Kenichi Nishiyama, Tomoru Miwa, Yuto Shirakawa, Hideaki Ono
This transparent model reveals complex mechanical interactions that are crucial for surgical safety but obscured during conventional surgery. By providing a feedback loop for "off-camera" instrument movements, the system serves as an invaluable tool for neurosurgical education, trajectory refinement, and the preclinical evaluation of the next-generation endoscopic instruments.
PURPOSE: Safe intraventricular neuroendoscopy requires refined instrument control within narrow and often distorted working corridors. A significant proportion of surgical complications-such as forniceal injury and vascular compromise-arises from mechanical interactions between the endoscope shaft/sheath and intraventricular structures that remain invisible to the surgeon during the procedure. No existing high-fidelity simulator allows for the real-time, external visualization of these "blind" movements. We developed a novel, high-clarity transparent ventricular model to clarify these interactions and provide a robust platform for surgical training and preclinical device validation.
METHODS: A transparent ventricular model was fabricated using high-clarity urethane and elastomer materials, engineered to approximate the viscoelastic properties and Young's modulus of human cerebral white matter. Critical anatomical landmarks, including the fornix, septal and thalamostriate veins, venous angle, choroid plexus, and mammillary bodies, were delineated using embedded, color-coded PVC films. The model was housed in a water-filled acrylic chamber to match refractive indices and ensure optical clarity. We simulated standard neuroendoscopic procedures-including endoscopic third ventriculostomy (ETV), septostomy, choroid plexus coagulation (CPC), and tumor biopsy-using both rigid and flexible endoscopes via frontal and parietal trajectories. Instrument-tissue interactions were recorded simultaneously via endoscopic and multiple external camera angles.
RESULTS: The model successfully facilitated the continuous, real-time visualization of structural displacements that are inherently invisible in vivo. During ETV simulation, advancement through the foramen of Monro revealed significant compression and lateral displacement of the forniceal columns, even when the endoscopic view suggested a centralized trajectory. Rigid endoscopes demonstrated a larger "mechanical footprint," transmitting higher shear forces to the parenchyma during sweeping maneuvers. Conversely, flexible scopes allowed for more delicate navigation in the temporal and occipital horns, though tip flexion was observed to cause localized displacement of the interthalamic adhesion. Specific "blind" risks, such as the stretching of the thalamostriate veins during sheath withdrawal, were clearly identified.
CONCLUSION: This transparent model reveals complex mechanical interactions that are crucial for surgical safety but obscured during conventional surgery. By providing a feedback loop for "off-camera" instrument movements, the system serves as an invaluable tool for neurosurgical education, trajectory refinement, and the preclinical evaluation of the next-generation endoscopic instruments.