Cranial base approaches to intracranial aneurysms in the subarachnoid space

Modifications to the orbitozygomatic approach. Technical note

The orbitozygomatic craniotomy is one of the workhorse approaches of skull base surgery, providing wide, multidirectional access to the anterior and middle cranial fossae as well as the basilar apex. Complete removal of the orbitozygomatic bar increases the angles of exposure, decreases the working depth of the surgical field, and minimizes brain retraction. In many cases, however, only a portion of the exposure provided by the full orbitozygomatic approach is needed. Tailoring the extent of the bone resection to the specific lesion being treated can help lower approach-related morbidity while maintaining its advantages. The authors describe the technical details of the supraorbital and subtemporal modified orbitozygomatic approaches and discuss the surgical indications for their use. Modifications to the orbitozygomatic approach are an example of the ongoing adaptation of skull base procedures to general neurosurgical practice.

Anatomical basis of approaches to foramen magnum and lower clival meningiomas: comparison of retrosigmoid and transcondylar approaches

OBJECT

Meningiomas of the lower clivus and foramen magnum are among the most challenging of all neurosurgical lesions. Debate continues regarding the most appropriate approach to this eloquent anatomical region. This anatomical study was undertaken to measure and compare the area of surgical exposures of the lower clivus achieved using the retrosigmoid and the extreme-lateral transcondylar (ELT) approaches.

METHODS

Thirteen embalmed cadaveric heads were dissected bilaterally via the retrosigmoid approach on one side and the ELT approach on the other. The circumference of the area of exposure was delineated using beaded pins placed into the dura. After removal of the brain, the longest longitudinal and transverse axes of the pinned areas were measured and surface area calculated. The area of surgical exposure was also expressed as a percentage of the total area of the lower clivus. Normalized and adjusted surface areas were calculated using the bimastoid diameter. The areas of exposure were compared using the two-tailed paired Student t-test. The mean area of exposure required using the retrosigmoid approach was 19.8 +/- 14.7 mm2 (range 6-49 mm2) and that using the ELT approach was 27.8 +/- 22.8 mm2 (range 10-90 mm2). The mean percentage of the lower clivus exposed by the retrosigmoid approach was 14.9 +/- 3.6% (range 10-22%) and that exposed by the ELT approach was 20.5 +/- 4.9% (range 10-25%). The ELT approach provided significantly greater area of operative exposure and allowed a significantly higher percentage of lower clivus and foramen magnum exposure than did the retrosigmoid approach (p < 0.05). Normalized and adjusted surface areas, taking into consideration the bimastoid diameter, were also statistically significant in favor of the ELT approach.

CONCLUSIONS

The ELT approach provided a significantly greater area of exposure than did the retrosigmoid approach.

Anatomic and Clinical Study of the Orbitopterional Approach to Anterior Communicating Artery Aneurysms

OBJECTIVE

To evaluate the orbitopterional approach to anterior communicating artery (AComA) aneurysms, on the basis of the quantification of this surgical exposure, compared with the pterional approach, in a cadaveric study and a retrospective review of data for 40 patients who underwent clipping of AComA aneurysms via the orbitopterional approach.

METHODS

In an anatomic study, four cadaveric heads underwent pterional craniotomies on the left side and orbitopterional craniotomies on the right side. A fifth head was initially subjected to bilateral pterional craniotomies and then underwent bilateral orbital osteotomies, for direct comparison of these approaches. Using frameless stereotaxy, we quantified the angles of exposure and surgical field depths provided by the pterional and orbitopterional craniotomies. In a clinical study, 40 patients who underwent clipping of AComA aneurysms via orbitopterional approaches were evaluated for basal brain injury, the need for resection of the gyrus rectus, dissection of the sylvian fissure, and approach-related complications. The incidence of postoperative hydrocephalus among patients with subarachnoid hemorrhage who underwent lamina terminalis fenestration was also reviewed.

RESULTS

The angles of observation were increased 46% in the axial plane (orbitopterional, 72.92 ± 6.57 degrees; pterional, 49.75 ± 2.27 degrees; P&lt; 0.01) and 137.5% in the projection plane (orbitopterional, 8 ± 2.19 degrees; pterional, 19 ± 1.78 degrees; P&lt; 0.01). The surgical window depth was decreased 13% with the orbitopterional approach (P&lt; 0.05). Clinically, there was no incidence of frontobasal hypodensities on postoperative computed tomographic scans. Three patients (7.5%) required resection of the gyrus rectus. No patient required sylvian fissure dissection for aneurysm exposure. Two of 29 patients (6.9%) who survived subarachnoid hemorrhage required ventriculoperitoneal shunts despite lamina terminalis fenestration. No approach-related complications were recognized.

CONCLUSION

The orbitopterional approach improved the observation of the AComA complex and seemed to decrease the risk of intraoperative brain damage.

The One-Piece Orbitopterional Approach

The orbitopterional approach is an anterior skull base extension of the pterional approach that provides greater exposure to the anterior cranial fossa, supra- and parasellar regions, and anterior communicating artery complex. We describe the surgical technique in a stepwise manner to create a one-piece orbitopterional craniotomy flap; keyholes for the bone cuts are the MacCarty burr-hole and the anterolateral portion of the inferior orbital fissure. This one-piece technique is less complicated than the two-piece orbitopterional craniotomy and eliminates the need for complex reconstruction of cosmetically important areas (i.e., the orbit and forehead).

Osteotomy design and execution

Craniofacial osteotomies are an integral part of contemporary neurosurgery because of their ability to provide substantially more exposure to deepseated lesions with reduced brain retraction. A systematic approach to the performance of these osteotomies coupled with meticulous bone work capitalizes on their advantages without producing any significant cosmetic defects. As their indications are progressively more clearly defined and familiarity and facility are gained by the surgeons performing them, operative time and morbidity should decrease. Lowering operative time and morbidity with excellent esthetic results is likely to be increasingly important when considering operative versus nonoperative management, particularly as nonsurgical modalities continue to develop.

Progression of an arterial infundibulum to aneurysm: case report

In this case an aneurysm of the right posterior communicating artery developed 11 months after an infundibular dilation of this artery had been angiographycally and surgically demonstrated. In the best of the authors' knowledge, there are only eleven such cases reported in the literature. This report brings about diagnostic and therapeutic questions regarding arterial infundibula and the need of a better understanding of those lesions.

Presigmoid approach for cavernous angioma in the pons--technical note

Surgical treatment of brainstem lesions has been encouraged after the development of magnetic resonance imaging. However, direct approaches to intra-axial lesions in the brainstem still carry a high risk of morbidity because the neuronal structures can be injured along the entry routes. We present two patients whose pontine cavernous angiomas were removed via incision of the lateral aspect of the pons with presigmoid approach. The first case, a 41-year-old woman, presented with paresis of the cranial nerves VI, VII, and VIII, and left hemiparesis progressing over 2 weeks caused by a cavernous angioma ventrally located in the lower pons. The second case, a 50-year-old woman, developed dizziness over 2 months due to a large cavernous angioma in the center of the pons. These lesions were totally removed through the presigmoid approach and no additional neurological deficits were observed. An image-guided navigation system was used for the craniotomy and removal of the lesion in the second patient. The presigmoid approach provides a safe route to intra-axial lesions in the pons. A technique for presigmoid craniotomy with one-piece bone flap under the image-guided navigation is also described.

Transorbital keyhole approach to anterior communicating artery aneurysms

OBJECTIVE

The transorbital keyhole approach to anterior communicating artery aneurysms was developed as a minimally invasive method for safe control of the anterior communicating artery complex. This approach does not necessitate resection of the gyrus rectus.

METHODS

The technique is described in detail. The transorbital keyhole approach provides more ventral access than the supraorbital approaches, and the anterior communicating artery complex can be controlled by splitting the basal aspect of the interhemispheric fissure.

RESULTS

Since late 1998, the authors have used the transorbital keyhole approach routinely. During the initial experience with 33 patients, the only observed complication specific to this approach was transient diplopia in one patient. At follow-up examinations 2 to 15 months after surgery, the cosmetic results were favorable as compared with those of standard pterional craniotomy.

CONCLUSION

We have designed a small, custom-tailored approach to the anterior communicating artery complex for routine use. The small orbitocranial approach is a step toward the ideal of purely extra-axial safe control of anterior communicating artery aneurysms. The orbitocranial keyhole approach seems to be substantially better than the craniotomy, although it requires additional effort and time.

Quantitative description of the far-lateral transcondylar transtubercular approach to the foramen magnum and clivus

OBJECT

The purpose of this study was to evaluate the far-lateral transcondylar transtubercular approach (complete FLA) based on quantitative measurements of the exposure of the foramen magnum and petroclival area obtained after each successive step of this approach.

METHODS

The complete FLA was reproduced in eight specially prepared cadaveric heads (a total of 15 sides). The approach was divided into six steps: 1) C-1 hemilaminectomy and suboccipital craniectomy with unroofing of the sigmoid sinus (basic FLA); 2) partial resection of the occipital condyle (up to the hypoglossal canal); 3) removal of the jugular tuberculum; 4) mastoidectomy (limited to the labyrinth and the fallopian canal) and retraction of the sigmoid sinus; 5) resection of the lateral mass of C-1 with mobilization of the vertebral artery; and 6) resection of the remaining portion of the occipital condyle. After each successive step, a standard set of measurements was obtained using a frameless stereotactic device. The measurements were used to estimate two parameters: the size of the exposed petroclival area and the size of a spatial cone directed toward the anterior rim of the foramen magnum, which depicts the amount of surgical freedom available for manipulation of instruments. The initial basic FLA provided exposure of only 21 +/- 6% of the petroclival area that was exposed with the full, six-step maximally aggressive (complete) FLA. Likewise, only 18 +/- 9% of the final surgical freedom was obtained after the basic FLA was performed. Each subsequent step of the approach increased both petroclival exposure and surgical freedom. The most dramatic increase in petroclival exposure was noted after removal of the jugular tuberculum (71 +/- 12% of final exposure), whereas the least improvement in exposure occurred after the final step, which consisted of total condyle resection.

CONCLUSIONS

The complete FLA provides wide and sufficient exposure of the foramen magnum and lower to middle clivus. The complete FLA consists of several steps, each of which contributes to increasing petroclival exposure and surgical freedom. However, the FLA may be limited to the less aggressive steps, while still achieving significant exposure and surgical freedom. The choice of complete or basic FLA thus depends on the underlying pathological condition and the degree of exposure required for effective surgical treatment.

Quantification of increased exposure resulting from orbital rim and orbitozygomatic osteotomy via the frontotemporal transsylvian approach

OBJECT

Use of orbital rim and orbitozygomatic osteotomy has been extensively reported to increase exposure in neurosurgical procedures. However, there have been few attempts to quantify the extent of additional exposure gained by these maneuvers. Using a novel laboratory technique, the authors have attempted to measure the increase in the "area of exposure" that is gained by removal of the orbital rim and zygomatic arch via the frontotemporal transsylvian approach.

METHODS

The authors dissected five cadavers bilaterally. The area of exposure provided by the frontotemporal transsylvian approach was determined by using a frameless stereotactic device. With the tip of a microdissector placed on targets deep within the exposure, the position of the end of the microdissector handle was measured in three-dimensional space as the microdissector was rotated around the periphery of the operative field. This maneuver was performed via the frontotemporal approach alone as well as with orbital rim and orbitozygomatic osteotomy approaches. After data manipulation, the areas of exposure corresponding to the polygons used to define these handle positions were calculated and directly compared. On average, the area of exposure provided by the frontotemporal transsylvian approach was increased 26 to 39% (p<0.05) by adding orbital rim osteotomy and an additional 13 to 22% (not significant) with removal of the zygomatic arch.

CONCLUSIONS

Significant and consistent increases in surgical exposure were obtained by using orbital osteotomy, whereas zygomatic arch removal produced less consistent gains. Both maneuvers may be expected to improve surgical access. However, because larger and more consistent gains were afforded by orbital rim removal, the threshold for removal of this portion of the orbitozygomatic complex should be lower.

[An en bloc cranio-orbitozygomatic approach: surgical technique and results]

An en bloc cranio-orbitozygomatic approach is described. This technique was applied in seven patients (five basilar artery aneurysms, a trigeminal neuroma, a meningioma of the lesser sphenoid wing). The follow-up period ranged from 3 to 50 months. The patients were retrospectively analyzed from the cosmetic point of view, and submitted to computerized tomography with three dimensional and multiplanar reconstructions. The access provided a wider operative field with a shorter distance to the pathology and possibility of increased angulation of the microscope. The aneurysms could be clipped and the tumors completely removed in all cases. A frontalis muscle paralysis occurred in two cases, as well as a temporalis muscle atrophy in another two patients. There were no enophthalmos or bone flap displacements. The surgical technique is simple and do not require drills, electric saws and mini-plates.

[Three-dimensional computed tomographic angiography as preoperative examination in the treatment of cerebral aneurysms]

This study is based on 36 cases selected from the radiological clinic of the Free-University of Berlin and shows the advantages of spiral CT angiography over conventional cerebral angiography which provides only a few limited anatomical views: frontal, lateral and oblique. With CTA (computerized tomographic angiography) it is possible to obtain 360 degrees reformatted images in all directions getting large number of projections and showing the neck of aneurysms and its relation to vessels and the fundus in relation to the neck. CTA also depicts aneurysms in relation to bone or portions of it along the base of the skull. The CTA achieves so good sensibility as the cerebral angiography does and is used as preoperative examination for the cerebral aneurysms treatment.

Orbitozygomatic craniotomy. Technical note

The orbitozygomatic approach provides wide, multidirectional access to the anterior and middle cranial fossae, as well as to the upper third of the posterior fossa and clivus. The authors describe technical details of the surgical approach as it has evolved over 3.5 years of experience in 83 consecutive cases. This modified technique eliminates the need for bone reconstruction of the orbital walls to prevent enophthalmos and minimizes the risk of injury to the frontal branch of the facial nerve. At a follow-up evaluation after a period averaging 14 months, all patients were pleased with the cosmetic results of this approach.

Technical aspects and recent trends in the management of large and giant midbasilar artery aneurysms

OBJECTIVE

Cranial base approaches that involve radical petrosectomy are associated with significant rates of morbidity. We have sought alternative approaches to the midbasilar artery to reduce the extent of temporal bone removal and correspondingly to reduce complications while still providing adequate surgical exposure. The extended orbitozygomatic and far-lateral approaches are two such approaches. We compared our experience with these approaches to our experience with the standard transpetrosal approaches in the treatment of midbasilar artery aneurysms.

METHODS

Between 1990 and 1995, 28 patients with large and giant midbasilar artery aneurysms were treated with approaches involving either radical or conservative petrosectomy.

RESULTS

Overall, good outcomes (Glasgow Outcome Scale scores of 1 and 2) were observed in 21 patients (75%), and three patients (11%) had permanent treatment-associated neurological deficits. Four patients died. Later in the series, the pterional-subtemporal approach (four patients) was supplanted by the orbitozygomatic approach (six patients). The increased use of hypothermic circulatory arrest involved exposure of the midbasilar region from above (orbitozygomatic approach) and below (far-lateral approach, 13 patients). Concomitantly, the use of transpetrosal approaches (five patients) decreased.

CONCLUSION

Modified orbitozygomatic and far-lateral approaches adequately expose the midbasilar region and can replace transpetrosal approaches in some cases. These extended approaches can be associated with lower morbidity rates than can transpetrosal approaches. Hypothermic circulatory arrest is critical to clipping large and giant midbasilar artery aneurysms directly when approaches that conserve the temporal bone are used.

Three-dimensional computed tomographic angiography in detection of cerebral aneurysms in acute subarachnoid hemorrhage

OBJECTIVE

Three-dimensional computed tomographic angiography (CTA) is a recently developed imaging modality. We demonstrate the value of this noninvasive method in replacing digital subtraction angiography (DSA) in the detection of aneurysms of the circle of Willis in patients with subarachnoid hemorrhage admitted to our institution.

METHODS

A helical acquisition was performed for computed tomographic scans obtained for 120 patients with a 1 mm per second table speed and a 1-mm collimation, 1:1 pitch. Axial source images were transferred on a console Advantage Windows workstation (General Electric, Milwaukee, WI) and CTA was obtained using maximum intensity projection reconstruction. All patients had undergone DSA of the circle of Willis (80 patients preoperatively and 40 postoperatively).

RESULTS

A total of 129 aneurysms were detected in 107 patients. Three-dimensional CTA disclosed nothing abnormal in 13 patients. Ninety-two patients sustained one aneurysm, 10 patients sustained two, 3 patients sustained three, and 2 patients sustained four. All results were confirmed by DSA. In two cases, aneurysms of the middle cerebral artery were defected by CTA but not by DSA. When using angiographic views, the aneurysm was always masked by a branch of the middle cerebral artery.

CONCLUSION

The sensitivity of three-dimensional CTA is comparable with that of DSA, and its specificity is 100%. Because CTA is simple, quick, noninvasive, and reliable, we think that it can eventually replace DSA.

The effect of orbitozygomatic access for ruptured basilar and related aneurysms on management outcome

BACKGROUND

Despite increasing use of craniofacial access for complex intracranial and skull base pathology, there have been no reports detailing the impact of improved access on clinical outcome.

METHODS

Orbitozygomatic access was used in 32 patients with an aneurysm of the basilar bifurcation, superior cerebellar, or posterior cerebral arteries over a 9-year period.

RESULTS

Operative mortality was 0%, overall management mortality 9% and management morbidity was 9%. This approach was selected for these patients because of the anatomy of the aneurysm and its relationship to the terminal basilar complex and the dorsum sellae/posterior clinoid process. The flexibility achieved by the access allowed intraoperative use of multiple corridors of access. Morbidity directly attributable to the use of orbitozygomatic access was minimal.

CONCLUSIONS

While management outcome after aneurysmal subarachnoid hemorrhage relates directly to the severity of the initial hemorrhage, rather than the surgical approach chosen, in selected patients we recommend the use of this approach as a valuable adjunct to the armamentarium of the vascular neurosurgeon.

Aneurysms of the vertebro-basilar junction area: preliminary experience in endovascular and surgical management

Aneurysms of the vertebro-basilar junction area have been considered the most difficult to be surgically treated because of their deep location, the proximity of the brain stem and the cranial nerves. However, at present, new endovascular techniques and new transbasal surgical approaches offer valuable management strategies. This paper concerns six consecutive patients whom we managed either endovascularly or surgically during a period of eighteen months. Direct surgical treatment was offered to two young patients with relatively small aneurysms in good neurological condition, whereas the other four patients initially underwent an endovascular attempt at aneurysm obliteration using the Guglielmi detachable coil system. Unfortunately, interventional neuroradiology failed in three cases, and surgery had to be re-considered. Accordingly, a total of five patients underwent surgical clipping through the combination of a transmastoid retrolabyrinthine approach with the suboccipital lateral approach. This combination of approaches provided a good control of both vertebral arteries and basilar artery, and allowed the aneurysm to be correctly clipped in all cases. Good long-term results were achieved in all cases but one. Based on this preliminary experience, we would stress the importance of multidisciplinary approach with a treatment calibrated for each single case. Furthermore, if surgery is to be performed, the combination of transmastoid-retrolabyrinthine and suboccipital lateral approaches provides a wide exposure of the whole vertebro-basilar junction area and allows good access to the lesion.

A surgical technique to avoid postoperative enophthalmos in the cranioorbital approach. Technical note

The authors describe a surgical technique to avoid postoperative enophthalmos when using the cranioorbital approach. To perform osteotomies with a less demanding technique, two separate bone flaps were created: 1) a free frontotemporal bone flap and 2) en bloc removal of the superior and lateral orbital rims: Because the latter bone flap includes both the orbital roof and the posterolateral wall of the orbit with the greater wing of the sphenoid bone, unnecessary bone defects in the lateral orbital wall are avoided. The technique has been performed in seven patients treated for medially located skull base neoplasms or complex anterior circulation aneurysms without postoperative enophthalmos or other cosmetic problems. The authors believe this cranioorbital approach, with its simpler, less invasive surgical technique, offers a definite advantage by avoiding postoperative enophthalmos.

Posterior transpetrosal approach to aneurysms of the basilar trunk and vertebrobasilar junction

Aneurysms of the basilar trunk and vertebrobasilar junction represent an exceptional challenge to the neurosurgeon. Surgical access to these deep and confined lesions is hampered by the direct proximity of highly vulnerable neural structures such as the brainstem and cranial nerves, as well as by the structure of the petrous bone, which blocks direct surgical approach to these aneurysms. A number of surgical tactics consisting of different supra- and infratentorial approaches have been applied over the years to gain access to these treacherous lesions. Only recently have lateral approaches, such as the anterior transpetrosal, the retrolabyrinthine-transsigmoidal, and the combined supra/infratentorial-posterior transpetrosal approaches, directed through parts of the petrous bone, been reported for surgery of basilar trunk and vertebrobasilar junction aneurysms. Because detailed reports of direct operative intervention using the transpetrosal route for these rare and difficult lesions are scarce, the authors present their surgical experiences in nine patients with basilar trunk and vertebrobasilar junction aneurysms, in whom they operated via the supra/infratentorial-posterior transpetrosal approach. In eight patients, including one with a giant partially thrombosed basilar trunk aneurysm, direct clipping of the aneurysm via the transpetrosal route was possible. In one patient with a giant vertebrobasilar junction aneurysm, the completely calcified aneurysm sac was resected after occlusion of the vertebral artery. In total, one patient died and another experienced postoperative accentuation of preexisting cranial nerve deficits. Two patients had transient cerebrospinal fluid leakage, and the postoperative course was uneventful in the remaining seven. Postoperative angiography demonstrated complete aneurysm clipping in eight patients and relief of preoperative brainstem compression in the patient with the giant vertebrobasilar junction aneurysm. It is concluded that the supra/infratentorial-posterior transpetrosal approach allows excellent access to the basilar artery trunk and vertebrobasilar junction and can be considered the approach of choice to selected aneurysms located in this area.

Overall management outcome of ruptured posterior fossa aneurysms

A study of the overall management of ruptured posterior fossa aneurysms was conducted over a 1-year period (1993) in five neurosurgical centers in Sweden, serving a population of 6.93 million people. Forty-nine cases were identified and treated. One-third of the patients were in the seventh or eighth decade of life. Good overall management outcomes at 6 months were achieved in 30 cases (61%). The overall mortality rate was 27%. Patients with Hunt and Hess Grades I and II had a good overall recovery rate of 87%. On admission, 69% of the patients were assigned Hunt and Hess Grades III to V. The impact on patient outcomes of the intraoperative difficulties encountered, especially in the basilar tip area, is stressed. The authors found that delayed operation is not warranted in most cases. Frequent devastating rebleeding was observed among patients not offered early aneurysm clipping and the operative results were not at significant variance between the early and late surgical groups. Only 50% of the patients scheduled for delayed surgery ultimately made a good recovery, whereas 72% of patients scheduled for early operation did so. The data demonstrate that overall management results with posterior fossa aneurysms, comparable to achievements with supratentorial lesions, are within the reach of modern strategies, even in centers not specializing in these problems.

Treatment of aneurysms by excision or trapping with arterial reimplantation or interpositional grafting. Report of three cases

The authors report three cases of ruptured, large or giant aneurysms that were treated by excision or trapping, followed by revascularization of distal vessels by means of arterial reimplantation or superficial temporal artery interpositional grafting. In the first case, a large serpentine aneurysm arising from the anterior temporal branch of the right middle cerebral artery (MCA) was excised and the distal segment of the anterior temporal artery was reimplanted into one of the branches of the MCA. In the second case, a giant aneurysm, fusiform in shape, arose from the rolandic branch of the MCA. This aneurysm was totally excised and the M3 branch in which it had been contained was reconstructed with an arterial interpositional graft. In the third case the patient, who presented with a subarachnoid hemorrhage, had a dissecting aneurysm that involved the distal portion of the left vertebral artery. In this case the posterior inferior cerebellar artery (PICA) arose from the wall of the aneurysm and coursed onward to supply the brainstem. This aneurysm was managed by trapping and the PICA was reimplanted into the ipsilateral large anterior inferior cerebellar artery. None of the patients suffered a postoperative stroke and all recovered to a good or excellent postoperative condition. These techniques allowed complete isolation of the aneurysm from the normal blood circulation and preserved the blood flow through the distal vessel that came out of the aneurysm. These techniques should be considered as alternatives when traditional means of cerebral revascularization are not feasible.

The role of computed tomographic angiography in the diagnosis of intracranial aneurysms and emergent aneurysm clipping

Conventional cerebral angiography has always been regarded as the gold standard for intracranial aneurysm detection. However, conventional angiography has the disadvantages of being invasive and time consuming. We present here 30 patients who underwent computed tomographic angiography (CTA) with three-dimensional reconstruction for the detection of intracranial aneurysms. All of these patients had subarachnoid hemorrhage or suspected intracranial aneurysms. CTA was performed in all patients with the use of a General Electric Hispeed Advantage helical scanner. Iohexol, 135 ml, was used as the contrast agent. Twenty-five patients also underwent conventional angiography for comparison. The five patients who underwent CTA only did not have conventional angiography because of poor clinical condition, and four of them subsequently died. Five patients had subarachnoid hemorrhage, but the results of both CTA and conventional angiography were negative for aneurysms. One patient had an incidental finding of a 3-mm left posterior communicating artery aneurysm on CTA, which was confirmed by conventional angiography. In the remaining 19 patients, 19 saccular aneurysms and 1 fusiform aneurysm were detected by CTA. Locations and sizes were confirmed by conventional angiography in all except two. The first exception was a patient who had a 2.5-mm anterior communicating artery aneurysm detected by CTA but not by conventional angiography. Surgical exploration confirmed the CTA diagnosis. The other exception was a patient in whom a 2-mm right posterior communicating artery aneurysm was detected by CTA but in whom conventional angiography showed a 2-mm left posterior communicating artery aneurysm. Unfortunately, there was no surgical confirmation in this case because the family of the patient refused surgery. Our results have demonstrated that CTA is a quick, reliable, and relatively simple diagnostic tool for intracranial aneurysms. In an emergent situation, such as a deteriorating patient with a hematoma, it is superior to either empiric exploration or infusion computed tomographic scans because it delineates the orientation and configuration of the aneurysm and its associated vascular anatomy.

Cranio-orbital approach for the paraclinoidal and anterior communicating aneurysms

Aneurysms arising at the proximal intracranial carotid artery (between cavernous sinus and posterior communicating artery) and at the anterior communicating complex may present with technical difficulties regarding appropriate access without excessive brain retraction. In a series of 15 patients the authors show the use of the cranio-orbital approach, formerly designed in the access of skull base tumors, for these subgroups of aneurysms. They discuss the advantages of a basal avenue in minimizing brain retraction, better anatomical orientation, obviation of tissue ressection and easier extra-dural bone removal. It was not identified any complication due to the described approach.