Safety of drilling for clinoidectomy and optic canal unroofing in anterior skull base surgery

Spheno-Orbital Meningioma - Treatment Outcomes and Factors Influencing Recurrence

PURPOSE

To determine treatment outcomes, recurrence rates, and predictors of recurrence, to inform future therapeutic approaches for spheno-orbital meningiomas (SOM).

METHODS

A retrospective single-center study of SOM treated from 1990 to 2021 was conducted with comprehensive neuro-ophthalmologic follow-up at Columbia University Medical Center (CUMC). Recurrence requiring reintervention was defined clinically as worsening of visual acuity, visual field defect, or ocular motility after an initial period of stabilization or 6 months of improvement following treatment, or radiologically as either a regrowth with an increase in tumor size by 20% at the site of previous growth or a new region of tumor growth.

RESULTS

In total 46 patients met the inclusion criteria. The mean follow-up was 106 months (range 1-303). Dictated by the phenotype of the disease, patients underwent either gross- (50%), near- (17%), or subtotal resection (26%). Removal of the anterior clinoid process (ACP) was performed in 52% of patients. Nine patients (20%) required an enucleation or exenteration. Radiotherapy was employed at some point of treatment in 50% of cases. Inherited cases (24%) were referred to CUMC for treatment following 1 or more recurrences. The total recurrence rate, including inherited cases, was 54%, occurring at a mean interval of 43 months. The recurrence rate of patients treated solely at CUMC was 40%, occurring at a mean interval of 41 months. A subset of patients (32%) had 2 or more recurrences. Histopathology at the first surgery was WHO grade I (87%) and II (13%) and at the final surgery was WHO grade I (74%), II (21%), and III (4%). A subset of grade I tumors that received radiotherapy (35%) evolved to a higher grade or developed multiple recurrences without a change in histologic grade I. Grade II tumors and treatment with radiotherapy increased the odds of recurrence. Removal of the ACP and gross total resection decreased the odds of recurrence.

CONCLUSION

Due to the routinely long interval to tumor recurrence, lifelong surveillance of patients with SOM is prudent. ACP resection and gross total resection, where possible, reduce tumor recurrence and the need for further treatment. Radiotherapy should be reserved for higher-grade meningiomas and select grade I tumors.

A Six-Surface System to Describe Anatomy of Anterior Clinoid Process and Its Application in Anterior Clinoidectomy and Resection of Paraclinoid Meningioma

OBJECTIVE

The anterior clinoid process (ACP) is surrounded by nerves and vessels that, together, constitute an intricate anatomical structure with variations that challenges the performance of individualized anterior clinoidectomy in treating lesions with different extents of invasion. In the present study, we established a 6-surface system for the ACP based on anatomical landmarks and analyzed its value in guiding ACP drilling and resection of paraclinoid meningiomas.

METHODS

Using the anatomical characteristics of 10 dry skull specimens, we set 9 anatomical landmarks to delineate the ACP into 6 surfaces. Guided by our 6-surface system and eggshell technique, 5 colored silicone-injected anatomical specimens were dissected via a frontotemporal craniotomy to perform anterior clinoidectomy. Next, 3 typical cases of paraclinoid meningioma were selected to determine the value of using our 6-surface system in tumor resection.

RESULTS

Nine points (A-H and T) were proposed to delineate the ACP surface into frontal, temporal, optic nerve, internal carotid artery, cranial nerve III, and optic strut surfaces according to the adjacent tissues. Either intradurally or extradurally, the frontal and temporal surfaces could be identified and drilled into depth, followed by skeletonization of the optic nerve, cranial nerve III, internal carotid artery, and optic strut surfaces. After the residual bone was removed, the ACP was drilled off. In surgery of paraclinoid meningiomas, our 6-surface system provided great benefit in locating the dura, nerves, and vessels, thus, increasing the safety of opening the optic canal and relaxing the oculomotor or optic nerves and allowing for individualized ACP drilling for meningioma removal.

CONCLUSIONS

Our 6-surface system adds much anatomical information to the classic Dolenc triangle and can help neurosurgeons, especially junior ones, to increase their understanding of the paraclinoid spatial structure and accomplish individualized surgical procedures with high safety and minimal invasiveness.

Efficiency and safety of optic canal unroofing in tuberculum sellae meningiomas: a meta-analysis and systematic review

Optic canal unroofing (OCU) has gradually become a routine technique for tuberculum sellae meningiomas (TSMs) resection. This meta-analysis aimed to evaluate the efficacy and safety of OCU. A systematic review and meta-analysis of the published literature on this topic from 2003 to 2023 were conducted in accordance with the PRISMA guidelines. Rigorous statistical analysis with a p-value was performed for related change in visual improvement, gross total resection (GTR), visual deterioration, and olfactory nerve damage. The study included 15 articles with 384 patients in whom OCU was performed by the transcranial approach (TCA) or the endoscopic endonasal approach (EEA). Of these, 341 patients had preoperative visual loss, and 266 patients had postoperative visual recovery. The overall rate of visual improvement was 0.803 (95% CI: 0.733-0.874, p < 0.01). The rate of visual improvement in the EEA and TCA groups was 0.884 (95% CI: 0.803-0.965, p < 0.01) and 0.788 (95% CI: 0.700-0.875, p < 0.01). Further analysis of classification shows that the rate of visual improvement in Type I: < 2 cm was 0.889(95% CI: 0.739-0.969), Type II:2-4 cm was 0.844(95% CI: 0.755-0.910), Type III: > 4 cm was 0.500(95% CI: 0.068-0.932) and the total was 0.853(95% CI: 0.779-0.927 p < 0.01) with low heterogeneity of I2 = 20.80%.Twelve studies separately reported GTR with OCU was 293; the rate of GTR was 0.911 (95% CI: 0.848-0.961, p < 0.01). And the rate of GTR in Type I: < 2 cm was 0.933(95% CI: 0.817-0.986), Type II:2-4 cm was 0.880(95% CI: 0.800-0.936), Type III: > 4 cm was 0.600(95% CI: 0.147-0.947). The total was 0.897(95% CI: 0.830-0.965 p < 0.01) with low heterogeneity of I2 = 34.57%. The related complications of OCU were visual deterioration and olfactory nerve damage. Visual decline was reported in nine studies, and the rate was 0.077 (95% CI: 0.041-0.113, p < 0.01). Six studies reported olfactory nerve damage, and the overall rate was 0.054 (95% CI: 0.019-0.090, p < 0.01). OCU could significantly recover preoperative impaired vision and make GTR easier to achieve, which was also a safe and effective technique in TSM.

Endoscopic Endonasal Transsphenoidal Approach to Repair Cerebrospinal Fluid Rhinorrhea After an Anterior Clinoidectomy for Aneurysm Clipping: Series of 4 Cases

BACKGROUND

Cerebrospinal fluid (CSF) rhinorrhea through a pneumatized optic strut is a known potential complication after an anterior clinoidectomy that is used to microsurgically clip a proximal internal carotid artery aneurysm. The original craniotomy site can be reopened to repair the skull base defect, but this technique has disadvantages.

OBJECTIVE

To avoid a repeat craniotomy and address the limitations of a transcranial approach, a straightforward alternative was used for skull base repair-the binostril endoscopic endonasal transsphenoidal approach.

METHODS

This retrospective case series describes the use of endoscopic transsphenoidal repair and outcomes for patients with CSF leaks after anterior clinoidectomy for aneurysm repair between January 1, 2015, and December 31, 2019.

RESULTS

Four adult patients (3 women and 1 man) with a mean age of 59.5 years were reviewed. Skull base repair occurred on average 24 days (range, 4-75 days) after the index operation. After demucosalization of the parasellar sphenoid sinus, the fistula in the pneumatized optic strut was reconstructed with a free nasal mucosal graft with or without an autologous muscle graft. None of the patients developed a recurrent CSF leak at a mean follow-up of 12.5 months (range, 8-22 months), and none experienced complications.

CONCLUSION

The endoscopic endonasal transsphenoidal approach was safe and effective for skull base repair in 4 patients with CSF rhinorrhea after an anterior clinoidectomy for aneurysm clipping.

How I do it: management of M2 tear injury caused by drilling during intradural anterior clinoidectomy for microsurgical clipping of intracranial aneurysms

BACKGROUND

High-speed drilling is associated with potential injury to neurovascular structures, particularly during intradural drilling of the anterior clinoid process.

METHOD

During an anterior clinoidectomy, a cotton patty and middle cerebral artery branches became inadvertently wrapped around the bit, causing a tear on the inferior M₂ trunk. Following temporary clipping of the internal carotid artery, the tear was identified. Temporary clips were placed proximally and distally. The tear was then repaired with interrupted microsutures.

CONCLUSION

Extreme care should be exercised during clinoidectomy. Should small vascular injury occur, direct microsuturing can be a good alternative to sacrificing or implantation anastomosis repair.

How I do it: optic canal unroofing in surgery for tuberculum sellae meningiomas with compression of the optic nerve

BACKGROUND

Tuberculum sellae meningiomas are challenging to treat when accompanied with altered vision due to compression of the optic nerve. These tumors mostly refer to be benign; therefore, gross total removal and excellent functional recovery are desired.

METHOD

We describe the microsurgical treatment of tuberculum sellae meningioma with altered vision function on the left eye. Intradural unroofing of the optic canal with gross total resection of the tumor led to immediate excellent recovery. Intraoperative video highlights key steps of our surgical approach.

CONCLUSION

Optic canal unroofing is in our opinion safe and mandatory when treating tuberculum sellae meningiomas with compression of optic nerve.

Thermal and physical damage in skull base drilling using gas cooling modes: FEM simulation and experimental evaluation

BACKGROUND

Skull base drilling, as a high-risk process, is one of the most important techniques of skull base surgeries.

METHODS

The temperature, thrust force, and torque were calculated using finite element method (FEM) simulation under two conventional cooling models, and internal and external CO₂ cooling modes at four rotational speeds (1000-4000 rpm). The temperatures at the bottom and on the surface of the drilling site were measured experimentally using a thermometer and a thermographic camera, respectively. The results were then compared with FEM results.

RESULTS

The efficiency rates of CO₂ coolants in reducing the maximum temperature, thrust force, and torque were at least 5.0-11.2%, 16.5-33.8%, and 6.9-11.3% higher than conventional cooling modes, respectively. The experimental results indicated that, in contrast to the maximum temperature, temperature durability was 72.7-107.3% higher in the conventional cooling modes than the cooling modes with external CO₂ coolant systems. The cracks and surface defects were less in the CO₂ coolants than the other cooling modes. The maximum temperature after the second and third drillings increased by 17.7 and 26.8%, compared to the first drilling in the conventional cooling modes. On the other hand, the repeated drillings had no impact on the temperature in the CO₂ cooling modes.

CONCLUSION

Skull base drilling with a rotational speed of 2000 rpm in the cooling mode of an external CO₂ coolant, even for repeated drillings, can lead to a skull drilling process with minimum risk of drill bit breakage and thermal and physical damage.

Assessment of variations in sphenoid sinus pneumatization in Indian population: A multidetector computed tomography study

Background and Purpose:

The purpose of our study was to assess the prevalence of variations in the extent of sphenoid pneumatization in the Indian population and compare with existing literature.

Materials and Methods:

This retrospective study included 500 patients who underwent CT of the paranasal sinuses. The multiplanar reformations of paranasal sinus were assessed for the type of pneumatization of the sphenoid sinus and type of clival, lateral recess, lesser wing, and anterior recess extensions.

Results:

The conchal, presellar, incomplete sellar, and complete sellar types comprised 0%, 1.2%, 22.2%, and 76.6% of patients. The extensions of pneumatization subtypes in the study population were clival in 76.6% subjects; lateral recess, lesser wing, and anterior recess in 59.7%, 20.4%, and 20.4% of sinuses, respectively. The pure forms were seen in 25.4% and combined forms in 61% of sinuses. The presellar type (1.2%) was less common and sellar type (98.8%) being common in our population compared to the Caucasian and East Asian population. The sphenoid sinuses were extensively pneumatized in our population compared to the Chinese and Caucasian population, the prevalence being 76.6%, 68%, and 44.5% for clival; 59.7%, 46%, and 28.3% for lateral recess; 20.4%, 32%, and 12% for lesser wing extension, respectively. The pure forms were relatively less common and combined forms being more common compared to the Chinese and Caucasian population in our study.

Conclusion:

The extent of pneumatization of the sphenoid sinus has clinical and surgical implications in sellar and central skull base lesions, and variability in different populations confirms that ethnicity influences the differences in prevalence.

Optic Nerve Mobilization as an Alternative to Anterior Clinoidectomy for Superior Carotid-Ophthalmic Aneurysms: Operative Technique

BACKGROUND

Carotid-ophthalmic aneurysms arise from the internal carotid artery between the distal dural ring and the origin of the posterior communicating artery. The surgical treatment of these aneurysms usually requires anterior clinoidectomy. However, this procedure is not without complications. In the present report, we have described optic nerve mobilization after optic foraminotomy as an alternative to anterior clinoidectomy to clip superior carotid-ophthalmic aneurysms.

METHODS

We have reported the cases of 3 patients with superior carotid-ophthalmic aneurysms who had undergone surgical clipping. Instead of an anterior clinoidectomy, the optic nerve was mobilized after performing optic foraminotomy. The optic canal was carefully unroofed with a 3-mm, high-speed, diamond drill under constant cold saline irrigation to avoid thermal damage to the optic nerve. After incision of the falciform ligament and optic sheath, the optic nerve was gently mobilized with a No. 6 Penfield dissector, facilitating aneurysmal neck exposure and clipping through a widened opticocarotid triangle.

RESULTS

The postoperative course was uneventful for all 3 patients, without any added visual defect. Optic nerve mobilization allowed us to safely widen the opticocarotid triangle and dissect the aneurysm off the optic nerve, without the need for clinoidectomy. This alternative technique permitted, not only early decompression of the optic nerve, but also dissection of the arachnoid between the inferior surface of the optic nerve and the superior surface of the ophthalmic-carotid artery and aneurysm dome.

CONCLUSIONS

Optic nerve mobilization after optic foraminotomy proved to be a safe and relatively easy technique for exposing and treating superior carotid-ophthalmic aneurysms.

[Transcranial microsurgical decompression of the optic canal in surgical treatment of meningiomas of the sellar region]

RATIONALE

When removing the meningiomas of the sellar region, there is always a risk of visual impairment for various reasons, in particular, as a result of traction damage to the optic nerve. Decompression of the optic canal increases nerve mobility during tumor manipulation. In cases of meningioma growing into the canal, its decompression often seems necessary.

AIM

Evaluation of the effectiveness and risks of performing decompression of the optic canal.

MATERIALS AND METHODS

The study included patients with meningiomas of the parasellar location, who underwent surgical treatment at the Burdenko Neurosurgical Center for the period from 2001 to 2017. They were divided into two groups - main and control. The main group consisted of 129 patients who underwent decompression of the optic nerve canals when the tumor was removed. The tumor matrix in this group was most often located in the region of the tuberum sellae, supradiaphragmally, in the region of the anterior clinoid process and the optic canal. In 31 cases, decompression was bilateral - during one operation and using one access in 27 patients; in 4 cases, the decompression of the second canal was delayed for 1.5-3 months after the first operation. 160 decompressions were performed by the intradural and 7 - by extradural methods. During intradural decompression, the roof of the optic canal was resected, and during extradural decompression, the lateral wall of the canal was trephined. The control group consisted of 308 patients who did not undergo canal decompression when the tumor was removed. It included meningiomas with a predominant location of the matrix in the area of the tuberclum and diaphragm of the sella. Tumors in both groups were removed according to the same principles (matrix coagulation, mainly the gradual removal of the tumor, the use of ultrasonic aspirator, a situational decision on the radicality of the operation, etc.). The main difference between operations in these two groups was only canal related algorithms (with or without its trepanation), as well as the probable prevalence of significant lateral tumor growth in cases with canal trepanation. Visual functions in the «primary» group were evaluated before and after operations with trepanation of the canal depending on various factors - the initial state of vision and the radicality of the tumor excision, including removal from the canal. The differences in the postoperative dynamics of vision in the main and control groups were studied. The primary data processing was carried out using the program MSExcel. Secondary statistical processing was carried out using the program Statistica. To assess the statistical significance of differences in the results obtained in the compared patient groups, the Chi-square test was used, and in the case of small groups - the exact Fisher test was applied.

RESULTS

In the main group postoperative vision improvement of varying degrees on the side of trepanation was registered in 36.9% (59 out of 160) cases, no vision changes were found in 36.9% (59 out of 160), and in 26,2% (42 out of 160) the eyesight deteriorated. If preserving vision is attributed to a satisfactory result, then in general the results of these operations should be considered good. A comparative study of the results of removal of meningiomas with trepanation of the canals (main group) or without it (control group) was carried out among patients with the most critical vision situation (visual acuity 0.1 and below, up to only light perception). These groups are comparable in the number of observations - 62 and 73 respectively. The predominance of cases with improved vision in the main group compared with the control group (50.0% versus 38.36%) and a lower incidence of vision impairment (22.58% versus 34.25%) were found. However, the revealed differences are statistically unreliable and make it possible for us to talk only about the trend. The complications associated with trepanation of the canal include mechanical damage to the nerve by the drill. In our series of observations, there was only 1 case of abrasion of the nerve surface with the burr, which did not lead to a significant visual impairment. With the intradural method of trepanation in the area of the medial wall of the canal, the sphenoid sinus may open (in our series, in 34 cases out of 160 trepanations). Immediately closure of these defects was performed by various auto- and allomaterials in various combinations (pericranium, fascia, muscle fragment, hemostatic materials, and fibrin-thrombin glue). A true complication - CSF rhinorrhea liquorrhea developed in only one case, which required transnasal plastic surgery of the CSF fistula using a mucoperiostal flap.

CONCLUSIONS

1. Trepanation of the optic canal in cases of meningiomas of parasellar localization is a relatively safe procedure in the hands of a trained neurosurgeon and does not worsen the results of operations compared with the excision of the same tumors without trepanation of the canal. 2. The literature data and the results of our study make it possible to consider the decompression of the optic canal as an optional, but in many cases, useful option that facilitates the transcranial removal of some meningiomas of the sellar region.

Sphenoid sinuses: pneumatisation and anatomical variants-what the radiologist needs to know and report to avoid intraoperative complications

PURPOSE

Sphenoid sinuses are pneumatised structures, placed in the body of the sphenoid bone, with highly variable morphology. The strict relationships with vascular and nervous structures determine the importance of their anatomical variants in otorhinolaryngology and neurosurgery; a precise understanding of the complex anatomy and anatomic variations of these structures is pivotal for radiological diagnosis of paranasal sinuses pathology and for surgical planning, to avoid potential complications. Our aim is to describe the anatomical variants of sphenoid sinuses, and to help general radiologists and specialists in endoscopic surgery in becoming familiar with these sensitive anatomical structures.

METHODS

A literature search of PubMed and Embase (Elsevier) databases was performed using the keywords "sphenoid sinus" and "anatomy, "sphenoid sinus" and "anatomic variants", "sphenoid sinus", and "anatomic variations".

RESULTS

We described the anatomical variants of the sphenoid sinuses anatomy, according to their size, shape, degree of pneumatisation, protrusion of anatomical structures into their lumen, superimposition of ethmoid cells (Onodi cells), and presence of accessory septations CONCLUSION: The information provided by this study may help in the identification and description of the anatomical variations of the sphenoid sinuses and their relationship to neurovascular structures.

Current decision-making in meningiomas

The incidence of meningiomas is rising and the number of incidental cases is increasing steadily. The efficiency and the safety of each treatment strategy are also improving over time. Therefore the indications to treat meningiomas are constantly changing. The aim of meningioma treatment is keeping the patient fully functional while achieving long-term relief or prevention from problems related to intracranial tumor growth. This chapter reviews the natural history and treatment results and aims to put together the information for the most objective decision-making in treating meningiomas. Factors acting on the treatment decision such as anatomical localization, symptomatology, variations in tumor biology, recurrence status, age and co-morbidities, operative gains, and patient preference are individually discussed.

Transient Complete Unilateral Oculomotor Nerve Palsy following Clipping of Ruptured Anterior Communicating Artery Aneurysm: An Abstruse Phenomenon

Background

Aneurysmal subarachnoid hemorrhage may be associated with different cranial nerve palsies, with oculomotor nerve palsy (ONP) being the most common. ONP is especially associated with posterior communicating artery aneurysms, due to the anatomical proximity of the nerve to the aneurysmal wall. Anterior communicating artery (Acom) aneurysms are very unlikely to produce ONP due to the widely separated anatomical locations of Acom and oculomotor nerve.

Case Description

Here we describe the case of a 60-year-old nondiabetic lady who presented with Acom aneurysmal subarachnoid hemorrhage having a World Federation of Neurosurgical Societies (WFNS) grade I. She underwent an uneventful right pterional craniotomy and clipping of the aneurysm, except for a short period of controlled rupture of the aneurysm. Postoperatively she developed complete ONP on the right side, though her sensorium was preserved. Computed Tomogram and Magnetic Resonance Imaging scans of the brain did not yield any useful information regarding its etiology. She was conservatively managed and kept on regular follow-up. She had a gradual recovery of ONP in the following order: pupillary reaction, ocular movements, and finally ptosis. On postoperative day 61, she had complete recovery from ONP.

Conclusion

We describe a very unusual case of complete ONP following Acom aneurysm clipping and its management by masterly inactivity.

Temperature changes associated with bone drilling in an orbital model: comparison of ultrasonic bone curette and conventional high-speed rotational drill

Purpose: Thermal injury to the optic nerve is a potential complication of bony decompression of the orbital apex. An animal model was used to compare and contrast temperature change while removing orbital bone with ultrasonic and conventional drills. Methods: Two devices, Sonopet ultrasonic bone curette and TPS CORE Micro drill, were used to remove bone from six unpreserved exenterated porcine orbits at fixed distances from the optic canal while temperature was recorded. Increasing irrigation flow rate and decreasing saline temperature with the ultrasonic bone curette were also investigated. Results: The mean change in temperature at the optic canal using the ultrasonic bone curette with 18 ml/min 24°C irrigation was +7.2 ± 3.3°C (range 3.3-12.7°C) at 60 s, and using the rotational drill was +1.7 ± 1.3°C (range 0.1-3.3°C), representing a statistically significant increase above baseline for both drills (p < 0.01 for each). The difference in temperature change between drills was statistically significant (p < 0.01). When irrigation fluid was changed from room temperature saline (24°C), rate 18 ml/min to chilled (10°C) irrigation saline, rate 40 ml/min, the magnitude of the mean temperature increase was reduced by 3.1°C, p < 0.05. Conclusions: In this orbital decompression model, both ultrasonic and rotational drills induced a rise in temperature. This increase was significantly greater with the ultrasonic bone curette, measuring up to 13.7°C. Clinicians should be aware of the potential for temperature spikes when decompressing the orbital apex. Increasing irrigation flow rate and using chilled saline may mitigate increases in temperature.

Cerebrospinal fluid rhinorrhea and otorrhea: A multimodality imaging approach

Cerebrospinal fluid (CSF) leaks are extracranial egress of CSF into the adjacent paranasal sinus or tympanomastoid cavity due to an osteodural defect involving skull base. It can be due to a multitude of causes including accidental or iatrogenic trauma, congenital malformations and spontaneous leaks. Accurate localization of the site of the leak, underlying causes and appropriate therapy is necessary to avoid associated complications. In this paper relevant anatomy, clinical diagnosis, imaging modalities and associated findings are discussed along with a brief mention about management.

Extradural anterior clinoidectomy in the management of parasellar meningiomas: Analysis of 13 years of experience and literature review

BACKGROUND AND AIM

The extradural anterior clinoidectomy (EAC) is a key microsurgical technique that facilitates the resection of tumors located in the parasellar region. There is currently no consensus regarding the execution of the procedure via extradural or intradural nor scientific evidence that supports its routine use. The purpose of this article is to expose our experience in performing EAC as part of the management of the parasellar meningiomas.

MATERIALS AND METHODS

A retrospective analysis of the EAC for parasellar meningioma resection performed in our center between 2003 and 2015 was done. A total of 53 patients were recorded. We analized our series focusing on visual outcomes, resection rates and complications. Through an extensive bibliographic research, we discussed the advantages and disadvantages of the EAC, technical considerations, comparison with the intradural clinoidectomy and its visual impact.

RESULTS

The most frequent tumors were anterior clinoidal meningiomas (33.9%). The most common initial symptoms were decreased visual acuity (45.3%) and headache (22.6%). A gross total resection was achieved in 67.9%, being subtotal in the remaining 32.1%. Regarding the visual deficits 67.9% of the patients presented clinical stability, 22.6% improvement and 9.4% worsening. The degree of tumor resection did not significantly influence post-surgical visual outcomes, either visual acuity (P=.71) or campimetric alterations (P=.53). 24.5% of the patients experienced iiinerve transient paresis and 1.9% permanent. The postoperative cerebrospinal fluid leak rate was 3.8%. Mortality rate was 0%. The mean follow-up was 82.3 months.

CONCLUSIONS

In our experience, EAC is a safe technique that facilitates the resection of the meningiomas located in the parasellar area, helps to achieve early tumor devascularization, reduces the need for retraction of the cerebral parenchyma and could play a positive role in the preservation of visual function and the appearance of tumor recurrences in the anterior clinoid process (ACP).

Operative simulation of anterior clinoidectomy using a rapid prototyping model molded by a three-dimensional printer

BACKGROUND

As the anatomical three-dimensional (3D) positional relationship around the anterior clinoid process (ACP) is complex, experience of many surgeries is necessary to understand anterior clinoidectomy (AC). We prepared a 3D synthetic image from computed tomographic angiography (CTA) and magnetic resonance imaging (MRI) data and a rapid prototyping (RP) model from the imaging data using a 3D printer. The objective of this study was to evaluate anatomical reproduction of the 3D synthetic image and intraosseous region after AC in the RP model. In addition, the usefulness of the RP model for operative simulation was investigated.

METHODS

The subjects were 51 patients who were examined by CTA and MRI before surgery. The size of the ACP, thickness and length of the optic nerve and artery, and intraosseous length after AC were measured in the 3D synthetic image and RP model, and reproducibility in the RP model was evaluated. In addition, 10 neurosurgeons performed AC in the completed RP models to investigate their usefulness for operative simulation.

RESULTS

The RP model reproduced the region in the vicinity of the ACP in the 3D synthetic image, including the intraosseous region, at a high accuracy. In addition, drilling of the RP model was a useful operative simulation method of AC.

CONCLUSIONS

The RP model of the vicinity of ACP, prepared using a 3D printer, showed favorable anatomical reproducibility, including reproduction of the intraosseous region. In addition, it was concluded that this RP model is useful as a surgical education tool for drilling.

Morphometric Analysis of the Middle Clinoid Process Using Maxillofacial Computed Tomography Scans

BACKGROUND

The interest in detailed anatomy of the sella and parasellar regions has resurged recently due to the wide clinical applications of the expanded endoscopic approaches to the skull base. The middle clinoid process (MCP) is a bony structure that can affect wide endoscopic exposure of the sella and parasellar region.

OBJECTIVE

To study and analyze the anatomic variations of the MCP in the general population using computed tomography scans.

METHODS

A total of 150 maxillofacial computed tomography scans were reviewed to characterize the MCP. Only adult patients without intracranial or nasal pathology were included. Measurements were made in the axial and sagittal planes to determine the maximum diameter, length, angulation, and location of the MCP.

RESULTS

The prevalence of the MCP was 30.7% in male and 42.7% in female patients. Of the MCPs, 41.8% were ring forming, whereas 76.4% were pneumatized. Quantitatively, the average axial base diameter was 4.6 ± 1.4 mm, the average sagittal base diameter was 5.0 ± 1.8 mm, the average length was 4.7 ± 1.7 mm, the average midline distance was 5.9 ± 2.3 mm, the average distance from the sellar-clival junction was 10.6 ± 3.3 mm, the average sagittal angle was 91.0 ± 21.1°, and the average axial angle was 45.2 ± 15.5°. A significant increase was found in the prevalence of MCPs in white patients compared with black patients, and a significantly greater midline distance and axial angle were found in male compared with female patients.

CONCLUSION

A clear understanding of the sellar and parasellar anatomy is crucial for successful and safe expanded endoscopic approaches. This study provides a quantitative anatomic characterization of the MCP in the U.S. population with demographic data analysis.

Imaging of Cerebrospinal Fluid Rhinorrhea and Otorrhea

As the obesity epidemic grows in the United States, rhinorrhea and otorrhea from spontaneous cerebrospinal fluid (CSF) leaks secondary to untreated idiopathic intracranial hypertension are increasing in prevalence. CSF rhinorrhea and otorrhea should also be carefully evaluated in posttraumatic and postsurgical settings, because untreated CSF leaks often have serious consequences. The work-up, diagnosis, and characterization of a CSF leak can be complex, often requiring a multimodality approach to optimize surgical planning. This article reviews the causes of CSF leaks, describes the methodology used to work up a suspected leak, and discusses the challenges of making an accurate diagnosis.

Optic nerve mobilization to enhance the exposure of the pituitary stalk during craniopharyngioma resection: early experience

OBJECT Preservation of the pituitary stalk and its vasculature is a key step in good postoperative endocrinological outcome in patients with craniopharyngiomas. In this article, the authors describe the surgical technique of medial optic nerve mobilization for better inspection and preservation of the pituitary stalk. METHODS This operative technique has been applied in 3 patients. Following tumor exposure via a frontolateral approach, the pituitary stalk could be seen partially hidden under the optic nerve and the optic chiasm. The subchiasmatic and opticocarotid spaces were narrow, and tumor dissection from the pituitary stalk under direct vision was not possible. The optic canal was therefore unroofed, the falciform ligament was incised, and the lateral part of the tuberculum sellae was drilled medial to the optic nerve. The optic nerve could be mobilized medially to widen the opticocarotid triangle, which enhanced visualization of and access to the pituitary stalk. RESULTS By using the optic nerve mobilization technique, the tumor could be removed completely, and the pituitary stalk and its vasculature were preserved in all patients. In 2 patients, vision improved after surgery, while in 1 patient it remained normal, as it was before surgery. The hormonal status remained normal after surgery in 2 patients. In the patient with preoperative hormonal deficiencies, improvement occurred early after surgery and hormonal levels were normal after 3 months. No approach-related complications occurred. CONCLUSIONS This early experience shows that this technique is safe and could be used as a complementary step during microsurgery of craniopharyngiomas. It allows for tumor dissection from the pituitary stalk under direct vision. The pituitary stalk can thus be preserved without jeopardizing the optic nerve.

Paraclinoid aneurysms: is there a new endovascular standard?

OBJECTIVES

Paraclinoid aneurysms are challenging lesions to treat with traditional surgical and conventional endovascular techniques despite modern improvements in technique and technology. Flow diversion emerged recently as a promising new therapy that overcomes limitations related to the wide-neck and fusiform morphology, and importantly addresses the underlying diseased parent artery from which the aneurysm arises.

METHODS

We reviewed the current literature regarding the safety and efficacy of flow diversion therapy for treatment of paraclinoid aneurysms.

RESULTS

Early results suggest excellent ability for flow diversion to remodel the diseased parent artery and achieve durable complete angiographic occlusion of the aneurysm with acceptable rates of peri-procedural risk.

DISCUSSION

Flow diversion therapy can achieve durable and high rates of obliteration that surpass traditional methods of management for paraclinoid aneurysms. However, caution is warranted when considering this treatment modality due to several concerning and often-unpredictable complications associated with this technology.

Anterior clinoidectomy

BACKGROUND

The optic nerve within the optic canal, the parophthalmic segment of the carotid artery, and the oculomotor nerve in the superior orbital fissure all lay against the anterior clinoid process. Bone resection uncovers these structures.

METHOD

For extradural resection of the anterior clinoid process and surrounding bone, two key steps are recommended: bony opening of the superior orbital fissure, and transection of the orbitotemporal periosteal fold.

CONCLUSION

Anterior clinoidectomy is technically challenging. Following a sequence of surgical steps to expose clearly-defined surgical landmarks helps to make this procedure simple and safe.

KEY POINTS

• Pterional craniotomy • Complete extradural anterior clinoidectomy • Slit dura (3 mm) to drain cerebrospinal fluid • Peel dura from orbital roof and lateral wall • Bony opening of superior orbital fissure to use it as surgical corridor • Drilling of optic canal • Transection of orbitotemporal periosteal fold • Hollow anterior clinoid process and piece-meal resection • Transection of falciforme ligament to free optic nerve • Replace falciforme ligament by extradural free pericranial flap.