Ultrasonic bone curettage for optic canal unroofing and anterior clinoidectomy. Technical note

Endoscopic transorbital extradural anterior clinoidectomy: A stepwise surgical technique and case series study [SevEN-013]

Background

Anterior clinoidectomy is an important procedure for approaching the central skull base lesions. However, anterior clinoidectomy through the endoscopic transorbital approach (ETOA) still has limitations due to technical difficulties and the structural complexity of the anterior clinoid process (ACP). Therefore, the authors designed a stepwise surgical technique of extradural anterior clinoidectomy through the ETOA. The purpose of this study was to evaluate the feasibility of this technique.

Methods

Anatomical dissections were performed in 6 cadaveric specimens using a neuroendoscope and neuro-navigation system. The extradural anterior clinoidectomy through the ETOA was performed stepwise, and based on the results, this surgical technique was performed in the 7 clinical cases to evaluate its safety and efficiency.

Results

Endoscopic extradural anterior clinoidectomy was successfully performed in all cadaveric specimens and patients using the proposed technique. This 5-step technique enabled detachment of the lesser wing of sphenoid bone from the ACP, safe unroofing of the optic canal, and resection of the optic strut without injuring the optic nerve and internal carotid artery. Since the sequential resection of the 3 supporting roots of the ACP was accomplished safely, anterior clinoidectomy was then successfully performed in all clinical cases. Furthermore, no complications related to the anterior clinoidectomy occurred in any clinical case.

Conclusion

We designed a stepwise surgical technique that allows safe and efficient anterior clinoidectomy through the ETOA. Using this technique, extradural anterior clinoidectomy can be accomplished under direct endoscopic visualization with low morbidity. Since this technique is applicable to the central skull base surgery where anterior clinoidectomy is necessary, it expands the application of the ETOA.

Novel Application of an Ultrasonic Bone Aspirator for Endoscopic Modified Medial Maxillectomy

Background

Endoscopic modified medial maxillectomy (EMMM) is a surgical technique developed to approach maxillary sinus lesions, such as papilloma and postoperative maxillary cyst, while preserving the postoperative nasal morphology and nasal function. In this technique, a diamond burr is used to remove the bone, which may damage adjacent soft tissue. We developed EMMM using an ultrasonic bone aspirator (UBA) instead of a conventional diamond burr. The purpose of this study was to clarify the effectiveness of the UBA in EMMM in comparison to the conventional diamond burr technique in terms of operative time, intraoperative complications, postoperative symptoms, and recurrence.

Methods

The medical records of all patients who underwent EMMM at Toyama University Hospital between June 2014 and December 2021 were reviewed. Patients who met the inclusion criteria were separated into Group 1, in which the UBA was used for EMMM, and Group 2, in which a drill with a diamond burr was used. Data on patient demographics, operation time, frequency of intraoperative complications and postoperative symptoms, and recurrence were statistically compared between the two groups.

Results

There were no significant differences between the two groups in the patient demographic data, operative time, postoperative symptoms, or frequency of recurrence. The frequency of intraoperative damage to adjacent soft tissues was significantly lower in patients who underwent EMMM with the UBA in comparison to those who underwent EMMM with a conventional diamond burr.

Conclusion

The application of the UBA to EMMM can improve surgical safety and facilitate surgical procedures.

Localized Amyloidosis of the Nasal Mucosa: A Case Report and Review of the Literature

Amyloidosis is a disorder of protein folding in which various proteins automatically aggregate into a highly abnormal fibrillar conformation. Amyloidosis is classified into systemic and localized forms depending on whether the abnormal proteins deposited in several different organs or only a single organ. In localized amyloidosis of the head and neck regions, laryngeal amyloidosis is common; however, localized amyloidosis of the nose is extremely rare. We herein report a case of localized amyloidosis of the nose and review the relevant literature on localized sinonasal amyloidosis. A 41-year-old man presented with a history of severe nasal obstruction, which had persisted for two decades. Nasal endoscopy and imaging studies showed extensive thickening of the bilateral nasal mucosa and diffuse submucosal deposition of calcification. After histopathological and systemic examinations, he was diagnosed with localized amyloidosis of the nasal mucosa. Septoplasty and bilateral inferior turbinoplasty, which consisted of mucosal resection using an ultrasonic bone curette, was performed and his symptoms markedly improved. Localized sinonasal amyloidosis has a good prognosis and surgical resection should be selected as a first-line treatment; however, clinicians should recognize the high probability of recurrence.

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.

Comparison of tendon-bone healing between a newly developed ultrasound device and the conventional metallic drill in a rabbit MCL reconstruction model

BACKGROUND

Ligament reconstructive surgeries demand tunnel creation using an over-drilling technique, though this technique has some problems such as metallic particle liberation or difficulties in tunnel creation other than circular cross-section. Recently, a new ultrasound (US) device for bone excavation to overcome these problems was developed. This study aimed to compare the tendon-bone healing in tunnels created using the new US device to that created using the conventional drill in a rabbit model.

METHODS

A total of 72 rabbits underwent a reconstruction for the anterior half of the medial collateral ligament (MCL) using a half of the patellar tendon. For the femoral tunnel creation, a new US device was used in 36 rabbits (US group), while a conventional metallic drill was used for the remaining 36 rabbits (DR group). At 4, 8, and 12 weeks postoperatively, biomechanical (n = 10) and histological (n = 2) evaluations were performed.

RESULTS

The ultimate failure load was almost equivalent between the US and DR groups at each period (US/DR; 4 weeks, 50.0 ± 12.8 N/43.4 ± 18.9 N, p = 0.62; 8 weeks, 78.6 ± 11.5 N/77.3 ± 29.9 N, p = 0.92; and 12 weeks: 98.9 ± 33.5 N/102.2 ± 38.3 N, p = 0.80). Pull-out failure from the femoral tunnel was only observed in two rabbits in the US group and one rabbit in the DR group at 4 weeks postoperatively. At 8 and 12 weeks, all specimens had a mid-substance tear. The collagen fiber continuity between tendon and bone occurred 8 weeks postoperatively in both groups and no histological difference was recognized throughout the evaluation period.

CONCLUSIONS

The tunnels created using the new US device and the conventional drill had equivalent biomechanical and histological features in tendon-bone healing. The bone excavation technology by the new US device may be applicable in ligament reconstructive surgeries.

Extradural anterior clinoidectomy through endoscopic transorbital approach: laboratory investigation for surgical perspective

BACKGROUND

The endoscopic transorbital approach (eTOA) is a new mini-invasive procedure used to explore different areas of the skull base. Authors propose an extradural anterior clinoidectomy (AC) through this corridor, defining the anatomical landmarks of the anterior clinoid process (ACP) projection onto the posterior orbit wall and the technical feasibility of this approach. We describe the exposure of the opticocarotid region and the surgical freedom and the angles of attack obtained with this novel approach.

METHODS

Five cadaver heads underwent an eTOA at the Laboratory of Surgical Neuroanatomy of the University of Barcelona. A step-by-step description of the extradural endoscopic transorbital clinoidectomy was provided. A volumetric analysis of the morphometrics characteristics of the sphenoid wings was evaluated before and after dissection using CT scans. Pterional approach was performed to ascertain ACP removal.

RESULTS

In all the specimens, it was possible to resect the ACP endo-orbitally aiming an optimal optic canal (OC) unroofing. The surface of the triangle corresponding to the ACP projection onto the posterior orbit wall was 0.42 ± 0.20 cm². The drilled area to perform the extradural clinoidectomy via eTOA was 3.11 ± 2.27 cm², and the volume of bone removal corresponding to the greater sphenoid wing (GSW) and lesser sphenoid wing (LSW) was 2.55 ± 1.41 and 0.26 ± 0.18 cm³ respectively. The area of surgical freedom provided by the eTOA was (3.11 ± 2.27cm²), and the angles of attack were 21.39 ± 9.13° in the horizontal axel and 30.63 ± 18.51° in the vertical.

CONCLUSIONS

The described extradural anterior clinoidectomy by eTOA uses specific landmarks to localize the ACP on the posterior orbit wall. Resection of the ACP is a technically feasible approach, achieving the main goals of any clinoidectomy.

Technical note: rectangular femoral tunnel for anterior cruciate ligament reconstruction using a new ultrasonic device: a feasibility study

PURPOSE

The goal of this preliminary report was to show the use of novel Ultrasound (US) technology for anterior cruciate ligament (ACL) reconstruction surgery and evaluate its feasibility for the creation of a rectangular femoral bone tunnel during an arthroscopic procedure in a human cadaver model.

METHODS

Two fresh frozen human cadaver knees were prepared for arthroscopic rectangular femoral tunnel completion using a prototype US device (OLYMPUS EUROPA SE & CO. KG). The desired rectangular femoral tunnel was intended to be located in the femoral anatomical ACL footprint. Its tunnel aperture was planned at 10 × 5 mm and a depth of 20 mm should be achieved. For one knee, the rectangular femoral tunnel was realized without a specific cutting guide and for the other with a 10 × 5 mm guide. One experienced orthopedic surgeon performed the two procedures consecutively. The time for femoral tunnel completion was evaluated. CT scans with subsequent three-dimensional image reconstructions were performed in order to evaluate tunnel placement and configuration.

RESULTS

In the two human cadaver models the two 10 × 5x20mm rectangular femoral tunnels were successfully completed and located in the femoral anatomical ACL footprint without adverse events. The time for femoral tunnel completion was 14 min 35 s for the procedure without the guide and 4 min 20 s with the guide.

CONCLUSION

US technology can be used for the creation of a rectangular femoral bone tunnel during an arthroscopic ACL reconstruction procedure. The use of a specific cutting guide can reduce the time for femoral tunnel completion. Additional experience will further reduce the time of the procedure.

A 270-Degree Decompression of Optic Nerve in Refractory Idiopathic Intracranial Hypertension Using an Ultrasonic Aspirator - A Prospective Institutional Study

Background

Although the nonsurgical treatment for idiopathic intracranial hypertension (IIH) involves weight loss, diuretics, and steroids, surgical intervention is required if there is a worsening of symptoms or visual deterioration.

Objective

To determine the efficacy and complications of transcranial optic nerve sheath fenestration (ONSF) using an ultrasonic aspirator as an adjunct in the treatment of refractory IIH.

Material and Methods

This prospective study included all patients with medically refractory IIH with visual deterioration from November 2017 to June 2019. Pterional craniotomy was followed by extradural clinoidectomy and optic foramen bony decompression using an ultrasonic aspirator. All the cases were followed up for changes in visual acuity and field and surgical outcomes.

Results

A total of 21 consecutive patients who underwent ONSF in the study period were included for analysis. Improvement in visual acuity was noted in 19/21 (90.47%) patients. Improvement in visual fields was noted in 17/21 (80.95%). Headache improved in 66.67% of patients. Improvement in the fundus picture was noted in 90.47%. Symptoms < 6 months showed better results compared to > 6 months symptom, although statistically nonsignificant (P = 0.2556). A 270-degree optic canal decompression was achieved in all the cases.

Conclusion

Transcranial optic nerve sheath decompression with a bone ultrasonic aspirator is a safe and direct decompression of the optic nerve in malignant/refractory cases of IIH.

Impact of Anterior Clinoidectomy on Visual Function After Paraclinoid Carotid Artery Aneurysm Surgery: Power-Drill Versus No-Drill Technique

BACKGROUND

Few studies have attempted to make a direct comparison of the risk of visual impairment following extradural anterior clinoidectomy (EAC) with and without the use of a power drill.

OBJECTIVE

To evaluate postoperative visual outcomes between groups of patients with paraclinoid carotid artery aneurysms (PCAAs) who underwent surgical clipping with and without the use of a power drill during EAC.

METHODS

Between January 2010 and November 2019, 90 patients, 7 with ruptured and 83 with unruptured PCAAs, underwent clipping surgery at our hospital. The authors retrospectively analyzed postoperative visual complications from the medical records of these patients.

RESULTS

Among the 85 patients (excluding 3 patients with disturbance of consciousness caused by subarachnoid hemorrhage and 2 patients with preoperative visual disturbance) evaluated, EAC was conducted using a power drill in 64 patients and using a microrongeur in 21 patients. Permanent postoperative visual impairment developed in 14 (21.9%) patients in the drill group: 9 patients had ipsilateral lower nasal quadrant hemianopsia (ILNQH) and 5 patients had ipsilateral visual acuity reduction. Transient ILNQH developed in only 1 patient in the no-drill group. The incidence of permanent postoperative visual impairments was significantly lower in the no-drill group than in the drill group (P = .020). Seventeen (26.6%) patients developed transient oculomotor nerve palsy in the drill group, while no patients developed oculomotor nerve palsy in the no-drill group.

CONCLUSION

EAC using a microrongeur versus a power drill significantly improved visual outcomes after clipping surgery for PCAAs.

Tailored Anterior Clinoidectomy: Beyond the Intradural and Extradural Concepts

Anterior clinoidectomy (AC) is a key microsurgical step for the safe and successful management of parasellar pathologies that involve the anterior clinoid process (ACP) and the optic canal. Traditionally, extra and intradural ACs are performed separately according to the surgeon's experience or preference. The objective is to present and discuss the tailored AC concept through illustrative cases. We conducted a retrospective record review of three patients who underwent AC as a surgical step for the treatment of parasellar pathologies that involve the ACP and optic canal. A review of the relevant literature on AC was performed in the PubMed, LILACS, and SciELO databases.

In all three cases, the pterional craniotomy was the preferred approach for AC. Case 1, a 47-year-old female patient with type III anterior clinoidal meningioma, underwent a tailored intradural technique (optic canal unroofing) with total tumor resection and complete visual recovery. Case 2, a 63-year-old female patient with a complex type II anterior clinoidal meningioma with extensive hyperostosis of the ACP, underwent a hybrid AC technique with complete removal of the tumor and visual improvement. Case 3, a 62-year-old female, underwent a tailored intradural AC for clipping an incidental carotid-ophthalmic aneurysm.

Tailored AC aims to provide adequate exposure with less risk of neurovascular injury, allowing enough space to safely treat parasellar lesions. The type, size, and location of the lesion, as well as the surgeon’s experience, should always be considered for surgical planning.

[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.

Primary lumbar decompression using ultrasonic bone curette compared to conventional technique

PURPOSE

The ultrasonic bone curette (Bone Scalpel) is a novel technique in neurosurgery for bony dissection. This study aimed to evaluate its use against conventional techniques for primary lumbar decompression.

MATERIALS AND METHODS

This study was a retrospective cohort comparison, using Spine Tango Registry data. All patients undergoing a primary procedure for lumbar decompression secondary to degenerative disease during a 2-year period (2014-2016) were identified, split into age and gender matched cohorts utilising either bone scalpel or conventional techniques intra-operatively.

RESULTS

Ninety-three patients were identified within each cohort, which did not differ significantly in terms of age, gender, BMI, number of operative vertebral levels or seniority of the principal surgeon. The incidence of intra-operative blood loss >100 ml was significantly reduced within the bone scalpel cohort (16.1% bone scalpel, 34.4% conventional, p = 0.04). There was no difference in the incidence of iatrogenic dural breach (9.7% bone scalpel, 16.1% conventional, p = 0.27). There was no significant difference in pre-operative Core Outcomes Measures Index (COMI) between the cohorts (7.91 bone scalpel, 8.02 conventional, p = 0.67) and both cohorts demonstrated a significant reduction in mean COMI at 24 months (bone scalpel p = 0.004, conventional p = <0.001). No difference in mean COMI existed between either cohort at any point across the 24-month post-operative period (p = 0.18).

CONCLUSIONS

The use of ultrasonic bone curette for primary lumbar decompression is associated with reduced intra-operative blood loss compared to conventional techniques, alongside a comparable safety profile and equivalent patient reported outcomes.

Deep Lateral Wall Partial Rim-Sparing Orbital Decompression with Ultrasonic Bone Removal for Treatment of Thyroid-Related Orbitopathy

Purpose

To describe the results of thyroid-related orbitopathy (TRO) treated by ultrasonic deep lateral wall bony decompression with partial rim sparing (DLW-PRS).

Methods

A review was carried out, from January 2015 to September 2017, of all patients treated with ultrasonic DLW-PRS decompression using a SONOPET® (Stryker, Kalamazoo, MI, USA) ultrasonic aspirator, using a lateral, small triangle flap incision for access. The primary outcome was the change in proptosis (measured by the difference in Hertel exophthalmometry measurements). Other secondary outcomes were changes in visual acuity (VA) (using Snellen scale, decimal fraction), presence of lagophthalmos, eyelid retraction (measured by upper eyelid margin distance to the corneal reflex (MRD₁) and lower eyelid margin distance to the corneal reflex (MRD₂), and presence of exposure keratopathy).

Results

A total of 58 orbital decompressions in 35 patients were reviewed, with 23 patients (65.7%) having bilateral decompressions. There was a female preponderance with 26 patients (74.2%), and the mean age ± standard deviation was 52.6 ± 13.9 years. Mean proptosis was 24.51 ± 1.76 mm preoperatively, reduced to 19.61 ± 1.27 mm in final follow-up. The mean reduction was 4.9 ± 1.54 mm. VA improved from 0.8 ± 0.14 to 0.9 ± 0.12, p=0.039. 5 of 13 patients (38.4%) with preoperative diplopia reported improvement or complete resolution after surgery. MRD₁ was reduced from 5.25 ± 0.88 mm to 4.49 ± 0.7 mm. MRD₂ was also reduced from 6.3 ± 0.88 mm to 5.0 ± 0.17 mm. Presence of lagophthalmos was reduced from 35 eyes (60.3%) to five (8.6%); the presence of epiphora was also reduced from 20 patients (57.1%) to 3 (8.5%) following decompression. Complications of the surgery included zygomatic hypoaesthesia in 14 (40%) patients in the early postoperative period and chewing alterations in 10 (28.5%) of the patients. All of these complications were resolved at the 6-month follow-up visit. We noted no surgical complications such as ocular or soft tissue damage, infection, inflammation, or visual loss.

Conclusions

The SONOPET® ultrasonic bone curette can be used safely and effectively for DLW orbital decompression surgery. The main benefits were good visualization and handling of tissues and speed and ease of use of the equipment. This trial is registered with ClinicalTrials.gov identifier: NCT04025034.

Anterior clinoidectomy using an extradural and intradural 2-step hybrid technique

In Brief: The authors found a practical intraoperative landmark to localize the optic strut during anterior clinoidectomy and used it as the basis for performing anterior clinoidectomy in two steps: extradural phase and intradural phase. This anatomically based technique can increase the safety of anterior clinoidectomy by providing easily identifiable landmarks and reducing intradural bone drilling, which could put the adjacent neurovauscular structures at risk.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Characteristics of ultrasound device: a new technology for bone curettage and excavation

Background

Ultrasonic (US) devices are used in laparoscopic, dental, and spinal surgeries, while it is difficult to use for the joint under irrigation and perfusion solutions due to lack of power. A new US device is developed with greater voltage improvement and has been implemented in the arthroscopic field. The aim is to compare the characteristics of the US devices with the conventional ones in water.

Methods

Twenty bone blocks from the porcine femur were settled in a holder in water. A 4.0 mm diameter abrader burr moved 15 mm along the long axis of the bone block in ten blocks for three times. A 4.3 mm wide curette blade powered by ultrasonic vibration was moved in the same manner in the other ten blocks. The gutter shape, including the gutter depth and the bottom angle of the gutter, and the curetted area ratio of the gutter were assessed.

Forty bones blocks from the porcine femurs were clamped with a holder in water, while the cortical bone surface must be located on the side. A 5 mm diameter drill excavated the bone along the previously-inserted guide wire to the 15 mm depth for twenty blocks. Next, the US excavation probe of 5x4mm rectangular shape was moved to the same depth in the other twenty blocks. Each ten block was cut in half along the bone tunnel and was assessed the surface roughness at three area, while the cross-sectional area (CSA) of the tunnel were measured and the ratio of the measured CSA was calculated based on an expected CSA in the remaining ten blocks for each device.

Results

The depth of curettage and bottom angle were significantly smaller with the US device than with the abrader burr at all planes, while the curetted area ratio created by each device was mostly equal to the other. Surface roughness was similar in two evacuating devices except one area. CSA ratio with the US excavation device was significantly smaller than that with the drill.

Conclusion

US curettage has an advantage to flatly curette bone surfaces, while a bone tunnel can be accurately created with the US device.

Novel approach using ultrasonic bone curettage and transoral robotic surgery for en bloc resection of cervical spine chordoma: case report

Chordomas are rare, locally aggressive neoplasms that develop from remnants of the notochord. The typical approach to chordomas of the clivus and axial cervical spine often limits successful en bloc resection. In this case report, authors describe the first-documented transoral approach using both transoral robotic surgery (TORS) for exposure and the Sonopet bone scalpel under navigational guidance to achieve en bloc resection of a cervical chordoma. This 27-year-old man had no significant past medical history (Charlson Comorbidity Index 0). During a trauma workup following a motor vehicle collision, a CT of the patient's cervical spine demonstrated an incidental 2.2-cm lesion situated along the posterior aspect of the C2 vertebral body. Postoperative imaging showed successful en bloc resection with adequate placement of hardware, and the pathology report demonstrated negative resection margins. The patient tolerated the procedure well, and because of the successful en bloc resection, radiation has been deferred. At 7 months postoperatively, the patient returned to work in New York City. Contrasted MRI at 15 months postoperatively showed the patient to be disease free. This approach offers a promising way forward in the treatment of these complex tumors.

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.

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).

Quantitative analysis of variable extent of anterior clinoidectomy with intradural and extradural approaches: 3-dimensional analysis and cadaver dissection

BACKGROUND

Drilling of the anterior clinoid process (ACP) is an integral component of surgical approaches for central and paracentral skull base lesions. The technique to drill ACP has evolved from pure intradural to extradural and combined techniques.

OBJECTIVE

To describe the computerized morphometric evaluation of exposure of optic nerve and internal carotid artery with proposed tailored intradural (IDAC) and complete extradural (EDAC) anterior clinoidectomy.

METHODS

We describe a morphometric subdivision of ACP into 4 quadrangles and 1 triangle on the basis of fixed bony landmarks. Computerized volumetric analysis with 3-dimensional laser scanning of dry-drilled bones for respective tailored IDAC and EDAC was performed. Both approaches were compared for the area and length of the optic nerve and internal carotid artery. Five cadaver heads were dissected on alternate sides with intradural and extradural techniques to evaluate exposure, surgical freedom, and angulation of approach.

RESULTS

Complete anterior clinoidectomy provides a 2.5-times larger area and 2.7-times larger volume of ACP. Complete clinoidectomy deroofed the optic nerve to an equal extent as by proposed the partial tailored clinoidectomy approach. Tailored IDAC exposes only the distal dural ring, whereas complete EDAC exposes both the proximal and distal dural rings with complete exposure of the carotid cave.

CONCLUSION

Quantitative comparative evaluation provides details of exposure and surgical ease with both techniques. We promote hybrid/EDAC technique for vascular pathologies because of better anatomic orientation. Extradural clinoidectomy is the preferred technique for midline cranial neoplasia. An awareness of different variations of clinoidectomy can prevent dependency on any particular approach and facilitate flexibility.

Application of ultrasonic bone curette in endoscopic endonasal skull base surgery: technical note

Background Endoscopic endonasal surgery (EES) of the skull base often requires extensive bone work in proximity to critical neurovascular structures. Objective To demonstrate the application of an ultrasonic bone curette during EES. Methods Ten patients with skull base lesions underwent EES from September 2011 to April 2012 at the University of Pittsburgh Medical Center. Most of the bone work was done with high-speed drill and rongeurs. The ultrasonic curette was used to remove specific structures. Results All the patients were submitted to fully endoscopic endonasal procedures and had critical bony structures removed with the ultrasonic bone curette. Two patients with degenerative spine diseases underwent odontoid process removal. Five patients with clival and petroclival tumors underwent posterior clinoid removal. Two patients with anterior fossa tumors underwent crista galli removal. One patient underwent unilateral optic nerve decompression. No mechanical or heat injury resulted from the ultrasonic curette. The surrounding neurovascular structures and soft tissue were preserved in all cases. Conclusion In selected EES, the ultrasonic bone curette was successfully used to remove loose pieces of bone in narrow corridors, adjacent to neurovascular structures, and it has advantages to high-speed drills in these specific situations.

Penetration of the optic nerve and falciform ligament by an internal carotid artery-ophthalmic artery aneurysm: case report

We report a case of an internal carotid artery (ICA)-ophthalmic artery aneurysm with penetration of the optic nerve. In addition, this case penetrated the falciform ligament, which severely disturbed optic canal unroofing during surgery. This is the first reported case in which penetration of the optic nerve and falciform ligament has been shown. To remove the anterior clinoid process in this case, the ultrasonic bone curette was a useful tool.

How I do it : anterior clinoidectomy and optic canal unroofing for microneurosurgical management of ophthalmic segment aneurysms

BACKGROUND

Power drilling commonly used for anterior clinoidectomy and optic canal unroofing can result in thermal injury to the optic nerve.

METHODS

The authors describe an intradural "limited drill" technique of anterior clinoidectomy and optic canal unroofing for microneurosurgical management of ophthalmic segment aneurysms, where optic canal unroofing is done with 1 mm Kerrison punch and the use of the power drill is restricted to anterior clinoidectomy to avoid thermal injury to the optic nerve. The optic nerve, internal carotid artery (ICA), and aneurysm are covered with wet gelfoam pieces to prevent any inadvertent contact with the drill.

CONCLUSION

"Limited drill technique" is a safe and effective technique of anterior clinoidectomy and optic canal unroofing.

KEY POINTS

• Anterior clinoidectomy and optic canal unroofing is an important skull base technique required for safe clipping of the majority of ophthalmic segment aneurysms • Power drilling commonly used for optic canal unroofing can cause thermal injury to optic nerve • More than 2 mm free space is available around the optic nerve in the optic canal • Foot plate of 1 mm Kerrison punch can be safely introduced within a normal optic canal without causing mechanical injury to the optic nerve • Reflection of posteriorly based dural flap acts as a dural barrier, preventing direct contact of drill bit to optic nerve, internal carotid artery and aneurysm during drilling • Entanglement of cottonoids to rotating drill bit is a major problem in intradural anterior clinoidectomy • Wet gelfoam pieces do not get entangled to the rotating drill bit • Structures surrounding the area of drilling can be covered with wet gel foam pieces to prevent direct contact of the drill to neurovascular structures • Opened cisterns can be covered with wet gelfoam pieces during drilling to prevent deposition of bone dust in the subarachnoid space • "Limited drill technique" of anterior clinoidectomy and optic canal unroofing is a safe and effective technique for the exposure of ophthalmic segment aneurysms.

Safety of spinal decompression using an ultrasonic bone curette compared with a high-speed drill: outcomes in 337 patients

Object

Unintended durotomies are a common complication of spine surgery and are often correlated with increased postoperative morbidity. Recently, ultrasonic bone curettes have been introduced in spine surgery as a possible alternative to the conventional high-speed drill, offering the potential for greater bone-cutting precision and less damage to surrounding soft tissues. To date, however, few studies have investigated the safety and efficacy of the ultrasonic bone curette in reducing the rates of incidental durotomy compared with the high-speed drill.

Methods

The authors retrospectively reviewed the records of 337 consecutive patients who underwent posterior cervical or thoracic decompression at a single institution between January 2009 and September 2011. Preoperative pathologies, the location and extent of spinal decompression, and the use of an ultrasonic bone curette versus the high-speed drill were noted. The rates of incidental durotomy, as well as hospital length of stay (LOS) and perioperative outcomes, were compared between patients who were treated using the ultrasonic bone curette and those treated using a high-speed drill.

Results

Among 88 patients who were treated using an ultrasonic bone curette and 249 who were treated using a high-speed drill, 5 (5.7%) and 9 (3.6%) patients had an unintentional durotomy, respectively. This finding was not statistically significant (p = 0.40). No patients in either cohort experienced statistically higher rates of perioperative complications, although patients treated using an ultrasonic bone curette tended to have a longer hospital LOS. This difference may be attributed to the fact that this series contained a statistically higher number of metastatic tumor cases (p < 0.0001) in the ultrasonic bone curette cohort, likely increasing the LOS for that patient population. In 13 patients, the dural defect was repaired intraoperatively. No patients who experienced an incidental durotomy had new-onset or permanent neurological deficits postoperatively.

Conclusions

The safety and efficacy of ultrasonic bone curettes in spine surgery has not been well established. This study shows that the ultrasonic bone curette has a similar safety profile compared with the high-speed drill, although both are capable of causing iatrogenic dural tears during spine surgery.

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

BACKGROUND

Skull base drilling is a necessary and important element of skull base surgery; however, drilling around vulnerable neurovascular structures has certain risks. We aimed to assess the frequency of complications related to drilling the anterior skull base in the area of the optic nerve (ON) and internal carotid artery (ICA), in a large series of patients.

METHODS

We included anterior skull base surgeries performed from 2000 to 2012 that demanded unroofing of the optic canal, with extra- or intradural clinoidectomy and/or drilling of the clinoidal process and lateral aspect of the tuberculum sella. Data was retrieved from a prospective database and supplementary retrospective file review. Our IRB waived the requirement for informed consent. The nature and location of pathology, clinical presentation, surgical techniques, surgical morbidity and mortality, pre- and postoperative vision, and neurological outcomes were reviewed.

RESULTS

There were 205 surgeries, including 22 procedures with bilateral optic canal unroofing (227 optic canals unroofed). There was no mortality, drilling-related vascular damage, or brain trauma. Complications possibly related to drilling included CSF leak (6 patients, 2.9 %), new ipsilateral blindness (3 patients, 1.5 %), visual deterioration (3 patients, 1.5 %), and transient oculomotor palsy (5 patients, 2.4 %). In all patients with new neuropathies, the optic and oculomotor nerves were manipulated during tumor removal; thus, new deficits could have resulted from drilling, or tumor dissection, or both.

CONCLUSION

Drilling of the clinoid process and tuberculum sella, and optic canal unroofing are important surgical techniques, which may be performed relatively safely by a skilled neurosurgeon.

Endoscopic extradural anterior clinoidectomy via supraorbital keyhole: a cadaveric study

BACKGROUND

Anterior clinoidectomy is an essential preliminary step for parasellar and pericavernous sinus surgery. Endoscopy is a widely accepted modality for neurosurgical strategies and is becoming more important in treating conditions involving the cranial base.

OBJECTIVE

To determine the feasibility of endoscopic extradural anterior clinoidectomy via the supraorbital keyhole.

METHODS

Eight fresh cadaver heads were studied using 4-mm, 0- and 30-degree rigid endoscopes to perform endoscopic extradural anterior clinoidectomy. We also evaluated a bony landmark for this technique in 36 dry craniums.

RESULTS

An endoscope was introduced into the extradural space created via a supraorbital keyhole craniotomy. The periorbita and the duplication of the dura extending to the temporal lobe dura and periorbita were exposed by drilling. Anterior clinoidectomy proceeded using a diamond drill under endoscopic visualization without a dural incision. A submerged view with continuous irrigation through an endoscopic sheath maintained clear visibility while drilling. A small bony eminence at the transition between the sphenoid ridge and the anterior clinoid process, which is an anatomic landmark for endoscopic extradural anterior clinoidectomy, was identified in 57.4% of 36 adult dry craniums.

CONCLUSION

The endoscopic extradural procedure can accomplish reliable anterior clinoidectomy under superb endoscopic visualization. This method would be applicable to parasellar and cavernous sinus surgery combined with keyhole or conventional craniotomy.

Complications of anterior clinoidectomy through lateral supraorbital approach

OBJECTIVE

We reviewed the surgical complications from our recent experience in vascular and tumor patients who underwent anterior clinoidectomy through the lateral supraorbital (LSO) approach.

METHODS

Between June 2007 and January 2011, a total of 82 patients with neoplastic and vascular lesions underwent anterior clinoidectomy by the senior author (J.H.) through the LSO approach. We analyzed the operative videos paying particular attention to the surgical technique used for removal of the anterior clinoid process (ACP) and compared the microsurgical nuances to postoperative complications related to anterior clinoidectomy.

RESULTS

Forty-five patients were treated for aneurysms; 35 patients for intraorbital, parasellar, and suprasellar tumors; and 2 patients for carotid-cavernous fistulas. Intradural anterior clinoidectomy was performed in 67 (82%) cases; in 15 (18%) cases an extradural approach was used. In 51 (62%) cases, ACP was removed completely, whereas in the remaining 31 (38%) a tailored anterior clinoidectomy was performed. Four (5%) patients had new postoperative visual deficits and 3 (4%) experienced a worsening of preoperative visual deficits. Twelve (15%) patients improved their preoperative visual deficits after intradural anterior clinoidectomy. Ultrasonic bone device is a useful tool but may damage the optic nerve when performing anterior clinoidectomy. There was no mortality in our series.

CONCLUSION

Anterior clinoidectomy can be performed through an LSO approach with a safety profile that is comparable to other approaches. Ultrasonic bone dissector is a useful tool but may lead to injury of the optic nerve and should be used very carefully in its vicinity.

Anterior clinoidectomy: Description of an alternative hybrid method and a review of the current techniques with an emphasis on complication avoidance

BACKGROUND

Anterior clinoidectomy is a difficult but important part of surgery for a variety of parasellar, proximal carotid and central skull base pathologies. First developed intradurally nearly 60 years ago, the promotion of an extradural technique decades later offered an approach with a different set of difficulties, risks and benefits. Many recent studies have demonstrated that there is no consensus about the "correct side" of the dura from which to remove the anterior clinoid process in a number of pathologies. Here, we review and compare the current techniques for intra- and extradural clinoidectomy and describe a hybrid alternative technique.

METHODS

We used a hybrid method to potentially engage the advantages of the intradural and extradural techniques. The hybrid method starts with an extradural sphenoid wing osteotomy to the level of the superior orbital fissure (SOF). The dura is then incised parallel to the sphenoid wing lateral to the SOF, and the need for further bony removal, including clinoidectomy, is assessed after gentle elevation of the frontal lobe and release of cerebrospinal fluid through opening the optico-carotid cisterns and inspection of the pathology in relation to the clinoid. Sylvian fissure may be dissected to relieve retraction on the frontal lobe.

RESULTS

The hybrid method allows an early identification of the optic nerve and its protection during clinoidectomy. The operator leaves the dura medial to the SOF intact and the clionoidectomy proceeds in an extradural fashion while intradural inspection periodically is performed to assess the extent of necessary extradural bony removal.

CONCLUSION

The hybrid method theoretically can be used as a versatile method under some circumstances. Cutting the dura along the sphenoid wing will prevent the dural layers from obscuring the clinoid and offers intradural visualization to monitor the lesion and potentially tailor bony removal.

The avoidance of microsurgical complications in the extradural anterior clinoidectomy to paraclinoid aneurysms

OBJECTIVE

Paraclinoid segment internal carotid artery (ICA) aneurysms have historically been a technical challenge for neurovascular surgeons. The development of microsurgical approach, advances in surgical techniques, and endovascular procedures have improved the outcome for paraclinoid aneurysms. However, many authors have reported high complication rates from microsurgical treatments. Therefore, the present study reviews the microsurgical complications of the extradural anterior clinoidectomy for treating paraclinoid aneurysms and investigates the prevention and management of observed complications.

METHODS

Between January 2004 and April 2008, 22 patients with 24 paraclinoid aneurysms underwent microsurgical direct clipping by a cerebrovascular team at a regional neurosurgical center. Microsurgery was performed via an ipsilateral pterional approach with extradural anterior clinoidectomy. We retrospectively reviewed patients' medical charts, office records, radiographic studies, and operative records.

RESULTS

IN OUR SERIES, THE CLINICAL OUTCOMES AFTER AN IPSILATERAL PTERIONAL APPROACH WITH EXTRADURAL ANTERIOR CLINOIDECTOMY FOR PARACLINOID ANEURYSMS WERE EXCELLENT OR GOOD (GLASGOWS OUTCOME SCALE : GOS 5 or 4) in 87.5% of cases. The microsurgical complications related directly to the extradural anterior clinoidectomy included transient cranial nerve palsy (6), cerebrospinal fluid leak (1), worsened change in vision (1), unplanned ICA occlusion (1), and epidural hematoma (1). Only one of the complications resulted in permanent morbidity (4.2%), and none resulted in death.

CONCLUSION

Although surgical complications are still reported to occur more frequently for the treatment of paraclinoid aneurysms, the permanent morbidity and mortality resulting from a extradural anterior clinoidectomy in our series were lower than previously reported. Precise anatomical knowledge combined with several microsurgical tactics can help to achieve good outcomes with minimal complications.

Bone removal with a new ultrasonic bone curette during endoscopic endonasal approach to the sellar-suprasellar area: technical note

BACKGROUND

Accessing intradural lesions via an extended endoscopic endonasal approach requires a relatively large bony removal over the skull base.

OBJECTIVE

We describe the Sonopet ultrasonic bone curette with a new dedicated endonasal hand-piece.

MATERIALS AND METHODS

We used this ancillary device in 27 nonconsecutive endonasal procedures for different skull base lesions (18 standard pituitary operations and 9 extended approaches for either meningiomas or craniopharyngiomas).

RESULTS

The ultrasonic bone curette with endonasal hand-piece was easy to use and effective during the removal of the bone covering or when close to the carotid and optic prominences, as well as in preserving the integrity of the superior intercavernous sinus. In only 1 case was small tearing of the dura mater observed during the bony removal. No cases of injury to the major neurovascular structures occurred.

CONCLUSION

The Sonopet ultrasonic bone curette is a useful tool during endoscopic endonasal skull base surgery.

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.

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.