Cranial base approaches to intracranial aneurysms in the subarachnoid space

1-Piece Versus 2-Piece Fronto-Temporo-Orbito-Zygomatic Craniotomy: A Narrative Overview of Evolution

BACKGROUND

The fronto-temporo-orbito-zygomatic (FTOZ) craniotomy is a commonly utilized surgical approach for many complex skull base lesions, especially lesions traversing skull base compartments. This craniotomy has evolved over multiple stages, originating from the classic pterional craniotomy and many variations that have emerged over time.

METHODS

Few clinical and anatomic studies have both shaped these craniotomies as well as provided immense information about instances in which they are most useful. We review the origin and history of the one-piece and two-piece fronto-temporo-orbito-zygomatic craniotomy and deliberate their advantages and disadvantages.

RESULTS

The FTOZ craniotomy provides access to the orbit as well as to multiple compartments in the cranium (anterior, middle and upper third posterior cranial fossae); thus, offering a multi-corridor approach to complex skull base lesions. The one-piece and two-piece fronto-temporo-orbitozygomatic craniotomies are two particularly notable variations that have stood the test of time. Selection between the two variations is mostly surgeon preference and comfort with the technique; however, there are certain indications that specifically suit each approach. Additionally, a pictorial review has been crafted to clearly illustrate the cuts to be made in both methods.

CONCLUSION

Understanding the evolution of this craniotomy and surgical approach provides an insight into accessing complex skull base pathologies with minimal brain retraction via safe and viable corridors.

Peritrigeminal Safe Entry Zone Access to Anterolateral Pons Using the Presigmoid Retrolabyrinthine Suprameatal Approach: A Cadaveric Morphometric Study

BACKGROUND AND OBJECTIVES

Access to the anterolateral pontine lesions can be achieved through the peritrigeminal and supratrigeminal safe entry zones using Kawase, retrosigmoid, or translabyrinthine approaches. However, these approaches entail shallow extensive dissection, tangential access, and compromise vestibulocochlear function. We aimed to investigate infratentorial presigmoid retrolabyrinthine approach to access pontine lesions through the peritrigeminal zone.

METHODS

We performed 10 presigmoid retrolabyrinthine suprameatal approach dissections in 5 cadaveric heads. Anatomic-radiological characteristics and variations were evaluated. Six morphometric parameters were measured and analyzed to predict surgical accessibility.

RESULTS

The pontine infratrigeminal area was accessible in all patients. The mean exposed area of the anterolateral pontine surface was 98.95 cm 2 (±38.11 cm 2 ). The mean length of the exposed trigeminal nerve was 7.9 cm (±2.9 cm). Preoperative anatomic-radiological parameters may allow to select patients with favorable anatomy that offers appropriate surgical accessibility to the anterior pontine cavernoma through a presigmoid retrolabyrinthine corridor.

CONCLUSION

Anterolateral pontine lesions can be accessed through a minimally invasive infratentorial presigmoid retrolabyrinthine approach by targeting the infratrigeminal safe entry zone. Further clinical studies should be conducted to evaluate the viability of this technique for treating these complex pathologies in real clinical settings.

A Frontal Route to Middle and Posterior Cranial Fossa: Quantitative Study for the Lateral Transorbital Endoscopic Approach and Comparison with the Subtemporal Approach

BACKGROUND

Skull base lesions within the middle cranial fossa (MCF) remain challenging. Recent reports suggest that transorbital endoscopic approaches (TOEAs) might be particularly suitable to access the MCF and expose the lateral wall of the cavernous sinus and the Meckel's cave.

METHODS

The present study was developed to compare the nuances of the subtemporal approach (STA) with those of the lateral TOEA (LTOEA) to the MCF and posterior cranial fossa (PCF) in cadaveric specimens. After orbital craniectomy, interdural opening of the cavernous sinus lateral wall (CSlw), exposure of the Gasserian ganglion, and extradural elevation of the temporal lobe was performed. Next, anterior endoscopic petrosectomy was performed and the PCF was accessed. We quantitatively analyzed and compared the angles of attack and distances between LTOEA and STA to different structures at the CSlw, petrous apex (PA), and PCF.

RESULTS

Cadaveric dissection through the LTOEA completely exposed the CSlw and PA. LTOA exhibited larger distances than the STA to all targets. Importantly, these differences were greater at the PA and its surrounding key anatomic landmarks. The horizontal and vertical angles of attack allowed by the LTOA were smaller both for the CSlw and PA. However, these differences were not significant for the vertical angle of attack at the CSlw.

CONCLUSIONS

LTOEA provides a direct ventral route to the medial aspect of MCF, PA, and PCF. Although TOEAs are versatile approaches, the unfamiliar surgical anatomy and limited instrument maneuverability demand extensive cadaveric dissection before moving to the clinical setting.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Middle Fossa Approaches and Anterior Petrosectomy, Surgical Principles, and Illustrative Cases

Introduction The middle fossa (MF) approaches encompass a group of versatile surgical accesses to pathologies in the MF, internal auditory canal (IAC), and superomedial aspect of the posterior fossa. Although many descriptions of the MF approaches have been published, a practical surgical guide that allows an easy understanding for Skull Base trainees is needed.

Methods Three formalin-fixed, colored-injected specimens were dissected under microscopic magnification (six sides). A MF craniotomy followed by IAC drilling was performed on three sides, and anterior petrosectomy (AP) was performed in the remaining three sides. The anatomical dissection was documented in stepwise three-dimensional photographic images. Following dissection, representative case applications were reviewed.

Results The MF approach provides direct access to the MF structures and IAC. The AP provides excellent access to the superomedial aspect of the posterior fossa. Key common steps include: positioning and skin incision; scalp and muscle flaps; burr holes; craniotomy flap elevation; dural dissection along the petrous ridge; division of the middle meningeal artery; and exposure of the greater superficial petrosal nerve, tegmen tympani, and V3. Then, to approach the IAC: superior IAC drilling, and longitudinal dura opening. The area drilled in the AP approach forms a pentagon limited by the petrous internal carotid artery, cochlea, IAC, petrous ridge, and lateral border of V3.

Conclusion The MF approaches are challenging. Operatively oriented skull base dissections provide a crucial foundation for learning these techniques. We describe comprehensive step-by-step approaches intended to develop familiarity in the cadaver laboratory and facilitate understanding of their potential for skull base disorders. Basic surgical principles are described to help in the operating room as well as illustrative cases.

Tailored Skull Base Approach to Management of Intracranial Aneurysms

Surgical management of intracranial aneurysms (IAs) remains one of the most challenging and dynamic tasks for neurosurgeons. The rivalry between modern time microsurgery and progress in endovascular intervention has provided a great arena for advancement and lead to redefine training concept and referral pattern. Both approaches has its own merits, risks and complications and the best outcome is achieved by case individualization and complimentary multidisciplinary approach.The recent innovation in microscopic and endoscopic tailored skull base approaches, intraoperative 3D and ICG video-angiography, design of high quality aneurysm clips, and refinement of cerebral bypass techniques enhance IAs neurosurgical management and their clinical outcome. The command of tailored skull base approaches should be part of the training curriculum of young generation of neurosurgeons to compliment the emerging treatment options of endovascular intervention.

Oscillopsia following orbitotomy for intracranial tumor resection

Background:

Oscillopsia is a visual phenomenon in which an individual perceives that their environment is moving when it is in fact stationary. In this report, we describe two patients with pulsatile oscillopsia following orbitocranial approaches for skull base meningioma resection.

Case Description:

Two patients, both 42-year-old women, underwent orbitocranial approaches for resection of a right sphenoid wing (Patient 1) and left cavernous sinus (Patient 2) meningioma. Patient 1 underwent uncomplicated resection and was discharged home without neurologic or visual complaints; she presented 8 days later with pulsatile oscillopsia. This was managed expectantly, and MRA revealed no evidence of vascular pathology. She has not required intervention as of most recent follow-up. Patient 2 developed trochlear and trigeminal nerve palsies following resection and developed pulsatile oscillopsia 4 months postoperatively. After patching and corrective lens application, the patient’s symptoms had improved by 26 months postoperatively.

Conclusion:

Oscillopsia is a potential complication following skull base tumor resection about which patients should be aware. Patients may improve with conservative management alone, although the literature describes repair of orbital defects for ocular pulsations in traumatic and with some developmental conditions.

Surgical Anatomy Applied to the Resection of Craniopharyngiomas: Anatomic Compartments and Surgical Classifications

BACKGROUND

Resective surgery remains the main treatment option for most patients with craniopharyngiomas. Understanding of the microsurgical anatomy of the sella and suprasellar region and its relationship with these tumors is necessary to achieve effective surgical treatment and minimize complications. In this article, we review the surgical anatomy related to craniopharyngiomas and divide it in 5 compartments according to tumor extension.

METHODS

Endoscopic and microsurgical dissection were performed in 3 freshly injected cadaver heads at the Weill Cornell Surgical Innovations Laboratory (New York, New York, USA) and at the Surgical Skills Center at Mount Sinai Hospital (Toronto, Ontario, Canada). Tumor extension was classified as 1) inferomedial or sellar, 2) superomedial or suprasellar, 3) lateral or sylvian, 4) posterior or interpeduncular/prepontine, and 5) intraventricular. The selection of surgical approaches is discussed based on the anatomic nuances of each these regions. In addition, we reviewed the literature regarding previous anatomic classifications for resection of craniopharyngiomas.

RESULTS

Different approaches should be considered according to tumor extension into different compartments. Purely sellar tumors are amenable to endoscopic transsellar approaches, whereas those with a suprasellar extension require an extended transtuberculum approach. In some of those patients, a narrow chiasm-pituitary window may block access to the tumor and a transcranial translamina terminalis approach may be favored. Tumors occupying the interpeduncular fossa may pose a significant challenge for an endoscopic endonasal approach and transcranial approaches. Transcavernous approaches and anterior and posterior clinoidectomies may be required for adequate exposure in such patients. Translamina terminalis and/or transcallosal approaches are recommended for resection of purely intraventricular tumors. Tumors extending into the lateral compartment should be considered for transcranial frontotemporal approaches.

CONCLUSIONS

The understanding of such anatomic nuances aids in the selection of the most appropriate surgical approach and in the prevention of potential complications. Because most craniopharyngiomas are midline lesions, the endoscopic endonasal approach represents an excellent approach for most of those tumors. However, transcranial approaches should be considered for tumors with extension into the lateral compartment and for selected tumors involving the ventricular compartment (purely intraventricular tumors and those with extension to the foramen of Monro and/or lateral ventricles).

The Orbitozygomatic Craniotomy and Its Judicious Use

The concept of maximizing bone removal along the skull base has been advocated to expand the operative space for large, firm, and encasing ventral and ventrolateral skull base tumors. However, indications for the use of such osteotomies have not been well defined. The improved maneuverability and enhanced extent of expansion of the operative corridor via the skull base approaches compared to those of standard craniotomies have been based on cadaveric studies that might not simulate the operative environment realistically. Bony removal alone is not adequate to protect neurovascular structures, and strategic use of dynamic retraction and innovative operative routes are some of the other factors that contribute to successful microsurgery. In this analysis, the more discriminate indications and modified techniques for orbitozygomatic osteotomy are discussed.

Quantitative analysis of the surgical exposure and surgical freedom between transcranial and transorbital endoscopic anterior petrosectomies to the posterior fossa

OBJECT

This study proposes a variation of the transorbital endoscopic approach (TOEA) that uses the lateral orbit as the primary surgical corridor, in a minimally invasive fashion, for the posterior fossa (PF) access. The versatility of this technique was quantitatively analyzed in comparison with the anterior transpetrosal approach (ATPA), which is commonly used for managing lesions in the PF.

METHODS

Anatomical dissections were carried out in 5 latex-injected human cadaveric heads (10 sides). During dissection, the PF was first accessed by TOEAs through the anterior petrosectomy, both with and without lateral orbital rim osteotomies (herein referred as the lateral transorbital approach [LTOA] and the lateral orbital wall approach [LOWA], respectively). ATPAs were performed following the orbital approaches. The stereotactic measurements of the area of exposure, surgical freedom, and angles of attack to 5 anatomical targets were obtained for statistical comparison by the neuronavigator.

RESULTS

The LTOA provided the smallest area of exposure (1.51 ± 0.5 cm2, p = 0.07), while areas of exposure were similar between LOWA and ATPA (1.99 ± 0.7 cm2 and 2.01 ± 1.0 cm2, respectively; p = 0.99). ATPA had the largest surgical freedom, whereas that of LTOA was the most restricted. Similarly, for all targets, the vertical and horizontal angles of attack achieved with ATPA were significantly broader than those achieved with LTOA. However, in LOWA, the removal of the lateral orbital rim allowed a broader range of movement in the horizontal plane, thus granting a similar horizontal angle for 3 of the 5 targets in comparison with ATPA.

CONCLUSIONS

The TOEAs using the lateral orbital corridor for PF access are feasible techniques that may provide a comparable surgical exposure to the ATPA. Furthermore, the removal of the orbital rim showed an additional benefit in an enhancement of the surgical maneuverability in the PF.

Three-Piece Orbitozygomatic Craniotomy: Anatomical and Clinical Findings

OBJECTIVE

To describe the technical details of 3-piece orbitozygomatic (OZ) craniotomy using a diamond threadwire saw as an alternative to cutting the orbital rim and zygoma.

METHODS

The details of this procedure are presented by cadaver dissection and a surgical case.

RESULTS

Three-piece OZ craniotomy consists of 3 steps of bone flap elevation. First, the zygomatic arch is divided and reflected downward with the temporal muscle. This provides adequate exposure around the inferior orbital fissure with less skin flap retraction. In the second step, frontotemporal craniotomy is performed close to the skull base without the requirement for additional craniectomy. Finally, the superolateral wall of the orbital bone flap is elevated. Cutting the orbital rim and zygoma with a diamond threadwire saw allows reconstruction with a minimal bone gap.

CONCLUSIONS

The herein-described 3-piece OZ craniotomy technique is simple and provides excellent brain exposure equivalent to that achieved by 1- and 2-piece OZ craniotomy while minimizing flap retraction and requiring less additional bone removal.

Pure Endoscopic Lateral Orbitotomy Approach to the Cavernous Sinus, Posterior, and Infratemporal Fossae: Anatomic Study

Objective  The aim of this anatomic study is to describe a fully endoscopic lateral orbitotomy extradural approach to the cavernous sinus, posterior, and infratemporal fossae. Material and Methods  Three prefixed latex-injected head specimens (six orbital exposures) were used in the study. Before and after dissection, a computed tomography scan was performed on each cadaver head and a neuronavigation system was used to guide the approach. The extent of bone removal and the area of exposure of the targeted corridor were evaluated with the aid of OsiriX software (Pixmeo, Bernex, Switzerland). Results  The lateral orbital approach offers four main endoscopic extradural routes: the anteromedial, posteromedial, posterior, and inferior. The anteromedial route allows a direct route to the optic canal by removal of the anterior clinoid process, whereas the posteromedial route allows for exposure of the lateral wall of the cavernous sinus. The posterior route is targeted to Meckel's cave and provides access to the posterior cranial fossa by exposure and drilling of the petrous apex, whereas the inferior route gives access to the pterygopalatine and infratemporal fossae by drilling the floor of the middle cranial fossa and the bone between the second and third branches of the trigeminal nerve. Conclusion  The lateral orbitotomy endoscopic approach provides direct access to the cavernous sinus, posterior, and infratemporal fossae. Advantages of the approach include a favorable angle of attack, minimal brain retraction, and the possibility of dissection within the two dural layers of the cavernous sinus without entering its neurovascular compartment.

Single piece fronto-temporo-orbito-zygomatic craniotomy: a personal experience and review of surgical technique

BACKGROUND

Fronto-Temporo-Orbito-Zygomatic (FTOZ) craniotomy has progressed from its humble beginnings. Numerous variations including one piece, two piece and even three piece FTOZ craniotomies have been described. The ideal technique still remains elusive and its use remains restricted to a few specialised centres even when benefits far outweigh the surgical difficulties.

OBJECTIVE

To analyse 11 cases in which single piece FTOZ craniotomy was used and to review the steps of surgery along with its advantages.

METHODS

A total of 11 cases of skull base lesions were operated over a period of 30 months and followed up for a minimum period of 6 months. They were analysed for intraoperative benefits, requirement of cerebral retraction, surgical difficulties, post op recovery, complications faced and post-op cosmetic appearance.

RESULT

A total of nine cases had tumours of skull base including Spheno-Petro-Clival meningiomas, Trigeminal schwannomas, Solitary fibrous histiocytoma and two had giant aneurysms of P1 segment. Intraoperative cerebral retraction was significantly less. There were two post-op deaths. Three patients had temporary and 1 patient had permanent third nerve deficit. There was no injury to periorbital fat and post op cosmetic appearance was good.

CONCLUSION

Single piece FTOZ craniotomy is no more difficult than two or three piece craniotomy, rather it facilitates a rapid craniotomy closure with excellent handling of single piece of bone. It provides a wide, multidirectional access to skull base. Lesions become shallow and their access easier. Benefits far outweigh the difficulties if any, and its use should be encouraged even at centres outside of the specialised units.

Modified Orbitozygomatic Approach without Orbital Roof Removal for Middle Fossa Lesions

Objective

The purpose of the present study was to describe an OrBitoZygomatic (OBZ) surgical variant that implies the drilling of the orbital roof and lateral wall of the orbit without orbitotomy.

Methods

Design : cross-sectional study. Between January 2010 and December 2014, 18 patients with middle fossa lesions underwent the previously mentioned OBZ surgical variant. Gender, age, histopathological diagnosis, complications, and percentage of resection were registered. The detailed surgical technique is described.

Results

Of the 18 cases listed in the study, nine were males and nine females. Seventeen cases (94.5%) were diagnosed as primary tumoral lesions, one case (5.5%) presented with metastasis of a carcinoma, and an additional one had a fibrous dysplasia. Age ranged between 27 and 73 years. Early complications were developed in four cases, but all of these were completely resolved. None developed enophthalmos.

Conclusion

The present study illustrates a novel surgical OBZ approach that allows for the performance of a simpler and faster procedure with fewer complications, and without increasing surgical time or cerebral manipulation, for reaching lesions of the middle fossa. Thorough knowledge of the anatomy and surgical technique is essential for successful completion of the procedure.

One Piece Orbitozygomatic Approach Based on the Sphenoid Ridge Keyhole: Anatomical Study

The one-piece orbitozygomatic (OZ) approach is traditionally based on the McCarty keyhole. Here, we present the use of the sphenoid ridge keyhole and its possible advantages as a keyhole for the one-piece OZ approach. Using transillumination technique the osteology of the sphenoid ridge was examined on 20 anatomical dry skull specimens. The results were applied to one-piece OZ approaches performed on freshly frozen cadaver heads. We defined the center of the sphenoid ridge keyhole as a superficial projection on the lateral skull surface of the most anterior and thickest part of the sphenoid ridge. It was located 22 mm (standard deviation [SD], 0.22 mm) from the superior temporal line; 10.7 mm (SD, 0.08 mm) posterior and 7.1 mm (SD, 0.22 mm) inferior to the frontozygomatic suture. The sphenoid ridge burr hole provides exposure of frontal, temporal dura as well as periorbita, which is essential for the later bone cuts. There is direct access to removal of the thickest (sphenoidal) part of the orbital roof, after which the paper-thin (frontal) part of the orbital roof is easily fractured. The sphenoid ridge is an easily identifiable landmark on the lateral skull surface, located below the usual placement of the McCarty keyhole, with comparative exposure.

Morphometric Analysis of Bone Resection in Anterior Petrosectomies

Introduction The anterior petrosectomy is a well-defined skull base approach to lesions such as petroclival meningiomas, posterior circulation aneurysms, petrous apex lesions (chondrosarcomas, cholesteatomas), ventrolateral brainstem lesions, clival chordomas, trigeminal neurinomas, and access to cranial nerves III, IV, V, and VII. Methods and Materials Fourteen anterior petrosectomies on eight cadaveric heads were performed in a skull base dissection laboratory. Predissection and postdissection thin-cut computed tomography scans were obtained to compare the bone resection. A computer program was used (InVivo5, Anatomage, San Jose, California, United States) to measure the bone resection and the improved viewing angle. Results The average bone removed in each plane was as follows: anterior to posterior plane was 10.57 mm ± 2.00 mm, superior to inferior was 9.39 mm ± 1.67 mm, and lateral to medial was 17.46 mm ± 4.64 mm. The average increased angle of view was 13.01 ± 2.35 degrees (Table 1). The average volume was 1786.94 ± 827.40 mm(3). Conclusions Anterior petrosectomy is a useful approach to access the ventrolateral brainstem region. We present a cadaveric study quantitating the volume of bone resection and improvement in the viewing angle. These data provide useful preoperative information on the utility of this skull base approach and the gain in the viewing angle after bony removal.

The 1-piece transbasal approach: operative technique and anatomical study

OBJECT

The transbasal approach (TBA) is an anterior skull base approach, which provides access to the anterior skull base, sellar-suprasellar region, and clivus. The TBA typically involves a bifrontal craniotomy with orbital bar and/or nasal bone osteotomies performed in 2 separate steps. The authors explored the feasibility of routinely performing this approach in 1 piece with a quantitative cadaveric anatomical study, and present an operative case example of their approach.

METHODS

Seven latex-injected cadaveric heads underwent a 1-piece TBA, followed by additional bone removal typical for a traditional 2-piece approach. Six surgical angles relative to the pituitary stalk, as well as the surface area of the orbital roof osteotomy, were measured before and after additional bone removal. The vertical angle from the frontonasal suture to the foramen cecum was measured in all specimens. In addition to an anatomical study, the authors have used this technique in the operating room, and present an illustrative case of resection of an anterior skull base meningioma.

RESULTS

Morphometric results were as follows: the vertical angle from the frontonasal suture to the foramen cecum ranged from 17.4° to 29.7° (mean 23.8° ± 4.8°) superiorly. Of the 6 surgical angle measures, only the middle horizontal angle was increased in the 2-piece versus the 1-piece approach (mean 43.4° ± 4.6° vs 43.0° ± 4.3°, respectively; p = 0.049), with a mean increase of 0.4°. The surface area of the orbital osteotomy was increased in the 2-piece versus the 1-piece approach (mean 2467 mm(2) ± 360 mm(2) vs 2045 mm(2) ± 352 mm(2), respectively; p < 0.001). The patient in the illustrative clinical case had a good outcome, both clinically and cosmetically.

CONCLUSIONS

The 1-piece TBA provides an alternative to the traditional 2-piece approach. It allows easier reconstruction, potentially decreased operative time, and improved cosmesis. While more of the orbital roof can be removed with the 2-piece approach, this additional bone removal offers only a small increase in 1 of 6 surgical angles that were measured.

Intradural anterior petrosectomy for petroclival meningiomas: a new surgical technique and results in 5 patients

Excision of petroclival meningiomas remains a surgical challenge. Extradural anterior petrosectomy is widely used as a skull base approach for these tumors; however, this approach has significant procedure-related morbidity. The authors describe an alternative technique of tailored intradural petrosectomy for removal of petroclival meningiomas. This technique was used successfully in 5 patients. Gross-total or near-total resection was possible in 2 patients, whereas a subtotal removal was achieved in 3 patients, without significant morbidity. The petrous drilling was tailored depending on the extent of tumor. Transsylvian intradural anterior petrosectomy is a safe approach for petroclival meningiomas. This approach avoids problems related to subtemporal retraction and rationalizes the degree of bone drilling.

Accessing the basilar artery apex: is the temporopolar transcavernous route an anatomically advantageous alternative?

The restricted operative field, difficulty of obtaining proximal vascular control, and close relationship to important anatomic structures limit approaches to basilar apex aneurysms. We used a cadaveric model to compare three surgical transcavernous routes to the basilar apex in the neutral configuration. Five cadaveric heads were dissected and analyzed. Working areas and length of exposure provided by the transcavernous (TC) approach via pterional, orbitozygomatic, and temporopolar (TP) routes were measured along with assessment of anatomic variation for the basilar apex region. In the pterional TC and orbitozygomatic TC approaches, the mean length of exposure of the basilar artery measured 6.9 and 7.2 mm, respectively (p = NS). The mean length of exposure in a TP TC approach increased to 9.3 mm (p < 0.05). Compared with the pterional and orbitozygomatic approaches, the TP TC approach provided a larger peribasilar area of exposure ipsilaterally and contralaterally (p < 0.05). The multiplanar working area related to the TP TC approach was 77.7 and 69.5% wider than for the pterional TC and orbitozygomatic TC, respectively. For a basilar apex in the neutral position, the TP TC approach may be advantageous, providing a wider working area for the basilar apex region, improving maneuverability for clip application, fine visualization of perforators, and better proximal control.

Unilateral subfrontal approach to anterior communicating artery aneurysms: A review of 28 patients

BACKGROUND

The pterional approach is the most common for AComm aneurysms, but we present a unilateral approach to a midline region for addressing the AComm complex. The pure subfrontal approach eliminates the lateral anatomic dissection requirements without sacrificing exposure. The subfrontal approach is not favored in the US compared to Asia and Europe. We describe our experience with the subfrontal approach for AComm aneurysms treated at a single institution.

METHODS

We identified 28 patients treated for AComm aneurysms through the subfrontal approach. Patient records and imaging studies were reviewed. Demographics and case data, as well as clinical outcome at 6 weeks and 1 year were collected.

RESULTS

Mean patient age was 48 (range 21-75) years and 64% suffered subarachnoid hemorrhage (SAH). All aneurysms were successfully clipped. Gyrus rectus was resected in 57% of cases, more commonly in ruptured cases. Intraoperative rupture occurred in 11% of cases. The average operative time was 171 minutes. There were two patient deaths. Ninety-two percent of patients had a Glasgow Outcome Scale (GOS) of 5 at 6 weeks. All unruptured patients had a GOS of 5. At 12 months, 96% of all patients had a GOS of 5.

CONCLUSIONS

The subfrontal approach provides an efficient avenue to the AComm region, which reduces opening and closing friction but still yields a comprehensive operative window for access to the anterior communicating region.

Far-lateral approach for lower basilar artery aneurysms

OBJECTIVES

Aneurysms of the lower basilar artery are surgically difficult to expose and clip. Various cranial base approaches, which are associated with significant morbidity, have been used to access this region. We have used the far-lateral approach without occipital condyle drilling for clipping of lower basilar junction aneurysms to assess the exposure for adequate visualization and clipping, and to study the complications and outcome.

DESIGN

Retrospective review of data.

SETTING

Between 1997 and 2001, four patients with lower basilar artery aneurysms were operated on at Louisiana State University Health Sciences Center in Shreveport. The far-lateral approach without drilling of the occipital condyle was used in each procedure.

PARTICIPANTS

Cases of basilar artery aneurysms.

MAIN OUTCOME MEASURES

Glasgow Outcome Scale (GOS) score.

RESULTS

All four aneurysms were clipped successfully. All patients had good outcome (GOS scores of 5 and 4). There were no instances of cerebrospinal fluid leakage or pseudomeningocele. Two patients experienced transient morbidity in the form of voice hoarseness and swallowing difficulty.

CONCLUSION

The far-lateral approach without drilling of the occipital condyle adequately exposed the lower basilar artery for successful clipping of aneurysms and was associated with minimal morbidity.

Lateral orbital rim osteotomy in the treatment of certain skull base lesions

Quantitative data from a recent human cadaveric study suggested that removal of the lateral orbital rim alone may be sufficient to reach many targets for which the orbitozygomatic craniotomy has been used. Consequently, a lateral orbital rim osteotomy was substituted for an orbitozygomatic craniotomy in seven patients with a variety of pathologies located in the anterior, middle, and interpeduncular fossae. In each case, lateral orbitotomy provided a satisfactory surgical corridor for diagnosis and treatment. Compared with the orbitozygomatic craniotomy, the lateral orbital rim osteotomy offers several advantages: technical simplicity, shorter operating time, and a low risk of postoperative malocclusion. If, however, prolonged access to a wide expanse of the anterior portion of the middle fossa and inferotemporal area is needed, an orbitozygomatic approach is a better choice.

Anatomo-radiological evaluation of lateral approaches to the skull base

Our objective is to correlate the anatomical exposure provided by complex skull base approaches to the lateral skull base with their CT and MRI scans counterparts and to introduce a modular concept emphasizing the derivation of complex skull base approaches from simpler ones.We executed 10 lateral approaches to the skull base in 20 embalmed cadaveric heads (40 sides). Each approach was executed a minimum of three times on each specimen. These approaches were the pterional and its modifications, the subtemporal and its modifications, and the suboccipital and its modifications. We correlated the approaches and the areas of the skull base exposed by scanning the surgical cavity filled with material imageable by CT and MRI and throughly surveying the operative field.Visualization of the area of the skull base exposed was excellent using our CT-MRI imageable cadaveric preparation. The topographic areas of the skull base exposed correlated well with their radiological counterparts.The areas of the skull base exposed by each of the complex surgical approaches to the skull base were clearly delineated by using our anatomo-radiological correlation. Complex approaches to the skull base are formed by simple neurosurgical approaches (building blocks) to which different modules are added.

The orbitopterional approach for large and giant middle cerebral artery aneurysms: a report of two cases and literature review

We report two cases of complex middle cerebral artery aneurysms that were surgically treated using the orbitopterional approach in a two-piece method. The objective of this work is to discuss the usefulness of the orbitopterional approach in the surgical management of large and giant middle cerebral artery aneurysms. A 32-year-old man with a giant aneurysm and a 50-year-old woman with a large and complex aneurysm presented with subarachnoid hemorrhages. Both aneurysms were successfully clipped through an orbitopterional approach. This approach permits a more basal view of the vascular structures with only a minor retraction of frontal lobe. It also increases the view angle and amount of working space available. This approach should be considered as an alternative to the classic pterional craniotomy for the surgical management of such complex lesions.

Endovascular treatment of aneurysms arising from the basilar artery trunk and branches

This study reports our experience with the endovascular treatment of basilar artery (BA) trunk and branch aneurysms. Subjects included 16 patients with BA trunk and branch aneurysms who underwent endovascular treatment in our hospital from October 2000 to October 2009, including four patients with associated arteriovenous malformation (AVM), two with associated moyamoya disease, one with multiple aneurysms at adjacent sites, and one with a distant aneurysm. Endovascular coil embolization, together with stent or balloon assistance when necessary, or while occluding the parent artery was performed. Associated diseases were managed intraoperatively or in the second stage, or treated with gamma knife radiotherapy, or followed up. Two patients with unsuccessful embolization died of re-rupture at the fourth month and fifth month follow-up. The remaining 14 patients reported good outcomes and experienced no re-rupture of either the aneurysm or associated disease. Angiographic follow-ups were conducted for the 14 patients for six to 12 months. Digital subtraction angiography (DSA) examination at the last follow-up showed no recurrence of the BA trunk and branch aneurysms. Together, BA trunk and branch aneurysms should be actively managed via endovascular techniques to prevent serious consequences due to aneurysm rupture and bleeding. Favorable outcomes can be obtained by the proper selection of endovascular treatment regimens.

The presigmoid approach to anterolateral pontine cavernomas. Clinical article

OBJECT

Anterolateral cavernomas of the pons have been surgically removed via a variety of approaches, commonly retrosigmoid or transventricular. The goal in this study was to evaluate the presigmoid approach as an alternative.

METHODS

Clinical data were reviewed in 9 patients presenting with anterolateral pontine cavernomas between 1999 and 2007.

RESULTS

All patients were treated via a presigmoid approach, which provided a nearly perpendicular trajectory to the anterolateral pons. The brainstem was entered through a "safe zone" between the trigeminal nerve and the facial/vestibulocochlear nerve complex. Complete resection was achieved in all cases. No patient experienced recurrent events during follow-up (1-24 months). The patients' modified Rankin Scale score improved within 1 year of surgery (1.7 ± 0.4) compared with baseline (2.6 ± 0.2; p < 0.05). Only one patient experienced a new deficit (decreased hearing), which was corrected with a hearing aid.

CONCLUSIONS

The presigmoid approach is recommended for the resection of anterolateral pontine cavernomas. With this approach, the need for cerebellar retraction is nearly eliminated. The lateral "presigmoid" entry point creates a trajectory that allows complete resection of even deep lesions at this level, or anterior to the internal acoustic meatus.

The extended retrosigmoid approach for neoplastic lesions in the posterior fossa: technique modification

Approaches to the cerebellar-pontine angle and petroclival region can be challenging due to intervening eloquent neurovascular structures and cerebellar retraction required to view this anatomic compartment with the standard retrosigmoid technique. As previously described [11], the extended retrosigmoid provides additional access to space ventral to the brainstem through mobilization of the sigmoid sinus. We report our further experience and modifications of this approach for neoplastic pathology. The standard craniotomy is utilized, and the burr holes are placed slightly beyond the transverse sinus as well as the transverse-sigmoid junction and down towards the foramen magnum, as low as possible. Another burr hole is placed over the cerebral hemisphere to facilitate the dural dissection below the bone flap and over the transverse and sigmoid sinuses. We then perform a standard retrosigmoid craniotomy with a craniotome and the transverse and sigmoid sinuses are skeletonized. Consequently, the sigmoid sinus can then mobilized anteriorly to provide an unobstructed view in line with the petrous bone, while exposure of the transverse sinus provides access to the tentorium. Fifteen patients (March 2006-July 2008) underwent this approach to manage neoplastic lesions, including five meningiomas, three schwannomas, one epidermoid, and four intra-axial metastatic lesions. The nine extra-axial lesions were predominantly in the cerebellar-pontine angle with extension medial to the seventh/eighth nerve complex to the petroclival region. Gross total resection was obtained in all patients. The primary complication due to the exposure was a clinically asymptomatic sigmoid sinus thrombosis in one patient. Requiring a fundamental change in the management of the venous sinuses, the extended retrosigmoid craniotomy permits mobilization of the sigmoid and transverse sinuses. In this process, the entire cerebellar-pontine angle extending from the tentorium to the foramen magnum can be visualized with minimal cerebellar retraction. This technical modification over the standard retrosigmoid approach may provide a useful advantage to neurosurgeons dealing with these complex lesions.

A surgical modification for performing orbitozygomatic osteotomies: technical note

The addition of orbitozygomatic osteotomies to the fronto-temporo-sphenoidal craniotomy minimizes brain retraction required to reach deep seated pathology by allowing additional soft tissue dissection and strategic cranial bone removal. We report a modification of this technique in order to reduce soft tissue and cosmetic morbidity while increasing the efficiency with which this technique is performed. A two piece fronto-temporo-sphenoidal craniotomy combined with orbitozygomatic osteotomies was analyzed via cadaver dissection. The craniotomy and orbitozygomatic osteotomies were performed using the foot plate of the craniotome to facilitate the orbitozygomatic osteotomies. A similar technique was utilized in the operating room to safely create the two piece fronto-temporo-sphenoidal craniotomy and orbitozygomatic osteotomies in a series of patients. The illustrated technique was performed in cadavers and the results were analyzed in a series of 18 consecutive patients with minimum 3-month follow-up. Increased efficiency, good tissue preservation, and minimal soft tissue damage with no orbital injury were noted with a high rate of gross total lesional resection. With the added safety of a cutting instrument separated from the orbital soft tissues by a footplate, tissue trauma was minimized. Orbitozygomatic osteotomies are frequently added to the fronto-temporo-sphenoidal craniotomy in order to reach intracranial pathology that would previously have required excessive brain retraction to address. This manuscript details the use of a single drill system that can be used for both the craniotomy and the safe and efficient generation of orbitozygomatic osteotomies.

Image-guided anatomical and morphometric study of supraorbital and transorbital minicraniotomies to the sellar and perisellar regions: comparison with standard techniques

OBJECT

Minimally invasive approaches have been proposed for the treatment of anterior cranial base pathology. Whereas earlier studies have quantified surgical exposure by referring to the opening on the surface, this cadaveric morphometric study redefines the concept of working area by examining the deep exposures afforded by several different approaches. Specifically, the authors systematically quantify and compare the operative exposure afforded by the pterional, supraorbital, and transorbital keyhole approaches to the sellar, suprasellar, and perisellar regions, including the anterior communicating artery complex.

METHODS

Pterional, supraorbital, and transorbital approaches were sequentially performed in 5 embalmed cadaveric heads on both sides. Preoperative and postoperative CT scans were obtained for frameless stereotactic navigation and measurements. Using reproducible anatomical landmarks, 6 triangles were defined to systematically measure the working area, depth of the surgical window, and angle of observation for each approach. Areas of the triangles were calculated using the Heron mathematical formula based on stereotactic navigation measurements. Ten sets of data were analyzed.

RESULTS

The pterional, supraorbital, and transorbital keyhole approaches provided progressively increasing working areas. The transorbital approach was associated with significantly increased exposure when compared with the pterional approach (p < 0.01). The transorbital approach was associated with a shallower depth of the surgical window when compared with either the supraorbital (p < 0.05) or pterional (p < 0.01) approach. The angle of basal view increased 56.6% with the transorbital approach (p < 0.001) when compared with the supraorbital approach. The transorbital route provided greater exposure on deeply located midline and contralateral structures.

CONCLUSIONS

In refining the concept of working area as deep rather than superficial in the surgical field, the authors quantified the 6 triangles whose boundaries were relative to the target structures to be exposed in the approach. The authors' morphometric findings support the use of the supraorbital and transorbital approaches as a valid alternative to the pterional approach for the treatment of sellar and perisellar pathology. The transorbital approach combines the advantages of minimal invasiveness with those of cranial base techniques.

Role of aneurysm projection in "A2" fork orientation for determining the side of surgical approach

PURPOSE

To determine factors that help decide the side of approach for anterior communicating artery (AComA) aneurysms, based on a prospective study.

METHODS

Between January 2004 and January 2006, 93 cases with AComA aneurysms were treated through pterional approach. They were classified as Type I, II (IIa, IIb), III and IV, based on the various projections and size of aneurysm. The principle for the choice of operative side was designed based on the type of aneurysm and the A2 fork orientation (the interrelations between the plane of bilateral A2, AComA, and mid-saggital plane).

RESULTS

There were 55 aneurysms of Type I, 10 of Type IIa, 14 of Type IIb, 12 of Type III, and 2 of Type IV. In Types I and IIa, the side posteriorly placed to A2 was chosen for the approach. In Type IIb, the side of the dominant A1 was selected. In Type III, the side anteriorly placed to A2 was chosen. Type IV aneurysms were difficult to handle even if approached from the dominant A1. There were 11 cases treated from the side of non-dominant A1. The overall outcome in the treatment of AComA aneurysms were considered excellent in 90.8% of cases according to the Glasgow Outcome Scale, with complete occlusion of aneurysms and complete patency of parent or perforating arteries.

CONCLUSIONS

Applying three-dimensional computed tomography and magnetic resonance angiography, we classified AComA aneurysms as four types and undertook surgical clipping from the chosen side of approach, according to the type of aneurysm and the A2 fork orientation. The selective side of approach on the basis of individual decision-making has led to favourable outcomes.

Cranio-orbital approach for complex aneurysmal surgery

Certain aneurysms of the anterior circulation continue to offer a technical challenge for safe exposure and clipping. The purpose of this paper was to describe the cranio-orbital approach for surgical clipping of complex aneurysms and to evaluate prospectively the associated complications of this approach. Prospective audit of all patients undergoing cranio-orbital approach for aneurysm surgery from 1997 to 2004 by the senior author. Twenty-five patients, eight male and 17 female, median age of 52 years, range 28-73. All patients had a standard pterional approach supplemented by an orbital osteotomy. In the 7-year period 367 patients underwent treatment for their aneurysms (169 clipped and 198 coiled). Of the 169 patients who were operated on, 29 had a skull base approach, of which 25 were cranio-orbital. The aneurysm location was as follows: 16 middle cerebral artery (MCA), three carotid bifurcation, four anterior communicating artery (ACOMM), one ophthalmic and one basilar. There were no approach-related complications. The cranio-orbital craniotomy can be a useful adjunct in the surgical treatment of giant or complex aneurysms. It offers the following advantages over a standard pterional approach: reduces operative distance; allows easy splitting of the sylvian fissure; and provides a wide arc of exposure with multiple working corridors.

The work horse of skull base surgery: orbitozygomatic approach. Technique, modifications, and applications

Object

The aim of this study was to describe the microsurgical anatomy of the orbitozygomatic craniotomy and its modifications, and detail the stepwise dissection of the temporalis fascia and muscle and explain the craniotomy techniques involved in these approaches.

Methods

Nine cadaveric embalmed heads injected with colored silicone were used to demonstrate a stepwise dissection of the 3 variations of orbitozygomatic craniotomy. The craniotomies and dissections were performed with standard surgical instruments, and the microsurgical anatomy was studied under microscopic magnification and illumination.

Results

The authors performed 2-piece, 1-piece, and supraorbital orbitozygomatic craniotomies in 3 cadaveric heads each. Stepwise dissection of the temporalis fascia and muscle, and osteotomy cuts were shown and the relevant microsurgical anatomy of the anterior and middle fossae was demonstrated in cadaveric heads. Surgical case examples were also presented to demonstrate the application of and indications for the orbitozygomatic approach.

Conclusions

The orbitozygomatic approach provides access to the anterior and middle cranial fossae as well as the deep sellar and basilar apex regions. Increased bone removal from the skull base obviates the need for vigorous brain retraction and offers an improved multiangled trajectory and shallower operative field. Modifications to the orbitozygomatic approach provide alternatives that can be tailored to particular lesions, enabling the surgeon to use the best technique in each individual case rather than a “one size fits all” approach.

Modified osteoplastic orbitozygomatic craniotomy in the pediatric population

OBJECT

Anterior and anterolateral skull base approaches offer the advantages of improved visualization and minimal brain retraction for lesions involving the orbital apex, parasellar regions, and anterior and middle fossa floors. These approaches are seldom used in the pediatric population due to the perceived increase in morbidity and surgical complexity. We report the application of the previously described modified osteoplastic orbitozygomatic (OZ) craniotomy to pediatric neurosurgical cases. This approach offers a number of advantages and is technically straightforward.

MATERIALS AND METHODS

The results from six pediatric cases are reported. Age ranged from 26 months to 15 years, with a follow-up period of 5 to 22 months. Pathology included craniopharyngioma (three), frontal epidural abscess-subdural empyema with intraorbital extension (one), hypothalamic hamartoma (one), and optic pathway glioma (one). No complications related to the surgical approach were noted. In all cases, good postoperative cosmesis was achieved with excellent realignment of the orbital rim. Temporalis muscle bulk was preserved and symmetric in all cases.

CONCLUSION

The modified osteoplastic OZ craniotomy can be safely and effectively applied to the pediatric population. Advantages include: (1) ease of use; (2) superior exposure and therefore less brain retraction; (3) an easily replaced one-piece bone flap which obviates the need for plating-suturing at the orbital rim; (4) a vascularized bone flap less susceptible to infection; and (5) maintenance of normal temporalis muscle anatomy for improved cosmesis and function.

Surgical management of giant intracranial aneurysms

OBJECTIVES

The natural history of giant intracranial aneurysms is generally morbid. Mortality and morbidity associated with giant aneurysms is also higher than for smaller aneurysms. This study was carried out to assess the demographic profile, presenting features, complications, and outcome after surgical treatment of giant intracranial aneurysms.

PATIENTS AND METHODS

A retrospective review of the medical records of all patients with giant intracranial aneurysms treated in the Department of Neurosurgery, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, from January 1995 through June 2007 was performed. The demographic profiles, presenting features, radiological findings, surgical treatments, and outcomes were assessed.

RESULTS

A total of 1412 patients harboring 1675 aneurysms were treated. Out of these, 222 patients had 229 (13.7%) giant aneurysms, and of those, 181 aneurysms in 177 patients were managed surgically while 48 were treated with endovascular therapy. In the patients treated with surgery, common clinical presentations included subarachnoid hemorrhage (SAH) in 110 (62%) cases followed by mass effect in 57 (32%) cases. In patients who presented with SAH, the Hunt and Hess SAH grading was: grade I in 43 (39%), grade II in 40 (36%), grade III in 23 (21%), grade IV in two (2%), and grade V in 2 (2%) patients. One hundred and seven aneurysms (in 103 patients) were treated using direct surgical clipping. Forty-six patients with good collateral circulation were treated by gradual occlusion and ligation of the internal carotid artery (ICA) in the neck with a Silverstone clamp. Another nine patients with good collateral circulation, but persisting symptoms after ICA ligation, required trapping for obliteration of the aneurysm. Eleven patients with poor collateral circulation required extracranial-intracranial (EC-IC) bypass before proximal ICA ligation. A post-operative digital subtraction angiography (DSA) was performed in 118 patients and revealed well-obliterated aneurysm in 106 patients. The total treatment mortality rate was 9%. In the last 5 years, 117 patients were operated on with four operative deaths. Overall, the outcome was excellent in 131 (74.0%), good in 22 (12.4%), and poor in eight (4.5%) cases.

CONCLUSIONS

It is concluded that 14% of all intracranial aneurysms are giant. The most common clinical presentation is SAH followed by features of an intracranial mass lesion. The cavernous ICA is the most common portion of the ICA affected. Direct surgical clipping is a safe and effective method of treatment and should be considered the first line of treatment whenever possible. With proper case selection, optimal radiological evaluation, and appropriate surgical strategy, it is possible to achieve a favorable outcome in almost 90% of the cases.

Image-Guided Lateral Suboccipital Approach: Part 2—Impact on Complication Rates and Operation Times

Objective:

Image-guidance systems are widely available for surgical planning and intraoperative navigation. Recently, three-dimensional volumetric image rendering technology that increasingly applies in navigation systems to assist neurosurgical planning, e.g., for cranial base approaches. However, there is no systematic clinical study available that focuses on the impact of this image-guidance technology on outcome parameters in suboccipital craniotomies.

Methods:

A total of 200 patients with pathologies located in the cerebellopontine angle were reviewed, 100 of whom underwent volumetric neuronavigation and 100 of whom underwent treatment without intraoperative image guidance. This retrospective study analyzed the impact of image guidance on complication rates (venous sinus injury, venous air embolism, postoperative morbidity caused by venous air embolism) and operation times for the lateral suboccipital craniotomies performed with the patient in the semi-sitting position.

Result:

This study demonstrated a 4% incidence of injury to the transverse-sigmoid sinus complex in the image-guided group compared with a 15% incidence in the non-image-guided group. Venous air embolisms were detected in 8% of the image-guided patients and in 19% of the non-image-guided patients. These differences in terms of complication rates were significant for both venous sinus injury and venous air embolism (P &lt; 0.05). There was no difference in postoperative morbidity secondary to venous air embolism between both groups. The mean time for craniotomy was 21 minutes in the image-guided group and 39 minutes in non-image-guided group (P = 0.036).

Conclusion:

Volumetric image guidance provides fast and reliable three-dimensional visualization of sinus anatomy in the posterior fossa, thereby significantly increasing speed and safety in lateral suboccipital approaches.

Microsurgical management of anterior communicating artery aneurysms

OBJECTIVE

Aneurysms of the anterior communicating (ACOM) artery are the most frequently occurring type of ruptured intracranial aneurysms. The peculiar anatomy of the anterior communicating artery complex, its anatomic variations, and its multiple perforators, along with the deep location of these aneurysms and our difficulty accessing them, pose challenging anatomic problems in their surgical treatment.

METHODS

We present our operative techniques for microsurgical treatment of ACOM artery aneurysms. Special, complex situations that may arise during treatment of these aneurysms and their solutions are also discussed. We highlight the technical aspects of microsurgical clipping of ACOM artery aneurysms.

RESULTS

Operative videos are provided to illustrate the technical variations of approaching and clipping these aneurysms, the A3-A3 bypass technique, and the complexity of managing these aneurysms.

CONCLUSION

Attention to detail is critical for successful treatment of ACOM artery aneurysms. Management of each patient must be tailored, because no one technique is suitable for all situations. Not all ACOM artery aneurysms can be coiled; therefore, the surgeon's microsurgical clipping technique is an important facet of managing these aneurysms.

Surgical planning for retrosigmoid craniotomies improved by 3D computed tomography venography

OBJECTIVE

It is impossible to precisely anticipate the crooked course of the transverse and sigmoid sinuses and their individual relationship to superficial landmarks such as the asterion during retrosigmoid approaches. This study was designed to evaluate this anatomical relationship with the help of a surgical planning system and to analyze the impact of these in vivo findings on trepanation placement in retrosigmoid craniotomies.

METHODS

In a consecutive series of 123 patients with pathologies located in the cerebellopontine angle, 72 patients underwent surgical planning for retrosigmoid craniotomies based on 3D volumetric renderings of computed tomography venography. By opacity modulation of surfaces in 3D images the position of the asterion was assessed in relationship to the transverse-sigmoid sinus transition (TST) and compared to its intraoperative localization. We evaluated the impact of this additional information on trepanation placement.

RESULTS

The spatial relationship of the asterion and the underlying TST complex could be identified and recorded in 66 out of 72 cases. In the remaining 6 cases the sutures were ossified and not visible in the 3D CT reconstructions. The asterion was located on top of the TST in 51 cases, above the TST in 4 cases, and below the TST in 11 cases. The location of the trepanation was modified in 27 cases due to the preoperative imaging findings with major and minor modifications in 10 and 17 cases, respectively.

CONCLUSION

Volume-rendered images provide reliable 3D visualization of complex and hidden anatomical structures in the posterior fossa and thereby increase the precision in retrosigmoid approaches.

Current Options in Clipping Versus Coiling of Intracranial Aneurysms: to Clip, to Coil, to Wait and Watch

Treatment of intracranial aneurysms involves many factors: patient preference and demographics; aneurysm size, site, geometry, access, and intrinsics; practitioner experience and availability; facility; technology; and ancillaries. Volume counts, teamwork enhancement, and management should be individualized.

One-piece versus two-piece orbitozygomatic craniotomy: quantitative and qualitative considerations

OBJECTIVE

The orbitozygomatic (OZ) craniotomy minimizes brain retraction and improves cranial base exposure by providing a multidirectional view, increased operative angles and working space. The two main variations of the approach include the one-piece and the two-piece types. The microsurgical anatomy of the one- and two-piece OZ craniotomies are presented with the goal of comparing the extent of orbital roof removal between these two craniotomies and the effect of orbital roof removal on operative exposure.

METHODS

Ten two-piece and 11 one-piece OZ craniotomies were performed in a stepwise manner simulating the approaches on formalin fixed specimens. The orbital surface area removed above the frontozygomatic suture extending medially over the orbital roof was measured from each bone flap. The two-sided unpaired t test using STATA 7.0 software was used to compare the amount of orbital roof removed using the two approaches.

RESULTS

The two-piece OZ craniotomy allowed for the removal of a larger portion of the roof and lateral wall of the orbit than the one-piece. The total orbitotomy, including the orbital roof plus the part of the lateral wall above the frontozygomatic suture, had an average surface area of 996 +/- 229 mm for the two piece and 372 +/- 103 mm for the one-piece. The orbital roof made up 27 +/- 18% of the orbital osteotomy for the one-piece craniotomies and 67 +/- 10% of the osteotomy for the two-piece craniotomies (P < 0.001).

CONCLUSION

The two-piece OZ craniotomy allows for more extensive orbital roof removal and better visualization of the basal frontal lobe. Therefore, the two-piece may result in a lower incidence of enophtalmus and poor cosmetic outcomes, particularly if the remaining orbital roof must be removed piecemeal during the one-piece OZ craniotomy in order to obtain satisfactory exposure.

The extended retrosigmoid approach: an alternative to radical cranial base approaches for posterior fossa lesions

OBJECTIVE

The extended retrosigmoid approach is presented as a simple and safe modification of the traditional retrosigmoid approach, with increased exposure resulting from a limited mastoidectomy and skeletonization of the sigmoid sinus.

METHODS

Patients with posterior fossa vascular lesions treated with the extended retrosigmoid approach between 1997 and 2003 were reviewed. A detailed description of the surgical approach, as well as case illustrations, is provided. We present a video narrated by the senior author in which a description of the technique is offered.

RESULTS

Thirty-eight patients underwent this approach to manage 40 lesions, including 15 dural arteriovenous fistulae, 9 arteriovenous malformations, 10 cavernous malformations, and 6 aneurysms. The extended retrosigmoid approach differs from the traditional approach with its C-shaped skin incision, posterior mastoidectomy, and extensive dissection of the sigmoid sinus, craniotomy rather than craniectomy, and anterior mobilization of the sinus with the dural flap.

CONCLUSION

The application of the extended retrosigmoid approach to a series of complex lesions in the posterior fossa demonstrates its applicability as an alternative to radical cranial base approaches. The extended retrosigmoid approach requires a fundamental change in the management of the sigmoid sinus. The neurosurgeon must be familiar with petrous bone anatomy, experienced dissecting through bone using a high-speed drill, and comfortable working directly over a major venous sinus. The technical modifications of the extended retrosigmoid approach can be incorporated into the neurosurgical repertoire and will enhance exposure of the cerebellopontine angle and deep vascular structures, thereby minimizing the need for brain retraction and other transpetrous approaches.

Quantitative anatomic study of three surgical approaches to the anterior communicating artery complex

OBJECTIVE

To compare the angles of approach and area of exposure to the anterior communicating artery (AComA) complex associated with pterional (PT), orbitopterional (OPT), and orbitozygomatic (OZ) craniotomies before and after gyrus rectus resection.

METHODS

PT, OPT, and OZ craniotomies were performed on both sides of four heads, and the angles of approach and area of exposure to the AComA complex were measured before and after resection of the gyrus rectus.

RESULTS

The vertical angle of approach increased significantly among the PT and OPT (P = 0.001), PT and OZ (P = 0.001), and OPT and OZ approaches (P = 0.005). The horizontal angle of approach was significantly larger between the PT to OPT (P = 0.001) and PT to OZ (P = 0.001) approaches but not between the OPT and OZ approaches (P = 0.757). After gyrus rectus resection, the vertical and horizontal angles of approach increased significantly for the PT approach but not for the OPT and OZ approaches. The area of exposure to the AComA complex increased progressively from the PT to OPT to OZ approach but did not reach statistical significance (P = 0.124). Resection of the gyrus rectus resulted in significant relative gains in the area of exposure for the PT (P = 0.01) and OPT (P = 0.04) approaches but not for the OZ approach (P = 0.88).

CONCLUSION

The vertical and horizontal angles of approach to the AComA complex are significantly larger for the OPT and OZ approaches compared with the PT approach. Use of the OZ approach may decrease the need for frontal lobe retraction and resection of the gyrus rectus.

Custom-tailored transdural anterior transpetrosal approach to ventral pons and retroclival regions

Object

The extradural anterior petrosectomy approach to the pons and midbasilar artery (mid-BA) has the main disadvantage that the extent of resection of the petrous apex cannot be as minimal as desired given that the surgical target field is not visible during bone removal. Unnecessary or excessive drilling poses the risk of injury to the internal carotid artery, vestibulocochlear organ, and seventh and eighth cranial nerves. The use of a custom-tailored transdural anterior transpetrosal approach can potentially avoid these pitfalls.

Methods

A technique for a transdural anterior petrosectomy was developed in the operating theater and anatomy laboratory. Following a subtemporal craniotomy and basal opening of the dura mater, the vein of Labbé is first identified and protected. Cerebrospinal fluid ([CSF] 50–100 ml) is drained via a spinal catheter. The tent is incised behind the entrance of the trochlear nerve toward the superior petrosal sinus (SPS), which is coagulated and divided. The dura is stripped from the petrous pyramid. Drilling starts at the petrous ridge and proceeds laterally and ventrally. The trigeminal nerve is unroofed. The internal acoustic meatus is identified and drilling is continued laterally as needed. The bone of the Kawase triangle toward the clivus can be removed down to the inferior petrosal sinus if necessary. Anterior exposure can be extended to the carotid artery if required. It is only exceptionally necessary to follow the greater superior petrosal nerve toward the geniculate ganglion and to expose the length of the internal acoustic canal.

The modified transdural anterior petrosectomy exposure has been used in nine patients—two with a mid-BA aneurysm, two with a dural arteriovenous fistula, one with a pontine glioma, three with a pontine cavernoma, and one with a pontine abscess. In one patient with a mid-BA aneurysm, subcutaneous CSF collection occurred during the postoperative period. No CSF fistula or approach-related cranial nerve deficit developed in any of these patients. There was no retraction injury or venous congestion of the temporal lobe nor any venous congestion due to the obliteration of the SPS or the petrosal vein.

Conclusions

The custom-made transdural anterior petrosectomy appears to be a feasible alternative to the formal extradural approach.

Fronto-orbital craniotomy reconstruction using the titanium clamp (Craniofix): a technical note

BACKGROUND

We evaluate a new technique for plateless fixation of a bone flap after fronto-orbital craniotomy.

METHODS

From September 1999 to October 2004, we performed fronto-orbital craniotomy reconstruction using the Craniofix titanium clamp in 108 consecutive patients with a variety of lesions in the anterior skull base. Postoperative computed tomographic imaging studies and clinical evaluations were performed to prospectively assess cosmetic conformity and bone flap stability and to evaluate the surgical benefit of Craniofix in these patients.

RESULTS

Excellent bone flap fixation and cosmetic results were obtained in all patients 6 to 68 months (average, 36 months) after surgery.

CONCLUSION

The Craniofix titanium clamp is a reliable, safe, and simple fixation device for reconstruction of fronto-orbital craniotomy.

Bypass Grafting and Revascularization in the Management of Posterior Circulation Aneurysms

OBJECTIVE:

To describe the bypass techniques, cranial base approaches, results of treatment, causes of failure, and lessons that are learned in patients with posterior circulation aneurysms requiring revascularization.

METHODS:

Retrospectively, 19 patients with posterior fossa aneurysms requiring revascularization procedures operated on between 1991 and 2002 were reviewed. Preoperative and postoperative clinical information, neurological examinations, imaging data, and updated follow-ups were reviewed. Patient outcome is reported as the most current Karnofsky Performance Scale score.

RESULTS:

A total of 22 arterial bypasses were performed in 19 patients for posterior fossa circulation aneurysms between 1991 and 2002. The mean follow-up was 41 months. Total graft patency rate (including patients requiring reoperation) was 86.4% (before) and 100% (after) salvage procedures. Patient outcome was 84.2% with Karnofsky Performance Scale score 80 to 90, and three deaths occurred perioperatively. Only one death could be attributed to the failure of the radial artery graft because of spasm and subsequent rupture during angioplasty.

CONCLUSION:

Certain graft selection criteria and technical considerations contribute to the success or failure of bypass grafts in the management of posterior circulation aneurysms. Bypass procedures remain an important method of management of complex posterior circulation aneurysms, in addition to endovascular procedures.

Anteroinferior Cerebellar Artery Aneurysms: Surgical Approaches and Outcomes—A Review of 34 Cases

OBJECTIVE:

Anteroinferior cerebellar artery (AICA) aneurysms are rare lesions whose treatment requires expertise in vascular, endovascular, and cranial base surgery. This article presents the largest series treated at one center.

METHODS:

We retrospectively analyzed presenting symptoms, aneurysm characteristics, surgical approaches, postoperative outcomes, and the application of endovascular techniques.

RESULTS:

We found 32 patients with 34 AICA aneurysms (11 men and 21 women; age range, 6–77 yr; mean age, 51 yr). Twenty-one aneurysms had ruptured; 13 were unruptured. Seven of the unruptured aneurysms presented with brainstem compression, and six were found incidentally. Surgical approaches included the retrosigmoid, far-lateral transcochlear, translabyrinthine, and orbitozygomatic. Eighteen patients (56%) had neurological complications. Thirty aneurysms were at proximal locations, and four were distal. Intraoperative hypothermic cardiac arrest was used to clip eight giant aneurysms. Follow-up was available in 56% of the patients for a mean of 41 months. The mean Glasgow Outcome Scale scores at discharge were not significantly different from the patients' status at their initial assessment.

CONCLUSION:

We recommend the standard retrosigmoid approach for treating small to medium aneurysms involving the lower two-thirds of the clivus or distal AICA aneurysms. Cranial base approaches are recommended for large or giant aneurysms or for those proximal to the emergence of the AICA from the basilar trunk. Hypothermic cardiac arrest facilitates dissection of giant aneurysms. Endovascular treatment is a useful adjunct for treating residual aneurysms but did not provide definitive treatment in any of our patients.