Does the method of visualization impact the performance of a new surgical task in novice subjects?

INTRODUCTION: Evolution of optical technology from two-dimensional to three-dimensional (3D) systems has come with an associated loss of stereoscopy and 3D depth perception. This report compares performance of surgical tasks in unbiased subjects using these systems. METHODS: Untrained subjects were randomized into two groups, robotically operated video optical telescopic-microscope (ROVOT) or surgical microscope (microscope). Subjects sutured and tied knots. Completion time, NASA-Task Load Index (TLX), and galvanic skin responses were analyzed. RESULTS: Intergroup analysis of suture completion time indicated that microscope use was significantly faster compared to ROVOT, whether used first or second. Regardless of which methodology was used first, the second modality was faster, indicating a transfer effect. NASA-TLX indicated that mental, performance, effort, and frustration were all greater with ROVOT. CONCLUSION: Task completion time and perceived effort were greater with ROVOT. Task completion times improved with repetition regardless of visual modality.

White Matter-Governed Superior Frontal Sulcus Surgical Paradigm: A Radioanatomic Microsurgical Study-Part I.

BACKGROUND: Frontal subcortical and intraventricular pathologies are traditionally accessed via transcortical or interhemispheric-transcallosal corridors. OBJECTIVE: To describe the microsurgical subcortical anatomy of the superior frontal sulcus (SFS) corridor. METHODS: Cadaveric dissections were undertaken and correlated with magnetic resonance imaging/diffusion-tensor imaging-Tractography. Surgical cases demonstrated clinical applicability. RESULTS: SFS was divided into the following divisions: proximal, precentral sulcus to coronal suture; middle, 3-cm anterior to coronal suture; and distal, middle division to the orbital crest. Anatomy was organized as layered circumferential rings projecting radially towards the ventricles: (1) outer ring: at the level of the SFS, the following lengths were measured: (A) precentral sulcus to coronal suture = 2.29 cm, (B) frontal bone projection of superior sagittal sinus (SSS) to SFS = 2.37 cm, (C) superior temporal line to SFS = 3.0 cm, and (D) orbital crest to distal part of SFS = 2.32 cm; and (2) inner ring: (a) medial to SFS, U-fibers, frontal aslant tract (FAT), superior longitudinal fasciculus I (SLF-I), and cingulum bundle, (b) lateral to SFS, U-fibers, (SLF-II), claustrocortical fibers (CCF), and inferior fronto-occipital fasciculus, and (c) intervening fibers, FAT, corona radiata, and CCF. The preferred SFS parafascicular entry point (SFSP-EP) also referred to as the Kassam-Monroy entry point (KM-EP) bisects the distance between the midpupillary line and the SSS and has the following coordinates: x = 2.3 cm (lateral to SSS), y ≥ 3.5 cm (anterior to CS), and z = parallel corona radiata and anterior limb of the internal capsule. CONCLUSION: SFS corridor can be divided into lateral, medial, and intervening white matter tract segments. Based on morphometric assessment, the optimal SFSP-EP is y ≥ 3.5 cm, x = 2.3 cm, and z = parallel to corona radiata and anterior limb of the internal capsule.

White Matter Governed Superior Frontal Sulcus Surgical Paradigm: A Radioanatomic Microsurgical Study-Part II.

BACKGROUND: Kocher's point (KP) and its variations have provided standard access to the frontal horn (FH) for over a century. Anatomic understanding of white matter tracts (WMTs) has evolved, now positioning us to better inform the optimal FH trajectory. OBJECTIVE: To (1) undertake a literature review analyzing entry points (EPs) to the FH; (2) introduce a purpose-built WMT-founded superior frontal sulcus parafascicular (SFSP)-EP also referred to as the Kassam-Monroy entry point (KM-EP); and (3) compare KM-EP with KP and variants with respect to WMTs. METHODS: (1) Literature review (PubMed database, 1892-2018): (a) stratification based on the corridor: i. ventricular catheter; ii. through-channel endoscopic; or iii. portal; (b) substratification based on intent: i. preoperatively planned or ii. intraoperative (postdural opening) for urgent ventricular drainage. (2) Anatomic comparisons of KM-EP, KP, and variants via (a) cadaveric dissections and (b) magnetic resonance-diffusion tensor imaging computational 3D modeling. RESULTS: A total of 31 studies met inclusion criteria: (a) 9 utilized KP coordinate (1 cm anterior to the coronal suture (y-axis) and 3 cm lateral of the midline (x-axis) approximated by the midpupillary line) and 22 EPs represented variations. All 31 traversed critical subcortical WMTs, specifically the frontal aslant tract, superior longitudinal fasciculus II, and inferior fronto-occipital fasciculus, whereas KM-EP (x = 2.3, y = 3.5) spares these WMTs. CONCLUSION: KP (x = 3, y = 1) conceived over a century ago, prior to awareness of WMTs, as well as its variants, anatomically place critical WMTs at risk. The KM-EP (x = 2.3, y = 3.5) is purpose built and founded on WMTs, representing anatomically safe access to the FH. Correlative clinical safety, which will be directly proportional to the size of the corridor, is yet to be established in prospective studies.

Initial Experience with Exoscopic-Based Intraoperative Indocyanine Green Fluorescence Video Angiography in Cerebrovascular Surgery: A Preliminary Case Series Showing Feasibility, Safety, and Next-Generation Handheld Form-Factor.

BACKGROUND: Native vessel patency and residual lesion are primary sources of morbidity in cerebrovascular surgery (CVS) that require real-time visualization to inform surgical judgment, as is available in endovascular procedures. Micro Doppler and microscopy-based indocyanine green (ICG) fluorescence are promising evolutions compared with intraoperative angiography (IA), and digital subtraction angiography (DSA) remains the gold standard. Exoscopic visualization in CVS is emerging; however, the feasibility of exoscopic-based ICG (ICG-E) for CVS has not yet been reported. To objective of the study was to provide initial experience with ICG-E video angiography in CVS. METHODS: Retrospective study in which 2 ICG-E form-factors (exoscopic-coupled or self-contained handheld imager) were used to determine native vessel patency and residual and compared with DSA. RESULTS: Eleven patients (8 aneurysms, 3 arteriovenous malformations [AVMs]) were included. ICG-E was feasible in all, providing real-time information leading to operative decisions affecting surgical judgment. For aneurysms, discordance of IA with ICG-E and DSA was 12%. In 1 patient, IA showed non-flow-restrictive branch stenosis; however, both ICG and DSA showed patency. All AVMs were fully obliterated, with 100% concordance among all modalities. ICG averaged 4.2 mg dose/run (1-4 doses/case); 1.25 mg was the lowest dose allowing visualization with no advantage with escalating dosages. There were no intraoperative/perioperative complications. CONCLUSIONS: In this preliminary study, ICG-E was safe and feasible, providing real-time visualization informing surgical decision making. The last 4 cases (2 aneurysms and 2 AVMs) evolved toward a portable handheld device, a readily accessible real-time modality providing contextual anatomic and flow visualization. Larger studies are needed to assess broader safety, dose escalation, and efficacy.

An Anatomically-Based Endoscopic Endonasal Model to Navigate the Anterior Ventral Skull Base.

BACKGROUND: Endoscopic endonasal approaches to access the sellar and parasellar regions are challenging in the face of anatomical variations or pathologic conditions. We propose an anatomically-based model including the orbitosellar line (OSL), critical oblique foramen line (COFL), and paramedial anterior line (PAL) facilitating safe, superficial-to-deep dissection triangulating upon the medial opticocarotid recess. METHODS: Five cadaveric heads were dissected to systematically expose the OSL, COFL, and PAL, illustrated with image guidance. Application of the coordinate system and a 6-step dissection sequence is described. RESULTS: The coordinate system consists of 1) the OSL, connecting a) the anterior orbital point, junction of the anterior buttress of the middle turbinate with the agger nasi region, located 34.3 ± 0.9 mm above the intersection of the vertical plane of the lacrimal crest, and the orthogonal plane of the maxillo-ethmoidal suture; b) the posterior orbital point, junction of the optic canal with the lamina papyracea, located 4 ± 0.7 mm below the posterior ethmoidal artery; and c) the medial opticocarotid recess; 2) COFL (15 ± 2.8 mm), connecting the palatovaginal canal, vidian canal, and foramen rotundum; and 3) PAL (39 ± 0.06 mm), connecting the vidian canal with the posterior ethmoidal artery. CONCLUSIONS: OSL, COFL, and PAL form an anatomically-based model for the systematic exposure when accessing the parasellar and sellar regions. Preliminary anatomical data suggest that this model may be of value when normal anatomy is distorted by pathology or anatomic variations.