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ABSTRACT: Object This study was designed to determine if the "keyhole concept," proposed by Perneczky's group, can be verified quantitatively. Methods Fourteen (3 bilateral and 8 unilateral) sides of embalmed latex-injected cadaveric heads were dissected via 3 sequential craniotomy approaches: supraorbital keyhole, frontotemporal pterional, and supraorbital. Three-dimensional cartesian coordinates were recorded using a stereotactic localizer. The orthocenter of the ipsilateral anterior clinoid process, the posterior clinoid process, and the contralateral anterior clinoid process are expressed as a center point (the apex). Seven vectors project from the apex to their corresponding target points in a radiating manner on the parasellar skull base. Each 2 neighboring vectors border what could be considered a triangle, and the total area of the 7 triangles sharing the same apex was geometrically expressed as the area of exposure in the parasellar region. Results Values are expressed as the mean ± SD (mm(2)). The total area of exposure was as follows: supraorbital keyhole 1733.1 ± 336.0, pterional 1699.3 ± 361.9, and supraorbital 1691.4 ± 342.4. The area of exposure on the contralateral side was as follows: supraorbital keyhole 602.2 ± 194.7, pterional 595.2 ± 228.0, and supraorbital 553.3 ± 227.2. The supraorbital keyhole skull flap was 2.0 cm(2), and the skull flap size ratio was 1:5:6.5 (supraorbital keyhole/pterional/supraorbital). Conclusions The area of exposure of the parasellar region through the smaller supraorbital keyhole approach is as adequate as the larger pterional and supraorbital approaches. The keyhole concept can be verified quantitatively as follows: 1) a wide area of exposure on the skull base can be obtained through a small keyhole skull opening, and 2) the side opposite the opening can also be visualized.
Journal of Neurosurgery 11/2012; · 2.96 Impact Factor
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ABSTRACT: Surgery to monitor and resect epileptogenic foci may be undertaken in 2 stages, providing an opportunity to use skull-fixated fiducials implanted during the first stage to improve the accuracy of cortical resection during the second stage. This study compared the intrinsic accuracy of skin-based and skull-fixated fiducial markers in registering frameless stereotaxy during pediatric epilepsy surgery. To the authors' knowledge, these modalities of registration have not previously been directly compared in this population.
The authors undertook a retrospective review of pediatric patients who underwent resection of epileptogenic foci in 2 stages with frameless stereotactic assistance, performed by a single surgeon at Oregon Health & Science University. For the first stage (subdural grid implantation), 9 skin fiducial markers were used to register anatomical data in a frameless stereotactic station. Intraoperatively, four 3-mm screws were placed circumferentially around the craniotomy. Postoperatively, thin-slice brain MR and CT images were obtained and fused. For the second stage, the 4 screws were used as fiducial markers to register the stereotactic anatomical data. For both stages, accuracy (difference in millimeters from zero of the manual fiducial registration compared with the computer model) was determined using navigation software. The intrinsic accuracy of these 2 methods of fiducial registration was compared using a paired Student t-test.
Between 2004 and 2009, 40 pediatric patients with epilepsy underwent frameless stereotactic surgical procedures. Fourteen patients who had 2-stage procedures using skin-based and skull-fixated registration with complete accuracy data were included in this retrospective review. Mean registration error was significantly lower using skull-fixated fiducials (1.35 mm, 95% CI 1.09-1.60 mm) than using skin-based fiducials (1.85 mm, 95% CI 1.56-2.13 mm; p = 0.0016).
A significantly higher degree of accuracy was achieved using 4 skull-fixated fiducials compared with using 9 skin-based fiducials. This simple and accurate method for registering frameless stereotactic anatomical data does not involve the potential time, expense, discomfort, and morbidity of extraoperative skull-fixated fiducial placement. The method described in this paper could also be extrapolated to other planned 2-stage cranial surgical procedures such as combined skull base approaches.
Journal of Neurosurgery Pediatrics 01/2011; 7(1):116-9. · 1.53 Impact Factor
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ABSTRACT: The following technical case report illustrates the use of multiple imaging modalities including 3D CTV with frameless stereotactic navigation for intraoperative planning and localization for surgical obliteration of a cranial dAVF with leptomeningeal drainage.
This 65-year-old man presented with an asymptomatic occipital dAVF with leptomeningeal drainage. In addition to cerebral angiography, a CTV with 3D reconstruction was performed, which provided excellent visualization of the dAVF and clarified its pattern of drainage. The dAVF was supplied by a middle meningeal artery branch that drained into an occipital cortical vein, which then retrograde filled the vein of Labbé. Frameless stereotactic navigation with the imported CTV images was used to plan the craniotomy and to localize the leptomeningeal draining vein and vein of Labbé. The draining vein of the fistula was successfully ligated and divided while preserving flow in the vein of Labbé. Postoperative angiogram demonstrated complete obliteration of the dAVF.
Integration of a 3D reconstructed CTV with conventional angiographic information optimized our surgical understanding of the spatial anatomy of this dAVF and its pattern of venous drainage. Applying the CTV with frameless stereotaxy allowed for safe obliteration of the dAVF while preserving the vein of Labbé.
Surgical Neurology 08/2008; 70(5):521-5; discussion 525. · 1.67 Impact Factor
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ABSTRACT: The authors conducted a cadaveric anatomical study to quantify and compare the area of surgical exposure and the freedom available for instrument manipulation provided by the following four surgical approaches to the extracranial periclival region: simple transoral (STO), transoral with a palate split (TOPS), Le Fort I osteotomy (LFO), and median labioglossomandibulotomy (MLM).
Twelve unembalmed cadaveric heads with normal mouth opening capacity were serially dissected. For each approach, quantitation of extracranial periclival exposure and freedom for instrument manipulation (known here as surgical freedom) was accomplished by stereotactic localization. To quantify the extent of extracranial clival exposure obtained, anatomical measurements of the extracranial clivus were performed on 17 dry skull bases. The values (means +/- standard deviations in mm2) for periclival exposure and surgical freedom, respectively, for the surgical approaches studied were as follows: STO = 492 +/- 229 and 3164 +/- 1900; TOPS = 743 +/- 319 and 3478 +/- 2363; LFO = 689 +/- 248 and 2760 +/- 1922; and MLM 1312 +/- 384 and 8074 +/- 6451. The extent of linear midline clival exposure and the percentage of linear midline clival exposure relative to the total linear midline exposure were as follows, respectively: STO = 0.6 +/- 4.9 mm and 7.8 +/- 11%; TOPS = 8.9 +/- 5.5 mm and 24.2 +/- 16.7%; LFO = 32.9 +/- 10.2 mm and 85.0 +/- 18.7%; and MLM = 2.1 +/- 4.4 mm and 6.7 +/- 11.1%.
The choice of approach and the resulting degree of complexity and associated morbidity depends on the location of the pathological entity. The authors found that the MLM approach, like the STO approach, provided good exposure of the craniocervical junction but limited exposure of the clivus. The TOPS approach, an approach attended by a lesser risk of morbidity, provided adequate exposure of the extracranial inferior clivus. Maximal exposure of the extracranial clivus proper was provided by the LFO approach.
Journal of Neurosurgery 09/2006; 105(2):301-8. · 2.96 Impact Factor
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ABSTRACT: Conventional wisdom regarding skull base surgery says that more extensive bone removal equals greater exposure. Few researchers have quantitatively examined this assertion, however. In this study the authors used a frameless stereotactic system to measure quantitatively the area of petroclival exposure and surgical freedom for manipulation of instruments with successive steps of temporal bone removal.
With the aid of high-power magnification and a high-speed drill, 12 cadaveric specimens were dissected in four predetermined, successive bone removal steps: 1) removal of the Kawase triangle; 2) removal of the Glasscock triangle; 3) removal of the cochlea together with skeletonization of the anterior internal auditory canal; and 4) inferior displacement of the zygoma. Step 1 offered 62 +/- 43 mm2 of exposed petroclival area, with 84 +/- 69 mm2 of surgical freedom; Step 2, 61 +/- 22 and 76 +/- 58 mm2; Step 3, 128 +/- 47 and 109 +/- 87 mm2; and Step 4, 135 +/- 38 and 102 +/- 69 mm2, respectively.
The middle fossa approach provided a means surgically to expose the petroclival area. When examined quantitatively by using a frameless stereotactic device, the authors determined that the removal of the cochlea and skeletonization of the anterior internal auditory canal (Step 3) provided the most significant increase in both exposure and surgical freedom. Removal of the zygoma improved neither exposure nor surgical freedom.
Journal of Neurosurgery 05/2004; 100(4):695-9. · 2.96 Impact Factor
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ABSTRACT: Intracranial endoscopy involves point-to-point navigation: first, in the introduction of the endoscope into a cerebrospinal fluid-containing space and, second, in the identification of a target structure. We report testing and preliminary clinical use of a device for the direct cranial fixation and point-to-point neuronavigation of a rigid ventricular endoscope. An 18-month-old female child presented with rapidly progressive macrocephaly, developmental delay and left hemiparesis. Neuroimaging revealed a large suprasellar cyst and obstructive hydrocephalus. We adapted a ball-stem device with an endoscopic working channel for direct cranial fixation over a burr hole. This device was successfully used in conjunction with MR-based neuronavigation to fenestrate the cyst. Seven months after the operation her developmental delay, macrocephaly and hemiparesis resolved. This device may be particularly effective in cases of small ventricles, ambiguous intra-ventricular landmarks, and in children too young for head-holder immobilization.
Pediatric Neurosurgery 41(5):233-6. · 0.70 Impact Factor
