Dural arteriovenous fistulas in the falx cerebri: case series and literature review.

Dural arteriovenous fistulas (DAVFs) within the falx cerebri are infrequently documented and may be linked with the falcine sinus/venous plexus. The falcine sinus/venous plexus, often regarded as a normal venous structure, can exhibit pathological characteristics, differing from the persistent fetal falcine sinus. A retrospective analysis was conducted at a single center to identify all cases of DAVFs within the falx cerebri spanning from 2002 to 2022. Demographic data, fistula features, treatment modalities, clinical outcomes, and fistula closure were collected and analyzed. Additionally, relevant literature on DAVFs in this location was reviewed. Ten cases were identified at our center, supplemented by 13 cases reported in the literature. In our cohort, patients had an average age of 49.4 ± 8.1 years, with a male predominance of 90%. Trans-arterial embolization (TAE) alone achieved immediate complete occlusion in eight cases, while conservative treatment was pursued in two cases. No treatment-related complications or fistula recurrences were observed. In the literature, seven patients underwent direct surgery, three underwent TAE, and one underwent both direct surgery and radiosurgery for complete fistula closure. No instances of fistula recurrence or treatment complications were reported. Dural arteriovenous fistulas within the falx cerebri are rare, with limited literature available. They typically present as aggressive lesions. Treatment options include direct surgery or TAE. However, due to a lack of long-term DSA follow-up, the cure and recurrence rates are unknown for endovasdcular therapy. Further investigation is warranted to elucidate the involvement of the falcine sinus/venous plexus in falx cerebri DAVFs.

Falx cerebelli and its associated occipital venous sinus: an anatomical study.

PURPOSE: This study presents the morphological variation of falx cerebelli, which helps to identify the possible variations in the presence of the occipital sinus in the posterior margin of the fold whose damage during midline incision of posterior cranial fossa surgeries may lead to internal hemorrhage. METHOD: The study was conducted on 48 cranial cavities exploring the falx cerebelli. Variations in the number of folds, its proximal and distal attachments, and the drainage pattern of the occipital sinus were evaluated by histological processing of the upper 1/3rd section of the falx fold. RESULTS: The variation in the number of folds recorded are single folds in 87.5%, double folded in 8.3%, and multiple folds (five and seven folded) in 4.2% of the cases. The variation in the proximal and distal attachments in single falx folds showed three combinations: Ramified triangular in 66.7%, both ramified type in 12.5%, and both triangular type in 8.3% of the cases. Double and multiple folds showed ramified and triangular types of variation in their attachments. Histological findings showed the presence of occipital venous sinuses in most of the single falx fold. Two aberrant venous sinuses were seen in a double and five-folded falx cerebelli. CONCLUSIONS: This study records the variations in the morphology of falx cerebelli. The histological data of this study sheds light on the drainage pattern of venous sinuses in the area whose negligence during midline incisions of brain surgeries may increase the possibility of hemorrhage.

Gamma Knife radiosurgery for meningiomas of the confluence of the falx and tentorium.

PURPOSE: Meningiomas arising from the confluence of the falx and tentorium (CFT) are a rare and challenging subset of meningiomas. Gamma Knife radiosurgery (GKRS) is well-established as a safe and effective management strategy for intracranial meningiomas, but its role in treating CFT meningiomas is not well-described. This paper reports the largest series focused exclusively on the outcomes of GKRS for CFT meningiomas. METHODS: We retrospectively identified 20 CFT meningiomas out of 2031 meningioma patients who underwent GKRS at our institution between 1987 and 2021. Tumor control, overall survival (OS), and complications were recorded and analyzed. The median tumor margin dose was 13 Gy at the 50% isodose line. The median tumor volume treated was 4.4 cc (IQR 3.5-7.7). The median patient age was 58 years (range 33-83), the median MRI surveillance duration was 59 months (IQR 34-92), and the median overall follow-up duration was 92 months (IQR 42-201). RESULTS: The local tumor control rate (PFS) at 5 and 10-years were 100% (N=10) and 83% (N=4), respectively. Eight patients had stable tumor volumes and 11 patients had regression. One patient with a twice-operated tumor had delayed progression at 7.5 years and was retreated with GKRS. No patient had adverse radiation effects during the period of MRI surveillance. The 5 and 10-year OS were 100% (N=13) and 100% (N=7), respectively. CONCLUSIONS: GKRS is a valuable therapeutic strategy for patients with newly diagnosed CFT meningiomas or progressive residual tumors after surgical resection.

Meningiomas of the rolandic region: risk factors for motor deficit and role of intra-operative monitoring.

OBJECTIVE: Meningiomas of the rolandic region are associated to high risk of postoperative motor deficits. This study discusses the factors affecting motor outcome and recurrences from the analysis of a monoinstitutional case series and eight studies from a literature review. METHODS: Data of 75 patients who underwent surgery for meningioma of the rolandic region were retrospectively reviewed. The analyzed factors included tumor location and size, clinical presentation, magnetic resonance imaging (MRI) and surgical findings, brain-tumor interface, extent of resection, postoperative outcome and recurrence. Eight studies from literature on rolandic meningiomas treated with or without intraoperative monitoring (IOM) were reviewed with the aim to define the impact of IOM on the extent of resection and motor outcome. RESULTS: Among the 75 patients of the personal series, the meningioma was on the brain convexity in 34 (46%), at the parasagittal region in 28 (37%) and at the falx in 13 (17%). The brain-tumor interface was preserved in 53 cases (71%) at MRI and in 56 (75%) at surgical exploration. Simpson grade I resection was obtained in 43% of patients, grade II in 33%, grade III in 15% and grade IV in 9%. The motor function worsened postoperatively in 9 among 32 cases with preoperative deficit (28%) and in 5 among 43 with no preoperative deficit (11.5%); definitive motor deficit was evidenced in overall series at follow-up in 7 (9.3%). Patients with meningioma with lost arachnoid interface had significant higher rates of worsened postoperative motor deficit (p = 0.01) and seizures (p = 0.033). Recurrence occurred in 8 patients (11%). The analysis of the 8 reviewed studies (4 with and 4 without IOM) shows in the group without IOM higher rates of Simpson grades I and II resection (p = 0.02) and lower rates of grades IV resection (p = 0.002); no significant differences in postoperative immediate and long-term motor deficits were evidenced between the two groups. CONCLUSIONS: Data from literature review show that the use of IOM does not affect the postoperative motor deficit Therefore, its role in rolandic meningiomas resection remains to be determined and will be defined in further studies.

Interhemispheric contralateral approach: the falx as a retractor.

The contralateral transfalcine approach is a valuable option to access lesions around the mesial surface of the brain hemispheres. Despite a favourable perspective, surgical manoeuvres within the interhemispheric fissure carry a risk of inadvertent injury to the healthy cortex on the craniotomy side. To overcome this drawback, a new method of brain retraction was developed. After dissecting the interhemispheric fissure, the falx was incised in an upside-down U-shaped manner and hinged inferiorly, taking care not to violate the inferior sagittal sinus. The falcine flap was reflected laterally and fixed to the lateral edge of the craniotomy, providing homogeneous retraction of the ipsilateral mesial cortex. Surgery proceeded with the brain surface hidden from the surgeon's view and protected by the flap. The absence of retractor devices hindering the surgeon's movements further simplified the procedure.

Bulky supernumerary bone of the falx cerebri: case report and literature review.

We present a rare case of ossification of the falx cerebri in a 25-year-old man, discovered incidentally on a craniofacial computed tomodensitometry (CT) scanner. This ossification presented a true cortico-medullary differentiation and pushed aside the right frontal lobe. There was no associated clinical manifestation.

Anatomic variations of the human falx cerebelli and its association with occipital venous sinuses.

PURPOSE: Human falx cerebelli is an important anatomical structure in regard to its relations with venous structures during infratentorial approach to reach cerebellar tumors, vascular malformations, traumatic hemorrhage and Chiari malformations. The present study aim to describe the different types of variations of the falx cerebelli, its morphological features and its association with occipital venous sinuses. METHOD: In this study 49 dura mater was obtained from the Institution of Forensic Medicine. The length, width and the depth of the falx cerebelli were measured using a digital compass. The data obtained were statistically analyzed in relation to age and gender. The relations of the falx cerebelli with the occipital sinus was documented. Histological sections from the falx cerebelli were stained with Hematoxylin Eosin to evaluate the fine structure. RESULTS: Among the 49 falx cerebelli examined 36 (73.5%) were classified as normal. The average length, width and depth of the normal falx cerebelli was 3.7, 1.0 and 0.4 cm respectively. Of the 49 falx cerebelli in 1 (2%) case it was absent, in 5 cases (10.2%) duplicate, in 5 cases (10.2%) triplicate, in 1 (2%) case quadruplets and in 1 case (2%) it was five-folded. The proximal and the distal attachments of the falx cerebelli showed 3 types of variations; both attachments triangular, the proximal attachments triangular and the distal ramified and distal attachments triangular and the proximal attachments ramified. The drainage of the occipital sinus of falx cerebelli with variations were evaluated. The increased number of falx cerebelli highly corresponded with the increased number of occipital sinus. CONCLUSIONS: The dural-venous variation in the posterior cranial fossa can be problematic in various diagnostic and operative procedures of this region. Neurosurgeons should be aware of such variations, as these could be potential sources of haemorrhage during the midline suboccipital and infratentorial approaches.

Inferior sagittal sinus: magnetic resonance imaging study.

PURPOSE: To date, no study has explored the inferior sagittal sinus (ISS) using neuroimaging modalities. This investigation aimed to characterize it using magnetic resonance imaging (MRI). METHODS: A total of 77 patients with intact cerebral hemispheres and covering meninges underwent thin-sliced, contrast-enhanced MRI. RESULTS: The ISS was well delineated as a linear structure with a constant diameter in 97% of the patients. The maximum intensity projection (MIP) images well delineated the three-dimensional architecture of the ISS and relevant veins. The identified ISSs could be classified into three different types, with the underdeveloped type being the most frequent at 47%. In addition, the ISSs showed considerable variability both in the original site and course along the lower margin of the falx cerebri. Furthermore, in 22% of the cases, fenestrations were identified in the falx cerebri adjacent to or near the ISS. More than 70% of them were located in the middle third of the falx, followed by the anterior and middle thirds of the falx. CONCLUSIONS: The ISS is a constant venous structure characterized by morphological variability and may function as an adjunctive or assistive venous drainage route. Thin-sliced, post-contrast-enhanced sagittal MRI combined with MIP imaging is useful for exploring the ISS.

The fetal falx cerebelli.

BACKGROUND: The falx cerebelli is a retrocerebellar dural reflection. The MR spectrum of the fetal falx cerebelli has not been described. OBJECTIVE: To determine the prevalence of falx cerebelli abnormalities in the context of posterior fossa malformations and compare them to age-matched normal fetal MRI exams. MATERIALS AND METHODS: We reviewed all consecutive fetal MRIs performed over 1 year at a children's hospital. We assessed the falx cerebelli in each examination for location, morphology, size and number. Exams were grouped into (1) normal or non-brain/head abnormalities or (2) abnormal brain or craniofacial structures. We used chi square, linear regression and logistic regression analyses; P<0.05 was considered significant. RESULTS: We included 424 examinations (223 controls, 201 malformations) from 378 patients (mean gestational age 27±6 weeks). In the control group, the mean falx size was 2.6±1.2 mm (anteroposterior) × 11.0±3.2 mm (craniocaudal), with 80% retrovermian centered; the falx was linear (23%), Y-shape (15%), V-shape (22%) or U-shape (21%); it was unusually multiplicated (17%) or absent (<2%). Falx cerebellar abnormalities were more common in abnormal exams (59%; 119/201) than in normal exams (19%; 43/223) (P<0.001). The falx was abnormal with Blake pouch cysts (9/9, 100%) and rhombencephalosynapsis (3/4, 75%), absent in all Chiari II (n=9) and most Dandy-Walker malformations (5/6, 83%), commonly multiplicated in mega cisterna magna (14/22, 64%), and deviated or absent in cases with arachnoid cysts (3/3, 100%) and adhesions (4/5, 80%). CONCLUSION: Structural alterations of the falx cerebelli are more prevalent in fetuses with brain and craniofacial abnormalities. Specific changes offer clues to posterior fossa diagnoses.

Interdural high signal on CISS sequence: an alternative CSF pathway?

PURPOSE: The falx cerebri, falx cerebelli, and tentorial notch exhibit a peculiar morphology with a two-layered, dural leaf that protrudes into the cranial cavity with a free edge. However, there are few studies exploring this morphology using neuroimaging techniques. The present study aimed to explore these dural structures using magnetic resonance imaging. METHODS: A total of 65 outpatients were included in this study. Following initial examinations with conventional sequences, the constructive interference in steady-state (CISS) sequences were performed in thin-sliced, coronal sections. RESULTS: In 78% of the subjects, the interdural spaces presenting with high signal were identified in the falx cerebri. These spaces were located adjacent to the uppermost part of the falx, formed by two dural leaves and the superior sagittal sinus, and tapered downward where the leaves united to form the falx cerebri. At the tentorial notch, these spaces were found in 52% of the 65, most predominantly in the medial edge followed by the tentorium cerebelli-tentorial notch junctional region. Forty-one percent of patients had a dural opening into the cerebral cistern. The interdural spaces with high signal were not identified in the tentorium cerebelli in any of the subjects. CONCLUSIONS: The falx cerebri and tentorial notch form the interdural spaces that may provide alternative cerebrospinal fluid pathways. The coronal CISS sequence is suitable for delineating such interdural spaces.

Modified unilateral approach for mid-third giant bifalcine meningiomas: resection using an oblique surgical trajectory and falx window.

BACKGROUND: Utilizing the shortest available trajectory is the norm for excision of meningiomas. However, such an approach for the mid-third/central falcine meningiomas risks the adjoining draining veins and eloquent cortex. A larger size and bilaterality of such tumors adds to the surgical challenge. Herein, we report the surgical nuances of a modified unilateral approach in patients operated for giant bilateral symmetrical mid-third falcine meningiomas. METHODS: Five such patients were operated. The clinico-radiologic data was studied at presentation and at the follow-up. The meningiomas were subclassified into those that were located in the anterior and posterior half of the central falx, and their surgical trajectory was chosen accordingly. The tumor was excised through an oblique anterior or a posterior trajectory instead of directly working over the major draining veins and eloquent brain. The falx was incised to create a surgical window and access the tumor on the contralateral side. RESULTS: Four patients had meningiomas in the anterior half and one in the posterior half of central falx. Simpson excision was grade II in four patients. One patient showed small residual tumor and underwent stereotactic radiosurgery. The overall mean follow-up of the patients was 9.2 months. All the patients had good clinical outcome. CONCLUSIONS: Giant bifalcine meningiomas can be safely resected through a unilateral approach. Falx opening serves as a window to remove the tumor from the contralateral side. An oblique trajectory rather than an end-on access to these tumors minimizes the risk of venous and cortical injury.

Venous channels of the falx cerebri in adult Japanese population: delineation using magnetic resonance imaging.

PURPOSE: Few studies have characterized the venous channels of the falx cerebri under physiological conditions. The present study aimed to explore the falx cerebri using magnetic resonance imaging (MRI). METHODS: A total of 91 patients (41 men and 50 women) with an intact falx cerebri and relevant dural sinuses underwent contrast MRI. RESULTS: In 15% of the participants, the falx cerebri contained venous channels with a patchy appearance. Seven of these channels were located in the anterior third of the falx, two were in the anterior two-thirds, and 5 were in the middle third. In 19 (21%) participants, the falcine sinus was unequivocally delineated. In 14 of them, connected the posterior third of the superior sagittal sinus and uppermost part of the straight sinus. These sinuses showed variable morphologies, presenting with linear, triangular, multi-channel, and branching appearances. The linear type was the most predominant and found in 50% of these cases. In contrast, in the remaining five participants, the falcine sinuses were coursing posteriorly, connecting the posterior third of the falx cerebri with the superior sagittal sinus. CONCLUSION: The falx cerebri may have a role as a pathway in the intracranial venous circulation. The falcine sinus has several variants with diverse morphologies.

Is the presence of corpus callosum predictable in the first trimester?

Corpus callosum agenesis (CCA) is a clinical condition accompanied by various aneuploidy and genetic syndromes. We identified the development of the corpus callosum (CC) in 278 patients before 18 weeks of gestational age by visualising the pericallosal artery (PCA) in the callosal sulcus and changes in the lengths and ratios of the midbrain (MB) and falx (F), which suggested elevation of the third ventricle and thalamus due to CCA in the first trimester. We succeeded in visualising the path of the PCA in 273 patients. As expected, we observed an increase in the lengths of the MB and F throughout the pregnancies. The MB:F ratio was 0.5-0.6, and it was independent of gestational age. In all 278 patients, the MB:F ratio was <0.6 (95th percentile = 0.79). We observed the presence of the CC during anatomical screening at gestational weeks 18-24. Visualisation of the PCA path (98% sensitivity) and calculation of the MB:F ratio <95th percentile (0.79-100% sensitivity) had very high sensitivity that indirectly confirmed the presence of the CC in the first trimester of pregnancy. Impact statement What is already known on this subject: After reading the articles for detecting the absence of corpus callosum (CC) at first trimester with midbrain (MB) and falx (F) measurement by Lachmann et al. ( 2013 ) and visualising pericallosal artery (PCA) as an indirect sign of CC agenesis by Pati et al. ( 2012 ), we aimed to have a look for our records visualising PCA in callosal sulcus and measure MB-F, as well as their ratios for an indirect sign of 'presence' of CC at first trimester. What the results of this study add: In recent literature, it is not possible to find many articles suggesting the presence of CC between 11 and 13 weeks of gestation. Díaz-Guerrero et al. ( 2013 ) and Pati et al. ( 2012 ) has researched visualising PCA path. Lachmann et al. ( 2013 ) reported an article for MB and F measurements in early suspicion of CC agenesis. Our study will be the first article in visualising PCA path and measuring MB-F lengths as well as their ratios for 'presence' of CC with high sensitivity rates (98% and 100%). What are the implications of these findings for clinical practice and/or further research: This study encourages clinicians visualising PCA path and measure MB-F lengths when they will try to visualise repetitive times and see how it is an easy procedure when you get used to it.

The missing falx: a potential surgical pitfall during interhemispheric transcallosal approach.

One of the standard surgical approaches to lateral ventricular tumors involves interhemispheric dissection along the falx cerebri. The falx cerebri thus provides an important landmark in guiding the surgeon to the midline. Unrecognized absence of falx may lead to surgical complications. A child with tuberous sclerosis presented with refractory epilepsy and a lateral ventricular tumor. The tumor was excised by an interhemispheric trans-callosal approach. The midline falx cerebri was absent anteriorly, rendering the identification of midline difficult. The embryology of a deficient falx and its surgical implications are discussed in this short report.

Resection of falx and parasagittal meningioma: complication avoidance.

Falx and parasagittal meningiomas are common locations for meningiomas of the cranial vault. Many of these tumors are now discovered incidentally during cranial imaging for other reasons. Therefore, in the calculation of the risks and benefits of surgery it behooves the surgeon to do all he/she can to avoid surgical complications. This is a heavily experience based article based off the senior author's experience with over 1200 intracranial meningiomas. We present three cases to illustrate some of the decision-making and techniques used to reduce complications in the management of these cases treated with an open operation.

Purely endoscopic removal of a parasagittal/falx meningioma.

BACKGROUND: Endoscopic techniques are an integral part of the neurosurgical armamentarium with a growing list of indications. We describe the purely endoscopic removal of an atypical parasagittal meningioma in a patient who could not undergo standard craniotomy due to severe scalp atrophy following childhood irradiation for tinea capitis. METHODS: A 68-year-old man in good general health presented with a parasagittal meningioma that recurred following subtotal removal and adjuvant fractionated stereotactic radiosurgery (FSR). The scalp above the tumor location was very diseased and precluded a regular craniotomy for tumor removal. A 4-cm craniotomy was made in the midline forehead, where the skin was normal. A rigid endoscope was advanced under neuronavigation through the interhemispheric fissure, which provided good access with limited retraction, until the tumor was encountered at a depth of 7-8 cm. Two surgeons performed the surgery using a "four-hands technique". The tumor was removed and the insertion area was resected and coagulated. RESULTS: The surgery was uneventful, with no coagulation or transection of major veins. A subtotal resection was achieved, and the patient recovered with no neurological deficit. CONCLUSIONS: Safe resection of parasagittal meningiomas with a purely endoscopic technique is feasible. This option needs further exploration as an alternative strategy in patients with severely atrophic scalp skin that greatly increases the risk of significant healing complications with calvarian craniotomy.

A possible venous connection between the cranial and nasal cavity.

PURPOSE: The foramen cecum (FC) is a fine bony canal with the aperture located immediately anterior to the crista galli (CG). The venous structures in the regions of the FC and CG have been inconsistently described and are not well understood. Here we explore these veins using magnetic resonance imaging. MATERIALS AND METHODS: We enrolled 101 patients who underwent contrast examinations and exhibited intact skin, skull, dura mater, and intracranial dural sinuses. Imaging data were obtained as thin-sliced, seamless sagittal sections and were transferred to a workstation for analysis. RESULTS: In 84 % of the patients, tubular-shaped venous extensions arose from the rostral end of the falx cerebri and were confirmed to lie in the FC. These extensions were supplied by the superior sagittal sinus or the frontal cortical vein, and were classified into four types: rudimental slight projections, short and straight extensions, long and straight channels, and long and tortuous channels. Furthermore, 27.7 % of the patients exhibited a distinct venous channel between the venous extension in the FC and the median vestibular submucosa of the nasal cavity. Among these channels, 81.5 % were connected to the vein lying in the FC via a short channel that vertically pierced the CG. CONCLUSIONS: The FC contains tubular-shaped venous extensions that are supplied by the rostral end of the superior sagittal sinus or the frontal cortical vein. The cranial cavity, FC, and nasal cavity may be connected by a venous channel.

Skeletal and cranio-facial signs in Gorlin syndrome from ancient Egypt to the modern age: sphenoid asymmetry in a patient with a novel PTCH1 mutation.

Gorlin syndrome is an autosomal dominant disorder linked to PTCH1 mutation, identified by a collection of clinical and radiologic signs. We describe the case of a family in which father and son fulfilled clear cut diagnostic criteria for Gorlin syndrome including multiple basal cell carcinomas, keratocystic odontogenic tumors, atypical skeletal anomalies and a novel PTCH1 germline mutation (c.1041delAA). Craniofacial and other skeletal anomalies displayed at 3D and helical CT scan were: macrocephaly, positional plagiocephaly, skull base and sphenoid asymmetry, bifidity of multiple ribs and giant multilocular odontogenic jaw cysts. Extensive multilamellar calcifications were found in falx cerebri, tentorium, falx cerebelli and in the atlanto-occipital ligament. The inclusion of bifid ribs as a novel major criteri may be useful for the recognition and characterization of misdiagnosed cases.

Dural composite hemangioendothelioma: The first intracranial case.

Background: Composite hemangioendothelioma (CHE) is a rare, locally aggressive neoplasm of intermediate malignant potential. It is composed of a mixture of vascular tumors with a predilection for the dermis and subcutis of the extremities. Case Description: In this report, we describe a 41-year-old man who presented with a 2-month history of headache, dizziness, and intermittent seizures. Magnetic resonance imaging showed a hemorrhagic, multilobulated, and dural-based mass with extension into the calvarium. The mass measured 10.3 × 4.8 × 4 cm along the interhemispheric fissure and encased the superior sagittal sinus. Excision was performed, and histopathologic examination revealed a heterogeneous mixture of vascular components consisting of epithelioid hemangioendothelioma, retiform hemangioendothelioma, and hemangioma. This is the first report of a primary intracranial CHE. Conclusion: The spectrum of mesenchymal neoplasms within the cranium expands to encompass CHE.

Acute subdural hematoma caused by hemorrhagic falx meningioma: A case report and review of the literature.

We herein report a case of acute subdural hematoma caused by hemorrhagic falx meningioma. The patient was a 64-year-old woman with no significant medical history or prior history of trauma. She experienced a sudden onset of headache and weakness in her extremities. Computed tomography (CT) scan and magnetic resonance imaging (MRI) showed a mass lesion with intratumoral hemorrhage or faint calcification along the left side of the fronto-parietal cerebral falx. There was also a linear lesion at the left side of the falx, suggesting acute subdural hematoma. MRI was performed again on the eleventh day. On precontrast T1-weighted images, intratumoral hemorrhage and widespread left subdural hematoma were shown as high intensity. On postcontrast T1-weighted images, the tumor showed heterogeneous enhancement with a dural tail sign on the falx, indicative of a falx meningioma. She underwent surgical resection, and the histological subtype was transitional meningioma. Nine cases of hemorrhagic falx meningioma associated with acute subdural hematoma have been reported. If not limited to the site of occurrence, there have been 59 reported cases overall. In our investigation, the incidence of hemorrhage is higher in the convexity and lower in the skull base. It is higher for fibrous, angiomatous, and metaplastic subtypes and lower for meningothelial subtype. The location and histological subtype might be risk factors for meningioma associated with subdural hematoma. Further accumulation of cases will be necessary to establish the cause of bleeding.