Aneurysms of the ophthalmic segment. A clinical and anatomical analysis

The "no-drill" technique of anterior clinoidectomy: a cranial base approach to the paraclinoid and parasellar region

INTRODUCTION

A high-speed power-drilling technique of anterior clinoidectomy has been advocated in all publications on paraclinoid region surgery. The entire shaft of the power drill is exposed in the operative field; thus, all neurovascular structures in proximity to any portion of the full length of the rotating drill bit are at risk for direct mechanical and/or thermal injury. Ultrasonic bone removal has recently been developed to mitigate the potential complications of the traditional power-drilling technique of anterior clinoidectomy. However, ultrasound-related cranial neuropathies are recognized complications of its use, as well as the increased cost of device acquisition and maintenance.

METHODS

A retrospective review of a cerebrovascular/cranial base fellowship-trained neurosurgeon's 45 consecutive cases of anterior clinoidectomy using the "no-drill" technique is presented. Clinical indications have been primarily small to giant aneurysms of the proximal internal carotid artery; however, in addition to ophthalmic segment aneurysms, selected internal carotid artery-posterior communicating artery aneurysms and internal carotid artery bifurcation aneurysms, and other large/giant/complex anterior circulation aneurysms, this surgical series of "no-drill" anterior clinoidectomy includes tuberculum sellae meningiomas, clinoidal meningiomas, cavernous sinus lesions, pituitary macroadenomas with significant suprasellar extension, other perichiasmal lesions (sarcoid), and fibrous dysplasia. A bony opening is made in the mid-to posterior orbital roof after the initial pterional craniotomy. Periorbita is dissected off the bone from inside the orbital compartment. Subsequent piecemeal resection of the medial sphenoid wing, anterior clinoid process, optic canal roof, and optic strut is performed with bone rongeurs of various sizes via the bony window made in the orbital roof.

RESULTS

No power drilling was used in this surgical series of anterior clinoidectomies. Optimal microsurgical exposure was obtained in all cases to facilitate complete aneurysm clippings and lesionectomies. There were no cases of direct injury to surrounding neurovascular structures from the use of the "no-drill" technique. The surgical technique is presented with illustrative clinical cases and intraoperative photographs, demonstrating the range of applications in anterior and central cranial base neurosurgery.

CONCLUSION

Power drilling is generally not necessary for removal of the anterior clinoid process, optic canal roof, and optic strut. Rigorous study of preoperative computed tomographic scans/computed tomographic angiography scans, magnetic resonance imaging scans, and angiograms is essential to identify important anatomic relationships between the anterior clinoid process, optic strut, optic canal roof, and neighboring neurovascular structures. The "no-drill" technique eliminates the risks of direct power-drilling mechanical/ thermal injury and the risks of ultrasound-associated cranial neuropathies. The "no-drill" technique provides a direct, time-efficient, and efficacious approach to the paraclinoid/ parasellar/pericavernous area, using a simplified mechanical route. This technique is applicable to any neurosurgical diagnosis and approach in which anterior clinoidectomy is necessary. It is arguably the gentlest and most efficient method for exposing the paraclinoid/parasellar/pericavernous region.

RESULTS, OUTCOMES, AND FOLLOW-UP OF REMNANTS IN THE TREATMENT OF OPHTHALMIC ANEURYSMS

OBJECTIVE

Ophthalmic aneurysms present unique challenges to a vascular team. This study reviews the 16-year experience of a multidisciplinary neurovascular service in the treatment, complications, outcomes, and follow-up of patients with ophthalmic aneurysms from 1990 to 2005.

METHODS

A retrospective analysis of prospectively collected data of 134 patients with 157 ophthalmic aneurysms is presented. Subgroup analysis is performed based on treatment and clinical presentation of the patients.

RESULTS

Clinical outcomes are reported using the Glasgow Outcome Scale. A “good” outcome is defined as a Glasgow Outcome Scale score of 4 or 5, and a “poor” outcome is defined as a Glasgow Outcome Scale score of 1 to 3. Outcome was related to patient age (P = 0.0002) and aneurysm size (P = 0.046). Outcomes for patients with ruptured aneurysms were related to hypertension (P < 0.0001) and clinical admission grade (P = 0.001). In patients with unruptured aneurysms, a good clinical outcome was noted in 103 (92.7%) of 111 patients at discharge and 83 (94.3%) of 88 patients at the time of the 1-year follow-up evaluation. Complete clipping was attained in 89 (79.5%) of 112 patients with angiographic follow-up. Patients with aneurysm remnants from both coiling and clipping had a low risk of regrowth, and there were no rehemorrhages. One of 25 patients with angiographic follow-up (average, 4.3 ± 4.1 years) after “complete” clipping showed recurrence of the aneurysm.

CONCLUSION

Despite the difficulties presented by ophthalmic aneurysms, these lesions can be successfully managed by a multidisciplinary team. Imaging follow-up of patients is important, as there is a risk of aneurysm regrowth after either coiling or clipping.

Clinical and radiogical outcomes of endovascular detachable coil embolization in paraclinoid aneurysms : a 10-year experience

OBJECTIVE

Direct surgical clipping of paraclinoid aneurysms poses technical challenges to even very experienced neurosurgeons, making endovascular treatment an alternative treatment modality in many centers. We have therefore retrospectively evaluated the safety and efficacy of endovascular detachable coil embolization of paraclinoid aneurysms.

METHODS

From June 1997 to June 2007, 65 patients underwent endovascular detachable coiling for 67 paraclinoid aneurysms (of which 9 were ruptured and 58 were unruptured) in our institute. Their medical records, radiological images and readings, and operation records were reviewed retrospectively.

RESULTS

After the initial embolization procedure, complete occlusion was achieved in 29 (43.3%) of the aneurysms treated by endovascular detachable coiling. Six aneurysms required retreatment, with two each requiring one, two, or three additional endovascular procedures. Fifty-five (82.1%) aneurysms were measured by three-dimensional time of flight (TOF) magnetic resonance images (MRI) or transfemoral cerebral angiography (TFCA) at a mean follow-up of 29.7 months (range from 4 to 94 months), with 39 aneurysms (70.9%) showing complete occlusion. Thromboembolic events (3.8%) were the most frequent complication. Rupture did not occur during or after any of the procedures. According to the Glasgow Outcome Scale (GOS), 98.4% of the patients treated by coil embolization had a score of 4 or 5.

CONCLUSION

Our results indicate that endovascular detachable coiling is a safe and effective treatment modality in paraclinoid aneurysms.

Segregated hemispheric pathways through the optic chiasm distinguish primates from rodents

At the optic chiasm retinal fibers either cross the midline, or remain uncrossed. Here we trace hemispheric pathways through the marmoset chiasm and show that fibers from the lateral optic nerve pass directly toward the ipsilateral optic tract without any significant change in fiber order and without approaching the midline, while those from medial regions of the nerve decussate directly. Anterograde labeling from one eye shows that the two hemispheric pathways remain segregated through the proximal nerve and chiasm with the uncrossed confined laterally. Retrograde labeling from the optic tract confirms this. This clearly demonstrates that hemispheric pathways are segregated through the primate chiasm. Previous chiasmatic studies have been undertaken mainly on rodents and ferrets. In these species there is a major change in fiber order pre-chiasmatically, where crossed and uncrossed fibers mix, reflecting their embryological history when all fibers approach the midline prior to their commitment to innervate either hemisphere. This pattern was thought to be common to placental mammals. In marsupials there is no change in fiber order and uncrossed fibers remain confined laterally through nerve and chiasm, again, reflecting their developmental history when all uncrossed fibers avoid the midline. Recently it has been shown that this distinction is not a true dichotomy between placental mammals and marsupials, as fiber order in tree shrews and humans mirrors the marsupial pattern. Architectural differences in the mature chiasm probably reflect different developmental mechanisms regulating pathway choice. Our results therefore suggest that both the organization and development of the primate optic chiasm differ markedly from that revealed in rodents and carnivores.

Long-term surgical results with aneurysms involving the ophthalmic segment of the carotid artery

Object

Because of the anatomical complexity of the paraclinoid region, the surgical treatment of aneurysms arising in the C6 segment of the internal carotid artery is extremely challenging. The authors' aim in this study was to describe the extended clinical follow-up and assess the short-term and long-term effectiveness of surgical treatment for these aneurysms, focusing on the clinical outcome and degree of aneurysm occlusion and recurrence.

Methods

The authors retrospectively analyzed the clinical records for patients treated surgically between 1973 and 2004 at the University of Rome, “La Sapienza.” Aneurysms were classified into the following 3 groups according to the site where they arose: the anteromedial, anterior or anterolateral, and posteromedial wall of the C6 segment.

Results

Of the 108 aneurysms in 104 patients treated, 63 (58%) were large or giant. Eighty-eight aneurysms in 84 patients were clipped, 16 underwent a high-flow bypass, 2 were trapped, 1 was wrapped, and 1 was left untreated. The mean follow-up was 126 months; 47 patients had a follow-up of > 10 years. Of the 88 aneurysms that were clipped, 6 (6.8%) had an incomplete occlusion that required an immediate reoperation in 1 case and at 2 years in another. Overall 6 patients (5.8%) had surgery-related permanent complications.

Conclusions

Mortality and morbidity rates depend mainly on the patient's preoperative Hunt and Hess grade subarachnoid hemorrhage, whereas surgical morbidity principally reflects excessive manipulation of the optic nerve or ischemic problems due to excessive temporary trapping undertaken without adequate neuroprotection. In expert hands, surgery (clipping and bypass procedures) is a definitive treatment for C6 aneurysms and has an acceptable complication rate.

Refinement of the extradural anterior clinoidectomy: surgical anatomy of the orbitotemporal periosteal fold

OBJECTIVE

Extradural removal of the anterior clinoid process is technically challenging because of the limited exposure. In our study of the extradural anterior clinoidectomy, we describe anatomic details and landmarks to facilitate sectioning of the orbitotemporal periosteal fold and elevation of the temporal fossa dura from the superior orbital fissure. We assess the morbidity associated with these procedures as well as compare the indications, advantages, and disadvantages of intra-versus extradural clinoidectomy.

METHODS

Of five formalin-fixed cadaveric heads, four were used for cadaveric dissections and one was used for histological examination.

RESULTS

Sectioning of the orbitotemporal periosteal fold revealed a cleavage plane between the temporal fossa dura and a thin layer of connective tissue that covers the superior orbital fissure. The lacrimal nerve coursed immediately medial to this surgically created cleavage plane. The superior orbital vein crossed laterally under the cranial nerves, which pass through the superior orbital fissure. This vein is particularly vulnerable as it is composed only of endothelium and a basal membrane.

CONCLUSION

Both intra- and extradural techniques for anterior clinoidectomy are important parts of the neurosurgical armamentarium. Sharp incision of the orbitotemporal periosteal fold to increase the extradural exposure of the anterior clinoid process should be made at the level of the sphenoid ridge and restricted to the periosteal bridge. Subsequent blunt elevation of the temporal fossa dura should be performed; however, peeling of the temporal fossa dura should be limited to avoid cranial nerve morbidity.

Endoscopic endonasal clipping of an unsecured superior hypophyseal artery aneurysm

✓Paraclinoidal aneurysms, especially superior hypophyseal artery (SHA) aneurysms (with medial projection), can be challenging to access via a pterional craniotomy and damage to the optic nerve can occur during surgery. The authors have previously reported on endonasal clipping and aneurysmorrhaphy of a vertebral artery aneurysm following proximal and distal protection of the aneurysm using partial coil embolization. To the best of the authors' knowledge no unprotected aneurysm has been clipped using an endonasal approach.

The 56-year-old woman in this report was found to have two unruptured aneurysms: an anterior communicating artery (ACoA) aneurysm and an SHA aneurysm. An endoscopic endonasal, transplanar–transsellar approach was used to successfully clip the SHA aneurysm. Proximal and distal control was obtained endonasally prior to successful clip occlusion of the aneurysm. The ACoA aneurysm was clipped via a pterional craniotomy during the same anesthetic session. This report shows that it is possible to successfully clip a medially projecting, paraclinoidal aneurysm using an endonasal approach. Such cases must be chosen with extreme caution and only performed by surgeons with significant experience with both endoscopic endonasal approaches and neurovascular surgery.

Usefulness of MR imaging for the assessment of nonophthalmic paraclinoid aneurysms

BACKGROUND AND PURPOSE

The neuroradiologic location of asymptomatic paraclinoid aneurysms is decisive for patient management. In a preliminary study, we designed a paraclinoid MR protocol (PMP) including high-resolution T2-weighted images in 2 orthogonal planes to define the inferior limit of the distal dural ring plane that represents the borderline between the intradural and extradural internal carotid artery. In this clinical study, we compared this protocol with digital subtraction angiography (DSA) for the location of paraclinoid aneurysms.

MATERIALS AND METHODS

During a 3-year period, we performed PMP and conventional angiograms in 14 consecutive patients with 17 asymptomatic paraclinoid aneurysms. Ophthalmic (superior) aneurysms were excluded. Two independent observers reviewed MR imaging data, and a third experienced neuroradiologist analyzed the conventional angiograms. MR imaging and conventional angiograms were independently analyzed, and interpretations obtained with each technique were compared.

RESULTS

PMP allowed correct visualization of the aneurysms in all patients. No significant differences (P >.05) were found between the DSA and PMP for the measurement of the aneurysmal neck or sac. Interobserver agreement was good. MR imaging was discordant with conventional angiography regarding the position around the cavernous sinus of the aneurysmal neck and sac in 5 cases. PMP images were helpful for treatment decisions in 4 cases.

CONCLUSION

PMP is an interesting tool that might be used in association with conventional angiography for the assessment of paraclinoid aneurysms.

Chiasm formation in man is fundamentally different from that in the mouse

At the optic chiasm axons make a key binary decision either to cross the chiasmal midline to innervate the contralateral optic tract or to remain uncrossed and innervate the ipsilateral optic tract. In rodents, midline interactions between axons from the two eyes are critical for normal chiasm development. When one eye is removed early in development the hemispheric projections from the remaining eye are disrupted, increasing the crossed projection at the expense of the uncrossed. This is similar to the abnormal decussation pattern seen in albinos. The decussation pattern in marsupials, however, is markedly different. Early eye removal in the marsupial has no impact on projections from the remaining eye. These differences are related to the location of the uncrossed projection through the chiasm. In rodents, axons that will form the uncrossed projection approach the chiasmal midline, while in marsupials they remain segregated laterally through the chiasm. Histological analysis of the optic chiasm in man provides anatomical evidence to suggest that, unlike in rodents, uncrossed axons are confined laterally from the optic nerve through to the optic tract and do not mix in each hemi-chiasm. This is a pattern similar to that found in marsupials. Electrophysiological evidence in human anophthalmics shows that the failure of one eye to develop in man has no impact on the hemispheric projections from the remaining eye. This strongly suggests that the mechanisms regulating chiasmal development in man differ from those in rodents, but may be similar to marsupials. This implies that optic chiasm formation in rodents and ferrets is not common to placental mammals in general.

Morphologie des Chiasma opticum bei Albinismus

Albinism is associated with a misrouting of fibers at the optic chiasm where the majority of fibers cross to the contralateral side. The cause of this abnormal decussation pattern reflects a disturbance of cell cycle regulation in the development of the retina which is in part controlled by melanin. Growing axons from retinal ganglion cells therefore arrive later than usual at the optic chiasm and are misrouted contralaterally. This atypical decussation leads to morphological changes of the optic chiasm including a reduced chiasm width with larger angles between optic nerves and tracts which can be shown by magnetic resonance imaging.

Large ophthalmic segment aneurysms with anterior optic pathway compression: assessment of anatomical and visual outcomes after endosaccular coil therapy

Object

The optimal therapy for ophthalmic segment aneurysms with anterior optic pathway compression (AOPC) is undecided. Surgical results have been described, but the results of endovascular coil therapy have not been well documented.

Methods

The authors retrospectively reviewed data obtained in all patients who harbored unruptured ophthalmic segment aneurysms with AOPC who underwent endovascular coil therapy at their institution. They analyzed baseline and outcome visual function, aneurysm features, extent of aneurysm closure, internal carotid artery (ICA) occlusion, additional interventions, and neurological outcome.

In 17 patients (16 women), age 38 to 83 years, there were 28 affected eyes. All aneurysms were greater than 10 mm in diameter. In the initial procedures 16 of 17 patients received endosaccular coils and the ICA was preserved; in one patient the aneurysm was trapped and the ICA occluded. Patients then underwent follow up for a mean of 2.90 years (range 1 month–11.2 years) after the last procedure. One patient died of subarachnoid hemorrhage (SAH) 1 month postoperatively and thus no follow-up data were available for this case. Vision worsened in six patients, stabilized in four, and improved in six. Twelve patients underwent 13 subsequent procedures, including endovascular ICA occlusion in seven, repeated coil therapy in five, and optic nerve decompression in one; vision improved in 83% of these cases after ICA occlusion. A second patient died of SAH 5 months after repeated coil treatment. At the final follow up, vision had improved in eight patients (50%), stabilized in four (25%), and worsened in four (25%). In 16 patients with follow-up studies, aneurysm closure was complete in eight (50%) and incomplete in eight (50%).

Conclusions

The authors found that in patients with ophthalmic segment aneurysms causing chronic AOPC, endosaccular platinum coil therapy, with ICA preservation, may not benefit vision and that additional procedures may be needed. Evaluation of their results suggests that endovascular trapping of the aneurysm and sacrifice of the ICA appear to result in good visual, clinical, and anatomical outcomes.

"Mirror-image" bilateral giants: intracavernous carotid artery aneurysms

SUMMARY

The literature on the incidence of "mirror image" bilateral giant intracavernous aneurysms, their symptoms and their association with other entities is reviewed, with a brief comment on their evolution and treatment. A case of "mirror image" bilateral giant intracavernous aneurysms in a 76-year-old man who presented a sudden diplopia with pupillary sparing is reported. A CT scan showed parasellar images and dolichomega circle of Willis arteries that enhanced with endovenous contrast. MRI and angiography disclose bilateral aneurysms in detail, associated with an anomalous origin of the left common carotid artery and bilateral renal artery stenosis.

Early midline interactions are important in mouse optic chiasm formation but are not critical in man: a significant distinction between man and mouse

The optic chiasm is one of the most popular models for studying axon guidance. Here axons make a key binary decision either to cross the midline to innervate the contralateral hemisphere or to remain uncrossed. In rodents, midline interactions between axons from the two eyes are critical for normal development, as early removal of one eye systematically disrupts hemispheric projections from the remaining eye, increasing the crossed projection at the expense of the uncrossed. This is similar to the abnormal decussation pattern seen in albinos. This pattern is markedly different in marsupials where early eye removal has no impact on projections from the remaining eye. These differences are related to the location of the uncrossed projection through the chiasm. In rodents these axons approach the midline whereas in marsupials they remain segregated laterally. We provide anatomical evidence in man suggesting that, unlike in rodents, uncrossed axons are confined laterally and do not mix in each hemi-chiasm, which is a pattern similar to that found in marsupials. Further, we demonstrate electrophysiologically, using visual cortical evoked potentials, that the failure of one eye to develop in man has no impact on the hemispheric projections from the remaining eye. These data demonstrate that the mechanisms regulating chiasmal development in man differ from those in rodents but may be similar to those in marsupials. We suggest that mouse models of the organization and development of the optic chiasm are not common to placental mammals in general.

Anatomic and surgical basis of the sphenoid ridge keyhole approach for cerebral aneurysms

In vascular neurosurgery, the pterional approach has been used primarily for the treatment of a wide variety of diseases (cavernous angiomas, arteriovenous malformations, etc.), and it is used to take advantage of naturally occurring planes and spaces to expose the major structures of the circle of Willis. It provides access to the major part of the anterior circulation aneurysms and those occurring in the upper and most proximal part of the posterior circulation. Conversely, there has been an increasing interest in the so-called minimally invasive procedures or keyhole approaches to treating cerebral aneurysms in specific locations. In this work, we describe a novel keyhole approach that was conceived to achieve the angle of vision and advantages of the classic pterional approach. This surgical approach is based on the anatomic location of the sphenoid ridge and its relationship with the sylvian fissure and basal cisterns. The initial incision is made over the hairline behind the external border of the eye on the side selected. A skin and muscular flap is reflected anteriorly, and a small 3 x 3-cm craniotomy is completed around the external landmarks of the sphenoid ridge. Further extradural drilling is completed down to the anterior clinoid process. The dura is opened in a semilunar manner, and the sylvian fissure is opened completely to reach the sylvian and basal cisterns. Thereafter, the aneurysm is dissected and clipped according to the standard microtechnique of the neurosurgeon. A step-by-step description of the approach is offered in this work to facilitate a clear understanding of it. We recommend this approach for treatment of aneurysms arising at the anterior part of the circle of Willis. It has the advantages of less operative time, fewer days of hospitalization, and similar morbidity and mortality compared with the standard pterional craniotomy (5.7% on our service for nongiant ruptured aneurysms).

Evidence for the improved exposure of the ophthalmic segment of the internal carotid artery after anterior clinoidectomy: morphometric analysis

BACKGROUND

Although resection of the anterior clinoid process (ACP) is valuable in the surgical treatment of aneurysms of the ophthalmic (C6) segment of the internal carotid artery (ICA), quantitative assessment of this adjunct is incomplete. Our morphometric study assesses the effectiveness of the anterior clinoidectomy for exposure of the C6 segment of the ICA.

METHODS

Ten formalin-fixed adult cadaveric heads were dissected bilaterally and pterional craniotomies were performed bilaterally. Measurements before and after resection of the ACP included the length of C6 segment of the ICA on its lateral aspect; C6 segment length on its medial aspect; and medial length of the optic nerve from the optic chiasm to falciform ligament (before ACP resection) then to the annulus of Zinn (after ACP resection).

FINDINGS

Height and width of the intradural ACP were 8.67 +/- 2.63 and 6.57 +/- 1.68 mm, respectively. After clinoidectomy, mean length of the lateral C6 segment of the ICA increased 60% and mean exposure of the medial C6 segment of the ICA increased 113% (p < 0.001). Exposure of the optic nerve increased 150% (p < 0.001) after clinoidectomy and sectioning of the falciform ligament. No correlations were found between the lengths of the ACP and entire C6 segment, or the ACP size and amount of the C6 segment covered by the clinoid.

CONCLUSIONS

Exposure of the C6 segment of the ICA is markedly increased by increase of the mobility of the optic nerve with clinoidectomy and section of the falciform ligament.

Intracranial Aneurysms: an Overview

The outcome of intracranial aneurysms remains disastrous despite progress in diagnosis, management, care, and follow-up. This article discusses the pathology, the etiologies, the epidemiology and the classifications of intracranial aneurysms.

Surgical decompression and coil removal for the recovery of vision after coiling and proximal occlusion of a clinoidal segment aneurysm: technical case report

OBJECTIVE

We present the case of a patient with continued deterioration of vision after endovascular treatment of an unruptured clinoidal segment aneurysm. In conjunction with a review of the literature, the findings in this case highlight the need for further refinements in our understanding of pathophysiological changes induced by coiling of cerebral aneurysms, especially those in aneurysms producing signs and symptoms relating to mass effect.

CLINICAL PRESENTATION

The patient is a 45-year-old man who presented with progressive vision loss. Imaging studies revealed a large, clinoidal segment aneurysm. The patient continued to experience progressive vision loss despite treatment with endovascular coiling, proximal occlusion, and high-dose steroid medication.

INTERVENTION

The patient underwent a craniotomy for decompression of the optic nerve and for salvage of vision. Clipping of the distal vessel was performed, and the coil mass was removed. The patient experienced marked improvement of central vision after the surgical procedure.

CONCLUSION

Although endovascular treatment of aneurysms protects most patients from aneurysm rupture, this case illustrates the fact that coiling, followed by proximal occlusion, might fail to alleviate symptoms related to mass effect. Our experience in this case suggests that early surgical decompression may be indicated for patients presenting with progressive visual deterioration.

Surgical anatomy of the ophthalmic artery: its origin and proximal course

OBJECTIVE

We examined the surgical anatomy of the ophthalmic artery (OA) by dissection of cadaver heads, evaluating the anatomic relationships between the origin of the OA and both its proximal course and surrounding structures. In addition, we demonstrated the surgical application of these anatomic features for safe surgical exploration of this region.

METHODS

Through anatomic dissection, the origin of the OA was examined in both sides of 25 formalin-fixed and 10 fresh cadaver specimens. The following parameters were evaluated: the location of the origin of the OA in relation to the dural rings, the topographic relationship of the paraclinoid region, and the location of the dural penetrating point of the OA in the optic canal.

RESULTS

The OA originated from the internal carotid artery within the intradural space in 49% of cases, just above the upper dural ring in 37%, at the clinoid segment in 7%, and within the cavernous sinus in 6%. The dural penetrating point of the OA was anterior to the falciform ligament, and thereby in the optic canal, in 74% of cases, ventral to the falciform ligament in 19%, and posterior to the falciform ligament in 7%. The anterior circumference point of the upper dural ring, the point at which the upper dural ring intersects the anterior edge of the internal carotid artery, was more anterior to the falciform ligament in 40% of cases and ventral and posterior to the falciform ligament in 16.4% and 43.6%, respectively.

CONCLUSION

Our anatomic findings demonstrate anatomic variation of the OA in terms of its region of origin. Several anatomic points that were noteworthy during surgical exploration of this region are discussed.

Anatomic features of the intracranial and intracanalicular portions of ophthalmic artery: for the surgical procedures

The intracranial and intracanalicular portions of the ophthalmic artery is suspectible to various diseases and injuries; therefore, knowledge of the microanatomy of the complex bony, dural, vascular, and neural relationships of this segment is necessary for proper diagnosis and preservation of the neurovascular structures during subfrontal, pterional and intracanalicular procedures. The artery was studied in 38 human adult cadaver specimens regarding origin, intracranial and intracanalicular portions for surgical approachs. The ophthalmic artery originated from the intradural portion of the internal carotid artery, except in 5% where the ophthalmic artery originated extradurally. The ophthalmic artery originated from medial of superior wall of internal carotid artery in 73.7%, from the central in 21% and the lateral in 5.3% of the specimens. The diameter of the ophthalmic artery at its origin was 2.25+/-0.3 mm on the right and 2.16+/-0.4 mm on the left. The intracranial and intracanalicular course of the artery was divided into short limb, angle "a", long limb, angle "b" and distal part to the apex of the orbit. Awareness of variations in anatomic structures is paramount importance both for diagnosis and treatment of vascular lesions of the brain.

Radiographic imaging of the distal dural ring for determining the intradural or extradural location of aneurysms

The effectiveness of several anatomical and radiological landmarks proposed to determine whether an aneurysm is located intradurally or extradurally is still debated. In anatomical and radiological studies, we examined the relationships of the distal dural ring (DDR) to the internal carotid artery (ICA) and surrounding bony structures to aid in the localization of aneurysms near the DDR. Anatomical relationships were examined by performing dissections on 10 specimens (5 formalin-fixed cadaveric heads). After the position of the DDR, optic nerve, and tuberculum sellae were marked with surgical steel wire, radiographs were taken in multiple projections. The only bony landmark consistently visible on radiographs was the planum sphenoidale. The superior border of the DDR is located at or below the level of the tuberculum sellae, which laterally becomes the superomedial aspect of the optic strut; thus, the optic strut marks the dorsal limit of the DDR. On 50 dry skulls, we measured the vertical distance between the planum sphenoidale and medial aspect of the optic strut (5.0 +/- 0.4 mm), the interoptic strut distance (14.4 +/- 1.4 mm), and the linear distance between the most posterior aspect of the planum sphenoidale (limbus sphenoidale) and the tuberculum sellae (6.0 +/- 0.5 mm). Using these measurements and the planum sphenoidale, tuberculum sellae, and optic strut as reference landmarks, we determined the location of the aneurysm relative to the DDR on angiographic images. In this way, we were able to identify whether lesions were intra- or extradural.

Microneurosurgical management of carotid-ophthalmic aneurysms

OBJECTIVE

To evaluate the management of carotid-ophthalmic segment aneurysms (COA) with modern microneurosurgical techniques and instruments.

METHOD

Sixty patients with COA undergoing microsurgical clipping between March 1994 and June 2002 in the Department of Neurosurgery, Tiantan Hospital, Beijing, were analyzed retrospectively. Neuroimaging included digital subtraction angiography (DSA), MRI, CT, three-dimensional CT angiography and three-dimensional DSA. From 1998, intraoperative Doppler ultrasound monitoring and endoscope-assisted techniques were used.

RESULT

All aneurysms were completely obliterated without either recurrence or death. The morbidity rate of surgery prior to 1998 was 21.7%, which decreased to 13.7% after 1998 (mean 18.3% for the whole study period).

CONCLUSION

Preoperative planning based on neuroimaging is very valuable. Advances in neuroimaging, endoscope-assisted techniques and intraoperative Doppler ultrasound monitoring are useful to decrease postoperative complications. Microneurosurgical techniques are optimal for the management of COA with ever lessening morbidity.

Analysis of supplemental surgical or endovascular treatment for cerebral aneurysms in the endovascular performed cases

SUMMARY

In the 150 endovascular performed cases from May 1997 to Dec 2004, supplemental combination of endovascular and surgical treatments were performed in 46 cases. Characteristics of the treatments were combination for multiple aneurysms, surgical clipping for failed endovascular attempt, embolization for recurrence after clipping, bypass surgery before endovascular parent artery occlusion, surgery for recurrent aneurysms after embolization, and embolization for failed surgical attempt. Sixty seven percent of ruptured and 87% of unruptured cases showed satisfactory clinical outcome (modified Rankin scale = 0 to 2). Supplemental combination of each treatment will support the disadvantage of another treatment, and which improve the clinical outcome of cerebral aneurysm.

Variations in the architecture and development of the vertebrate optic chiasm

At the vertebrate optic chiasm there is major change in fibre order and, in many animals, a separation of fibres destined for different hemispheres of the brain. However, the structure of this region is not uniform among all species but rather shows marked variations both in terms of its gross architecture and the pathways taken by different fibres. There also are striking differences in the developmental mechanisms sculpting this region even between closely related animals. In spite of this, recent studies have provided strong evidence for a remarkable degree of conservation in the molecular nature of the guidance signals and regulatory genes driving chiasmatic development. Here differences and similarities in chiasmatic organisation and development between separate groups of animals will be reviewed. While it may not be possible to ascribe a single set of factors that are universal components of the vertebrate chiasm, there are both strikingly similar elements as well as diverse features to the development, organisation and architecture of this region. This review aims to highlight key issues in the organisation and development of the vertebrate optic chiasm with a focus on comparing and contrasting the data that has been gleaned to date from different vertebrate groups.

Embryology of the internal carotid artery dural crossing: apropos of a continuous series of 48 specimens

The aim of this study was to describe the embryologic and foetal development of the anterior paraclinoid region and more precisely the relationship of the internal carotid artery to the dura mater. This has been done by examining a collection of histological sections, representing a continuous series of 48 embryologic and foetal specimens, covering the period of the first 6 months of intra-uterine life. Neurological and vascular elements develop during the embryologic period; the internal carotid artery is recognizable in the various sections of its course and acquires a histological adult parietal constitution. The foetal period corresponds to the development of the meningeal structures. The superior, medial and lateral walls appear on the fifteenth week of amenorrhoea and do not change after that. The internal carotid artery enters subarachnoid space accompanied by a sleeve of mesenchymatous cells, which fixes it to the anterior clinoid process. The constitution of this sleeve, arising from the superior wall of the lateral sellar compartment, remained independent of the principle vascular part, which allows the formation of a plan of cleavage. The foetal relations of the dura mater and the internal carotid artery were seen to be different from those of adult subjects described in the literature, suggesting an existence of period of maturation postnatally.

Application of CT angiography of complex cerebrovascular lesions during surgical decision making

Helical computed tomographic angiography (CTA) is a relatively new noninvasive volumetric imaging technique. Since early reports in the 1990s, CTA has rapidly improved image resolution and scan volume. Cerebral arteries can be imaged clearly, which is advantageous in the diagnosis of vascular diseases such as cerebral aneurysms, arteriovenous malformations, and cerebrovascular occlusive disease. Before attacking a cerebrovascular lesion near or in the skull base, precise preoperative knowledge of anatomic relationships between the bony and neurovascular structures is critical for obtaining successful outcomes. The sensitivity of CTA for the detection of cerebral aneurysms < or = 5 mm in diameter may be higher than that of digital subtraction angiography (DSA), with equal specificity and high interoperator reliability. With minor modification to the technique, paraclinoid vascular lesions can be depicted using CTA. We present our experience using CTA in addition to DSA to obtain important anatomic information about skull base vascular lesions that assisted in the clinical decision-making process.

Enhanced exposure of carotico-oculomotor triangle following extradural anterior clinoidectomy: a comparative anatomical study

OBJECTIVE

To quantify and compare the carotico-oculomotor triangle (COT) area before and after extradural anterior clinoidectomy (AC).

METHODS

Ten cadaveric heads were dissected bilaterally. Before and after an extradural AC, the following points were measured: (1) the internal carotid artery (ICA) bifurcation to the tip of the anterior clinoid process (ACP) (A) and to the distal dural ring (A'), (2) the ICA bifurcation to the point where the oculomotor nerve becomes obscured by the tentorial fold (B) and to the porus oculomotoris after incision of the tentorial fold (B'), and (3) the tip of the ACP to the point where the oculomotor nerve becomes obscured by the tentorial incisura (C) and from the distal dural ring to the porus oculomotoris (C'). The area of the COT was calculated before and after AC (DeltaABC and DeltaA'B'C', respectively).

RESULTS

The mean values were as follows: A: 9.15 +/- 0.93 mm, A': 13.45 +/- 0.82 mm; B: 7.80 +/- 1.24 mm, B': 9.90 +/- 1.21 mm; C: 7.15 +/- 0.99 mm, C': 9.3 +/- 1.26 mm; DeltaABC: 26.26 +/- 6.05 mm, DeltaA'B'C': 45.06 +/- 8.92 mm.

CONCLUSIONS

Extradural AC enhances the exposure of the COT almost twofold. This increased exposure can be of significant help during resection of lesions of the parasellar and basilar apex regions.

Conventional microsurgical treatment of paraclinoid aneurysms: state of the art with the use of the selective extradural anterior clinoidectomy SEAC

Surgical treatment of paraclinoid aneurysms is considered to be difficult due to their complicated anatomical location in the vicinity of important neural, vascular and bony structures. We present our clinical experience of the past 10 years of conventional microsurgical treatment of 81 paraclinoid aneurysms in 75 patients with the use of selective extradural anterior clinoidectomy SEAC and discuss the method of therapy option by reviewing recent reports on results of endovascular coiling method and the combination of these with conventional microsurgical therapy. The favorable surgical results with the use of SEAC and no recurrence of the treated aneurysm after clipping procedure in our series indicate that direct surgery can still be a standard technique for paraclinoid aneurysms in view of the fact that the endovascular aneurysm coiling methods are still associated with a considerable percentage of incomplete occlusion and present the problem of coil packing.

Computer simulation of flow dynamics in paraclinoidal aneurysms

SUMMARY

Endovascular treatment, which is very useful method especially for paraclinoidal aneurysms, has the limitations of coil compaction and recanalization, which are difficult to predict. We tried to understand flow dynamic features, one of the important factors of such problems, using computer flow dynamics (CFD) simulations. CFD simulations were made in paraclinoidal aneurysm model of different size and protruded directions. Flow patterns, flow velocities and pressure are analyzed. Although the pressure on the aneurismal orifice is highest in the aneurysm protruding vertically - upward, the flow velocity is highest in the superior-medial protruding one. Significant difference is not observed in either flow patterns, flow velocities or pressures on the aneurismal orifices between the sizes of aneurismal sac. Among paraclinoidal aneurysms, an aneurysm protruding to superior-medially receives the most severe haemodynamic stresses at the orifice and the aneurysm size does not cause significant differences in the aspect of flow dynamics. It should be considered in the treatment of such aneurysms.

MRI location of the distal dural ring plane: anatomoradiological study and application to paraclinoid carotid artery aneurysms

The distal dural ring plane (DDRP) separates the intradural from the extradural paraclinoid internal carotid artery. The purpose of this study was to evaluate its position with MR imaging. The protocol used a T2-weighted sequence in two orthogonal planes: diaphragmatic (DIA-P) and carotid (CAR-P). The DDRP passes through four anatomoradiological reference points (RefP). We developed on a cadaveric model a correlation method supported by correlation lines and angles (CA) projecting the RefP toward the DDRP. RefP were correlated to the DDRP in 65-84% of cases in the DIA-P and 60-76% of cases in the CAR-P. CA were identified and correlated to the DDRP, respectively, in 87% and 60% of cases in the DIA-P, and 60% and 51% of cases in the CAR-P (failure often related to a lack of visibility of just one RefP). A higher tissular contrast in living subjects allowed the identification of CA in 90% and 80% of cases, respectively, in the DIA-P and the CAR-P. We propose that CA, when identified, should be considered as an approximation of the inferior radiological limit of the DDRP curve. In difficult angiographical cases, this MRI protocol could help to locate paraclinoid aneurysms on both sides of the cavernous sinus roof.

Large paraclinoid aneurysm with a calcified neck treated by tailored multimodality procedures

A 68-year-old woman presented with a large paraclinoid aneurysm with a calcified neck causing visual symptoms. Direct clipping was hazardous because of severe calcification of the neck. Endovascular internal trapping was difficult because of the short distance between the neck and the origin of the posterior communicating artery. Proximal occlusion was likely to be less effective because of large collateral back flow to the aneurysm via the ophthalmic artery (OphA). The aneurysm was successfully treated by a combination of a high-flow bypass, intraoperative coil embolization of the parent artery including the origin of the OphA, and clipping of the internal carotid artery distal to the aneurysm. Paraclinoid aneurysms may be difficult to treat by the simple application of direct clipping, endovascular coiling, or trapping. Multimodality procedures can be tailored to treat such aneurysms.

Thrombotic Intracranial Aneurysms: Classification Scheme and Management Strategies in 68 Patients

OBJECTIVE:

Thrombotic aneurysms are a diverse collection of complex aneurysms characterized by organized intraluminal thrombus and solid mass. Consequently, their treatment often requires techniques other than conventional clipping, such as thrombectomy with clip reconstruction or bypass with parent artery occlusion. A single-surgeon experience with thrombotic aneurysms was analyzed to determine optimal treatment strategies. A classification scheme was devised on the basis of aneurysm, thrombus, and lumen morphology to relate these anatomic features to surgical therapy.

METHODS:

Sixty-eight patients with thrombotic aneurysms were managed during a period of 6.25 years. Thrombotic aneurysms were classified into six types: concentric (n = 17, 25%), eccentric (n = 14, 21%), lobulated (n = 2, 3%), complete (n = 2, 3%), canalized (n = 17, 25%), and coiled (n = 16, 24%).

RESULTS:

Aneurysm management consisted of direct clipping (n = 22, 32%), thrombectomy-clip reconstruction (n = 18, 26%), bypass-occlusion (n = 20, 29%), other (n = 6, 9%), or observation (n = 2, 3%). Complete angiographic obliteration was achieved in 97% of patients, and 47% of aneurysms were thrombectomized. The surgical mortality rate was 6%, and the permanent neurological morbidity rate was 7%. Overall, 87% of patients were improved or unchanged at follow-up, with 79% reaching a Glasgow Outcome Scale score of 5 or 4. Management strategy was influenced by thrombotic aneurysm type, but patient outcome was not. The best results were observed in patients treated with direct clipping and bypass-occlusion.

CONCLUSION:

Despite their solid mass, one-third of thrombotic aneurysms can be treated surgically with conventional clipping. Direct clipping is associated with the best surgical results, and the proposed classification scheme identifies thrombotic aneurysms that may be clippable. Patients with unclippable thrombotic aneurysms had more favorable results when treated with bypass and aneurysm occlusion than with thrombectomy and clip reconstruction. The classification scheme may provide conceptual clarity and therapeutic guidance with preoperative and intraoperative decision making.

Postoperative vasospasm of unruptured paraclinoid carotid aneurysms: analysis of 30 cases

This study was conducted to determine the incidence, severity, and causes of delayed vasospasm after clipping of unruptured paraclinoid aneurysms of the internal carotid artery (ICA). A retrospective analysis was made of 30 patients, who underwent clipping of unruptured paraclinoid aneurysms in our institution between 1991 and 1998. We compared angiograms before and after operation and classified them into two groups: vasospasm group and non-vasospasm group. Eleven variables were assessed as to their relationship to delayed vasospasm. There were 9 patients (30%) in the vasospasm group, of which 3 patients (10%) were clinically symptomatic. For all symptomatic patients, aggressive treatment, including triple-H therapy, was conducted with good outcome. The number of clips used (p<0.04) and temporary occlusion of the ICA (p<0.005) were statistically significant factors associated with the incidence of vasospasm. It is suggested that mechanical stimulation to the vascular wall of the ICA is responsible for causing spasm in addition to intraoperative bleeding around the dural ring.

Simultaneous microscopic and endoscopic monitoring during surgery for internal carotid artery aneurysms

Object. The authors of this study evaluated the efficacy of simultaneous microscopic and endoscopic monitoring during surgery for internal carotid artery (ICA) aneurysms.

Methods. The endoscopic technique was applied during microsurgery in 11 patients with 13 aneurysms. Nine of these lesions were located on the posterior communicating artery (PCoA), three in the paraclinoid region, and one on the anterior choroidal artery (AChA). Eight patients had unruptured aneurysms and three had ruptured aneurysms. The endoscope was introduced after first exposing the aneurysm through the microscope and was gripped firmly by an air-locked holding arm fitted with a steering system throughout the entire surgery, including dissection of the perforating arteries and application of the aneurysm clips.

Regarding paraclinoid aneurysms, clips were applied through direct visualization of the ophthalmic artery and the proximal neck. In a case involving a superior hypophyseal artery aneurysm in the paraclinoid segment, a ring clip was applied without removing the bone structure around the optic canal. In all aneurysms of the PCoA and the AChA, perforating arteries behind the lesion were identified and dissected using endoscopic control. The aneurysm clip was applied in the best position in a single attempt in 10 of 11 patients. There was no surgical complication related to the endoscopic procedures.

Conclusions. Simultaneous monitoring with the microscope and endoscope is extremely useful in applying clips to ICA aneurysms. This combined method allows for direct dissection of the aneurysm, perforating vessels, and the main trunk in an area not visible through the microscope's eyepiece and promises better surgical results.

Ruptured intrasellar superior hypophyseal artery aneurysm presenting with pure subdural haematoma. Case report

SUMMARY

Subdural haemorrhage from a ruptured intracranial aneurysm is a well-known entity when associated with subarachnoid haemorrhage. However, haemorrhage confined only to the subdural space is rare because there are limited anatomical sites where extravasation can be purely subdural. We report the rare case of a patient who suffered pure subdural haematoma after the rupture of a left superior hypophyseal artery aneurysm located within the sella turcica. The patient was treated with endovascular coil embolization of the aneurysm. Angiography immediately after treatment and one month later revealed complete obliteration of the aneurysm. Six months after treatment, the patient remained symptom free.

Surgery for carotid dural ring aneurysms

BACKGROUND

Carotid aneurysms of the paraclinoid segment are usually located in the intradural space, but can infrequently straddle the intra- and extradural space.

CASE DESCRIPTION

We present 2 cases of unruptured carotid dural ring aneurysms with an aneurysmal sac that straddled the distal dural ring. Each paraclinoid aneurysm projected superiorly from the anterior surface of the internal carotid artery with a relatively flattened dome and central indentation on angiography. The aneurysmal domes were circumscribed by the distal dural ring and straddled the intra- and extradural space. After broad opening of the distal dural ring, aneurysms were successfully obliterated by clip application in parallel with the internal carotid artery.

CONCLUSION

These cases underscore the significance of an aneurysmal dome indentation on angiographic images as a reflection of aneurysmal circumscription by the distal dural ring. Aneurysms that straddle the intra- and extradural space may require broad opening of the distal dural ring for adequate control and clipping.

Balloon-assisted microvascular clipping of paraclinoid aneurysms

✓ Paraclinoid aneurysms represent a significant surgical challenge. Multiple techniques have been developed to maximize the effectiveness and safety of excluding these aneurysms from the cerebral circulation. Endovascular balloons have been used for proximal control of parent arteries during the treatment of aneurysms. In this report the authors describe the technique of navigating an endovascular balloon across the neck of paraclinoid aneurysms in four patients to gain proximal control, improve the accuracy of clip placement, and reduce the risk of distal embolization of intraluminal thrombus.

Six consecutive patients with giant or complex aneurysms of the ophthalmic or paraclinoid internal carotid artery that were not amenable to endovascular obliteration were retrospectively analyzed. In all six patients, the aneurysm was exposed and dissected for microsurgical clipping, and attempts were made to navigate a nondetachable, compliant silicone balloon across the neck of the aneurysm. If successfully placed, the balloon was inflated during clip placement. In four patients, the balloon was successfully navigated across the neck of the aneurysm and was inflated during clip application. Internal carotid artery tortuosity precluded navigation of the balloon into the intracranial circulation in two patients. All aneurysms were completely excluded from the parent vessel according to postoperative angiography studies. No complication occurred as a direct result of the endovascular portion of the procedure.

Endovascular balloon stenting of complex paraclinoid aneurysms during microvascular clipping may provide an adjunctive therapy that facilitates safe and accurate clip placement.

Computer simulation of flow dynamics in an intracranial aneurysm. Effects of vessel wall pulsation on a case of ophthalmic aneurysm

SUMMARY

Using a supercomputer, the authors studied the effect of vessel wall pulsation on flow dynamics with a three-dimensional model simulating both a rigid and pulsatile style. The design of the aneurysm models was set with a 5 mm dome diameter and a 1 or 3 mm orifice size to simulate a carotid-ophthalmic aneurysm. Flow dynamics were analyzed according to flow pattern, wall pressure and wall shear stress. The flow pattern in the aneurysm sac showed the great difference between rigid and pulsatile models particularly in the small-neck aneurysm model. The arterial wall tended to be exposed to a higher pressure peak in the pulsatile model than in the rigid one, especially at its bifurcation and curved regions. Sites of shear stress peak were found on the aneurysmal dome as well as at the distal end of the orifice in both rigid and pulsatile models. The effects of vessel-wall pulsation should be considered whenever evaluating conditions in and around an aneurysm.

Paraclinoid and cavernous sinus regions: Measurement of critical structures relevant for surgical procedure

Determination of the safest distance the falciform ligament can be incised from its origin to the orbital apex. Measurement of the distance between the oculomotor foramen and the IV nerve in the lateral wall of the cavernous sinus. Evaluation of the optic strut as an accurate landmark between the intradural (subarachnoid) and extradural segment of the internal carotid artery (ICA). Ten fixed human cadaver heads were examined for a total of 20 sides. A frontotemporal craniotomy, an orbito-optic osteotomy, and extradural anterior clinoidectomy were carried out followed by opening the falciform ligament, circumferentially releasing the distal dural ring and dissection of the lateral wall of the cavernous sinus under the operating microscope. We measured: 1) the distance between the entry of the III nerve and the point where the IV nerve crosses over it into the cavernous sinus; 2) the distance the falciform ligament can be incised along the optic nerve laterally until the IV nerve is encountered at the orbital apex; 3) the distance between the optic strut and the lateral part of the distal dural ring; and 4) the distance between the optic strut and the ophthalmic artery. All measurements were made in millimeters, using small calipers. The distance between the optic strut and the lateral part of the distal dural ring ranges from 3-7.5 mm (mean=5.47 mm). In all our specimens, the ophthalmic artery was found distally from the optic strut in the intradural space at a distance ranging from 0.5-7 mm (mean=3.35 mm). The distance between the entry of the third nerve and the IV nerve into the cavernous sinus ranged from 7-15 mm (mean=10.9 mm). The distance between the origin of the falciform ligament and the IV nerve at the level of the orbital apex ranged from 9-15 mm (mean=10.75 mm). The falciform ligament and the optic sheath should not be opened longer than 9 mm along the lateral optic nerve or injury to the IV nerve can occur. Starting at the oculomotor foramen, the opening of the cavernous sinus should be limited to 7 mm to avoid injuring the IV nerve. Finally, the optic strut can be a reliable bony landmark that separates the subarachnoid space and extradural compartments along the anterior and medial ICA.

Penetration of the Optic Nerve by an Internal Carotid Artery-Ophthalmic Artery Aneurysm: Case Report and Literature Review

OBJECTIVE AND IMPORTANCE

Although it is well known that large or giant internal carotid artery-ophthalmic artery aneurysms can cause visual deficits, penetration and schism of the optic nerve by an aneurysm are very rare.

CLINICAL PRESENTATION

A 48-year-old man presented with an acute onset of right visual deterioration after an episode of severe headache. Magnetic resonance imaging demonstrated penetration of the right optic nerve by an intracranial aneurysm. Cerebral angiography revealed an internal carotid artery-ophthalmic artery aneurysm of 12 × 7 mm. The aneurysm was directed superomedially and appeared to have a “waist” within the penetration.

INTERVENTION

Intraoperatively, we observed that part of the aneurysm wall was visible through the optic nerve fibers at the junction with the optic chiasm.

CONCLUSION

Although there was no direct evidence of subarachnoid hemorrhage on imaging scans or with operative exploration, we think that the patient must have experienced sentinel hemorrhaging, leading to visual deterioration. We describe the case in detail and review the world literature.

Unruptured paraclinoid aneurysms: a management strategy

OBJECT

To elucidate an optimal managenent strategy for unruptured paraclinoid aneurysms, the authors retrospectively reviewed their experience in the treatment of 100 patients who underwent 112 procedures for111 paraclinoid aneurysms performed using direct surgery and/or endovascular treatment.

METHODS

Between 1997 and 2002, 111 unruptured paraclinoid aneurysms categorized according to a modified al-Rodhan classification (Group la, 30 anterior wall lesions; Group lb, 25 ventral paraclinoid lesions; Group IL 18 true ophthalmic artery lesions; Group III, 37 carotid cave lesions; and Group IV, one transitional lesion) were treated by direct surgery (35 lesions) and/or endovascular treatment (77 lesions) (one aneurysm was treated by both procedures). In lesions in Groups Ia, Ib, II, and III that were treated by endovascular treatment, complete aneurysm obliteration was achieved in 50, 65, 50, and 78%, respectively, and the combined transient and permanent morbidity rates due to cerebral embolic events were 20, 25, 20, and 13.9%, respectively. Overall, the transient morbidity rate after endovascular treatment was 14.3% and the permanent morbidity rate was 6.5%. Notably, permanent visual deficits caused by retinal embolism occurred after endovascular treatment in two patients with Group II aneurysms. Direct surgery was mainly performed in Groups Ia (20 lesions), Ib (five lesions), and II (eight lesions), with complete neck clip occlusion achieved in 80, 80, and 71.4%, respectively; the transient and permanent morbidity rates associated with aneurysms treated by surgery were 8.6 and 2.9%, respectively.

CONCLUSIONS

Endovascular therapy for superiorly projecting paraclinoid aneurysms (Groups Ia and II) is associated with lower rates of complete obliteration than direct surgery, and with rates of cerebral embolic events comparable to those of endovascular treatment in the other groups. Furthermore, endovascular treatment for Group II aneurysms entails additional risks of retinal embolism. Therefore, direct surgery is recommended for the treatment of paraclinoid aneurysms projecting superiorly. For other groups, especially for Group III, endovascular treatment is the acceptable first line of therapy.

An alternative extradural exposure to the anterior clinoid process: the superior orbital fissure as a surgical corridor

OBJECTIVE

Dolenc has pioneered the extradural approach to the anterior clinoid process (ACP) in approaching the cavernous sinus, clinoidal space, and orbital apex. A key step is the division of the frontotemporal dural fold (FTDF). Less experienced surgeons may not be as versatile in their three-dimensional understanding of the superior orbital fissure and thus may risk injury to its contents. Through our cadaveric and subsequent clinical experience, we have devised a modification of the approach that permits safer handling of the contents of the superior orbital fissure.

METHODS

In five consecutive injected cadaveric heads (10 sides), we performed on one side a traditional extradural exposure of the ACP. On the other side, we performed our alternative dissection. Instead of exposing the ACP from medial to lateral and dividing the frontotemporal dural fold along the assumed path of safety, we followed the edge of the lesser wing from lateral to medial, uncovered the superior orbital fissure, and peeled the outer layer of the cavernous sinus medial to the foramen rotundum along the greater wing, thus uncovering the inferolateral surface of the ACP. This allowed dural division under full visualization.

RESULTS

The alternative method proved easier and more reliable in every case. We applied this technical modification in seven patients with no complications. Specifically, there was no injury to the oculomotor, lacrimal, frontal, or trigeminal nerves or branches. We present detailed anatomic expositions of the injected specimens.

CONCLUSION

This technical modification of the extradural approach of Dolenc is a simple, safe, and valuable adjunct to the exposure of the ACP. We recommend its use particularly by relatively inexperienced surgeons.

Endovascular treatment of paraclinoid aneurysms: experience with 73 patients

OBJECTIVE

Aneurysms arising from the internal carotid artery in close relation to the clinoid process have been called paraclinoid aneurysms. The surgical management of these aneurysms poses technical challenges, and such patients are frequently referred for endovascular treatment. We reviewed our experience with endovascular coil embolization of paraclinoid aneurysms to evaluate the safety and efficacy of this treatment modality.

METHODS

From December 1993 to May 2002, 70 patients underwent endovascular procedures with detachable coils for 73 paraclinoid aneurysms (8 ruptured, 65 unruptured) at the University of Pittsburgh Medical Center and the University of Texas Southwestern Medical Center. A retrospective review of the medical records, outpatient charts, and operative reports was performed. Angiographic outcome was determined at the end of each procedure and by review of follow-up angiograms. Clinical assessments and outcomes are reported according to the Glasgow Outcome Scale (GOS).

RESULTS

Immediate angiographic outcomes for 73 paraclinoid aneurysms demonstrated complete occlusion in 53 (72.6%), near-complete occlusion in 6 (8.2%), and partial occlusion in 14 (19.2%). Nine aneurysms required more than one coiling session to complete treatment; 8 of these aneurysms required two sessions and 1 required four, for a total of 84 endovascular procedures. Follow-up angiograms could be obtained in 49 patients with 52 paraclinoid aneurysms. During the follow-up period, 6 aneurysms demonstrating partial occlusion and 3 demonstrating near-complete occlusion showed spontaneous progression of thrombosis to complete occlusion. Twelve aneurysms initially demonstrating complete occlusion (5 aneurysms), near-complete occlusion (3 aneurysms), or partial occlusion (4 aneurysms) showed coil compaction requiring retreatment. Of these 12 aneurysms that demonstrated coil compaction, 3 were treated with surgery and 9 with coil repacking. The final angiographic outcomes, determined on the last available follow-up angiograms of 49 aneurysms, excluding 3 surgically clipped aneurysms, showed complete occlusion in 43 (87.8%), near-complete occlusion in 3 (6.1%), and partial occlusion in 3 (6.1%). The angiographic follow-up period ranged from 4 to 54 months (mean, 13.9 mo). Morbidity and mortality rates related to 84 endovascular procedures were 8.3 and 0%, respectively. There were no recurrent or new subarachnoid hemorrhages in 63 patients in whom clinical follow-up could be performed during a mean clinical follow-up period of 14.4 months. The final clinical outcomes demonstrated a GOS score of 5 (good recovery) in 56 patients (88.9%), a GOS score of 4 (moderate disability) in 2 (3.2%), and a GOS score of 3 (severe disability) in 1 (1.6%). Four patients (6.3%) died of unrelated causes. The average period of hospitalization was 17.8 days in patients with acutely ruptured aneurysms and 3.5 days in patients with unruptured or retreated aneurysms.

CONCLUSION

The results of this study indicate that endovascular treatment is a safe and effective therapeutic alternative in ruptured and unruptured paraclinoid aneurysms. The endovascular treatment may also confer a positive impact in terms of the length of hospital stay.

Subclinoid aneurysms

OBJECT

This study was undertaken to analyze the features that define subclinoid aneurysms.

METHODS

Five cases of laterally directed carotid artery (CA) aneurysms adjacent to the anterior clinoid process (ACP) were identified in a series of approximately 1400 surgically treated aneurysms. These cases were selected because the aneurysms had the same features as the only previously described "subclinoid" aneurysm. The angiographic and anatomical features of the five cases were analyzed.

CONCLUSIONS

Subclinoid aneurysms are a unique group of congenital berry aneurysms. They originate from the lateral surface of the CA adjacent to the ACP. They are partially or completely hidden from view at surgery by the ACP and are partially or completely proximal to the distal dural ring of the CA. The proximal neck of these lesions is located at the same level of the CA cut perpendicular to its axis of blood flow as the origin of the ophthalmic artery (OphA), but they do not originate at that or any other branch of the CA. They can only be definitively differentiated from OphA, anterior paraclinoid, and blister-like aneurysms at surgery.