Falcine venous plexus within the falx cerebri: anatomical and scanning electron microscopic findings and clinical significance

Background

Only limited attention has been paid to the anatomy and clinical importance of the falcine venous plexus. The aim of this study was to evaluate the falcine venous plexus anatomically using scanning electron microscopy (SEM), and to provide guidance for neurosurgical approaches.

Methods

Latex or ink was injected into the superior and inferior sagittal sinus. The falcine venous plexus lying within the connective tissue of the falx cerebri was observed by dividing the falx into thirds (anterior, middle and posterior). Further, the SEM appearance of the falcine venous plexus was evaluated.

Results

The anterior third of the falx cerebri consisted of small diameter falcine venous vessels. These vessels were localized close to either the superior or inferior sagittal sinus, and none extended as far as mid-falx cerebri levels in any of the 16 cases. They communicated with either superior or inferior sagittal sinuses, but not with both of these sinuses. In the middle third of the falx cerebri, the majority of the vessels of the falcine venous plexus had larger diameter compared to those of the anterior third. These vessels extended the length of the falx cerebri levels. They communicated with both superior and inferior sagittal sinuses. In the posterior third of the falx cerebri, the vessels of the falcine venous plexuses had the largest diameter and were located at the junction of the inferior sagittal sinus and the straight sinus. They were localized at the lower two-thirds of the falx cerebri. In all cases, the dense venous networks communicated with the inferior sagittal sinus but not with the superior sagittal sinus. The falcine venous plexus observed in the posterior third of the falx cerebri was denser than in the anterior and middle portions. The SEM revealed small vessels whose diameter ranged between 42 and 138 μm. The vessels of the falcine venous plexus in the anterior third had a mean diameter of 0.42?±?0.1 mm, in the middle third a mean diameter of 0.87?±?0.17 mm, and in the posterior third, 1.38?±?0.21 mm.

Conclusion

The falcine venous plexus is a network of venous channels that exists within the connective tissue of the falx; the sizes and patterns of communication of these structures showed regional differences. Neurosurgeons should be aware of the regional differences when making an incision or puncturing the falx during a surgical approach.     

Microsurgical anatomy of the superficial veins of the cerebrum

The microsurgical anatomy of the superficial cortical veins was examined in 20 cerebral hemispheres. The superficial cortical veins are divided into three groups based on whether they drain the lateral, medial, or inferior surface of the hemisphere. The veins on the three surfaces are further subdivided on the basis of the lobe and cortical area that they drain. The superficial cerebral veins collect into four groups of bridging veins: a superior sagittal group, which drains into the superior sagittal sinus; a sphenoidal group, which drains into the sphenoparietal and cavernous sinuses on the inner surface of the sphenoid bone; a tentorial group, which converges on the sinuses in the tentorium; and a falcine group, which empties into the inferior sagittal or straight sinus or their tributaries. The superior sagittal group drains the superior part of the medial and lateral surfaces of the frontal, parietal, and occipital lobes and the anterior part of the basal surface of the frontal lobe. The sphenoidal group drains the parts of the frontal, temporal, and parietal lobes adjoining the sylvian fissure. The tentorial group drains the lateral surface of the temporal lobe and the basal surface of the temporal and occipital lobes. The falcine group drains an area that includes the cingulate and parahippocampal gyri and approximates the cortical parts of the limbic lobe of the brain. The relationship of these veins to the venous lacunae was also examined.     

Persistent falcine sinus associated with obstruction of the superior sagittal sinus caused by meningioma--case report

A 72-year-old woman presented with meningothelial meningioma causing obstruction of the superior sagittal sinus (SSS). Magnetic resonance imaging demonstrated the lesion in the left occipital parasagittal region and a linear vascular structure in the posterior falx extending from the vein of Galen to the SSS. Cerebral angiography demonstrated obstruction of the posterior portion of the SSS and venous flow from the bilateral occipital lobes draining into the falcine sinus and then into the vein of Galen. The tumor was subtotally removed with preservation of the falcine sinus and bridging veins draining into the sinus. The falcine sinus is usually obliterated after birth, but may persist into adulthood and be involved in unusual draining patterns.     

Anatomic variations of venous sinuses in the region of the torcular Herophili

In this study of 110 cranial cavities from adult cadavers, the superior sagittal sinus was found to divide into two channels. In most cases, the division was associated with a dural partition. Essentially, the variations as observed in this study could be grouped into three types: Type 1 includes those specimens in which the sagittal sinus drains into one lateral sinus and the straight sinus into the other, with no connection between the two. Type 2 includes those specimens in which the superior sagittal sinuses and the straight sinus fork, and the forks from both sinuses join to form the lateral sinuses. Type 3 includes those specimens in which a confluence of sinuses exists, varying from a common pool to merely a potential confluence, depending upon the presence of pads, incomplete partitions, and complete partitions of dura mater. Rare findings previously not reported consist of double straight sinuses draining into one transverse sinus; the superior sagittal sinus dividing into three channels with two transverse sinuses on one side; a transverse sinus originating from a tentorial vein; and drainage of a tentorial vein into the confluence of sinuses.     

MSCT诊断成人永存镰状窦6例及文献回顾

目的分析成人永存镰状窦的多排螺旋CT表现,提高对大脑深静脉发育异常的进一步认识。方法选取6例经CTA诊断为永存镰状窦的成人患者,采用MSCT重组技术对其静脉成像进行分析。结果 6例患者均因临床疑诊颅内动脉病变而接受CTA检查。静脉期见大脑大静脉或直窦前部与上矢状窦后2/3相连的条带状血管样结构,未合并其他动静脉异常。结论成人永存镰状窦可不合并其他先天性静脉窦发育异常及阻塞,多排螺旋CTA是其无创、有效的检查方法。     

Results of attempted radical tumor removal and venous repair in 100 consecutive meningiomas involving the major dural sinuses

OBJECT: Radical removal of meningiomas involving the major dural sinuses remains controversial. In particular, whether the fragment invading the sinus must be resected and whether the venous system must be reconstructed continue to be issues of debate. In this paper the authors studied the effects, in terms of tumor recurrence rate as well as morbidity and mortality rates, of complete lesion removal including the invaded portion of the sinus and the consequences of restoring or not restoring the venous circulation. METHODS: The study consisted of 100 consecutive patients who had undergone surgery for meningiomas originating at the superior sagittal sinus in 92, the transverse sinus in five, and the confluence of sinuses in three. A simplified classification scheme based on the degree of sinus involvement was applied: Type I, lesion attachment to the outer surface of the sinus wall; Type II, tumor fragment inside the lateral recess; Type III, invasion of the ipsilateral wall; Type IV, invasion of the lateral wall and roof; and Types V and VI, complete sinus occlusion with or without one wall free, respectively. Lesions with Type I invasion were treated by peeling the outer layer of the sinus wall. In cases of sinus invasion Types II to VI, two strategies were used: a nonreconstructive (coagulation of the residual fragment or global resection) and a reconstructive one (suture, patch, or bypass). Gross-total tumor removal was achieved in 93% of cases, and sinus reconstruction was attempted in 45 (65%) of the 69 cases with wall and lumen invasion. The recurrence rate in the study overall was 4%, with a follow-up period from 3 to 23 years (mean 8 years). The mortality rate was 3%, all cases due to brain swelling after en bloc resection of a Type VI meningioma without venous restoration. Eight patients--seven of whom harbored a lesion in the middle third portion of the superior sagittal sinus--had permanent neurological aggravation, likely due to local venous infarction. Six of these patients had not undergone a venous repair procedure. CONCLUSIONS: The relatively low recurrence rate in the present study (4%) favors attempts at complete tumor removal, including the portion invading the sinus. The subgroup of patients without venous reconstruction displayed statistically significant clinical deterioration after surgery compared with the other subgroups (p = 0.02). According to this result, venous flow restoration seems justified when not too risky.     

Anatomical features of the straight sinus and its tributaries.

The authors report a variety of arrangements of the venous channels comprising the straight sinus (sinus rectus) and its connections during a continuing study of the cerebral sinuses and their tributaries. In approximately 85% of 131 specimens of dura mater with enclosed venous sinuses derived from fresh cadavers, the straight sinus was represented by a single midline tentorial channel whereas in the remaining 15%, segments of it were doubled and in a few, tripled. In addition to these aberrations in the development of the main trunk of this sinus, the venous patterns at the junctions of the inferior sagittal sinus, vein of Galen and straight sinus showed comparable developmental inconstancies. Also in no specimens were the patterns of venous channels in the leaves of the tentorium cerebelli alike. The course, size, and connections of all the tributaries of the straight sinus have been studied and consideration given to their potentials as collateral pathways in the event either the vein of Galen or the straight sinus itself were occluded.     

连头婴显微分离手术中静脉窦的处理及重建

目的 报道连头婴分离手术中有关静脉窦处理及重建方法与临床效果。方法 采用显微手术分离连头婴共用的矢状窦，窦汇，横窦及直窦，用转流管分别作右婴的矢状窦，直窦与颈内静脉转流术，以及应用人造血管移植进行重建，在手术中确保左婴有完整的矢状窦，窦汇及横窦。结果 左婴术后功能恢复正常，右婴术后22h死于肾衰竭，高钾血症。结论 应用显微外科手术进行静脉窦转流和重建是连头婴分离手术成功的关键技术之一。     

Lateral posterior fossa venous sinus relationships to surface landmarks

BACKGROUND: Knowing the location of the venous sinuses in the combined lateral posterior fossa and lateral cranial base approach is important to prevent their inadvertent injury. The identification of surface landmarks related to these structures is useful in planning such surgical approaches. METHODS: Twelve injected adult cadaver specimens and 10 dried skulls were used to study the relationship of the venous sinuses to various surface anatomic structures. RESULTS: The asterion was not clearly seen in 60% of the studied cadaver sides. The asterion was always clearly seen in the dry skull preparations. The upper margin of the superior nuchal line was found to range from 1.5 mm to 14 mm inferior to the lower margin of the lateral transverse sinus. In 85% of our specimens, the mastoid groove was found to completely overlie the sigmoid sinus. CONCLUSIONS: The asterion was found to be variable in its anatomic relations to other identifiable structures. This variability in relation to other posterior fossa bony landmarks limits its overall usefulness as a consistently stable marker for intracranial structures. The first and most superolateral burr hole for lateral posterior fossa procedures can be safely placed 1 cm below the superior nuchal line and 1 cm medial to the top of the mastoid groove. A burr hole in this location will avoid the transverse and sigmoid sinuses, as well as the transverse-sigmoid junction, yet will be high enough and lateral enough to provide easy exposure of these venous sinuses for all lateral posterior fossa procedures.