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Objective: To investigate the association of high septal deviation with the olfactory fossa depth and Gera angle., Methods: Fifty-four computed tomography scans of patients with high septal deviation were evaluated. The olfactory fossa depth and Gera angle were measured. The values of the deviated and nondeviated sides were compared., Results: No association between high septal deviation and the olfactory fossa depth and Gera angle was found., Conclusion: High septal deviation does not affect the olfactory fossa depth and Gera angle. In other words, the olfactory fossa depth and Gera angle have no association with the high septal deviation.

Background: Among the new perspectives to revolutionize skull base surgery, there are the transorbital neuroendoscopic (TONES) approaches to reach the anterior and middle cranial fossa (ACF and MCF). We conceived to explore the potentialities of a modified superiorly and medially extended lateral retrocanthal (LRC) approach., Methods: Six head specimens were dissected. Applying the established conic model and the key surgical landmark of sphenofrontal suture, we tested the feasibility of a modified LRC to reach ACF and MCF; computed tomography (CT) scans were performed before and after dissection to obtain a morphometric analysis of the surgical corridors using a polygonal surfaces model., Results: Through our anatomical study, we were able to identify and explore 3 different surgical corridors to reach the ACF and MCF: the superomedial, the superolateral, and the inferolateral. The superomedial corridor appeared most suitable to reach the medial part of the ACF and the optic-carotid region, whereas through the superolateral and inferolateral corridors it was possible to reach and explore the lateral part of ACF and MCF. The mean volumes of the 3 surgical corridors calculated on post-dissection CT scans were: 12.72 ± 1.99, 5.69 ± 0.34, and 6.24 ± 0.47 cm 3 , respectively., Conclusions: The development of TONES approaches has not replaced the traditional open or endoscopic approach; nonetheless, identification of surgical corridors and the possibility to combine them represent a major breakthrough. Clinical studies are necessary to demonstrate their validity and test the effectiveness, safety, and reproducibility of TONES approaches in managing lesions harboring in the ACF and MCF., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: Keyhole approaches, namely the minipterional approach (MPTa) and the supraorbital approach (SOa), are alternatives to the standard pterional approach to treat lesions located in the anterior and middle cranial fossae. Despite their increasing popularity and acceptance, the indications and limitations of these approaches require further assessment. The purpose of the present study was to determine the differences in the area of surgical exposure and surgical maneuverability provided by the MPTa and SOa., Methods: The areas of surgical exposure afforded by the MPTa and SOa were analyzed in 12 sides of cadaver heads by using a microscope and a neuronavigation system. The area of exposure of the region of interest and surgical freedom (maneuverability) of each approach were calculated., Results: The area of exposure was significantly larger in the MPTa than in the SOa (1250 ± 223 mm2 vs 939 ± 139 mm2, p = 0.002). The MPTa provided larger areas of exposure in the ipsilateral and midline compartments, whereas there was no significant difference in the area of exposure in the contralateral compartment. All targets in the anterior circulation had significantly larger areas of surgical freedom when treated via the MPTa versus the SOa., Conclusions: The MPTa provides greater surgical exposure and better maneuverability than that offered by the SOa. The SOa may be advantageous as a direct corridor for treating lesions located in the contralateral side or in the anterior cranial fossa, but the surgical exposure provided in the midline region is inferior to that exposed by the MPTa.

Background: Endoscopic transorbital approach (eTOA) has been announced as an alternative minimally invasive surgery to skull base. Owing to the inferior orbital fissure (IOF) connecting the orbit with surrounding pterygopalatine fossa (PPF), infratemporal fossa (ITF), and temporal fossa, the idea of eTOA to anterolateral skull base through IOF is postulated. The aim of this study is to access its practical feasibility., Methods: Anatomical dissections were performed in five human cadaveric heads (10 sides) using 0-degree and 30-degree endoscopes. A stepwise description of eTOA to anterolateral skull base through IOF was documented. The anterosuperior corner of the maxillary sinus in the horizontal plane of the upper edge of zygomatic arch was defined as reference point (RP). The distances between the RP to the foramen rotundum (FR), foramen ovale (FO), and Gasserian ganglion (GG) were measured. The exposed area of anterolateral skull base in the coronal plane of the posterior wall of the maxillary sinus was quantified., Results: The surgical procedure consisted of six steps: (1) lateral canthotomy with cantholysis and preseptal lower eyelid approach with periorbita dissection; (2) drilling of the ocular surface of greater sphenoid wing and lateral orbital rim osteotomy; (3) entry into the maxillary sinus and exposure of PPF and ITF; (4) mobilization of infraorbital nerve with drilling of the infratemporal surface of the greater sphenoid wing and pterygoid process; (5) exposure of middle cranial fossa, Meckel's cave, and lateral wall of cavernous sinus; and (6) reconstruction of orbital floor and lateral orbital rim. The distances measured were as follows: RP-FR = 45.0 ± 1.9 mm, RP-FO = 55.7 ± 0.5 mm, and RP-GG = 61.0 ± 1.6 mm. In comparison with the horizontal portion of greater sphenoid wing, the superior and inferior axes of the exposed area were 22.3 ± 2.1 mm and 20.5 ± 1.8 mm, respectively. With reference to the FR, the medial and lateral axes of the exposed area were 11.6 ± 1.1 mm and 15.8 ± 1.6 mm, respectively., Conclusions: The eTOA through IOF can be used as a minimally invasive surgery to access whole anterolateral skull base. It provides a possible resolution to target lesion involving multiple compartments of anterolateral skull base.

The anterior cranial fossa is an important anatomical landmark in clinical orthodontics consisting of the frontal, ethmoid, and sphenoid bones. The relationships between these bones remain poorly understood. The purposes of the present study were to describe the morphological relationships among the three bones and to discuss the factors contributing to individual variations in adult skulls based on postnatal development. Skulls of 100 Indian adults and 18 Japanese juveniles were observed both macroscopically and using computed tomography images in the median sagittal plane. Three types of relationship were seen among the three bones in adult skulls: (a) a triangular border between ethmoid and sphenoid bones (ethmoid spine), (b) a straight or concave border between ethmoid and sphenoid bones, and (c) frontal bone lying between the ethmoid and sphenoid bones. In the juvenile skull, structures corresponding to those in adults were observed. These three bones comprise the anterior cranial base, each with differing developmental processes, and slight differences in these processes seem to be reflected in the morphological variations seen among adults., Competing Interests: None declared.

Removal of the fronto-orbital bandeau is one of the most critical components for procedures designed to correct anomalies of the craniofacial skeleton and remodel the anterior calvarial vault. It is also used to improve exposure of the anterior cranial fossa. It is arguably one of the more difficult portions of some craniofacial procedures. While the technique for fronto-orbito-sphenoid osteotomy has been frequently described, it has only been minimally detailed. Separation of bone in this region remains challenging due to the bone thickness, adjacent vital structures, and limited direct visibility. The present paper describes the anatomy of this particular region, which the authors have termed the "triple point", to facilitate successful osteotomy and avoid potential injury.

Background: Frontofacial monobloc advancement creates a communication between the anterior cranial fossa and nasal cavities. To tackle this issue, transorbital pericranial pedicled flaps are routinely performed in the authors' center. This study aimed to assess the postoperative ossification of the anterior skull base and pedicled flaps following frontofacial monobloc advancement, and to identify factors influencing this ossification., Methods: Measurements of the skull base only and of the ossified pedicled flaps together with the skull base were performed on computed tomographic scans at the nasofrontal and the nasoethmoid frontal junctions. The total thickness of the skull vault was measured and a qualitative defect score for the anterior skull base was computed., Results: Twenty-two patients who underwent frontofacial monobloc advancement at a median age of 3.1 years (range, 1.9 to 3.6 years) were included: 14 with Crouzon, five with Pfeiffer, and three with Apert syndrome. One year and 5 years after surgery, the distraction gap was completely ossified in the anterior skull base midline in all patients. Ossified pedicled flaps together with the skull base were thicker in patients than in controls at these two time points (p < 0.005 and p < 0.02). Patients with Pfeiffer syndrome had a significantly thicker skull base only and ossified pedicled flaps together with the skull base thicknesses (p = 0.01 and p = 0.03) and lower defect scores than patients with Crouzon or Apert syndrome (p = 0.03) 1 year postoperatively., Conclusion: As ossification of the pedicled flaps and total reossification of the anterior skull base midline were observed in all patients, the authors indicate that performing pedicled flaps in frontofacial monobloc advancement surgery could promote the reossification of the anterior skull base., Clinical Question/level of Evidence: Therapeutic, IV.

Objective We sought to identify a relationship between skull base height and anterior ethmoid artery (AEA) anatomy. Study Design Retrospective radiologic chart review. Setting University of Arkansas for Medical Sciences. Subjects Patients seen in a tertiary rhinology clinic between September 2014 and October 2015. Methods Review of 101 maxillofacial computed tomography scans with institutional review board approval. Skull base height and AEA locations were measured on each side. Prevalence of the AEA outside of the skull base and distance of the AEA from skull base were calculated and compared with Keros classification using χ 2 testing. Comparisons of skull base height between sexes and age and distance between skull base and the AEA among Keros 2 and Keros 3 patients were made using an unpaired, 2-tailed t test. Results The AEA was located below the skull base in 25.7% of cases and more often in Keros type 3 (55%) than in Keros type 2 (29.5%) or Keros type 1 (0%) ( P < .05). Male patients were significantly more likely to have a greater average skull base height (5.25 vs 4.28 mm) and to have AEAs below the skull base (38.4% vs 14.8%). In addition, the distance of the AEA from the skull base was significantly higher in Keros type 3 patients compared with Keros type 2 patients (4.55 vs 3.42 mm, P = .001). Conclusions Variations in the AEA pathway occur more in male patients and those with higher Keros classifications. The distance between the variant AEA and the skull base increases with higher Keros classification. Keros classification can yield insight to the location of the AEA.

Orbits are connected with the middle cranial fossa via the optic canal, the superior orbital fissure, the M-type orbitomeningeal foramen, the metoptic canal, an accessory anterior opening of the foramen rotundum, and Warwick's canal. They are also in communication with the anterior cranial fossa via the ethmoidal canals and the A-type orbitomeningeal foramen. The anatomy of these conduits has been recently enriched with several details that are summarized and reviewed in this article.

The skull base is uniquely placed to absorb anteriorly directed forces imparted either via the midfacial skeleton or cranial vault. A variety of skull base fracture classifications exist. Less well understood, however, is fracture extension beyond the anterior cranial fossa (ACF) into the middle and posterior cranial fossae. The cases of 81 patients from two UK major trauma centres were studied to examine the distribution of fractures across the skull base and any relationship between the vector of force and extent of skull base injury. It was found that predominantly lateral force to the craniofacial skeleton produced a fracture that propagated beyond the ACF into the middle cranial fossa in 77.4% of cases, significantly more (P<0.001) than for predominantly anterior force (12.0%). Fractures were significantly more likely to propagate into the posterior fossa with a lateral vector of impact compared to an anterior vector (P=0.049). This difference in energy transfer across the skull base may, in part, be explained by the local anatomy. The more delicate central ACF acts as a 'crumple zone' in order to absorb force. Conversely, no collapsible interface exists in the lateral aspect of the ACF, thus the lateral ACF behaves like a 'buttress', resulting in increased energy transfer., (Copyright © 2015 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

Typically, the medial orbital wall contains an anterior ethmoidal foramen (EF) and a posterior EF, but may also have multiple EFs transmitting the arteries and nerves between the orbit and the anterior cranial fossa. The aim of this study is to determine a patient-friendly landmark of the medial orbital wall and to specify a precise location of the ethmoidal foramens (EF) in order to standardize certain anatomical marks as safe ethmoidal arteries. Orientation points on the anterior ethmoidal foramen (AEF), posterior ethmoidal foramen (PEF) and middle ethmoidal foramen (MEF) were investigated in 262 orbits. Using a software program, distances between each foramen and the midpoint of the anterior lacrimal crest (ALC), the optic canal (OC), and some important angles were measured. The EFs were identified as single in 0.8%, double in 73.7%, triple 24,4% and quadruple in 1.1% specimens. The mean distances between ALC and AEF, ALC and PEF and ALC and MEF were 27.7, 10.6, and 12.95 mm, respectively. The distances from ALC-AEF, AEF-PEF, and PEF-OC were 27.7 ± 2.8, 10.6 ± 3.3, 5.4 ± 1 mm. The angles from the plane of the EF to the medial border of the OC were calculated as 13.2° and 153°, respectively. The angle from the AEF to the medial border of the OC was based on the plane between the ALC and AEF was 132°. The occurrence of multiple EF with an incidence of 25% narrows the borders of the safe region in the medial orbital wall. Safe distance of the ALC-EF was measured as 22.1 mm on medial wall. The line of the location of the EF was calculated 16.2 mm. In this study, it was possible to investigate the variability of the orbital orifice of the EF and the feasibility of the EA, to observe various angles of the orbital wall bones and to calculate the lengths of some parameters with the help of certain software.

Aim: The major aim of the present anatomical study was to demonstrate the anatomical structures that can be visualized using the supraorbital keyhole approach, both endoscopically and microscopically, from an eyebrow incision to intracranial structures. Furthermore, it defines an optimal craniotomy for surgery., Methods: Fine dissection was performed on each side of 5 formalin-fixed adult cadavers according to the surgical procedures of the supraorbital keyhole approach, and each step was documented both endoscopically and microscopically. Furthermore, the distance between the superior temporal line and the supraorbital notch/foramen was measured from the 10 total sides of the 5 cadavers and from the 118 sides of the 59 autopsies., Results: Tumors and aneurysms of the anterior cranial fossa can be visualized during the supraorbital keyhole approach. The average distance between the superior temporal line and the supraorbital notch/foramen was measured. The distance obtained from the autopsies on the 25 females was 31.56 ± 4.03  mm on the right side and 31.04 ± 5.40  mm on the left side. The average distance obtained from the autopsies on the 34 males was 34.00 ± 4.59  mm on the right side and 33.59 ± 5.41  mm on the left side. There was no statistically significant difference between right and left in the female and male autopsies or between sexes., Conclusions: This anatomical study showed that structures in the anterior and middle cranial fossa can be reached via the supraorbital keyhole craniotomy approach with minimal brain retraction and adequate exposure and with minimal craniotomy size.

We reviewed the anatomy and embryology of the bridging and emissary veins aiming to elucidate aspects related to the cranial dural arteriovenous fistulae. Data from relevant articles on the anatomy and embryology of the bridging and emissary veins were identified using one electronic database, supplemented by data from selected reference texts. Persisting fetal pial-arachnoidal veins correspond to the adult bridging veins. Relevant embryologic descriptions are based on the classic scheme of five divisions of the brain (telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon). Variation in their exact position and the number of bridging veins is the rule and certain locations, particularly that of the anterior cranial fossa and lower posterior cranial fossa are often neglected in prior descriptions. The distal segment of a bridging vein is part of the dural system and can be primarily involved in cranial dural arteriovenous lesions by constituting the actual site of the shunt. The veins in the lamina cribriformis exhibit a bridging-emissary vein pattern similar to the spinal configuration. The emissary veins connect the dural venous system with the extracranial venous system and are often involved in dural arteriovenous lesions. Cranial dural shunts may develop in three distinct areas of the cranial venous system: the dural sinuses and their interfaces with bridging veins and emissary veins. The exact site of the lesion may dictate the arterial feeders and original venous drainage pattern.

Object: The transbasal approach (TBA) is an anterior skull base approach, which provides access to the anterior skull base, sellar-suprasellar region, and clivus. The TBA typically involves a bifrontal craniotomy with orbital bar and/or nasal bone osteotomies performed in 2 separate steps. The authors explored the feasibility of routinely performing this approach in 1 piece with a quantitative cadaveric anatomical study, and present an operative case example of their approach., Methods: Seven latex-injected cadaveric heads underwent a 1-piece TBA, followed by additional bone removal typical for a traditional 2-piece approach. Six surgical angles relative to the pituitary stalk, as well as the surface area of the orbital roof osteotomy, were measured before and after additional bone removal. The vertical angle from the frontonasal suture to the foramen cecum was measured in all specimens. In addition to an anatomical study, the authors have used this technique in the operating room, and present an illustrative case of resection of an anterior skull base meningioma., Results: Morphometric results were as follows: the vertical angle from the frontonasal suture to the foramen cecum ranged from 17.4° to 29.7° (mean 23.8° ± 4.8°) superiorly. Of the 6 surgical angle measures, only the middle horizontal angle was increased in the 2-piece versus the 1-piece approach (mean 43.4° ± 4.6° vs 43.0° ± 4.3°, respectively; p = 0.049), with a mean increase of 0.4°. The surface area of the orbital osteotomy was increased in the 2-piece versus the 1-piece approach (mean 2467 mm(2) ± 360 mm(2) vs 2045 mm(2) ± 352 mm(2), respectively; p < 0.001). The patient in the illustrative clinical case had a good outcome, both clinically and cosmetically., Conclusions: The 1-piece TBA provides an alternative to the traditional 2-piece approach. It allows easier reconstruction, potentially decreased operative time, and improved cosmesis. While more of the orbital roof can be removed with the 2-piece approach, this additional bone removal offers only a small increase in 1 of 6 surgical angles that were measured.

Objectives/hypothesis: Endoscopic infratemporal fossa (ITF) surgery is a growing clinical interest. This study presents a method of analyzing approach access and visualization, identifies relevant anatomy in an endoscopic approach to the ITF, and compares endoscopic medial maxillectomy (MMA) and endoscopic-assisted sublabial transmaxillary (SLT) approaches to the ITF as a model for this paradigm., Study Design: Human cadaver anatomic study., Methods: Five human cadaver heads (10 ITF dissections) were used. An SLT and MMA were performed on each side. For endoscopic dissections of the ITF, 0° and 30° endoscopes were used. Key landmarks were the posterior maxillary sinus wall, temporomandibular joint, pterygoid plates, foramen spinosum, and foramen ovale. Open dissection was used to confirm ITF landmarks. A novel measurement method using angles of approach and visualization was used to compare approaches., Results: Visualization and mobility in SLT and MMA were significantly different. The lateral extent and greatest average depth for dissection was 7.9 cm in MMA and 6.1 cm for SLT. The average angle of mobility in approach was 36.3° for MMA and 57.9° for SLT. Average visualization was 40.2° for MMA and 126.5° for SLT. Despite these differences, both surgical approaches allowed access and visualization to all targeted landmarks., Conclusions: This evaluation paradigm provides useful data in evaluating an endoscopic or endoscopic-assisted approach to the ITF. Using this paradigm, the SLT and MMA were analyzed. Each provided adequate access to the ITF, but visualization and maneuverability were better in SLT., (Copyright © 2013 The American Laryngological, Rhinological and Otological Society, Inc.)

Various surgical approaches to the infratemporal fossa (ITF) have been reported. Among them, the preauricular transzygomatic anterior ITF approach (anterior ITF approach) has been used for exposure of the antero-superior part of the ITF. The purpose of this article is to show anatomical dissections using the anterior ITF approach and to evaluate our surgical experience using this approach. An anatomical study of the anterior ITF approach was performed using six sides of three cadaveric heads. Clinical course was retrospectively reviewed for 34 patients who underwent microsurgical resection of tumor in or around the ITF using this approach. Medical, surgical, and neuroimaging records of these patients were evaluated. The key point of this approach was mobilization of the second and third divisions of the trigeminal nerve after drilling of the lateral loop between the foramina rotundum and ovale. After mobilization of the trigeminal nerve, the auditory tube, tensor veli palatini muscle, and pharyngobasilar membrane could be seen. Removal of the pterygoid muscles and plates allowed surgical access to the ITF, orbit, maxillary sinus, pterygopalatine fossa, and parapharyngeal space. We used this approach in 31 patients with skull base tumors between 1994 and 2007. Gross total removal was achieved in 27 of the 31 patients. No mortality or severe morbidity was encountered. Therefore, the anterior ITF approach provides easy access to the ITF and adjacent regions without destruction of important organs.

Background: As a thin filmy covering overlaying the inferior orbital fissure (IOF), Muller's muscle was considered a vestigial structure in humans, and for this reason, its anatomical significance was neglected. Because of increasing interest in endonasal approaches to the skull base that encompasses this region, we re-examined this structure's role as an anatomical landmark from an endoscopic perspective., Methods: In 10 cadaveric specimens, microanatomical dissections were performed (n = 5); endoscopic dissections were performed (n = 5) via approaches of the middle turbinate or inferior turbinate, and via the Caldwell-Luc approach through the maxillary sinus. Histological examinations were performed in 20 human fetuses (Embryology Institute, Universidad Complutense de Madrid, Madrid, Spain)., Results: In cadaveric dissections, Muller's muscle was demonstrated in all specimens, serving as a bridge-like structure that spanned the entire IOF and separated the orbit from the temporal, infratemporal, and pterygopalatine fossas. Depending on which endoscopic corridor was used, a different aspect of the IOF and Muller's muscle was identified. In our endoscopic and microscopic observations, Muller's muscle was extensive, not only spanning the IOF but also extending posteriorly to reach the superior orbital fissure (SOF) and anterior confluence of the cavernous sinus. Histological analysis identified many anastomotic connections between the ophthalmic venous system and pterygoid plexus that may explain how infection or tumor spreads between these regions., Conclusions: Muller's muscle serves as an anatomical landmark in the IOF and facilitates anatomical orientation in this region for endoscopic skull base approaches. Its recognition during endoscopic approaches allows for a better three-dimensional understanding of this anterior cranial base region., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Dural arteriovenous fistulas (dAVFs) of the anterior cranial fossa have traditionally been treated by open surgical disconnection. Safe navigation through the ophthalmic artery or fragile cortical veins has historically provided a barrier to effective endovascular occlusion of these lesions. Using current microcatheter technology and embolic materials, safe positioning within the distal ophthalmic artery, beyond the origin of the central retinal artery, is achievable. We describe two cases in which anterior cranial fossa dAVFs were treated by exclusively endovascular strategies, and highlight the pertinent technical and anatomic considerations. We discuss the clinical symptoms resulting from the differing venous drainage patterns.

Background: We investigated a new minimally invasive surgical technique for the treatment of idiopathic intracranial hypertension in a cadaveric model. This technique aims at establishing a communication between the intraorbital and intracranial compartments by creating a bone, dural, and periorbital window in the anterior cranial fossa. This procedure is predicated on intraorbital absorptive capability that has been demonstrated in animals and discussed in humans., Methods: Three fresh cadaver heads were fixed in a head holder so as to mimic the hyperextended supine position. The procedure was conducted bilaterally in each specimen. Our technique is as follows: 1) An incision is made in the eyebrow medial to the supraorbital notch; 2) using an endoscope and a periosteal elevator, the intraorbital surface of the orbital roof is separated from the periorbita in an anteroposterior direction for a length of 1.5-2.5 cm; 3) a 1 cm of the exposed orbital roof is removed, and the dura and arachnoid are opened; and 4) slits are made in the exposed periorbita., Results: We were able to create a communication between the intracranial and the intraorbital compartments in all specimens., Conclusion: Our technique is new and does not require any foreign body implantation. Its applicability in humans needs to be evaluated in a clinical context.

Objectives: To describe an anatomic and clinical outcome study of transorbital neuroendoscopic surgical (TONES) for the repair of complex anterior cranial fossa (ACF) cerebrospinal fluid (CSF) leaks., Design: Anatomic cadaver investigation and clinical outcomes evaluation., Methods: An anatomic cadaver study was undertaken to determine the anatomic feasibility of the TONES approaches for repair of CSF leaks, and determine the optimal approaches for these repairs. A targeted outcome analysis was performed on 10 consecutive patients who underwent 12 ACF CSF leak repairs by TONES., Results: The cadaver study demonstrated that the entire ACF can be accessed by TONES. Due to the rise and angulation of the orbital roof above the interorbital ACF, the precaruncular (PC) approach optimal for a coplanar target approach in the interorbital ACF, and the superior lid crease (SLC) trajectory is preferable for procedures involving the supraorbital ACF. There were no complications in the 12 clinical procedures. Fifty percent of the cases were revisions, referred after up to five previous craniotomies and endoscopic procedures; all TONES repairs were successful with a single operation., Conclusions: The use of TONES to repair ACF CSF leaks was demonstrated to be technically feasible in cadaver and clinical studies. The SLC approach was optimal for supraorbital ACF leaks; the PC approach was preferable for interorbital ACF pathology. TONES was shown to be highly effective for treating complex pathology that was refractory to correction through frontal craniotomy and /or transnasal endoscopy, providing safe, minimally disruptive direct coplanar routes for target approach and manipulation.

We present a patient who had a median anterior cerebral artery fenestration with a congenital azygous infra-optic anterior cerebral artery. This rare combination of abnormalities was an incidental finding in a patient who suffered spontaneous subarachnoid haemorrhage from a ruptured anterior cerebral artery aneurysm., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The primary goal of any surgical approach is to adequately visualize and treat the pathologic condition with minimal disruption to adjacent normal anatomy. The work of several researchers has revealed the promise of minimally invasive endonasal neurosurgery and paved the way for broader applications of the technology. This article discusses the current state of minimally invasive endonasal techniques to address the pathologic conditions of the anterior cranial fossa and parasellar region., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Background and Purpose: Interpretation of CT of the anterior skull base in children depends on knowledge of the pattern and chronology of ossification. The purpose of this study was to ascertain the age at which the anterior cranial fossa is fully ossified as assessed on CT examinations., Materials and Methods: This was a retrospective review of 127 CT examinations of children ranging from 1 day to 16 years 7 months of age without known or suspected anterior cranial fossa abnormality. Measurements of the length and width of the anterior skull base and the presence and size of the most anterior unossified portion were determined by 2 investigators., Results: At birth, the anterior skull base consists mainly of cartilage. There is a wide variation in ossification rates between individuals, but the anterior skull base was fully ossified at 3 years 10 months in all of our cases., Conclusions: In healthy individuals, the anterior skull base is fully ossified by 4 years of age.

Background: Tumors of the gyrus cinguli are deep-seated, and may require a variety of surgical options. We focused on anterior tumors, which have specific anatomic and surgical features., Objective: To evaluate different approaches and indications through detailed description and a review of our experience., Methods: These approaches include unilateral interhemispheric or combined: bilateral interhemispheric, unilateral plus superior frontal gyrectomy, or unilateral plus frontal polectomy. The relevance of this retrospective analysis is stressed by the extremely limited literature in this regard., Results: In the past 5 years we operated on 38 patients with gliomas. We compared the following variables: location (perigenual, prerolandic), pathology (glioblastoma, other gliomas), size (<4 cm, > or =4 cm), extension (unilateral, bilateral), and approach (unilateral interhemispheric, combined). The only significant association we found was between tumor location (perigenual) and bilateral extension (P < .01). However, combined approaches were adopted only slightly more frequently in this region than in the prerolandic area, and this resulted in a lower rate of total removal (33% vs 76%, P < .01). Gross total removal was achieved in 28 cases (66%) and was significantly associated with combined approaches (77% vs 50%, P < .05)., Conclusions: The choice of a combined approach to anterior gyrus cinguli tumors is critical to improving the quality of resection in selected cases. We recommend a combined approach in the surgical treatment of large tumors of the perigenual area.

Background: The transciliary supraorbital approach (TCSO) provides an anterior view for visualizing sellar, parasellar, and suprasellar structures. Whether an orbital osteotomy adds to this exposure has not been quantified., Objective: We quantitatively evaluated the TCSO and benefits of an additional orbital osteotomy for exposing common sites of anterior circulation aneurysms., Methods: Under image guidance, TCSO and orbital osteotomy were performed on 10 sides of 5 cadaver heads to quantify exposures of 4 surgical targets: (1) the junction of the anterior cerebral and anterior communicating arteries (ACoA); (2) the internal carotid artery (ICA) at the level of the posterior communicating artery (PCoA); (3) the bifurcation of the ICA; and (4) the middle cerebral artery (MCA) bifurcation. Horizontal and vertical angles of attack and surgical freedom for instrument manipulation were measured before and after the orbital rim and roof were removed., Results: An orbital osteotomy significantly increased surgical freedom to the ACoA (from 471.15 +/- 182.14 mm2 to 683.35 +/- 283.78 mm2, P = .021); PCoA (from 746.58 +/- 242.78 mm2 to 966.23 +/- 360.22 mm2, P = .007); ICA bifurcation (from 616.08 +/- 310.95 mm2 to 922.38 +/- 374.88 mm2, P = .002); and MCA bifurcation (from 1160.77 +/- 412.03 mm2 to 1597.71 +/- 733.18 mm2, P = .004). There were no significant differences in horizontal angles of attack. The vertical angles of attack were significantly greater after orbital osteotomy, principally with the ACoA and ICA bifurcation as targets., Conclusion: TCSO combined with orbital osteotomy improves exposure. Removing the orbital rim and roof increases the area for instrument use and improves the vertical angle of attack to common sites in the anterior circulation involving aneurysms.

Background: Precise placement of the MacCarty keyhole, a burr hole simultaneously exposing the anterior cranial fossa floor and orbit, provides accurate, efficient entry for orbitozygomatic and supraorbital craniotomies. To locate the optimal keyhole site, previous studies have used superficial landmarks that, in our experience, are not always visible or consistent on older crania., Objective: Therefore, we present a technique for accurate keyhole placement using landmarks that are easily visible across age ranges., Methods: From inside the cranium, 1-mm burr holes were placed along the anterior junction of the floor and lateral wall of the anterior cranial fossa in 50 adult skulls (100 sides, with calvaria removed). Additionally, from inside the orbit, 1-mm burr holes were placed into the lateral orbital roof. Exit sites of intracranial and intraorbital burr holes were referenced to the frontozygomatic suture. The center of the site between the exiting intracranial and intraorbital holes was deemed the best location for the keyhole., Results: The keyhole center was 6.8 mm (mean) superior and 4.5 mm (mean) posterior to the frontozygomatic suture, which was easily identified on all specimens. Although this keyhole center was slightly more superior on right sides than left, this was not statistically significant. In a minority of specimens, the keyhole was located near the meningo-orbital foramen (22%) and the lateral extent of the frontal sinus (2%)., Conclusions: We defined an alternative method for locating the MacCarty keyhole, based on a reliable external landmark, approximately 7 mm superior and 5 mm posterior to the frontozygomatic suture.

Background: To examine the strength and tolerance of the fibrin glue sealant in a situation of extended transsphenoidal surgery. The withstand pressure of fibrin glue sealant was measured using a simple sellar reconstruction model., Methods: A 15-mm diameter hole at the bottom of a 51-cm high cylinder was covered with a Gore-Tex (Gore-Tex, Tokyo, Japan) sheet. A small plate was placed on the center for a brief fixation, and 3 mL of fibrin glue was applied over the entire bottom. Then water was gradually filled in five cylinders, and the water level at leakage was measured as withstand pressures at 10 minutes and 24 hours after sealant application. The stability of the sealant under pressures of 20 and 30 cm H(2)O for 12 hours was also examined., Results: The median initial withstand pressure at 10 minutes was 32 cm H(2)O (n = 5), and was significantly increased to 47.5 cm H(2)O after 24 hours (n = 4). In four of five cylinders, fibrin glue sealants were stable against a pressure of 20 cm H(2)O for 12 hours and 30 cm H(2)O for the next 12 hours., Conclusions: The withstand pressure of simple fibrin glue sealant without other biological reactions could be estimated to be more than 20 cm H(2)O after application, and increased to more than 40 cm H(2)O after 24 hours. These data are practical for neurosurgeons to comprehend the strength and limit of fibrin glue sealant and suggests the importance to control the intracranial pressure to less than 20 cm H(2)O, especially for the first 12 to 24 hours., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Background: The significance of medial and lateral opticocarotid recesses and the planum sphenoidale region in skull base pathologies for the transsphenoidal-transplanum approach were evaluated., Methods: The sphenoid bone block samples were extracted from adult cadavers. Dissections and measurements in the opticocarotid and planum sphenoidale regions were performed in 29 samples using a surgical microscope. For histologic evaluation, oblique sections through the bilateral opticocarotid regions were obtained and examined in eight samples., Results: Optic, carotid prominences, and medial and lateral opticocarotid recesses can be identified as lateral markers intraoperatively to the extent of the exposure. The lateral opticocarotid recess was observed to be prominent in all samples. In all samples, the groove formed by optic and carotid prominences between the medial and lateral opticocarotid recesses was seen. This groove was designated the inter-recess sulcus. In the transsphenoidal-transplanum approach, the area needed for a reliable bone resection was measured as a mean of 237.32 ± 30.96 mm(2). The mean angle between optic nerves was 115.41 ± 18.39 degrees. The mean anteroposterior length of the planum sphenoidale was 14.84 ± 1.52 mm. In histologic sections, collagenous ligaments between the anterior part of cavernous sinus and the adventitia layer of internal carotid artery were more frequent and regular than the inferior part of optic nerve., Conclusions: The lateral opticocarotid recess is a reliable and persistent indicator for extended transsphenoidal surgery. To approach the opticocarotid region near the internal carotid artery and optic nerve, a careful dissection is needed to minimize surgical injuries to the optic nerve and carotid artery. Other factors determining a reliable bone resection are the anteroposterior length of the planum sphenoidale and the distance and width of the angle between optic nerves. Attention should be given to individual anatomic variations of the region when planning and performing transsphenoidal-transplanum surgery., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Objective: To describe the technical details of a 3-piece orbitozygomatic approach., Introduction: In a 3-piece orbitozygomatic approach, soft tissue exposure is mostly comparable to the classic frontopterional approach. Osseous resection is a 3-piece operation that consists of first performing anterior and posterior cuts along the zygomatic arch, reflecting it down, attached to the masseter. This is followed by a classic frontotemporosphenoidal craniotomy, and finally, an osteotomy of the orbital rim, roof, and lateral wall of the orbit., Results: When compared with its 1- and 2-piece counterparts, 3-piece orbitozygomatic craniotomy, as described here, is a relatively simple operation and is thus advisable when considering an anterior or middle fossa approach. Brain exposure is wide, whereas cerebral retraction is minimal. We recommend avoiding orbit sectioning as deep as the superior orbital fissure., Conclusion: The modifications described herein show the technical features of the 3-piece orbitozygomatic approach, which provides excellent brain exposure with less retraction and a good cosmetic result.

Aim: The purpose of this study was to provide practical anatomic data for imaging diagnosis of olfactory pathways and operation of nasal cavity and anterior cranial fossae., Methods: Sectional anatomy of olfactory pathways were investigated specially on 17 sets of Chinese adult cadavers and 9 sets of serial magnetic resonance (MR) imaging of normal adult on serial transverse, sagittal and coronal sections respectively., Results: We recognized olfactory bulb, olfactory tract, medial and lateral olfactory striae, olfactory trigone, anterior perforated substance and piriform lobe on transverse, sagittal and coronal sections respectively. On the 5-7 serial coronal sections from crista galli of ethmoid bone to the optic chiasm, the cusp ellipse olfactory bulb and the triangular tract were situated in the shallow part of the olfactory sulcus., Conclusion: The olfactory bulb and olfactory tract lay tightly on the ethmoidal cribriform plate and jugum sphenoidale, in the olfactory cistern of the shallow part of the olfactory sulcus, the ethmoid sinus and sphenoid sinus inferiorly.

The frontal-nasal-orbital craniotomy has been utilized for craniofacial abnormalities and resection of tumors involving the anterior skull base. We describe modifications of this technique to approach extra-axial and intradural midline lesions of the anterior fossa with or without involvement of the skull base. A craniotomy was planned with an endoscope and image guidance. A modified frontal-nasal-orbital craniotomy encompassing the entire frontal sinus complex was performed in conjunction with osteotomies incorporating the bilateral superior orbital ridges and nasal septum. Removal of the posterior wall of the frontal sinus was completed if necessary. Dural repair and final reconstruction are detailed. Our initial experience using this approach in five patients harboring lesions of the anterior skull base resulted in adequate exposure of the targeted pathology. There were no complications of the procedure. Cosmetic results were acceptable. We present a detailed account of this procedure via photographs and a video. The frontal-nasal-orbital craniotomy provides access to the floor of the anterior fossa while avoiding excessive brain retraction associated with facial incisions. In addition, this approach is associated with a lower incidence of complications, such as CSF leak, brain retraction edema, or infection. The frontal-nasal-orbital craniotomy is a useful technique for midline lesions of the anterior skull base, and it should be in the armamentarium of neurological surgeons.

Injectable fillers allow for augmentation of soft tissue deficiencies caused by aging, trauma or other scarring. Placement of injectable fillers can be performed in the office, safely and with minimal patient downtime. In order to avoid complications from injection of filler substances, the injector must have a thorough knowledge of the applied anatomy. The temple and forehead are often associated with aging changes. This article describes the anatomic layers of the forehead and temple, and discusses the various planes for safe injection of fillers.

Objectives/hypothesis: Operative intervention of anterior skull base lesions is challenging. Various endoscopic surgical approaches have been described. The goal of the present study is to perform a radiographic analysis of the endoscopic transnasal approach to the clivus., Study Design: Anatomic study utilizing computed tomography (CT)., Methods: High-resolution surgical-guidance CT images of the sinuses from 97 patients at a tertiary care medical center between 2002 and 2007 were evaluated. Axial and sagittal images were used to evaluate surgical access to the clivus. Multiple anatomical measurements were obtained and analyzed with imaging and statistical software., Results: Of the 97 imaging studies, there were 39 males and 58 females. The width of exposure of the clivus without removal of the septum was 2.7 cm (1.9-3.4 cm) and with removal of the bony septum was 3.6 cm (2.6-4.8 cm) (P < .001). No patients had complete exposure of the width of the clivus without the septum removed compared to 56 (58%) patients with the septum removed. Endoscopic exposure of the inferior and superior limits of the clivus was not limited in any images studied., Conclusions: The endoscopic transnasal approach to the clivus is a viable option in the treatment of anterior skull base lesions with the preservation of functional anatomy in select patients. A large portion of the population has limited lateral exposure secondary to the eustachian tube and the medial pterygoid plate with an endoscopic transnasal approach. Vertically, this approach allows complete access to the clivus in all patients studied.

Objective: Resection of the anterior clinoid process (ACP) for the clipping of an internal carotid-posterior communicating artery aneurysm is rarely needed. However, preoperative awareness of the necessity of anterior clinoidectomy is essential for safe clipping of the lesions. We investigated the preoperative predictive value for anterior clinoidectomy in treating internal carotid-posterior communicating artery aneurysms., Methods: We retrospectively reviewed all patients with a posterior communicating artery aneurysm treated with clipping in the past 5 years. Only the patients who underwent both computed tomographic angiography and 4-vessel digital subtraction angiography were included in this study. We measured several angles and distances on these images, and compared the parameters measured between an anterior clinoidectomy group and a non-anterior clinoidectomy group. A P value of less than 0.05 was considered significant., Results: We examined 94 cases of posterior communicating artery aneurysms treated with clipping. The ACP was resected in 6 of the 94 cases. In the anterior clinoidectomy group, there were 3 factors that were statistically significant. First, the calculated real distance between the ACP and the aneurysmal neck was shorter (mean, 4.4 +/- 0.7 versus 7.2 +/- 1.4 mm). Second, the angle between vertical line to cranial base and communicating segment of the internal carotid artery (ICA) was larger (mean, 62.5 +/- 4.6 versus 50.9 +/- 10.7 degrees). Third, the angle between the communicating segment and the ophthalmic segment of the ICA was smaller (mean, 66.5 +/- 15.1 versus 84.6 +/- 20.4 degrees)., Conclusion: The anterior clinoidectomy group showed a more tortuous course of intracranial ICA around the ACP than the nonclinoidectomy group. Therefore, measurement of the distal ICA angle is helpful in predicting the necessity of anterior clinoidectomy.

Introduction: The role of the endoscopic management of lesions located in the anterior cranial fossa and skull base continues to expand., Materials and Methods: An endoscopic anatomic study was conducted on cadaver specimens. 10 orbits from 5 cadaveric heads fixed in formalin were examined after the vascular structures had been perfused with colored latex and silicone. Endoscopic dissections were performed using rigid endoscopes of 4 mm diameter, 18 cm length, and equipped with 0 degrees , and 30 degrees lenses, according to the different steps of the anatomic dissection protocol., Results: We have identified and described three endoscopic approaches to the orbit: 1) an inferolateral endoscopic orbital approach (IL-EOA), 2) an endoscopic endonasal medial orbital approach (EEM-OA), and 3) a transcranial key hole endoscopic orbital approach (TCK-EOA)., Discussion: The IL-EOA provides excellent exposure of the temporal compartment of the orbit. In this approach special care should be taken to preserve the ciliary ganglion, the ciliary artery and the ciliary nerves. The EEM-OA offers direct access to the medial and inferomedial orbit, the medial part of the optic nerve and orbital apex through its anteromedial walls. The EEM-OA is simple, relatively quick and has superiority over microsurgical operations by excluding the potential complications of intracranial operations. The EEM-OA is minimally invasive and cosmetically acceptable. The TCK-EOA offers an exposure of the orbital roof and the superior part of the optic nerve as well as other intraorbital structures from above. The TCK-EOA is a potentially safe approach for tumors extending from the orbital wall to the anterior cranial fossa and the parasellar region., (Copyright Georg Thieme Verlag KG Stuttgart. New York.)

Objective: Several variations on the supraorbital craniotomy via a forehead or eyebrow incision have been described in the literature in recent years. A modification of this approach, the transciliary orbitofrontozygomatic approach, has been used by the authors as a minimally invasive method of approaching certain intracranial pathologies. The authors present their experience with this technique in 105 consecutive patients with tumors or aneurysms of the anterior cranial fossa., Methods: A transciliary keyhole approach was used in all cases. From June 1998 to June 2005, 37 tumors, 1 cavernous malformation, and 77 anterior circulation aneurysms were treated (67 females, 38 males; age range, 8-77 years) with an orbitofrontozygomatic approach via an eyebrow incision. Patients were followed by the authors at a single institution for 1 year postoperatively., Results: Of the 105 patients treated with a transciliary orbitofrontozygomatic approach, 2 (1.9%) developed a cerebrospinal leak. Two other patients (1.9%) very early in the series had persistent forehead asymmetry at 1 year postoperatively. Two patients who underwent surgery for a ruptured aneurysm experienced an intraoperative rupture, which was thought to be unrelated to the exposure. None of the operations had to be converted to a pterional craniotomy., Conclusion: This approach was used in 105 consecutive patients who underwent operation for either tumors or aneurysms via an eyebrow incision. The transciliary orbitofrontozygomatic approach is associated with low surgical morbidity. Although experience with this technique is still limited, it is a viable alternative in cases in which the pathology resides in the midline or anterior fossa.

Objective: Few quantitative data are available to describe Kawase's exposure of the posterior fossa. We used a cadaveric model to compare Kawase's and the retrosigmoid approach to the petroclival region., Methods: Eighteen cadaveric specimens were dissected and analyzed (6 retrosigmoid, 6 Kawase's, and 6 retrosigmoid intradural suprameatal approaches). Clival and brainstem working areas and surgical freedom were measured., Results: The retrosigmoid approach provided a significantly larger clival and brainstem working area than Kawase's approach. Surgical freedom at the trigeminal root entry zone, origin of the anterior inferior cerebellar artery, and Dorello's canal was equivalent across approaches. Kawase's approach provided the most surgical freedom at the trigeminal porus. However, the addition of a suprameatal extension significantly improved the surgical freedom provided by the retrosigmoid approach., Conclusion: The retrosigmoid approach is a powerful approach to lesions of the cerebellopontine angle and ventral brainstem. Lesions involving the trigeminal porus and Meckel's cave can be approached through Kawase's approach or a suprameatal extension of the retrosigmoid approach. Kawase's approach is best suited for accessing middle fossa lesions with smaller petroclival components located above the internal auditory canal.

Object: Olfactory groove meningiomas arise in the midline along the dura of the cribriform plate and may reach a large size before producing symptoms. We conducted a retrospective study of patients with these lesions focused on pre- and post-operative investigations for ophthalmological, personality and cognitive disturbances., Methods: The authors reviewed 36 patients with giant olfactory groove meningiomas surgically treated via a bifrontal approach. Ophthalmological evaluation included visual acuity, fundoscopy and visual fields while psychological evaluation included a Mini-Mental State Examination. Data was collected before, 1 and 12 months after surgery. Formal pre- and post-operative ophthalmological examinations discovered visual deficits in 55.5% of the patients. Within the first month after surgery, improvement of visual acuity and of visual field deficits was observed. In post-operative neuropsychological testing, higher mental functions showed improvement. The most frequent post-operative complication was persistent rhinorrhoea in two patients., Conclusions: Results at longest follow up indicate that cognitive changes and visual deficits will improve in patients with giant olfactory groove meningiomas after a bifrontal approach, without additional neurological deficits.

Introduction: Literature specifically focusing on clinoidal meningiomas is scant, particularly with regards to the postoperative visual outcome. In this study, we aimed to document the incidence of optic canal involvement (OCI) by the tumor, its management using a skull base technique, and its significance with relation to the visual outcome., Materials and Methods: Fifty-two patients with clinoidal meningiomas were retrospectively analyzed. In 47 patients, skull base technique consisting of extradural anterior clinoidectomy with falciform ligament and optic nerve sheath opening was performed. Pre-operative visual status and post-operative outcome were analyzed with respect to OCI., Results: The incidences of OCI was present in 19 (36%) and pre-operative visual deficit (VD) in 24 (46%) patients. With regard to pre-operative visual status, OCI was seen in 14 (58%) of 24 patients with VD, as compared to five (18%) in 28 patients without (p = 0.004). Among the 22 patients with VD and detailed postoperative neuro-ophthalmological evaluation, 17 (77%) had visual improvement, and in five patients (23%), vision was unchanged. In the presence of OCI in 11 patients, vision improved in seven (64%), and remained unchanged in four patients (36%), whereas all but one of the 11 patients (91%) without OCI improved and in the remaining one (9%), remained unchanged. Simpson Grade I and II resection was achieved in 71%., Conclusion: OCI is observed in 36% of clinoidal meningiomas, and it correlates well with pre-operative visual status. With the use of the skull base technique, without which the tumor in the optic canal could not have been removed completely and safely, visual improvement of 77% and stability of 23% was achieved.

The cranial base is one of the major foci of interest in functional craniology. The evolution and morphogenesis of this structure are still poorly known and rather controversial because of multifactorial influences and polyphasic stages. Endocranial dynamics are associated anteriorly with the upper facial structures, laterally with the mandibular system and midsagittally with brain development. In the present study, we investigated the endocranial morphology of modern humans using 3D landmark-based approaches, i.e. geometric morphometrics and Euclidean distance matrix analysis. The structure of endocranial variation is poorly integrated, with only weak reciprocal influences among the three fossae. Some major variations are associated with changes in the posterior fossa, with possible consequences on the anterior areas. These main patterns of integration are hypothesized to be influenced by the connective tensors of the dura layers. Static allometry and sex differences are largely related to the ontogenetic sequences, characterized by early maturation of the anterior fossa with respect to the middle and posterior regions (i.e., relatively shorter posterior part of the planum sphenoideum and vertical lengthening of the clivus in males). The relative independence between the endocranial fossae, as well as their structural connection through the meningeal tensors, must be carefully considered in studies on the evolutionary dynamics, since they lead to mosaic changes through phylogeny.

Objective: Access to the high cervical internal carotid artery (ICA) is technically challenging for the treatment of lesions in and around this region. The aims of this study were to analyze the efficacy of approaching the high cervical ICA through the retromandibular fossa and to compare preauricular and postauricular incisions. In addition, the relevant neural and vascular structures of this region are demonstrated in cadaveric dissections., Methods: The retromandibular fossa approach was performed in four arterial and venous latex-injected cadaveric heads and necks (eight sides) via preauricular and postauricular incisions. This approach included three steps: 1) sternocleidomastoid muscle dissection; 2) transparotid dissection; and 3) removal of the styloid apparatus and opening of the retromandibular fossa to expose the cervical ICA with the internal jugular vein along with Cranial Nerves X, XI, and XII., Results: The posterior belly of the digastric muscle and the styloid muscles were the main obstacles to reaching the high cervical ICA. The high cervical ICA was successfully exposed through the retromandibular fossa in all specimens. In all specimens, the cervical ICA exhibited an S-shaped curve in the retromandibular fossa. The external carotid artery was located more superficially than the ICA in all specimens. The average length of the ICA in the retromandibular fossa was 6.8 cm., Conclusion: The entire cervical ICA can be exposed via the retromandibular fossa approach without neural and vascular injury by use of meticulous dissection and good anatomic knowledge. Mandibulotomy is not necessary for adequate visualization of the high cervical ICA.

Objectives: With a new intraoperative computed tomography (CT) imaging system, patient-to-image registration without any invasive registration markers is possible. Furthermore, registration can be performed fully automatically. The accuracy of this method for skull base surgery was investigated in this study., Methods: We employed a phantom study design. A phantom skull was equipped with 33 target markers in the regions of the anterior and lateral skull base. CT image data were acquired with an intraoperative CT suite. Image data were transferred as DICOM data to the navigation system, and registration was performed automatically. For registration, the position of the patient and the position of the CT gantry were monitored in the imaging process, using the infrared camera of a navigation system. Using the pointing device of the navigation system, the target markers were identified. The accuracy was measured as the spatial difference of the target markers in image space and on the phantom., Results: Accuracy was always sufficient for image-guided surgery of any region of the skull base, with an average target registration error of below 1.2 mm. In contrast to traditional non-invasive registration methods, there was no difference in registration accuracy between the anterior skull base and the lateral skull base., Conclusions: Fully automated registration based on a tracked CT gantry is a robust and accurate registration method for skull base surgery.

Objective: The aim of this work was to determine reliable bony landmarks for the anterior skull base and to standardize some specific dimensions among the frontal sinus and neighboring structures for safe anterior cranial surgery., Methods: The study consisted of a topographical anatomic examination and cephalometric analysis of the skull. Thirty adult skulls (60 sides) were studied regarding the localization and dimensions of the supraorbital foramen (SOF), frontal sinus (FS), frontozygomatic fissure, infraorbital foramen, anterior nasal spine, and nasion. Differences between the measurement of skulls and cephalograms were analyzed by Student's t test. The Pearson correlation test was used for statistical analysis of the cephalogram., Results: Examination of the 60 sides of the bony heads revealed that the shape of the SOF was a foramen in 25 sides (41%), a notch in 29 sides (49%), and a groove in 6 sides (10%). A total of 20 (33%) SOFs were inside the FS and the mean distance was 6.3+1.34 mm from the lateral border of the sinus, 27 (45%) of SOFs were outside of the FS and the mean distance was 8.8+2.01 mm, and 13 (22%) of SOFs were at the border of the FS. According to our measurements the medial border of the craniotomy should be placed approximately 43 mm lateral to the nasion to avoid entering into the frontal sinus., Conclusion: To plan and to decide the convenient and safe anterior midline skull base approach and to avoid postoperative complications, bony landmarks and anatomic measurements around the SOF and FS will be helpful for the surgeon to constitute a simplification of topographic anatomy.

The pterygopalatine fossa (PPF) is a small anatomic region of particular interest in cranial base surgery. Infectious diseases and malignancy may spread through the PPF to contiguous areas as a result of the low resistance offered by the numerous foramina and fissures that surrounds the fossa. We present an anatomic report on the PPF. Twelve sides of six fixed cadaveric heads were dissected through a LeFort I maxillary osteotomy with transantral exposure of the neurovascular content of the PPF. Arterial vascular patterns of the maxillary artery were observed. The pterygopalatine fossa is a deeply located small anatomic region with a rich neurovascular content. The third portion of the maxillary artery in the PPF may demonstrate a variable vascular morphology. A correct understanding and knowledge of the anatomic structures lodged into the PPF, as well as their relationships and functions, remain crucial to minimizing postsurgical morbidity and intraoperative complications.

Background: Different retractors including high-technology products were proposed for neurosurgical interventions. The sponge, having characteristics of deformability and resistance to compression, might be an alternative retractor for the neurosurgical era., Methods: Sponge obtainable from the ordinary market was broken into pieces and sterilized by ethylene oxide. During intervention, the appropriate sponge pieces were applied inside the dissected sulci for the purpose of retraction., Results: The sponge pieces were easily applied and supplied optimal retraction during operations. Proximal application to the dissected sylvian fissure enabled the exposure of the inner distal part including the insular surface, whereas application between the frontobasal surface and the orbital roof provided satisfactory exposure of the suprachiasmatic area. The retraction capacity of the sponge was less than that of self-retaining Leyla retractors, but the postoperative appearance of cortical surfaces was fine without any bruising or hyperemia., Conclusion: The sponge material, with its inner mechanical characteristics and ease of application like cotton pads, seems to be an alternative retractor in neurosurgical interventions, and these characteristic may inspire development of new high-technology retractors.

Background: Although resection of the anterior clinoid process (ACP) is valuable in the surgical treatment of aneurysms of the ophthalmic (C6) segment of the internal carotid artery (ICA), quantitative assessment of this adjunct is incomplete. Our morphometric study assesses the effectiveness of the anterior clinoidectomy for exposure of the C6 segment of the ICA., Methods: Ten formalin-fixed adult cadaveric heads were dissected bilaterally and pterional craniotomies were performed bilaterally. Measurements before and after resection of the ACP included the length of C6 segment of the ICA on its lateral aspect; C6 segment length on its medial aspect; and medial length of the optic nerve from the optic chiasm to falciform ligament (before ACP resection) then to the annulus of Zinn (after ACP resection)., Findings: Height and width of the intradural ACP were 8.67 +/- 2.63 and 6.57 +/- 1.68 mm, respectively. After clinoidectomy, mean length of the lateral C6 segment of the ICA increased 60% and mean exposure of the medial C6 segment of the ICA increased 113% (p < 0.001). Exposure of the optic nerve increased 150% (p < 0.001) after clinoidectomy and sectioning of the falciform ligament. No correlations were found between the lengths of the ACP and entire C6 segment, or the ACP size and amount of the C6 segment covered by the clinoid., Conclusions: Exposure of the C6 segment of the ICA is markedly increased by increase of the mobility of the optic nerve with clinoidectomy and section of the falciform ligament.

Objective: Many approaches have been recommended for the surgical treatment of anterior and middle cranial fossa lesions. The frontobasal approach and its many modifications have been proposed and developed for such situated lesions. An alternative approach is the frontolateral craniotomy through a supraciliary skin incision., Methods: This minimally invasive technique, a 2.5 x 3.0 cm craniotomy, just above the eyebrow through a supraciliary incision, is a simple but elegant modification of the traditional approach to the anterior cranial fossa., Results: A step-by-step description of the approach is offered in this report to facilitate a clear understanding of the lesions treatable with this minimally invasive technique., Conclusion: The supraciliary frontolateral keyhole craniotomy is a minimally invasive cosmetic approach that provides excellent exposure to a variety of intracranial lesions. This approach cannot be used for all intracranial pathologies, but is recommended for many anterior and middle cranial fossa lesions.

Clinoidal meningiomas, also referred to as medial or inner sphenoid wing meningiomas, are often difficult and challenging to remove completely and safely, especially when they become large enough to encircle, compress, or displace the adjacent critical neurovascular structures such as the optic nerve, the internal carotid artery and its branches, and the oculomotor nerve. In this article, the authors describe the detailed surgical technique used in their practice in addition to subtle nuances learned from their experience of operating on more than 40 patients with clinoidal meningiomas over the past several years. The primary goals of surgery are to achieve aggressive tumor removal with avoidance of intraoperative morbidity and, in addition, for those with preoperative compromised vision, to provide improvement in their visual function after surgery.

Background: Distal anterior cerebral artery (DACA) aneurysms are uncommon. Most authors have reported technical difficulties during surgery for these aneurysms, and a variety of surgical approaches have been advocated., Methods: Over a period of 5 years (1999-2003), 67 patients with DACA aneurysms were operated. Twenty-eight of these were operated on through the bifrontal basal anterior interhemispheric approach. Of the 28 patients, 68% were in poor clinical grade (Hunt and Hess grade III-V) and 89.3% had a Fisher grade III and IV on computed tomography scan. A surgical trajectory about 2 to 3 cm superior to the anterior cranial fossa floor led directly to the aneurysm. Proximal control was achieved before aneurysm dissection and parallel clipping., Results: Good outcome (Glasgow Outcome Scale V and IV) was seen in 57.19 of the patients, 14.3% had a poor outcome, and 28.6% died. The cause of death in most patients was found to be a poor clinical grade, postoperative infarct, or presence of multiple aneurysms., Conclusions: The advantages of the bifrontal basal anterior interhemispheric approach were the following: (a) It provided the shortest and a direct trajectory to the aneurysm. (b) Proximal control of the parent A(2) vessels could be easily achieved. (c) Release of cerebrospinal fluid from basal cisterns could be done, if necessary. (d) There was a minimal distortion of or traction over the aneurysm.