Carolina Martins

Working area and angle of attack in three cranial base approaches

OBJECTIVE This study was designed to quantify the operative exposure obtained in the pterional, orbitozygomatic, and modified orbitozygomatic with maxillary extension surgical approaches. METHODS The pterional and orbitozygomatic approaches and a variation of the orbitozygomatic osteotomy that included an extra centimeter of bone resection in the inferior direction (“maxillary extension”) were performed on cadaveric heads. For each surgical exposure, the working area was determined by using triangles defined with anatomic points. The “angle of attack” of the approaches for the same target point was determined with the use of a robotic microscope. RESULTS The maximum allowable angle of attack was significantly greater with the orbitozygomatic approach (37.2 ± 4.7 degrees) than that with the pterional approach (27.1 ± 4.3 degrees) (P < 0.001). The angle of attack with the maxillary extension (42.0 ± 4.9 degrees) was significantly greater than that with the orbitozygomatic approach (P < 0.001). The working areas were 281, 343, and 371 mm2 for the pterional, orbitozygomatic, and maxillary extension approaches, respectively. The orbitozygomatic approach with maxillary extension had a significantly larger working area than the pterional approach (P = 0.011). CONCLUSION Increments in bony removal open a wider angle in which to work more than they increase the actual amount of working area. Increasing the amount of bone removed by using an orbitozygomatic approach instead of a pterional approach converts a narrow space into a wide portal, allowing surgeons to work closer to the surgical target while decreasing the need for brain retraction. Extending the orbitozygomatic approach into the maxillary region also improves the exposure area and angle, but less significantly.

Limitations of the transcallosal transchoroidal approach to the third ventricle.

OBJECT The aim of this study was to determine the anatomical limitations of the transcallosal transchoroidal approach to the third ventricle. METHODS Twenty-six formalin-fixed specimens were studied. Sagittal dissections were used to determine the anatomical relationships of the foramen of Monro, the angle of approach to landmarks, and placement of a callosotomy. Lateral ventricular dissections were performed to quantitate the forniceal anatomy. RESULTS The foramen of Monro was found 1.07+/-0.11 cm superior and slightly anterior to the mammillary bodies, 1.48+/-0.16 cm posterosuperior to the optic recess, and 2.26+/-0.16 cm anterosuperior to the aqueduct. Relative to the genu, a callosal incision 2.64+/-0.53 cm long and angled 37+/-4.3 degrees anterior was needed to access the aqueduct, and an incision 4.92+/-0.71 cm long and angled 49+/-7.4 degrees posterior was needed to access the optic recess. The fornix progressively widened within the lateral ventricle, from 1.25+/-0.63 mm at the foramen of Monro to >7 mm at 2 cm behind the foramen. Three zones of exposure were identified, requiring unique craniotomies, callosotomies, and angles of approach. The major limiting factors in the approach included the columns of the fornix anteriorly, the width of the fornix posteriorly, and the draining veins of the parietal cortex. The choroidal fissure opening was limited to 1.5 cm posterior to the foramen of Monro; this limited opening created an aperture effect that required an anterior-to-posterior angle, an anterior craniotomy, and an anteriorly placed callosotomy to access the posterior landmarks. In contrast, a posterior-to-anterior angle, posteriorly placed craniotomy, and posteriorly placed callosotomy were required to access anterior landmarks. CONCLUSIONS The transcallosal transchoroidal approach was ideally suited to access the foramen of Monro and the middle and posterior thirds of the third ventricle. Exposure of the anterior third ventricle was limited by the columns of the fornix and by the presence of parietal cortical draining veins.

Cluster headache and intracranial aneurysm

In the present study we describe the cases of two patients with cluster-like headache related to intracranial carotid artery aneurysm. One of these patients responded to verapamil prescription with headache resolution. In both cases the surgical clipping of the aneurysm resolved the cluster pain. These findings strongly suggest a pathophysiological link between the two conditions. The authors discuss the potential pathophysiological mechanisms underlying cluster-like headache due to intracranial carotid artery aneurysm.

Microsurgical Anatomy of the Orbit: The Rule of Seven

The orbits are paired structures, located on the anterior part of the face. Morphologically, each orbit is a four sided pyramid with a posterior apex and anterior base. In the orbit, all openings are arranged around the base, apex or between the orbital walls. An anatomical characteristic of the orbit is that structures are arranged in groups of seven: there are seven bones, seven intraorbital muscles and seven nerves in the orbit. Tumors confined within the periorbita in the anterior two thirds of the orbit can often be approached extracranially, but those located in the apical area, and especially those on the medial side of the optic nerve, often require a transcranial approach. Thus, knowledge of orbital osteology is paramount in adequately choosing and performing an orbital approach. Understanding the critical topographical elements in this area helps to classify an orbital lesion and provides for a solid basis in choosing the most adequate intraorbital route for its treatment.

Three-piece orbitozygomatic approach.

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.

Hematoma volumes of spontaneous intracerebral hemorrhage: the ellipse (ABC/2) method yielded volumes smaller than those measured using the planimetric method

OBJECTIVE To compare two different methods for measuring intracerebral hemorrhage (ICH) volume: the ellipse volume (called ABC/2), and the software-aided planimetric. METHODS Four observers evaluated 20 brain computed tomography (CT) scans with spontaneous ICH. Each professional measured the volume using the ABC/2 and the planimetric methods. The average volumes were obtained, and the intra- and inter-rater variability was determined. RESULTS There is an absolute 2.24 cm3 average difference between both methodologies. Volumes yielded by the ABC/2 method were as much as 14.9% smaller than by the planimetric one. An intra-observer variability rate of 0.46% was found for the planimetric method and 0.18% for the ABC/2. The inter-observer rates were 1.69 and 1.11% respectively. CONCLUSIONS Both methods are reproducible. The ABC/2 yielded hemorrhage volumes as much as 14.9% smaller than those measured using the planimetric methodology.

Endoscopic-Assisted Lateral Transatlantal Approach to Craniovertebral Junction

BACKGROUND The lateral approach to the craniocervical junction is directed along the atlantal and occipital condyles to the dens. The advantages of the lateral approach compared with the anterior transoral and transnasal approaches are that it provides a sterile field, and anterior decompression and postdecompression fixation can be performed in one procedure. OBJECTIVE To examine the usefulness of endoscopy as an auxiliary tool during lateral transatlantal odontoidectomy. METHODS Six cadaver heads, in which the vessels were injected with colored silicone, were dissected using a surgical microscope and 0- and 30-degree endoscopes. A flap incision was chosen to accomplish exposure of the area of the decompression, the occipital squama and adjacent laminae for fixation, and the vertebral artery from C2 to its dural entrance for its stabilization. RESULTS Study findings revealed that endoscopy adds several advantages to microscopy in the lateral transatlantal approach to the craniovertebral junction in cases of craniovertebral malformation by providing magnification and illumination not limited by corners, thus helping to avert substandard decompression and complications such as dural tears and cerebrospinal fluid leaks; flexibility in surgical positioning of patients; and improved ergonomics that enable the surgeon to complete the procedure in a more efficient, comfortable, and safe manner. CONCLUSION Endoscopy is a useful adjunct to microscopy in completing lateral approaches to the craniovertebral junction.

Three-dimensional digital projection in neurosurgical education: technical note.

Three-dimensional images have become an important tool in teaching surgical anatomy, and its didactic power is enhanced when combined with 3D surgical images and videos. This paper describes the method used by the last author (G.C.R.) since 2002 to project 3D anatomical and surgical images using a computer source. Projecting 3D images requires the superposition of 2 similar but slightly different images of the same object. The set of images, one mimicking the view of the left eye and the other mimicking the view of the right eye, constitute the stereoscopic pair and can be processed using anaglyphic or horizontal-vertical polarization of light for individual use or presentation to larger audiences. Classically, 3D projection could be obtained by using a double set of slides, projected through 2 slide projectors, each of them equipped with complementary filters, shooting over a medium that keeps light polarized (a silver screen) and having the audience wear appropriate glasses. More recently, a digital method of 3D projection has been perfected. In this method, a personal computer is used as the source of the images, which are arranged in a Microsoft PowerPoint presentation. A beam splitter device is used to connect the computer source to 2 digital, portable projectors. Filters, a silver screen, and glasses are used, similar to the classic method. Among other advantages, this method brings flexibility to 3D presentations by allowing the combination of 3D anatomical and surgical still images and videos. It eliminates the need for using film and film developing, lowering the costs of the process. In using small, powerful digital projectors, this method substitutes for the previous technology, without incurring a loss of quality, and enhances portability.

Dural landmark to locate the internal auditory canal in large and giant vestibular schwannomas: the Tübingen line.

BACKGROUND: In cases of large and giant vestibular schwannomas (VS), the visualization of the internal auditory canal (IAC) opening is difficult or impossible. OBJECTIVE: To describe the Tübingen line and explore its relationships with the IAC as a landmark to help locate the IAC. METHODS: Ten cadaveric heads were used in this study. Between 2004 and 2009, the senior author (M.T.) used the Tübingen line as a landmark to recognize the IAC in 300 consecutive patients with VS. To locate the Tübingen line, the initial step was to identify several vertical foldings of dura located around the area of the vestibular aqueduct. After this, foldings upward consistently reached a linear level where all of the foldings ended and the dura tightly adhered to the bony surface in a smooth, foldless shape. RESULTS: The Tübingen line was identified in all temporal bones studied and in all 300 patients operated on, with the exception of 2 cases (<1%). Removal of the bone just above the Tübingen line located the IAC in all temporal bone specimens studied. Similarly, the surgical cases showed that the Tübingen line helped locate the IAC in all patients. CONCLUSION: The Tübingen line is an easy, consistent, and safe method to locate the projection of the IAC along the posterior surface of the temporal bone.

An MCDM project portfolio web-based DSS for sustainable strategic decision making in an electricity company

Purpose The purpose of this paper is to analyze the impacts of Portfolio size effect due to scaling issues in the outcome obtained in a project portfolio selection for an electricity company in Brazil, focusing on improving business strategic performance. Design/methodology/approach The study uses a web-based decision support system (DSS), in which scaling issues are considered, incorporating results of previous work. The study evaluates 32 projects from the electricity company and compared the possible results when considering different scales. Additionally, a sensitivity analysis was conducted to analyze the robustness of the case, using the web-based DSS. Findings The results for an interval scale context showed a portfolio with 21 projects, contrasting with the correct solution of a portfolio containing 23 projects. The latter is related to a ratio scale context, with the proper transformation of weights, which was found to be robust with a sensitivity analysis using Monte Carlo simulation. This demonstrates that only appropriate models for selecting projects can improve the contribution to the company’s permanent strategies of increasing productivity, considering its constraints to achieve optimal results. Originality/value Additive value functions approach imposes certain requirements on the measurement scales used for the items in a portfolio that should not be ignored, once they have significant impact on the general portfolio results, which are directly related to the business strategic performance and the facilities of doing that with a web-based DSS.