Cerebral vein disorders and postoperative brain damage associated with the pterional approach in aneurysm surgery

[Venous factor in surgical management of skull base meningiomas]

Skull base venous system is a variable anatomical formation in both health and pathology. Damage to venous structures during surgical treatment of craniobasal meningiomas can lead to formidable postoperative complications, such as hemorrhagic infarctions, cerebral edema and persistent neurological deficit. Despite the improvement of microsurgical techniques, methods of morphological and functional angiography, as well as modeling the mechanisms of compensation for venous hemodynamic disorders, the problem of preventing postoperative venous complications remains relevant.

OBJECTIVE

To analyze available literature data on the role of venous system in surgery for skull base meningiomas and prevention of venous outflow disorders.

MATERIAL AND METHODS

The PRISMA algorithm was used to search for publications on venous complications, venous outflow compensation and prevention of vein damage in skull base meningiomas. The PubMed and Google Scholar databases were reviewed.

RESULTS

Thirty-six manuscripts were assessed. Statistics of venous complications in neurosurgery, venous system reorganization in craniobasal meningiomas, modern methods of X-ray diagnosis and minimization of venous complications during tumor resection are described.

CONCLUSION

Peculiarities of venous hemodynamics in skull base meningiomas are important in planning surgical treatment, as evidenced by many studies in recent years. Improvement of microsurgical techniques and highly informative methods of X-ray diagnosis reduce the likelihood of venous complications in neurosurgery. However, persistent risk of vein damage during resection of craniobasal meningiomas necessitates further improvement of diagnostic and treatment algorithms.

Training in Sylvian Arachnoid Dissection: The Art of Using Kamiyama Scissors and a Simple Novel Model for Practice Sylvian Arachnoid Dissection Using Cotton Fiber with Brain Model

Background  Transsylvian approach is one of the main approaches for a variety of vascular, tumor, and skull-base lesions. Sylvian fissure harbors a lot of critical structures including the middle cerebral artery and many venous structures. If not done properly, the transsylvian approach could cause several complications. Up to now, there is no simple training model for practicing Sylvian fissure dissection. In this article, we describe the technique of using microscissors for the sharp dissection of arachnoid trabeculae. We also propose a new model for practicing Sylvian arachnoid dissection using a three-dimensional (3D) brain model with cotton fiber. Materials and Method  We inserted cotton fiber into the Sylvian fissure of the brain model (aneurysm box from UpsurgeOn) and covered the Sylvian fissure with a cotton sheet, then sprayed the water over it. We dissected this model under a microscope by using Kamiyama scissors in the right hand and suction in the left hand. Result  Under the microscope, our model appears comparable with the real Sylvian fissure. We can use this model for practicing arachnoid dissection with Kamiyama scissors. Conclusion  The arachnoid dissection model by using a 3D brain model with cotton fiber is a simplified and novel approach for practicing the Sylvian fissure dissection.

[Venous cerebral complications after microsurgery for complex aneurysms of the middle cerebral arteries]

Microsurgeries are common for complex aneurysms of the middle cerebral artery (MCA).

OBJECTIVE

To evaluate the incidence and types of venous cerebral disorders after microsurgeries for complex MCA aneurysms.

MATERIAL AND METHODS

A retrospective study included 285 patients with complex MCA aneurysms between 2009 and 2020. Pterional craniotomy and transsylvian approach were used in all cases. Aneurysm clipping was performed in 230 cases, revascularization - 27, trapping without bypass - 17, reinforcement - in 11 cases. Computed tomography within 1-3 days after surgery recognized venous cerebral disorders as heterogeneous foci of abnormal brain density with unclear boundaries. These foci were crescent-shaped as a rule and located in deep and basal parts of the frontal lobes.

RESULTS

Venous abnormalities occurred in 76 (26.7%) patients. Thirty-five (12.3%) patients had mild venous edema of the frontal lobe alone. In 35 (12.3%) patients, we found moderate disorders with focus in the frontal lobe and compression of anterior horn of the left lateral ventricle with or without hemorrhagic imbibition. Severe disorders occurred in 6 (2.1%) patients with lesion extending to the frontal, insular and temporal lobes. These lesions were accompanied by hemorrhagic imbibition, and lateral dislocation exceeded 5 mm.

CONCLUSION

Careful dissection of veins in Sylvian fissure with preservation of bridging veins is likely to reduce the risk of this complication. Cauterization of a large vein in Sylvian fissure should be followed by careful hemostasis within frontal or temporal cortex. Bleeding and cortical tension can indicate intracerebral hematoma whose likelihood is higher in patients with venous cerebral disorders.

A Novel Surgical Classification of the Sylvian Fissure and Its Implications on the Clinical and Radiological Outcomes of Patients Undergoing Clipping for Unruptured Middle Cerebral Artery Aneurysms

BACKGROUND

The main access route for middle cerebral artery (MCA) aneurysms is the transsylvian approach. Although Sylvian fissure (SF) variations have been assessed, none have examined how this affects MCA aneurysm surgery. The objective of this study is to investigate how SF variants affect clinical and radiological outcomes for surgically-treated unruptured MCA aneurysms.

METHODS

This retrospective study examined consecutive unruptured MCA aneurysms in 101 patients undergoing SF dissection and aneurysm clipping. SF anatomical variants were categorized using a novel functional anatomical classification: Type I: Wide straight, Type II: Wide with frontal and/or temporal opercula herniation, Type III: Narrow straight, and Type IV: Narrow with frontal and/or temporal opercula herniation. The relationships between SF variants and postoperative edema, ischemia, hemorrhage, vasospasm, and Glasgow Outcome Scale (GOS) were analyzed.

RESULTS

Study included 101 patients (53.5% women), 60.9 ± 9.4 (range 24-78) years. SF types were 29.7% Type I, 19.8% Type II, 35.6% Type III, and 14.9% Type IV. The SF type with the highest proportion of females was Type IV (n = 11, 73.3%), while it was Type III for males (n = 23, 63.9%) (P = 0.03). There were significant differences between SF types, ischemia, and edema (P < 0.001, P = 0.008, respectively). Although narrow SF types had poorer GOS scores (P = 0.055), there were no significant differences between SF types and GOS, postoperative hemorrhage, vasospasm, or hospital stay.

CONCLUSIONS

Sylvian fissure variants may impact intraoperative complications during aneurysm surgery. Thus, presurgical determination of SF variants can predict surgical difficulties, thereby potentially reducing morbidity for patients with MCA aneurysms and other pathologies requiring SF dissection.

Skull Base Meningiomas

Skull base meningiomas are among the most challenging meningiomas to treat clinically due to their deep location, involvement or encasement of adjacent essential neurovascular structures (such as key arteries, cranial nerves, veins, and venous sinuses), and their often-large size prior to diagnosis. Although multimodal treatment strategies continue to evolve with advances in stereotactic and fractionated radiotherapy, surgical resection remains the mainstay of treatment for these tumors. Resection of these tumors however is challenging from a technical standpoint, and requires expertise in several skull-base surgical approaches that rely on adequate bony removal, minimization of brain retraction, and respect for nearby neurovascular structures. These skull base meningiomas originate from a variety of different structures including, but are not limited to: the clinoid processes, tuberculum sellae, dorsum sellae, sphenoid wing, petrous/petroclival area, falcotentorial region, cerebellopontine angle, and foramen magnum. In this chapter, we will cover the common anatomical areas in the skull base from which these tumors arise, and the specific or optimal surgical approaches and other treatment modalities for meningiomas in these such locations.

Morphological Analysis of the Sylvian Fissure Stem to Guide a Safe Trans-sylvian Fissure Approach

The sylvian fissure stem and its deep cisternal part (SDCP) consist mainly of the orbital gyrus (OG) and anterior medial portion of the temporal lobe. SDCP's adhesion has been found to make a trans-sylvian approach difficult due to the various patterns of adhesion. Thus, in this study, we aim to clarify the morphological features of the SDCP, and to guide a safe trans-sylvian approach. We retrospectively classified the morphology of the SDCP in 81 patients into 3 types (tight, moderate, loose type) according to the degree of adhesion of the arachnoid membrane and analyzed the morphological features of the OG and the temporal lobe using intraoperative video images. In addition, we have retrospectively measured each width of the SDCP's subarachnoid space at the three points (Point A, lateral superior portion; Point B, downward portion; Point C, medial inferior portion of SDCP) and analyzed their relationship to the degree of adhesion using the preoperative coronal three-dimensional computed tomography angiography (3D-CTA) images of 44 patients. As per the results, SDCP's adhesions were determined to be significantly tighter in cases with large OG and young cases. The temporal lobe had four surfaces (posterior, middle, anterior, and medial) that adhered to the OG in various patterns. The tighter the adhesion between the OG and each of the three distal surfaces of the temporal lobe, the narrower the width of the subarachnoid space at each point (A, B, C). Understanding of the morphological features of the SDCP, and estimating its adhesion preoperatively are useful in developing a surgical strategy and obtaining correct intraoperative orientation in the trans-sylvian approach.

Dissection of the Sylvian Fissure in the Trans-sylvian Approach Based on the Morphological Classification of the Superficial Middle Cerebral Vein

The superficial middle cerebral vein (SMCV) is one of the main factors that can impede a wide opening of the sylvian fissure. To reveal the most efficient SMCV dissection for a wide operative field while preserving the veins in the trans-sylvian approach, we retrospectively investigated the SMCVs through intraoperative video images. We characterized the SMCV as composed of the frontosylvian trunk (FST; receiving frontosylvian veins [FSVs] or parietosylvian veins [PSVs]), the temporosylvian trunk (TST; receiving temporosylvian veins [TSVs]), and the superficial middle cerebral common trunk (SMCCT; receiving both FSV/PSV and TSV), and classified the SMCVs of the 116 patients into 5 types based on the morphological classification of the SMCV. Type A SMCV (60.4%) with the SMCCT anastomosed to the frontal side had few bridging veins (BVs) between the SMCCT and the temporal side during dissection. Type B (7.8%) had the SMCCT with no anastomoses to the frontal side. In Type C (17.2%) consisting of the FST and TST and Type D (12.9%) with a merging of the vein of Trolard and Labbé posteriorly and the SMCVs dividing into the FST and the TST again proximally, there were few BVs between the FST and the TST during dissection. Finally, in Type E (1.7%) showing an undeveloped SMCV, there were no BVs between the frontal and the temporal lobes. Postoperative venous infarction occurred in 2.6%. Morphological classification of the SMCV can inform appropriate dissection line to create a wide operative field while preserving the veins in the trans-sylvian approach.

Giant Middle Cerebral Artery Aneurysms: A 55-Patient Series

BACKGROUND

The treatment of middle cerebral artery (MCA) giant aneurysms (GAs) represents a challenging task.

METHODS

The data for 55 patients treated for MCA GA (≥25 mm) at the N.N. Burdenko NMRCN between 2010 and 2019 were analyZed.

RESULTS

The GAs were located in the M1 segment in 11 (20%) patients, MCA bifurcation in 33 (60%), M2 in 7 (12.7%), and M3 in 4 (7.3%). There were 32 (58.2%) saccular and 23 (41.8%) fusiform GAs. MCA GAs were treated with neck clipping (50.9%), clipping with the artery lumen formation (3.6%), bypass surgeries (34.5%), wrapping (3.6%), and endovascular surgery (7.3%). A worsening of the neurologic state in the perioperative period was observed in 50.9% of patients. The complete closure of GA was achieved in 78.2%. Surgery-related mortality was 1.8%. The long-term outcome was favorable in 76.9% of patients. Surgery-related and disease-related plus treatment failures-related mortality was 9.6%.

CONCLUSIONS

Microsurgical clipping and bypass surgery are the main operative interventions for MCA GA treatment. These operations are technically complex and are followed by a relatively high percentage of complications. The main tasks that require further investigations are the introduction of new precise diagnostic methods for the collateral circulation assessment in the cortical MCA branches, the perfection of the algorithm for the bypass selection, and investigation of the long-term results of the endovascular and combined treatments. It is of major importance to thoroughly observe the patients long-term after the surgery and ensure the possibility for further angiographic studies.

Planning of Endocranial Supratentorial Basal Cistern and Skull Base Approaches Depending on Venous Patterns Using a Topogram

BACKGROUND

Because damage or sacrifice of venous drainage during supratentorial basal cistern and skull base approaches may have severe and harmful consequences, methods to identify preoperatively veins at risk are of paramount importance. Among methods, a codified assessment with a venous topogram is helpful, with practical implications.

METHODS

This technical note describes how to construct an easy-to-use topogram. Three regions of interest are defined as triangles. The anterior triangle corresponds to the anterior frontal veins draining to the superior sagittal sinus at risk during anterior cerebral fossa surgery, the middle triangle corresponds to the anterior sylvian veins draining to the cavernous sinus at risk during pterional approaches, and the inferior triangle corresponds to the inferior cerebral veins draining to the transverse sinus at risk in subtemporal approaches and temporal lobe surgery.

RESULTS

Depending on predominance of the drainage, 4 situations were defined: an anterior, an inferior, and a middle predominance or equilibrium between the 3 triangles. These anatomic features have important practical implications in skull base and basal cistern approaches.

CONCLUSIONS

This is, to our knowledge, the only topogram described in the scientific literature. Any well-defined approach should be adapted to the individual patient according not only to location and type of lesion but also to the venous drainage to be encountered along the way.

Surgical Techniques and Prevention of Complications in the Treatment of Basal Ganglia Hemorrhage Through the Distal Transsylvian Approach

OBJECTIVE

Basal ganglia hemorrhage can damage the internal capsule and lead to high rates of disability and mortality. The distal transsylvian approach is a validated approach in the treatment of basal ganglia hemorrhage. However, this approach is difficult and prone to complications. The present study was performed to investigate the surgical techniques and prevention of complications of basal ganglia hemorrhage through the distal transsylvian approach.

PATIENTS AND METHODS

From January 2015 to January 2018, the authors treated 40 cases of basal ganglia hemorrhage using the distal transsylvian approach. The surgical video recordings and the patients' clinical data were retrospectively analyzed. The authors discussed the surgical techniques and prevention of complications through the distal transsylvian approach.

RESULTS

Thirty-eight cases of basal ganglia hemorrhage were successfully treated through the distal transsylvian approach. The other 2 cases were converted to the transcortical transtemporal approach. In the early cases, complications occurred in 3 stages: sylvian fissure dissection, insula lobectomy, and hematoma removal. In the subsequent cases, the authors implemented appropriate surgical techniques to prevent complications.

CONCLUSION

Basal ganglia hemorrhage can be treated through the distal transsylvian approach, but not in all patients. The distal transsylvian approach is highly technical and more problematic than the transcortical transtemporal approach. Mastering certain operative skills can reduce the surgical complications.

Morphological Pattern and Classification of the Superficial Middle Cerebral Vein by Cadaver Dissections: An Embryological Viewpoint

In this study, we used 45 adult cadaveric cerebral hemispheres to investigate the anatomical classification of the superficial middle cerebral vein (SMCV) based on the number of stems, course, and anastomosis at the distal portion. We classified the SMCVs into five types based on embryological concept. Type A (18 cases, 40.0%) is that the frontosylvian veins (FSVs) merge with the vein of Trolard (VT) and the vein of Labbé (VL) at the distal portion of the sylvian fissure. Type B (5 cases, 11.1%) is that the temporosylvian veins (TSVs) merge with the VT and the VL at the distal portion. Type C (13 cases, 28.9%) is that no vein merge with the VT and the VL at the distal portion. The VT merges with the SMCV from the FSV and the VL merges with the SMCV from the TSV. They course along the sylvian fissure and merge at the proximal portion. In Type D (eight cases: 17.8%), the VT and the VL merge at the distal portion, and the SMCV from the FSV and the SMCV from the TSV join their confluence without merging. Type E (one case, 2.2%) show an undeveloped SMCV. Formation rate of intravenous anastomoses or bridging veins(BVs) at the distal portion between the frontosylvian trunk (FST) and the temporosylvian trunk (TST), between the FST and the temporal lobe, and between the TST and the frontal lobe was very low, because these formation may be difficult to occur during the embryological process in which the SMCV is formed from the telencephalic vein.

Absent Filling of Ipsilateral Superficial Middle Cerebral Vein Is Associated With Poor Outcome After Reperfusion Therapy

BACKGROUND AND PURPOSE

Our aim was to study the effect of drainage of cortical veins, including the superficial middle cerebral vein (SMCV), vein of Trolard, and vein of Labbé on neurological outcomes after reperfusion therapy.

METHODS

Consecutive ischemic stroke patients who underwent pretreatment computed tomographic perfusion and 24-hour computed tomographic perfusion or magnetic resonance perfusion after intravenous thrombolysis were included. We defined "absent filling of ipsilateral cortical vein" (eg, SMCV-) as no contrast filling of the vein across the whole venous phase on 4-dimensional computed tomographic angiography in the ischemic hemisphere.

RESULTS

Of 228 patients, SMCV-, vein of Trolard- and vein of Labbé- were observed in 50 (21.9%), 27 (11.8%), and 32 (14.0%) patients, respectively. Only SMCV- independently predicted poor outcome (3-month modified Rankin Scale score of >2; odds ratio, 2.710; P=0.040). No difference was found in reperfusion rate after treatment between patients with and without SMCV- (P>0.05). In patients achieving major reperfusion (≥80%), there was no difference in 24-hour infarct volume, or rate of poor outcome between patients with and without SMCV- (P>0.05). However, in those without major reperfusion, patients with SMCV- had larger 24-hour infarct volume (P=0.011), higher rate of poor outcome (P=0.012), and death (P=0.032) compared with those with SMCV filling. SMCV- was significantly associated with brain edema at 24 hours (P=0.037), which, in turn, was associated with poor 3-month outcome (P=0.002).

CONCLUSIONS

Lack of SMCV filling contributed to poor outcome after thrombolysis, especially when reperfusion was not achieved. The main deleterious effect of poor venous filling appears related to the development of brain edema.

Quantitative analysis of surgical exposure and surgical freedom to the anterosuperior pons: comparison of pterional transtentorial, orbitozygomatic, and anterior petrosal approaches

Surgical approaches to the pons lump together different areas of the pons, such as the anterosuperior and the anteroinferior pons. These areas are topographically different, and different approaches may be best suited for one or the other area. We evaluated the exposure of the anterosuperior pons using different surgical approaches. We quantify the surgical exposure and surgical freedom to the anterosuperior pons afforded by the pterional transtentorial (PT), the orbitozygomatic with anterior clinoidectomy (OZ), and the anterior petrosal (AP) approaches. Five embalmed cadaver heads were used. The three approaches were executed on each side, for a total of 30 approaches. The area of maximal exposure of the anterosuperior pons was measured with the aid of neuronavigation. We also evaluated the feasible angles of approach in the vertical and horizontal planes. We were able to successfully expose the anterosuperior pons using all the selected approaches. In the PT and OZ approaches, mobilization of the sphenoparietal sinus can prevent over-retraction of the temporal bridging veins, while use of the endoscope can help in preserving the integrity of the fourth nerve while cutting the tentorium. The mean exposure area was largest for the AP and smallest for the PT; the surgical freedom was similar among all the approaches. However, there was no statistically significant difference among all the approaches in the exposure area or in the surgical freedom. There is no significant difference among the three evaluated approaches in exposure of the anterosuperior pons.

Leukocytosis after routine cranial surgery: A potential marker for brain damage in intracranial surgery

Aims and Objectives:

Leukocytosis after intracranial surgery may create concern about possible infection, especially when associated with fever. Knowledge of the expected degree of leukocytosis after surgery would assist in the interpretation of leukocytosis. It was hypothesized that the degree of leukocytosis after intracranial surgery correlated with the extent of brain damage inflicted during the surgery.

Materials and Methods:

In this prospective study conducted over 6 months, consecutive patients undergoing either elective resections of brain tumors (having significant collateral brain damage) or aneurysm clipping (with minimal collateral brain damage) were studied. Total blood leukocyte count was checked daily in the morning for the first five postoperative days in both the groups. The mean of the leukocyte count ratio (postoperative leukocyte count/preoperative leukocyte count) on each day was calculated for each group.

Results:

There were 76 patients, 46 in the test group and 30 controls. Both groups were well matched in age, sex, duration of surgery, and intraoperative fluid balance. The mean leukocyte count ratio on POD1 in the tumor group was significantly higher (1.87) as compared to 1.1 in the aneurysm group (P = 0.001). This difference in the leukocyte count ratio between the groups was maintained on the second and third postoperative days, with decreasing level of significance after the third day.

Conclusions:

This study shows that intraoperative brain injury is associated with leukocytosis in the immediate postoperative period. This can assist in the interpretation of leukocytosis after intracranial surgeries and could be a quantitative marker for brain injury in patients undergoing intracranial surgery.

Mobilization of the sphenoparietal sinus: a simple technique to preserve prominent frontobasal bridging veins during surgical clipping of anterior communicating artery aneurysms: technical case report

BACKGROUND AND IMPORTANCE

Bridging veins arising from the frontal base (frontobasal bridging veins, FBBVs) can pose obstacles when performing clipping of anterior communicating artery (ACoA) aneurysms via the pterional approach. Although FBBVs can in general be sacrificed without critical complications to achieve an adequate retraction of the frontal lobe, neurosurgeons sometimes encounter postoperative venous infarction or contusion of the retracted frontal lobe, which may be accounted for by the damage to the venous drainage system. Thus, preservation of intracranial veins is desirable to prevent postoperative venous complications, especially when they are prominent.

CLINICAL PRESENTATION

A 66-year-old female patient was revealed to have multiple unruptured aneurysms at the ACoA, bilateral middle cerebral arteries, and the left internal carotid artery. In the first stage of the operation, clipping of the right middle cerebral artery and ACoA aneurysms was performed via a right pterional approach. Because the ACoA aneurysm was located at a high position and projecting posteriorly, a transsylvian "lateral" trajectory was preferred to a subfrontal "anterior" trajectory. Intraoperatively, her FBBV was revealed to be so prominent that the sacrifice would be harmful. Thus, we performed posteriorward displacement of the sphenoparietal sinus extradurally, thereby achieving adequate retraction of the frontal lobe intradurally without sacrificing the FBBV. With this simple technique, the ACoA aneurysm was successfully treated.

CONCLUSION

This technique is useful for retracting the frontal lobe sufficiently to enable establishment of an appropriate surgical field for a pterional approach to ACoA aneurysms with prominent FBBVs.

Dural Entrance of the Bridging Vein in the Middle Cranial Fossa: A Novel Classification of the Cerebral Veins for Preoperative Planning

BACKGROUND AND IMPORTANCE:

Understanding of the intracranial venous anatomy is essential for preoperative planning.

OBJECTIVE:

To identify anatomic features of the dural entrance of the bridging veins (BVs) into the dural sinuses in the middle cranial fossa on the cadaver and to correlate such features with those of digital subtraction venogram, computed tomographic venogram, and magnetic resonance venogram.

CLINICAL PRESENTATION:

A total of 30 adult cadavers and 86 patients were examined with anatomic dissection or neuroimages. The number, diameter, and location of the BVs entering the dural sinuses in the middle cranial fossa were recorded and compared between the cadavers and neuroimages. The dural entrances of the BVs were identifiable on neuroimages and distributed mainly at the anteromedial area of the fossa. Morphological features of the dural sinuses and meningeal veins in the fossa indicated that the techniques of lengthening the BV by dissecting it away from the dura mater or cutting a small area of the dura along the sides of the BV may not be applicable for the management of BVs in the anteromedial middle cranial fossa.

CONCLUSION:

Unique anatomic features of the dural entrance of BVs entering the dural sinuses in the cadaver are correlated to those on neuroimages. Identification of the dural entrance of BVs with neuroimaging modalities provides a reliable measure for preoperative planning.

The pterional-transsylvian approach: an analytical study

OBJECTIVE

Splitting of the sylvian fissure (SF) improves exposure with the pterional (PT) approach. Traditionally, the choice of whether or not to split the SF and how far to open it has depended on the neurosurgeon's experience and preference rather than on quantifiable data. We undertook this study to evaluate the effects of progressive splitting of the SF on surgical exposure with the PT approach.

METHODS

A PT craniotomy was performed on nine sides of cadaver heads. Splitting the SF was divided into four steps: 1) dissection of the basal cisterns, 2) dissection of the sphenoidal compartment, 3) dissection of the operculoinsular compartment to the anterior ascendant ramus, and 4) dissection progressing 2.0 cm distal to the anterior ascendant ramus. The degree of the retraction and the relative position of the brain retractors were kept constant. After each step, we used a computerized tracking system to measure the area of surgical exposure of the circle of Willis, the angles of approach to the carotid bifurcation, and the distance between the frontal lobe and skull base.

RESULTS

Exposure of the circle of Willis, angles of approach to the carotid bifurcation, and linear distance between the frontal lobe and skull base all increased significantly as splitting of the SF progressed from Steps 1 to 2 and from Steps 2 to 3. There was no significant difference between Steps 3 and 4.

CONCLUSION

Exposure of the basal cisterns and circle of Willis by the PT approach is optimized when dissection of the SF reaches the anterior ascendant ramus. Further splitting of the SF provides no additional gain.

Role of uncal resection in optimizing transsylvian access to the basilar apex: cadaveric investigation and preliminary clinical experience in eight patients

OBJECTIVE

The pretemporal approach has gained popularity for the treatment of basilar apex aneurysms. However, it requires the sacrifice of anterior temporal bridging veins to allow posterior temporal lobe retraction and, for patients with dominant pretemporal venous drainage, has the attendant risk of venous hypertension, hemorrhagic venous infarction, or seizures postoperatively. Alternatively, we have found that splitting the sylvian fissure, resecting the uncus, and applying posterolateral retraction to the medial temporal lobe provides a similar exposure to the basilar apex while preserving the anterior temporal bridging veins. To evaluate the transsylvian, trans-uncal approach to the basilar apex, we report our initial clinical results using this exposure in eight consecutive patients. A morphometric cadaveric analysis comparing this approach with the pretemporal approach was also performed.

METHODS

For the clinical study, all hospital charts and imaging studies were retrospectively reviewed for patients undergoing the transsylvian, trans-uncal approach for the treatment of an upper basilar trunk aneurysm between July 2000 and July 2002. In the anatomic study, six formalin-fixed cadaver specimens were used. Two sequential exposures of the basilar apex were performed on each specimen side. First, the pretemporal exposure was performed with anteroposterior temporal lobe retraction. Next, after the temporal lobe had been allowed to return to normal anatomic position, the retractor was repositioned on the medial aspect of the temporal lobe superficial to the uncus, and a 10 x 10 x 15-mm volume of uncus was removed. Morphometric measurements were performed for each exposure.

RESULTS

Four basilar bifurcation and four superior cerebellar segment aneurysms in eight consecutive patients were successfully clip-ligated by use of the transsylvian, trans-uncal approach. All patients had temporal bridging veins that were preserved, as documented by angiography and operative reports. No patient developed a venous infarction or new postoperative seizures, with a mean follow-up of 9.75 months (range, 0.5-28 mo). The cadaveric analysis revealed that in addition to providing a similar exposure of the upper basilar complex, the transsylvian, trans-uncal approach provided additional exposure of the ipsilateral posterior cerebral and superior cerebellar arteries compared with the pretemporal approach.

CONCLUSION

When approaching the basilar bifurcation, the transsylvian, trans-uncal approach provides superior exposure of the ipsilateral superior cerebellar and posterior cerebral arteries compared with the pretemporal approach, while preserving the anterior temporal bridging veins. This approach is most valuable in patients with dominant temporal venous drainage or when additional exposure of the ipsilateral posterior cerebral or superior cerebellar arteries is required.

Preoperative evaluation of the venous system for potential interference in the clipping of cerebral aneurysm

BACKGROUND

Variations of the venous system affecting the surgical treatment of cerebral aneurysm were evaluated using three-dimensional computed tomography angiography (3D-CTA) to evaluate the essential aspects of preoperative diagnosis.

METHODS

This study included 50 patients who underwent clipping of cerebral aneurysm through the pterional and trans-sylvan approaches. The 3D-CTA and operative findings were compared to assess the characteristics of cases in which the veins restrict brain retraction, hinder operative manipulations or require sacrifice because of the position in the operative field.

RESULTS

Superficial sylvian veins that restricted brain retraction were identified in 8 cases. The veins entered the cavernous sinus in a relatively high position just below either the sphenoid ridge (superior lateral type) or the anterior clinoid process (superior medial type), and the veins entering at a more medial position were closer to the spatula and tended to be compressed or directly excluded (superior medial type). The inferior medial type did not tend to become tense and so did not restrict brain retraction. The inferior lateral type hardly affected the operative manipulation. The first segment of the basal vein of Rosenthal, the uncal vein entering the cavernous sinus, or the sphenoparietal sinus were located in the operative field in six cases, and affected the manipulation of dissecting arteries, and exposure and clipping of the aneurysm.

CONCLUSIONS

3D-CTA provides essential information for operative planning to protect the venous system during the pterional and trans-sylvian approaches.

Estudio morfométrico mediante técnicas de imagen de la vena de Trolard en su anastomosis al seno longitudinal superior

OBJECTIVE

The main objective of this work is to allow the anatomical localization of the vein of Trolard (VT) or great anastomotic vein, before neurosurgical approaches to the parietal region.

MATERIAL AND METHODS

Thirty four patients were subjected to cerebral angiography. Measurements of different points related to the anatomy of the vein were taken in 41 studies on the lateral projection. A statistical analysis was performed.

CONCLUSIONS

The measures obtained are of practical utility to locate the final portion of the vein of Trolard in its anastomotis to the sagittal superior sinus (SLS) for planning neurosurgical approaches to the parietal region.

Venous Infarction Resulting From Sacrifice of a Bridging Vein During Clipping of a Cerebral Aneurysm: Preoperative Evaluation Using Three-dimensional Computed Tomography Angiography-Case Report-

A 67-year-old woman presented with a ruptured aneurysm of the left internal carotid artery bifurcation. Three-dimensional computed tomography angiography (3D-CTA) demonstrated the first segment of the basal vein of Rosenthal passing in front of the internal carotid artery and the anastomosis with the cavernous sinus, the partially hypoplastic second segment, and the superficial sylvian vein entering the lateral side of the sphenoparietal sinus. Dissection of the sylvian fissure toward the distal direction enabled transfer of the superficial sylvian vein to the temporal side, but the bridging vein had to be sacrificed to secure adequate operating space. Postoperative CT demonstrated hemorrhagic infarction at the left caudate head and surrounding region. Postoperative venous infarction is not an uncommon complication of various approaches. 3D-CTA can provide important information about the venous anatomy indispensable for avoiding postoperative venous infarction.

Operative Anatomy and Classification of the Sylvian Veins for the Distal Transsylvian Approach

Methods for preservation of the sylvian veins in the transsylvian approach have not been established because of the considerable variations. This study attempted to classify the sylvian veins to facilitate systematic dissection of the sylvian fissure for sylvian veins to be preserved. The operative anatomy of the sylvian vein was examined in 82 hemispheres. The type of drainage and the pattern of branching were investigated. The superficial sylvian vein (SSV) was classified into three types according to the number of stems draining into the dural sinus on the inner surface of the sphenoid bone: The SSV was absent or hypoplastic in eight cases, the SSV was single in 38 cases, and the SSV was double in 36 cases. The SSV drained into neither the sphenoparietal sinus nor the cavernous sinus in nine cases. An anastomosis between the SSV and the deep middle cerebral vein (DMCV) was observed in 42 cases. The frontobasal bridging vein (FBBV) drained into the sphenoparietal sinus in 47 cases. The type of connection was further subdivided into four types according to the connections with the DMCV and FBBV. The venous anatomy of sylvian fissure indicates that dissection (skeletonization) of the main stem of sylvian veins from the temporal lobe should be performed to preserve the tributaries from the frontal lobe.

Effects of habitual cigarette smoking on higher cortical function in patients with unruptured cerebral aneurysms

Postoperative changes in higher cortical function and cerebral blood flow (CBF) were investigated in patients with unruptured cerebral aneurysms to assess the effect of habitual smoking on the known transient changes after aneurysm surgery. Fifty-six adults with unruptured cerebral aneurysms, including 11 heavy smokers (smoking index > or = 600) and 45 non-smokers, were evaluated using three neuropsychological examinations, the Mini-Mental State Examination, the Maze test, and the Kana-hiroi test, and single photon emission computed tomography to measure CBF before and after surgery. Neuropsychological changes were assessed by reliable change indices to take into account the practice effects. The scores of at least one examination decreased in 15 of 56 patients 1 month after surgery. On the Maze test, five of 11 heavy smokers and five of 45 non-smokers deteriorated after surgery, showing a significant difference (p = 0.018). The CBF in heavy smokers often decreased after surgery, but there was no statistically significant difference in logistic regression. Three months after surgery, the neuropsychological scores of 13 of the 15 deteriorated patients recovered to the preoperative level. Higher cortical function in heavy smokers with unruptured cerebral aneurysms often decreases transiently after operation, compared to non-smokers. Therefore, surgery planning for heavy smokers with unruptured cerebral aneurysms should consider this outcome.

Postoperative cortical venous infarction in tumours firmly adherent to the cortex

It is sometimes difficult to separate extra-axial tumours from the cortical veins in case of tumours attaching tightly to the cortex and the cortical veins. We present two patients having a postoperative cortical venous infarction. A 59 year old female had convexity meningioma above the motor cortex where abnormal cortical anastomotic veins developed. Transient hemiparesis occurred after total removal of the tumour because of venous infarction and cyst formation resulting from sacrifice of these veins which were tightly adherent to the tumour surface. A 15 year old boy with immature teratoma of the pineal region, showing several draining veins around the vascular-rich tumour, presented transient drowsiness, diplopia and partial impairment of bilateral visual acuity postoperatively because of localised cortical brain and venous damage. It is important to make an effort to preserve main cortical veins during operation as much as possible, even if the tumour adheres to the cortical surface.

The regional cerebral blood flow amelioration of argatroban in the acute stage of cerebral thrombosis

Cerebral blood flow changes by argatroban in the acute stage of cerebral thrombosis have been investigated with the use of stable xenon computed tomography (Xe/CT). The study group consisted of 14 cases (7 males, 7 females) with the average age of 59 years old (ranging from 21 to 79 years of age). We evaluated the cerebral blood flow change after an intravenous drip infusion of 10 mg of argatroban. After the administration of argatroban, we recognized a significant increase in the blood flow (24.4 +/- 5.0 ml/100 g/min to 28.4 +/- 2.7 ml/100 g/min, p < 0.05) in the blood flow area of lower than 30 ml/100 g/min in the affected vascular territory. As a conclusion, we found that argatroban improves ischemic symptoms through the amelioration of blood flow in the penumbra area.

Tumor-related venous obstruction and development of peritumoral brain edema in meningiomas

OBJECTIVE

The exact pathogenesis of peritumoral brain edema (PTBE) in meningiomas is still unknown. A number of different pathophysiological hypotheses have been considered. A detrimental effect of tumor-related venous obstruction has been suggested as one pathogenetic mechanism. We sought to characterize the significance of venous stasis in the development of PTBE in meningiomas.

METHODS

Angiograms for 134 patients with 136 intracranial meningiomas were analyzed. Pathological changes affecting cortical veins, sylvian veins, bridging veins, deep veins, transmedullary veins, and dural sinuses were evaluated. From preoperative computed tomographic scans, the total tumor volume, the tumor/PTBE volume ratio (edema index [EI]), and the location of the edema were determined. For statistical evaluation, meningiomas associated with pathological venous drainage were compared with size-matched controls.

RESULTS

The edema incidence and the mean EI were not different for meningiomas with unselected signs of obstructed venous drainage, compared with controls. In particular, lesions with involvement of cortical veins, bridging veins, and dural sinuses showed no higher edema incidence. However, meningiomas associated with venous changes in sylvian veins (EI = 4.9 versus EI = 2.7; P < 0.004) and with dysplastic transmedullary veins (EI = 3.3 versus EI = 1.7; P < 0.04) showed significantly higher mean EI values, compared with meningiomas without involvement of these vessels.

CONCLUSION

Our data suggest that tumor-related venous obstruction does not play an essential role in the development of PTBE for the majority of meningiomas. For a small subgroup of meningiomas with involvement of sylvian veins or development of dysplastic transmedullary veins, changes in venous drainage may aggravate preexisting PTBE.

The variations of Sylvian veins and cisterns in anterior circulation aneurysms. An operative study

The anatomical variations of Sylvian vein and cistern were investigated during the pterional approach in 230 patients with 276 aneurysms of anterior circulation arteries, that were operated on at the Neurosurgical Department of Atatürk University Medical School. Erzurum, Türkiye. All patients underwent radical surgery for aneurysm by the right or left pterional approach. The findings were recorded during surgical intervention and observed through the slides and videotapes of the operations. In our study, we surgically classified the variations of the Sylvian vein, according to its branching and draining patterns. Type I: The fronto-orbital (frontosylvian), fronto-parietal (parietosylvian) and anterior temporal (temporosylvian) veins drain into one sylvian vein. Type II: Two superficial Sylvian veins with separated basal vein draining into the sphenoparietal and Rosenthal's basal vein. Type III: Two superficial Sylvian veins draining into the sphenoparietal and the superior petrosal veins. Type IV: Hypoplastic superficial Sylvian vein and the deep one. Four types of Sylvian vein variations were defined as follows. The Type I was seen in 45% (n = 103), the Type II was found in 29% (n = 67), Type III was recorded in 15% (n = 34) and Type IV, or hypoplastic and deep form was discovered in 11% (n = 26) of patients. The course of the Sylvian vein was on the temporal side (Temporal Coursing) in 70 percent of the cases (n = 160), on the frontal side (Frontal Coursing) in 19% of the patients (n = 45) and in 8 percent of the cases (n = 18) in the deep localization (Deep Coursing). Only 3 percent of the cases (n = 7) showed a mixed course. The variations of the Sylvian cisterns were classified into three types, according to the relationships between the lateral fronto-orbital gyrus and the superior temporal gyrus. In Sylvian Type, the frontal and temporal lobes are loosely (Sylvian Type A, Large) or tightly (Sylvian Type B, Close and Narrow) approximated on the surface thereby covering the area of the Sylvian cistern. In frontal type, the proximal, part of the lateral fronto-orbital gyrus herniated into the temporal lobe. In temporal type, the proximal part of the superior temporal gyrus hemiated into the lateral fronto-orbital gyrus. The variations of the Sylvian cisterns in 230 patients were as follows: in 31% (n = 71) Sylvian Type A, in 21% (n = 48) Sylvian Type B, in 34% (n = 78) Frontal Type, and in 14% (n = 33) Temporal Type. We concluded that venous perfusion disorder of the brain is the most important factor during the pterional approach. Careful intraoperative assessment and protection of the Sylvian vein, which is a surgical pitfall, is an indispensable part of the operation. The recognition of the anatomical variations of the Sylvian vein and cistern, and the detailed knowledge of the microvascular relationships at that level will allow the neurosurgeon to construct a better and safter microdissection plan, to save time and can prevent postoperative neurological deficits.