Matteo de Notaris

Impairment of Olfaction and Mucociliary Clearance After Expanded Endonasal Approach Using Vascularized Septal Flap Reconstruction for Skull Base Tumors

BACKGROUND Endoscopic skull base surgery is now the preferred treatment option to remove skull base tumors. OBJECTIVE To evaluate the patients sense of smell and mucociliary clearance time (MCT) after skull base surgery. METHODS Patients with pituitary adenoma underwent a transnasal transsphenoidal endoscopic approach (TTEA group, n = 36), whereas patients with other benign parasellar tumors underwent an expanded endonasal approach (EEA group, n = 14) with a vascularized septal flap. Assessment of symptoms (Visual Analogue Scale), olfactometry (Barcelona Smell Test, BAST-24), and MCT (saccharin test) were performed before and 3 months after surgery. RESULTS Before surgery, patients reported poorer BAST-24 scores on detection, identification, and forced choice than the healthy population, but both study groups had similar sinonasal symptoms, BAST-24, and MCT scores. After surgery, no changes in symptom scores (Visual Analogue Scale) were observed except for the loss of smell (26.7 ± 30.5 mm, P < .05) and posterior nasal discharge (29.7 ± 30.3 mm, P < .05) compared with baseline (5.2 ± 11.3, 19.1 ± 25.3, respectively). EEA patients reported higher loss of smell and posterior nasal discharge compared with TTEA. TTEA and EEA groups had similar scores on postoperative BAST-24. After surgery, however, patients showed prolonged saccharin test (15.6 ± 10.8 min, P < .05) compared with baseline (8.4 ± 4.4 min). In addition, EEA patients reported longer MCT than TTEA patients. CONCLUSION EEA but not TTEA has a short-term (3 months) negative impact on patients olfaction and mucociliary clearance. Patients should be informed about smell loss as a consequence of skull base surgery to prevent legal claims. Likewise, further research and some modifications on reconstruction flaps are encouraged to avoid damaging the olfactory neuroepithelium.

Endoscopic endonasal transclival approach and retrosigmoid approach to the clival and petroclival regions.

OBJECTIVE The removal of clival lesions, mainly those located intradurally and with a limited lateral extension, may be challenging because of the lack of a surgical corridor that would allow exposure of the entire lesion surface. In this anatomic study, we explored the clival/petroclival area and the cerebellopontine angle via both the endonasal and retrosigmoid endoscopic routes, aiming to describe the respective degree of exposure and visual limitations. METHODS Twelve fresh cadaver heads were positioned to simulate a semisitting position, thus enabling the use of both endonasal and retrosigmoid routes, which were explored using a 4-mm rigid endoscope as the sole visualizing tool. RESULTS The comparison of the 2 endoscopic surgical views (endonasal and retrosigmoid) allowed us to define 3 subregions over the clival area (cranial, middle, and caudal levels) when explored via the endonasal route. The definition of these subregions was based on the identification of some anatomic landmarks (the internal carotid artery from the lacerum to the intradural segment, the abducens nerve, and the hypoglossal canal) that limit the bone opening via the endonasal route and the natural well-established corridors via the retrosigmoid route. CONCLUSION Different endoscopic surgical corridors can be delineated with the endonasal transclival and retrosigmoid approaches to the clival/petroclival area. Some relevant neurovascular structures may limit the extension of the approach and the view via both routes. The combination of the 2 approaches may improve the visualization in this challenging area.

Preliminary experience with a new three-dimensional computer-based model for the study and the analysis of skull base approaches.

PurposeThe goal of the present study was to develop a three-dimensional (3D) geometrical model based on pre- and post-dissection Digital Imaging and Communication in Medicine (DICOM) images of both transcranial and endonasal skull base approaches. Such model was structured for either teaching surgical anatomy and to evaluate the amount of bone removal over the skull base surface through a 3D digital perspective.MethodsTwenty-five human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy (LSNA) of the University of Barcelona (Spain) between 2007 and 2009. Before and after each dissection, a computed tomography-scan (CT-scan) was obtained in order to create a 3D geometrical model of the same approach performed in the dissection laboratory. The model protocol was designed as follows: (1) preoperative CT-scan of the specimens; (2) creation of a computer-generated 3D model of the specimen using specific imaging software for visualization and manipulation of biomedical data; (3) dissection of the specimens; (4) development of a 3D CT-based model of the approach as a result of the overlapping of the DICOM data of the specimens before and after the dissection.ResultsThe fusion of the pre- and post-dissection 3D models allowed evaluation of the amount of bone removal over the skull base surface.ConclusionsMeasurements of the bony landmarks as well as the visual feedback of the drilled bone over the skull base provided by our 3D model gives the opportunity to improve the tailoring of each approach to the different skull base areas.

The use of a three-dimensional novel computer-based model for analysis of the endonasal endoscopic approach to the midline skull base.

OBJECTIVES To apply a three-dimensional geometric model to various endoscopic endonasal approaches to analyze the bony anatomy of this area, quantify preoperatively bone removal, and optimize surgical planning. METHODS Investigators dissected 18 human cadaveric heads at the Laboratory of Surgical NeuroAnatomy (LSNA) of the University of Barcelona (Spain). Before and after each dissection, a computed tomography (CT) scan was performed to create a three-dimensional geometric model of the approach performed in the dissection room. The model protocol was designed as follows: (i) a preliminary exploration of each specimen using the preoperative CT scan, (ii) creation of a computer-generated three-dimensional virtual model of the approach, (iii) cadaveric anatomic dissection, and (iv) development of a CT-based model of the approach as a result of the superimposition of predissection and postdissection digital imaging and communications in medicine (DICOM) images of specimens. RESULTS This method employing preliminary virtual exploration of each specimen, the creation of a three-dimensional virtual model of the approach, and the overlapping of the predissection and postdissection three-dimensional models was useful to define the exact boundaries of the endoscopic endonasal craniectomy. CONCLUSIONS Aside from laboratory anatomic dissection itself, this model is very effective in providing a depiction of bony landmarks and visual feedback of the amount of bone removed, improving the design of the craniectomy in the endoscopic endonasal midline skull base approach.

Improved Assessment of Ex Vivo Brainstem Neuroanatomy With High-Resolution MRI and DTI at 7 Tesla

The aim of the present work was to provide the topography of the main gray nuclei and white matter tracts of the human brainstem at 7 Tesla (7 T) high‐field magnetic resonance imaging (MRI) using structural imaging (T1) and diffusion tensor imaging (DTI). Both imaging techniques represent a new field of increasing interest for its potential neuroanatomic and neuropathologic value. Brainstems were obtained postmortem from human donors, fixated by intracarotid perfusion of 10% neutral buffered formalin, and scanned in a Bruker BioSpec 7 T horizontal scanner. 3D‐data sets were acquired using the modified driven equilibrium Fourier transform (MDEFT) sequence and Spin Echo‐DTI (SE‐DTI) sequence was used for DTI acquisition. High‐resolution structural MRI and DTI of the human brainstem acquired postmortem reveals its basic cyto‐ and myeloar‐chitectonic organization, only visualized to this moment by histological techniques and higher magnetic field strengths. Brainstem structures that are usually not observed with lower magnetic fields were now topographically identified at midbrain, pons, and medullar levels. The application of high‐resolution structural MRI will contribute to precisely determine the extension and topography of brain lesions. Indeed, the current findings will be useful to interpret future high‐resolution in vivo MRI studies in living humans. Anat Rec, 2011.

Functional anatomy of subcortical circuits issuing from or integrating at the human brainstem

The functional organization of the main human brainstem centers and circuits are described as revealed in post-mortem material with high-resolution structural magnetic resonance imaging (MRI), diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) acquired at ultra-high magnetic field 7 T. The description is complemented with a conventional in vivo fiber tracking study of the descending motor pathways. This type of neuroanatomic depiction of nuclei and nerve tracts at very high spatial resolution opens new possibilities to analyze the fine structure and circuits of the human brainstem, at least in post-mortem material.

Endoscopic endonasal anatomy of superior orbital fissure and orbital apex regions: critical considerations for clinical applications.

The superior orbital fissure is a critical three-dimensional space connecting the middle cranial fossa and the orbit. From an endoscopic viewpoint, only the medial aspect has a clinical significance. It presents a critical relationship with the lateral sellar compartment, the pterygopalatine fossa and the middle cranial fossa. The connective tissue layers and neural and vascular structures of this region are described. The role of Muller’s muscle is confirmed, and the utility of the maxillary and optic strut is outlined. Muller’s muscle extends for the whole length of the inferior orbital fissure, passes over the maxillary strut and enters the superior orbital fissure, representing a critical surgical landmark. Dividing the tendon between the medial and inferior rectus muscle allows the identification of the main trunk of the oculomotor nerve, and a little laterally, it is usually possible to visualize the first part of the ophthalmic artery. Based on a better knowledge of anatomy, we trust that this area could be readily addressed in clinical situations requiring an extended approach in proximity of the orbital apex.

Anatomic skull base education using advanced neuroimaging techniques.

OBJECTIVE The goal of the present article was to describe our dissection training system applied to a variety of endoscopic endonasal approaches. It allows one to perform a 3D virtual dissection of the desired approach and to analyze and quantify critical surgical measurements. METHODS All the human cadaveric heads were dissected at the Laboratory of Surgical Neuro-Anatomy (LSNA) of the University of Barcelona (Spain). The model surgical training protocol was designed as follows: 1) virtual dissection of the selected approach using our dissection training 3D model; 2) preliminary exploration of each specimen using a second 3D model based on a preoperative computed tomographic scan; 3) cadaveric anatomic dissection with the aid of a neuronavigation system; and 4) quantification and analysis of the collected data. RESULTS The virtual dissection of the selected approach, preliminary exploration of each specimen, a real laboratory dissection experience, and finally, the analysis of data retrieved during the dissection step was a complete method for training manual dexterity and hand-eye coordination and to improve the general knowledge of surgical approaches. CONCLUSIONS The present model results are found to be effective, providing a valuable representation of the surgical anatomy as well as a 3D visual feedback, thus improving study, design, and execution in a variety of approaches. Such a system can also be developed as a preoperative planning tool that will allow the neurosurgeon to practice and manipulate 3D representations of the critical anatomic landmarks involved in the endoscopic endonasal approaches to the skull base.

The trochlear nerve: microanatomic and endoscopic study.

The purpose of the present study was to analyze the relationships of the trochlear nerve with the surrounding structures through both endoscopic and microscopic perspectives. The aim was to assess the anatomy of the nerve and to carry out a thorough description of its entire course. A comprehensive anatomically and clinically oriented classification of its different segments is proposed. Forty human cadaveric fixed heads (20 specimens) were used for the dissection. The arterial and venous systems were injected with red and blue colored latex, respectively, in the transcranial dissection. For illustrative purposes, the arterial vessels were injected alone in endoscopic endonasal procedures. A CT scan was carried out on every head. Median supracerebellar infratentorial, subtemporal, fronto-temporo-orbito-zygomatic, and endoscopic endonasal transsphenoidal approaches were performed to expose the entire pathway of the nerve. A navigation system was used during the dissection process to perform the measurements and postoperatively to reconstruct, using dedicated software, a three-dimensional model of the different segments of the nerve. The trochlear nerve was divided into five segments: cisternal, tentorial, cavernous, fissural, and orbital. Detailed and comprehensive examination of the basic anatomical relationships through the view of transcranial, endoscope-assisted, and pure endoscopic endonasal approaches was achieved. As a result of a thorough study of its intra- and extradural pathways, an anatomic-, surgically, and clinically based classification of the trochlear nerve is proposed. Precise knowledge of the involved surgical anatomy is essential to safely access the supracerebellar region, middle fossa, parasellar area, and orbit.

A three-dimensional computer-based perspective of the skull base.

OBJECTIVE To describe our designed protocol for the reconstruction of three-dimensional (3D) models applied to various endoscopic endonasal approaches that allows performing a 3D virtual dissection of the desired approach and analyzing and quantifying critical surgical landmarks. METHODS All human cadaveric heads were dissected at the Laboratory of Surgical Neuroanatomy of the University of Barcelona. The dissection anatomic protocol was designed as follows: 1) virtual surgery simulation systems, 2) navigated cadaver dissection, and 3) postdissection analysis and quantification of data. RESULTS The virtual dissection of the selected approach, the preliminary exploration of each specimen, the real dissection laboratory experience, and the analysis of data retrieved during the dissection step provide a complete method to improve general knowledge of the main endoscopic endonasal approaches to the skull base, at the same time allowing the development of new surgical techniques. CONCLUSIONS The methodology for surgical training in the anatomic laboratory described in this article has proven to be very effective, producing a depiction of anatomic landmarks as well as 3D visual feedback that improves the study, design, and execution in various neurosurgical approaches. The Dextroscope as a virtual surgery simulation system can be used as a preoperative planning tool that can allow the neurosurgeon to perceive, practice reasoning, and manipulate 3D representations using the transsphenoidal perspective acquiring specifically visual information for endoscopic endonasal approaches to the skull base. The Dextroscope also can be used as an advanced tool for analytic purposes to perform different types of measurements between surgical landmarks before, during, and after dissection.