2020; Published May 1, 2020).

[Vestibular Schwannoma Surgery with Continuous Intraoperative Monitoring of Evoked Facial Nerve Electromyograms].

Preservation of facial nerve function is crucial during vestibular schwannoma surgery. Here, we report the utility of continuous intraoperative monitoring of evoked facial nerve electromyograms(EMGs)for preservation of facial nerve function during vestibular schwannoma surgery. A 64-year-old man presented with left ear hearing disturbance. CT and MRI revealed a tumor mass(4cm)with cyst formation in the left cerebellopontine angle. Microsurgical removal was performed with continuous intraoperative monitoring of evoked facial nerve EMGs. An electrode with Ag wire and absorbable gelatin sponge, which we developed, was used for continuous monitoring. It could be placed and fixed more easily on the root exit zone of the facial nerve than the previously reported electrodes and provide reliable information during surgery. The tumor mass could be removed safely without inducing facial nerve palsy. Continuous intraoperative monitoring of evoked facial nerve EMGs with this newly developed electrode could facilitate successful schwannoma surgery.

Relationship between gait parameters and MR imaging in idiopathic normal pressure hydrocephalus patients after shunt surgery.

BACKGROUND: A few previous studies have reported a change in gait motion in idiopathic normal pressure hydrocephalus (iNPH) patients after shunt surgery compared with before shunt surgery; however, there has been no detailed quantitative investigation of gait, including kinetic and kinematic parameters. Furthermore, the relationship between gait parameters and magnetic resonance (MR) imaging has not been confirmed. RESEARCH QUESTION: We investigated the gait motion in patients with iNPH, and evaluated the relationship between kinetic gait parameters and MR imaging before and after shunt surgery. METHODS: The subjects were 12 patients with iNPH who could walk 10 m without aids. A three-dimensional motion analysis system was used to obtain the spatiotemporal, kinetic, and kinematic parameters before and after surgery. Relationships between each gait parameter and MR imaging were assessed. RESULTS: The post-shunt walking speed and step length were increased compared with pre-shunt values. The post-shunt evaluation showed increased range of motion of the hip, knee, and ankle joints in the sagittal plane during the gait cycle. The peak flexion moment of the hip during the stance phase was greater after shunt surgery. The improvement rate of the Evans index was significantly correlated with the improvement rate of walking speed, and the total ranges of motion of the hip and ankle joints in the sagittal plane. SIGNIFICANCE: The propulsive force of the hip and ankle joints was regained after shunt surgery. Normalization of the Evans index could predict improvement in propulsive force after shunt surgery in iNPH.

Pathological examination of cerebral amyloid angiopathy in patients who underwent removal of lobar hemorrhages.

Cerebral amyloid angiopathy (CAA) is a degenerative disorder characterized by amyloid-ß (Aß) deposition in the brain microvessels. CAA is also known to contribute not only to cortical microbleeds but also lobar hemorrhages. This retrospective study examined CAA pathologically in patients who underwent direct surgeries for lobar hemorrhage. Thirty-three patients with lobar hemorrhage underwent open surgery with biopsy from 2007 to 2016 in our hospital. Cortical tissues over hematomas obtained surgically were pathologically examined using hematoxylin, eosin stain, and anti-Aß antibody to diagnose CAA. We also investigated the advanced degree of CAA and clinical features of each patient with lobar hemorrhage. In the 33 patients, 4 yielded specimens that were insufficient to evaluate CAA pathologically. Twenty-four of the remaining 29 patients (82.8%) were pathologically diagnosed with CAA. The majority of CAA-positive patients had moderate or severe CAA based on a grading scale to estimate the advanced degree of CAA. About half of the CAA-positive patients had hypertension, and four took anticoagulant or antiplatelet agents. In five patients who were not pathologically diagnosed with CAA, one had severe liver function disorder, three had uncontrollable hypertension, and one had no obvious risk factor. Our pathological findings suggest that severe CAA with vasculopathic change markedly contributes to lobar hemorrhage. The coexistence of severe CAA and risk factors such as hypertension, anticoagulants or antiplatelets may readily induce lobar hemorrhage.

Mitogen-activated protein kinase in gliosis and pilocytic astrocytoma.

Pilocytic astrocytoma (PA), featuring activation of the mitogen-activated protein kinase (MAPK) pathway, is the most common tumor of the pediatric central nervous system. However, it remains unknown whether MAPK activation is present in the reactive gliosis of non-neoplastic lesions. Therefore, we investigated the expression of MAPK in reactive gliosis associated with cavernous angiomas. Immunohistochemical expression and the extent of BRAF, ERK, p38, and JNK were investigated in 10 patients with gliosis surrounding cavernous angiomas (GS group) and 10 patients with PA (PA group). Evaluation of these parameters was scored as 0, none; 1, scarce; 2, moderate; 3, global. In the GS group, histopathologic features of PA (piloid cells, Rosenthal fibers, microcysts with eosinophilic granular bodies) were identified. Expression of ERK, and p38 was shown in all patients in the GS and PA group. Expression of BRAF was identified in 5 patients (50%) in the GS group and in 8 (80%) in the PA group. The mean score of BRAF expression in the PA group was significantly higher than that in the GS group (p = 0.019). Reactive gliosis may resemble PA in histological findings and MAPK activation. Therefore, PA could be indistinguishable from reactive gliosis with classic histopathologic and/or immunohistochemical methods.
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Spinal endoscopy combined with selective CT myelography for dural closure of the spinal dural defect with superficial siderosis: technical note.

The authors describe a new procedure to detect the tiny dural hole in patients with superficial siderosis (SS) and CSF leakage using a coronary angioscope system for spinal endoscopy and selective CT myelography using a spinal drainage tube. Under fluoroscopy, surgeons inserted the coronary angioscope into the spinal subarachnoid space, similar to the procedure of spinal drainage, and slowly advanced it to the cervical spine. The angioscope clearly showed the small dural hole and injured arachnoid membrane. One week later, the spinal drainage tube was inserted, and the tip of the drainage tube was located just below the level of the dural defect found by the spinal endoscopic examination. This selective CT myelography clarifies the location of the dural defect. During surgery, the small dural hole could be easily located, and it was securely sutured. It is sometimes difficult to detect the actual location of the small dural hole even with thin-slice MRI or dynamic CT myelography in patients with SS. The use of a coronary angioscope for the spinal endoscopy combined with selective CT myelography may provide an effective examination to assess dural closure of the spinal dural defect with SS in cases without obvious dural defects on conventional imaging.

Evaluation of the Use of Calcium Phosphate Cement for Aesthetic Neurosurgical Cranial Reconstruction.

OBJECTIVE: The objective of this article is to evaluate whether newly developed calcium phosphate cement (CPC), mounted around the titanium plates, is useful for aesthetic cranial reconstruction by using 2 methods. METHODS: The morphologic changes of CPC were observed in videos of 6 patients who had undergone cranial reconstruction with CPC during the first surgery and required second surgery. The facial aesthetic outcomes of 74 consecutive patients, more than 12 months after frontotemporal or bifrontal craniotomy and reconstruction with or without CPC, were evaluated. RESULTS: Observations of CPC changes were available 1 day, 2 weeks, 2 months, 5 months, 10 months, and 26 months after the first surgeries. CPC, applied superficially on the cranial surface, had not set sufficiently. CPCs, mounted thickly around the titanium plates and forming hydroxyapatite, were residual during the latter period. Comparison between the aesthetic reconstruction group (with CPC) and the simple reconstruction group (without CPC) showed that the objective bump detected by the investigator, and the subjective bump noticed by the patients themselves, were significantly more frequent in the simple reconstruction group. Comparison between the patients without an objective bump and the patients with an objective bump during the follow-up period showed that the proportion of patients after aesthetic cranial reconstruction with CPC was significantly higher in patients without an objective bump. Patients' characteristics, craniotomy procedure, use of a vascularized pericranial flap, and craniotomy-associated complications did not influence the objective bump significantly. CONCLUSIONS: Use of CPC was expected to bring better aesthetic outcomes after neurosurgical cranial reconstructions.

[Neurosurgical Outcomes of Intradural Extramedullary Spinal Tumors in 97 cases:Siberian Experience].

We retrospectively investigated the clinical presentation and outcome of patients with spinal intradural extramedullary tumors, which had been surgically treated. A total of 97 consecutive patients(32 males and 65 females;mean age, 48 years;range, 17-79 years)underwent surgery between 2004 and 2014 at Irkutsk State Medical Academy and affiliated hospitals. To determine presentation and outcomes associated with these tumors, we evaluated the waiting period before surgery, neurological symptoms including motor, sensory, urinary, and rectal dysfunction, modified McCormick scale, Macnab's outcome assessment of patient satisfaction, surgical procedure, tumor location, and histological diagnosis. The most frequent preoperative symptom was myelopathy(52.6%)at presentation, followed by radiculopathy(20.6%), and a combination of both(26.8%). Surgical intervention produced highly successful results, in which 77 of 97 cases showed neurological improvement. However, the symptoms were not completely reversed, and there was improvement only the equivalent to one grade in the modified McCormick scale for most patients. Surgical outcomes were not influenced by tumor location, extent of lamina resection, or histological diagnosis, but there was a correlation between greater patient improvement and a shorter waiting period before surgery. As such, we recommend early total resection for symptomatic spinal intradural extramedullary tumors.

Evaluation of obliteration of arteriovenous malformations after stereotactic radiosurgery with arterial spin labeling MR imaging.

PURPOSE: Complete obliteration of treated arteriovenous malformations (AVMs) can be diagnosed only by confirming the disappearance of arterio-venous (A-V) shunts with invasive catheter angiography. The authors evaluated whether non-invasive arterial spin labeling (ASL) magnetic resonance (MR) imaging can be used to diagnose the obliteration of AVMs facilitate the diagnosis of AVM obliteration after treatment with stereotactic radiosurgery (SRS). MATERIAL AND METHODS: Seven patients with a cerebral AVM treated by SRS were followed up with ASL images taken with a 3T-MR unit, and received digital subtraction angiography (DSA) after the AVM had disappeared on ASL images. Three patients among the seven received DSA also after the postradiosurgical AVM had disappeared on conventional MR images but A-V shunt was residual on ASL images. Four patients among the seven received contrast-enhanced (CE) MR imaging around the same period as DSA. RESULTS: ASL images could visualize postradiosurgical residual A-V shunts clearly. In all seven patients, DSA after the disappearance of A-V shunts on ASL images demonstrated no evidence of A-V shunts. In all three patients, DSA after the AVM had disappeared on conventional MR images but not on ASL images demonstrated residual A-V shunt. CE MR findings of AVMs treated by SRS did not correspond with DSA findings in three out of four patients. CONCLUSIONS: Findings of radiosurgically treated AVMs on ASL images corresponded with those on DSA. The results of this study suggest that ASL imaging can be utilized to follow up AVMs after SRS and to decide their obliteration facilitate to decide the precise timing of catheter angiography for the final diagnosis of AVM obliteration after SRS.

[A Case of Subcortical Intracerebral Hemorrhage Caused by Underlying Oligodendroglioma Diagnosed through Long-Term Follow-Up].

We report on a case of an oligodendroglioma that caused intracerebral hemorrhage, which was diagnosed by long-term follow-up. An 82-year-old man with underlying hypertrophic cardiomyopathy presented with weakness in the right upper extremity. Computed tomography and magnetic resonance imaging(MRI)showed intracerebral hemorrhage and focal brain edema. Since there was a discrepancy between hematoma and focal brain edema, we first diagnosed cardiogenic cerebral embolism. Six months later, MRI results showed an improvement of the brain edema; however, the lesion developed after a year. We suspected that this lesion included a brain tumor and performed an open surgical biopsy. Pathological examination revealed that the tumor was an oligodendroglioma(World Health Organization grade 2). Because brain tumors that are complicated with intratumoral bleeding are often highly malignant and the lesions gradually increase in size, it is relatively easy to make a precise diagnosis. However, in low-grade gliomas, the intracerebral hemorrhage and brain edema may occasionally improve in the short term. We show that a case with a discrepancy between hematoma and brain edema should be followed up for at least more than a year, even when initial MRI does not reveal a brain tumor .

Orbitozygomatic Craniotomy with Modified Zabramski's Technique: A Technical Note and Anatomic and Clinical Findings.

BACKGROUND: The surgical technique of orbitozygomatic craniotomy reported by Zabramski et al. is an excellent procedure, facilitating wide surgical exposure, easy orbital reconstruction, and a satisfactory postsurgical aesthetic outcome; however, it is anatomically complicated and technically difficult. We introduce a simplified technique of Zabramski's orbitozygomatic craniotomy and present the anatomic and clinical findings with cadaveric photos, illustrations, and a video. METHODS: The orbitozygomatic craniotomy was performed on 20 sides of 11 cadaveric heads, in which the cut between the inferior orbital fissure and superior orbital fissure was modified and simplified, and the shortest distance between them was measured. This technique was applied to 13 clinical cases, and craniotomy-associated aesthetic and functional complications were evaluated. RESULTS: The average of the shortest distance from the inferior orbital fissure to superior orbital fissure was 21.3 mm (range, 19-23 mm) on the 20 sides of the 11 cadaveric heads. In all 13 clinical cases, orbitozygomatic craniotomy could be achieved in a short time, while preserving the structure of the orbital wall. A hollow at the temple was noted in 1 patient, cerebrospinal fluid leak occurred in 2 patients, and transient facial pain occurred in 1 patient; however, no other craniotomy-associated aesthetic or functional complications, including enophthalmos, were found in any of the 13 patients. CONCLUSIONS: With this modified technique, Zabramski's ideal orbitozygomatic craniotomy could be achieved easily with only minimal complications, while realizing all advantages of the technique.

Predictive Factors for the Occurrence of Visual and Ischemic Complications After Open Surgery for Paraclinoid Aneurysms of the Internal Carotid Artery.

OBJECTIVE: To investigate the predictive factors for visual and ischemic complications after open surgery for paraclinoid aneurysms of the internal carotid artery (ICA). MATERIALS AND METHODS: Thirty-eight consecutive patients with unruptured paraclinoid aneurysms of ICA operated on between 2009 and 2013 were included in this study. The male:female ratio was 6:32 and the ages ranged from 33 to 81 (mean: 60 ± 2). Twenty cases were asymptomatic and 18 had ophthalmological symptoms. The sizes of the aneurysms ranged from 2 to 35 mm (mean: 10.6 ± 9 mm). Twenty-three patients were treated by clipping and 15 by trapping with bypass (high-flow bypass in 11, and low-flow in 4). Twenty-four patients underwent removal of the anterior clinoid process. Among them, 8 underwent en bloc anterior clinoidectomy with a high-speed drill, and 16 had piecemeal excision with a microrongeur or ultrasonic bone curette. Intraoperative monitoring was performed using motor-evoked potentials (MEP) and visual-evoked potentials (VEP) in 27 and 15 cases, respectively. RESULTS: Complete obliteration of the aneurysm was achieved in 37 cases (97.4 %). The patency rate of bypass was 100 %. Postoperative worsening of visual acuity, including one case of blindness, was observed in six cases (11 %). Worsening of visual field defects occurred in 14 cases (38 %), but 10 of them were transient. Transient oculomotor nerve palsy occurred in six cases (15 %). Postoperative stroke was detected by diffusion-weighted imaging (DWI) in five cases (13 %), four of which were symptomatic. Statistical analysis showed that piecemeal anterior clinoidectomy was significantly safer than en bloc removal in preserving visual function. Trapping with high-flow bypass had a significantly greater risk of postoperative stroke than direct clipping. CONCLUSIONS: Intraoperative VEP monitoring might be useful for preventing postoperative worsening of visual function. Two-stage treatment with bypass and endovascular trapping might be safer than single-stage trapping alone.

Long-term follow-up of cryopreservation with glycerol of autologous bone flaps for cranioplasty after decompressive craniectomy.

BACKGROUND: Autologous bone flaps adequately preserved can be used successfully for repair of cranial bone defects with biological and economic advantages. However, the effect or advantages of cryopreservation of autologous bone flaps using cryoprotectant solutions have not been investigated. The aim of this study was to investigate the utility of autologous bone flaps frozen with glycerol in cranioplasty after decompressive craniectomy. METHODS: We evaluated postoperative complications and clinical and aesthetic results in 40 consecutive patients who underwent delayed cranioplasty using autologous bone flaps frozen with glycerol following decompressive craniectomy between 2001 and 2010. Bone flaps removed at the time of external decompression were dipped in 20 % glycerol solution with a sterilized plastic vessel and stored at -84 °C in an ultra-low temperature freezer. The bone flaps were thawed in the vessel at room temperature for 12 h. The bone flaps were taken out of melting glycerol, replaced in their original positions, and fixed with silk sutures or titanium plates. Follow-up periods ranged from 35 to 3745 days (median, 558 days). RESULTS: Mild resorption of the bone flap occurred in one case. However, there were no cases with local infection and no cases requiring reoperation for complications during the follow-up period. CONCLUSIONS: Cryopreservation with glycerol is a simple and safe method for preservation of autologous bone grafts. The clinical and aesthetic results of delayed cranioplasty using autologous bone flaps frozen with glycerol solution were satisfactory.

Clinicopathologic features of small cell glioblastomas.

Small cell glioblastoma (SCGBM) is a variant of glioblastomas characterized by a predominant population of small and monomorphic glial cells. The aim of the present study was to investigate clinical, neuroimaging, pathologic, and genetic features of SCGBM. The clinicopathologic and genetic features were evaluated in 14 patients with SCGBM. All cases were divided into multifocal and solitary type by MRI, and extent of microvascular proliferation, intratumoral necrosis, and perivascular lymphocytic accumulation were investigated. IDH1 mutations by immunohistochemistry (IDH1 R132H) and 1p 19q codeletion by fluorescence in situ hybridization were detected. Patients ranged from 23 to 92 years of age (median: 71 years), with three females and eleven males. The overall survival time of the patients ranged from 7 to 23 months (mean: 11 months). Nine patients (64%) were the multifocal type. Pathologic study revealed that the microvascular proliferation, necrosis, and lymphocytic infiltration were limited in SCGBM. Immunohistochemically, tumor cells were negative for IDH1 R132H in all patients. FISH analysis demonstrated that no SCGBM had 1p/19q codeletion in informative patients. Our investigation suggested that an elderly onset and multifocal lesions were characteristics of SCGBM associated with degradation of the immune response, infiltrative feature of tumor cells, and an unfavorable prognosis.

A Large Endodermal Cyst with Xanthogranuloma at the Frontal Skull Base, Slowly Recurring with Hemorrhage.

A 45-year-old man with a past history of the removal of a degenerated hematoma two times presented with general convulsion. Computed tomography (CT) showed a high-density lobular mass growing from the right frontal skull base and occupying the right frontal lobe. Magnetic resonance imaging (MRI) demonstrated a homogeneously hyperintense mass on T1-weighted imaging and a homogeneously hypointense mass on T2- and T2*-weighted imaging. We removed the lesion, which intraoperatively showed a blackish-brown and jellylike mass with machine oil-like fluid. There was a thin and elastic membrane at the boundary between the mass and degenerated brain tissue, and we removed as much of the membrane as possible. On light microscopy, most parts of the mass consisted of a degenerated hematoma with xanthogranuloma, while the thin and elastic membrane revealed one or two layers of non-ciliated columnar epithelial cells based on thin fibrous tissues with microvessels. Immunohistochemical staining showed that these epithelial cells contained periodic acid-Schiff (PAS)-positive granules, and were positive for cytokeratin (CAM5.2), carcinoembryonic antigen (CEA), and epithelial membrane antigen (EMA). Ultrastructual examination showed numerous microvilli at the surface of non-ciliated cells, and an interdigitation-like, dense adhesion structure. On the basis of pathological findings, the patient was considered to have a large endodermal cyst (EC) at the frontal skull base, probably derived from Seessel's pouch. We speculate that EC developed inflammatory changes with xanthogranuloma, which caused further damage to the blood vessels and continuous hemorrhage.