Musculoskeletal demands in microsurgery-an explorative study comparing the ergonomics of microscope and 3D exoscope.

To assess neurosurgeons' physical demands and investigate ergonomic aspects when using microsurgical visualization devices. Six neurosurgeons performed micro-surgical procedures on cadaveric specimens using the prototype of a digital 3D exoscope system (Aeos®, Aesculap, Tuttlingen, Germany) and a standard operating microscope (Pentero 900, Zeiss, Oberkochen, Germany) at two different patient positions (semisitting (SS), supine (SP)). The activities of the bilateral upper trapezius (UTM), anterior deltoid (ADM), and lumbar erector spinae (LEM) muscles were recorded using bipolar surface electromyography and neck flexion, arm abduction, and arm anteversion angles by gravimetrical posture sensors. Perceived discomfort frequency was assessed and subjects compared the two systems in terms of usability, posture, physical and mental demands, and working precision. Using the exoscope led to reduced ADM activity and increased UTM and LEM activity during SS position. The neck was extended when using the exoscope system with lower arm anteversion and abduction angles during the SS position. Subjects reported discomfort at the shoulder-neck area less frequently and lower physical demands when using the Aeos®. However, mental demands were slightly higher and two subjects reported lower working precision. The exoscope system has the potential to reduce the activity of the ADM by changing surgeons arm posture which may be accompanied by less discomfort in the shoulder-neck area. However, dependent on the applied patient position higher muscle activities could occur in the UTM and LEM.

One-on-one mentoring for final year medical students during the neurosurgery rotation.

BACKGROUND: Medical students show varying clinical practical skills when entering their final year clinical clerkship, which is the final period to acquire and improve practical skills prior to their residency. We developed a one-on-one mentoring program to allow individually tailored teaching of clinical practical skills to support final year students with varying skill sets during their neurosurgical clinical clerkship. METHODS: Each participating student (n = 23) was paired with a mentor. At the beginning students were asked about their expectations, teaching preferences and surgical interest. Regular meetings and evaluations of clinical practical skills were scheduled every 2 weeks together with fixed rotations that could be individually adjusted. The one-on-one meetings and evaluations with the mentor gave each student the chance for individually tailored teaching. After completion of the program each student evaluated their experience. RESULTS: The mentoring program was well received by participating students and acquisition or improvement of clinical practical skills was achieved by most students. A varying practical skill level and interest in the field of surgery was seen. CONCLUSIONS: A neurosurgical one-on-one mentoring program is well received by final year medical students and allows for individually tailored learning of clinical practical skills.

Nerve Ultrasonography as an Additive Tool to Clinical Examination and Electrodiagnostics in Sporadic Mononeuritis - Imaging is the Key.

PURPOSE: Sporadic mononeuropathies without trauma or compression are challenging to diagnose. Nerve ultrasound has recently proven its usefulness in the diagnosis of traumatic neuropathies, tumors and polyneuropathies. However, its role in mononeuropathies currently remains unclear. We describe ultrasonography follow-up results in 12 patients with suggested spontaneous, monophasic mononeuritis without signs of generalization. MATERIALS AND METHODS: Nerve conduction studies (NCS), ultrasonography of the affected nerves and the contralateral side, laboratory analysis, and if possible magnetic resonance imaging (MRI) of the affected nerves were established in all patients at onset. In one patient, additive nerve biopsy was performed. In all patients, ultrasonography was repeated after immunotherapy. RESULTS: An infectious pathogen of neuritis was not found in any patient. All but one patient showed predominant axonal nerve damage in NCS, whereas ultrasonography and MRI revealed fascicular and/or overall cross-sectional area (CSA) enlargement or T2 hyperintensity of the affected nerve segments, suggesting an inflammatory background of the neuropathy. Most patients showed significant clinical amelioration of symptoms under treatment (75.0 %) and consequently a decrease in CSA/fascicle enlargement over time (77.8 %). CONCLUSION: Ultrasonography and MRI of the nerves revealed enlargement in patients with mononeuropathy of axonal NCS pattern of unknown origin. Ultrasonography can facilitate the therapeutic decision for immunotherapy. Next to nerve trauma, nerve tumors and nerve entrapments, ultrasonography reliably shows nerve enlargement in the case of inflammation and therefore could further enrich neurophysiology. Nerve imaging might serve as a follow-up tool by observing a decrease in nerve enlargement and improved function.

The midline suboccipital subtonsillar approach to the cerebellomedullary cistern: how I do it.

BACKGROUND: Lesions lateral to the lower brainstem in an area extending from the foraminae of Luschka to the foramen magnum are rare and include different pathologies. There is no consensus on an ideal surgical approach. METHOD: To gain access to this area, we use the midline suboccipital subtonsillar approach (STA). This midline approach with unilateral retraction of the cerebellar tonsil enables entry into the cerebellomedullary cistern. CONCLUSIONS: The STA offers excellent access with a panoramic view of the cerebellomedullary cistern and its structures and therefore can be useful for a number of different pathologies in the lower petroclival area.

Fronto-temporal branch of facial nerve within the interfascial fat pad: is the interfascial dissection really safe?

BACKGROUND: The study was conducted to clarify the presence or absence of fronto-temporal branches (FTB) of the facial nerve within the interfascial (between the superficial and deep leaflet of the temporalis fascia) fat pad. METHODS: Eight formalin-fixed cadaveric heads (16 sides) were used in the study. The course of the facial nerve and the FTB was dissected in its individual tissue planes and followed from the stylomastoid foramen to the frontal region. RESULTS: In the fronto-temporal region, above the zygomatic arch, FTB gives several small twigs running anteriorly in the fat pad above the superficial temporalis fascia and a branch within the temporo-parietal fascia (TPF) to the muscles of the forehead. There were no twigs of the FTB within the interfascial fat pad. CONCLUSIONS: No branches of the FTB are found in the interfascial (between the superficial and deep leaflet of the temporalis fascia) fat pad. The interfascial dissection can be safely performed without risk of injury to the FTB and potential subsequent frontalis palsy.

Actual state of EndActive ventricular endoscopy.

PURPOSE: We assessed usability and applicability of a rigid, multidirectional steerable videoendoscope (EndActive, Karl Storz GmbH, Tuttlingen, Germany) for endoscopic third ventriculostomy and compared our experience with reports about other multidirectional endoscopes. METHODS: The prototype is a 4-mm-diameter rigid videoendoscope with an integrated image sensor comprising an embedded light source, offering a free viewing direction in a range of 160° while the tip itself does not move. In five specimens (ten sides), we introduced the endoscope via precoronal burr holes through the lateral ventricle and foramen of Monro into the third ventricle. The endoscope's tip was positioned at the level of the mamillary bodies and the previously defined anatomical target structures; anteriorly, the optic chiasm, anterior commissure, infundibulum, tuber cinereum and posteriorly, the entrance to the mesencephalic aqueduct and posterior commissure were inspected. RESULTS: A single insertion of the videoendoscope was sufficient to explore with the multiplanar viewing mechanism the entire third ventricle. The prototype videoendoscope may be held like a microsurgical instrument in one hand. It is feasible to control movements precisely due to the reduced weight and ergonomic shape of the device. CONCLUSIONS: The prototype EndActive has the potential to fit in the current concept of ETV and enrich the setting adding working economy and viewing variability.

Developments in neuroendoscopy: trial of a miniature rigid endoscope with a multidirectional steerable tip camera in the anatomical lab.

The aim of this study is to assess field of view, usability and applicability of a rigid, multidirectional steerable video endoscope (EndActive) in various intracranial regions relevant to neurosurgical practice. In four cadaveric specimens, frontolateral, pterional, transnasal (to sella and clivus), interhemispheric (transcallosal and retrocallosal) and retrosigmoid approaches as well as precoronal burr holes for ventriculoscopy were performed. Anatomical target structures were defined in each region. We assessed field of view as well as optical and ergonomic features of the prototype. The EndActive is a 4-mm-diameter rigid video (endo)scope with an integral image sensor comprising an embedded light source. The viewing direction in a range of 160° can either be controlled by the computer keyboard or a four-way joystick mounted to the handle section of the endoscope. The endoscopic imaging system allows the operator to simultaneously see both a 160° wide-angle view of the site and an inset of a specific region of interest. The surgeon can hold the device like a microsurgical instrument in one hand and control movements precisely due to its reduced weight and ergonomic shape. The multiplanar variable-view rigid endoscope proved to be useful for following anatomical structures (cranial nerves I-XII). The device is effective in narrow working spaces where movements jeopardize the delicate surrounding structures. The multiplanar variable viewing mechanism in a compact device offers advantages in terms of safety and ergonomics. Improving the usability will probably optimize the applicability of endoscopic techniques in neurosurgery.

3D Exoscope System in Neurosurgery-Comparison of a Standard Operating Microscope With a New 3D Exoscope in the Cadaver Lab.

BACKGROUND: For decades, the operating microscope has been the "gold standard" visualization device in neurosurgery. The development of endoscopy revolutionized different surgical disciplines, whereas in neurosurgery, the endoscope is commonly used as an additional device more than as single visualization tool. Invention of a 3D exoscope system opens new possibilities in visualization and ergonomics in neurosurgery. OBJECTIVE: To assess the prototype of a 3D exoscope (3D exoscope, year of manufacture 2015, FA Aesculap, Tüttlingen, Germany) as neurosurgical visualization device in comparison to a standard operating microscope. METHODS: A pterional approach was performed in 3 ETOH-fixed specimens (6 sides). A standard operating microscope was compared to a 3D exoscope prototype. Dimensions like visual field, magnification, illumination, ergonomics, depth effect, and 3D impression were compared. RESULTS: In all approaches, the structures of interest could be clearly visualized with both devices. Magnification showed similar results. The exoscope had more magnification potential, whereas the visual quality got worse in higher magnification levels. The illumination showed better results in the microscope. Surgeons felt more comfortable with the 3D exoscope, concerning ergonomic considerations. Depth effect and 3D impression showed similar results. None of the surgeons felt uncomfortable using the exoscope. CONCLUSION: The operating microscope is the gold standard visualization tool in neurosurgery because of its illumination, stereoscopy, and magnification. Nevertheless, it causes ergonomic problems. The prototype of a 3D exoscope showed comparable features in visual field, stereoscopic impression, and magnification, with a clear benefit concerning the ergonomic possibilities.

Interoptic, Trans-lamina Terminalis, Opticocarotid Triangle, and Caroticosylvian Windows From Mini-Supraorbital, Frontomedial, and Pterional Perspectives: A Comparative Cadaver Study With Artificial Lesions.

Introduction: The mini-supraorbital (MSO) and pterional (PT) approaches have been compared in a number of studies focusing on the treatment of aneurysms, craniopharyngiomas, and meningiomas. The goal of this study was to analyze the surgical exposure to different artificial lesions through interoptic (IO), trans-lamina terminalis (TLT), opticocarotid triangle (OCT), and caroticosylvian (CS) windows from the MSO, frontomedial (FM), and PT perspectives. Methods: The MSO, PT, and FM approaches were performed sequentially in two fixed cadaver heads. Three colored spheres were placed around the optic chiasm: (1) between the optic nerves; (2) between the optic nerve and the internal carotid artery; and (3) between the internal carotid artery and the oculomotor nerve. The surgical exposures to these structures by using the IO, TLT, OCT, and CS windows were compared. Results: (1) IO window: from the MSO and PT approaches, the total surgical exposure mainly allows visualization of contralateral lesions. The FM approach was superior for exploration of both sides of the area between the optic nerves. (2) TLT pathway: the MSO and PT approaches mainly expose the contralateral third ventricle wall. (3) OCT window: the PT approach allows exposure of a larger part of the sphere between the optic nerve and the internal carotid artery than the MSO approach. (4) CS window: the PT approach allows a better exposure of lateral structures such as the oculomotor nerve and of the medial prepontine area in comparison to the MSO approach. Conclusion: Simulation of the surgical situation with artificial lesions is a good model for comparing surgical perspectives and for analyzing feasibility of lesion exposure and resection.

Interactive anatomical and surgical live stream lectures improve students' academic performance in applied clinical anatomy.

Tuebingen's Sectio Chirurgica (TSC) is an innovative, interactive, multimedia, and transdisciplinary teaching method designed to complement dissection courses. The Tuebingen's Sectio Chirurgica (TSC) allows clinical anatomy to be taught via interactive live stream surgeries moderated by an anatomist. This method aims to provide an application-oriented approach to teaching anatomy that offers students a deeper learning experience. A cohort study was devised to determine whether students who participated in the TSC were better able to solve clinical application questions than students who did not participate. A total of 365 students participated in the dissection course during the winter term of the 2012/2013 academic year. The final examination contained 40 standard multiple-choice (S-MC) and 20 clinically-applied multiple-choice (CA-MC) items. The CA-MC items referred to clinical cases but could be answered solely using anatomical knowledge. Students who regularly participated in the TSC answered the CA-MC questions significantly better than the control group (75% and 65%, respectively; P < 0.05, Mann-Whitney U test). The groups exhibited no differences on the S-MC questions (85% and 82.5%, respectively; P > 0.05). The CA-MC questions had a slightly higher level of difficulty than the S-MC questions (0.725 and 0.801, respectively; P = 0.083). The discriminatory power of the items was comparable (S-MC median Pearson correlations: 0.321; CA-MC: 0.283). The TSC successfully teaches the clinical application of anatomical knowledge. Students who attended the TSC in addition to the dissection course were able to answer CA-MC questions significantly better than students who did not attend the TSC. Thus, attending the TSC in addition to the dissection course supported students' clinical learning goals. Anat Sci Educ 10: 46-52. © 2016 American Association of Anatomists.

Petrosectomy and Topographical Anatomy in Traditional Kawase and Posterior Intradural Petrous Apicectomy (PIPA) Approach: An Anatomical Study.

OBJECTIVE: To compare the anatomical exposure and petrosectomy extent in the Kawase and posterior intradural petrous apicectomy (PIPA) approaches. METHODS: Kawase and PIPA approaches were performed on 4 fixed cadaveric heads (3 alcohol-fixed, 1 formaldehyde-fixed silicone-injected; 4 Kawase and 4 PIPA approaches). The microsurgical anatomy was examined by means of Zeiss Opmi CS/NC-4 microscopes. HD Karl Storz Endoscopes (AIDA system) were used to display intradural exposure. Petrosectomy volumes was assessed by comparing pre- and postoperative thin-slice computed tomography scans (Analyze 12.0; AnalyzeDirect Mayo Clinic). RESULTS: The Kawase approach exposed the rhomboid fossa with Meckel's cave extradurally, the upper half of the clivus, superior cerebellopontine angle, ventrolateral brainstem, the intrameatal region, basilar apex, and the preganglionic root of cranial nerve (CN) V, CN III-IV-VI intradurally. The PIPA approach exposed the cerebello-pontine angle with CN VI-XII, Meckel's cave, CN III-V, and the middle and lower clivus intradurally from a posterior view. The area of surgical exposure is wide in both approaches; however, the volume of petrosectomy, the working angle, and surgical corridor differ significantly. CONCLUSIONS: The Kawase approach allows wide exposure of the middle cranial fossa (MCF) and posterior cranial fossa, requiring extradural temporal lobe retraction and an extradural petrosectomy with preservation of the internal acoustic meatus and cochlea. No temporal lobe retraction and direct control of neurovascular structures make the PIPA approach a valid alternative for lesions extending mostly in the Posterior cranial fossa with minor extension in the MCF. The longer surgical corridor, cerebellar retraction, and limited exposure of the anterior brainstem make this approach less indicated for lesions with major extension in the MCF and the anterior cavernous sinus.

The midline suboccipital subtonsillar approach to the cerebellomedullary cistern and its structures: anatomical considerations, surgical technique and clinical application.

OBJECTIVE: Lesions of the cerebellomedullary cistern lateral to the lower brainstem in an area extending from the foraminae of Luschka to the foramen magnum are rare and can be caused by various sources. There is no consensus on an ideal surgical approach. We describe the anatomical features and the surgical technique of the midline suboccipital subtonsillar (STA) approach to the cerebellomedullary cistern and its pathologies. METHODS: The study was performed on three alcohol (ETOH)-fixed specimens (6 sides), and the technique of the approach was highlighted. The tonsillar retraction needed to view the important structures was measured. Additionally, the records of 31 patients who underwent the STA procedure were evaluated. We provide three clinical cases as examples. RESULTS: Tonsillar retraction of 0.3cm (SD±0.1cm) exposed the PICA with its telo-velo-tonsillar and cortical branches. Retraction of 0.4cm (SD±0.2cm) exposed the spinal root of CN XI. Retraction of 0.9cm (SD±0.01cm) exposed the hypoglossal canal. Retraction of 1.3cm (SD±0.2cm) exposed the root exit zone of the glossopharyngeal nerve. Retraction of 1.6cm (SD±0.3cm) exposed the jugular foramen (JF), and retraction of 2.4cm (SD±0.2cm) exposed the inner auditory canal (IAC). In all of the selected cases, the pathology could be reached and exposed using the STA. CONCLUSIONS: We recommend STA as a straightforward, easy-to-learn and therefore time-saving and safe procedure compared with other standard approaches to the cerebellomedullary cistern and its pathologies.

Focus on the Lateral Incisural Space: Where is the Trochlear Nerve?

Objective To define the entrance point of the trochlear nerve in the free edge of the tentorium, giving a topographical description in relation to supratentorial and infratentorial reference points. Method The study was performed on seven formaldehyde-fixed specimens (14 sides). The distance from supratentorial and infratentorial reference points to the entrance point of the trochlear nerve into the free tentorial edge was measured. Results The cisternal segment of the trochlear nerve, the tentorial entry point, and the reference points could be clearly identified in all specimens. The assessed distances measured from the tentorial entry point of the trochlear nerve to the anterior clinoid process was 14 to 28 mm, to the posterior clinoid process was 9 to 19 mm, to the posterior lip of the inner auditory canal was 25 to 29 mm, to the posterior border of the Meckel cave was 9 to 14 mm, and to the oculomotor triangle was 5 to 16 mm. Conclusions The cisternal length of the trochlear nerve shows a marked variability and may be further distorted by tumors, whereas the entry point into the tentorium is a stable landmark. Therefore, it might be an important reference point for identifying the nerve before cutting the tentorium.