The intracranial bridging veins: a comprehensive review of their history, anatomy, histology, pathology, and neurosurgical implications

Vascular microforamina and endocranial surface: Normal variation and distribution in adult humans: Vascular biology

The term craniovascular traits refers to the imprints left by arteries and veins on the skull bones. These features can be used in biological anthropology and archaeology to investigate the morphology of the vascular network in extinct species and past populations. Generally, the term refers to macrovascular features of the endocranial cavity, like those associated with the middle meningeal artery, venous sinuses, emissary foramina, and diploic channels. However, small vascular passages (here called microforamina or microchannels) have been occasionally described on the endocranial surface. The larger ones (generally with a diameter between 0.5 and 2.0 mm) can be detected through medical scanners on osteological collections. In this study, we describe and quantify the number and distribution of these microforamina in adult humans (N = 45) and, preliminarily, in a small sample of children (N = 7). Adults display more microchannels than juvenile skulls. A higher frequency in females is also observed, although this result is not statistically significant and might be associated with allometric cranial variations. The distribution of the microforamina is particularly concentrated on the top of the vault, in particular along the sagittal, metopic, and coronal sutures, matching the course of major venous sinuses and parasagittal bridging veins. Nonetheless, the density is lower in the region posterior to bregma. Beyond oxygenation, these vessels are likely involved in endocranial thermal regulation, infection, inflammation, and immune responses, and their distribution and prevalence can hence be of interest in human biology, evolutionary anthropology, and medicine.

On the spinal venous sinus of Alligator mississippiensis

The epidural space of the American alligator (Alligator mississippiensis) is largely filled by a continuous venous sinus. This venous sinus extends throughout the trunk and tail of the alligator, and is continuous with the dural sinuses surrounding the brain. Segmental spinal veins (sl) link the spinal venous sinus (vs) to the somatic and visceral venous drainage. Some of these sl, like the caudal head vein along the occipital plate of the skull, are enlarged, suggesting more functional linkage. No evidence of venous valves or external venous sphincters was found associated with the vs; the relative scarcity of smooth muscle in the venous wall of the sinus suggests limited physiological regulation. The proatlas (pr), which develops between the occipital plate and C1 in crocodylians, is shaped like a neural arch and is fused to the dorsal surface of the vs. The present study suggests that the pr may function to propel venous blood around the brain and spinal cord. The vs effectively encloses the spinal dura, creating a tube-within-a-tube system with the (smaller volume) spinal cerebrospinal fluid (CSF). Changes in venous blood pressure, as are likely during locomotion, would impact dural compliance and CSF pressure waves propagating along the spinal cord.

Handling Severe Intraoperative Hemorrhage and Avoiding Iatrogenic Stroke During Brain Tumor Surgery: Techniques for Prevention of Hemorrhagic and Ischemic Complications

BACKGROUND

Nationwide databases show that iatrogenic stroke and postoperative hematoma are among the commonest complications in brain tumor surgery, with a 10-year incidence of 16.3/1000 and 10.3/1000, respectively. However, techniques for handling severe intraoperative hemorrhage and dissecting, preserving, or selectively obliterating vessels traversing the tumor are sparse in the literature.

METHODS

Records of the senior author's intraoperative techniques during severe haemorrhage and vessel preservation were reviewed and analyzed. Intraoperative media demonstrations of key techniques were collected and edited. In parallel, a literature search investigating technique description in handling severe intraoperative hemorrhage and vessel preservation in tumor surgery was undertaken. Histologic, anesthetic, and pharmacologic prerequisites of significant hemorrhagic complications and hemostasis were analyzed.

RESULTS

The senior author's techniques for arterial and venous skeletonization, temporary clipping with cognitive or motor mapping, and ION monitoring were categorized. Vessels interfacing with tumor are labeled intraoperatively as supplying/draining the tumor, or traversing en passant, while supplying/draining functional neural tissue. Intraoperative techniques of differentiation were analyzed and illustrated. Literature search found 2 vascular-related complication domains in tumor surgery: perioperative management of excessively vascular intraparenchymal tumors and lack of intraoperative techniques and decision processes for dissecting and preserving vessels interfacing or traversing tumors.

CONCLUSIONS

Literature searches showed a dearth of complication-avoidance techniques in tumor-related iatrogenic stroke, despite its high prevalence. A detailed preoperative and intraoperative decision process was provided along with a series of case illustrations and intraoperative videos showing the techniques required to reduce intraoperative stroke and associated morbidity addressing a void in complication avoidance of tumor surgery.

Mechanical Thrombectomy with Tandem Double Stent Retriever in Combination with Intermediate Catheter Aspiration for Refractory Severe Hemorrhagic Cerebral Venous Sinus Thrombosis

OBJECTIVE

We aimed to describe the initial experience of mechanical thrombectomy using tandem double stent retrievers combined with intermediate catheter aspiration to treat refractory severe hemorrhagic (SH)-cerebral venous sinus thrombosis (CVST).

METHODS

All refractory SH-CVST patients treated with mechanical thrombectomy using tandem double stent retriever (SR) combined with intermediate catheter aspiration (MT-TDSA) in our institution were retrospectively reviewed. MT-TDSA is a technique that fully engages the clot with double SRs and retrieves the clot using a double SR in combination with aspiration from an intermediate catheter. Demographics, clinical manifestation, medical history, the location of the occluded venous sinus, intraoperative details, procedure-related complications, and modified Rankin Scale (1, 6, 12 months postoperatively) were collected and analyzed.

RESULTS

Fourteen patients (median age, 43 years) with refractory SH-CVST were treated with MT-TDSA between January 2016 and January 2020. Ten of 14 (71.4%) had a successful intraoperative recanalization rate (>90%) using MT-TDSA. No procedure-related complications occurred. Eleven patients had good clinical outcomes (modified Rankin Scale score 0-2 at 12 months postoperatively).

CONCLUSIONS

MT-TDSA for refractory SH-CVST might improve clot-capturing ability and remove blood clots from cerebral venous sinuses effectively and safely, achieving good clinical outcomes.

Diploic vein morphology in normal and craniosynostotic adult human skulls

Diploic veins (DV) run within the cranial diploe, where they leave channels that can be studied in osteological samples. This study investigates overall DV variability in human adults and the effects of sex, age, cranial dimensions, and dysmorphogenesis associated with craniosynostosis (CS). The morphology of macroscopic diploic channels was analyzed in a set of the qualitative and quantitative variables in computed tomography-images of crania of anatomically normal and craniosynostotic adult individuals. Macroscopic diploic channels occur most frequently in the frontal and parietal bones, often with a bilaterally symmetrical pattern. DV-features (especially DV-pattern) are characterized by high individual diversity. On average, there are 5.4 ± 3.5 large macroscopic channels (with diameters >1 mm) per individual, with a mean diameter of 1.7 ± 0.4 mm. Age and sex have minor effects on DV, and cranial proportions significantly influence DV only in CS skulls. CS is associated with changes in the DV numbers, distributions, and diameters. Craniosynostotic skulls, especially brachycephalic skulls, generally present smaller DV diameters, and dolichocephalic skulls display increased number of frontal DV. CS, associated with altered cranial dimensions, suture imbalance, increased intracranial pressure, and with changes of the endocranial craniovascular system, significantly also affects the macroscopic morphology of DV in adults, in terms of both structural (topological redistribution) and functional factors. The research on craniovascular morphology and CS may be of interest in biological anthropology, paleopathology, medicine (e.g., surgical planning), but also in zoology and paleontology.

Anatomy of Intracranial Veins

The cerebral venous system is complex and sophisticated and serves various major functions toward maintaining brain homeostasis. Cerebral veins contain about 70% of cerebral blood volume, have thin walls, are valveless, and cross seamlessly white matter, ependymal, cisternal, arachnoid, and dural boundaries to eventually drain cerebral blood either into dural sinuses or deep cerebral veins. Although numerous variations in the cerebral venous anatomic arrangement may be encountered, the overall configuration is relatively predictable and landmarks relatively well defined. A reasonable understanding of cerebral vascular embryology is helpful to appreciate normal anatomy and variations that have clinical relevance. Increasing interest in transvascular therapy, particularly transvenous endovascular intervention provides justification for practitioners in the neurosciences to acquire at least a basic understanding of the cerebral venous system.

Chronic subdural hemorrhage predisposes to development of cerebral venous thrombosis and associated retinal hemorrhages and subdural rebleeds in infants

For infants presenting with subdural hemorrhage, retinal hemorrhage, and neurological decline the "consensus" opinion is that this constellation represents child abuse and that cerebral venous sinus thrombosis and cortical vein thrombosis is a false mimic. This article contends that this conclusion is false for a subset of infants with no evidence of spinal, external head, or body injury and is the result of a poor radiologic evidence base and misinterpreted data. Underdiagnosis of thrombosis is the result of rapid clot dissolution and radiologic under recognition. A pre-existing/chronic subdural hemorrhage predisposes to development of venous sinus thrombosis/cortical vein thrombosis, triggered by minor trauma or an acute life-threatening event such as dysphagic choking, variably leading to retinal and subdural hemorrhages and neurologic decline. These conclusions are based on analysis of the neuroradiologic imaging findings in 11 infants, all featuring undiagnosed cortical vein or venous sinus thrombosis. Subtle neuroradiologic signs of and the mechanisms of thrombosis are discussed. Subarachnoid hemorrhage from leaking thrombosed cortical veins may be confused with acute subdural hemorrhage and probably contributes to the development of retinal hemorrhage ala Terson's syndrome. Chronic subdural hemorrhage rebleeding from minor trauma likely occurs more readily than bleeding from traumatic bridging vein rupture. Radiologists must meet the challenge of stringent evaluation of neuro imaging studies; any infant with a pre-existing subdural hemorrhage presenting with neurologic decline must be assumed to have venous sinus or cortical vein thrombosis until proven otherwise.

Rapid Spontaneous Resolution of Contralateral Lentiform Acute Subdural Hematoma After Burr Hole Trephination for Chronic Subdural Hematoma

Although rare, acute subdural hematoma (ASDH) may occur after burr hole trephination (BHT) for chronic subdural hematoma (CSDH). It usually occurs in the hemisphere ipsilateral to the burr hole site and rarely in the hemisphere contralateral to the burr hole site. On computed tomography (CT), SDH is usually crescent-shaped and occasionally lentiform or biconvex, which can be misdiagnosed as epidural hematoma (EDH). In rare cases, ASDH may resolve spontaneously and rapidly. Here, we report a case of rapid spontaneous resolution of contralateral lentiform ASDH after BHT for CSDH in a patient with brain atrophy. A 55-year-old man developed left CSDH 2 months after traumatic brain injury. Left BHT was performed, and a lentiform hematoma, presumed to be EDH, was found in the right frontal region on the CT scan acquired immediately after BHT. On the CT scan acquired 12 hours later, the lentiform hematoma disappeared and spread along the hemisphere. It was presumed to be ASDH. To prevent contralateral ASDH after BHT, slow decompression and minimal gentle or no irrigation should be performed during BHT, particularly in patients with brain atrophy.

Suboccipital Transhorizontal Fissure Approach for Posterior Cranial Fossa Lesions: A Cadaveric Study and First Clinical Experience

BACKGROUND

Surgical treatment of pathological lesions in the deep cerebellar hemisphere, cerebellopontine angle (CPA), and fourth ventricle of the posterior cranial fossa (PCF) is challenging. Conventional neurosurgical approaches to these lesions are associated with risk of various complications. Mastery of efficient fissure dissection is imperative when approaching deep-seated lesions. The horizontal fissure (HF) is the largest and deepest fissure of the cerebellum.

OBJECTIVE

To conduct an anatomical study and introduce a novel suboccipital trans-HF (SOTHF) approach to access lesions of the deep cerebellar hemispheres, CPA, and upper fourth ventricle of the PCF.

METHODS

We performed a cadaveric dissection study focusing on anatomical landmarks and surgical feasibility of the SOTHF approach then implemented it in 2 patients with a deep cerebellar hemispheric tumor.

RESULTS

Anatomical feasibility of the SOTHF approach was demonstrated and compared with conventional approaches in the cadaveric study. Opening the suboccipital surface of the HF to create medial, intermediate, and lateral surgical corridors provided optimal viewing angles and wide access to the deep cerebellar hemispheres, CPA, and upper fourth ventricle without heavy cerebellar retraction. Sacrificing cerebellar neural structures and complex skull base techniques were not required to obtain adequate exposure. The SOTHF approach was successfully applied without complication in 2 patients with a deep cerebellar hemispheric tumor.

CONCLUSION

The HF is an important cerebellar fissure that provides a gateway to deep areas of the PCF. Further studies are needed to define and expand applications of the SOTHF approach.

Thrombosis is not a marker of bridging vein rupture in infants with alleged abusive head trauma

Aim

Thrombosis of bridging veins has been suggested to be a marker of bridging vein rupture, and thus AHT, in infants with subdural haematoma.

Methods

This is a non‐systematic review based on Pubmed search, secondary reference tracking and authors’ own article collections.

Results

Radiological studies asserting that imaging signs of cortical vein thrombosis were indicative of traumatic bridging vein rupture were unreliable as they lacked pathological verification of either thrombosis or rupture, and paid little regard to medical conditions other than trauma. Autopsy attempts at confirmation of ruptured bridging veins as the origin of SDH were fraught with difficulty. Moreover, microscopic anatomy demonstrated alternative non‐traumatic sources of a clot in or around bridging veins. Objective pathological observations did not support the hypothesis that a radiological finding of bridging vein thrombosis was the result of traumatic rupture by AHT. No biomechanical models have produced reliable and reproducible data to demonstrate that shaking alone can be a cause of bridging vein rupture.

Conclusion

There is no conclusive evidence supporting the hypothesis that diagnostic imaging showing thrombosed bridging veins in infants correlates with bridging vein rupture. Hence, there is no literature support for the use of thrombosis as a marker for AHT.

[Bridging vein injuries in shaken baby syndrome : Forensic-radiological meta-analysis with special focus on the tadpole sign]

Shaken baby syndrome is a common variant of the abusive head trauma in infants and toddlers and is still subject of intensive research. In recent years, a number of radiological studies on the diagnostic and forensic relevance of injured bridging veins were conducted using different imaging modalities. The present article will give an overview on the current state of research in this field and will discuss the forensic implications. The meta-analysis of the seven currently existing studies revealed that injuries of the bridging veins and bridging vein thromboses, respectively, frequently appear as rounded, enlarged, and/or tubular structures. The "tadpole sign" may serve as a valuable tool for the identification of these formations. Especially, T2*/SWI (susceptibility-weighted imaging) sequences allow for good detectability of these lesions and should always be generated when abusive head trauma is suspected. In conclusion, it can be recommended that the presence of radiologically detectable bridging vein injuries should give reason to search for other manifestations of physical child abuse.

Relationship of superior sagittal sinus with sagittal midline: A surgical application

Background:

Interhemispheric approach is widely used to surgical management of midline tumors and vascular lesion in and around the third ventricle. Complete exposure of the superior sagittal sinus to obtain adequate working space of midline lesion is difficult, because of the risk to inadvertent injury to the sinus and bridging veins, which may cause several neurological deficits. Understanding the SSS neuroanatomy and its relationships with external surgical landmarks avoid such complications. The objective of this study is to accurately describe the position of SSS and its displacement in relation with sagittal midline by magnetic resonance imaging.

Methods:

A retrospective cross-sectional, observational study was performed. Magnetic resonance image of 76 adult patients with no pathological imaging was analyzed. The position of the halfway between nasion and bregma, bregma, halfway between bregma and lambda, and lambda was performed. The width and the displacement of the superior sagittal sinus accordingly to the sagittal midline were assessed in those landmarks.

Results:

The mean width of superior sagittal sinus at halfway between nasion and bregma, bregma, halfway between bregma and lambda, and lambda was 5.62 ± 2.5, 6.5 ± 2.8, 7.4 ± 3.2, and 8.5 ± 2.1 mm, respectively, without gender discrepancy. The mean displacement according to the midline at those landmarks showed a statistically significant difference to the right side among sexes.

Conclusion:

In this study, we demonstrate that sagittal midline may approximate external location of the superior sagittal sinus. Our data showed that in the majority of the cases, the superior sagittal sinus is displaced to the right side of sagittal midline as far as 16.3 mm. The data we obtained provide useful information that suggest that neurosurgeons should use safety margin to perform burr holes and drillings at the sagittal midline.

Cortical and bridging veins of the upper cerebral convexity: a magnetic resonance imaging study

PURPOSE

There is no study exploring the cortical veins (CVs) and connecting bridging veins (BVs) with neuroimaging modalities. The present study aimed to characterize these veins of the upper cerebral convexity.

METHODS

A total of 89 patients with intact cerebral hemispheres and covering meninges underwent thin-sliced, contrast magnetic resonance imaging (MRI). In addition, three injected specimens were dissected in this study.

RESULTS

In cadaver dissection, the BVs were observed to course in the arachnoid sheaths, suspended from the dura mater. The medial parts of the BVs, located near the superior sagittal sinus (SSS)-BV junction site, were occasionally exposed subdurally. The CVs were formed by venous channels arising from the cerebral gyri and those emerging from the sulci. On MRI, the CVs and connecting BVs were identified in the medial and latera convexity areas and medial surface of the cerebrum. These veins were highly variable in number, thickness, length, course, and distribution. In the medial convexity area, the CVs arising from the gyri were identified in 58% of patients, while they were found only in 11% of patients in the lateral convexity area.

CONCLUSION

In the medial convexity area, involving the parasagittal region, the CVs connect more densely with the BVs that may predispose to injury during neurosurgical procedures. Mechanical impact exerted the area, diameter of the veins in the craniocaudal direction, and number of venous afferences may affect the SSS-BV junctional region in an indirect manner and lead to the development of acute subdural hematoma.

Tortuosity of superior cerebral veins: Comparative magnetic resonance imaging morphometrics in normal subjects and arteriovenous malformation patients

Blood vessel tortuosity results from increased diameter and length in response to higher hemodynamic loads. Tortuosity metrics have not been determined for abnormal superior cerebral veins (SCVs) draining cerebral arteriovenous malformations (AVMs). Draining vein (DV) tortuosity may influence safety and efficacy of retrograde microcatheter navigation during transvenous treatment of pial AVMs. Here, we quantify SCV tortuosity in normal subjects and AVM patients using two image segmentation methods. We used contrast-enhanced brain magnetic resonance (MR) images to define the axis of each SCV through a regularly spaced set of three-dimensional (3D) points defining its skeleton curve. We then calculated two metrics: the "sum of angles metric" (SOAM), which adds all angles of curvature along a vessel and normalizes by vessel length, and the "distance metric" (DM), a tortuosity measure providing a ratio of vessel length to linear distance between vessel endpoints. We analyzed 168 metrics in 43 veins of eight normal subjects and 41 veins of seven AVM patients. In normal subjects, the mean SOAM and DM for SCVs were 21.34 ± 7.49 °/mm and 1.42 ± 0.25, respectively. In AVM patients, DVs had a significantly higher mean SOAM of 30.43 ± 11.38 °/mm (p = .02) and DM of 2.79 ± 1.77 (p = .01) than normal subjects. In AVM patients, DVs were significantly more tortuous than matched contralateral uninvolved SCVs, which were similar in tortuosity to normal subject SCVs. We thus report normative tortuosity metrics of brain SCVs and show that AVM cortical DVs are significantly more tortuous than normal SCVs. Knowledge of these comparative tortuosities is valuable in planning endovenous AVM embolotherapies.

Venous anatomy of the supratentorial compartment

The cerebral venous drainage system in humans has several unique characteristics that set it apart from its arterial counterpart. The intracranial drainage system can be broadly divided into supra- and infratentorial components. The supratentorial venous drainage is further subclassified into superficial and deep systems, each with a unique set of features. A thorough knowledge of the normal and variant venous drainage pathways is important to understand the different pathologic processes involving the venous vasculature, to identify and anticipate the different venous channels encountered during surgery and also to predict the possible sequelae of intentional or inadvertent venous sacrifice during surgery. This chapter summarizes the anatomic and radiologic characteristics of the venous supply of the supratentorial compartment of the brain, reviews its general characteristics, sheds light on the different classifications and nomenclature used for its descriptions, and briefly discusses its embryologic development.

Three-Dimensional Angles of Confluence of Cortical Bridging Veins and the Superior Sagittal Sinus on MR Venography: Does Drainage of Adjacent Brain Arteriovenous Malformations Alter this Spatial Configuration?

Few neuroimaging anatomic studies to date have investigated in detail the point of entry of cortical bridging veins (CBVs) into the superior sagittal sinus (SSS). Although we know that most CBVs join the SSS at an acute angle opposite to the direction of SSS blood flow, the three-dimensional (3-D) spatial configuration of these venous confluences has not been studied previously. This anatomical information would be pertinent to several clinically applicable scenarios, such as in planning intracranial surgical approaches that preserve bridging veins; studying anatomical factors in the pathophysiology of SSS thrombosis; and when planning endovascular microcatheterization of pial veins to retrogradely embolize brain arteriovenous malformations (AVMs). We used the concept of Euclidean planes in 3-D space to calculate the arccosine of these CBV-SSS angles of confluence. To test the hypothesis that pial AVM draining veins may not be any more acutely angled or difficult to microcatheterize at the SSS than for normal CBVs, we measured 70 angles of confluence on magnetic resonance venography images of 11 normal, and nine AVM patients. There was no statistical difference between normal and AVM patients in the CBV-SSS angles projected in 3-D space (56.2° [SD = 22.4°], and 46.2° [SD = 22.3°], respectively; P > 0.05). Hence, participation of CBVs in drainage of pial AVMs should not confer any added difficulty to their microcatheterization across the SSS, when compared to the acute angles found in normal individuals. This has useful implications for potential choices of strategies requiring endovascular transvenous retrograde approaches to treat AVMs. Clin. Anat. 33:293-299, 2020. © 2019 Wiley Periodicals, Inc.

Normal craniovascular variation in two modern European adult populations

The vascular networks running into the meningeal layers, between the brain and braincase, leave imprints on the endocranial surface. These traces are visible in osteological specimens and skeletal collections, providing indirect evidence of vascular patterns in those cases in which bone remains are the only source of anatomical information, such as in forensic science, bioarchaeology and paleontology. The main vascular elements are associated with the middle meningeal artery, the venous sinuses of the dura mater, and the emissary veins. Most of these vascular systems have been hypothesized to be involved in endocranial thermal regulation. Although these traits deal with macroanatomical features, much information on their variation is still lacking. In this survey, we analyze a set of craniovascular imprints in two European dry skull samples with different neurocranial proportions: a brachycephalic Czech sample (n = 103) and a mesocephalic Italian sample (n = 152). We analyzed variation and distribution, correlation with cranial metrics, and sex differences in the dominance of the branches of the middle meningeal artery, the patterns of confluence of the sinuses, and the size of the emissary foramina. The descriptive statistics provide a reference to compare specimens and samples from different case studies. When compared with the Italian skulls, the Czech skulls display a greater dominance of the anterior branch of the middle meningeal artery and more asymmetric right-dominance of the confluence of the venous sinuses. There is no sex difference in the middle meningeal vessels, but males show a greater prevalence of the occipito-marginal draining system. Differences in the middle meningeal vessels or venous sinuses are apparently not influenced by cranial dimensions or proportions. The mastoid foramina are larger in larger and more brachycephalic skulls, which increases the emissary potential flow in the Czech sample and males, when compared with the Italian samples and females, respectively. The number of mastoid foramina increases in wider skulls. This anatomic information is necessary to develop further morphological and functional inferences on the relationships between neurocranial bones and vessels at the genetic, ontogenetic, and phylogenetic levels.

Ocular and Intracranial MR Imaging Findings in Abusive Head Trauma

Abusive head trauma (AHT) is a form of inflicted head injury. AHT is more frequent in 2-year-old or younger children. It is an important cause of neurological impairment and the major cause of death from head trauma in this age group. Brain magnetic resonance imaging allows the depiction of retinal hemorrhages, injured bridging veins, and identifying and localizing extra- and intra-axial bleeds, contusions, lacerations, and strokes. The diagnosis of AHT is a multidisciplinary team effort which includes a careful evaluation of social, clinical, laboratory, and radiological findings. Notwithstanding, the introduction in the current clinical practice of high-resolution techniques is adding forensic evidence to the recognition of AHT.

Quantitative Endoscopic Comparison of Contralateral Interhemispheric Transprecuneus and Supracerebellar Transtentorial Transcollateral Sulcus Approaches to the Atrium

OBJECTIVE

The contralateral interhemispheric transprecuneus approach (CITP) and the supracerebellar transtentorial transcollateral sulcus approach (STTC) are 2 novel approaches to access the atrium of the lateral ventricle. We quantitatively compared the 2 approaches.

METHODS

Both approaches were performed in 6 sides of fixed and color-injected cadaver heads. We predefined the 6 targets in the atrium for measurement and standardization of the approaches. Using a navigation system, we quantitatively measured the working distance, cortical transgression, angle of attack, area of exposure, and surgical freedom.

RESULTS

The distances from the craniotomy edge to the posterior pole of the choroid plexus of the CITP (mean ± standard deviation, 67 ± 5.3 mm) and STTC (mean, 57 ± 4.0 mm) differed significantly (P < 0.01). Cortical transgression with the CITP (mean, 27 ± 2.8 mm) was significantly greater than that with the STTC (mean, 21 ± 6.7 mm; P = 0.03). The CITP showed a significantly wider rostrocaudal angle of attack than that with the STTC (P = 0.01). The STTC showed a significantly wider mediolateral angle (P < 0.01). No significant difference was found for surgical freedom of any target except for point E, for which the CITP was larger. The exposure area did not differ significantly between the 2 approaches (P = 0.07).

CONCLUSIONS

Both approaches were feasible for accessing the atrium. The STTC provided a shorter working distance and wider mediolateral angle, CITP provided a wider rostrocaudal angle of attack and better exposure and maneuverability to the anterior and superior atrium. In contrast, the STTC was more favorable for the inferior and posterior regions.

Trans-falcine and contralateral sub-frontal electrode placement in pediatric epilepsy surgery: technical note

INTRODUCTION

Phase II monitoring with intracranial electroencephalography (ICEEG) occasionally requires bilateral placement of subdural (SD) strips, grids, and/or depth electrodes. While phase I monitoring often demonstrates a preponderance of unilateral findings, individual studies (video EEG, single photon emission computed tomography [SPECT], and positron emission tomography [PET]) can suggest or fail to exclude a contralateral epileptogenic onset zone. This study describes previously unreported techniques of trans-falcine and sub-frontal insertion of contralateral SD grids and depth electrodes for phase II monitoring in pediatric epilepsy surgery patients when concern about bilateral abnormalities has been elicited during phase I monitoring.

METHODS

Pediatric patients with medically refractory epilepsy undergoing stage I surgery for phase II monitoring involving sub-frontal and/or trans-falcine insertion of SD grids and/or depth electrodes at the senior author's institution were retrospectively reviewed. Intra-operative technical details of sub-frontal and trans-falcine approaches were studied, while intra-operative complications or events were noted. Operative techniques included gentle subfrontal retraction and elevation of the olfactory tracts (while preserving the relationship between the olfactory bulb and cribriform plate) to insert SD grids across the midline for coverage of the contralateral orbito-frontal regions. Trans-falcine approaches involved accessing the inter-hemispheric space, bipolar cauterization of the anterior falx cerebri below the superior sagittal sinus, and sharp dissection using a blunt elevator and small blade scalpel. The falcine window allowed contralateral SD strip, grid, and depth electrodes to be inserted for coverage of the contralateral frontal regions.

RESULTS

The study cohort included seven patients undergoing sub-frontal and/or trans-falcine insertion of contralateral SD strip, grid, and/or depth electrodes from February 2012 through June 2015. Five patients (71%) experienced no intra-operative events related to contralateral ICEEG electrode insertion. Intra-operative events of frontal territory venous engorgement (1/7, 14%) due to sacrifice of anterior bridging veins draining into the SSS and avulsion of a contralateral bridging vein (1/7, 14%), probably due to prior anterior corpus callosotomy, each occurred in one patient. There were no intra-operative or peri-operative complications in any of the patients studied. Two patients required additional surgery for supplemental SD strip and/or depth electrodes via burr hole craniectomy to enhance phase II monitoring. All patients proceeded to stage II surgery for resection of ipsilateral epileptogenic onset zones without adverse events.

CONCLUSIONS

Trans-falcine and sub-frontal insertion of contralateral SD strip, grid, and depth electrodes are previously unreported techniques for achieving bilateral frontal coverage in phase II monitoring in pediatric epilepsy surgery. This technique obviates the need for contralateral craniotomy and parenchymal exposure with limited, remediable risks. Larger case series using the method described herein are now necessary.

Anatomic comparison of veins of Labbé between autopsy, digital subtraction angiography and computed tomographic venography

Objective

The drainage portion of the vein of Labbé varies, and it is difficult to predict whether the operation is likely to damage this vein. The aim of this study was to correlate the microanatomy of the vein of Labbé with digital subtraction angiography (DSA) and computed tomographic venography (CTV), in order to provide a basis for the preservation of the vein of Labbé during a supratentorial surgical approach.

Methods

A total of 30 human cadavers (60 sides) and 61 living patients (110 sides) were examined in this study. Each cadaver head was injected with blue latex via the superior sagittal sinus and the internal jugular veins. The venograms of each patient were obtained from the venous phases of DSA (60 sides for 36 patients) or CTV (50 sides for 25 patients).

Results

The patients were divided into four subgroups based on the location where a vein entered the dural sinus: the transverse sinus group, the tentorial group, the petrosal group, and the upper-transverse sinus group. The veins of Labbé in transverse sinus group and petrosal group directly entered dural sinus. The veins of Labbé in tentorial group and upper-transverse sinus group indirectly entered transverse sinus via the tentorium sinus or the upper-transverse sinus. These sinuses were meningeal veins running through two layers of the cerebral dura mater. The length of meningeal veins in these groups was 10.0 ± 7.2 mm. The veins of Labbé were mainly localized around the STP junction, which was the confluence of sigmoid sinus, transverse sinus, and superior petrosal sinus. The distance between the dural entrance of veins and the STP junction was 16.8 ± 10.2 mm. There was no significant difference in the results of the DSA and CTV examinations when compared to the observations in cadavers.

Conclusions

Preoperative venograms are useful to design an individualized surgical approach for the preservation of the vein of Labbé. In general, the supratentorial median approach has the least chance to damage this vein. However, when preoperative venograms show that the vein of Labbé is too close to the confluence of sinuses or the meningeal veins are too long, an alternative approach should be chosen.

Where are we? The anatomy of the murine cortical meninges revisited for intravital imaging, immunology, and clearance of waste from the brain

Rapid progress is being made in understanding the roles of the cerebral meninges in the maintenance of normal brain function, in immune surveillance, and as a site of disease. Most basic research on the meninges and the neural brain is now done on mice, major attractions being the availability of reporter mice with fluorescent cells, and of a huge range of antibodies useful for immunocytochemistry and the characterization of isolated cells. In addition, two-photon microscopy through the unperforated calvaria allows intravital imaging of the undisturbed meninges with sub-micron resolution. The anatomy of the dorsal meninges of the mouse (and, indeed, of all mammals) differs considerably from that shown in many published diagrams: over cortical convexities, the outer layer, the dura, is usually thicker than the inner layer, the leptomeninx, and both layers are richly vascularized and innervated, and communicate with the lymphatic system. A membrane barrier separates them and, in disease, inflammation can be localized to one layer or the other, so experimentalists must be able to identify the compartment they are studying. Here, we present current knowledge of the functional anatomy of the meninges, particularly as it appears in intravital imaging, and review their role as a gateway between the brain, blood, and lymphatics, drawing on information that is scattered among works on different pathologies.

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.

Bridging veins and autopsy findings in abusive head trauma

Bridging veins are crucial for the venous drainage of the brain. They run as short and straight bridges between the brain surface and the superior sagittal sinus in the subdural compartment. Subdural bleeding is a marker for a traumatic mechanism (i.e., acceleration/deceleration, rotational and shearing forces due to violent shaking) causing rupture of the bridging veins. Demonstration of bridging vein rupture allows the unequivocal diagnosis of a traumatic mechanism and should therefore be a routine part of the postmortem in cases of subdural hemorrhage.

Cranial dural arteriovenous shunts. Part 1. Anatomy and embryology of the bridging and emissary veins

We reviewed the anatomy and embryology of the bridging and emissary veins aiming to elucidate aspects related to the cranial dural arteriovenous fistulae. Data from relevant articles on the anatomy and embryology of the bridging and emissary veins were identified using one electronic database, supplemented by data from selected reference texts. Persisting fetal pial-arachnoidal veins correspond to the adult bridging veins. Relevant embryologic descriptions are based on the classic scheme of five divisions of the brain (telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon). Variation in their exact position and the number of bridging veins is the rule and certain locations, particularly that of the anterior cranial fossa and lower posterior cranial fossa are often neglected in prior descriptions. The distal segment of a bridging vein is part of the dural system and can be primarily involved in cranial dural arteriovenous lesions by constituting the actual site of the shunt. The veins in the lamina cribriformis exhibit a bridging-emissary vein pattern similar to the spinal configuration. The emissary veins connect the dural venous system with the extracranial venous system and are often involved in dural arteriovenous lesions. Cranial dural shunts may develop in three distinct areas of the cranial venous system: the dural sinuses and their interfaces with bridging veins and emissary veins. The exact site of the lesion may dictate the arterial feeders and original venous drainage pattern.

Structural and mechanical characterisation of bridging veins: A review

Bridging veins drain the venous blood from the cerebral cortex into the superior sagittal sinus (SSS) and doing so they bridge the subdural space. Despite their importance in head impact biomechanics, little is known about their properties with respect to histology, morphology and mechanical behaviour. Knowledge of these characteristics is essential for creating a biofidelic finite element model to study the biomechanics of head impact, ultimately leading to the improved design of protective devices by setting up tolerance criteria. This paper presents a comprehensive review of the state-of-the-art knowledge on bridging veins. Tolerance criteria to prevent head injury through impact have been set by a number of research groups, either directly through impact experiments or by means of finite element (FE) simulations. Current state-of-the-art FE head models still lack a biofidelic representation of the bridging veins. To achieve this, a thorough insight into their nature and behaviour is required. Therefore, an overview of the general morphology and histology is provided here, showing the clearly heterogeneous nature of the bridging vein complex, with its three different layers and distinct morphological and histological changes at the region of outflow into the superior sagittal sinus. Apart from a complex morphology, bridging veins also exhibit complex mechanical behaviour, being nonlinear, viscoelastic and prone to damage. Existing material models capable of capturing these properties, as well as methods for experimental characterisation, are discussed. Future work required in bridging vein research is firstly to achieve consensus on aspects regarding morphology and histology, especially in the outflow cuff segment. Secondly, the advised material models need to be populated with realistic parameters through biaxial mechanical experiments adapted to the dimensions of the bridging vein samples. Finally, updating the existing finite element head models with these parameters will render them truly biofidelic, allowing the establishment of accurate tolerance criteria and, ultimately, better head protection devices.