Contralateral pterional approach for carotid-ophthalmic aneurysm: usefulness of high resolution metrizamide or blood computed tomographic cisternography

The approach angle to the interoptic triangle limits surgical workspace when targeting the contralateral internal carotid artery

BACKGROUND

The interoptic triangle (IOT) offers a key access to the contralateral carotid artery's ophthalmic segment (oICA) and its perforating branches (PB), the ophthalmic artery (OA), and the superior hypophyseal artery (SHA). It has been previously reported that the assessment of IOT's size is relevant when attempting approaches to the contralateral oICA. However, previous studies have overseen that, since the oICA is a paramedian structure and a lateralized contralateral approach trajectory is then required, the real access to the oICA is further limited by the approach angle adopted by the surgeon with respect to the IOT's plane. For this reason, we determined the surgical accessibility to the contralateral oICA and its branches though the IOT by characterizing the morphometry of this triangle relative to the optimal contralateral approach angle.

METHODS

We defined the "relative interoptic triangle" (rIOT) as the two-dimensional projection of the IOT to the surgeon's view, when the microscope has been positioned with a certain angle with respect to the midline to allow the maximal contralateral oICA visualization. We correlated the surface of the rIOT to the visualization of oICA, OA, SHA, and PBs on 8 cadavers and 10 clinical datasets, using for the last a 3D-virtual reality system.

RESULTS

A larger rIOT correlated positively with the exposure of the contralateral oICA (R = 0.967, p < 0.001), OA (R = 0.92, p < 0.001), SHA (R = 0.917, p < 0.001), and the number of perforant vessels of the oICA visible (R = 0.862, p < 0.001). The exposed length of oICA, OA, SHA, and number PB observed increased as rIOT's surface enlarged. The correlation patterns observed by virtual 3D-planning matched the anatomical findings closely.

CONCLUSIONS

The exposure of contralateral oICA, OA, SHA, and PB directly correlates to rIOT's surface. Therefore, preoperative assessment of rIOT's surface is helpful when considering contralateral approaches to the oICA. A virtual 3D planning tool greatly facilitates this assessment.

Contralateral approach for the treatment of a distal supraclinoid aneurysm: a technical case report

Background: When treating intracranial aneurysms with open microsurgery, rare cases arise in which an ipsilateral approach leads to poor visualization, lack of proximal control, or potential damage to nearby vital structures due to the anatomy of the aneurysm. Case Description: We describe a patient with a small, unruptured aneurysm arising from the medial aspect of the distal supraclinoid internal carotid artery (ICA), just below the ICA bifurcation. A contralateral surgical approach was chosen because our view of the aneurysm from an ipsilateral approach would have been obstructed by the ICA. The contralateral approach provided excellent exposure of the aneurysm and allowed for precise clip placement without complications. Conclusions: Contralateral approaches may be a good option for some small medially pointing aneurysm of large proximal cerebral arteries.

Comprehensive Anatomic Assessment of Ipsilateral Pterional Versus Contralateral Subfrontal Approaches to the Internal Carotid Ophthalmic Segment: A Cadaveric Study and Three-Dimensional Simulation

OBJECTIVE

Medially pointing aneurysms of the ophthalmic segment of the internal carotid artery (oICA) represent a neurosurgical challenge. Conventional ipsilateral approaches require internal carotid artery and optic nerve (ON) mobilization as well as anterior clinoidectomy (AC), all associated with increased surgical risk. Contralateral approaches could provide a better exposure of the superomedial aspect of the oICA, ophthalmic artery, and superior hypophyseal artery, sparing AC and internal carotid artery or ON mobilization. However, the microsurgical anatomy of this approach has not been systematically studied. In the present work, we exhaustibly analyzed the anatomic and morphometric characteristics of contralateral approaches to the oICA and compared them with those from ipsilateral approaches.

METHODS

We assessed 36 ipsilateral and contralateral approaches to the oICAs in cadaveric specimens and live patients, using for the latter a three-dimensional virtual reality (VR) system.

RESULTS

Contralateral approaches spared sylvian fissure dissection and required only minimal frontal lobe retraction. The ipsilateral and contralateral oICA were found at a depth of 49.2 ± 1.8 mm (VR, 50.1 ± 2.92 mm) and 65.1 ± 1.5 mm (VR, 66.05 ± 3.364 mm) respectively. The exposure of the superomedial aspect of oICA was 7.25 ± 0.86 mm (VR: 6 ± 1 mm) contralaterally without ON mobilization and 2.44 ± 0.51 mm (VR, 2 ± 1 mm) ipsilaterally even after AC. Statistical analysis showed that, for nonprefixed chiasm, contralateral approaches achieved a significantly higher exposure of the ophthalmic artery, superior hypophyseal artery, and the superomedial aspect of the oICA with its perforating branches (all P < 0.01).

CONCLUSIONS

Contralateral approaches may enable successful exposure of the oICA and related vascular structures, reducing the need for AC or ON mobilization. Systematic clinical/surgical studies are needed to further determine the effectiveness and safety of the approach.

A literature review concerning contralateral approaches to paraclinoid internal carotid artery aneurysms

Ipsilateral approaches remain the standard technique for clipping paraclinoid aneurysms. Surgeons must however be prepared to deal with bony and neural structures restricting accessibility. The application of a contralateral approach has been proposed claiming that some structures in the region can be better exposed from this side. Yet, only few case series have been published evaluating this approach, and there is a lack of systematic reviews assessing its specific advantages and disadvantages. We performed a structured literature search and identified 19 relevant publications summarizing 138 paraclinoid aneurysms operated via a contralateral approach. Patient's age ranged from 19 to 79 years. Aneurysm size mainly varied between 2 and 10 mm and only three articles reported larger aneurysms. Most aneurysms were located at the origin of the ophthalmic artery, followed by the superior hypophyseal artery and carotid cave. All aneurysm protruded from the medial aspect of the carotid artery. Interestingly, minimal or even no optic nerve mobilization was required during exposure from the contralateral side. Strategies to achieve proximal control of the carotid artery were balloon occlusion and clinoid segment or cervical carotid exposure. Successful aneurysm occlusion was achieved in 135 cases, while 3 ophthalmic aneurysms had to be wrapped only. Complications including visual deterioration, CSF fistula, wound infection, vasospasm, artery dissection, infarction, and anosmia occurred in a low percentage of cases. We conclude that a contralateral approach can be effective and should be considered for clipping carefully selected cases of unruptured aneurysms arising from medial aspects of the above listed vessels.

Contralateral Transfalcine Versus Ipsilateral Anterior Interhemispheric Approach for Midline Arteriovenous Malformations: Surgical and Anatomical Assessment

BACKGROUND

The contralateral anterior interhemispheric approach (CAIA) is considered to provide surgical advantages to access deep midline lesions: wider working angle, gravity enhanced dissection and retraction, more efficient lighting, and ergonomics. Our team has previously published on the merits of using a contralateral trajectory for medial frontoparietal arteriovenous malformations (AVMs) compared with the conventional anterior interhemispheric approach (IAIA). In this article, we compare the IAIA and CAIA for the resection of medial frontoparietal AVMs using quantitative surgical and anatomical analysis.

METHODS

Two models were designed mimicking the most common features of midline AVMs. The CAIA and IAIA were performed bilaterally in 10 specimens. Variables to compare technical feasibility (surgical window [SW] and surgical freedom [SF], target exposure, and angle of attack) were independently assessed using stereotactic navigation. The average SW, SF, and angle of attack were compared with the Student t test. Significance threshold was set at 0.05.

RESULTS

The CITA and IAIA were similar in terms of SW, target exposure, and SF in the superior aspect of the AVM. In the depth of the interhemispheric fissure, the CAIA was significantly superior to IAIA in both AVM models: 77% wider AA for the inferior aspect of the AVM (P < 0.01) and greater SF for the draining vein (54%, P = 0.01), ipsilateral (98%, P = 0.02), and contralateral ACA (117%, P < 0.01).

CONCLUSIONS

This study suggests technical superiority of the CAIA for the resection of deep midline AVMs. No objective difference was noted in the superficial areas of our models, denoting that IAIA is a safer choice for superficial AVMs. Our results set the foundation for further clinical analysis comparing both approaches.

Development of Three-Dimensional Printed Craniocerebral Models for Simulated Neurosurgery

OBJECTIVE

To use three-dimensional (3D) printed craniocerebral models to guide neurosurgery and design the best operative route preoperatively.

METHODS

Computed tomography, magnetic resonance imaging, computed tomography angiography, and functional magnetic resonance images of the patients were collected as needed, reconstructed to form multicolor 3D craniocerebral images, and printed to form solid 3D models. The hollow aneurysm model was printed with rubberlike material; craniocerebral models were printed with resin or gypsum.

RESULTS

The 3D printed hollow aneurysm model was highly representative of what was observed during the surgery. The model had realistic texture and elasticity and was used for preoperative simulation of aneurysm clipping for clip selection, which was the same as was used during the surgery. The craniocerebral aneurysm model clearly showed the spatial relation between the aneurysm and surrounding tissues, which can be used to select the best surgical approach in the preoperative simulation, to evaluate the necessity of drilling the anterior clinoid process, and to determine the feasibility of using a contralateral approach. The craniocerebral tumor and anatomic model showed the spatial relation between tumor and intracranial vasculatures, tractus pyramidalis, and functional areas, which was helpful 1) when selecting the optimal surgical approach to avoid damage to brain function, 2) for learning the functional anatomy of the craniocerebral structure, and 3) for preoperative selection of surgical spaces in the sellar region.

CONCLUSIONS

3D printing provides neurosurgeons with solid craniocerebral models that can be observed and operated on directly and effectively, which further improves the accuracy of neurosurgeries.

Transient Cardiac Arrest Induced by Adenosine: A Tool for Contralateral Clipping of Internal Carotid Artery-Ophthalmic Segment Aneurysms

BACKGROUND

The disadvantages of a contralateral approach (CA) include deep and narrow surgical corridors and inconsistent ability to achieve proximal control of the supraclinoid internal carotid artery (ICA). However, a CA remains as a microsurgical option for selected ICA-ophthalmic (opht) segment aneurysms.

OBJECTIVE

To describe transient cardiac arrest induced by adenosine as an alternative tool to obtain proximal vascular control and soften the aneurysm sac in selected patients while performing a CA.

METHODS

From January 1998 to December 2013, we retrospectively identified 30 patients with ICA-opht segment aneurysms treated through a CA. Of those, 8 patients received an intravenous bolus of adenosine to induce transient cardiac arrest for softening of the aneurysm sac. We reviewed preoperative clinical status, characteristics of the contralateral aneurysm, adenosine doses, asystole time, recovery of normal circulation, outcome, and complications.

RESULTS

No preoperative cardiac or pulmonary pathologies were found in the study population. All contralateral ICA-opht segment aneurysms were unruptured, small, and saccular in shape. Transient cardiac arrest was induced because it was impossible to apply a temporary clip on the parent contralateral supraclinoid ICA. The median dose of adenosine was 22.5 mg (range, 5-50 mg) and the asystole time ranged from 20 to 40 seconds. All patients (n = 8) had good postoperative outcomes. No brain infarction or cardiac complications appeared postoperatively.

CONCLUSIONS

In selected patients, transient cardiac arrest induced by adenosine during a contralateral approach allows a brief flow arrest and softening of the aneurysm for safer exposure and clipping.

Contralateral Approach to Internal Carotid Artery Ophthalmic Segment Aneurysms: Angiographic Analysis and Surgical Results for 30 Patients

BACKGROUND

Contralateral aneurysm clipping can be applied to bilateral intracranial aneurysms of the anterior circulation and to selected aneurysms on the medial wall of the internal carotid artery (ICA).

OBJECTIVE

To identify anatomic and radiological parameters that would favor a contralateral microsurgical approach to ICA-ophthalmic segment (ICA-opht) aneurysms.

METHODS

For the period January 1957 to December 2012, we retrospectively analyzed 268 patients with ICA-opht aneurysms treated in our institution. Of these patients, 30 underwent a contralateral approach; 15 patients (50%) had multiple intracranial aneurysms, and 15 patients had a single aneurysm on the contralateral side of the craniotomy.

RESULTS

Thirty saccular aneurysms located on the contralateral ICA were treated. Six aneurysms (20%) were present in patients with a subarachnoid hemorrhage due to associated aneurysms, whereas 24 aneurysms (80%) had no history of bleeding. Contralateral aneurysms were smaller than 14 mm and showed no wall irregularities, calcifications, or secondary pouches. Projections of the aneurysms were superomedial (n = 23, 77%), medial (n = 4, 13%), and superior (n = 3, 10%). The median prechiasmatic distance was 5.7 mm (range, 3.4-8.7 mm), the median interoptic distance was 10.5 mm (range, 7.6-15.9 mm), and the median distance between both ICAs was 14.7 mm (range, 10.4-21.4 mm).

CONCLUSION

The contralateral approach for ICA-opht aneurysms remains a treatment option for intracranial aneurysms. Its feasibility depends on specific anatomic parameters related to the aneurysm itself and to the prechiasmatic distance, interoptic distance, and relationship of the ICA with the anterior clinoid process.

OLFACTORY DYSFUNCTION AFTER IPSILATERAL AND CONTRALATERAL PTERIONAL APPROACHES FOR CEREBRAL ANEURYSMS

OBJECTIVE

This study investigated olfactory dysfunction after using a contralateral or ipsilateral pterional approach for anterior circulation aneurysms and related risk factors.

METHODS

This study included 189 patients who experienced an aneurysmal subarachnoid hemorrhage and in whom a pterional approach was used, including a contralateral pterional approach (12 patients), a pterional approach for an anterior communicating artery (AComA) aneurysm (70 patients), and an ipsilateral pterional approach for aneurysms of the anterior circulation, excluding the AComA (107 patients). In addition to questionnaires on olfactory function, Sniffin' Sticks tests were performed 12 to 38 months after the operation.

RESULTS

The incidence of olfactory dysfunction was high: 58% (7 of 12) with a contralateral pterional approach, 14% (10 of 70) with a pterional approach for an AComA aneurysm, and 4% (4 of 107) with an ipsilateral pterional approach for aneurysms of the anterior circulation, except for the AComA. In addition, patients 55 years and older had a higher incidence of olfactory dysfunction. Among the 12 patients in whom the contralateral pterional approach was used, 5 (42%) were anosmic and 2 (17%) were hyposmic. The incidence of olfactory dysfunction was also significantly higher at ages 55 years and older. The size and location of the contralateral aneurysm, if small (&lt;1 cm) and located within a 3-cm lateral distance from the midline, were not found to influence the incidence.

CONCLUSION

A higher incidence of olfactory dysfunction was found in those patients in whom a contralateral pterional approach and a pterional approach for an AComA aneurysm were used. Another major risk factor was an age of 55 years and older.

Contralateral Approaches to Multiple Cerebral Aneurysms

NOT INFREQUENTLY, PATIENTS with bilateral cerebral aneurysms are encountered. In such patients, the ability to treat bilateral aneurysms through a unilateral approach spares the patient the risk and inconvenience associated with a separate craniotomy. The contralateral approach for aneurysm repair is technically feasible and safe in appropriately selected patients. Herein, we review our technique for maximizing contralateral exposure and clipping contralateral aneurysms through the four anatomic triangles that serve as corridors in this approach.

[Surgical treatment of múltiple intracraneal aneurysms]

INTRODUCTION

Surgical treatment of multiple intracranial aneurysms is always a complex task.

OBJECTIVE

To analyze aneurysms characteristics, therapeutic possibilities and surgical outcomes in a series of patients with multiple intracranial aneurysms.

PATIENTS AND METHOD

Among 514 patients with intracranial aneurysms, there were 113 with multiple aneurysms (21.5%) and 256 sacs: 244 located at the carotid system and 12 in the vertebrobasilar system. Patients were classified in three groups according to Orz criteria. Surgical treatment was performed in one or two stage operations. Patients were at I or II Grades of the World Federation Scale. The Glasgow Outcome Scale was used for evaluating surgical results.

RESULTS

Patients sacs rate was 2.3. The location of aneurysms was high in the posterior communicating artery and very low at the middle cerebral artery. 100% of the lesions in Orz group 1, 82% in group 2 and 33% in group 3 were operated on in one stage operation. Postoperative follow-up showed that 79 % of the patients made a completely recovery. Mortality rate was 4.4%.

CONCLUSIONS

Results were determined by the peculiar characteristics of this series, good preoperative condition and high proportion of one-stage operations.

Three-dimensional contrast medium-enhanced computed tomographic cisternography for preoperative evaluation of surgical anatomy of intradural paraclinoid aneurysms of the internal carotid artery: technical note

OBJECTIVE AND IMPORTANCE

Precise preoperative evaluation is especially important when internal carotid artery aneurysms in the paraclinoid region are clipped, because these vascular structures are located in close proximity to various important structures such as the optic nerve and anterior clinoid process. We report a new method for "simultaneously" describing the interrelationships among the aneurysm, internal carotid artery, optic nerve, and bony structures with three-dimensional contrast medium-enhanced computed tomographic (3-D CMECT) cisternography.

METHODS

Informed consent was obtained from the patient. An 8-ml injection of iotrolan (Isovist; Schering, Berlin, Germany) (240 mg I/ml) was administered into the lumbar intrathecal space. A computed tomographic scan of the head was obtained 2 hours later with a multislice Asteion computed tomographic scanner (Toshiba, Inc., Tokyo, Japan). An Alatoview workstation (Silicon Graphics, Mountain View, CA) was used to reconstruct the three-dimensional images.

RESULTS

These images, as generated by 3-D CMECT cisternography, were found to accurately demonstrate the interrelationships of the internal carotid artery, aneurysm, and surrounding structures preoperatively. The findings obtained from these images proved to be quite similar to the intraoperative findings. 3-D CMECT cisternography clarified whether the paraclinoid aneurysm was intradural or extradural.

CONCLUSION

3-D CMECT cisternography was found to provide a useful means for preoperative evaluation of lesions in the paraclinoid area.

Clinoid and paraclinoid aneurysms: surgical anatomy, operative techniques, and outcome

BACKGROUND

Paraclinoid or ophthalmic segment aneurysms arise from the internal carotid artery (ICA) between the roof of the cavernous sinus and the origin of the posterior communicating artery. Clinoid aneurysms arise between the proximal and distal carotid dural rings. The complex anatomy of clinoid and paraclinoid ICA aneurysms often makes them difficult to treat by microsurgery. The natural history of these aneurysms varies, based on their location and anatomic relationships. Accurate preoperative assessment of the origin of these aneurysms is therefore a critical aspect of their management.

METHODS

The authors reviewed 35 clinoid and paraclinoid ICA aneurysms operated in 28 patients and classify them according to their anatomic location and angiographic pattern. The operative techniques, surgical outcomes, and indications for surgery are reviewed.

RESULTS

Based on surgical anatomy and angiographic patterns, the aneurysms were classified into two categories: clinoid segment and paraclinoid (ophthalmic) segment. The clinoid segment aneurysms consisted of medial, lateral and anterior varieties. The paraclinoid aneurysms could be classified topographically into medial, posterior and anterior varieties, or based on the artery of origin into ophthalmic, superior, hypophyseal, and posterior paraclinoid aneurysms. Ophthalmic aneurysms were most common (40%), followed by posterior ICA wall aneurysms (29%), superior hypophyseal aneurysms (14%), and clinoid aneurysms (17%). Twenty patients (71%) had single aneurysms. Of the remaining eight, six had bilateral aneurysms and two had unilateral multiple aneurysms. Of the 35 aneurysms, 32 were clipped satisfactorily, as confirmed by intraoperative or postoperative angiography. One small broad-based aneurysm was wrapped, and two others were treated by trapping and bypass techniques. Three patients who had bilateral aneurysms underwent successful clipping of four contralateral, left-sided aneurysms via a right frontotemporal, transorbital approach. On follow-up (mean, 39 months), 25 patients were in excellent condition (returned to their prior occupation), two were in good condition (independent, but not working), and one died postoperatively of vasospasm.

CONCLUSION

Our increased knowledge of anatomy and refinements in operative techniques have greatly improved the surgical treatment of clinoid and paraclinoid aneurysms.

Contralateral approaches to bilateral cerebral aneurysms: a microsurgical anatomical study

In patients with bilateral supratentorial aneurysms, surgical clipping of all aneurysms via a unilateral approach would obviate the need for a second operation. The authors conducted a microsurgical study in human cadaver heads to examine the contralateral exposure for four common aneurysm sites in the anterior circulation: the ophthalmic artery (OA) origin, the posterior communicating artery (PCoA) origin, the internal carotid artery (ICA) termination, and the middle cerebral artery (MCA) bifurcation. Frontotemporal craniotomies were performed in 16 cadavers to evaluate the corridor for exposure of these sites from the contralateral side. Morphometric data, including lengths and diameters of major arterial segments and optic nerves, were documented for anatomical correlation. In this study, the contralateral OA origin was successfully exposed in 62% of specimens, the PCoA origin in 50%, the ICA bifurcation in 100%, and the MCA bifurcation in 62%. Exposure of the OA origin and, in some cases, the PCoA, required incision of the falciform ligament and mobilization of the contralateral optic nerve. Exposure of the MCA bifurcation was dependent on the length of the M1 segment, with successful exposure only when this segment was shorter than 14 mm. Implications for the contralateral approach to aneurysms at these sites are discussed and the microsurgical corridors for exposure are described. For correlation with the anatomical study, a brief clinical review of patients with bilateral supratentorial aneurysms treated at The Johns Hopkins Hospital between 1992 and 1995 is presented. Guidelines for the contralateral approach to aneurysms are discussed with reference to the anatomical study and the clinical review.

Brain edema after carotid surgery

The postoperative hyperperfusion syndrome describes an abrupt increase in blood flow with loss of autoregulation in surgically reperfused brain. Reports described a spectrum of findings, including severe headache, transient ischemia, seizures, and intracerebral hemorrhage. Hypertension is common after carotid artery surgery and often plays a role in the pathophysiology. We now report five patients with severe white matter edema after carotid surgery, a finding not previously included in the hyperperfusion syndrome. Five to 8 days after carotid surgery and after hospital discharge, each patient developed hypertension, headache, hemiparesis, seizures, and aphasia or neglect due to severe white matter edema ipsilateral to the carotid surgery. One patient had a small hemorrhage within the edematous area. Hypertension was severe in four patients and moderate in one. The carotid artery was patent by ultrasound or angiography in each patient after surgery. Transcranial Doppler showed increased velocities ipsilateral to surgery in two patients and bilaterally in one. Computed tomographic abnormalities and neurologic signs resolved within 3 weeks in four of the five patients treated with antihypertensives and anticonvulsants. The fifth patient died from herniation secondary to massive edema. Brain edema with focal neurologic signs should be included as a serious but potentially reversible component of the postoperative hyperperfusion syndrome.

Anatomical and technical aspects of the contralateral approach for multiple aneurysms

Microsurgery of multiple aneurysms is still a controversial subject. In order to avoid the risk of rebleeding and the consequent increase in morbidity in such cases all aneurysms or at least as many aneurysms as possible should be treated in the first operative procedure. To reach that goal aneurysms located on the contralateral side should also be considered for clipping during the first operation. Between 1984 and 1994 a series of 51 patients harboring multiple aneurysms of which 55 aneurysms were located on the contralateral side of the craniotomy were operated at our institution. No mortality or morbidity could be directly ascribed to the aneurysm that was clipped contralaterally. Based on that series we have described the anatomical features, technical aspects and surgical difficulties of approaching bilateral aneurysms through the same craniotomy.

Unilateral pterional approach to bilateral cerebral aneurysms

Between 1976 and 1991, we determined that 19 patients harboring bilateral supratentorial aneurysms should be approached in a single sitting through a unilateral pterional craniotomy. Using microsurgical techniques, the Sylvian cistern was opened widely to expose the aneurysms located ipsilateral to the craniotomy. These aneurysms were clipped in the usual fashion. Following clipping, a tunnel was developed over the contralateral anterior cerebral artery and over or under the contralateral optic nerve allowing access to the opposite carotid and middle cerebral arteries. The contralateral nonruptured aneurysms were clipped in a routine fashion. We were able to clip or wrap with muscle all bilateral aneurysms in 15 cases, and we have concluded that this approach can be safely employed in selected patients with bilateral supratentorial aneurysms, and thus a second craniotomy can be avoided.

"Subclinoid" carotid aneurysm with erosion of the anterior clinoid process and fatal intraoperative rupture

We present the case of a patient with an aneurysm of the right internal carotid artery with subarachnoid hemorrhage. The aneurysm had resulted in erosion of the anterior clinoid process, but this was not recognized preoperatively. Intraoperative rupture during drilling of the clinoid necessitated vigorous packing that led to unintended carotid occlusion with subsequent fatal cerebral infarction. Preoperative recognition of the clinoid erosion may have prevented this catastrophe. To call attention to the potential for intraoperative rupture during exposure, we suggest the term subclinoid aneurysm to refer to aneurysms of the internal carotid artery that grow superolaterally and remain confined under the anterior clinoid process.

[Multiple intracranial aneurysms]

Thirty eight patients with multiple intracranial aneurysms were studied. They correspond to 19.4% of all aneurysms treated over a twelve year period in the Servidores do Estado Hospital. 89 aneurysms and 4 infundibuli were detected. In 71.0% of the patients, two aneurysms were found; in 18.4%, three aneurysms; and in 10.4%, 4 or 5 aneurysms were observed. Twenty-seven patients were women and 11 men, ranging in age from 16 to 72 (average 47 years old). Subarachnoid hemorrhage was found in 36 patients (86.8%). The operative mortality in this series was 3.5%. We concluded that patients with multiple intracranial aneurysms should have all aneurysms, that can bleed, clipped through standard micro-neurosurgery technics.

Bifrontal interhemispheric approach for carotid-ophthalmic aneurysms

The authors report their experience with the surgical treatment of carotid-ophthalmic aneurysms in 29 cases, and describe their surgical technique. The technique can be summarized as follows. When dissecting the aneurysm, temporary vascular occlusion of the common carotid artery and external carotid artery is done in the neck under the administration of cerebral protective substances. Through a bifrontal craniotomy, wide dissection of the Sylvian fissures and the interhemispheric fissure is performed. When necessary, the anterior clinoid process and the roof of the optic canal are removed. This approach allows for observation of the neck of the aneurysm from various angles, thus facilitating clipping of the neck. There have been no previous reports of direct surgery on carotid-ophthalmic aneurysms using an interhemispheric approach, but this approach provides a much larger operative field and a better exposure of the aneurysm than other surgical approaches.

Microsurgical anatomy of the arteries of the pituitary stalk and gland as viewed from above

The microsurgical anatomy of the arteries of the pituitary stalk and gland as viewed from above was studied in 50 adult cadaveric hemispheres using the operating microscope. There were three types of vessels to the pituitary from above: the superior hypophyseal artery originating from the internal carotid artery, the infundibular artery from the posterior communicating artery, and the prechiasmal artery from the ophthalmic artery. The superior hypophyseal artery originated from the medial to posterior aspect of the internal carotid artery. The average number of vessels of the superior hypophyseal artery was 2.2 per hemisphere, and the diameter was 0.25 mm on average. The majority (76%) of superior hypophyseal arteries arose from the proximal half of the segment between the origins of the ophthalmic and posterior communicating arteries of the internal carotid artery. The infundibular artery originated mainly from the medial side (69%) of the posterior communicating artery. Its diameter was 0.22 mm, and number 0.23 per hemisphere. The number of prechiasmal arteries was 0.06 per hemisphere. As a result, there were on average 2.5 vessels per hemisphere, totally 5 per brain, with the average diameter 0.25 mm, supplying the pituitary stalk and gland from above. The clinical application of these anatomical data to the diagnosis and treatment of suprasellar tumours and carotid-ophthalmic aneurysms is discussed.

Microsurgical anatomy around the origin of the ophthalmic artery with reference to contralateral pterional surgical approach to the carotid-ophthalmic aneurysm

The supraclinoid segments of the internal carotid artery (ICA) and their surrounding structures were examined under magnification in 25 adult cadavers. Attention was paid to anatomical variations and relationships concerning ipsilateral and contralateral pterional microsurgical approaches to these regions, especially to the origin of the ophthalmic artery. Eighty-four percent of the ophthalmic arteries arose from the supraclinoid segment of the ICA. In the ipsilateral pterional approach, mobilization of the ipsilateral optic nerve was required to see the origin of the ipsilateral ophthalmic artery and the medial aspect of the proximal portion of the supraclinoid segment of the ICA. In the contralateral pterional approach, on the other hand, these areas on the contralateral side could be identified under the optic nerve with minimal or without retraction of the contralateral optic nerve. This was because 71% of the ophthalmic arteries arose from the supero-medial aspect of the ICA, and because there was nothing to intercept the view of the medial aspect of the ICA under the optic nerve. This study supports the usefulness of the contralateral pterional approach to the origin of the ophthalmic artery and the medial aspect of the supraclinoid segment of the ICA. This approach could be useful in certain cases of carotid-ophthalmic aneurysm. The authors' experience with the contralateral pterional approach to carotid-ophthalmic aneurysms is also described.