Endoscopic Transorbital Approaches to Anterior and Middle Cranial Fossa: Exploring the Potentialities of a Modified Lateral Retrocanthal Approach.

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 cm3, 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.

The Relationship of High Septal Deviation, the Depth of Olfactory Fossa, and Gera Angle: Is High Septal Deviation Associated With Any Anatomic Abnormalities in the Anterior Skull Base?

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.

Comparative anatomical analysis between the minipterional and supraorbital approaches.

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.

Endoscopic transorbital approach to anterolateral skull base through inferior orbital fissure: a cadaveric study.

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.

Morphological variation in the anterior cranial fossa.

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.

Demystifying the "Triple Point: " Technical Nuances of the Fronto-Orbital Advancement.

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.

Anterior Skull Base and Pericranial Flap Ossification after Frontofacial Monobloc Advancement.

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.

The revised anatomy of the canals connecting the orbit with the cranial cavity.

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.

Analysis of the Relationship between the Location of the Anterior Ethmoid Artery and Keros Classification.

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 χ2 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.

Applied anatomy of the anterior cranial fossa: what can fracture patterns tell us?

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.

The Supraorbital Keyhole Approach.

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 ±â€Š4.03  mm on the right side and 31.04 ±â€Š5.40  mm on the left side. The average distance obtained from the autopsies on the 34 males was 34.00 ±â€Š4.59  mm on the right side and 33.59 ±â€Š5.41  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.

Computer-assisted analysis of anatomical relationships of the ethmoidal foramina and optic canal along the medial orbital wall.

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.

Cranial dural arteriovenous shunts. Part 1. Anatomy and embryology of the bridging and emissary veins.

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.

The 1-piece transbasal approach: operative technique and anatomical study.

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.

Anatomy of the adult foramen caecum

The foramen caecum is a hitherto not fully described structure of the base of the anterior cranial fossa. The surroundings of its route are routinely the site of surgical interventions which are preceded by a computer tomography scan. The examination and comparison of the adult foramen caecum anatomy are found in anatomical specimens and in computer tomography images. The measurements of foramen caecum were done using computer tomography images. The anonymous images of 18 adult patients were used, as well as 15 cranium anatomical specimens. Only skulls with an intact foramen caecum region were examined. Tools available in the Clear Canvas Workstation 2,0SP1 were used to conduct measurements of the CT images, while a millimeter scale and a probe inserted into the foramen caecum were used to conduct measurements of the anatomical specimens. The foramen caecum was present in all investigated skulls but with the wide range of proper dimensions. The highest (15 mm) and the lowest depth (4 mm) were found in anatomical specimens. It has been ascertained that the foramen caecum inside bone structure takes the form of a short canal leading to the frontal sinus. The comparison of the results of the measurements of CT images and anatomical specimens revealed that the dimensions of the foramen caecum vary. The examination of each CT image resulted in identification of the foramen caecum (AU)

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Evaluating endoscopic and endoscopic-assisted access to the infratemporal fossa: a novel method for assessment and comparison of approaches.

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.

Preauricular transzygomatic anterior infratemporal fossa approach for tumors in or around infratemporal fossa lesions.

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.

Muller's muscle, no longer vestigial in endoscopic surgery.

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.

Endovascular management of anterior cranial fossa dural arteriovenous malformations. A technical report and anatomical discussion.

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.

Transorbital endoscopic repair of cerebrospinal fluid leaks.

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.