Spinal endodermal cyst undergoing malignant transformation and marked elevation of serum carbohydrate 19-9 level.

Endodermal cyst (EC) is a benign tumor that can arise along the craniospinal axis. Infrequently, ECs undergo malignant transformation. A 43-year-old man presented with numbness in the right arm, leg and occipitalgia. MRI revealed a multicystic, intradural extramedullary tumor at C2 with enhancement along the ventral surface of the spinal cord. Blood test showed an abnormal increase in serum carbohydrate antigen 19-9 (CA 19-9) level. Systemic positron emission tomography-computed tomography was normal. He underwent total tumor resection and was diagnosed with EC. He developed double vision, hearing loss, and swallowing difficulty on postoperative day 70. Cerebral MRI revealed marked extensions of leptomeningeal dissemination. The serum CA 19-9 level increased continuously and finally reached 1515.0 U/ml. He died of respiratory failure on day 108. An autopsy did not reveal abnormalities in the abdominal and chest organs. On microscopic examination, the post-mortem specimen revealed adenocarcinoma. Immunohistochemically, both the surgical and autopsy specimens were positive for CA 19-9. Spinal ECs may lead to malignant transformation with leptomeningeal dissemination that causes abnormal elevation of serum CA 19-9 levels.

The Superior Ophthalmic Vein: Anatomical Perspective for Transvenous Access to the Cavernous Sinus.

The anatomical characteristics of the superior ophthalmic vein (SOV), which is crucial when performing craniofacial surgeries and transvenous access to the cavernous sinus, have not been documented. The present study aimed to explore them using magnetic resonance angiography (MRA). A volumetric, phase-contrast MRA was performed in 74 outpatients not bearing vascular or tumorous pathologies in the face, orbit, and cavernous sinus. The entire course of the SOV was delineated in 46 patients (62%), for 76% on the right side and 83% on the left. These SOVs consistently showed a characteristic morphology with a laterally coursing proximal segment and a medially coursing distal segment. The latter segment was connected to the angular, supraorbital, supratrochlear, facial, and external nasal veins that were inconsistently delineated. The angular vein was tortuous in 51% of the patients on the right and 53% on the left. The morphology of the proximal part of the SOV was also variable and involved a tortuous segment in 11% of the patients on the right and in 7% on the left. Furthermore, in 4 patients (8.7%), a fenestration was found in the right SOVs. Inconsistent tributaries of the SOV, tortuous angular vein, and possible tortuous segment and fenestration of the SOV can make orbital transvenous access to the cavernous sinus difficult.

Does the prone sleeping position affect the intracranial dural venous flow?

PURPOSE: There are few studies documenting the effect of posture on intracranial dural venous flow. The aim of the present study was to explore alterations caused by the prone position using magnetic resonance (MR) venography. METHODS: A total of eight patients (five men and three women) underwent non-contrast MR venography in both supine and prone positions. RESULTS: In the prone position, an increase in intracranial dural venous flow was found in all patients in the non-dominant transverse and sigmoid sinuses. An increase in venous flow to the straight sinus was observed in 75% of the patients. Flow to the superior ophthalmic vein decreased in three patients. No postural flow alterations were observed in any of the patients in the superior sagittal, dominant transverse, and sigmoid sinuses. CONCLUSION: Based on results of the study, in the prone sleeping position, part of the intracranial venous flow may be preferentially drained through the straight and non-dominant transverse sinuses.

Vertebral artery segment at the suboccipital dural penetration site: an anatomical study using magnetic resonance imaging.

PURPOSE: The morphology of the vertebral artery (VA) segment at the suboccipital dural penetration site has little been explored with magnetic resonance imaging (MRI). Therefore, the aim of this study was to examine the structure using MRI. METHODS: In total, 94 patients underwent thin-sliced, contrast MRI in the axial, coronal, and sagittal planes involving the atlas, axis, occipital bone, and V3 and V4 segments of the VA. RESULTS: The VA segment at the suboccipital dural penetration site was well-delineated in 93% on the axial images and in 95% on the coronal images. The axial images showed that 82% of the VA penetration sites were located in the middle third of the dural sac. Meanwhile, the coronal images revealed that the heights of both VA penetration sites were located at the same level in 87%. The axial VA penetration angle, which is formed by the VA and tangential line of the dural sac, was 66 ± 11.9° on the right side and 61 ± 14.1° on the left side. The coronal VA penetration angle, which is formed by the tangential line of the VA and dural sac, was 111 ± 24.6° on the right side and 112 ± 19.9° on the left side. CONCLUSIONS: The morphology of the VA segment is considerably variable at the suboccipital dural penetration site, while most penetration sites are located in the middle third of the dural sac on axial MRI. These should be assumed during surgeries around the suboccipital VA penetration site.

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.

Possible cerebrospinal fluid pathways in the middle fossa floor and pterional diploe: a magnetic resonance imaging study.

PURPOSE: There has not been a study documenting the distribution of cerebrospinal fluid (CSF) pathways in the anterolateral base of the middle fossa (ALB) and diploe of the pterional region (Pt). The present study aimed to delineate these pathways using magnetic resonance imaging. METHODS: Thin-sliced, axial, and coronal T2-weighted sequences were performed for a total of 358 outpatients, including 20 pediatric patients. RESULTS: Adult population: CSF-filled channels were identified on axial images in the ALB in 57% and in the diploe of the Pt in 65% of 338 patients. These pathways showed variable morphology and number bilaterally. CSF-filled channels were identified on coronal images in the ALB in 14% and in the diploe of the Pt in 100% of 59 patients. These were delineated as linear structures of variable number and thickness. Eleven percent of the pathways identified in the ALB was connected with extracranial channels. Pediatric population: CSF-filled channels were identified on axial images in the ALB in 75% and in the diploe of the Pt in 80% of 20 patients. CONCLUSIONS: The ALB and diploe of the Pt may function as CSF pathways in children and adults. The pathways in the ALB can be a CSF-drainage route connecting to the extracranial sites.

Diploic veins of the cranial base: an anatomical study using magnetic resonance imaging.

PURPOSE: The anatomy and distribution of the diploic veins (DVs) of the cranial base have not been fully documented. The aim of this study was to characterize these veins using contrast magnetic resonance imaging (MRI). METHODS: In total, 95 patients underwent thin-sliced, contrast MRI. Coronal and sagittal images were used for the analysis. The cranial base was divided into the anterior, middle, and posterior bases. Then, each base was further subdivided into three equal parts in the anteroposterior and lateromedial directions. The anteroposterior parts were evaluated on coronal images, while the lateromedial parts were evaluated on sagittal images. RESULTS: The DVs were identified over the entire cranial base. However, they were more frequent in the posterior-third of the lateral-third region of the anterior, middle-third of the lateral and middle-third regions of the middle, and middle-third region of the posterior cranial base, and sparse in the posterior and medial-third regions of the middle cranial base. The DVs showed marked morphological variability. For instance, the DVs of the pterional area were generally well defined, as pivotal channels connecting the lateral parts of the anterior and middle cranial base, but were highly varied in appearance. CONCLUSIONS: The DVs of the cranial base are distinct structures characterized by morphological variability and topographical predilection. Contrast MRI is useful for delineating these veins.

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.

An undescribed venous pathway intervening between the olfactory fossa and nasal vestibule.

PURPOSE: A curvilinear pathway intervening between the olfactory fossa and nasal vestibule has not been well documented. Therefore, the aim of this study was to examine its structure using magnetic resonance imaging (MRI). METHODS: In total, 84 patients underwent thin-sliced, contrast MRI. Among these patients, 31 underwent additional thin-sliced, sagittal T2-weighted imaging. RESULTS: A curvilinear pathway intervening between the olfactory fossa and nasal vestibule was delineated on sagittal and coronal imaging in 98% and 82% of patients, respectively. All of these pathways demonstrated communication with the lower limit of the superior sagittal sinus (SSS) or fine venous channels connecting to the SSS in the vicinity of the crista galli. The pathway was identified in the parasagittal regions on both sides with varying lengths, diameters, and curvatures. In 94% of the patients who underwent sagittal T2-weighted imaging, the pathways appeared as linear high-intensity signals. Most pathways were delineated as a single channel coursing extracranially adjacent to the olfactory fossa. In 38% of the patients, post-contrast sagittal images showed variable filling defects between the olfactory bulb and floor of the olfactory fossa, furthermore traversing the venous pathway. Additionally, in 73% of the patients, post-contrast images identified diploic venous channels, variably in the nasal bone and communicating with the venous pathway. CONCLUSIONS: A curvilinear pathway intervening between the olfactory fossa and nasal vestibule is a consistent venous structure and may function as an extracranial route of cerebrospinal fluid drainage.

The diaphragma sellae, diaphragm opening, and subdiaphragmatic cistern: an anatomical study using magnetic resonance imaging.

PURPOSE: Few studies have explored the detailed morphology of the diaphragma sellae (DS), diaphragm opening (DO) or stoma, and subdiaphragmatic cistern (SDC) using neuroimages. The aim of the present study was to characterize these structures using magnetic resonance imaging. METHODS: Thin-sliced, sagittal and coronal T2-weighted imaging was performed for a total of 84 outpatients. RESULTS: The DS, DO, SDC, and relevant structures were consistently delineated in all patients. In 66% of patients, all three structures appeared to be highly variable, and were classifiable as six distinct morphological types. In 4% of patients, the DS presented as a complete sheet lacking a discernible DO. In addition, 30% of the patients presented with undiscernible SDCs. In the coronal sections of 11% of patients, the pituitary glands extended laterally, reaching or extending beyond the center line on the sectional image of the cavernous internal carotid artery. CONCLUSIONS: Thin-sliced, sagittal, and coronal T2-weighted sequences are useful for delineating the DS, DO, and SDC. Morphological variation of these structures among individuals may considerably influence the direction of pituitary tumor expansion.

Visualization of the periventricular Virchow-Robin spaces with ependymal openings.

PURPOSE: The morphological relationships between the periventricular Virchow-Robin spaces (VRSs) and cerebral ventricles have been poorly documented. The present study aimed to explore the issue using magnetic resonance imaging. METHODS: A total of 211 patients were included in this study. T2-weighted and constructive interference in steady state (CISS) sequences were performed in thin-sliced, coronal sections. RESULTS: On T2-weighted sequence, the periventricular VRSs with ependymal openings were identified in 34% of 139 subjects. All the openings were located in the lateral wall of the anterior horn. In CISS sequences, such VRSs were found in 39% of 72 subjects. The mean age was significantly higher in the population with such VRSs compared to those without VRSs (p = 0.0047). Of the 58 periventricular VRSs with ependymal openings identified on T2-weighted images, 16% were located in the upper, 36% in the middle, and 48% in the lower part of the lateral wall. Of the 38 such VRSs identified on CISS images, 32% were located in the upper, 24% in the middle, and 42% in the lower part of the lateral wall, and 3% in the upper part of the medial wall. CONCLUSIONS: The ependymal openings of the periventricular VRSs may be centered in the lateral wall of the anterior horn. The coronal CISS sequence can sensitively delineate the VRSs with ependymal openings.

Spinal Dural Arteriovenous Fistula Assumed to be Symptomatic after Placement of Lumbar Cerebrospinal Fluid Drain.

A 69-year-old man presented with severe headache. Cranial computed tomography revealed diffuse subarachnoid hemorrhage. An anterior communicating artery aneurysm was identified and successfully obliterated by open microsurgery on the same day. Following placement of a continuous lumbar cerebrospinal fluid drain on hospitalization day 7, the patient developed a severe paraplegia and sensory loss below T6. Cerebral magnetic resonance imaging did not identify a responsible lesion. Spinal magnetic resonance imaging, however, showed extensive intramedullary hyperintensity on T2-weighted sequences. Spinal angiography identified a dural arteriovenous fistula fed by the segmental artery branching with the 12th intercostal artery. It was successfully embolized and the patient's sensorimotor disturbances remarkably improved. A spinal dural arteriovenous fistula may better be considered as one of the underlying etiologies when patients exhibit new neurological deficits after placement of a continuous lumbar cerebrospinal fluid drain.

Cortical bridging venous segment protruding into the inner skull depression: a potential site of hemorrhage at external ventriculostomy.

PURPOSE: The cortical bridging venous segment protruding into the inner skull depression (CBVISD), a distinctive structure found in the calvarial convexity, may be a potential risk factor for hemorrhagic complications resulting from trephination. However, this subject has not been documented. In the present study, we explore the CBVISD using magnetic resonance imaging (MRI). METHODS: A total of 94 patients underwent contrast-enhanced MRI. Distributions of the CBVISDs were recorded in two symmetrical regions of the frontal calvarial convexity. The lateral dimensions on both hemispheres were defined to range between 25 and 35 mm from the midsagittal section. The anteroposterior axis was delimited anteriorly by the supraorbital bar and posteriorly by the coronal suture, which was further divided into four parts: the forehead (FH), anterior frontal (AF), FH-AF junctional, and posterior frontal (PF) regions. RESULTS: Analysis of the delineations revealed that the CBVISDs had variable shapes and sizes. They were identified on the right side in 40% of the 94 patients and in 41% on the left side. Among the 91 identified CBVISDs, 5.5% of the CBVISDs were located in the FH, 17.6% in the FH-AF, 34.1% in the AF, and 42.9% in the PF. CONCLUSIONS: The CBVISDs are most frequently located at the common trephination site of external ventriculostomy. Trephination performed in the FH and FH-AF junctional regions may be safer than that in more posterior frontal areas.

The third ventricle roof: an anatomical study using constructive interference in steady-state magnetic resonance imaging.

PURPOSE: The third ventricle roof in vivo has been infrequently explored. The aim of the present study was to delineate the neurovascular structures relevant to the third ventricle roof using magnetic resonance (MR) imaging. METHODS: A total of 78 patients were enrolled in the study. Following initial examinations with conventional MR sequences, the constructive interference in steady-state (CISS) sequence was performed in coronal sections on 67 patients and in sagittal sections on 11 patients. RESULTS: In the coronal sections, the fornices and internal cerebral veins were delineated in all 67 patients. The cross-sectional appearance and size of the fornices were variable, and the relationship between fornices presented as five different types. In 82% of patients, dominance of one relationship type was not found. The diameter of the internal cerebral veins (ICVs) was also variable, and the relationship between ICVs presented as four different types. In 70% of patients, dominance of one relationship type was not found. In 52% of patients, the lower layer of the third ventricle roof was identified as an inhomogeneous membranous structure. In the sagittal sections, the lower layer of the third ventricle roof was delineated as an inhomogeneous linear structure with variable slopes. CONCLUSIONS: The third ventricle roof appears highly variable in morphology. Visualization of the third ventricle roof using the CISS sequence may be useful for planning safe and effective surgical maneuvers around the region.

The trigeminal root: an anatomical study using magnetic resonance imaging.

PURPOSE: The trigeminal root is a remarkable structure that can be an original site of trigeminal neuralgia. However, few studies have explored the detailed anatomy of it with neuroimages. The aim of the present study was to characterize the trigeminal root using magnetic resonance (MR) imaging. METHODS: Thin-sliced, axial T2-weighted imaging and coronal constructive interference in steady-state (CISS) sequence were performed for a total of 167 patients. RESULTS: On axial T2-weighted imaging, three divisions of the main trigeminal sensory root were unequivocally delineated in 36% of the 95 patients. Sixty-three percent of the Meckel's cave was bilaterally adjacent to the petrous portion of the internal carotid artery. On CISS sequence, course of the main trigeminal sensory root was well delineated in all of the 72 patients. The accessory sensory and motor rootlets were identified in 38% and 56% of 144 sides, respectively. Levels of the main trigeminal roots at the original site and entrance into the Meckel's as well morphology of the original segment of the main trigeminal sensory root were variable. Furthermore, in 24% of sides, three divisions of the main trigeminal sensory root were clearly delineated, arranged in variable manners. In 20% sides, segments of the superior cerebellar artery had a contact with the main trigeminal sensory root and motor rootlets. CONCLUSIONS: Coronal CISS sequence is useful for delineating the trigeminal root. Anatomy of the trigeminal root presents considerable inter- and intra-individual variability that can influence the symptoms of trigeminal neurovascular compression.

Visualization of the vidian canal and nerve using magnetic resonance imaging.

BACKGROUND AND PURPOSE: Few studies have investigated the vidian nerve (VN) and vidian canal (VC) with the use of magnetic resonance imaging (MRI). The present study aimed to characterize the VC and VN using MRI. MATERIALS AND METHODS: A total of 91 patients underwent thin-sliced, contrast MRI. The course of the VC and VN and the relationships with relevant structures were analyzed. RESULTS: The VC was identified in 95% of axial images on the right side and in 93% on the left. The course of the VC was delineated in 99% of serial coronal images on both sides. The VN location in the VC was highly variable. The course of the VC and transmitting VN was delineated in 95% of sagittal images on the right side and in 91% on the left. The mean length of the VC was 19.8 mm on the right side and 19.3 mm on the left. Topographical relationships between the anterior genu of the petrous internal carotid artery and the posterior end of the vidian canal could be classified into three types. Of these, the type terminating at the level of the petrous carotid was the most predominant, comprising 76% of 182 sides. The course of the VC and transmitting VN could be classified into four types. The straight type was the most predominant and was found in 41%. CONCLUSIONS: The VC and transmitting VN are structures with variable morphologies. Contrast MRI is useful for delineating the VC and VN.

Visualization of the cavum septi pellucidi, cavum Vergae, and cavum veli interpositi using magnetic resonance imaging.

PURPOSE: The morphology of the cavum septi pellucidi (CSP), cavum Vergae (CV), and cavum veli interpositi (CVI) has been infrequently explored with neuroimaging. The aim of the present study was to delineate these cavities using magnetic resonance (MR) imaging. METHODS: A total of 71 patients were enrolled in the present study. Following initial examinations with conventional MR sequences, constructive interference in steady-state (CISS) sequence was performed in the coronal and sagittal sections for 60 and 11 patients, respectively. RESULTS: The coronal CISS images at the level of the aqueduct showed two distinct morphologies of the CV roof, one formed by the fornices with varying degrees of conjugation and the other formed by the corpus callosum with completely separated fornices. Appearance of the CSP was classified into four distinct types. Furthermore, the CVI presented two distinct appearances. CONCLUSIONS: Typically, the CSP, CV, and CVI present with asymptomatic conditions with morphological variabilities. Visualization of the CSP, CV, and CVI using the CISS sequences may be useful when managing lesions affecting these cavities.

Dorsal extensions of the fastigium cerebelli: an anatomical study using magnetic resonance imaging.

BACKGROUND AND PURPOSE: The fastigium cerebelli is an important topographical landmark for neurosurgeons and radiologists. However, few studies have characterized the morphology of the fastigium cerebelli. We aimed to investigate the fastigium cerebelli using postmortem specimens and magnetic resonance imaging (MRI) in vivo. MATERIALS AND METHODS: Three cadaveric brains were midsagittally sectioned for observing the fastigium cerebelli. Additionally, 66 outpatients underwent MRI, including sagittal T1-weighted imaging, axial T2-weighted imaging, and coronal constructive interference in steady-state (CISS) sequence. RESULTS: In the cadaveric specimens, the fastigium cerebelli was observed as a beak-like dorsal protrusion of the fourth ventricle. Its inner surface was observed as a small fovea. On serial CISS images, the fastigium cerebelli consistently possessed a pair of triangular-shaped, dorsal extensions lying parasagittally along the nodule. These extensions were classified as symmetrical, right-side dominant, or left-side dominant. The symmetrical type was the most predominant and comprised 60.6% of the extensions, while the right-side dominant and left-side dominant types comprised 13.6 and 25.8%, respectively. In 91% of the 66 patients, the number of slices covering the entirety of the dorsal extensions were the same on both sides. The fastigial angle (θ) formed by lines tangent to the superior and inferior medullary velums varied widely. CONCLUSIONS: The fastigium cerebelli has a pair of dorsal extensions lying parasagittally along the nodule. Coronal CISS sequence is useful in delineating the fastigium cerebelli in vivo.

The cisternal segment of the anterior choroidal artery: an anatomical study using magnetic resonance imaging.

PURPOSE: The topography of the anterior choroidal artery (AChA) has infrequently been delineated on neuroimages. The present study aimed to explore the cisternal segment of the AChA using magnetic resonance imaging. METHODS: A total of 50 sides of the AChA obtained from 25 patients were included in this study. A constructive interference in steady-state (CISS) sequence was performed in thin-sliced axial sections. Furthermore, the cisternal AChA and relevant neurovascular structures were observed through cadaveric dissections in two heads. RESULTS: In the cadaveric dissections, all the AChAs were exposed only in the proximal part even after extensive arachnoid dissections and cerebral retraction. In the examinations with the CISS sequence, the original site of the AChA was identified on the right side in 88% and on the left side in 96%. In 70% of the 50 sides, the AChA arose from the posterolateral wall of the internal carotid artery, distally to that of the posterior communicating artery. The cisternal course of the AChA was delineated on the right side in 96% and on the left side in 100%; it crossed over the optic tract in variable manners with the middle third as the most frequent site found in 60% of the sides. CONCLUSIONS: The cisternal AChA shows a morphological variability. The CISS sequence is useful for delineating the cisternal AChA.

Immobile cerebral veins in the context of positional brain shift: an undescribed risk factor for acute subdural hemorrhage.

BACKGROUND: Changes in head position are thought to cause a degree of brain shift in the intracranial cavity. However, little is known on the concurrent shift of the cerebral veins. The present study aimed to investigate the positional shift of the cerebral veins that accompanies brain shift. METHODS: Sagittal T2-weighted magnetic resonance imaging was performed on 21 consecutive patients lying in the supine and prone positions, using the same sequence. For each patient, imaging data were obtained for the two positions as a pair of images with morphologically best-matched cerebral contours. RESULTS: The subarachnoid spaces in the parasagittal frontal convexity showed variable reductions related to a postural change from a supine to a prone position, with a mean percent reduction (%Δ) of 17.8 ± 11.7%. Additionally, cerebral cisterns ventral to the brainstem and upper cervical cord were reduced in most patients when lying in a prone position, with a mean %Δ of 16.6 ± 8.7%. In contrast, none of these 130 pairs of identical venous segments located in the parasagittal cerebral convexity showed positional shift. Cadaveric dissections found that the major cortical veins were superficially upheld by the arachnoid membranes. CONCLUSIONS: The parasagittal major cortical and bridging veins do not seem to show positional shifts. Positional change in the posterior-anterior direction causes a shearing between the frontal cortices and the distributing veins and can be a risk factor for acute subdural hemorrhage, in case of severe head trauma.