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

Anatomical features of the sphenoid ridge in the pediatric population

PURPOSE

To describe the relation of the sphenoid ridge (SR) with the surrounding anatomical structures in healthy children when approaching the anterior and middle fossae.

METHODS

Computed tomography of 180 pediatric patients (90 males / 90 females), aged 1-18 years were included the study. The size of the lesser wing (LW) and the distances of the LW to certain landmarks were measured.

RESULTS

The LW length was 28.48 ± 8.15 mm. The LW widths at the midline and the midpoint and lateral point of the SR were 7.78 ± 1.74 mm, 2.84 ± 0.81 mm, and 1.91 ± 0.64 mm, respectively. The distance between the midpoint of the SR and the crista galli was 28.22 ± 5.56 mm, and the distance between the crista alaris and internal auditory meatus was 51.73 ± 5.79 mm. The linear function was calculated as y = 18.748 + 1.024 × age for SR length, y = 6.046 + 0.182 × age for the midline width of SR, y = 2.367 + 0.050 × age for the midpoint width of SR, y = 1.249 + 0.069 × age for the crista alaris width, y = 21.727 + 0.683 × age for the distance between the SR midpoint and the crista galli, and y = 43.614 + 0.855 × age for the distance between the crista alaris and internal auditory meatus.

CONCLUSION

All measured parameters increased irregularly with advancing age. Furthermore, our regression equations representing the growth dynamics of SR may be used to estimate these parameters.

'What's in a name', a systematic review of the pterional craniotomy for aneurysm surgery and its many modifications with a proposal for simplified nomenclature

BACKGROUND

The pterional or frontosphenotemporal craniotomy has stood the test of time and continues to be a commonly used method of managing a variety of neurosurgical pathology. Already described in the beginning of the twentieth century and perfected by Yasargil in the 1970s, it has seen many modifications. These modifications have been a normal evolution for most neurosurgeons, tailoring the craniotomy to the patients' specific anatomy and pathology. Nonetheless, an abundance of variations have appeared in the literature.

METHODS

A search strategy was devised according to the 2020 Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) statement. To identify articles investigating the variations in the pterional approach, the following search terms were applied: (pterional OR minipterional OR supraorbital) AND (approach OR craniotomy OR technique).

RESULTS

In total, 3552 articles were screened with 74 articles being read in full with 47 articles being included for review. Each article was examined according the name of the technique, temporalis dissection technique, craniotomy technique and approach.

CONCLUSION

This systematic review gives an overview of the different techniques and modifications to the pterional craniotomy since it was initially described. We advocate for the use of a more standardised nomenclature that focuses on the target zone to simplify the management approach to supratentorial aneurysms.

Paraclinoid aneurysms clipping through an extradural sphenoid ridge keyhole approach

BACKGROUND

Paraclinoid aneurysms represent a challenge for neurosurgeons due to the anatomical complexity of this region. Then, innovative techniques such as the extradural sphenoid ridge approach are suitable for a safe microsurgical clipping.

METHOD

A description of the surgical technique was made by the senior author, a vascular neurosurgeon experienced with the use of this approach in the management of paraclinoid aneurysms exemplified through a clinical case.

CONCLUSION

Microsurgical clipping through an extradural sphenoid ridge keyhole approach for small and midsize paraclinoid aneurysms is an excellent treatment modality with good clinical and surgical results.

The sylvian keyhole approach for surgical clipping of middle cerebral artery aneurysms: Technical nuance to the minipterional craniotomy

Background

The minipterional (MPT) craniotomy is a workhorse approach for clipping of middle cerebral artery (MCA) aneurysms. Because it aims to reach the skull base, traction on the temporal muscle is required. As a result, patients may suffer from transient postoperative temporal muscle discomfort. The sylvian keyhole approach (SKA) represents an alternative craniotomy for the clipping of MCA aneurysms. The aims of this study are to describe the operative technique of the SKA and to discuss the benefits and disadvantages compared to the MPT craniotomy.

Methods

In this technical note, we report the experience gained with the SKA. This experience was acquired with virtual reality, 3D-printed models, and anatomical dissections. We also present two clinical cases.

Results

The SKA is centered on the distal sylvian fissure and tailored toward the specific MCA aneurysm. Traction to the temporal muscle is not necessary because access to the skull base is not sought. With the SKA, dissection of the MCA is performed from distal to proximal, aiming for a proximal control at the level of the M1-segment. The limen insulae was identified as a key anatomical landmark for approach selection. The SKA offers good surgical maneuverability when the aneurysm is located at the level or distal to the limen. The MPT craniotomy, however, remains the most appropriate approach when the aneurysm is located proximal to the limen.

Conclusion

The SKA represents a feasible and innovative alternative approach to the MPT craniotomy for surgical clipping of unruptured MCA aneurysms located at the level or distal to the limen insulae.

Minimally invasive craniotomies for lesions of the anterior and middle fossa

Minimally invasive craniotomies are the subject of increasing attention over the last two decades in neurosurgery, following the current trend of attempting to increase patient safety by providing surgeries with less tissue disruption, blood loss, and decreased operative time. However, a significant information overlap exists among the various keyhole approaches regarding their indications and differences with more invasive techniques. Therefore, the present study aims to comprehensively review, illustrate, and describe the potential benefits and disadvantages of minimally invasive techniques to access the anterior and middle fossa, including the mini-pterional, mini orbito-zygomatic, supraorbital, lateral supraorbital, and extended lateral supraorbital approaches while comparing them to classic, more invasive approaches.

Keyhole approach in anterior circulation aneurysm: Current indication, advantages, technical limitations, complications and their avoidance

Keyhole surgery recently evolved as a minimal invasive surgical approach for treatment of anterior circulation aneurysm. This review was done to evaluate the keyhole approach for anterior circulation aneurysms, their indications, advantages, technical limitations, complications and their avoidance. The literature review was performed with the phrase "keyhole approach for anterior circulation aneurysm" as a search term in PubMed central, Medline, Google scholar and Embase data base to identify all the articles published till December 2020. Out of 113 articles searched, 22 were included in this review after screening for eligibility. On analyzing these articles, there was total 2058 aneurysm in 1871 patients. Out of 2058 aneurysm, 988 were ruptured and 547 unruptured. In 5 studies, which include 344 aneurysms in 344 cases, aneurysm ruptured or unruptured status was not specified. The most frequent aneurysm site was anterior communicating artery (n=573). The size of the aneurysm mentioned in most of the study was <15 mm. The rate of complete occlusion was ranged from 93.6-100%. The range of intra operative rupture (IOR) was 0-28.6%. The mean operative time was ranged from 70 min-5.34 hours as reported in 13 studies. Good outcome [Glasgow outcome scale (GOS): 4-5] were seen in 75-100% cases. The frontalis muscle weakness has been reported in 3 studies and ranged from 0-1.99%. Keyhole surgery can be a safe and effective treatment modality for treatment of a selected anterior circulation aneurysm. In the experienced hand it has certain advantages over standard pterional craniotomy.

Extradural minipterional approach: Evolving indications of the minipterional craniotomy

Background:

In this paper, we report a clinical series of skull base lesions operated on trough the MiniPT, extending its application to skull base lesions, either using the classical minipterional or a variant, we call extradural minipterional approach (MiniPTEx).

Methods:

We describe our surgical technique of operating on complex skull base lesions using a minipterional extradural approach. Anterior clinoidectomy, middle fossa peeling, transcavernous, and Kawase approaches were performed as needed. In total, we carried out 24 surgeries: three skull base tumors, 1 Moyamoya case, and 20 giant/complex intracranial aneurysms. All the patients present good neurological result (mRs < 3). Only two patients had paralysis of any cranial nerve and only one patient had a mild hemiparesis.

Results:

This surgery series there are 24 cases, 10 patients were treated with exclusive MiniPT. MiniPT extradural approach was made in 14 patients. Twelve were treated using pure MiniPTEx approach, 1 patient using transcavernous approach, and in 1 patient, the anterior clinoid was resected with the combination of a MiniPT, a medium fossa peeling, and the Kawase anterior petrosectomy for skull base surgery.

Conclusion:

We further advance the indications of the MiniPT by extending it to operate on the cranial base tumors or complex vascular lesions without additional morbidity. MiniPT approach may be safely associated with skull base techniques, including anterior and posterior clinoidectomies, peeling of the middle fossa, transcavernous approach, and anterior petrosectomy. The versatility of the MiniPT craniotomy and the feasibility of performing skull base surgery through the MiniPT technique have been demonstrated in this paper.

[microsurgery 'burr hole' for intracranial tumors and mesial temporal lobe epilepsy]

PURPOSE

In recent years, neurosurgery has been characterized by a clear tendency towards the development of minimally invasive and less traumatic surgical approaches. To minimize the degree of injury to the brain tissue, we have proposed burr hole-based microsurgical approaches.

MATERIAL AND METHODS

In the period between February 2016 and February 2019, more than 500 microsurgical interventions were performed through a 14 mm burr hole using a technique that we called burr-hole microneurosurgery; to date, 200 of these have been analyzed. The age of patients varied from 16 to 79 years (median, 38 years). Female patients predominated - 1.6:1. Surgery for intracranial lesions with various locations was performed in 176 cases; in the remaining 24 cases, patients with hippocampal sclerosis underwent selective amygdalohippocampectomy.

RESULTS

Various surgical approaches were used: transcortical approach in 81 (40.5%) cases; retro-sigmoid approach in 38 (19%); sub-temporal approach in 32 (16%); infratentorial supracerebellar approach in 25 (12.5%); interhemispheric approach in 17 (8.5%); telovelar approach in 5 (2.5%); trans-eyebrow approach in 2 cases. The resection degree was evaluated in 167 patients with planned maximum tumor resection. Resection was total and almost total in 145 (87%) patients, subtotal in 15 (9%), and partial in 7 (4%). The surgery duration varied from 35 to 300 min (mean, 80 min). The extubation time after surgery ranged from 5 min to 5 days (mean, 70 min). In 195 (97.5%) cases, patients were verticalized within the first 3 days after surgery.

CONCLUSION

The proposed burr hole technique enables successful surgery in patients with various intracranial pathologies, using a smaller trepanation window compared to that in keyhole surgery. The proposed burr hole technique minimizes injury to the brain substance, significantly reduces patient's exposure to anesthesia, and decreases the entire duration of surgery.

The extradural minipterional approach for the treatment of paraclinoid aneurysms: a cadaver stepwise dissection and clinical case series

Minipterional (MPT) craniotomy has recently been added to the neurosurgical armamentarium as a less invasive alternative to the pterional craniotomy for the treatment of parasellar lesions. However, its clinical applicability in the treatment of certain complex aneurysms, such as those arising in the paraclinoid region, remains unclear. To illustrate the microsurgical anatomy of a modified extradural MPT approach, which combines a classic MPT craniotomy with an extradural anterior clinoidectomy, and to demonstrate its clinical applicability in the treatment of complex paraclinoid aneurysms. A stepwise extradural MPT approach is illustrated in a cadaver study. Clinical outcome data from a series of 19 patients with 20 paraclinoid aneurysms treated surgically using the extradural MPT approach between 2016 and 2018 were retrospectively collected. In 95% of the cases, complete aneurysm occlusion was achieved. No aneurysm recurrences were seen during follow-up with a median length of 21 months. The outcome, according to the modified Rankin Scale, was 0 points in 12 patients (63%), 1 point in 6 patients (32%), and 2 points in 1 patient (5%). Four out of 6 patients (67%) with initial visual symptoms showed improvement following treatment, whereas in two (11%), vision became worse. The extradural MPT approach ensures a sufficiently large exposure of the paraclinoid region that is comparable with conventional approaches with the advantage of being minimally invasive. Our case series demonstrates the feasibility of this approach for the treatment of complex paraclinoid aneurysms.

[A comparative study of the efficacy and safety of the eyebrow supraorbital approach in cerebral aneurysm surgery]

OBJECTIVE

The study objective was to compare the efficacy and safety of supraorbital eyebrow (SEA) and pterional (PA) approaches in surgery of anterior circle of Willis (ACW) aneurysms and to determine the advantages and disadvantages of SEA in aneurysm clipping.

MATERIAL AND METHODS

The analysis included 166 patients with ACW aneurysms aged 18 to 70 years who were treated in the Neurosurgery Department of the Interregional Clinical Diagnostic Center (Kazan) in the period from 2013 to 2016. At the first stage of the study, factors affecting surgical outcomes were compared (by using the Glasgow outcome scale (GOS)) in subpopulations of patients operated on using SEA (n=49) and PA (n=117). At the second stage, we compared the efficacy and safety of approaches using a case-control subanalysis in appropriate subgroups of the SEA (n=37) and PA (n=37) groups. The subgroups were comparable in the following factors: gender, age, severity of subarachnoid hemorrhage (SAH) on (Fisher scale), severity of the patient's condition (Hunt-Hess scale), size and location of the aneurysm, surgery duration, intraoperative aneurysm rupture (IOAR), amount of blood loss, rate of frontal sinus surgery, rate of nasal CSF leak, rate of intraoperative and postoperative complications, hemorrhagic and ischemic complications according to postoperative CT, patient's satisfaction with the cosmetic result of surgery (visual analogue scale - VAS), and treatment outcomes (GOS). Treatment outcomes (GOS) and patient's satisfaction with the cosmetic result of surgery (VAS) were considered as the efficacy parameters. The safety parameters included the amount of blood loss, rate of frontal sinus surgery, rate of nasal CSF leak, and rate of intraoperative and postoperative (hemorrhagic and ischemic) complications.

RESULTS

At the first stage of the study, we found that the amount of intraoperative blood loss in the subpopulation of patients with ACW aneurysms who were operated on using SEA was statistically significantly less than that in the PA group (p=0.0000002). In the postoperative period, patients who underwent surgery using SEA less frequently experienced neurological deficit (p=0.003), less frequently developed first epileptic seizures (p=0.035), and had a lower rate of hemorrhagic complications (p=0.003) and better treatment outcomes (GOS) (p=0.01). Comparison of appropriate subgroups in the SEA and PA groups, which were selected according to the case-control methodology and were comparable in the main factors affecting treatment outcomes, confirmed statistically significantly lower blood loss for SEA (p=0.0000002) than for PA. Compared to the SEA group, the PA group was characterized by more frequent, but not statistically significantly different, IOAR (p=1), postoperative worsening of neurological deficit (p=0.115), newly developed epileptic seizures (p=0.493), and hemorrhagic complications (p=0.0557). There were no deaths in both groups. In the SEA group, the treatment outcome was scored 4 and 5 (GOS, favorable outcome); in the PA group, the treatment outcome was scored 3 (GOS) in 2 (5.4%) patients and 4 or 5 in 35 (94.6%) patients (p=0.063). The mean subjective score of satisfaction with the treatment result (VAS) in the SEA group was significantly higher (9.4±1) than in the PA group (8.8±1; p=0.01).

CONCLUSION

SEA is an adequate approach for clipping ACW aneurysms, in particular ACA-AComA and MCA aneurysms, which is as effective and safe as the pterional approach.

Extended Lateral Orbital Craniotomy: Anatomic Study and Initial Clinical Series of a Novel Minimally Invasive Pterional Approach

Background  Of the minimally invasive "keyhole" alternatives to the pterional region, the supraorbital eyebrow approach is the most widely adopted. Yet it can prove disadvantageous when a more direct lateral microsurgical trajectory of attack to the Sylvian fissure and anterior middle fossa are needed. Objective  The extended lateral orbital (XLO) approach was designed to be direct and minimally invasive, with the sphenoid ridge at the center of exposure. Methods  Five injected cadaver heads were used for anatomic study of the XLO approach. The anatomic course of the frontalis branch of facial nerve was studied in relation to the XLO incision. Following XLO incision, the bone exposure was measured. The intracranial microsurgical exposure was assessed subjectively. Application of the technique in representative clinical operative cases is provided. Results  The frontalis nerve was protected in the subgaleal fat pad, with an average minimum distance of 2.3 cm from the XLO incision. The mean calvarial area exposure was 4.95 cm ² and consistently centered on the sphenoid ridge. Excellent access to ipsilateral Sylvian's fissure, perisylvian regions, and supra-/parasellar structures was possible. The main limitations related to exposure of the posterior Sylvian fissure and the expected limitations of microsurgical instrument manipulation from a smaller craniotomy. Conclusions  The XLO approach is a minimally invasive keyhole approach to the pterional region that affords a unique lateral trajectory via a craniotomy centered on the sphenoid ridge. Excellent exposure to properly selected lesions is possible. The incision is at a safe distance from the frontalis branch and shows excellent cosmetic healing.

A Comparative Study between Supraorbital Keyhole and Pterional Approaches on Anterior Circulation Aneurysms

Background

Many different conventional approaches such as the frontal and pterional approaches are used to access anterior circulation aneurysms. Recently, the supraorbital approach has been widely applied to the treatment of anterior circulation aneurysms. This study was done to evaluate which approach (pterional or supraorbital) has better outcomes in terms of residual neck post-clipping, cosmetic satisfaction, scar tenderness, complications and functional outcomes.

Methodology

A total of 123 patients were recruited into this study, comprising 82 patients who underwent a pterional approach and 41 patients who underwent a supraorbital approach. Computed tomography angiograms, the modified Rankin Scale, and the visual analogue scale were administered at 6 months to look for residual aneurysm, functional outcomes, scar tenderness, and cosmetic satisfaction. Complication data were collected from patients' case notes.

Results

The mean operating time for the pterional group was 226 min, compared to supraorbital group, which was 192 min (P = 0.07). Cosmetic satisfaction was significantly higher (P = 0.001) in the supraorbital group. There was no significant difference between the supraorbital and pterional groups' scar tenderness (P = 0.719), residual aneurysm (P = 0.719), or functional outcomes (P = 0.137), and there was no significant difference between the groups in terms of intra-operative and post-operative complications.

Conclusions

The supraorbital group had better cosmetic outcomes and shorter operating times compared to the pterional group.

Distal transsylvian keyhole approach for unruptured anterior circulation small aneurysms

Background

To reduce complications associated with conventional pterional craniotomy, a transsylvian keyhole approach for unruptured small anterior circulation aneurysms is proposed.

Methods

A 7-cm linear scalp incision is made along the hairline, beginning at the zygoma, followed by minimal temporal muscle dissection. Two burr holes are drilled out at McCarty’s point and the temporal bone, and a 3-cm equilateral triangle bone flap is made, whose apex is located above the sylvian point. After the sphenoid ridge is drilled off, aneurysms are exposed and clipped with conventional microsurgical instruments.

Conclusions

This approach permits access to aneurysms via the transsylvian corridor with a smaller area of potential injury of superficial structures.

Electronic supplementary material

The online version of this article (10.1007/s00701-017-3378-7) contains supplementary material, which is available to authorized users.

The minipterional approach for ruptured and unruptured anterior circulation aneurysms: Our initial experience

Objective:

To report our experience with the minipterional (MPT) craniotomy approach for anterior circulation aneurysms and to discuss the clinical outcomes as well as to evaluate the advantages of this unique approach.

Materials and Methods:

Single-center retrospective review of 57 cases involving anterior circulation aneurysms both ruptured and unruptured aneurysms treated with the MPT. We analyzed the clinical and patient demographic data, aneurysm characteristics, surgical outcomes, and complications in these individuals.

Results:

Between July 2008 and March 2014, of the 57 patients reviewed: 45 had middle cerebral artery (MCA), 6 had internal carotid artery terminus, and 7 had posterior communicating artery aneurysms. 20 of the 57 patients presented with a ruptured aneurysm. The average aneurysm size was 5.8 mm. The length of hospitalization for unruptured aneurysm cases ranged between 3 and 5 days. The average follow-up for all cases was 21.5 months. Successful clipping of the aneurysms was obtained in all patients. None of the cases required additional skin incisions or craniotomy extensions. The overall surgical outcomes were favorable. There was no postoperative facial nerve damage, temporalis muscle wasting, or symptoms of paresthesias around the incision line. Two patients developed a postoperative stroke manifested as symptoms of unilateral arm and facial weakness, receptive aphasia, and dysarthria.

Conclusion:

The MPT provides a reliable and less invasive alternative to the standard pterional craniotomy. Furthermore, ruptured and unruptured anterior circulation aneurysms can safely and effectively be treated with limited bone removal which provides better cosmetic outcomes and excellent postoperative temporalis muscle function.

Keyhole Approach and Neuroendoscopy for Cerebral Aneurysms

Treating diseases in the field of neurosurgery has progressed concomitantly with technical advances. Here, as a surgical armamentarium for the treatment of cerebral aneurysms, the history and present status of the keyhole approach and the use of neuroendoscopy are reviewed, including our clinical data. The major significance of keyhole approach is to expose an essential space toward a target, and to minimize brain exposure and retraction. Among several kinds of keyhole approaches, representative keyhole approaches for anterior circulation aneurysms include superciliary and lateral supraorbital, frontolateral, mini-pterional and mini-interhemispheric approaches. Because only a fixed and limited approach angle toward a target is permitted via the keyhole, however, specialized surgical devices and preoperative planning are very important. Neuroendoscopy has helped to widen the indications of keyhole approaches because it can supply illumination and visualization of structures beyond the straight line of microscopic view. In addition, endoscopic indocyanine green fluorescence angiography is useful to detect and correct any compromise of the perforators and parent arteries, and incomplete clipping. The authors think that keyhole approach and neuroendoscopy are just an intermediate step and robotic neurosurgery would be realized in the near future.

Computed Tomography- and Magnetic Resonance Image-based Analysis of the Anatomical Variations of the Sylvian Fissure and Characteristics of the Middle Cerebral Artery

The aim of this cross sectional anatomical study is to determine the distribution of the defined anatomical variations of the Sylvian fissure (SF) in a normal population and to analyze its bilateral superposable presentation. Furthermore, we examined the course of the middle cerebral artery (MCA) and the division of the MCA branches in relation to the SF types. A total of 300 cranial CT scans - 100 CT angiography datasets and 86 MRIs of patients without intracranial pathologies - were reviewed. The SF was categorized in five types based on Yasargils description and our previous publication. The length, diameter and branches of the MCA were measured and compared to the SF types. SPSS 23.0 for Windows® was used for statistical analysis. We analyzed data of 300 patients (171 male, 129 female; mean age 51.6years). Symmetric and mirror-imaged coherence of the SF was found in 266 patients (88.7%, χ²(8)=3.04, p=0.932). The distribution of the SF types showed significant differences in patients younger than 60 years compared to older patients. A bifurcation was observed in 72.0%. A trifurcation was observed in 12.0% and a false bifurcation in 16.0% of patients. There was no significant difference of the measured diameters or length of the M1 segments according to the SF types. In this CT and MRI based anatomical study we could show that a twisted and narrow SF occurred more frequently in patients younger than 60 years of age. The SF has a high congruence intra-individually. The anatomical condition might influence the size and configuration of the proximal MCA, which in turn might influence the surgeon's choice of the approach to the SF. Preoperative evaluation on the basis of the presented data, may help to decide for an appropriate approach to the SF.

[Minipterional craniotomy in surgery for anterior circle of Willis aneurysms]

One of the significant events in aneurysm surgery was promotion of a microneurosurgical technique by G. Yasargil. Despite its versatility, pterional craniotomy is associated with extensive osteotomy and a significant incision of the skin and temporal muscle, which may lead to the adverse cosmetic effects, risk of temporomandibular joint dysfunction, injury to the frontal branch of the facial nerve, and facial and scalp numbness. We present our experience with minipterional craniotomy in surgery for anterior circle of Willis aneurysms in 40 patients. There were no serious complications or deaths. Also, there were no intraoperative aneurysm ruptures. All patients had expected transient hypesthesia in the temporal region, which was not considered as a complication. This region was significantly smaller compared to that in classical pterional craniotomy. Patients assessed the postoperative cosmetic outcome as excellent.

Drilling of the marginal tubercle to enhance exposure via mini pterional approach: An anatomical study and clinical series of 25 sphenoid wing meningiomas

Background:

The marginal tubercle (MT) of zygomatic bone can be an obstacle in the standard mini pterional (MPT) craniotomy; we aim to evaluate the effect of drilling this MT in enhancing the exposure of MPT craniotomy for resection of sphenoid wing meningiomas (SWMs).

Methods:

The authors utilized 60 dry skulls to perform the anatomical part of the study. The MT size was reflected by the AB distance, wherein point A is the most prominent part of MT and point B is located on the orbital rim in the same axial plane as point A. The authors analyzed the effect of MT size in masking the sphenozygomatic suture (SZS), which is the most anterior part of the MPT craniotomy. One silicon-injected embalmed specimen was used to demonstrate other modifications to the standard MPT approach. The results of the anatomical analysis were translated into the second part of the study, which consisted of the resection of 25 SWMs.

Results:

The MT obscured visualization when the AB distance measured 13 mm or greater. In the clinical series of SWMs, drilling such prominent MT maximized exposure during MPT approach.

Conclusion:

The MPT approach could be used for the resection of SWMs. Drilling of prominent MTs can enhance and optimize exposure to SWMs through standard MPT approaches.

One Piece Orbitozygomatic Approach Based on the Sphenoid Ridge Keyhole: Anatomical Study

The one-piece orbitozygomatic (OZ) approach is traditionally based on the McCarty keyhole. Here, we present the use of the sphenoid ridge keyhole and its possible advantages as a keyhole for the one-piece OZ approach. Using transillumination technique the osteology of the sphenoid ridge was examined on 20 anatomical dry skull specimens. The results were applied to one-piece OZ approaches performed on freshly frozen cadaver heads. We defined the center of the sphenoid ridge keyhole as a superficial projection on the lateral skull surface of the most anterior and thickest part of the sphenoid ridge. It was located 22 mm (standard deviation [SD], 0.22 mm) from the superior temporal line; 10.7 mm (SD, 0.08 mm) posterior and 7.1 mm (SD, 0.22 mm) inferior to the frontozygomatic suture. The sphenoid ridge burr hole provides exposure of frontal, temporal dura as well as periorbita, which is essential for the later bone cuts. There is direct access to removal of the thickest (sphenoidal) part of the orbital roof, after which the paper-thin (frontal) part of the orbital roof is easily fractured. The sphenoid ridge is an easily identifiable landmark on the lateral skull surface, located below the usual placement of the McCarty keyhole, with comparative exposure.

Prospective randomized study comparing clinical, functional, and aesthetic results of minipterional and classic pterional craniotomies

OBJECT The object of this study was to compare the clinical, functional, and aesthetic results of 2 surgical techniques, pterional (PT) and minipterional (MPT) craniotomies, for microsurgical clipping of anterior circulation aneurysms. METHODS Fifty-eight patients with ruptured and unruptured anterior circulation aneurysms were enrolled into a prospective randomized study. The first group included 28 patients who underwent the MPT technique, and the second group comprised 30 patients who underwent the classic PT craniotomy. To evaluate the aesthetic effects, patients were asked to grade on a rule from 0 to 100 the best and the worst aesthetic result. Photographs were also taken, assessed by 2 independent observers, and classified as showing excellent, good, regular, or poor aesthetic results. Furthermore, quantitative radiological assessment (percentage reduction in thickness and volumetric analysis) of the temporal muscle, subcutaneous tissue, and skin was performed. Functional outcomes were compared using the modified Rankin Scale (mRS). Frontal facial palsy, postoperative hemorrhage, cerebrospinal fistula, hydrocephalus, and mortality were also analyzed. RESULTS Demographic and preoperative characteristics were similar in both groups. Satisfaction in terms of aesthetic result was observed in 19 patients (79%) in the MPT group and 13 (52%) in the PT group (p = 0.07). The mean score on the aesthetic rule was 27 in the MPT group and 45.8 in the PT group (p = 0.03). Two independent observers analyzed the patient photos, and the kappa coefficient for the aesthetic results was 0.73. According to these observers, excellent and good results were seen in 21 patients (87%) in the MPT and 12 (48%) in the PT groups. The degree of temporal muscle, subcutaneous tissue, and skin atrophy was 14.9% in the MPT group and 24.3% in the PT group (p = 0.01). Measurements of the temporal muscle revealed 12.7% atrophy in the MPT group and 22% atrophy in the PT group (p = 0.005). The volumetric reduction was 14.6% in the MPT and 24.5% in the PT groups (p = 0.012). Mortality and mRS score were similar in both groups at the 6-month evaluation (p = 0.99). CONCLUSIONS Minipterional craniotomy provides clinical results similar to those of the PT technique. Moreover, it provides better cosmetic results. It can be used safely and effectively to surgically treat aneurysms of the anterior circulation instead of the PT approach.

Keyhole concept in cerebral aneurysm clipping and tumor removal by the supraciliary lateral supraorbital approach

The keyhole concept in neurosurgery is designed to minimize the craniotomy needed for the access route to deep intracranial pathologies. Such keyhole surgeries cause less trauma and can be less invasive than conventional surgical techniques. Among the various types of keyhole mini-craniotomy, supraorbital or lateral supraorbital mini-craniotomy is the standard and basic keyhole approaches. The lateral supraorbital keyhole provides adequate working space in the suprasellar to parasellar areas and planum sphenoidale area including the anterior communicating artery complex. Despite the development of neuro-endoscopic techniques and intra-operative assistant methods, the limited working angle to manipulate and observe deeply situated pathologies is a major disadvantage of the keyhole approaches. Neurosurgeons should understand that keyhole mini-craniotomy surgeries aim at “minimally invasive neurosurgery” but still carry the risks of malpractice unless we understand the advantages and disadvantages of these keyhole concepts and strategies.

Effectiveness of zigzag Incision and 1.5-Layer method for frontotemporal craniotomy

Background:

In this era of minimally invasive treatment, it is important to make operative scars as inconspicuous as possible, and there is a great deal of room for improvement in daily practice. Zigzag incision with coronal incision has been described mainly in the field of plastic surgery, and its applicability for skin incision in general neurosurgery has not been reported.

Methods:

Zigzag incision with 1.5-layer method was applied to 14 patients with unruptured cerebral aneurysm between April 2011 and August 2012. A questionnaire survey was administered among patients with unruptured aneurysm using SF-36v2 since April 2010. The results were compared between patients with zigzag incision and a previous cohort with traditional incision.

Results:

There were no cases of complications associated with the operative wound. In the questionnaire survey, all parameters tended to be better in the patients with zigzag incision, and role social component score (RCS) was significantly higher in the zigzag group than in the traditional incision group (P =0.0436).

Conclusion:

Zigzag incision using the 1.5-layer method with frontotemporal craniotomy seems to represent an improvement over the conventional curvilinear incision with regard to cosmetic outcome and RCS.

Anatomical configuration of the Sylvian fissure and its influence on outcome after pterional approach for microsurgical aneurysm clipping

Background:

The sylvian fissure (SF) is the anatomical pathway used in a pterional approach, which leads to most aneurysms. There are four different anatomical variants of the SF described. In the present retrospective study the four different categories of the SF were studied in order to evaluate any correlation of these variants to surgical outcome.

Methods:

Patients treated for intracranial aneurysms by a pterional transsylvian approach during 2003-2012 (N = 237) were included in the study. The SF category was determined by analysis of preoperative computed tomography (CT) scanning. Patients were grouped into unruptured intracranial aneurysms (UIA) and ruptured intracranial aneurysms with subarachnoid hemorrhage (SAH) according to the Hunt and Hess grades. Brain edema, vasospasms, ischemic lesion rate, and outcome were evaluated for possible correlation with SF anatomical variants.

Results:

Postsurgically brain edema formation correlated significantly with more complex anatomical variants of the SF in patients with UIAs and in patients with Hunt and Hess 1 and 2. Ischemia rate, vasospasms, or clinical outcome was not negatively affected though.

Conclusion:

The classification of the SF as proposed by Yasargil is more than a pure anatomical observation. In this retrospective study, we show that the anatomical variants of the SF can be associated to postoperative complications like formation of brain edema or ischemic lesions Preoperative knowledge of the SF anatomy and possibly consecutive adapted extend of the surgical approach can decrease procedure-related morbidity.

Comparative Analysis of the Mini-pterional and Supraorbital Keyhole Craniotomies for Unruptured Aneurysms with Numeric Measurements of Their Geometric Configurations

Objective

Keyhole craniotomy is a modification of pterional craniotomy that allows for use of a minimally invasive approach toward cerebral aneurysms. Currently, mini-pterional (MPKC) and supraorbital keyhole craniotomies (SOKC) are commonly used. In this study, we measured and compared the geometric configurations of surgical exposure provided by MPKC and SOKC.

Methods

Nine patients underwent MPKC and four underwent SOKC. Their postoperative contrast-enhanced brain computed tomographic scans were evaluated. The transverse and longitudinal diameters and areas of exposure were measured. The locations of the anterior communicating artery, bifurcation of the middle cerebral artery (MCAB), and the internal carotid artery (ICA) terminal were identified, and the working angles and depths for these targets were measured.

Results

No significant differences in the transverse diameters of exposure were observed between MPKC and SOKC. However, the longitudinal diameters and the areas were significantly larger, by 1.5 times in MPKC. MPKC provided larger operable working angles for the targets. The angles by MPKC, particularly for the MCAB, reached up to 1.9-fold of those by SOKC. Greater working depths were required in order to reach the targets by SOKC, and the differences were the greatest in the MCAB by 1.6-fold.

Conclusion

MPKC provides larger exposure than SOKC with a similar length of skin incision. MPKC allows for use of a direct transsylvian approach, and exposes the target in a wide working angle within a short distance. Despite some limitations in exposure, SOKC is suitable for a direct subfrontal approach, and provides a more anteromedial and basal view. MCAB and posteriorly directing ICA terminal aneurysms can be good candidates for MPKC.

Preoperative percutaneous mapping of the frontal branch of the facial nerve to assess the risk of frontalis muscle palsy after a supraorbital keyhole approach

OBJECT

Although a supraorbital keyhole approach utilizing an eyebrow incision and supraorbital minicraniotomy is one of the most commonly used keyhole approaches for treating cerebral aneurysms, the risk of frontalis muscle palsy due to an injury of the frontal branch of the facial nerve remains a serious drawback to a supraorbital keyhole approach as a minimally invasive surgical technique. Therefore, the authors attempted to evaluate the risk of frontalis muscle palsy by mapping the frontal nerve branch in the lower forehead using a nerve conduction study in individual patients.

METHODS

Percutaneous mapping of the frontal nerve branch was performed preoperatively on 52 patients who underwent supraorbital keyhole approaches for aneurysmal clipping. The maximal compound muscle action potentials (CMAPs) in the lower forehead were observed at 5 points along a laterally inclined line angled 30° from the midpupillary line, in which the points were 1.0, 1.5, 2.0, 2.5, and 3.0 cm as measured from the supraorbital margin. ResULTS Severe frontalis muscle palsy was observed in 11 patients (21.2%), yet recovery occurred 2-5 months after surgery. No patients experienced permanent palsy. The incidence of severe palsy was 7.4% in those patients showing clear CMAPs with a high location (exclusively at 2.0, 2.5, or 3.0 cm), 14.3% in those with a bimodal distribution, 40.0% in those with a low location (exclusively at 1.5 cm), and 83.3% in those with an extremely low location (exclusively at 1.0 cm).

CONCLUSIONS

Percutaneous mapping of the frontal branch of the facial nerve using a nerve conduction study can be used to assess the risk of postoperative frontalis muscle palsy following a supraorbital keyhole approach. The patients with the highest risk of postoperative palsy showed a clear CMAP exclusively at 1.0 cm along the inclined line measured from the supraorbital margin.

Technical nuances of temporal muscle dissection and reconstruction for the pterional keyhole craniotomy

The supraorbital keyhole approach offers a limited access for aneurysms located at the middle cerebral artery (MCA) bifurcation with long M1 segments or proximal M2 aneurysms. Alternative minimally invasive routes centered on the pterion have been developed to address these aneurysms. Appropriate dissection and reconstruction of the temporal muscle are important for optimal exposure and best cosmetic results with the pterional keyhole craniotomy. The authors describe the technical nuances of temporal muscle dissection and reconstruction adapted to the pterional keyhole craniotomy.

After incising the scalp in a curvilinear fashion behind the hairline, an interfascial dissection is performed, allowing anterior reflection of the superficial temporal fat pat and superficial temporal fascia. The temporal muscle is incised 7–10 mm below its insertion at the superior temporal line. The deep temporal fascia and temporal muscle are incised vertically, completing a T-shaped incision. Subperiosteal dissection of both muscle flaps preserves the deep temporal arteries and nerves. A craniotomy measuring 2.5–3 cm in diameter, based anteriorly at the pterion, is made over the sylvian fissure. Dissection of the sylvian fissure and of MCA aneurysms can proceed without the use of retractors. The bone flap and associated hardware is entirely covered by the temporal muscle, which is reconstructed in 2 layers: the temporal muscle/deep temporal fascia and the superficial temporal fascia.

This dissection technique prevents damage to branches of the facial nerve and minimizes temporal muscle damage. Dividing the temporal muscle vertically and reflecting both parts anteriorly and posteriorly prevents suboptimal illumination and visualization under the microscope. Covering the bone flap and related hardware with a multilayer anatomical reconstruction optimizes cosmetic results.

The quality of life of patients with good outcomes after anterior circulation aneurysm surgery assessed by the world health organization quality of life instrument-korean version

Objective

Even in the patients with neurologically good outcome after intracranial aneurysm surgery, their perception of health is an important outcome issue. This study aimed to investigate the quality of life (QOL) and its predictors of patients who had a good outcome following anterior circulation aneurysm surgery as using the World Health Organization Quality of Life instrument-Korean version.

Methods

We treated 280 patients with 290 intracranial aneurysms for 2 years. This questionnaire was taken and validated by 99 patients whose Glasgow Outcome Scale score was 4 and more and Global deterioration scale 3 and less at 6 months after the operation, and 85 normal persons. Each domain and facet was compared between the two groups, and a subgroup analysis was performed on the QOL values and hospital expenses of the aneurysm patients according to the type of craniotomy, approach, bleeding of the aneurysm and brain injury.

Results

Aneurysm patients showed a lower quality of life compared with control patients in level of independence, psychological, environmental, and spiritual domains. In the environmental domain, there were significant intergroup differences according to the type of craniotomy and the surgical approach used on the patients (p<0.05). The hospital charges were also significantly different according to the type of craniotomy (p<0.05).

Conclusion

Despite good neurological status, patients surgically treated for anterior circulation aneurysm have a low quality of life. The craniotomy size may affect the QOL of patients who underwent an anterior circulation aneurysm surgery and exhibited a good outcome.

Microsurgical experience with supraorbital keyhole operations on anterior circulation aneurysms

OBJECTIVE

Conventional pterional approach is a commonly used neurosurgical technique for the treatment of cerebral aneurysms. However, this technique requires more extensive brain exposure than other key hole approaches and is sometimes associated with surgical traumatization or cosmetic problems. The aim of this study was to compare the postoperative outcome between pterional and supraorbital keyhole approaches in the patients with anterior circulation aneurysms.

METHODS

The authors reviewed patients with anterior circulation aneurysms who underwent aneurysm clipping via pterional or supraorbital keyhole approach at a single institute over a period of 2 years. Ninety-eight patients harboring 108 aneurysms were included in this study. Various outcomes were recorded, which included clinical grade, cosmetic problems, patients' satisfaction and complications such as chewing discomfort, frontal muscle weakness, hyposmia, infection.

RESULTS

The supraorbital approach exhibited a shorter operation time compared with the pterional approach. Complications such as chewing discomfort occurred less frequently in the supraorbital approach group. Moreover, the cosmetic outcome was significantly better in the supraorbital group than in the pterional group.

CONCLUSION

The supraorbital keyhole approach reduced intra- and postoperative complications, including chewing discomfort and cosmetic disturbances, compared with the conventional pterional approach.