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ORIGINAL ARTICLE
Year : 2017  |  Volume : 65  |  Issue : 4  |  Page : 794--800

Microsurgical anatomy of the superior sagittal sinus and draining veins

Mariano Anto Bruno-Mascarenhas, Vengalathur G Ramesh, Sundar Venkatraman, Jolarpettai V Mahendran, S Sundaram 
 Institute of Neurosurgery, Madras Institute of Neurology, Madras Medical College and Rajiv Gandhi Government General Hospital, Chennai, Tamil Nadu, India

Correspondence Address:
Mariano Anto Bruno-Mascarenhas
Department of Neurosurgery, Centre for Advanced Brain and Spine Surgery, Tamil Nadu Government Multi Super Specialty Hospital, Omandurar Government Estate, Chennai - 600 002, Tamil Nadu
India

Abstract

Background: The superior sagittal sinus and the draining cerebral veins are often encountered during the surgery for parasagittal and falx meningiomas and during the interhemisperic transcallosal approaches. A knowledge about the variations from the normally described anatomy helps in anticipating and avoiding problems related to these structures during surgery. Aim: The normal variations in the disposition of the superior sagittal sinus and the number and direction of the draining veins in the Indian population have been studied. Settings and Design: This is an anatomical study in the fresh cadavers. Materials and Methods: Sixty fresh cadavers were examined in the autopsy theatre of the Forensic Medicine Department of the Hospital between March 2011 and February 2013. Statistical Analysis Used: Epi-Info, MS-Excel, and the Statistical Package for the Social Sciences (SPSS) were used for data analysis. Results: The position of the superior sagittal sinus was variable and was up to within 1cm on either side of the sagittal suture. The origin of the superior sagittal sinus varied from the level of foramen caecum to a little posterior from the foramen caecum. The total length of the superior sagittal sagitttal sinus varied from 321 mm to 357 mm (average length 338.77mm); vertical compartments of the sinus were found in three-fourth of the cases studied. Tributaries were found in the herringbone pattern and varied from 13 to 19 on the right and 14 to 19 on the left. The Rolandic vein was the largest draining vein in most of the cases. The superior sagittal sinus drained predominantly to the right transverse sinus in three-fourth of the cases studied. The position of the torcula was variable; often towards the right side and at a higher level. The central sulcus was 49.93 mm posterior to the coronal suture and 130.78 mm anterior to the lambdoid suture. Conclusions: This is the first study of its kind in Indian population studying the anatomical variations in the anatomy of the superior sagittal sinus that may have a significant bearing on the neurosurgical approaches adopted.



How to cite this article:
Bruno-Mascarenhas MA, Ramesh VG, Venkatraman S, Mahendran JV, Sundaram S. Microsurgical anatomy of the superior sagittal sinus and draining veins.Neurol India 2017;65:794-800


How to cite this URL:
Bruno-Mascarenhas MA, Ramesh VG, Venkatraman S, Mahendran JV, Sundaram S. Microsurgical anatomy of the superior sagittal sinus and draining veins. Neurol India [serial online] 2017 [cited 2021 Feb 28 ];65:794-800
Available from: https://www.neurologyindia.com/text.asp?2017/65/4/794/209535


Full Text



It is common knowledge that, very much like finger-prints, no two brains are alike. There are a multitude of variations. The patterns of gyri and sulci vary from person to person and the vasculature patterns also vary a lot.

The superior sagittal sinus is an important component of the venous system of the brain. There are numerous anatomical and structural variations in the superior sagittal sinus and the draining veins, which are of clinical and neurosurgical significance. It is imperative for the surgeon to understand the normal course and variations of the sinus and the draining veins, for a proper preoperative planning of the surgical procedure as well as for the peroperative maneuvers that need to be adopted. A thorough understanding and meticulous avoidance of the veins and tributaries may result in a good functional outcome; whereas, an inadvertent injury to any of the veins can lead to venous thrombosis with devastating results.

This is especially important in the surgical management of parasagittal and falxine meningiomas as well as the use of the transcallosal approach for other conditions. The anatomy of the veins and their variations are an integral part of the preoperative planning for the above-mentioned surgeries.

Various authors have studied the superior sagittal sinus, veins of the brain, and their variations, in cadavers as well as radiologically.[1],[2],[3],[4],[5],[6],[7] A cadaveric study involving a larger number of specimens among the Indian population has not been done till date. This study was conducted to improve our knowledge of the microsurgical anatomy of the superior sagittal sinus to enable a better planning and a more focused surgery. This study was based on the dissection of fresh cadavers.

 Materials and Methods



The study was conducted by the dissection of fresh cadavers of both the genders, examined in the autopsy theatre of the Institute of Forensic Medicine, Madras Medical College and Government General Hospital, Chennai between March 2011 and February 2013. The approval of Institutional Ethics Committee was obtained on 17.03.2011 vide No 09032011.

Inclusion criteria

The inclusion criterion included cadavers on whom postmortem examination was being done for medicolegal purposes.

Exclusion criteria

Those subjects who had died due to trauma and those in whom craniotomy had already been done were excluded to avoid a bias in values due to the anatomical distortion that may have been present in these situations.

Dissection method

The dissection and observations performed by the investigators were carried out during routine medicolegal postmortem examinations done by the Professors/Medical Officers of the Institute of Forensic Medicine, Madras Medical College and Rajiv Gandhi Government General Hospital. Dissection of the area under interest was carried out under 4× magnification using a Carl Zeiss magnifying loupe. The equipment used were chisel and mallet, toothed forceps, non-toothed forceps, scissors, number 11 blade knife, curved mosquito artery forceps, straight mosquito artery forceps, and silk sutures. A Vernier caliper with an accuracy of 0.1 mm was used for conducting the measurements. A 16 megapixel digital camera was used for taking the photographs. The scalp was incised from ear to ear, and the two flaps were retracted anteriorly and posteriorly, respectively. In order to mark the location of the coronal suture on the dura, a needle was inserted, mostly with force and sometimes by twisting at the bregma (the junction of the coronal and sagittal sutures). Another needle was inserted at the lambda (the junction of sagittal and lambdoid sutures) to mark the location of the lambdoid suture in the dura. The skull was opened by chiseling around and removing the calvarium. At this moment, the impact of the needles over the dura/sinus was noted. The sites of impact of the needles were marked for further reference. If the dura was very adherent to the skull and got torn in the process, thereby avulsing the sinus along with the bridging veins from the cortex, further measurements were not taken and the specimens were not taken into consideration. The dura was opened first on the right and then on the left side in a C-shaped manner with the base towards the superior sagittal sinus and 3 cm lateral from the sagittal sinus, and other measurements were made. The veins were then studied. The superior sagittal sinus was then opened at the level of the coronal suture and also at the level of lambdoid suture and measurements taken [Figure 1] and [Figure 2]. The torcula was then dissected and the mode of termination of the superior sgittal sinus and the transverse sinuses were noted [Figure 3] and [Figure 4]. Further examinations of the brain and other organs, as part of the routine postmortem examination, were carried out. Care was taken to ensure that there was no hindrance to the routine procedures of the Department of Forensic Medicine and also that there was no time delay in completion of the postmortem examination.{Figure 1}{Figure 2}{Figure 3}{Figure 4}

Statistical analysis

Tabulations, graphs, and charts were analyzed with MS-Excel, the Statistical Package for the Social Sciences (SPSS), and Epi-Info.

Status of the superior sagittal sinus

The position of the superior sagittal sinus from the coronal suture to the lambdoid suture was noted. The sagittal suture was taken as the reference point, and if the sinus was found directly underneath the suture, it was recorded as zero. If the sinus was towards the left of the sagittal suture, it is mentioned as a negative value, and if it was towards the right, it was mentioned as a positive value. The recordings were mentioned in units of millimeters.

Origin of the superior sagittal sinus

The origin of the superior sagittal sinus was a point of study. It was ascertained whether the sinus originated at the foramen caecum or posterior to the foramen caecum. If the sinus originated from the foramen caecum itself, it was noted as zero, and if it was posterior to the foramen caecum, the distance of origin of the superior sagittal sinus from the foramen caecum was measured in millimeters.

Length of the superior sagittal sinus

The length of the sinus was measured from its origin (as noted above) to the site of termination. This was measured using a long silk thread. One end of the thread was placed at the site of origin. The position of the coronal suture and lambdoid suture were noted on the thread. The site of termination was also noted on the thread. The length of the silk thread was then measured with a Vernier caliper and the measurements were noted according to the following landmarks: a. Anterior one-third of the sinus was regarded as the distance from the glabella to the coronal suture; middle one-third was regarded as the distance from the coronal suture to the lambdoid suture; posterior one-third was regarded as the distance from the lambdoid suture to the torcula; and, the total length of the sinus was calculated based on these three values.

Number of tributaries draining into the superior sagittal sinus

The dura was opened first on the right side, and then on the left side, in a C-shaped manner, with the base towards the Sylvian fissure and 3 cm lateral from the sagittal sinus and other measurements were made. The number of tributaries draining from both sides was then noted. It was again grouped into three groups on each side, from the glabella to the coronal suture, from the coronal to the lambdoid suture and from the lambdoid suture to the torcula. The total number of tributaries of the emerging veins from the superior sagittal sinus were also counted.

Mode of arrangement of the veins

The mode of arrangement of the veins and the tributaries were noted. The aim was to document whether the tributaries and veins resembled a herringbone pattern (or dicot root pattern), similar to that of the duct system of pancreas, or whether they resembled a tree trunk pattern.

Relationship of the largest draining vein to the central sulcus

The largest draining vein and its location to the central sulcus was noted. If the vein was in the central sulcus, it was noted as “0.” If it was anterior to the central sulcus, the distance was noted as negative, and if it was posterior to it, the distance was noted as positive. The largest draining vein and its location in relation to the coronal suture and lambdoid suture on each side was also noted.

Relationship of the central sulcus to the coronal suture and the lambdoid suture

The distance of the central sulcus from the coronal suture and lambdoid suture on both sides was noted. This measurement was not directly related to the study. However, this data was of immense clinical significance in locating the motor cortex, and hence, was also studied.

The cross-sectional area of the superior sagittal sinus

The sinus was divided at various levels, i.e., at the origin, at the level of the coronal suture, at the level of the central sulcus, at the level of the lambdoid suture, and at the termination. The height and width of the sinus at these places were measured [Figure 1]. As the sinus was triangular in cross-section, the area was measured using the formula: Area = ½ × width × height.

Compartments of the superior sagittal sinus in its intermediate one-third

This was measured at a later stage of dissection. The sinus was divided at two levels, one at the level of the coronal suture and the next at the level of lambdoid suture. Value 1 was given if there were no compartments in the superior sagittal sinus. Value 2 was given if there was a vertical division of the sinus into the superior and inferior compartments.

Termination of the superior sagittal sinus

At a later stage of dissection, the torcula was opened in a cruciate manner and the mode of termination of the superior sagittal sinus was noted as follows:

Superior sagittal sinus drained only into the right transverse sinus and had no communication with the left transverse sinusSuperior sagittal sinus drained predominantly into the right transverse sinusSuperior sagittal sinus bifurcated into the right and left transverse sinusesSuperior sagittal sinus drained predominantly to the left transverse sinusSuperior sagittal sinus drained only into the left transverse sinus and had no communication with the right transverse sinus.

Location of the torcula in relation to the external occipital protuberance

The location of the torcula in relation to the external occipital protuberance (EOP) was also noted. The position of the torcula was either above the level of the EOP, at the level of the EOP, or below the level of the EOP. Whether the torcula was to the right, at the midline, or to the left of the EOP was also recorded.

 Results



Equal number of male and female cadavers were included in the study. The age varied from 20 to 59 years, with a mean age of 39.22 years [Figure 5]. In this study, we found that there was no side predilection. The sinus was found up to 1 cm on either side of the midline [Figure 6] and [Figure 7]. The lie was from 9 mm to the left to 10 mm to the right. The mode (the position in which sinus was found the maximum number of times) was 5 mm to the left. The median was 1 mm to the right, and the mean was 0.32 mm to the right [Table 1] and [Table 2]. The superior sagittal sinus originated at a variable distance from the foramen caecum, and the distance varied from less than 1 mm to 12 mm. The mean site of origin of the superior sagittal sinus was 6.05 mm posterior to the foramen caecum [Figure 8] and [Figure 9]. The total length of the sinus varied from 321 mm to 357 mm. The mean total length was 338.77 mm, the median was 337.50 mm, and the mode was 334 mm. It was found that the cross-section at the level of the lambdoid suture was always greater than the cross-section at the level of the coronal suture, and that the flow was always towards the posterior aspect in all the 60 cases.{Figure 5}{Figure 6}{Figure 7}{Table 1}{Table 2}{Figure 8}{Figure 9}

In our study, we found that there was vertical division of the sinus into the superior and inferior compartments in 44 cases (73.3%). The total number of tributaries on the right side varied from 13 to 19, whereas on the left side, it varied from 14 to 19. All cadavers studied had a herringbone pattern (or dicot root pattern) of distribution of venous tributaries of the superior sagittal sinus, similar to that of the duct system of pancreas. On both the sides, the commonest location for the largest draining vein was at the central sulcus. The largest draining vein was found at an average distance of 53.83 mm posterior to the coronal suture and 126.83 mm anterior to the lambdoid suture on the right side, and 54.27 mm posterior to the coronal suture and 126.4 mm anterior to the lambdoid suture on the left side. In 44 cases (73.3%), the sinus drained predominantly to the right transverse sinus, whereas in 4 cases (6.7%), it drained only into the right transverse sinus. In 5 cases (8.3%), the sinus bifurcated into the right and left transverse sinuses [Table 3]. In 3 cases (5.0%), the sinus drained predominantly to the left transverse sinus. In 4 cases (6.7%), the sinus drained only into the left transverse sinus [Figure 4]. The position of the torcula was not exactly at the level of EOP. It was variable, and more towards the right and at a higher level in most cases. The central sulcus was found at an average distance of 49.93 mm posterior to the coronal suture and 130.78 mm anterior to the lambdoid suture on the right side, and 49.93 mm posterior to the coronal suture and 130.78 mm anterior to the lambdoid suture on the left side [Table 4].{Table 3}{Table 4}

 Discussion



A knowledge regarding the normal variations in the anatomy of the superior sagittal sinus helps in planning surgery in this region and in avoiding injury to the veins and the sinus during surgery. This study was undertaken to study the variations in the origin, lie and termination of the superior sagittal sinus, the drainage pattern of the draining veins and cross-sectional anatomy of the superior sagittal sinus. O'Connell (1934) has done pioneering work on the anatomy of superior sagittal sinus and the patterns of distribution of the draining veins.[1] Several other authors too have studied these aspects in detail by anatomical dissections as well as by angiographic studies.[2],[3],[4],[5],[6],[7] We have endeavored to study these aspects of anatomy in the Indian population and have tried to compare our findings with that of the other authors who have published similar studies.

Origin of the superior sagittal sinus – distance from foramen caecum

In our study, we found that the superior sagittal sinus originated at a variable distance from the foramen caecum, and the distance varied from less than 1 mm to 12 mm. The mean site of origin of the superior sagittal sinus was 6.05 mm posterior to the foramen caecum. This is in conformity with other published studies of Kaplan et al.,[8] Krayenbühl et al.,[9] and Hacker et al.[2]

Position of the superior sagittal sinus

Though it is a common knowledge that the superior sagittal sinus lies just below the sagittal suture, i.e., in the midline, this is not always true. In this study, the superior sagittal sinus was found to lie anywhere within about 1 cm on either side, without any predilection for a particular side. Samadian et al.,[6] and Tubbs et al.,[10] have found a right sided predilection in their study. Hence, one has to observe caution while making a burr hole or a bony cut within 1 cm of the sagittal suture.

Length of the superior sagittal sinus

In this series, the total length of the sinus varied from 321 mm to 357 mm. The mean total length was 338.77 mm, the median was 337.50 mm, and the mode was 334 mm. This is in conformity with the other published studies.[1],[2],[3],[4],[5],[6],[7]

Area of cross-section of the superior sagittal sinus

It was found that the cross-sectionl area at the level of the lambdoid suture was always greater than that at the level of the coronal suture, and that the flow was always towards the posterior aspect in all the 60 cases. In the study published by Andrews et al., who have examined the microsurgical anatomy of the superior sagittal sinus in 10 fresh specimens, it has been found that the superior sagittal sinus had a mean width of 4.3 mm and a depth of 3.6 mm in the mid anterior frontal region, which enlarged to a mean width of 9.9 mm and a depth of 6.8 mm in the midoccipital region [Table 2].[3]

Compartments in intermediate one-third of the superior sagittal sinus

In the present study, the transverse septation dividing the superior sagittal sinus into the superior and inferior compartments was found in 73.3% of the cases. Though this has been observed by the other authors also, the exact incidence has not been recorded [Figure 2].

Number of tributaries draining into the superior sagittal sinus

In the present study, the number of tributaries/draining veins varied from 13 to 19 on the right side and 14 to 19 on the left side, which is almost equal on both the sides. Andrews et al., found on an average, 6.5 veins draining the surface of each hemisphere in the anterior frontal region, 3 veins draining each posterior frontal region, 4 veins draining each parietal region, and 1 vein draining each occipital region.[3] Brockmann et al., showed most of the branching veins emptying into the superior sagittal sinus close by (±3 cm) and distal to the coronary suture (74% on computed tomographic (CT) venograms and 62% in cadavers).[7]

Arrangement of the draining veins

The arrangement of the draining veins in this study was similar to the herringbone pattern (or dicot root pattern), resembling the duct system of pancreas. O'Connell observed that the anterior-most draining veins entered the superior sagittal sinus almost at right angles or in a slightly posterior direction, whereas the remaining veins turned anteriorly and entered the sinus obliquely, which was more marked in the posterior veins [1]. Bonnal also noted similar findings.[11] This has been our observation too. Han et al., found that (1) the way a draining (bridging) vein entered the superior sagittal sinus varied in three dimensions and hence the point of entry was difficult to visualize on the digital subtraction angiographic images, (2) the pattern of the dural entrance of the bridging veins into the superior sagittal sinus was almost constant and there was consistently the presence of a segment of the superior sagittal sinus around the area of coronal suture, and, (3) almost 97% of the bridging veins entered the superior sagittal sinus at an angle against the direction of blood flow.[5]

The largest draining vein was the superior anastomotic vein (vein of Trolard) and this corresponded to the Rolandic vein (vein of the central sulcus) in most of the specimens in the present study. Rhoton in 2002 found that the vein of Trolard was precentral, central or post central in location in 75% of the specimens studied.[4] The largest draining vein (vein of Trolard) was found at an average of 53.83 mm posterior to the coronal suture and 126.83 mm anterior to the lambdoid suture on the right side and 54.27 mm posterior to the coronal suture and 126.4 mm anterior to the lambdoid suture on the left side in the present study.

Termination of the superior sagittal sinus

In 73.3% (44) of the specimens, the superior sagittal sinus drained predominantly into the right transverse sinus. Widraja et al.,[12] in their study of magnetic resonance venography in fifty children found a predominant drainage of the superior sagittal sinus into the right transverse sinus in 27 cases, and drainage into the left transverse sinus in 18 cases [Table 3].

Location of the torcula in relation to the EOP

Contrary to the common understanding, the torcula was not exactly underneath the EOP, but slightly above and to the right in most of the specimens in the present study. This is also in agreement with the findings of Ebraheim et al.,[13] and Tubbs et al.[14]

Relationship of the central sulcus to the coronal and lambdoid sutures

The position of the central sulcus to the coronal and lambdoid sutures was also studied as a corollary to the main study as it would be of interest to the neurosurgeons. The central sulcus was found at an average of 49.93 mm (about 5 cm) posterior to the coronal suture and 130.78 mm (about 13 cm) anterior to the lambdoid suture. Others have shown a slight variation in these measurements. Sarmento et al., found the average distance of the central sulcus from the coronal suture to be about 5.9 cm;[15] Gusmao et al., (2001, 2003) reported this to be about 4.5 cm;[16],[17] Ribas et al., (2006) reported this distance to be 5 cm, similar to that seen in the present study [Table 4].[18] Rivet et al., found that the mean distance from the coronal suture to the motor cortex and central sulcus were 32.8 ± 6 mm and 50.3 ± 4.7 mm respectively.[19] In actual practice, the presence of space occupying lesions or brain edema may alter the position of the sulci in relation to the bony landmarks.

The present study has included only adult brain specimens. We could not use an operating microscope and dye injections, as this study was done as a part of routine post-mortem examination. We used a magnifying loupe instead and could get the required information. This is the first study of its kind in the Indian population and has shown more or less similar findings to those done in other population groups. The important conclusions from this study are that the lie of the superior sagittal sinus can vary up to 1 cm on either side of the sagittal suture, the torcula is usually slightly superior and to the right of the EOP, and there is division of the superior sagittal sinus into the superior and inferior compartments by a transverse septation. These findings have immense implications on the surgical interventions in this region.[20],[21]

Acknowledgments

We thank the Faculty and Staff of the Institute of Forensic Medicine, Madras Medical College and Government General Hospital, Chennai, for their help in carrying out this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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